U.S. patent application number 12/458063 was filed with the patent office on 2010-01-14 for hard phase forming alloy powder, wear resistant sintered alloy, and production method for wear resistant sintered alloy.
This patent application is currently assigned to HITACHI POWDERED METALS CO., LTD.. Invention is credited to Hideaki Kawata.
Application Number | 20100008812 12/458063 |
Document ID | / |
Family ID | 41505324 |
Filed Date | 2010-01-14 |
United States Patent
Application |
20100008812 |
Kind Code |
A1 |
Kawata; Hideaki |
January 14, 2010 |
Hard phase forming alloy powder, wear resistant sintered alloy, and
production method for wear resistant sintered alloy
Abstract
A hard phase forming alloy powder, for forming a hard phase
dispersed in a sintered alloy, consists of, by mass %, 15 to 35% of
Mo, 1 to 10% of Si, 10 to 40% of Cr, and the balance of Co and
inevitable impurities. A production method, for a wear resistant
sintered alloy, includes preparing a matrix forming powder, the
hard phase forming alloy powder, and a graphite powder. The
production method further includes mixing 15 to 45% of the hard
phase forming alloy powder and 0.5 to 1.5% of the graphite powder
with the matrix forming powder into a raw powder. The production
method further includes compacting the raw powder into a green
compact having a predetermined shape and includes sintering the
green compact. A wear resistant sintered alloy exhibits a metallic
structure in which 15 to 45% of a hard phase is dispersed in a
matrix. The hard phase consists of, by mass %, 15 to 35% of Mo, 1
to 10% of Si, 10 to 40% of Cr, and the balance of Co and inevitable
impurities.
Inventors: |
Kawata; Hideaki;
(Matsudo-shi, JP) |
Correspondence
Address: |
OLIFF & BERRIDGE, PLC
P.O. BOX 320850
ALEXANDRIA
VA
22320-4850
US
|
Assignee: |
HITACHI POWDERED METALS CO.,
LTD.
MATSUDO-SHI
JP
|
Family ID: |
41505324 |
Appl. No.: |
12/458063 |
Filed: |
June 30, 2009 |
Current U.S.
Class: |
419/11 ; 420/436;
420/583; 420/588; 75/230 |
Current CPC
Class: |
C22C 38/48 20130101;
C22C 38/44 20130101; C22C 33/0285 20130101; B22F 2998/10 20130101;
C22C 38/02 20130101; C22C 38/52 20130101; C22C 38/46 20130101; B22F
3/02 20130101; B22F 2998/10 20130101; B22F 3/10 20130101 |
Class at
Publication: |
419/11 ; 420/436;
420/583; 420/588; 75/230 |
International
Class: |
B22F 3/12 20060101
B22F003/12; C22C 19/07 20060101 C22C019/07; C22C 30/00 20060101
C22C030/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 3, 2008 |
JP |
2008-174624 |
Jul 3, 2008 |
JP |
2008-174629 |
Dec 22, 2008 |
JP |
2008-325074 |
Dec 22, 2008 |
JP |
2008-325075 |
Dec 22, 2008 |
JP |
2008-325076 |
Dec 22, 2008 |
JP |
2008-325077 |
Claims
1. A hard phase forming alloy powder for forming a hard phase
dispersed in a sintered alloy, the hard phase forming alloy powder
consisting of, by mass %, 15 to 35% of Mo, 1 to 10% of Si, 10 to
40% of Cr, and the balance of Co and inevitable impurities.
2. The hard phase forming alloy powder according to claim 1,
wherein the amount of Cr is 20 to 40%.
3. The hard phase forming alloy powder according to claim 1,
wherein not more than 80 mass % of Co is substituted by Fe.
4. The hard phase forming alloy powder according to claim 1,
wherein not more than 5 mass % of Mn is added to the
composition.
5. A production method for a wear resistant sintered alloy,
comprising: preparing a matrix forming powder, the hard phase
forming alloy powder recited in claim 1, and a graphite powder;
mixing 15 to 45% of the hard phase forming alloy powder and 0.5 to
1.5% of the graphite powder with the matrix forming powder into a
raw powder; compacting the raw powder into a green compact having a
predetermined shape; and sintering the green compact.
6. The production method for the wear resistant sintered alloy
according to claim 5, wherein the matrix forming powder is a mixed
powder consisting of 1 to 5 mass % of a nickel powder and the
balance of an iron powder.
7. The production method for the wear resistant sintered alloy
according to claim 6, wherein the iron powder is an ore-reduced
iron powder including 0.3 to 1.5 mass % of metallic oxides.
8. The production method for the wear resistant sintered alloy
according to claim 5, wherein the matrix forming powder is an iron
alloy powder consisting of 1 to 5 mass % of Cr and the balance of
Fe and inevitable impurities.
9. The production method for the wear resistant sintered alloy
according to claim 8, wherein the iron alloy powder further
includes at least one of Mo, V, and Nb at not more than 2.4 mass
%.
10. The production method for the wear resistant sintered alloy
according to claim 5, the matrix forming powder is a mixed powder
consisting of an iron alloy powder and not more than 5 mass % of a
nickel powder with respect to the raw powder, and the iron alloy
powder consists of 1 to 5 mass % of Cr and the balance of Fe and
inevitable impurities.
11. The production method for the wear resistant sintered alloy
according to claim 5, wherein the matrix forming powder is an iron
alloy powder consisting of, by mass %, 3 to 8% of Co, 1 to 2% of
Ni, 1 to 2% of Mo, and the balance of Fe and inevitable
impurities.
12. The production method for the wear resistant sintered alloy
according to claim 5, wherein the matrix forming powder is a mixed
powder consisting of an iron alloy powder and not more than 5 mass
% of a nickel powder with respect to the raw powder, and the iron
alloy powder consists of, by mass %, 3 to 8% of Co, 1 to 2% of Ni,
1 to 2% of Mo, and the balance of Fe and inevitable impurities.
13. The production method for the wear resistant sintered alloy
according to claim 5, wherein the matrix forming powder is an iron
alloy powder consisting of, by mass %, 1 to 3% of Ni, 0.5 to 2% of
Mo, 0.1 to 1% of Cr, 0.1 to 0.5% of Mn, and the balance of Fe and
inevitable impurities.
14. The production method for the wear resistant sintered alloy
according to claim 5, wherein the matrix forming powder is a mixed
powder consisting of an iron alloy powder and not more than 5 mass
% of at least one of a nickel powder and a copper powder with
respect to the raw powder, and the iron alloy powder consists of,
by mass %, 1 to 3% of Ni, 0.5 to 2% of Mo, 0.1 to 1% of Cr, 0.1 to
0.5% of Mn, and the balance of Fe and inevitable impurities.
15. The production method for the wear resistant sintered alloy
according to claim 5, wherein the matrix forming powder is an iron
alloy powder consisting of 1 to 7 mass % of Mo and the balance of
Fe and inevitable impurities.
16. The production method for the wear resistant sintered alloy
according to claim 5, wherein the matrix forming powder is a mixed
powder consisting of an iron alloy powder and not more than 5 mass
% of a nickel powder with respect to the raw powder, and the iron
alloy powder consists of 1 to 7 mass % of Mo and the balance of Fe
and inevitable impurities.
17. The production method for the wear resistant sintered alloy
according to claim 5, wherein the raw powder further includes at
least one kind of powder of machinability improving material at 0.3
to 2 mass %, and the powder of the machinability improving material
is selected from the group consisting of a lead powder, a disulfide
molybdenum powder, a manganese sulfide powder, a boron nitride
powder, a calcium metasilicate mineral powder, and a calcium
fluoride powder.
18. The production method for the wear resistant sintered alloy
according to claim 5, wherein the wear resistant sintered alloy
obtained by sintering has pores, and the production method further
comprising infiltrating or impregnating the pores with one selected
from the group consisting of lead, lead alloy, copper, copper
alloy, and acrylic resin.
19. A wear resistant sintered alloy exhibiting a metallic structure
in which 15 to 45% of a hard phase is dispersed in a matrix, the
hard phase consisting of, by mass %, 15 to 35% of Mo, I to 10% of
Si, 10 to 40% of Cr, and the balance of Co and inevitable
impurities.
20. The wear resistant sintered alloy according to claim 19,
wherein not more than 80 mass % of Co is substituted by Fe in the
composition of the hard phase.
21. The wear resistant sintered alloy according to claim 19,
wherein the hard phase further includes not more than 5 mass % of
Mn.
22. The wear resistant sintered alloy according to claim 19,
wherein the wear resistant sintered alloy has an overall
composition consisting of, by mass %, 1 to 5% of Ni, 2.25 to 33.3%
of Co, 1.5 to 18% of Cr, 2.25 to 15.75% of Mo, 0.15 to 4.5% of Si,
0.5 to 1.5% of C, and the balance of Fe and inevitable impurities,
and the matrix is made of an Fe--Ni--C alloy.
23. The wear resistant sintered alloy according to claim 22,
wherein the matrix of the Fe--Ni--C alloy includes at least one
kind of an oxide of a metal at 0.15 to 1.25 mass % with respect to
the overall composition, and the metal is selected from the group
consisting of aluminum, silicon, magnesium, iron, titanium, and
calcium.
24. The wear resistant sintered alloy according to claim 19,
wherein the wear resistant sintered alloy has an overall
composition consisting of, by mass %, 2.34 to 20.73% of Cr, 2.25 to
15.75% of Mo, 0.15 to 4.5% of Si, 2.25 to 33.3% of Co, 0.5 to 1.5%
of C, and the balance of Fe and inevitable impurities, and the
matrix is made of an Fe--Cr--C alloy.
25. The wear resistant sintered alloy according to claim 24,
wherein the matrix of the Fe--Cr--C alloy further includes at least
one of Mo, V, and Nb at not more than 2 mass % with respect to the
overall composition.
26. The wear resistant sintered alloy according to claim 24,
wherein the matrix of the Fe--Cr--C alloy further includes Ni at
not more than 5 mass % with respect to the overall composition.
27. The wear resistant sintered alloy according to claim 19,
wherein the wear resistant sintered alloy has an overall
composition consisting of, by mass %, 1.5 to 18% of Cr, 0.54 to
1.69% of Ni, 3.09 to 16.84% of Mo, 0.15 to 4.5% of Si, 4.76 to
37.66% of Co, 0.5 to 1.5% of C, and the balance of Fe and
inevitable impurities, and the matrix is made of an Fe--Co--C
alloy.
28. The wear resistant sintered alloy according to claim 27,
wherein the matrix of the Fe--Co--C alloy further includes Ni at
not more than 5 mass % with respect to the overall composition.
29. The wear resistant sintered alloy according to claim 19,
wherein the wear resistant sintered alloy has an overall
composition consisting of, by mass %, 1.58 to 18.55% of Cr, 0.54 to
2.54% of Ni, 2.67 to 16.84% of Mo, 0.15 to 4.5% of Si, 2.25 to
33.30% of Co, 0.05 to 0.42% of Mn, 0.5 to 1.5% of C, and the
balance of Fe and inevitable impurities, and the matrix is made of
an Fe--Ni--Mo--C alloy.
30. The wear resistant sintered alloy according to claim 29,
wherein the matrix of the Fe--Ni--Mo--C alloy further includes at
least one of Ni and Cu at not more than 5.0 mass % with respect to
the overall composition.
31. The wear resistant sintered alloy according to claim 19,
wherein the wear resistant sintered alloy has an overall
composition consisting of, by mass %, 1.5 to 18% of Cr, 3.09 to
19.57% of Mo, 0.15 to 4.5% of Si, 2.25 to 33.3% of Co, 0.5 to 1.5%
of C, and the balance of Fe and inevitable impurities, and the
matrix is made of an Fe--Mo--C alloy.
32. The wear resistant sintered alloy according to claim 31,
wherein the matrix of the Fe--Mo--C alloy further includes Ni at
not more than 5.0 mass % with respect to the overall
composition.
33. The wear resistant sintered alloy according to claim 19,
wherein the sintered alloy has pores and grain boundaries, at least
one kind of powder of machinability improving material is dispersed
in the pores and the grain boundaries at 0.3 to 2 mass %, and the
machinability improving material is selected from the group
consisting of lead, disulfide molybdenum, manganese sulfide, boron
nitride, calcium metasilicate mineral, and calcium fluoride.
34. The wear resistant sintered alloy according to claim 19,
wherein the sintered alloy has pores filled with one kind selected
from the group consisting of lead, lead alloy, copper, copper
alloy, and acrylic resin.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Technical Field
[0002] The present invention relates to a hard phase forming alloy
powder that may preferably be used for forming a hard phase
dispersed in a wear resistant sintered alloy. The wear resistant
sintered alloy, such as that used in valve sheets for
internal-combustion engines, must have wear resistance at high
temperatures. The present invention also relates to a production
method for a wear resistant sintered alloy using the hard phase
forming alloy powder, and the wear resistant sintered alloy may
preferably be used for valve sheets for internal-combustion
engines. In addition, the present invention relates to a wear
resistant sintered alloy obtained by the production method.
[0003] 2. Background Art
[0004] For a sintered alloy, the alloy design can be freely
selected, and various characteristics, such as heat resistance and
wear resistance, can be easily added thereto compared to doing so
for ingot materials. Therefore, the sintered alloy is used for
valve sheets for internal-combustion engines. In such wear
resistant sintered alloy for valve sheets, a hard phase having a
high degree of hardness is generally dispersed in an iron-based
alloy matrix primarily to improve wear resistance. For example, the
following sintered alloys are known. A sintered alloy, in which
ferroalloy particles are dispersed in an iron-based alloy matrix as
a hard phase, is disclosed in Japanese Patent Application of
Laid-Open No. 64-015349. This sintered alloy is formed by adding a
ferroalloy powder, such as ferromolybdenum and ferrotungsten, to a
raw powder and then sintering. Another sintered alloy, in which a
hard phase is dispersed in an iron-based alloy matrix, is disclosed
in Japanese Patent Application of Laid-Open No. 09-195012. This
sintered alloy is formed by adding a high-speed tool steel powder
or a die steel powder to a raw powder and then sintering, and metal
carbides are dispersed in the hard phase. Specifically, when high
wear resistance is required for a sintered alloy, it is preferable
that a Co-based alloy powder or a Ni-based alloy powder (see
Japanese Patent Application of Laid-Open No. 10-046298) be added to
a raw powder and be dispersed as a hard phase. For the Co-based
alloy powder, a Co--Cr--W alloy (see Japanese Patent Application of
Laid-Open No. 64-015349) and a Co--Mo--Si alloy (see Japanese
Patent Application of Laid-Open No. 56-152947) may be used.
SUMMARY OF THE INVENTION
[0005] The cost of a wear resistant sintered alloy, in which
Co--Mo--Si alloy is dispersed as a hard phase, has increased
because the costs of Co and Mo have been rising recently. In view
of recent environmental issues and crude oil depletion issue,
alcohol-based fuels of biological origin (biofuels) are being used
more frequently as fuels for internal-combustion engines. The
alcohol fuels generate acidic materials during combustion, and
therefore, a wear resistant sintered alloy used for valve sheets is
required to have higher corrosion resistance. Accordingly, an
object of the present invention is to provide a hard phase forming
alloy powder at lower cost, and the hard phase forming alloy powder
exhibits wear resistance to the same degree or to a greater degree
than the degree of wear resistance obtained by using a conventional
Co--Mo--Si alloy powder. Moreover, an object of the present
invention is to provide a wear resistant sintered alloy at lower
cost, and the wear resistant sintered alloy has higher corrosion
resistance than the corrosion resistance of a conventional sintered
alloy. Furthermore, an object of the present invention is to
provide a production method for the wear resistant sintered alloy.
In the following description, all of the symbols "%" represent
percentages of mass ratio, that is, "mass %".
[0006] The present invention provides a hard phase forming alloy
powder for forming a hard phase dispersed in a sintered alloy. The
hard phase forming alloy powder consists of, by mass %, 15 to 35%
of Mo, 1 to 10% of Si, 10 to 40% of Cr (preferably, 20 to 40% of
Cr), and the balance of Co and inevitable impurities. In this case,
not more than 80 mass % of Co is preferably substituted by Fe, and
not more than 5 mass % of Mn is preferably added.
[0007] In the hard phase forming alloy powder of the present
invention, Cr, which is relatively low cost, is used as a matrix
strengthening element. Cr is added to a raw powder of a wear
resistant sintered alloy and is sintered, whereby Cr forms a hard
phase dispersed in the sintered alloy. In sintering, Cr in the hard
phase forming alloy powder strengthens the alloy matrix of the hard
phase, and Cr is dispersed from the hard phase forming alloy powder
and strengthens the iron-based alloy matrix of the wear resistant
sintered alloy. In addition, Cr forms a passive oxide film on the
surface of a wear resistant part. Therefore, a wear resistant
sintered alloy using the hard phase forming alloy powder of the
present invention exhibits superior corrosion resistance and wear
resistance.
[0008] The present invention provides a production method for a
wear resistant sintered alloy, and the production method includes
mixing 15 to 45% of the hard phase forming alloy powder and 0.5 to
1.5% of a graphite powder with a matrix forming powder into a raw
powder. The production method further includes compacting the raw
powder into a green compact having a predetermined shape and
includes sintering the green compact.
[0009] In the production method for the wear resistant sintered
alloy, according to a first aspect of the present invention, the
matrix forming powder is preferably made of a mixed powder
consisting of 1 to 5 mass % of a nickel powder and the balance of
an iron powder. As the iron powder, an ore-reduced iron powder
including 0.3 to 1.5 mass % of metal oxides is more preferably
used.
[0010] In the production method for the wear resistant sintered
alloy, according to a second aspect of the present invention, the
matrix forming powder is preferably made of an iron alloy powder
consisting of 1 to 5 mass % of Cr and the balance of Fe and
inevitable impurities. In this case, the iron alloy powder
preferably includes at least one of Mo, V, and Nb at not more than
2.4 mass %. In the second aspect of the present invention, the
matrix forming powder is more preferably made of a mixed powder
consisting of the iron alloy powder and not more than 5 mass % of a
nickel powder with respect to the raw powder.
[0011] In the production method for the wear resistant sintered
alloy, according to a third aspect of the present invention, the
matrix forming powder is preferably made of an iron alloy powder
consisting of, by mass %, 3 to 8% of Co, 1 to 2% of Ni, 1 to 2% of
Mo, and the balance of Fe and inevitable impurities. In the third
aspect of the present invention, the matrix forming powder is more
preferably made of a mixed powder consisting of the iron alloy
powder and not more than 5 mass % of a nickel powder with respect
to the raw powder.
[0012] In the production method for the wear resistant sintered
alloy, according to a fourth aspect of the present invention, the
matrix forming powder is preferably made of an iron alloy powder
consisting of, by mass %, 1 to 3% of Ni, 0.5 to 2% of Mo, 0.1 to 1%
of Cr, 0.1 to 0.5% of Mn, and the balance of Fe and inevitable
impurities. In the fourth aspect of the present invention, the
matrix forming powder is more preferably made of a mixed powder
consisting of the iron alloy powder and not more than 5 mass % of
at least one of a nickel powder and a copper powder with respect to
the raw powder.
[0013] In the production method for the wear resistant sintered
alloy, according to a fifth aspect of the present invention, the
matrix forming powder is preferably made of an iron alloy powder
consisting of 1 to 7 mass % of Mo and the balance of Fe and
inevitable impurities. In the fifth aspect of the present
invention, the matrix forming powder is more preferably made of a
mixed powder consisting of the iron alloy powder and not more than
5 mass % of a nickel powder with respect to the raw powder.
[0014] In the production method for the wear resistant sintered
alloy of the present invention, at least one kind of powder of a
machinability improving material is preferably added to the raw
powder at 0.3 to 2 mass %. The powder of the machinability
improving material is selected from the group consisting of lead
powder, disulfide molybdenum powder, manganese sulfide powder,
boron nitride powder, calcium metasilicate mineral powder, and
calcium fluoride powder. The wear resistant sintered alloy obtained
by sintering has pores, and one selected from the group consisting
of lead, lead alloy, copper, copper alloy, and acrylic resin is
preferably infiltrated or impregnated into the pores.
[0015] The present invention provides a wear resistant sintered
alloy having a metallic structure in which 15 to 45% of a hard
phase is dispersed in the matrix, and the hard phase consists of 15
to 35% of Mo, 1 to 10% of Si, 10 to 40% of Cr, and the balance of
Co and inevitable impurities. In the composition of the hard phase,
not more than 80 mass % of Co is preferably substituted by Fe, and
not more than 5 mass % of Mn is preferably added.
[0016] In the wear resistant sintered alloy, according to a first
aspect of the present invention, the overall composition preferably
consists of, by mass %, 1 to 5% of Ni, 2.25 to 33.3% of Co, 1.5 to
18% of Cr, 2.25 to 15.75% of Mo, 0.15 to 4.5% of Si, 0.5 to 1.5% of
C, and the balance of Fe and inevitable impurities. In this case,
the matrix is preferably made of an Fe--Ni--C alloy. In addition,
at least one kind of an oxide of a metal is more preferably added
in the Fe--Ni--C alloy matrix at 0.15 to 1.25 mass % with respect
to the overall composition. The metal is selected from the group
consisting of aluminum, silicon, magnesium, iron, titanium, and
calcium.
[0017] In the wear resistant sintered alloy, according to a second
aspect of the present invention, the overall composition preferably
consists of, by mass %, 2.34 to 20.73% of Cr, 2.25 to 15.75% of Mo,
0.15 to 4.5% of Si, 2.25 to 33.3% of Co, 0.5 to 1.5% of C, and the
balance of Fe and inevitable impurities. In this case, the matrix
is preferably made of an Fe--Cr--C alloy. In addition, more
preferably, at least one of Mo, V, and Nb is added in the Fe--Cr--C
alloy matrix at not more than 2 mass % with respect to the overall
composition. Moreover, Ni is more preferably added in the Fe--Cr--C
alloy matrix at not more than 5 mass % with respect to the overall
composition.
[0018] In the wear resistant sintered alloy, according to a third
aspect of the present invention, the overall composition preferably
consists of, by mass %, 1.5 to 18% of Cr, 0.54 to 1.69% of Ni, 3.09
to 16.84% of Mo, 0.15 to 4.5% of Si, 4.76 to 37.66% of Co, 0.5 to
1.5% of C, and the balance of Fe and inevitable impurities. In this
case, the matrix is preferably made of an Fe--Co--C alloy. In
addition, Ni is more preferably added in the Fe--Co--C alloy matrix
at not more than 5 mass % with respect to the overall
composition.
[0019] In the wear resistant sintered alloy, according to a fourth
aspect of the present invention, the overall composition preferably
consists of, by mass %, 1.58 to 18.55% of Cr, 0.54 to 2.54% of Ni,
2.67 to 16.84% of Mo, 0.15 to 4.5% of Si, 2.25 to 33.30% of Co,
0.05 to 0.42% of Mn, 0.5 to 1.5% of C, and the balance of Fe and
inevitable impurities. In this case, the matrix is preferably made
of an Fe--Ni--Mo--C alloy. In addition, at least one of Ni and Cu
is more preferably added in the Fe--Ni--Mo--C alloy matrix at not
more than 5.0 mass % with respect to the overall composition.
[0020] In the wear resistant sintered alloy, according to a fifth
aspect of the present invention, the overall composition preferably
consists of, by mass %, 1.5 to 18% of Cr, 3.09 to 19.57% of Mo,
0.15 to 4.5% of Si, 2.25 to 33.3% of Co, 0.5 to 1.5% of C, and the
balance of Fe and inevitable impurities. In this case, the matrix
is preferably made of an Fe--Mo--C alloy. In addition, Ni is more
preferably added in the Fe--Mo--C alloy matrix at not more than 5.0
mass % with respect to the overall composition.
[0021] In the wear resistant sintered alloy of the present
invention, the sintered alloy has pores and grain boundaries, and
0.3 to 2 mass % of at least one kind of powder of machinability
improving material is preferably dispersed in the pores and the
grain boundaries. The machinability improving material is selected
from the group consisting of lead, disulfide molybdenum, manganese
sulfide, boron nitride, calcium metasilicate mineral, and calcium
fluoride. In addition, one selected from the group consisting of
lead, lead alloy, copper, copper alloy, and acrylic resin is
preferably infiltrated or impregnated in the pores of the sintered
alloy.
[0022] In the hard phase forming alloy powder of the present
invention, Cr, which is relatively low cost, is used as a matrix
strengthening element. Cr is added to the raw powder of a wear
resistant sintered alloy and is sintered, whereby Cr forms a hard
phase dispersed in the sintered alloy. In sintering, Cr in the hard
phase forming alloy powder strengthens the alloy matrix of the hard
phase, and Cr is dispersed from the hard phase forming alloy powder
and strengthens the iron based alloy matrix of the wear resistant
sintered alloy. In addition, Cr forms a passive oxide film on the
surface of a wear resistant part. Therefore, the wear resistant
sintered alloy using the hard phase forming alloy powder of the
present invention exhibits superior corrosion resistance and wear
resistance. Accordingly, the wear resistant sintered alloy of the
present invention is preferably used for valve sheets of
internal-combustion engines using an alcohol fuel as a fuel.
PREFERRED EMBODIMENTS OF THE INVENTION
1. Hard Phase Forming Alloy Powder
[0023] Similar to a conventional Co--Mo--Si alloy powder, the hard
phase forming alloy powder of the present invention is added to a
raw powder and is sintered, whereby the hard phase forming alloy
powder is dispersed in the matrix as a hard phase. The essential
feature of the present invention is that a great amount of Cr is
added to the conventional Co--Mo--Si alloy powder so as to improve
the conventional Co--Mo--Si alloy powder.
[0024] Co is included in the hard phase forming alloy powder of the
present invention and is solid-solved in the alloy matrix of the
hard phase formed by the hard phase forming alloy powder. As a
result, Co improves heat resistance of the hard phase and also
improves strength and wear resistance at high temperatures. Co
included in the hard phase forming alloy powder is dispersed in the
matrix of a sintered alloy in sintering, whereby the matrix of the
sintered alloy is strengthened by solid solution strengthening, and
the hard phase is strongly combined to the matrix of the sintered
alloy. In addition, a partial amount of Co combines with Mo, Cr,
and Si and forms molybdenum silicides, chromium silicides, and
complex silicides thereof. The silicides function as a core of a
hard phase and prevent plastic flow and adhesion of the matrix of
the sintered alloy, whereby wear resistance is improved.
[0025] Mo is included in the hard phase forming alloy powder of the
present invention and is dispersed in the matrix of a sintered
alloy in sintering. As a result, the matrix of the sintered alloy
is strengthened by solid solution strengthening, and quenchability
of the matrix of the sintered alloy is improved, whereby strength
and wear resistance of the sintered alloy are improved. Mo combines
mainly with Si and forms hard molybdenum silicides, and a partial
amount of Mo reacts with Cr and Co and forms complex silicides. The
silicides function as a core of the hard phase. Therefore, plastic
flow and adhesion of the matrix of the sintered alloy are
prevented, whereby wear resistance is improved. In this case, when
the amount of Mo in the hard phase forming alloy powder is less
than 15%, the matrix is not sufficiently strengthened. Moreover,
silicides are not sufficiently precipitated, and the above pinning
effect is not sufficiently obtained, whereby wear resistance is
decreased. On the other hand, when more than 35% of Mo is included
in the hard phase forming alloy powder, the hard phase forming
alloy powder is hardened, whereby compressibility of the raw powder
is decreased. Moreover, since the amount of silicides is increased,
a mating part may be easily worn. Therefore, the amount of Mo in
the hard phase forming alloy powder is set to be 15 to 35%.
[0026] Si combines with Mo, Co, and Cr and forms hard molybdenum
silicides, chromium silicides, and complex silicides thereof,
thereby improving wear resistance. When the amount of Si in the
hard phase forming alloy powder is less than 1%, silicides are not
sufficiently precipitated. When the amount of Si in the hard phase
forming alloy powder is greater than 10%, the hard phase forming
alloy powder is hardened, whereby compressibility and sinterability
is decreased. Therefore, the amount of Si in the hard phase forming
alloy powder is set to be 1 to 10%.
[0027] Cr is solid-solved in the alloy matrix of the hard phase
that is formed after sintering, whereby the alloy matrix of the
hard phase is strengthened. Moreover, Cr is dispersed in the matrix
of a sintered alloy in sintering and strengthens the matrix of the
sintered alloy. Cr dispersed in the sintered alloy forms a passive
oxide film on the surface of a wear resistant part and improves
corrosion resistance and oxidation resistance. A partial amount of
Cr combines with Si, Mo, and Co and forms hard chromium silicides
and complex silicides. Cr is low in cost compared to the costs of
Co and Mo, and Cr is added to decrease the amount of Co, whereby
the hard phase forming alloy powder is inexpensive, and a wear
resistant sintered alloy can be produced at lower cost. When Cr
having the above effects in the hard phase forming alloy powder is
less than 10%, the above effects are not sufficiently obtained. In
order to efficiently obtain the above effects, the amount of Cr is
preferably set to be 20% or more. On the other hand, when the
amount of Cr in the hard phase forming alloy powder is greater than
40%, oxide films are strongly formed on the surfaces of the hard
phase forming alloy powder particles, whereby sintering may be
prevented. Moreover, since the hard phase forming alloy powder is
hardened by the oxide films, compressibility of the raw powder is
decreased, and strength and wear resistance of the sintered alloy
are decreased. Therefore, the amount of Cr in the hard phase
forming alloy powder is set to be 10 to 40%, preferably, 20 to
40%.
[0028] In the present invention, by setting the amount of Cr in the
hard phase forming alloy powder for forming a hard phase as
described above, corrosion resistance and oxidation resistance are
improved. Therefore, a partial amount of Co for forming the alloy
matrix of the hard phase can be substituted by Fe. That is, since
Cr solid-solved in Fe forms a passive oxide film and thereby
improves corrosion resistance and oxidation resistance, Fe, which
is inexpensive, can be substituted part of the amount of Co that
has superior corrosion resistance but is expensive. In this case,
not more than 80% of Co in the hard phase forming alloy powder can
be substituted by Fe.
[0029] In the present invention, by adding Mn in the hard phase
forming alloy powder, Mn is solid-solved in the alloy matrix of the
hard phase formed after sintering, and the alloy matrix of the hard
phase is strengthened. By strengthening the alloy matrix of the
hard phase in this manner, flow and drop off of silicides
(molybdenum silicides, chromium silicides, and complex silicides
thereof) precipitated in the hard phase are prevented, whereby
superior wear resistance is obtained under severe conditions. Mn is
dispersed in Fe matrix of the sintered alloy and increases
fixability of the hard phase, whereby drop off of the hard phase is
prevented, and wear resistance is improved. When the amount of such
Mn in the hard phase forming alloy powder is greater than 5%, Mn
oxide films are formed on the surface layers of the hard phase
forming alloy powder particles, whereby dispersion during sintering
is prevented, and the fixability of the hard phase is decreased.
Therefore, the upper limit of the amount of Mn in the hard phase
forming alloy powder is set to be 5%.
[0030] For the matrix of the wear resistant sintered alloy, in
which the hard phase made from the hard phase forming alloy powder
of the present invention is dispersed, a conventional wear
resistant sintered alloy matrix may be used, and specifically, a
low-alloy steel or a stainless steel may be used. That is, in a raw
powder of a sintered alloy to which a conventional Co--Mo--Si based
hard phase forming alloy powder is added, instead of using the
conventional Co--Mo--Si based hard phase forming alloy powder, the
hard phase forming alloy powder of the present invention can be
used. When such a raw powder is compacted and is sintered, a
sintered alloy is obtained. This sintered alloy has corrosion
resistance, oxidation resistance, and wear resistance to the same
degree or to degrees greater than those of a wear resistant
sintered alloy in which a hard phase made from a conventional
Co--Mo--Si based hard phase forming alloy powder is dispersed. In
addition, since the amount of Co that is expensive is decreased,
the sintered alloy can be produced at lower cost.
2. Production Method for Wear Resistant Sintered Alloy and Wear
Resistant Sintered Alloy
2-1. Basic Formation
[0031] In the present invention, Cr is dispersed in the matrix and
forms a passive oxide film by using the above hard phase, and
corrosion resistance of the matrix is improved. Therefore, the
matrix can be made of an iron alloy, which is relatively
inexpensive, without using large amounts of Co and Mo, which are
expensive. Specifically, a wear resistant sintered alloy is
obtained by the following method. The above hard phase forming
alloy powder and a graphite powder are mixed with an iron based
matrix forming powder into a raw powder. Then, the raw powder is
compacted into a green compact having a predetermined shape, and
the green compact is sintered.
[0032] When the hard phase forming alloy powder is added to the raw
powder at less than 15%, wear resistance is not sufficiently
obtained. The hard phase forming alloy powder of the present
invention is made by increasing the amount of Cr in a conventional
Co--Mo--Si based hard phase forming alloy powder. Since Cr is
solid-solved in the Co-alloy matrix, the hardness of the hard phase
forming alloy powder is increased, and compressibility thereof is
decreased. Therefore, when the hard phase forming alloy powder is
added to the raw powder at more than 45%, the compressibility of
the raw powder is greatly decreased. Accordingly, the hard phase
forming alloy powder is added to the raw powder at 15 to 45%.
[0033] The hard phase dispersed in the matrix of the wear resistant
sintered alloy is formed by adding the hard phase forming alloy
powder and a graphite powder to the iron based matrix forming
powder and by sintering. Since the hard phase forming alloy powder
is added to the raw powder at 15 to 45%, the amount of the hard
phase dispersed in the matrix of the wear resistant sintered alloy
is 15 to 45%. As described above, the hard phase forming alloy
powder consists of 15 to 35% of Mo, 1 to 10% of Si, 10 to 40% of
Cr, and the balance of Co and inevitable impurities. Therefore, in
the overall composition of the wear resistant sintered alloy, the
amount of Co is 2.25 to 33.3%, the amount of Cr is 1.5 to 18%, the
amount of Mo is 2.25 to 15.75%, and the amount of Si is 0.15 to
4.5%. When Mn is added to the hard phase forming alloy powder, the
amount of Mn in the overall composition is not more than 2.25%.
[0034] A graphite powder is added as a source of C. C is dispersed
in the iron based matrix forming powder in sintering and is
solid-solved in the Fe matrix, whereby the Fe matrix is
strengthened. Moreover, C is added in order to form a matrix
structure made of martensite or bainite, which have high strength.
When the amount of C is less than 0.5%, the above effects are not
sufficiently obtained. On the other hand, when the amount of C is
greater than 1.5%, brittle cementite may be precipitated at grain
boundaries, whereby strength and wear resistance of the wear
resistant sintered alloy are decreased. Therefore, the amount of C
in the overall composition is set to be 0.5 to 1.5%. If such C is
added and is solid-solved in the iron powder, the hardness of the
iron powder is increased, and the compressibility is greatly
decreased. Therefore, the entire amount of C is added in the form
of a graphite powder. Accordingly, a graphite powder is added to
the matrix forming powder at 0.5 to 1.5%.
[0035] In the production method for the wear resistant sintered
alloy of the present invention, the raw powder is compacted into a
green compact having a predetermined shape, and the green compact
is sintered. The compacting and the sintering may be performed in
the same manner as those for a conventional wear resistant sintered
alloy using a Co--Mo--Si alloy powder as a hard phase forming alloy
powder. That is, the compacting may be performed at a compacting
pressure of 600 to 1000 MPa, and the sintering may be performed at
a sintering temperature of 1000 to 1300.degree. C.
[0036] A sintered alloy obtained by the above production method
exhibits a metallic structure in which 15 to 45% of a hard phase is
dispersed in a matrix, and the hard phase consists of 15 to 35% of
Mo, 1 to 10% of Si, 10 to 40% of Cr, and the balance of Co and
inevitable impurities.
[0037] In the wear resistant sintered alloy of the present
invention, a machinability improving technique that is
conventionally performed may be used. That is, at least one kind of
machinability improving material may be added to the raw powder at
0.3 to 2% so as to disperse the machinability improving material in
the pores and grain boundaries of the wear resistant sintered
alloy. The machinability improving material is selected from the
group consisting of lead powder, disulfide molybdenum powder,
manganese sulfide powder, boron nitride powder, calcium
metasilicate mineral powder, and calcium fluoride powder. These
materials are machinability improving components, and the materials
function as a starting point for breaking during machining when the
materials are dispersed in the matrix, whereby the machinability of
the sintered alloy is improved. When the amount of the
machinability improving components is less than 0.3%, the effects
are not sufficiently obtained. On the other hand, when the amount
of the machinability improving components is greater than 2%, the
strength of the sintered alloy is decreased.
[0038] One selected from the group consisting of lead, lead alloy,
copper, copper alloy, and acrylic resin may be infiltrated or
impregnated in the pores of the wear resistant sintered alloy of
the present invention. When a sintered alloy having pores is
machined, the machining is intermittently performed, and impact is
intermittently applied to an edge of a tool. However, by adding
lead, copper, and the like in the pores, the machining may be
continuously performed, and the degree of impact at an edge of a
tool is decreased. Lead and lead alloy function as a solid
lubricant. Copper and copper alloy have high thermal conductivity,
thereby preventing thermal accumulation and decreasing thermal
damages at the edge. Acrylic resin functions as a starting point
for breaking in machining.
2-2. Fe--Ni--C Alloy Matrix
[0039] In the above wear resistant sintered alloy, according to the
first preferred embodiment of the present invention, the matrix of
the wear resistant sintered alloy is made of an Fe--Ni--C alloy.
The Fe--Ni--C alloy does not include Co and Mo, which are
expensive, whereby a wear resistant sintered alloy may be formed at
lower cost.
[0040] Ni is solid-solved in the Fe matrix and thereby strengthens
the Fe matrix, and Ni is added in order to easily obtain martensite
at a cooling rate after sintering. Ni having such effects is
dispersed in. Fe at relatively high rate during sintering.
Moreover, if Ni is added in the form of an Fe--Ni alloy powder in
which Ni is solid-solved in Fe, the main raw powder is hardened.
Therefore, Ni is added by adding a nickel powder to the iron
powder. In this case, when the nickel powder is added to the iron
powder at less than 1%, the above effects are not sufficiently
obtained. On the other hand, when the nickel powder is added to the
iron powder at more than 5%, a large amount of Ni-rich austenite
having low wear resistance is formed and remains. Therefore, the
nickel powder is added to the iron powder at 1 to 5%.
[0041] C is solid-solved in the Fe matrix and thereby strengthens
the Fe matrix, and C is added in order to form a matrix structure
made of martensite or bainite, which have high strength. When the
amount of C is less than 0.5%, the above effects are not
sufficiently obtained. On the other hand, when the amount of C is
greater than 1.5%, brittle cementite may be precipitated at grain
boundaries, whereby strength and wear resistance of the wear
resistant sintered alloy are decreased. Therefore, the amount of C
in the overall composition is set to be 0.5 to 1.5%. If such C is
added and is solid-solved in the iron powder, the hardness of the
iron powder is increased, and the compressibility is greatly
decreased. Accordingly, the entire amount of C is added in the form
of a graphite powder.
[0042] As described above, according to the first embodiment of the
present invention, the production method for the wear resistant
sintered alloy includes preparing an iron powder, a nickel powder,
a hard phase forming alloy powder, and a graphite powder. The hard
phase forming alloy powder consists of, by mass %, 15 to 35% of Mo,
1 to 10% of Si, 10 to 40% of Cr, and the balance of Co and
inevitable impurities. The production method further includes
mixing 1 to 5% of the nickel powder, 15 to 45% of the hard phase
forming alloy powder, and 0.5 to 1.5% of the graphite powder with
the iron powder into a raw powder. The production method further
includes compacting the raw powder into a green compact having a
predetermined shape and includes sintering the green compact.
[0043] As described above, according to the first embodiment of the
present invention, the wear resistant sintered alloy consists of,
by mass %, 1 to 5% of Ni, 2.25 to 33.3% of Co, 1.5 to 18% of Cr,
2.25 to 15.75% of Mo, 0.15 to 4.5% of Si, 0.5 to 1.5% of C, and the
balance of Fe and inevitable impurities. The wear resistant
sintered alloy exhibits a metallic structure in which 15 to 45% of
a hard phase is dispersed in an Fe--Ni--C alloy matrix, and the
hard phase consists of 15 to 35% of Mo, 1 to 10% of Si, 10 to 40%
of Cr, and the balance of Co and inevitable impurities.
[0044] The matrix of the wear resistant sintered alloy of the
present invention is made of an Fe--Ni--C alloy by adding a nickel
powder and a graphite powder to the iron powder, as described
above. In this case, as the iron powder of the main raw material,
an ore-reduced iron powder is preferably used. The ore-reduced iron
powder includes a very small amount of metallic oxides, such as
aluminum, silicon, magnesium, iron, titanium, and calcium, due to
the production method thereof. These metallic oxides are dispersed
in the matrix as fine metallic oxide phases, and these metallic
oxides function as free-machining components and improve
machinability. In contrast, an atomized iron powder and a mill
scale-reduced iron powder, which are generally used, do not include
sufficient amount of metallic oxides, and the above effect for
improving machinability is not obtained therefrom. In order to
obtain the effect for improving the machinability, at least one
kind of metallic oxides is required at 0.3% or more, and the
metallic oxide is selected from the group consisting of aluminum,
silicon, magnesium, iron, titanium, and calcium. On the other hand,
when the amount of the metallic oxides in the ore-reduced iron
powder is greater than 1.5%, the matrix is embrittled, and the
compressibility of the iron powder is decreased. Therefore, the
amount of the metallic oxides in the ore-reduced iron powder is set
to be 0.3 to 1.5%. This amount of the metallic oxides corresponds
to 0.15 to 1.25% with respect to the overall composition.
2-3. Fe--Cr--C Alloy Matrix
[0045] In the above wear resistant sintered alloy, according to the
second preferred embodiment of the present invention, the matrix of
the wear resistant sintered alloy is made of an Fe--Cr--C alloy.
The Fe--Cr--C alloy does not include Co and Mo, which are
expensive, whereby a wear resistant sintered alloy may be formed at
lower cost. By preliminarily adding Cr to the matrix, corrosion
resistance of the matrix is further improved. Since Cr is dispersed
from the above hard phase to the matrix, the amount of Cr in the
Fe--Cr--C alloy matrix can be small compared to the amount of Cr in
the hard phase.
[0046] Cr included in the matrix forms a passive oxide film and
thereby improves the corrosion resistance of the matrix, and Cr is
solid-solved in the Fe matrix and strengthens the Fe matrix.
Moreover, Cr included in the matrix improves the quenchability of
the matrix and forms a matrix structure made of a bainite structure
having high strength and high toughness at a cooling rate after
sintering. In order to uniformly add such effects of Cr to the
entirety of the matrix, Cr is alloyed with Fe and is added in the
form of the iron alloy powder. In this case, when the amount of Cr
in the iron alloy powder is less than 1%, the above effects are not
sufficiently obtained. On the other hand, when the amount of Cr in
the iron alloy powder is greater than 5%, the hardness of the iron
alloy powder is increased, and the compressibility of the raw
powder is decreased. Therefore, the amount of Cr in the iron alloy
powder is set to be 1 to 5%.
[0047] C is solid-solved in the Fe matrix and thereby strengthens
the Fe matrix, and C is added in order to form a matrix structure
made of martensite or bainite having high strength. When the amount
of C is less than 0.5%, the above effects are not sufficiently
obtained. On the other hand, when the amount of C is greater than
1.5%, C combines with Cr and precipitates Cr carbides in the
matrix. Cr was added to form a passive oxide film and to improve
the corrosion resistance of the matrix. As a result, the
concentration of Cr in the matrix is decreased, and the corrosion
resistance of the matrix is decreased. Therefore, the amount of C
in the overall composition is set to be 0.5 to 1.5%. If such C is
added and is solid-solved in the above iron alloy powder, the
hardness of the iron alloy powder is increased, and the
compressibility of the raw powder is greatly decreased.
Accordingly, the entire amount of C is added in the form of a
graphite powder.
[0048] As described above, according to the second embodiment of
the present invention, the production method for the wear resistant
sintered alloy includes preparing an iron alloy powder, a hard
phase forming alloy powder, and a graphite powder. The iron alloy
powder consists of, by mass %, 1 to 5% of Cr and the balance of Fe
and inevitable impurities. The hard phase forming alloy powder
consists of, by mass %, 15 to 35% of Mo, 1 to 10% of Si, 10 to 40%
of Cr, and the balance of Co and inevitable impurities. The
production method further includes mixing 15 to 45% of the hard
phase forming alloy powder and 0.5 to 1.5% of the graphite powder
with the iron alloy powder into a raw powder. The production method
further includes compacting the raw powder into a green compact
having a predetermined shape and includes sintering the green
compact.
[0049] As described above, according to the second embodiment of
the present invention, the wear resistant sintered alloy consists
of, by mass %, 2.34 to 20.73% of Cr, 2.25 to 15.75% of Mo, 0.15 to
4.5% of Si, 2.25 to 33.3% of Co, 0.5 to 1.5% of C, and the balance
of Fe and inevitable impurities. The wear resistant sintered alloy
exhibits a metallic structure in which 15 to 45% of a hard phase is
dispersed in an Fe--Cr--C alloy matrix, and the hard phase consists
of 15 to 35% of Mo, 1 to 10% of Si, 10 to 40% of Cr, and the
balance of Co and inevitable impurities.
[0050] Mo, V, and Nb have higher carbide-forming ability than that
of Cr. Therefore, in the wear resistant sintered alloy having the
above Fe--Cr--C alloy matrix of the present invention, by adding at
least one of Mo, V, and Nb to the Fe--Cr--C alloy matrix, Mo, V,
and Nb selectively combine with the above C and form fine metallic
carbides dispersed in the matrix. Accordingly, corrosion resistance
is not decreased by the precipitation of Cr carbides. In addition,
mechanical strength and wear resistance of the matrix can be
improved. In order to uniformly add these effects to the entirety
of the matrix, at least one of Mo, V, and Nb is preferably added
and is solid-solved in the iron alloy powder. In this case, when
more than 2.4% of Mo, V, and Nb are added to the iron alloy powder,
the hardness of the iron alloy powder is increased, and the
compressibility of the raw powder is decreased. Therefore, the
total amount of Mo, V, and Nb added to the iron alloy powder is set
to be not more than 2.4%. This total amount of Mo, V, and Nb
corresponds to not more than 2 mass % with respect to the overall
composition.
[0051] Ni is solid-solved in the Fe matrix and thereby strengthens
the Fe matrix, and Ni improves the quenchability of the matrix.
Therefore, in a case of improving wear resistance and mechanical
strength by forming a matrix structure made of a martensite
structure or a mixed structure of a martensite structure and a
bainite structure, instead of forming a matrix structure made of a
bainite structure, Ni is added. Ni having such effects is dispersed
into Fe at relatively high rate in sintering. Moreover, if Ni is
added and is solid-solved in the above iron alloy powder, the iron
alloy powder is hardened, and the compressibility of the main raw
powder is decreased. Therefore, Ni is added by adding a nickel
powder to the iron alloy powder. In this case, when the nickel
powder is added to the raw powder at more than 5%, a large amount
of Ni-rich austenite having low wear resistance is formed and
remains in the matrix. Therefore, the upper limit of the amount of
the nickel powder added to the raw powder is set to be 5%.
2-4. Fe--Co--C Alloy Matrix
[0052] In the above wear resistant sintered alloy, according to the
third embodiment of the present invention, the matrix of the wear
resistant sintered alloy is made of an Fe--Co--C alloy. The
Fe--Co--C alloy includes Co and Mo, but the amounts of Co and Mo
are small, whereby a wear resistant sintered alloy can be formed at
lower cost than the cost of a conventional wear resistant sintered
alloy.
[0053] Co is solid-solved in the Fe matrix and thereby strengthens
the Fe matrix, and Co increases the heat resistance of the matrix
and improves the wear resistance at high temperatures. In order to
uniformly add such effects of Co to the entirety of the matrix, Co
is alloyed with Fe and is added in the form of an iron alloy
powder. In this case, when the amount of Co in the iron alloy
powder is less than 3%, the above effects are not sufficiently
obtained. On the other hand, when the amount of Co in the iron
alloy powder is greater than 8%, the hardness of the iron alloy
powder is increased, the compressibility of the raw powder is
decreased, and the cost of the iron alloy powder is high.
Therefore, the amount of Co in the iron alloy powder is set to be 3
to 8%.
[0054] Mo is solid-solved in the Fe matrix and thereby strengthens
the Fe matrix, and Mo increases the quenchability of the matrix and
improves the strength and wear resistance of the matrix. In order
to uniformly add such effects of Mo to the entirety of the matrix,
Mo is added by solid solving Mo in the above iron alloy powder. In
this case, when the amount of Mo in the iron alloy powder is less
than 1%, the above effects are not sufficiently obtained. On the
other hand, when the amount of Mo in the iron alloy powder is
greater than 2%, the above improving effects are not efficiently
obtained, and the hardness of the iron alloy powder is increased,
thereby decreasing the compressibility of the raw powder.
Therefore, the amount of Mo in the iron alloy powder is set to be 1
to 2%.
[0055] Ni is solid-solved in the Fe matrix and thereby strengthens
the Fe matrix, and Ni increases the quenchability of the matrix and
improves the strength and wear resistance of the matrix. In order
to uniformly add such effects of Ni to the entirety of the matrix,
Ni is added by solid solving Ni in the above iron alloy powder. In
this case, when the amount of Ni in the iron alloy powder is less
than 1%, the above effects are not sufficiently obtained. On the
other hand, when the amount of Ni in the iron alloy powder is
greater than 2%, the hardness of the iron alloy powder is
increased, and the compressibility of the raw powder is decreased.
Therefore, the amount of Ni in the iron alloy powder is set to be 1
to 2%.
[0056] C is solid-solved in the Fe matrix and strengthens the Fe
matrix, and C is added in order to form a matrix structure made of
martensite or bainite having high strength. When the amount of C is
less than 0.5%, the above effects are not sufficiently obtained. On
the other hand, when the amount of C is greater than 1.5%, C
combines with Cr and precipitates Cr carbides in the matrix. Cr was
added for forming a passive oxide film and improving corrosion
resistance of the matrix. As a result, the concentration of Cr in
the matrix is decreased, and the corrosion resistance of the matrix
is decreased. Therefore, the amount of C in the overall composition
is set to be 0.5 to 1.5%. If such C is added and is solid-solved in
the above iron alloy powder, the hardness of the iron alloy powder
is increased, and the compressibility of the raw powder is greatly
decreased. Accordingly, the entire amount of C is added in the form
of a graphite powder.
[0057] As described above, according to the third embodiment of the
present invention, the production method of the wear resistant
sintered alloy includes preparing an iron alloy powder, a hard
phase forming alloy powder, and a graphite powder. The iron alloy
powder consists of, by mass %, 3 to 8% of Co, 1 to 2% of Ni, 1 to
2% of Mo, and the balance of Fe and inevitable impurities. The hard
phase forming alloy powder consists of, by mass %, 15 to 35% of Mo,
1 to 10% of Si, 10 to 40% of Cr, and the balance of Co and
inevitable impurities. The production method further includes
mixing 15 to 45% of the hard phase forming alloy powder and 0.5 to
1.5% of the graphite powder with the iron alloy powder into a raw
powder. The production method further includes compacting the raw
powder into a green compact having a predetermined shape and
includes sintering the green compact.
[0058] As described above, according to the third embodiment of the
present invention, the wear resistant sintered alloy consists of,
by mass %, 1.5 to 18% of Cr, 0.54 to 1.69% of Ni, 3.09 to 16.84% of
Mo, 0.15 to 4.5% of Si, 4.76 to 37.66% of Co, 0.5 to 1.5% of C, and
the balance of Fe and inevitable impurities. The wear resistant
sintered alloy exhibits a metallic structure in which 15 to 45% of
a hard phase is dispersed in an Fe--Co--C alloy matrix, and the
hard phase consists of 15 to 35% of Mo, 1 to 10% of Si, 10 to 40%
of Cr, and the balance of Co and inevitable impurities.
[0059] In the wear resistant sintered alloy according to the third
embodiment of the present invention, if a greater amount of the
above effects of Ni is required, Ni may be added to the raw powder
in the form of a nickel powder. Since Ni is dispersed into Fe at
relatively high rate in sintering, Ni is preferably added by
alloying. Nevertheless, when a larger amount of Ni is added, Ni may
be added in the form of a nickel powder, because the effects of Ni
are easily added to the entirety of the matrix compared to the
cases of other elements. In this case, when the nickel powder is
added to the raw powder at greater than 5%, a large amount of
Ni-rich austenite having low wear resistance is formed and remains
in the matrix. Therefore, the upper limit of the amount of the
nickel powder added to the raw powder is set to be 5%.
2-5. Fe--Ni--Mo--C Alloy Matrix
[0060] In the wear resistant sintered alloy, according to the
fourth preferred embodiment of the present invention, the matrix of
the wear resistant sintered alloy is made of an Fe--Ni--Mo--C
alloy. The Fe--Ni--Mo--C alloy includes Mo, but the amount of Mo is
small, and the Fe--Ni--Mo--C alloy does not include Co. Therefore,
a wear resistant sintered alloy can be formed at lower cost than
the cost of a conventional wear resistant sintered alloy.
[0061] In view of wear resistance, wearing characteristics with
respect to a mating material, and strength of a wear resistant
sintered alloy, the metallic structure of the matrix is made so as
to be bainite. In order to form a matrix structure made of bainite,
addition of alloying elements such as Mo, Ni, and Cr is effective.
In order to uniformly add this effect to the entirety of the matrix
structure, these alloying components are alloyed with Fe and are
added in the form of an iron alloy powder. Specifically, the
composition of the iron alloy powder is selected so as to consist
of, by mass %, 1 to 3% of Ni, 0.5 to 2% of Mo, 0.1 to 1% of Cr, 0.1
to 0.5% of Mn, and the balance of Fe and inevitable impurities.
That is, when the amount of Ni is less than 1%, the amount of Mo is
less than 0.5%, the amount of Cr is less than 0.1%, and the amount
of Mn is less than 0.1%, the matrix is not sufficiently bainitized.
On the other hand, when the amount of Ni is greater than 3%, the
amount of Mo is greater than 2%, the amount of Cr is greater than
1%, and the amount of Mn is greater than 0.5%, the hardness of the
alloy powder is increased, and the compressibility is decreased,
whereby strength and wear resistance are decreased.
[0062] C is solid-solved in the Fe matrix and thereby strengthens
the Fe matrix, and C is added in order to form a matrix structure
made of martensite or bainite having high strength. When the amount
of C is less than 0.5%, the above effects are not sufficiently
obtained. On the other hand, when the amount of C is greater than
1.5%, C combines with Cr and precipitates Cr carbides in the
matrix. Cr was added for forming a passive oxide film and improving
corrosion resistance of the matrix. As a result, the concentration
of Cr in the matrix is decreased, and the corrosion resistance of
the matrix is decreased. Therefore, the amount of C in the overall
composition is set to be 0.5 to 1.5%. If such C is added and is
solid-solved in the above iron alloy powder, the hardness of the
iron alloy powder is increased, and the compressibility of the raw
powder is greatly decreased. Accordingly, the entire amount of C is
added in the form of a graphite powder.
[0063] As described above, according to the fourth embodiment of
the present invention, the production method of the wear resistant
sintered alloy includes preparing an iron alloy powder, a hard
phase forming alloy powder, and a graphite powder. The iron alloy
powder consists of, by mass %, 1 to 3% of Ni, 0.5 to 2% of Mo, 0.1
to 1% of Cr, 0.1 to 0.5% of Mn, and the balance of Fe and
inevitable impurities. The hard phase forming alloy powder consists
of, by mass %, 15 to 35% of Mo, 1 to 10% of Si, 10 to 40% of Cr,
and the balance of Co and inevitable impurities. The production
method further includes mixing 15 to 45% of the hard phase forming
alloy powder and 0.5 to 1.5% of the graphite powder with the iron
alloy powder into a raw powder. The production method further
includes compacting the raw powder into a green compact having a
predetermined shape and includes sintering the green compact.
[0064] As described above, according to the fourth embodiment of
the present invention, the wear resistant sintered alloy consists
of, by mass %, 1.58 to 18.55% of Cr, 0.54 to 2.54% of Ni, 2.67 to
16.84% of Mo, 0.15 to 4.5% of Si, 2.25 to 33.30% of Co, 0.05 to
0.42% of Mn, 0.5 to 1.5% of C, and the balance of Fe and inevitable
impurities. The wear resistant sintered alloy exhibits a metallic
structure in which 15 to 45% of a hard phase is dispersed in an
Fe--Ni--Mo--C alloy matrix, and the hard phase consists of 15 to
35% of Mo, 1 to 10% of Si, 10 to 40% of Cr, and the balance of Co
and inevitable impurities.
[0065] In the wear resistant sintered alloy according to the fourth
embodiment of the present invention, when further improvement of
the wear resistance is required, a nickel powder or a copper powder
may be added to the raw powder so as to form a matrix structure
which partially includes martensite with high strength and is made
of a mixed structure of bainite and martensite. Ni and Cu have
great effects for improving the quenchability, and a nickel powder
and a copper powder have low hardness. Therefore, by adding a
nickel powder or a copper powder to the above iron alloy powder, a
mixed structure of bainite and martensite is easily formed as a
matrix structure. In this case, when the amount of the nickel
powder added to the iron alloy powder is greater than 5%, a large
amount of Ni-rich austenite having low wear resistance is formed
and remains in the matrix. In addition, when the amount of the
copper powder added to the iron alloy powder is greater than 5%, a
soft copper phase is precipitated in the matrix, whereby the
strength of the matrix is decreased. Therefore, the upper limit of
the amount of the nickel powder added to the iron alloy powder is
set to be 5%, and the upper limit of the copper powder added to the
iron alloy powder is set to be 5%.
2-6. Fe--Mo--C Alloy Matrix
[0066] In the wear resistant sintered alloy, according to the fifth
preferred embodiment of the present invention, the matrix of the
wear resistant sintered alloy is made of an Fe--Mo--C alloy. The
Fe--Mo--C alloy includes Mo, but the amount of Mo is small, and the
Fe--Ni--Mo--C alloy does not include Co. Therefore, a wear
resistant sintered alloy can be formed at lower cost than the cost
of a conventional wear resistant sintered alloy.
[0067] Mo is solid-solved in the Fe matrix and thereby strengthens
the Fe matrix, and Mo extends the bainite area of an alloy, whereby
Mo forms a matrix structure made of a bainite structure having high
strength and high toughness at a cooling rate after sintering. In
order to uniformly add such effects of Mo in the entirety of the
matrix, Mo is alloyed with Fe and is added in the form of an iron
alloy powder. In this case, when the amount of Mo in the iron alloy
powder is less than 1%, the above effects are not sufficiently
obtained. On the other hand, when the amount of Mo in the iron
alloy powder is greater than 7%, the hardness of the iron alloy
powder is increased, and the compressibility of the raw powder is
decreased. Therefore, the amount of Mo in the iron alloy powder is
set to be 1 to 7%.
[0068] C is solid-solved in the Fe matrix and thereby strengthens
the Fe matrix, and C is added in order to form a matrix structure
made of martensite or bainite having high strength. When the amount
of C is less than 0.5%, the above effects are not sufficiently
obtained. On the other hand, when the amount of C is greater than
1.5%, brittle cementite may be precipitated at grain boundaries,
whereby strength and wear resistance of the wear resistant sintered
alloy are decreased. Therefore, the amount of C in the overall
composition is set to be 0.5 to 1.5%. If such C is added and is
solid-solved in the iron powder, the hardness of the iron powder is
increased, and the compressibility is greatly decreased.
Accordingly, the entire amount of C is added in the form of a
graphite powder.
[0069] As described above, according to the fifth embodiment of the
present invention, the production method for the wear resistant
sintered alloy includes preparing an iron alloy powder, a hard
phase forming alloy powder, and a graphite powder. The iron alloy
powder consists of, by mass %, 1 to 7% of Mo and the balance of Fe
and inevitable impurities. The hard phase forming alloy powder
consists of, by mass %, 15 to 35% of Mo, 1 to 10% of Si, 10 to 40%
of Cr, and the balance of Co and inevitable impurities. The
production method further includes mixing 15 to 45% of the hard
phase forming alloy powder and 0.5 to 1.5% of the graphite powder
with the iron alloy powder into a raw powder. The production method
further includes compacting the raw powder into a green compact
having a predetermined shape and includes sintering the green
compact.
[0070] As described above, according to the fifth embodiment of the
present invention, the wear resistant sintered alloy consists of,
by mass %, 1.5 to 18% of Cr, 3.09 to 19.57% of Mo, 0.15 to 4.5% of
Si, 2.25 to 33.3% of Co, 0.5 to 1.5% of C, and the balance of Fe
and inevitable impurities. The wear resistant sintered alloy
exhibits a metallic structure in which 15 to 45% of a hard phase is
dispersed in an Fe--Mo--C alloy matrix, and the hard phase consists
of 15 to 35% of Mo, 1 to 10% of Si, 10 to 40% of Cr, and the
balance of Co and inevitable impurities.
[0071] When Ni is solid-solved in an Fe matrix, Ni strengthens the
Fe matrix and improves the quenchability of the matrix. In the wear
resistant sintered alloy according to the fifth embodiment of the
present invention, in a case of improving wear resistance and
mechanical strength by forming a matrix structure made of a
martensite structure or a mixed structure of a martensite structure
and a bainite structure, instead of forming a matrix structure made
of a bainite structure, Ni is added. Ni having such effects is
dispersed into Fe at relatively high rate in sintering. In
addition, if Ni is added and is solid-solved in the above iron
alloy powder, the iron alloy powder is hardened, and the
compressibility of the main raw powder is decreased. Therefore, Ni
is added by adding a nickel powder to the iron alloy powder. In
this case, when the nickel powder is added to the raw powder at
more than 5%, a large amount of Ni-rich austenite having low wear
resistance is formed and remains in the matrix. Therefore, the
upper limit of the amount of the nickel powder added to the raw
powder is set to be 5%.
Examples
Example A
Hard Phase Forming Alloy Powder
Example A-1
[0072] An iron powder, a copper powder, a graphite powder, and a
hard phase forming alloy powder having a composition shown in Table
A-1 were prepared. The iron powder, 1.5% of the copper powder, 35%
of the hard phase forming alloy powder, and 1% of the graphite
powder were added and mixed with a forming lubricant (0.8% of zinc
stearate), and a raw powder was obtained. The obtained raw powder
was compacted at a compacting pressure of 650 MPa so as to be
formed in a ring shape with an outer diameter of 30 mm, an inner
diameter of 20 mm, and a height of 10 mm. Next, these green
compacts were sintered at 1160.degree. C. for 60 minutes in a
decomposed ammonia gas atmosphere, and samples Nos. A01 to A07 were
formed. Simple wear tests and corrosion tests were performed on
these samples. The results of these tests are shown in Table
A-1.
[0073] The simple wear tests were performed with the input of
colliding and sliding under high temperature. Specifically, the
above-described ring-shaped samples (sintered alloys) were formed
in a valve sheet in which the inner edge part has a tapered surface
of 45.degree.. The valve sheets were pressed into and were fitted
into a housing made of an aluminum alloy. Then, discoid mating
materials (valves) in which the outer edge partially has a tapered
surface of 45.degree. were made from SUH-36. The mating material
was moved up and down by rotation of an eccentric cam driven by a
motor so that the tapered surface of the sintered alloy and the
mating material collided repeatedly. That is, the movement of the
valve is a piston movement up and down, and the valve repeats an
action of leaving from the valve sheet by rotation of the eccentric
cam driven by the motor and an action of colliding with the valve
sheet by a valve spring. In these tests, the mating materials were
heated with a burner so that the sintered alloys reached
350.degree. C. The colliding frequency was 2800 times per minute,
and the repeating time was 10 hours. After these tests were
performed, the wear amounts of the valve sheets and wear amounts of
the valves were measured and evaluated. In corrosion tests,
ring-shaped samples were immersed in a 10% nitric acid solution for
one hour, and weight changes were measured before and after the
immersing. The weight changes were divided by the surface area, and
these calculated values were evaluated as a corrosion loss
(mg/cm.sup.2).
TABLE-US-00001 TABLE A-1 Compositions of hard phase Wear amount
forming alloy powder Substitutional .mu.m Corrosion Sample mass %
ratio Valve loss No. Co Fe Cr Mo Si of Fe sheet Valve Total
mg/cm.sup.2 Notes A01 Balance -- 8.0 28.0 2.5 -- 45 3 48 0.35
Conventional example A02 Balance 26.0 5.0 20.0 3.0 36 115 3 118
0.51 Comparative example A03 Balance 24.0 10.0 20.0 3.0 36 80 3 83
0.38 Comparative example A04 Balance 20.6 20.0 20.0 3.0 36 42 3 45
0.15 Practical example A05 Balance 17.0 30.0 20.0 3.0 36 35 3 38
0.13 Practical example A06 Balance 13.4 40.0 20.0 3.0 36 45 5 50
0.16 Practical example A07 Balance 9.7 50.0 20.0 3.0 36 99 21 120
0.21 Comparative example
[0074] In the sample No. A01 in Table A-1, a conventional hard
phase forming alloy powder was used. In the samples Nos. A02 to
A07, the amount of Mo in a conventional hard phase forming alloy
powder was decreased, 36% of Co was substituted by Fe, and the
amount of Cr was changed in the range of 5 to 50%. According to
these samples, the influence of the amount of Cr in the hard phase
forming alloy powder was investigated.
[0075] In the sample No. A02 in which the amount of Cr in the hard
phase forming alloy powder was 5%, the wear amount of the valve
sheet was large because Fe was included in the hard phase forming
alloy powder and the amount of Cr was insufficient. Moreover, the
corrosion loss was large because Fe was included in the hard phase
forming alloy powder. In the sample No. A03 in which the amount of
Cr in the hard phase forming alloy powder was 10%, the amount of Cr
was increased, whereby the wear amount of the valve sheet and the
corrosion loss were decreased, but these values were large. On the
other hand, in the samples Nos. A04 to A06 in which the amount of
Cr in the hard phase forming alloy powder was 20 to 40%, the wear
amount was equal to or less than that of the sample No. A01
(conventional example) because the matrix was strengthened by Cr.
Moreover, the corrosion loss was not more than half that of the
sample No. A01 (conventional example) because corrosion resistance
was improved by Cr. In the sample No. A06 in which the amount of Cr
in the hard phase forming alloy powder was 40%, as described above,
although wear resistance and corrosion resistance were good, the
wear amount and the corrosion loss were slightly increased,
compared with the sample No. A05 in which the amount of Cr in the
hard phase forming alloy powder was 30%. This is because, in the
sample No. A06, the oxide films on the surfaces of the hard phase
forming alloy powder particles were hardened by the increase in the
amount of Cr, whereby hardness of the hard phase forming alloy
powder was increased, and compressibility of the raw powder was
decreased. As a result, the density of the green compact was
decreased, and the density of the sintered compact was decreased.
In the sample No. A07 in which the amount of Cr in the hard phase
forming alloy powder was greater than 40%, the influence of the
decrease in the density of the sintered compact was remarkable, and
the strength of the sintered compact was decreased. That is, the
wear amount of the valve sheet was remarkably increased, and the
wear amount of the valve was also remarkably increased because wear
particles of the valve sheet eroded the valve. Moreover, pitting
corrosion was easily caused, whereby the corrosion loss was
increased. According to the above results, when the amount of Cr in
the hard phase forming alloy powder was 20 to 40%, the obtained
sintered alloys had not less than approximately equal wear
resistance and superior corrosion resistance, compared with a case
of using the conventional hard phase forming alloy powder.
Example A-2
[0076] The iron powder, the copper powder, the graphite powder used
in the example A-1, and a hard phase forming alloy powder having a
composition shown in Table A-2 were added and mixed in the same
ratio as in the example A-1, and a raw powder was obtained. The
obtained raw powder was compacted and sintered in the same way as
in the example A-1, and samples Nos. A08 to A13 were formed. The
wear tests were performed in the same way as in the example A-1 for
these samples. The results and the values of the samples Nos. A01
and A05 are shown in Table A-2.
TABLE-US-00002 TABLE A-2 Compositions of hard phase forming Wear
amount alloy powder Substitutional .mu.m Sample mass % ratio Valve
No. Co Fe Cr Mo Si of Fe sheet Valve Total Notes A01 Balance --
8.00 28.00 2.50 -- 45 3 48 Conventional example A08 Balance --
30.00 20.00 3.00 -- 25 3 28 Practical example A09 Balance 7.00
30.00 20.00 3.00 15 30 3 33 Practical example A05 Balance 17.00
30.00 20.00 3.00 36 35 3 38 Practical example A10 Balance 28.20
30.00 20.00 3.00 60 37 3 40 Practical example A11 Balance 37.60
30.00 20.00 3.00 80 45 4 49 Comparative example A12 Balance 42.30
30.00 20.00 3.00 90 78 5 83 Comparative example A13 -- 47.00 30.00
20.00 3.00 100 171 10 181 Practical example
[0077] According to Table A-2, when Co in the hard phase forming
alloy powder was substituted by Fe, the influence of the
substitutional ratio of Fe was investigated. The substitutional
ratio is a percentage of the amount of Fe in the hard phase forming
alloy powder to the sum total of the amount of Co and Fe in the
hard phase forming alloy powder. In the sample No. A08, Co in the
hard phase forming alloy powder was not substituted by Fe, and the
wear amount was the least among the above examples A and wear
resistance was good. When Co in the hard phase forming alloy powder
was substituted by Fe and the substitutional ratio of Fe was
increased, the wear amount was increased. In this case, when the
substitutional ratio of Fe was not more than 80%, the wear amount
was approximately equal to or less than that of the sample No. A01
(conventional example). However, when the substitutional ratio of
Fe was more than 80%, the effect of Co was insufficient and the
wear amount was increased remarkably. According to the above
results, although Co in the hard phase forming alloy powder could
be substituted by Fe, the substitutional ratio of Fe should be not
more than 80%.
Example A-3
[0078] The iron powder, the copper powder, the graphite powder used
in the example A-1, and a hard phase forming alloy powder having a
composition shown in Table A-3 were added and mixed in the same
ratio as in the example A-1, and a raw powder was obtained. The
obtained raw powder was compacted and sintered in the same way as
in the example A-1, and samples Nos. A14 to A17 were formed. The
wear tests were performed in the same way as in the example A-1 for
these samples. The results and the values of the samples Nos. A01
and A05 are shown in Table A-3.
TABLE-US-00003 TABLE A-3 Compositions of hard phase forming Wear
amount alloy powder Substitutional .mu.m Sample mass % ratio Valve
No. Co Fe Cr Mo Si of Fe sheet Valve Total Notes A01 Balance --
8.00 28.00 2.50 0.0 45 3 48 Conventional example A05 Balance 17.00
30.00 20.00 3.00 36.2 35 3 38 Practical example A14 Balance 17.00
30.00 20.00 3.00 36.2 32 3 35 Practical example A15 Balance 17.00
30.00 20.00 3.00 36.2 27 4 31 Practical example A16 Balance 17.00
30.00 20.00 3.00 36.2 35 12 47 Practical example A17 Balance 17.00
30.00 20.00 3.00 36.2 68 46 114 Comparative example
[0079] According to Table A-3, the effect of Mn in the hard phase
forming alloy powder was investigated. In the samples Nos. A14 to
A16 in which the amount of Mn in the hard phase forming alloy
powder was not more than 5%, the alloy matrixes of hard phases were
strengthened by Mn, whereby the wear amounts of the valve sheets
were approximately equal to or less than that of the sample No. A05
in which Mn was not added in the hard phase forming alloy powder.
On the other hand, the wear amounts of the valves were slightly
increased according to the increase in the amount of Mn because
hard phases were strengthened. In the sample No. A17 in which the
amount of Mn in the hard phase forming alloy powder was greater
than 5%, the wear amount of the valve sheet was remarkably
increased. This is because the hard phase forming alloy powder was
hardened by the increase in the amount of Mn, whereby
compressibility of the raw powder was remarkably decreased. As a
result, the density of the green compact was decreased, and the
density of the sintered compact was decreased, whereby the strength
of the sintered compact was decreased. Moreover, the wear amount of
the valve was also remarkably increased because the wear particles
of the valve sheet eroded the valve. According to the above
results, although wear resistance of the sintered alloy could be
further improved by adding Mn in the hard phase forming alloy
powder, the amount of Mn in the hard phase forming alloy powder
should be not more than 5%.
Example B
Fe--Ni--C Alloy Matrix
Example B-1
[0080] An ore-reduced iron powder consisting of 1% of metal oxides
and the balance of Fe and inevitable impurities, a nickel powder, a
hard phase forming alloy powder having a composition shown in Table
B-1, and a graphite powder were prepared. These powders were added
and mixed with a forming lubricant (0.8% of zinc stearate) in the
mixing ratio shown in Table B-1, and a raw powder was obtained. The
obtained raw powder was compacted and sintered in the same way as
in the example A-1, and samples Nos. B01 to B06 were formed. The
simple wear tests and the corrosion tests were performed in the
same way as in the example A-1 for these samples. In the simple
wear tests, the mating materials were heated with a burner so that
the sintered alloys reached 300.degree. C. The results of these
tests are also shown in Table B-1.
TABLE-US-00004 TABLE B-1 Mixing ratio mass % Evaluation item Hard
phase forming alloy powder Wear amount .mu.m Corrosion Sample Iron
Nickel Compositions mass % Graphite Valve loss No. powder powder Co
Fe Cr Mo Si powder sheet Valve Total mg/cm.sup.2 Notes B01 Balance
2.00 35.00 Balance 42.00 5.00 20.00 3.00 1.00 98 3 101 0.32
Comparative example B02 Balance 2.00 35.00 Balance 37.00 10.00
20.00 3.00 1.00 61 3 64 0.17 Practical example B03 Balance 2.00
35.00 Balance 27.00 20.00 20.00 3.00 1.00 41 3 44 0.15 Practical
example B04 Balance 2.00 35.00 Balance 17.00 30.00 20.00 3.00 1.00
30 3 33 0.13 Practical example B05 Balance 2.00 35.00 Balance 7.00
40.00 20.00 3.00 1.00 47 5 52 0.16 Practical example B06 Balance
2.00 35.00 Balance 2.00 45.00 20.00 3.00 1.00 85 21 106 0.20
Comparative example
[0081] According to Table B-1, the influence of the amount of Cr in
the hard phase forming alloy powder (the amount of Cr in the hard
phase) was investigated. In the sample No. B01, the amount of Cr in
the hard phase forming alloy powder was insufficient, whereby the
matrix of the sintered alloy was not sufficiently strengthened, and
the wear amount of the valve sheet was large. In addition, since
the amount of Cr was insufficient, the corrosion resistance was
insufficient, and the corrosion loss was also large. In the sample
No. B02 in which the amount of Cr in the hard phase forming alloy
powder was 10%, the wear amount of the valve sheet was remarkably
decreased because the matrix was strengthened by Cr, and the
corrosion loss was reduced because corrosion resistance was
improved by Cr. When the amount of Cr in the hard phase forming
alloy powder was not more than 30%, the wear amounts of the valve
sheets and the corrosion losses were decreased according to the
increase in the amount of Cr. On the other hand, in the sample No.
B05 in which the amount of Cr in the hard phase forming alloy
powder was 40%, the wear amount of the valve sheet and the
corrosion loss were increased. This is because the amount of Cr in
the hard phase forming alloy powder was increased, whereby the
hardness of the hard phase forming alloy powder was increased. As a
result, compressibility of the raw powder was decreased, and the
density of the green compact was decreased, whereby the density of
the sintered compact was decreased. In the sample No. B06 in which
the amount of Cr in the hard phase forming alloy powder was greater
than 40%, the wear amount of the valve sheet was increased and the
corrosion loss was remarkably increased, because the influence of
the decrease of compressibility was remarkable. Moreover, the wear
amount of the valve was also remarkably increased because the wear
particles of the valve sheet eroded the valve. According to the
above results, when the amount of Cr in the hard phase forming
alloy powder was 10 to 40%, the wear amounts of the valve sheet and
valve were small and the corrosion loss of the sintered alloy was
small.
Example B-2
[0082] The ore-reduced iron powder used in the example B-1, a
nickel powder, a graphite powder, and the hard phase forming alloy
powder used in the sample No. B04 in the example B-1 were prepared.
The ratio of the hard phase forming alloy powder was changed as
shown in Table B-2, these powders were added and mixed with a
forming lubricant (0.8% of zinc stearate), and a raw powder was
obtained. The obtained raw powder was compacted and sintered in the
same way as in the example A-1, and samples Nos. B07 to B11 were
formed. The wear tests and the corrosion tests were performed in
the same way as in the example B-1 for these samples. The results
are shown in Table B-2 with the values of the sample No. B04 in the
example B-1.
TABLE-US-00005 TABLE B-2 Mixing ratio mass % Evaluation item Hard
phase forming alloy powder Wear amount .mu.m Corrosion Sample Iron
Nickel Compositions mass % Graphite Valve loss No. powder powder Co
Fe Cr Mo Si powder sheet Valve Total mg/cm.sup.2 Notes B07 Balance
2.00 5.00 Balance 17.00 30.00 20.00 3.00 1.00 120 0 120 0.56
Comparative example B08 Balance 2.00 15.00 Balance 17.00 30.00
20.00 3.00 1.00 58 2 60 0.28 Practical example B09 Balance 2.00
25.00 Balance 17.00 30.00 20.00 3.00 1.00 35 3 38 0.18 Practical
example B04 Balance 2.00 35.00 Balance 17.00 30.00 20.00 3.00 1.00
30 3 33 0.13 Practical example B10 Balance 2.00 45.00 Balance 17.00
30.00 20.00 3.00 1.00 49 6 55 0.15 Practical example B11 Balance
2.00 55.00 Balance 17.00 30.00 20.00 3.00 1.00 90 35 125 0.26
Comparative example
[0083] According to Table B-2, the influence of the amount of the
hard phase forming alloy powder (the amount of the hard phase
dispersed in the matrix) was investigated. In the sample No. B07 in
which the amount of the hard phase forming alloy powder was less
than 15%, the wear amount of the valve sheet was large because the
amount of the hard phase was insufficient and the plastic flow of
the matrix could not be prevented. Moreover, the corrosion loss was
large because the hard phase was insufficient and Cr was not
sufficiently dispersed from the hard phase to the matrix. In the
sample No. B08 in which the amount of the hard phase forming alloy
powder was 15%, wear resistance and corrosion resistance of the
matrix of the sintered alloy were improved by the hard phase,
whereby the wear amount of the valve sheet was remarkably decreased
and the corrosion loss was decreased. When the amount of the hard
phase forming alloy powder was not more than 35%, the wear amount
of the valve sheet and the corrosion loss were decreased according
to the increase in the amount of the hard phase forming alloy
powder. On the other hand, in the sample No. B10 in which the
amount of the hard phase forming alloy powder was 45%, the wear
amount of the valve sheet and the corrosion loss were slightly
increased because compressibility of the raw powder was decreased
by the increase in the amount of the hard phase forming alloy
powder. In the sample No. B11 in which the amount of the hard phase
forming alloy powder was greater than 45%, the influence of the
decrease of compressibility was remarkable, whereby the wear amount
of the valve sheet was remarkably increased, and the corrosion loss
was increased. Moreover, the wear amount of the valve also was
remarkably increased because the wear particles of the valve sheet
eroded the valve. According to the above results, when the amount
of the hard phase forming alloy powder (the amount of the hard
phase dispersed in the matrix) was 15 to 45%, the wear amounts of
the valve sheet and the valve were small.
Example B-3
[0084] The ore-reduced iron powder used in the example B-1, a
nickel powder, a graphite powder, and the hard phase forming alloy
powder used in the sample No. B04 in the example B-1 were prepared.
The ratio of the nickel powder was changed as shown in Table B-3,
these powders were added and mixed with a forming lubricant (0.8%
of zinc stearate), and a raw powder was obtained. The obtained raw
powder was compacted and sintered in the same way as in the example
A-1, and samples Nos. B12 to B17 were formed. The wear tests were
performed in the same way as in the example B-1 for these samples.
The results are shown in Table B-3 with the values of the sample
No. B04 in the example B-1.
TABLE-US-00006 TABLE B-3 Mixing ratio mass % Evaluation item Hard
phase forming alloy powder Wear amount .mu.m Sample Iron Nickel
Compositions mass % Graphite Valve No. powder powder Co Fe Cr Mo Si
powder sheet Valve Total Notes B12 Balance -- 35.00 Balance 17.00
30.00 20.00 3.00 1.00 102 2 104 Comparative example B13 Balance
1.00 35.00 Balance 17.00 30.00 20.00 3.00 1.00 51 3 54 Practical
example B04 Balance 2.00 35.00 Balance 17.00 30.00 20.00 3.00 1.00
30 3 33 Practical example B14 Balance 3.00 35.00 Balance 17.00
30.00 20.00 3.00 1.00 26 3 29 Practical example B15 Balance 4.00
35.00 Balance 17.00 30.00 20.00 3.00 1.00 33 3 36 Practical example
B16 Balance 5.00 35.00 Balance 17.00 30.00 20.00 3.00 1.00 56 4 60
Practical example B17 Balance 6.00 35.00 Balance 17.00 30.00 20.00
3.00 1.00 94 5 99 Comparative example
[0085] According to Table B-3, the influence of the amount of the
nickel powder (the amount of Ni in the overall composition) was
investigated. In the sample No. B12 in which the nickel powder was
not added, the wear amount of the valve sheet was large because the
Fe matrix of the sintered alloy was not strengthened. In the sample
No. B13 in which the amount of the nickel powder was 1%, the wear
amount of the valve sheet was remarkably decreased because the Fe
matrix was strengthened by Ni. When the amount of the nickel powder
was not more than 3%, the wear amount of the valve sheet was
decreased according to the increase in the amount of the nickel
powder. On the other hand, in the samples Nos. B15 and B16 in which
the amount of the nickel powder was 4 to 5%, the wear amounts of
the valve sheet were slightly increased because the amount of soft
residual austenite phase was increased. In the sample No. B17 in
which the amount of the nickel powder was greater than 5%, the wear
amount of the valve sheet was remarkably increased because the
amount of the soft residual austenite phase was too large.
According to the above results, when the amount of the nickel
powder (the amount of Ni in the overall composition) was 1 to 5%,
the wear amount of the valve sheet was small.
Example B-4
[0086] The ore-reduced iron powder used in the example B-1, a
nickel powder, a graphite powder, and the hard phase forming alloy
powder used in the sample No. B04 in the example B-1 were prepared.
The ratio of the graphite powder was changed as shown in Table B-4,
these powders were added and mixed with a forming lubricant (0.8%
of zinc stearate), and a raw powder was obtained. The obtained raw
powder was compacted and sintered in the same way as in the example
A-1, and samples Nos. B18 to B23 were formed. The wear tests were
performed in the same way as in the example B-1 for these samples.
The results are shown in Table B-4 with the values of the sample
No. B04 in the example B-1.
TABLE-US-00007 TABLE B-4 Mixing ratio mass % Evaluation item Hard
phase forming alloy powder Wear amount .mu.m Sample Iron Nickel
Compositions mass % Graphite Valve No. powder powder Co Fe Cr Mo Si
powder sheet Valve Total Notes B18 Balance 2.00 35.00 Balance 17.00
30.00 20.00 3.00 0.30 125 2 127 Comparative example B19 Balance
2.00 35.00 Balance 17.00 30.00 20.00 3.00 0.50 67 3 70 Practical
example B20 Balance 2.00 35.00 Balance 17.00 30.00 20.00 3.00 0.80
36 3 39 Practical example B04 Balance 2.00 35.00 Balance 17.00
30.00 20.00 3.00 1.00 30 3 33 Practical example B21 Balance 2.00
35.00 Balance 17.00 30.00 20.00 3.00 1.20 36 4 40 Practical example
B22 Balance 2.00 35.00 Balance 17.00 30.00 20.00 3.00 1.50 65 8 73
Practical example B23 Balance 2.00 35.00 Balance 17.00 30.00 20.00
3.00 1.80 113 42 155 Comparative example
[0087] According to Table B-4, the influence of the amount of the
graphite powder (the amount of C in the overall composition) was
investigated. In the sample No. B18 in which the amount of the
graphite powder was less than 0.5%, the wear amount of the valve
sheet was large because Fe matrix of the sintered alloy was not
sufficiently strengthened. In the sample No. B19 in which the
amount of the graphite powder was 0.5%, the wear amount of the
valve sheet was remarkably decreased because the Fe matrix of the
sintered alloy was strengthened. When the amount of the graphite
powder was not more than 1.0%, the wear amount of the valve sheet
was decreased according to the increase in the amount of the
graphite powder. On the other hand, in the samples Nos. B21 and B22
in which the amount of the graphite powder was greater than 1.0%,
the wear amounts of valve sheet were increased because the Fe
matrix of the sintered alloy was hardened and embrittled. In the
sample No. B23 in which the amount of the graphite powder was
greater than 1.5%, this tendency was more remarkable, and therefore
the wear amount of the valve sheet was remarkably increased.
Moreover, the wear amount of the valve was also remarkably
increased because the wear particles of the valve sheet eroded the
valve. According to the above results, when the amount of the
graphite powder (the amount of C in the overall composition) was
0.5 to 1.5%, the wear amounts of the valve sheet and the valve were
small.
Example B-5
[0088] The ore-reduced iron powder used in the example B-1, a
nickel powder, a graphite powder, and a hard phase forming alloy
powder having a composition shown in Table B-5 were prepared. These
powders were added and mixed with a forming lubricant (0.8% of zinc
stearate) in the mixing ratio shown in Table B-5, and a raw powder
was obtained. The obtained raw powder was compacted and sintered in
the same way as in the example A-1, and samples Nos. B24 to B29
were formed. The wear tests were performed in the same way as in
the example B-1 for these samples. The results are shown in Table
B-5 with the values of the sample No. B04 in the example B-1.
TABLE-US-00008 TABLE B-5 Mixing ratio mass % Hard phase forming
alloy powder Evaluation item Compositions Substitutional Wear
amount .mu.m Sample Iron Nickel mass % ratio Graphite Valve No.
powder powder Co Fe Cr Mo Si of Fe powder sheet Valve Total Notes
B24 Balance 2.00 35.00 Balance 0.00 30.00 20.00 3.00 0.00 1.00 21 3
24 Comparative example B25 Balance 2.00 35.00 Balance 7.00 30.00
20.00 3.00 14.90 1.00 26 3 29 Practical example B04 Balance 2.00
35.00 Balance 17.00 30.00 20.00 3.00 36.20 1.00 30 3 33 Practical
example B26 Balance 2.00 35.00 Balance 27.00 30.00 20.00 3.00 57.40
1.00 34 3 37 Practical example B27 Balance 2.00 35.00 Balance 37.00
30.00 20.00 3.00 78.70 1.00 57 4 61 Practical example B28 Balance
2.00 35.00 Balance 42.00 30.00 20.00 3.00 89.40 1.00 101 5 106
Practical example B29 Balance 2.00 35.00 Balance 47.00 30.00 20.00
3.00 100.00 1.00 145 10 155 Comparative example
[0089] According to Table B-5, when Co in the hard phase forming
alloy powder was substituted by Fe, the influence of the
substitutional ratio of Fe was investigated. In the sample No. B24
in which Co in the hard phase forming alloy powder was not
substituted by Fe, the total of the wear amounts was the least
among the above examples B, and wear resistance was good. When Co
in the hard phase forming alloy powder was substituted by Fe and
the substitutional ratio of Fe was increased, the total of the wear
amounts was increased. In this case, when the substitutional ratio
of Fe was not more than 80%, wear amounts were not a problem in
practical use. On the other hand, when the substitutional ratio of
Fe was more than 80%, the wear amounts were remarkably increased
because the effect of Co was insufficient. According to the above
results, although Co in the hard phase forming alloy powder could
be substituted by Fe, the substitutional ratio of Fe should be not
more than 80%.
Example B-6
[0090] The ore-reduced iron powder used in the example B-1, a
nickel powder, a graphite powder, and a hard phase forming alloy
powder having a composition shown in Table B-6 were prepared. These
powders were added and mixed with a forming lubricant (0.8% of zinc
stearate) in the mixing ratio shown in Table B-6, and a raw powder
was obtained. The obtained raw powder was compacted and sintered in
the same way as in the example A-1, and samples Nos. B30 to B33
were formed. The wear tests were performed in the same way as in
the example B-1 for these samples. The results are shown in Table
B-6 with the values of the sample No. B04 in the example B-1.
TABLE-US-00009 TABLE B-6 Mixing ratio mass % Evaluation item Hard
phase forming alloy powder Wear amount .mu.m Sample Iron Nickel
Compositions mass % Graphite Valve No. powder powder Co Fe Cr Mo Si
Mn powder sheet Valve Total Notes B04 Balance 2.00 35.00 Balance
17.00 30.00 20.00 3.00 -- 1.00 30 3 33 Practical example B30
Balance 2.00 35.00 Balance 17.00 30.00 20.00 3.00 1.00 1.00 27 3 30
Practical example B31 Balance 2.00 35.00 Balance 17.00 30.00 20.00
3.00 3.00 1.00 23 4 27 Practical example B32 Balance 2.00 35.00
Balance 17.00 30.00 20.00 3.00 5.00 1.00 28 10 38 Practical example
B33 Balance 2.00 35.00 Balance 17.00 30.00 20.00 3.00 6.00 1.00 54
46 100 Comparative example
[0091] According to Table B-6, the effect of Mn in the hard phase
forming alloy powder was investigated. In the samples Nos. B30 to
B32 in which the amount of Mn in the hard phase forming alloy
powder was not more than 5%, the alloy matrix of the hard phase was
strengthened by Mn, whereby the wear amounts of the valve sheets
were less than that of the sample No. B04 in which Mn in the hard
phase forming alloy powder was not added. On the other hand, the
wear amounts of the valves were slightly increased according to the
increase in the amount of Mn because the hard phases were
strengthened. In the sample No. B33 in which Mn in the hard phase
forming alloy powder was more than 5%, the hard phase forming alloy
powder was hardened, and the compressibility of the raw powder was
greatly decreased. As a result, the wear amount of the valve sheet
was remarkably increased, and the wear amount of the valve was also
remarkably increased because the wear particles of the valve sheet
eroded the valve. According to the above results, although wear
resistance of the sintered alloy could be further improved by
adding Mn in the hard phase forming alloy powder, the amount of Mn
in the hard phase forming alloy powder should be not more than
5%.
Example B-7
[0092] The nickel powder used in the example B-1, a hard phase
forming alloy powder, a graphite powder, and an ore-reduced iron
powder in which the amount of metal oxides was different as shown
in Table B-7 were prepared. These powders were added and mixed with
a forming lubricant (0.8% of zinc stearate) in the mixing ratio
shown in Table B-7, and a raw powder was obtained. The obtained raw
powder was compacted and sintered in the same way as in the example
A-1, and samples Nos. B34 to B38 were formed. The wear tests were
performed in the same way as in the example B-1 for these samples.
Moreover, in the example B-7, machinability tests were performed.
In the machinability tests, holes were made in the samples with a
constant load by using a bench drill, and the numbers of the
machined holes were compared. In these tests, the load was 1.3 kg,
the drill was a carbide drill with a diameter of 3 mm, and the
thickness of sample was 5 mm. The numbers of the machined holes in
these machinability tests are shown in Table B-7.
TABLE-US-00010 TABLE B-7 Mixing ratio mass % Evaluation item Sam-
Iron powder Hard phase forming alloy powder Wear amount .mu.m
Number of ple Metal Nickel Compositions mass % Graphite Valve
machined No. oxide powder Co Fe Cr Mo Si powder sheet Valve Total
holes Notes B34 Balance 0.20 2.00 35.00 Balance 17.00 30.00 20.00
3.00 1.00 32 3 35 5 Comparative example B35 Balance 0.30 2.00 35.00
Balance 17.00 30.00 20.00 3.00 1.00 31 3 34 11 Practical example
B04 Balance 1.00 2.00 35.00 Balance 17.00 30.00 20.00 3.00 1.00 30
3 33 20 Practical example B36 Balance 0.50 2.00 35.00 Balance 17.00
30.00 20.00 3.00 1.00 30 3 33 15 Practical example B37 Balance 1.50
2.00 35.00 Balance 17.00 30.00 20.00 3.00 1.00 41 10 51 23
Practical example B38 Balance 2.00 2.00 35.00 Balance 17.00 30.00
20.00 3.00 1.00 95 36 131 25 Comparative example
[0093] According to Table B-7, the influence of the amount of metal
oxides in the ore-reduced iron powder (the amount of metal oxides
in the matrix of the sintered alloy) was investigated. In the
samples Nos. B34 to B36 and B04 in which the amount of metal oxides
in the ore-reduced iron powder was 0.2 to 1.0%, the wear amounts
were approximately equal. On the other hand, in the sample No. B37
in which the amount of metal oxides in the ore-reduced iron powder
was 1.5%, the iron powder was hardened by the increase in the metal
oxides in the ore-reduced iron powder, whereby the compressibility
of the raw powder was decreased, and the wear amounts were
increased. In the sample No. B38 in which the amount of metal
oxides in the ore-reduced iron powder was greater than 1.5%, the
wear amount was remarkably increased because compressibility of the
raw powder was remarkably decreased. In the sample No. B34 in which
the amount of metal oxides in the ore-reduced iron powder was 0.2%,
there were 5 machined holes, and the machinability was not good. On
the other hand, in the sample No. B35 in which the amount of metal
oxides in the ore-reduced iron powder was 0.3%, the number of the
machined holes was 11, and the machinability was improved and was
more than twice the number of the machined holes of the sample No.
B34. When the amount of metal oxides was further increased, the
numbers of the machined holes were increased and the machinability
was improved. However, in the sample No. B38 in which the amount of
metal oxides in the ore-reduced iron powder was greater than 1.5%,
the effect of the machinability improvement was insufficient.
Accordingly, the amount of metal oxides in the ore-reduced iron
powder (the amount of metal oxides in the matrix of the sintered
alloy) was preferably not less than 0.3% from the viewpoint of
machinability, and preferably not more than 1.5% from the viewpoint
of wear resistance and machinability.
Example C
Fe--Cr--C Alloy Matrix
Example C-1
[0094] An iron alloy powder consisting of 3% of Cr and the balance
of Fe and inevitable impurities, a hard phase forming alloy powder
having a composition shown in Table C-1, and a graphite powder were
prepared. The iron alloy powder, 35% of the hard phase forming
alloy powder, and 1% of the graphite powder were added and mixed.
Furthermore, 0.8 mass parts of zinc stearate as a forming lubricant
was added and mixed with 100 mass parts of the mixed powder, and a
raw powder was obtained. The obtained raw powder was compacted and
sintered in the same way as in the example A-1, and samples Nos.
C01 to C06 were formed. The simple wear tests and the corrosion
tests were performed in the same way as in the example A-1 for
these samples. In the simple wear tests, the mating materials were
heated with a burner so that the sintered alloys reached
300.degree. C., and the colliding frequency was 3000 times per
minute, and the time during which this was conducted was 15 hours.
The results of these tests are also shown in Table C-1.
TABLE-US-00011 TABLE C-1 Mixing ratio mass % Evaluation item Hard
phase forming alloy powder Wear amount .mu.m Corrosion Sample Iron
alloy Composition mass % Graphite Valve loss No. powder Co Fe Cr Mo
Si powder sheet Valve Total mg/cm.sup.2 Notes C01 Balance 35.00
Balance 42.00 5.00 20.00 3.00 1.00 83 3 86 0.31 Comparative example
C02 Balance 35.00 Balance 37.00 10.00 20.00 3.00 1.00 52 4 56 0.15
Practical example C03 Balance 35.00 Balance 27.00 20.00 20.00 3.00
1.00 35 4 39 0.12 Practical example C04 Balance 35.00 Balance 17.00
30.00 20.00 3.00 1.00 26 4 30 0.10 Practical example C05 Balance
35.00 Balance 7.00 40.00 20.00 3.00 1.00 40 6 46 0.13 Practical
example C06 Balance 35.00 Balance 2.00 45.00 20.00 3.00 1.00 72 25
97 0.23 Comparative example
[0095] According to Table C-1, the influence of the amount of Cr in
the hard phase forming alloy powder (the amount of Cr in the hard
phase) was investigated. In the sample No. C01, the amount of Cr in
the hard phase forming alloy powder was insufficient, whereby
corrosion resistance was insufficient and the corrosion loss was
large. Moreover, since the amount of Cr was insufficient, the
matrix of the sintered alloy was not sufficiently strengthened, and
the wear amount of the valve sheet was also large. On the other
hand, in the sample No. C02 in which the amount of Cr in the hard
phase forming alloy powder was 10%, the corrosion loss was reduced
because corrosion resistance was improved by Cr, and the wear
amount of the valve sheet was remarkably decreased because the
matrix was strengthened by Cr. When the amount of Cr in the hard
phase forming alloy powder was not more than 30%, the wear amounts
of the valve sheets were at low levels, and the corrosion losses
were reduced to low levels according to the increase in the amount
of Cr. In the sample No. C05 in which the amount of Cr in the hard
phase forming alloy powder was 40%, the hardness of the hard phase
forming alloy powder was increased by the increase in the amount of
Cr in the hard phase forming alloy powder, whereby the
compressibility of the raw powder was decreased, and the density of
the green compact was decreased. As a result, the density of the
sintered compact was decreased, whereby the wear amount of the
valve sheet and the corrosion loss were increased, but these values
were sufficiently small. Moreover, the wear particles of the valve
sheet eroded the valve, and the wear amount of the valve was also
increased, but this value was small. In the sample No. C06 in which
the amount of Cr in the hard phase forming alloy powder was greater
than 40%, this tendency was more remarkable, and therefore the
total of the wear amounts and the corrosion loss were remarkably
increased. According to the above results, when the amount of Cr in
the hard phase forming alloy powder was 10 to 40%, the wear amounts
of the valve sheet and the valve were small and the corrosion loss
of the sintered alloy was small.
Example C-2
[0096] The iron alloy powder (Fe-3% Cr powder) used in the example
C-1, the hard phase forming alloy powder (Co-30% Cr-20% Mo-17%
Fe-3% Si powder) used in the sample No. C04 in the example C-1, and
a graphite powder were prepared. The ratio of the hard phase
forming alloy powder was changed as shown in Table C-2, and these
powders were added and mixed. Furthermore, 0.8 mass parts of zinc
stearate as a forming lubricant was added and mixed with 100 mass
parts of the mixed powder, and a raw powder was obtained. The
obtained raw powder was compacted and sintered in the same way as
in the example A-1, and samples Nos. C07 to C11 were formed. The
wear tests and the corrosion tests were performed in the same way
as in the example C-1 for these samples. The results are shown in
Table C-2 with the values of the sample No. C04 in the example
C-1.
TABLE-US-00012 TABLE C-2 Mixing ratio mass % Hard phase Evaluation
item forming Wear amount .mu.m Corrosion Sample Iron alloy alloy
Graphite Valve loss No. powder powder powder sheet Valve Total
mg/cm.sup.2 Notes C07 Balance 5.00 1.00 102 2 104 0.53 Comparative
example C08 Balance 15.00 1.00 49 3 52 0.24 Practical example C09
Balance 25.00 1.00 30 4 34 0.14 Pracitcal example C04 Balance 35.00
1.00 26 4 30 0.10 Practical example C10 Balance 45.00 1.00 42 9 51
0.15 Practical example C11 Balance 55.00 1.00 77 36 113 0.30
Comparative example
[0097] According to Table C-2, the influence of the amount of the
hard phase forming alloy powder (the amount of the hard phase
dispersed in the matrix) was investigated. In the sample No. C07 in
which the amount of the hard phase forming alloy powder was less
than 15%, the wear amount of the valve sheet was large, because the
amount of the hard phase was insufficient and the plastic flow of
the matrix could not be prevented. Moreover, the corrosion loss was
large, because the hard phase was insufficient and Cr was not
sufficiently dispersed from the hard phase to the matrix. On the
other hand, in the sample No. C08 in which the amount of the hard
phase forming alloy powder was 15%, wear resistance and corrosion
resistance of the matrix of the sintered alloy were improved by the
hard phase, and the wear amount of the valve sheet was remarkably
decreased and the corrosion loss was decreased. When the amount of
the hard phase forming alloy powder was not more than 35%, the wear
amount of the valve sheet and the corrosion loss were decreased
according to the increase in the amount of the hard phase forming
alloy powder. In the sample No. C10 in which the amount of the hard
phase forming alloy powder was 45%, compressibility of the raw
powder was decreased by the increase in the amount of the hard
phase forming alloy powder, whereby the wear amount of the valve
sheet and the corrosion loss were slightly increased, but these
were at low levels. In the sample No. C11 in which the amount of
the hard phase forming alloy powder was greater than 45%, the wear
amount of the valve sheet was remarkably increased and the
corrosion loss was increased, because the influence of the decrease
of compressibility was remarkable. Moreover, the wear amount of the
valve was also remarkably increased because the wear particles of
the valve sheet eroded the valve. According to the above results,
when the amount of the hard phase forming alloy powder (the amount
of the hard phase dispersed in the matrix) was 15 to 45%, the wear
amounts of the valve sheet and the valve were small.
Example C-3
[0098] An iron alloy powder having a composition shown in Table
C-3, a graphite powder, and the hard phase forming alloy powder
(Co-30% Cr-20% Mo-17% Fe-3% Si powder) used in the sample No. C04
in the example C-1 were prepared. The iron alloy powder, 35% of the
hard phase forming alloy powder, and 1% of the graphite powder were
added and mixed. Furthermore, 0.8 mass parts of zinc stearate as a
forming lubricant was added and mixed with 100 mass parts of the
mixed powder, and a raw powder was obtained. The obtained raw
powder was compacted and sintered in the same way as in the example
A-1, and samples Nos. C12 to C17 were formed. The wear tests and
the corrosion tests were performed in the same way as in the
example C-1 for these samples. The results are shown in Table C-3
with the values of the sample No. C04 in the example C-1.
TABLE-US-00013 TABLE C-3 Mixing ratio mass % Hard phase Evaluation
item Iron alloy powder forming Wear amount .mu.m Corrosion Sample
compositions alloy Graphite Valve loss No. Fe Cr powder powder
sheet Valve Total mg/cm.sup.2 Notes C12 Balance Balance 0.00 35.00
1.00 103 3 106 0.22 Comparative example C13 Balance Balance 1.00
35.00 1.00 43 4 47 0.16 Practical example C14 Balance Balance 2.00
35.00 1.00 30 4 34 0.13 Practical example C04 Balance Balance 3.00
35.00 1.00 26 4 30 0.10 Practical example C15 Balance Balance 4.00
35.00 1.00 29 4 33 0.09 Practical example C16 Balance Balance 5.00
35.00 1.00 48 5 53 0.16 Practical example C17 Balance Balance 6.00
35.00 1.00 80 6 86 0.25 Comparative example
[0099] According to Table C-3, the influence of the amount of Cr in
the iron alloy powder was investigated. In the sample No. C12 using
a pure iron powder in which Cr was not added, the wear amount of
the valve sheet and the corrosion loss were large because Fe matrix
of the sintered alloy was not strengthened. In the sample No. C13
in which the amount of Cr in the iron alloy powder was 1%, the wear
amount of the valve sheet was remarkably decreased because the Fe
matrix was strengthened by Cr, and the corrosion loss was decreased
because the corrosion resistance of the Fe matrix was improved.
When the amount of Cr in the iron alloy powder was not more than
3%, the wear amount of the valve sheet and the corrosion loss were
decreased according to the increase in the amount of Cr in the iron
alloy powder. In the samples Nos. C15 and C16 in which the amount
of Cr in the iron alloy powder was 4 to 5%, the hardness of the
iron alloy powder was increased, whereby compressibility of the raw
powder was decreased, and the density of the green compact was
decreased. As a result, the density of the sintered compact was
decreased, whereby the wear amount of the valve sheet and the
corrosion loss were slightly increased, but these were at low
levels. On the other hand, in the sample No. C17 in which the
amount of Cr in the iron alloy powder was greater than 5%, the
influence of the. increase in the hardness of the iron alloy powder
was remarkable, and the density of the sintered compact was
remarkably decreased, whereby the wear amount of the valve sheet
and the corrosion loss were remarkably increased. According to the
above results, when the amount of Cr in the iron alloy powder was 1
to 5%, the wear amount of the valve sheet was small and the
corrosion loss was reduced.
Example C-4
[0100] The iron alloy powder (Fe-3% Cr powder) used in the example
C-1, the hard phase forming alloy powder (Co-30% Cr-20% Mo-17%
Fe-3% Si powder) used in the sample No. C04 in the example C-1, and
a graphite powder were prepared. The ratio of the graphite powder
was changed as shown in Table C-4, and these powders were added and
mixed. Furthermore, 0.8 mass parts of zinc stearate as a forming
lubricant was added and mixed with 100 mass parts of the mixed
powder, and a raw powder was obtained. The obtained raw powder was
compacted and sintered in the same way as in the example A-1, and
samples Nos. C18 to C23 were formed. The wear tests were performed
in the same way as in the example C-1 for these samples. The
results are shown in Table C-4 with the values of the sample No.
C04 in the example C-1.
TABLE-US-00014 TABLE C-4 Mixing ratio mass % Hard phase Evaluation
item forming Wear amount .mu.m Iron alloy alloy Graphite Valve
Sample No. powder powder powder sheet Valve Total Notes C18 Balance
35.00 0.30 107 3 110 Comparative example C19 Balance 35.00 0.50 57
4 61 Practical example C20 Balance 35.00 0.80 31 4 35 Practical
example C04 Balance 35.00 1.00 26 4 30 Practical example C21
Balance 35.00 1.20 30 5 35 Practical example C22 Balance 35.00 1.50
55 9 64 Practical example C23 Balance 35.00 1.80 96 43 139
Comparative example
[0101] According to Table C-4, the influence of the amount of the
graphite powder (the amount of C in the overall composition) was
investigated. In the sample No. C18 in which the amount of the
graphite powder was less than 0.5%, the wear amount of the valve
sheet was large because Fe matrix of the sintered alloy was not
sufficiently strengthened. However, in the sample No. C19 in which
the amount of the graphite powder was 0.5%, the wear amount of the
valve sheet was remarkably decreased because Fe matrix of the
sintered alloy was strengthened. When the amount of the graphite
powder was not more than 1.0%, the wear amount of the valve sheet
was decreased according to the increase in the amount of the
graphite powder. In the sample in which the amount of the graphite
powder was 1.2 to 1.5%, the wear amount of the valve sheet was
increased and the wear amount of the valve was slightly increased
because Fe matrix of the sintered alloy was hardened and
embrittled. In this case, the total of the wear amounts was not a
problem in practical use. On the other hand, in the sample No. C23
in which the amount of the graphite powder was greater than 1.5%,
this tendency was more remarkable, and therefore the wear amount of
the valve sheet was remarkably increased. Moreover, the wear amount
of the valve was also remarkably increased because the wear
particles of the valve sheet eroded the valve. According to the
above results, when the amount of the graphite powder (the amount
of C in the overall composition) was 0.5 to 1.5%, the wear amounts
of the valve sheet and the valve were small.
Example C-5
[0102] The iron alloy powder (Fe-3% Cr powder) used in the example
C-1, a graphite powder, and a hard phase forming alloy powder as
shown in Table C-5 were prepared. The hard phase forming alloy
powder has a composition in which a ratio of Co and Fe was
different from that of the hard phase forming alloy powder (Co-30%
Cr-20% Mo-17% Fe-3% Si powder) used in the sample No. C04 in the
example C-1. The iron alloy powder, 35% of the hard phase forming
alloy powder, and 1% of the graphite powder were added and were
mixed. Furthermore, 0.8 mass parts of zinc stearate as a forming
lubricant was added and mixed with 100 mass parts of the mixed
powder, and a raw powder was obtained. The obtained raw powder was
compacted and sintered in the same way as in the example A-1, and
samples Nos. C24 to C29 were formed. The wear tests were performed
in the same way as in the example C-1 for these samples. The
results are shown in Table C-5 with the values of the sample No.
C04 in the example C-1.
TABLE-US-00015 TABLE C-5 Mixing ratio mass % Evaluation item Hard
phase forming alloy powder Wear amount .mu.m Sample Iron alloy
Compositions mass % Substitutional Graphite Valve No. powder Co Fe
Cr Mo Si ratio of Fe powder sheet Valve Total Notes C24 Balance
35.00 Balance 0.00 30.00 20.00 3.00 0.00 1.00 18 3 21 Comparative
example C25 Balance 35.00 Balance 7.00 30.00 20.00 3.00 14.90 1.00
22 4 26 Practical example C04 Balance 35.00 Balance 17.00 30.00
20.00 3.00 36.20 1.00 26 4 30 Practical example C26 Balance 35.00
Balance 28.00 30.00 20.00 3.00 59.60 1.00 29 4 33 Practical example
C27 Balance 35.00 Balance 37.50 30.00 20.00 3.00 79.80 1.00 46 5 51
Practical example C28 Balance 35.00 Balance 42.00 30.00 20.00 3.00
89.40 1.00 86 6 92 Practical example C29 Balance 35.00 Balance
47.00 30.00 20.00 3.00 100.00 1.00 123 11 134 Comparative
example
[0103] According to Table C-5, when Co in the hard phase forming
alloy powder was substituted by Fe, the influence of the
substitutional ratio of Fe was investigated. In the sample No. C24
in which Co in the hard phase forming alloy powder was not
substituted by Fe, the wear amounts were the least among the above
examples C, and wear resistance was good. When Co in the hard phase
forming alloy powder was substituted by Fe and the substitutional
ratio of Fe was increased, the wear amounts were increased. In this
case, when the substitutional ratio of Fe was not more than 80%
(samples Nos. C04 and C25 to C27), the wear amounts were not
problem in practical use. However, in the samples Nos. C28 and C29
in which the substitutional ratio of Fe was more than 80%, the wear
amounts were remarkably increased because the effect of Co was
insufficient. According to the above results, although Co in the
hard phase forming alloy powder could be substituted by Fe, the
substitutional ratio of Fe should be not more than 80%.
Furthermore, the substitutional ratio of Fe was preferably not more
than 60%.
Example C-6
[0104] The iron alloy powder (Fe-3% Cr powder) used in the example
C-1, a graphite powder, and a hard phase forming alloy powder as
shown in Table C-6 were prepared. The hard phase forming alloy
powder was formed by adding different amount of Mn in the hard
phase forming alloy powder (Co-30% Cr-20% Mo-17% Fe-3% Si powder)
used in the sample No. C04 in the example C-1. The iron alloy
powder, 35% of the hard phase forming alloy powder, and 1% of the
graphite powder were added and mixed. Furthermore, 0.8 mass parts
of zinc stearate as a forming lubricant was added and mixed with
100 mass parts of the mixed powder, and a raw powder was obtained.
The obtained raw powder was compacted and sintered in the same way
as in the example A-1, and samples Nos. C30 to C33 were formed. The
wear tests were performed in the same way as in the example C-1 for
these samples. The results are shown in Table C-6 with the values
of the sample No. C04 in the example C-1.
TABLE-US-00016 TABLE C-6 Mixing ratio mass % Evaluation item Hard
phase forming alloy powder Wear amount .mu.m Sample Iron alloy
Compositions mass % Graphite Valve No. powder Co Fe Cr Mo Si Mn
powder sheet Valve Total Notes C04 Balance 35.00 Balance 17.00
30.00 20.00 3.00 -- 1.00 26 4 30 Practical example C30 Balance
35.00 Balance 17.00 30.00 20.00 3.00 1.00 1.00 23 5 28 Practical
example C31 Balance 35.00 Balance 17.00 30.00 20.00 3.00 3.00 1.00
20 5 25 Practical example C32 Balance 35.00 Balance 17.00 30.00
20.00 3.00 5.00 1.00 24 11 35 Practical example C33 Balance 35.00
Balance 17.00 30.00 20.00 3.00 7.00 1.00 46 49 95 Comparative
example
[0105] According to Table C-6, the effect of Mn added in the hard
phase forming alloy powder (the hard phase) was investigated. In
the samples Nos. C30 to C32 in which the amount of Mn in the hard
phase forming alloy powder was not more than 5%, the alloy matrix
of the hard phase was strengthened by Mn, whereby the wear amounts
of the valve sheets were less than that of the sample No. C04 in
which Mn in the hard phase forming alloy powder was not added. On
the other hand, the wear amounts of the valves were slightly
increased according to the increase in the amount of Mn, because
the hard phase was strengthened. In the sample No. C33 in which the
amount of Mn in the hard phase forming alloy powder was greater
than 5%, the hard phase forming alloy powder was hardened, whereby
compressibility of the raw powder was decreased. Therefore, the
wear amount of the valve sheet was remarkably increased, and the
wear amount of the valve was also remarkably increased because the
wear particles of the valve sheet eroded the valve. According to
the above results, although wear resistance of the sintered alloy
could be further improved by adding Mn in the hard phase forming
alloy powder, the amount of Mn in the hard phase forming alloy
powder should be not more than 5%.
Example C-7
[0106] An iron alloy powder having a composition shown in Table
C-7, the hard phase forming alloy powder (Co-30% Cr-20% Mo-17%
Fe-3% Si powder) used in the sample No. C04 in the example C-1, and
a graphite powder were prepared. The iron alloy powder was formed
by adding at least one of Mo, V, and Nb in the iron alloy powder
(Fe-3% Cr powder) used in the example C-1. The iron alloy powder,
35% of the hard phase forming alloy powder, and 1% of the graphite
powder were added and mixed. Furthermore, 0.8 mass parts of zinc
stearate as a forming lubricant was added and mixed with 100 mass
parts of the mixed powder, and a raw powder was obtained. The
obtained raw powder was compacted and sintered in the same way as
in the example A-1, and samples Nos. C34 to C44 were formed. The
wear tests were performed in the same way as in the example C-1 for
these samples. The results are shown in Table C-7 with the values
of the sample No. C04 in the example C-1.
TABLE-US-00017 TABLE C-7 Mixing ratio mass % Hard phase Evaluation
item Iron alloy powder forming Wear amount .mu.m Sample
Compositions mass % alloy Graphite Valve No. Fe Cr Mo V Nb powder
powder sheet Valve Total Notes C04 Balance Balance 3.00 -- -- --
35.00 1.00 26 4 30 Practical example C34 Balance Balance 3.00 0.50
-- -- 35.00 1.00 22 5 27 Practical example C35 Balance Balance 3.00
0.50 0.50 -- 35.00 1.00 18 7 25 Practical example C36 Balance
Balance 3.00 0.50 -- 0.50 35.00 1.00 19 6 25 Practical example C37
Balance Balance 3.00 0.50 0.50 0.50 35.00 1.00 15 11 26 Practical
example C38 Balance Balance 3.00 1.00 -- -- 35.00 1.00 18 7 25
Practical example C39 Balance Balance 3.00 1.50 -- -- 35.00 1.00 14
10 24 Practical example C40 Balance Balance 3.00 2.00 -- -- 35.00
1.00 13 15 28 Practical example C41 Balance Balance 3.00 1.50 0.50
-- 35.00 1.00 13 13 26 Practical example C42 Balance Balance 3.00
2.00 1.00 -- 35.00 1.00 18 21 39 Comparative example C43 Balance
Balance 3.00 2.40 -- -- 35.00 1.00 13 15 28 Practical example C44
Balance Balance 3.00 3.00 -- -- 35.00 1.00 16 25 41 Comparative
example
[0107] According to samples Nos. C04, C34, C38 to C40, C43, and C44
in Table C-7, the effect of the amount of Mo in the iron alloy
powder was investigated. In these samples, compared with the sample
No. C04 in which Mo was not added in the iron alloy powder, when Mo
was added in the iron alloy powder and the amount of Mo was
increased, the wear amounts of the valves were slightly increased,
but the wear amounts of valve sheets were decreased and the totals
of the wear amounts were decreased. However, in the sample No. C44
in which the amount of Mo in the iron alloy powder was greater than
2.4%, the wear amount of the valve sheet was increased and the
total of the wear amounts was increased.
[0108] The sample No. C38 included Mo in the iron alloy powder at
1%, and the sample No. C35 included Mo in the iron alloy powder at
0.5% and included V in the iron alloy powder at 0.5% (the total
amount of Mo and V was 1.0%). The sample No. C36 included Mo in the
iron alloy powder at 0.5% and included Nb in the iron alloy powder
at 0.5% (the total amount of Mo and Nb was 1.0%). In these samples
Nos. C38, C35, and C36, the wear amounts of the valve sheets were
approximately equal and the wear amounts of the valves were
approximately equal. The sample No. C39 included Mo in the iron
alloy powder at 1.5%, and the sample No. C37 included Mo, V, and Nb
in the iron alloy powder at respectively 0.5% (the total amount of
Mo, V, and Nb was 1.5%). In these samples Nos. C39 and C37, the
wear amounts of the valve sheets were approximately equal and the
wear amounts of the valves were approximately equal. The sample No.
C42 included Mo in the iron alloy powder at 2.0%, and the sample
No. C41 included Mo in the iron alloy powder at 1.5% and included V
in the iron alloy powder at 0.5% (the total amount of Mo and V was
2.0%). In these samples Nos. C42 and C41, the wear amounts of the
valve sheets were approximately equal and the wear amounts of the
valves were approximately equal. The sample No. C44 included Mo in
the iron alloy powder at 3.0%, and the sample No. C42 included Mo
in the iron alloy powder at 2.0% and included V in the iron alloy
powder at 1.0% (the total amount of Mo and V was 3.0%). In these
samples Nos. C44 and C42, the wear amounts of valve sheets were
approximately equal, the wear amounts of valves were approximately
equal, and the totals of the wear amounts were increased.
Accordingly, Mo, V, and Nb in the iron alloy powder had
approximately equal effects, and the wear resistance was improved
when the total amount of Mo, V, and Nb in the iron alloy powder was
not more than 2.4%.
Example C-8
[0109] The iron alloy powder (Fe-3% Cr powder) used in the example
C-1, the hard phase forming alloy powder (Co-30% Cr-20% Mo-17%
Fe-3% Si powder) used in the sample No. C04 in the example C-1, a
graphite powder, and a nickel powder were prepared. The iron alloy
powder, 35% of the hard phase forming alloy powder, 1% of the
graphite powder, and a ratio shown in Table C-8 of the nickel
powder were added and mixed. Furthermore, 0.8 mass parts of zinc
stearate as a forming lubricant was added and mixed with 100 mass
parts of the mixed powder, and a raw powder was obtained. The
obtained raw powder was compacted and sintered in the same way as
in the example A-1, and samples Nos. C45 to C50 were formed. The
wear tests were performed in the same way as in the example C-1 for
these samples. The results are shown in Table C-8 with the values
of the sample No. C04 in the example C-1.
TABLE-US-00018 TABLE C-8 Mixing ratio mass % Hard phase Evaluation
item forming Wear amount .mu.m Sample Iron alloy alloy Graphite
Nickel Valve No. powder powder powder powder sheet Valve Total
Notes C04 Balance 35.00 1.00 0.00 26 4 30 Practical example C45
Balance 35.00 1.00 1.00 23 4 27 Practical example C46 Balance 35.00
1.00 2.00 22 4 26 Practical example C47 Balance 35.00 1.00 3.00 21
4 25 Practical example C48 Balance 35.00 1.00 4.00 22 4 26
Practical example C49 Balance 35.00 1.00 5.00 25 5 30 Practical
example C50 Balance 35.00 1.00 7.00 67 8 75 Comparative example
[0110] According to Table C-8, compared with the sample No. C04 in
which the nickel powder was not added to the raw powder and Ni was
not added in the matrix, in the samples Nos. C45 to C49, in which
the nickel powder was added at not more than 5%, the wear amounts
of the valve sheets were decreased and the totals of the wear
amounts were decreased. In the sample No. C50 in which the amount
of the nickel powder was greater than 5%, a large amount of Ni-rich
austenite having low wear resistance was formed and remained in the
matrix, whereby the wear resistance of the valve sheet was
decreased and the wear amount of the valve sheet was increased.
Moreover, the amount of hard martensite was increased, and the
degree of erosion of the valve (the mating material) was increased,
whereby the wear amount of the valve was increased and the total of
the wear amounts was remarkably increased. Accordingly, although
wear resistance was improved by adding the nickel powder, the
amount of the nickel powder should be not more than 5.0%.
Example D
Fe--Co--C Alloy Matrix
Example D-1
[0111] An iron alloy powder consisting of 6.5% of Co, 1.5% of Ni,
1.5% of Mo, and the balance of Fe and inevitable impurities, a hard
phase forming alloy powder having a composition shown in Table D-1,
and a graphite powder were prepared. The iron alloy powder, 35% of
the hard phase forming alloy powder, and 1% of the graphite powder
were added and mixed. Furthermore, 0.8 mass parts of zinc stearate
as a forming lubricant was added and mixed with 100 mass parts of
the mixed powder, and a raw powder was obtained. The obtained raw
powder was compacted and sintered in the same way as in the example
A-1, and samples Nos. D01 to D06 were formed. The simple wear tests
and the corrosion tests were performed in the same way as in the
example C-1 for these samples. The results of these tests are also
shown in Table D-1.
TABLE-US-00019 TABLE D-1 Mixing ratio mass % Evaluation item Hard
phase forming alloy powder Wear amount .mu.m Corrosion Sample Iron
alloy Compositions mass % Graphite Valve loss No. powder Co Fe Cr
Mo Si powder sheet Valve Total mg/cm.sup.2 Notes D01 Balance 35.00
Balance 42.00 5.00 20.00 3.00 1.00 74 2 76 0.30 Comparative example
D02 Balance 35.00 Balance 37.00 10.00 20.00 3.00 1.00 45 2 47 0.16
Practical example D03 Balance 35.00 Balance 27.00 20.00 20.00 3.00
1.00 29 2 31 0.14 Practical example D04 Balance 35.00 Balance 17.00
30.00 20.00 3.00 1.00 21 2 23 0.11 Practical example D05 Balance
35.00 Balance 7.00 40.00 20.00 3.00 1.00 35 4 39 0.16 Practical
example D06 Balance 35.00 Balance 2.00 45.00 20.00 3.00 1.00 69 20
89 0.26 Comparative example
[0112] According to Table D-1, the influence of the amount of Cr in
the hard phase forming alloy powder (the amount of Cr in the hard
phase) was investigated. In the sample No. D01, the amount of Cr in
the hard phase forming alloy powder was insufficient, whereby the
matrix of sintered alloy was not sufficiently strengthened, and the
wear amount of the valve sheet was large. Moreover, since the
amount of Cr was insufficient, the corrosion resistance was
insufficient, and the corrosion loss was also large. In the sample
No. D02 in which the amount of Cr in the hard phase forming alloy
powder was 10%, the wear amount of the valve sheet was remarkably
decreased because the matrix was strengthened by Cr. Moreover, the
corrosion loss was reduced because corrosion resistance was
improved. When the amount of Cr in the hard phase forming alloy
powder was not more than 30%, the wear amounts of the valve sheets
were at low levels and the corrosion losses were reduced according
to the increase in amount of Cr. In the sample No. D05 in which the
amount of Cr in the hard phase forming alloy powder was 40%, the
hardness of the hard phase forming alloy powder was increased by
the increase in the amount of Cr in the hard phase forming alloy
powder, whereby compressibility of the raw powder was decreased,
and the density of the green compact was decreased. As a result,
the density of the sintered compact was decreased, whereby the wear
amount of the valve sheet and the corrosion loss were increased,
but these values were sufficiently small. Moreover, the wear amount
of the valve was also increased because the wear particles of the
valve sheet eroded the valve, but this value was small. However, in
the sample No. D06 in which the amount of Cr in the hard phase
forming alloy powder was greater than 40%, this tendency was more
remarkable, and therefore the total of the wear amounts and the
corrosion loss were remarkably increased. According to the above
results, when the amount of Cr in the hard phase forming alloy
powder (the amount of Cr in the hard phase) was 10 to 40%, the wear
amounts of the valve sheet and the valve were small and the
corrosion loss of the sintered alloy was small.
Example D-2
[0113] The iron alloy powder (Fe-6.5% Co-1.5% Ni-1.5% Mo powder)
used in the example D-1, the hard phase forming alloy powder
(Co-30% Cr-20% Mo-17% Fe-3% Si powder) used in the sample No. D04
in the example D-1, and a graphite powder were prepared. The ratio
of the hard phase forming alloy powder were changed as shown in
Table D-2, and these powders were added and mixed. Furthermore, 0.8
mass parts of zinc stearate as a forming lubricant was added and
mixed with 100 mass parts of the mixed powder, and a raw powder was
obtained. The obtained raw powder was compacted and sintered in the
same way as in the example A-1, and samples Nos. D07 to D11 were
formed. The wear tests and the corrosion tests were performed in
the same way as in the example C-1 for these samples. The results
are shown in Table D-2 with the values of the sample No. D04 in the
example D-1.
TABLE-US-00020 TABLE D-2 Mixing ratio mass % Hard phase Evaluation
item forming Wear amount .mu.m Corrosion Sample Iron alloy alloy
Graphite Valve loss No. powder powder powder sheet Valve Total
mg/cm.sup.2 Notes D07 Balance 5.00 1.00 102 2 104 0.49 Comparative
example D08 Balance 15.00 1.00 46 1 47 0.22 Practical example D09
Balance 25.00 1.00 25 2 27 0.16 Practical example D04 Balance 35.00
1.00 21 2 23 0.11 Practical example D10 Balance 45.00 1.00 38 5 43
0.14 Practical example D11 Balance 55.00 1.00 73 34 107 0.24
Comparative example
[0114] According to Table D-2, the influence of the amount of the
hard phase forming alloy powder (the amount of the hard phase
dispersed in the matrix) was investigated. In the sample No. D07 in
which the amount of the hard phase forming alloy powder was less
than 15%, the wear amount of the valve sheet was large because the
amount of the hard phase was insufficient and the plastic flow of
the matrix could not be prevented. Moreover, the hard phase was
insufficient, and Cr was not sufficiently dispersed from the hard
phase to the matrix, whereby the corrosion loss was large. In the
sample No. D08 in which the amount of the hard phase forming alloy
powder was 15%, wear resistance and corrosion resistance of the
matrix of the sintered alloy were improved by the hard phase, and
the wear amount of the valve sheet was remarkably decreased and the
corrosion loss was decreased. When the amount of the hard phase
forming alloy powder was not more than 35%, the wear amount of the
valve sheet and the corrosion loss were decreased according to the
increase in the amount of the hard phase forming alloy powder. In
the sample No. D10 in which the amount of the hard phase forming
alloy powder was 45%, compressibility of the raw powder was
decreased by the increase in the amount of the hard phase forming
alloy powder, whereby the wear amount of the valve sheet and the
corrosion loss were slightly increased, but these were at low
levels. On the other hand, in the sample No. D11 in which the
amount of the hard phase forming alloy powder was greater than 45%,
the influence of the decrease of compressibility was remarkable,
whereby the wear amount of the valve sheet was remarkably
increased, and the corrosion loss was increased. Moreover, the wear
amount of the valve was also remarkably increased because the wear
particles of the valve sheet eroded the valve. According to the
above results, when the amount of the hard phase forming alloy
powder (the amount of the hard phase dispersed in the matrix) was
15 to 45%, the wear amounts of the valve sheet and the valve were
small.
Example D-3
[0115] An iron alloy powder as shown in Table D-3, a graphite
powder, and the hard phase forming alloy powder (Co-30% Cr-20%
Mo-17% Fe-3% Si powder) used in the sample No. D04 in the example
D-1 were prepared. In the iron alloy powder, the amount of Co was
different from that of the iron alloy powder used in the example
D-1. The iron alloy powder, 35% of the hard phase forming alloy
powder, and 1% of the graphite powder were added and mixed.
Furthermore, 0.8 mass parts of zinc stearate as a forming lubricant
was added and mixed with 100 mass parts of the mixed powder. The
obtained raw powder was compacted and sintered in the same way as
in the example A-1, and samples Nos. D12 to D16 were formed. The
wear tests and the corrosion tests were performed in the same way
as in the example C-1 for these samples. The results are shown in
Table D-3 with the values of the sample No. D04 in the example
D-1.
TABLE-US-00021 TABLE D-3 Mixing ratio mass % Hard phase Evaluation
item Iron alloy powder forming Wear amount .mu.m Corrosion Sample
compositions mass % alloy Graphite Valve loss No. Fe Co Ni Mo
powder powder sheet Valve Total mg/cm.sup.2 Notes D12 Balance
Balance 1.00 1.50 1.50 35.00 1.00 89 1 90 0.17 Comparative example
D13 Balance Balance 3.00 1.50 1.50 35.00 1.00 42 2 44 0.15
Practical example D14 Balance Balance 5.00 1.50 1.50 35.00 1.00 30
2 32 0.11 Practical example D04 Balance Balance 6.50 1.50 1.50
35.00 1.00 21 2 23 0.10 Practical example D15 Balance Balance 8.00
1.50 1.50 35.00 1.00 23 2 25 0.12 Practical example D16 Balance
Balance 10.00 1.50 1.50 35.00 1.00 66 4 70 0.23 Comparative
example
[0116] According to Table D-3, the influence of the amount of Co in
the iron alloy powder was investigated. In the sample No. D12 in
which the amount of Co was less than 3%, the wear amount of the
valve sheet and the corrosion loss were large because strength and
heat resistance of the Fe matrix were not sufficiently improved by
Co. In the sample No. D13 in which the amount of Co in the iron
alloy powder was 3%, the wear amount of the valve sheet was
remarkably decreased because the Fe matrix was strengthened by Co
and heat resistance was improved by Co, and the corrosion loss was
decreased because corrosion resistance of the Fe matrix was
improved. When the amount of Co in the iron alloy powder was not
more than 6.5%, the wear amount of the valve sheet and the
corrosion loss were decreased according to the increase in the
amount of Co in the iron alloy powder. In the sample No. D15 in
which the amount of Co in the iron alloy powder was 8%,
compressibility of the raw powder was decreased by the increase in
the hardness of the iron alloy powder, whereby the density of the
green compact was decreased. As a result, the density of the
sintered compact was decreased, whereby the wear amount of the
valve sheet and the corrosion loss were slightly increased, but
these were at low levels. On the other hand, in the sample No. D16
in which the amount of Co in the iron alloy powder was greater than
8%, the influence of the increase in the hardness of the iron alloy
powder was remarkable, and the density of the sintered compact was
remarkably decreased, whereby the wear amount of the valve sheet
and the corrosion loss were remarkably increased. According to the
above results, when the amount of Co in the iron alloy powder was 3
to 8%, the wear amount of the valve sheet was small and the
corrosion loss was reduced.
Example D-4
[0117] The iron alloy powder (Fe-6.5% Co-1.5% Ni-1.5% Mo powder)
used in the example D-1, the hard phase forming alloy powder
(Co-30% Cr-20% Mo-17% Fe-3% Si powder) used in the sample No. D04
in the example D-1, and a graphite powder were prepared. The ratio
of the graphite powder was changed as shown in Table D-4, and these
powders were added and mixed. Furthermore, 0.8 mass parts of zinc
stearate as a forming lubricant was added and mixed 100 mass parts
of the mixed powder, and a raw powder was mixed. The obtained raw
powder was compacted and sintered in the same way as in the example
A-1, and samples Nos. D17 to D22 were formed. The wear tests were
performed in the same way as in the example C-1 for these samples.
The results are shown in Table D-4 with the values of the sample
No. D04 in the example D-1.
TABLE-US-00022 TABLE D-4 Mixing ratio mass % Hard phase Evaluation
item forming Wear amount .mu.m Iron alloy alloy Graphite Valve
Sample No. powder powder powder sheet Valve Total Notes D17 Balance
35.00 0.30 121 2 123 Comparative example D18 Balance 35.00 0.50 55
2 57 Practical example D19 Balance 35.00 0.80 25 2 27 Practical
example C04 Balance 35.00 1.00 21 2 23 Practical example D20
Balance 35.00 1.20 25 3 28 Practical example D21 Balance 35.00 1.50
48 7 55 Practical example D22 Balance 35.00 1.80 90 41 131
Comparative example
[0118] According to Table D-4, the influence of the amount of the
graphite powder (the amount of C in the overall composition) was
investigated. In the sample No. D17 in which the amount of the
graphite powder was less than 0.5%, the wear amount of the valve
sheet was large because Fe matrix of the sintered alloy was not
sufficiently strengthened. In the sample No. D18 in which the
amount of the graphite powder was 0.5%, the wear amount of the
valve sheet was remarkably decreased because the Fe matrix of the
sintered alloy was strengthened. When the amount of the graphite
powder was not more than 1.0%, the wear amount of the valve sheet
was decreased according to the increase in the amount of the
graphite powder. In the sample in which the amount of the graphite
powder was 1.2 to 1.5%, the wear amount of the valve sheet was
increased and the wear amount of the valve was slightly increased
because the Fe matrix of the sintered alloy was hardened and
embrittled. In this case, the total of the wear amounts was not a
problem in practical use. On the other hand, in the sample No. D22
in which the amount of the graphite powder was greater than 1.5%,
this tendency was more remarkable, and therefore the wear amount of
the valve sheet was remarkably increased. Moreover, the wear amount
of the valve was also remarkably increased because the wear
particles of the valve sheet eroded the valve. According to the
above results, when the amount of the graphite powder (the amount
of C in the overall composition) was 0.5 to 1.5%, the wear amounts
of the valve sheet and the valve were small.
Example D-5
[0119] The iron alloy powder (Fe-6.5% Co-1.5% Ni-1.5% Mo powder)
used in the example D-1, a graphite powder, and a hard phase
forming alloy powder as shown in Table D-5 were prepared. The hard
phase forming alloy powder had a composition in which a ratio of Co
and Fe was different from that of the hard phase forming alloy
powder (Co-30% Cr-20% Mo-17% Fe-3% Si powder) used in the sample
No. D04 in the example D-1. The iron alloy powder, 35% of the hard
phase forming alloy powder and 1% of the graphite powder were added
and mixed. Furthermore, 0.8 mass parts of zinc stearate as a
forming lubricant was added and mixed with 100 mass parts of the
mixed powder, and a raw powder was obtained. The obtained raw
powder was compacted and sintered in the same way as in the example
A-1, and samples Nos. D23 to D28 were formed. The wear tests were
performed in the same way as in the example C-1 for these samples.
The results are shown in Table D-5 with the values of the sample
No. D04 in the example D-1.
TABLE-US-00023 TABLE D-5 Mixing ratio mass % Evaluation item Hard
phase forming alloy powder Wear amount .mu.m Sample Iron alloy
Compositions mass % Substitutional Graphite Valve No. powder Co Fe
Cr Mo Si ratio of Fe powder sheet Valve Total Notes D23 Balance
35.00 Balance 0.00 30.00 20.00 3.00 0.00 1.00 15 2 17 Practical
example D24 Balance 35.00 Balance 7.00 30.00 20.00 3.00 14.90 1.00
18 2 20 Practical example D04 Balance 35.00 Balance 17.00 30.00
20.00 3.00 36.20 1.00 21 2 23 Practical example D25 Balance 35.00
Balance 28.00 30.00 20.00 3.00 59.60 1.00 24 2 26 Practical example
D26 Balance 35.00 Balance 37.50 30.00 20.00 3.00 79.80 1.00 40 3 43
Practical example D27 Balance 35.00 Balance 42.00 30.00 20.00 3.00
89.40 1.00 71 4 75 Practical example D28 Balance 35.00 Balance
47.00 30.00 20.00 3.00 100.00 1.00 102 9 111 Comparative
example
[0120] According to Table D-5, when Co in the hard phase forming
alloy powder was substituted by Fe, the influence of the
substitutional ratio of Fe was investigated. In the sample No. D23
in which Co in the hard phase forming alloy powder was not
substituted by Fe, the wear amounts were the least among the above
examples D and wear resistance was good. When Co in the hard phase
forming alloy powder was substituted by Fe and the substitutional
ratio of Fe was increased, the wear amounts were increased. In this
case, when the substitutional ratio of Fe was not more than 80%
(samples Nos. D04 and D24 to D26), the wear amounts were not a
problem in practical use. However, in the samples Nos. D27 and D28
in which the substitutional ratio of Fe was more than 80%, the wear
amounts were remarkably increased, because the effect of Co was
insufficient. According to the above results, although Co in the
hard phase forming alloy powder could be substituted by Fe, the
substitutional ratio of Fe should be not more than 80%. The
substitutional ratio of Fe is preferably not more than 60%.
Example D-6
[0121] The iron alloy powder (Fe-6.5% Co-1.5% Ni-1.5% Mo powder)
used in the example D-1, a graphite powder, and a hard phase
forming alloy powder as shown in Table D-6 were prepared. The hard
phase forming alloy powder was formed by adding different amount of
Mn in the hard phase forming alloy powder (Co-30% Cr-20% Mo-17%
Fe-3% Si powder) used in the sample No. D04 in the example D-1. The
iron alloy powder, 35% of the hard phase forming alloy powder and
1% of the graphite powder were added and mixed. Furthermore, 0.8
mass parts of zinc stearate as a forming lubricant was added and
mixed with 100 mass parts of the mixed powder, and a raw powder was
obtained. The obtained raw powder was compacted and sintered in the
same way as in the example A-1, and samples Nos. D29 to D32 were
formed. The wear tests were performed in the same way as in the
example C-1 for these samples. The results are shown in Table D-6
with the values of the sample No. D04 in the example D-1.
TABLE-US-00024 TABLE D-6 Mixing ratio mass % Evaluation item Hard
phase forming alloy powder Wear amount .mu.m Sample Iron alloy
Compositions mass % Graphite Valve No. powder Co Fe Cr Mo Si Mn
powder sheet Valve Total Notes D04 Balance 35.00 Balance 17.00
30.00 20.00 3.00 -- 1.00 21 2 23 Practical example D29 Balance
35.00 Balance 17.00 30.00 20.00 3.00 1.00 1.00 19 2 21 Practical
example D30 Balance 35.00 Balance 17.00 30.00 20.00 3.00 3.00 1.00
16 3 19 Practical example D31 Balance 35.00 Balance 17.00 30.00
20.00 3.00 5.00 1.00 20 9 29 Practical example D32 Balance 35.00
Balance 17.00 30.00 20.00 3.00 7.00 1.00 38 45 83 Comparative
example
[0122] According to Table D-6, the effect of Mn added in the hard
phase forming alloy powder (the hard phase) was investigated. In
the samples Nos. D29 to D31 in which the amount of Mn in the hard
phase forming alloy powder was not more than 5%, the alloy matrix
of the hard phase was strengthened by Mn, whereby the wear amounts
of valve sheets were less than that of the sample No. D04 in which
Mn in the hard phase forming alloy powder was not added. On the
other hand, the wear amounts of the valves were slightly increased
according to the increase in the amount of Mn, because the hard
phase was strengthened. In the sample No. D32 in which the amount
of Mn in the hard phase forming alloy powder was greater than 5%,
the hard phase forming alloy powder was hardened, and
compressibility of the raw powder was remarkably decreased, whereby
the wear amount of the valve sheet was remarkably increased.
Moreover, the wear amount of the valve was also remarkably
increased because the wear particles of the valve sheet eroded the
valve. According to the above results, although wear resistance
could be further improved by adding Mn in the hard phase forming
alloy powder, the amount of Mn in the hard phase forming alloy
powder should be not more than 5%.
Example D-7
[0123] The iron alloy powder (Fe-6.5% Co-1.5% Ni-1.5% Mo powder)
used in the example D-1, the hard phase forming alloy powder
(Co-30% Cr-20% Mo-17% Fe-3% Si powder) used in the sample No. D04
in the example D-1, a graphite powder, and a nickel powder were
prepared. The iron alloy powder, 35% of the hard phase forming
alloy powder, 1% of the graphite powder, and a ratio shown in Table
D-7 of the nickel powder were added and mixed. Furthermore, 0.8
mass parts of zinc stearate as a forming lubricant was added and
mixed with 100 mass parts of the mixed powder, and a raw powder was
obtained. The obtained raw powder was compacted and sintered in the
same way as in the example A-1, and samples Nos. D33 to D39 were
formed. The wear tests were performed in the same way as in the
example C-1 for these samples. The results are shown in Table D-7
with the values of the sample No. D04 in the example D-1.
TABLE-US-00025 TABLE D-7 Mixing ratio mass % Hard phase Evaluation
item forming Wear amount .mu.m Sample Iron alloy alloy Graphite
Nickel Valve No. powder powder powder powder sheet Valve Total
Notes D04 Balance 35.00 1.00 0.00 21 2 23 Practical example D33
Balance 35.00 1.00 0.10 20 2 22 Practical example D34 Balance 35.00
1.00 1.00 18 2 20 Practical example D35 Balance 35.00 1.00 2.00 16
2 18 Practical example D36 Balance 35.00 1.00 3.00 17 2 19
Practical example D37 Balance 35.00 1.00 4.00 18 2 20 Practical
example D38 Balance 35.00 1.00 5.00 20 3 23 Practical example D39
Balance 35.00 1.00 7.00 49 8 57 Comparative example
[0124] According to Table D-7, compared with the sample No. D04 in
which the nickel powder was not added to the raw powder and Ni was
not added in the matrix, in the samples Nos. D33 to D38 in which
the nickel powder was added at not more than 5%, the wear amount of
the valve sheet was decreased and the total of the wear amounts was
decreased. In the sample No. D39 in which the amount of the nickel
powder was greater than 5%, a large amount of Ni-rich austenite
having low wear resistance was formed and remained in the matrix,
whereby wear resistance of the valve sheet was decreased and the
wear amount of the valve sheet was increased. Moreover, the amount
of the hard martensite was increased, and the erosion of the valve
(the mating material) was increased, whereby the wear amount of the
valve was increased and the total of the wear amounts was
remarkably increased. Accordingly, although wear resistance was
improved by adding the nickel powder, the amount of the nickel
powder should be not more than 5.0%.
Example E
Fe--Ni--Mo--C Alloy Matrix
Example E-1
[0125] An iron alloy powder consisting of 2% of Ni, 1% of Mo, 0.5%
of Cr, 0.3% of Mn, and the balance of Fe and inevitable impurities,
a hard phase forming alloy powder shown in Table E-1, and a
graphite powder were prepared. The iron alloy powder, 35% of the
hard phase forming alloy powder, and 1% of the graphite powder were
added and mixed. Furthermore, 0.8 mass parts of zinc stearate as a
forming lubricant was added and mixed with 100 mass parts of the
mixed powder, and a raw powder was obtained. The obtained raw
powder was compacted and sintered in the same way as in the example
A-1, and samples Nos. E01 to E06 were formed. The simple wear tests
and the corrosion tests were performed in the same way as in the
example C-1 for these samples. The results of these tests are also
shown in Table E-1.
TABLE-US-00026 TABLE E-1 Mixing ratio mass % Evaluation item Hard
phase forming alloy powder Wear amount .mu.m Corrosion Sample Iron
alloy Compositions mass % Graphite Valve loss No. powder Co Fe Cr
Mo Si powder sheet Valve Total mg/cm.sup.2 Notes E01 Balance 35.00
Balance 42.00 5.00 20.00 3.00 1.00 92 4 96 0.31 Comparative example
E02 Balance 35.00 Balance 37.00 10.00 20.00 3.00 1.00 55 4 59 0.15
Practical example E03 Balance 35.00 Balance 27.00 20.00 20.00 3.00
1.00 37 4 41 0.14 Practical example E04 Balance 35.00 Balance 17.00
30.00 20.00 3.00 1.00 27 4 31 0.11 Practical example E05 Balance
35.00 Balance 7.00 40.00 20.00 3.00 1.00 42 7 49 0.15 Practical
example E06 Balance 35.00 Balance 2.00 45.00 20.00 3.00 1.00 79 24
103 0.32 Comparative example
[0126] According to Table E-1, the influence of the amount of Cr in
the hard phase forming alloy powder (the amount of Cr in the hard
phase) was investigated. In the sample No. E01, the amount of Cr in
the hard phase forming alloy powder was insufficient, whereby the
matrix of sintered alloy was not sufficiently strengthened, and the
wear amount of the valve sheet was large. Moreover, since the
amount of Cr was insufficient, corrosion resistance was
insufficient, and the corrosion loss was also large. In the sample
No. E02 in which the amount of Cr in the hard phase forming alloy
powder was 10%, the wear amount of the valve sheet was remarkably
decreased because the matrix was strengthened by Cr. Moreover, the
corrosion loss was reduced because corrosion resistance was
improved by Cr. When the amount of Cr in the hard phase forming
alloy powder was not more than 30%, the wear amounts of the valve
sheets were low values and the corrosion losses were reduced
according to the increase in the amount of Cr. In the sample No.
E05 in which the amount of Cr in the hard phase forming alloy
powder was 40%, the hardness of the hard phase forming alloy powder
was increased by the increase in the amount of Cr in the hard phase
forming alloy powder, whereby compressibility of the raw powder was
decreased, and the density of the green compact was decreased. As a
result, the density of the sintered compact was decreased, whereby
the wear amount of the valve sheet and the corrosion loss were
increased, but these values were sufficiently small. Moreover, the
wear amount of the valve was also increased because the wear
particles of the valve sheet eroded the valve, but this value was
small. However, in the sample No. E06 in which the amount of Cr in
the hard phase forming alloy powder was greater than 40%, this
tendency was more remarkable, and therefore the total of the wear
amounts and the corrosion loss were remarkably increased. According
to the above results, when the amount of Cr in the hard phase
forming alloy powder was 10 to 40%, the wear amounts of the valve
sheet and the valve were small and the corrosion losses of the
sintered alloys were small.
Example E-2
[0127] The iron alloy powder (Fe-2% Ni-1% Mo-0.5% Cr-0.3% Mn
powder) used in the example E-1, the hard phase forming alloy
powder (Co-30% Cr-20% Mo-17% Fe-3% Si powder) used in the sample
No. E04 in the example E-1, and a graphite powder were prepared.
The ratio of the hard phase forming alloy powder was changed as
shown in Table E-2, and these powders were added and mixed.
Furthermore, 0.8 mass parts of zinc stearate as a forming lubricant
was added and mixed with 100 mass parts of the mixed powder, and a
raw powder was obtained. The obtained raw powder was compacted and
sintered in the same way as in the example A-1, and samples Nos.
E07 to E11 were formed. The wear tests and the corrosion tests were
performed in the same way as in the example C-1 for these samples.
The results are shown in Table E-2 with the values of the sample
No. E04 in the example E-1.
TABLE-US-00027 TABLE E-2 Mixing ratio mass % Hard phase Evaluation
item forming Wear amount .mu.m Corrosion Sample Iron alloy alloy
Graphite Valve loss No. powder powder powder sheet Valve Total
mg/cm.sup.2 Notes E07 Balance 5.00 1.00 110 2 112 0.51 Comparative
example E08 Balance 15.00 1.00 53 3 56 0.26 Practical example E09
Balance 25.00 1.00 32 3 35 0.15 Practical example E10 Balance 35.00
1.00 27 4 31 0.11 Practical example E11 Balance 45.00 1.00 45 6 51
0.18 Practical example E12 Balance 55.00 1.00 86 45 131 0.45
Comparative example
[0128] According to Table E-2, the influence of the amount of the
hard phase forming alloy powder (the amount of the hard phase
dispersed in the matrix) was investigated. In the sample No. E07 in
which the amount of the hard phase forming alloy powder was less
than 15%, the wear amount of the valve sheet was large because the
amount of the hard phase was insufficient and the plastic flow of
the matrix could not be prevented. Moreover, the hard phase was
insufficient, and Cr was not sufficiently dispersed from the hard
phase to the matrix, whereby the corrosion loss was large. In the
sample No. E08 in which the amount of the hard phase forming alloy
powder was 15%, the wear amount of the valve sheet was remarkably
decreased and the corrosion loss was decreased because wear
resistance and corrosion resistance of the matrix of the sintered
alloy are improved by the hard phase. When the amount of the hard
phase forming alloy powder was not more than 35%, the wear amount
of the valve sheet and the corrosion loss were decreased according
to the increase in the amount of the hard phase forming alloy
powder. In the sample No. E10 in which the amount of the hard phase
forming alloy powder was 45%, compressibility of the raw powder was
decreased by the increase in the amount of the hard phase forming
alloy powder, whereby the wear amount of the valve sheet and the
corrosion loss were slightly increased, but these were at low
levels. On the other hand, in the sample No. E11 in which the
amount of the hard phase forming alloy powder was greater than 45%,
the influence of the decrease of compressibility was remarkable,
whereby the wear amount of the valve sheet was remarkably increased
and the corrosion loss was increased. Moreover, the wear amount of
the valve was also remarkably increased because the wear particles
of the valve sheet eroded the valve. According to the above
results, when the amount of the hard phase forming alloy powder
(the amount of the hard phase dispersed in the matrix) was 15 to
45%, the wear amounts of the valve sheet and the valve were
small.
Example E-3
[0129] An iron alloy powder having a composition shown in Table
E-3, the hard phase forming alloy powder (Co-30% Cr-20% Mo-17%
Fe-3% Si powder) used in the sample No. E04 in the example E-1, and
a graphite powder were prepared. The iron alloy powder, 35% of the
hard phase forming alloy powder and 1% of the graphite powder were
added and mixed. Furthermore, 0.8 mass parts of zinc stearate as a
forming lubricant was added and mixed with 100 mass parts of the
mixed powder, and a raw powder was obtained. The obtained raw
powder was compacted and sintered in the same way as in the example
A-1, and samples Nos. E12 to E20 were formed. The wear tests and
the corrosion tests were performed in the same way as in the
example C-1 for these samples. The results are shown in Table E-3
with the values of the sample No. E04 in the example E-1.
TABLE-US-00028 TABLE E-3 Mixing ratio mass % Hard phase Evaluation
item Iron alloy powder forming Wear amount .mu.m Sample
Compositions mass % alloy Graphite Valve No. Fe Ni Cr Mo Mn powder
powder sheet Valve Total Notes E12 Balance Balance 0.00 0.50 1.00
0.30 35.00 1.00 85 3 88 Comparative example E13 Balance Balance
1.00 0.50 1.00 0.30 35.00 1.00 40 4 44 Practical example E04
Balance Balance 2.00 0.50 1.00 0.30 35.00 1.00 27 4 31 Practical
example E14 Balance Balance 3.00 0.50 1.00 0.30 35.00 1.00 33 5 38
Practical example E15 Balance Balance 5.00 0.50 1.00 0.30 35.00
1.00 59 13 72 Comparative example E16 Balance Balance 2.00 0.00
1.00 0.30 35.00 1.00 62 2 64 Comparative example E17 Balance
Balance 2.00 0.10 1.00 0.30 35.00 1.00 41 2 43 Practical example
E18 Balance Balance 2.00 0.30 1.00 0.30 35.00 1.00 31 3 34
Practical example E04 Balance Balance 2.00 0.50 1.00 0.30 35.00
1.00 27 4 31 Practical example E19 Balance Balance 2.00 1.00 1.00
0.30 35.00 1.00 35 5 40 Practical example E20 Balance Balance 2.00
1.50 1.00 0.30 35.00 1.00 67 14 81 Comparative example
[0130] According to samples Nos. E04 and E12 to E15 in Table E-3,
the influence of the amount of Ni in the iron alloy powder was
investigated. In the sample No. E12 in which Ni was not added in
the iron alloy powder, the wear amount of the valve sheet and the
corrosion loss were large because the Fe matrix of the sintered
alloy was not strengthened. In the samples Nos. E13, E04, and E14
in which the amount of Ni in the iron alloy powder was 1 to 3%,
strength and corrosion resistance of the Fe matrix were improved by
Ni, the wear amount of the valve sheet was remarkably decreased,
and the corrosion loss was decreased. In the sample No. E15 in
which the amount of Ni in the iron alloy powder was greater than
3%, compressibility of the raw powder was decreased by the increase
in the hardness of the iron alloy powder, whereby the density of
the compact was decreased. As a result, the density of the sintered
compact was decreased, whereby the wear amount of the valve sheet
and the corrosion loss were remarkably increased. According to the
above results, when the amount of Ni in the iron alloy powder was 1
to 3%, the wear amount of the valve sheet was small and the
corrosion loss was reduced.
[0131] According to samples Nos. E04 and E16 to E20 in Table E-3,
the influence of the amount of Cr in the iron alloy powder was
investigated. In the sample No. E16 in which Cr was not added in
the iron alloy powder, the wear amount of the valve sheet and the
corrosion loss were large because the Fe matrix of the sintered
alloy was not strengthened. However, in the samples Nos. E18, E04,
and E19 in which the amount of Cr in the iron alloy powder was 0.1
to 1%, strength and corrosion resistance of the Fe matrix were
improved by Cr, whereby the wear amount of the valve sheet was
remarkably decreased, and the corrosion loss was decreased. In the
sample No. E20 in which the amount of Cr in the iron alloy powder
was greater than 1%, compressibility of the raw powder was
decreased by the increase in the hardness of the iron alloy powder,
whereby the density of the green compact was decreased. As a
result, the density of the sintered compact was decreased, whereby
the wear amount of the valve sheet and the corrosion loss were
remarkably increased. According to the above results, when the
amount of Cr in the iron alloy powder was 0.1 to 1%, the wear
amount of the valve sheet was small and the corrosion loss was
reduced.
Example E-4
[0132] The iron alloy powder (Fe-2% Ni-1% Mo-0.5% Cr-0.3% Mn
powder) used in the example E-1, the hard phase forming alloy
powder (Co-30% Cr-20% Mo-17% Fe-3% Si powder) used in the sample
No. E04 in the example E-1, and a graphite powder were prepared.
The ratio of the graphite powder was changed as shown in Table E-4,
and these powders were added and mixed. Furthermore, 0.8 mass parts
of zinc stearate as a forming lubricant was added and mixed with
100 mass parts of the mixed powder, and a raw powder was obtained.
The obtained raw powder was compacted and sintered in the same way
as in the example A-1, and samples Nos. E21 to E26 were formed. The
wear tests were performed in the same way as in the example C-1 for
these samples. The results are shown in Table E-4 with the values
of the sample No. E04 in the example E-1.
TABLE-US-00029 TABLE E-4 Mixing ratio mass % Hard phase Evaluation
item Sam- Iron forming Wear amount .mu.m ple alloy alloy Graphite
Valve No. powder powder powder sheet Valve Total Notes E21 Balance
35.00 0.30 113 2 115 Comparative example E22 Balance 35.00 0.50 54
3 57 Practical example E23 Balance 35.00 0.80 32 4 36 Practical
example E04 Balance 35.00 1.00 27 4 31 Practical example E24
Balance 35.00 1.20 32 5 37 Practical example E25 Balance 35.00 1.50
51 10 61 Practical example E26 Balance 35.00 1.80 102 52 154
Comparative example
[0133] According to Table E-4, the influence of the amount of the
graphite powder (the amount of C in the overall composition) was
investigated. In the sample No. E21 in which the amount of the
graphite powder was less than 0.5%, the wear amount of the valve
sheet was large because the Fe matrix of the sintered alloy was not
sufficiently strengthened. In the sample No. E22 in which the
amount of the graphite powder was 0.5%, the wear amount of the
valve sheet was remarkably decreased because the Fe matrix of the
sintered alloy was strengthened. When the amount of the graphite
powder was not more than 1.0%, the wear amount of the valve sheet
was decreased according to the increase in the amount of the
graphite powder. In the samples in which the amount of the graphite
powder was 1.0 to 1.5%, the Fe matrix of the sintered alloy was
hardened and embrittled, whereby the wear amount of the valve sheet
was increased and the wear amount of the valve was slightly
increased. In this case, the total of the wear amounts was not a
problem in practical use. On the other hand, in the sample No. E26
in which the amount of the graphite powder was greater than 1.5%,
this tendency was more remarkable, and therefore the wear amount of
the valve sheet was remarkably increased. Moreover, the wear amount
of the valve was also remarkably increased because the wear
particles of the valve sheet eroded the valve. According to the
above results, when the amount of the graphite powder (the amount
of C in the overall composition) was 0.5 to 1.5%, the wear amounts
of the valve sheet and the valve were small.
Example E-5
[0134] The iron alloy powder (Fe-2% Ni-1% Mo-0.5% Cr-0.3% Mn
powder) used in the example E-1, a graphite powder, and a hard
phase forming alloy powder as shown in Table E-5 were prepared. The
hard phase forming alloy powder had a composition in which a ratio
of Co and Fe was different from that of the hard phase forming
alloy powder (Co-30% Cr-20% Mo-17% Fe-3% Si powder) used in the
sample No. E04 in the example E-1. The iron alloy powder, 35% of
the hard phase forming alloy powder, and 1% of the graphite powder
were added and mixed. Furthermore, 0.8 mass parts of zinc stearate
as a forming lubricant was added and mixed with 100 mass parts of
the mixed powder, and a raw powder was obtained. The obtained raw
powder was compacted and sintered in the same way as in the example
A-1, and samples Nos. E27 to E32 were formed. The wear tests were
performed in the same way as in the example C-1 for these samples.
The results are shown in Table E-5 with the values of the sample
No. E04 in the example E-1.
TABLE-US-00030 TABLE E-5 Mixing ratio mass % Evaluation item Hard
phase forming alloy powder Wear amount .mu.m Sample Iron alloy
Compositions mass % Substitutional Graphite Valve No. powder Co Fe
Cr Mo Si ratio of Fe powder sheet Valve Total Notes E27 Balance
35.00 Balance 0.00 30.00 20.00 3.00 0.00 1.00 19 3 22 Practical
example E28 Balance 35.00 Balance 7.00 30.00 20.00 3.00 14.90 1.00
23 3 26 Practical example E04 Balance 35.00 Balance 17.00 30.00
20.00 3.00 36.20 1.00 27 4 31 Practical example E29 Balance 35.00
Balance 28.00 30.00 20.00 3.00 59.60 1.00 31 4 35 Practical example
E30 Balance 35.00 Balance 37.50 30.00 20.00 3.00 79.80 1.00 49 4 53
Practical example E31 Balance 35.00 Balance 42.00 30.00 20.00 3.00
89.40 1.00 88 6 94 Practical example E32 Balance 35.00 Balance
47.00 30.00 20.00 3.00 100.00 1.00 129 12 141 Comparative
example
[0135] According to Table E-5, when Co in the hard phase forming
alloy powder was substituted by Fe, the influence of the
substitutional ratio of Fe was investigated. In the sample No. E27
in which Co in the hard phase forming alloy powder was not
substituted by Fe, the wear amounts were the least among the above
examples E and wear resistance was good. When Co in the hard phase
forming alloy powder was substituted by Fe and the substitutional
ratio of Fe was increased, the wear amounts were increased. In this
case, when the substitutional ratio of Fe was not more than 80%
(samples Nos. E04 and E28 to E30), the wear amounts were not a
problem in practical use. However, in the samples Nos. E31 and E32
in which the substitutional ratio of Fe was more than 80%, the wear
amounts were remarkably increased, because the effect of Co was
insufficient. According to the above results, although Co in the
hard phase forming alloy powder could be substituted by Fe, the
substitutional ratio of Fe should be not more than 80%.
Furthermore, the substitutional ratio of Fe was preferably not more
than 60%.
Example E-6
[0136] The iron alloy powder (Fe-2% Ni-1% Mo-0.5% Cr-0.3% Mn
powder) used in the example E-1, a graphite powder, and a hard
phase forming alloy powder as shown in Table E-6 were prepared. The
hard phase forming alloy powder was formed by adding different
amount of Mn in the hard phase forming alloy powder (Co-30% Cr-20%
Mo-17% Fe-3% Si powder) used in the sample No. E04 in the example
E-1. The iron alloy powder, 35% of the hard phase forming alloy
powder, and 1% of the graphite powder were added and mixed.
Furthermore, 0.8 mass parts of zinc stearate as a forming lubricant
was added and mixed with 100 mass parts of the mixed powder, and a
raw powder was obtained. The obtained raw powder was compacted and
sintered in the same way as in the example A-1, and samples Nos.
E33 to E36 were formed. The wear tests were performed in the same
way as in the example C-1 for these samples. The results are shown
in Table E-6 with the values of the sample No. E04 in the example
E-1.
TABLE-US-00031 TABLE E-6 Mixing ratio mass % Evaluation item Hard
phase forming alloy powder Wear amount .mu.m Sample Iron alloy
Composition mass % Graphite Valve No. powder Co Fe Cr Mo Si Mn
powder sheet Valve Total Notes E04 Balance 35.00 Balance 17.00
30.00 20.00 3.00 -- 1.00 27 4 31 Practical example E33 Balance
35.00 Balance 17.00 30.00 20.00 3.00 1.00 1.00 24 4 28 Practical
example E34 Balance 35.00 Balance 17.00 30.00 20.00 3.00 3.00 1.00
22 5 27 Practical example E35 Balance 35.00 Balance 17.00 30.00
20.00 3.00 5.00 1.00 24 12 36 Practical example E36 Balance 35.00
Balance 17.00 30.00 20.00 3.00 7.00 1.00 47 50 97 Comparative
example
[0137] According to Table E-6, the effect of Mn in the hard phase
forming alloy powder (the hard phase) was investigated. In the
samples Nos. D33 to D35 in which the amount of Mn in the hard phase
forming alloy powder was not more than 5%, the alloy matrix of the
hard phase was strengthened by Mn, whereby the wear amounts of the
valve sheets were less than that of the sample No. E04 in which Mn
was not added in the hard phase forming alloy powder. On the other
hand, the wear amounts of the valves were slightly increased
according to the increase in the amount of Mn, because the hard
phase was strengthened. In the sample No. E36 in which the amount
of Mn in the hard phase forming alloy powder was greater than 5%,
the hard phase forming alloy powder was hardened, and
compressibility of the raw powder was remarkably decreased, whereby
the wear amount of the valve sheet was remarkably increased.
Moreover, the wear amount of the valve was also remarkably
increased because the wear particles of the valve sheet eroded the
valve. According to the above results, although wear resistance
could be further improved by adding Mn in the hard phase forming
alloy powder, the amount of Mn in the hard phase forming alloy
powder should be not more than 5%.
Example E-7
[0138] The iron alloy powder (Fe-2% Ni-1% Mo-0.5% Cr-0.3% Mn
powder) used in the example E-1, the hard phase forming alloy
powder (Co-30% Cr-20% Mo-17% Fe-3% Si powder) used in the sample
No. E04 in the example E-1, a graphite powder, and a nickel powder
were prepared. The iron alloy powder, 35% of the hard phase forming
alloy powder, 1% of the graphite powder, and a ratio shown in Table
E-7 of the nickel powder were added and mixed. Furthermore, 0.8
mass parts of zinc stearate as a forming lubricant was added and
mixed with 100 mass parts of the mixed powder, and a raw powder was
obtained. The obtained raw powder was compacted and sintered in the
same way as in the example A-1, and samples Nos. E37 to E43 were
formed. The wear tests were performed in the same way as in the
example C-1 for these samples. The results are shown in Table E-7
with the values of the sample No. E04 in the example E-1.
TABLE-US-00032 TABLE E-7 Mixing ratio mass % Evaluation item Hard
phase Wear amount .mu.m Sample Iron alloy forming Graphite Nickel
Valve No. powder alloy powder powder powder sheet Valve Total Notes
E04 Balance 35.00 1.00 0.00 27 4 31 Practical example E37 Balance
35.00 1.00 0.10 25 4 29 Practical example E38 Balance 35.00 1.00
1.00 24 4 28 Practical example E39 Balance 35.00 1.00 2.00 22 4 26
Practical example E40 Balance 35.00 1.00 3.00 21 4 25 Practical
example E41 Balance 35.00 1.00 4.00 23 5 28 Practical example E42
Balance 35.00 1.00 5.00 25 6 31 Practical example E43 Balance 35.00
1.00 7.00 75 10 85 Comparative example
[0139] According to Table E-7, compared with the sample No. E04 in
which the nickel powder was not added to the raw powder and Ni was
not added in the matrix, in the samples Nos. E37 to E42 in which
the nickel powder was added at not more than 5%, the wear amount of
the valve sheet was decreased and the total of the wear amounts
were decreased. In the sample No. E43 in which the amount of the
nickel powder was greater than 5%, a large amount of Ni-rich
austenite having low wear resistance was formed and remained in the
matrix, whereby wear resistance of the valve sheet was decreased
and the wear amount of the valve sheet was increased. Moreover, the
amount of hard martensite was increased, and the erosion of the
valve (the mating material) was increased, whereby the wear amount
of the valve was increased and the total of the wear amount was
remarkably increased. Accordingly, although wear resistance was
improved by adding the nickel powder, the amount of the nickel
powder should be not more than 5.0%.
Example E-8
[0140] The iron alloy powder (Fe-2% Ni-1% Mo-0.5% Cr-0.3% Mn
powder) used in the example E-1, the hard phase forming alloy
powder (Co-30% Cr-20% Mo-17% Fe-3% Si powder) used in the sample
No. E04 in the example E-1, a graphite powder, and a copper powder
were prepared. The iron alloy powder, 35% of the hard phase forming
alloy powder, 1% of the graphite powder, and a ratio shown in Table
E-8 of the copper powder were added and mixed. Furthermore, 0.8
mass parts of zinc stearate as a forming lubricant was added and
mixed with 100 mass parts of the mixed powder, and a raw powder was
obtained. The obtained raw powder was compacted and sintered in the
same way as in the example A-1, and samples Nos. E44 to E50 were
formed. The wear tests were performed in the same way as in the
example C-1 for these samples. The results are shown in Table E-8
with the values of the sample No. E04 in the example E-1.
TABLE-US-00033 TABLE E-8 Mixing ratio mass % Evaluation item Hard
phase Wear amount .mu.m Sample Iron alloy forming Graphite Copper
Valve No. powder alloy powder powder powder sheet Valve Total Notes
E04 Balance 35.00 1.00 0.00 27 4 31 Practical example E44 Balance
35.00 1.00 0.10 25 4 29 Practical example E45 Balance 35.00 1.00
1.00 23 5 28 Practical example E46 Balance 35.00 1.00 2.00 22 5 27
Practical example E47 Balance 35.00 1.00 3.00 22 5 27 Practical
example E48 Balance 35.00 1.00 4.00 23 6 29 Practical example E49
Balance 35.00 1.00 5.00 24 7 31 Practical example E50 Balance 35.00
1.00 7.00 53 46 99 Comparative example
[0141] According to Table E-8, compared with the sample No. E04 in
which the copper powder was not added to the raw powder and Cu was
not added in the matrix, in the samples Nos. E44 to E49 in which
the copper powder was added at not more than 5%, the wear amount of
the valve sheet was decreased and the total of the wear amounts was
decreased. In the sample No. E50 in which the amount of the copper
powder was greater than 5%, a part of Cu was not solid-solved in
the matrix, and Cu phase was dispersed in the matrix, whereby the
strength of the matrix was decreased, and the wear amount of the
valve sheet was increased. Moreover, the amount of hard martensite
was increased, and the erosion of valve (the mating material) was
increased, whereby the wear amount of the valve was increased and
the total of the wear amounts was remarkably increased.
Accordingly, although wear resistance was improved by adding the
copper powder, the amount of the copper powder should be not more
than 5.0%.
Example F
Fe--Mo--C Alloy Matrix
Example F-1
[0142] An iron alloy powder consisting of 3% of Mo and the balance
of Fe and inevitable impurities, a hard phase forming alloy powder
shown in Table F-1, and a graphite powder were prepared. The iron
alloy powder, 35% of the hard phase forming alloy powder, and 1% of
the graphite powder were added and mixed. Furthermore, 0.8 mass
parts of zinc stearate as a forming lubricant was added and mixed
with 100 mass parts of the mixed powder, and a raw powder was
obtained. The obtained raw powder was compacted and sintered in the
same way as in the example A-1, and samples Nos. F01 to F06 were
formed. The simple wear tests and the corrosion tests were
performed in the same way as in the example C-1 for these samples.
The results of these tests are also shown in Table F-1.
TABLE-US-00034 TABLE F-1 Mixing ratio mass % Evaluation item Hard
phase forming alloy powder Wear amount .mu.m Corrosion Sample Iron
alloy Composition mass % Graphite Valve loss No. powder Co Fe Cr Mo
Si powder sheet Valve Total mg/cm.sup.2 Notes F01 Balance 35.00
Balance 42.00 5.00 20.00 3.00 1.00 63 5 68 0.28 Comparative example
F02 Balance 35.00 Balance 37.00 10.00 20.00 3.00 1.00 37 5 42 0.14
Practical example F03 Balance 35.00 Balance 27.00 20.00 20.00 3.00
1.00 25 5 30 0.11 Practical example F04 Balance 35.00 Balance 17.00
30.00 20.00 3.00 1.00 18 5 23 0.08 Practical example F05 Balance
35.00 Balance 7.00 40.00 20.00 3.00 1.00 28 7 35 0.14 Practical
example F06 Balance 35.00 Balance 2.00 45.00 20.00 3.00 1.00 55 26
81 0.20 Comparative example
[0143] According to Table F-1, the influence of the amount of Cr in
the hard phase forming alloy powder (the amount of Cr in the hard
phase) was investigated. In the sample No. F01, the amount of Cr in
the hard phase forming alloy powder was insufficient, whereby the
matrix of sintered alloy was not sufficiently strengthened, and the
wear amount of the valve sheet was large. Moreover, the amount of
Cr was insufficient, whereby corrosion resistance was insufficient,
and the corrosion loss was also large. In the sample No. F02 in
which the amount of Cr in the hard phase forming alloy powder was
10%, the wear amount of the valve sheet was remarkably decreased
because the matrix was strengthened by Cr. Moreover, the corrosion
loss was reduced because corrosion resistance was improved by Cr.
When the amount of Cr in the hard phase forming alloy powder was
not more than 30%, the wear amounts of the valve sheets were at low
levels and the corrosion losses were reduced according to the
increase in the amount of Cr. In the sample No. F05 in which the
amount of Cr in the hard phase forming alloy powder was 40%, the
hardness of the hard phase forming alloy powder was increased by
the increase in the amount of Cr in the hard phase forming alloy
powder, whereby compressibility of the raw powder was decreased,
and the density of the green compact was decreased. As a result,
the density of the sintered compact was decreased, whereby the wear
amount of the valve sheet and the corrosion loss was increased, but
these values were sufficiently small. Moreover, the wear particles
of the valve sheet eroded the valve, and the wear amount of the
valve was also increased, but this value was small. However, in the
sample No. F06 in which the amount of Cr in the hard phase forming
alloy powder was greater than 40%, this tendency was more
remarkable, and therefore the total of the wear amounts and the
corrosion loss were remarkably increased. According to the above
results, when the amount of Cr in the hard phase forming alloy
powder was 10 to 40%, the wear amounts of the valve sheet and the
valve were small and the corrosion losses of the sintered alloys
were small.
Example F-2
[0144] The iron alloy powder (Fe-3% Mo powder) used in the example
F-1, the hard phase forming alloy powder (Co-30% Cr-20% Mo-17%
Fe-3% Si powder) used in the sample No. F04 in the example F-1, and
a graphite powder were prepared. The ratio of the hard phase
forming alloy powder was changed as shown in Table F-2, and these
powders were added and mixed. Furthermore, 0.8 mass parts of zinc
stearate as a forming lubricant was added and mixed with 100 mass
parts of the mixed powder, and a raw powder was obtained. The
obtained raw powder was compacted and sintered in the same way as
in the example A-1, and samples Nos. F07 to F11 were formed. The
wear tests and the corrosion tests were performed in the same way
as in the example C-1 for these samples. The results are shown in
Table F-2 with the values of the sample No. F04 in the example
F-1.
TABLE-US-00035 TABLE F-2 Mixing ratio mass % Evaluation item Hard
phase Wear amount .mu.m Corrosion Sample Iron alloy forming
Graphite Valve loss No. powder alloy powder powder sheet Valve
Total mg/cm.sup.2 Notes F07 Balance 5.00 1.00 72 2 74 0.46
Comparative example F08 Balance 15.00 1.00 35 4 39 0.18 Practical
example F09 Balance 25.00 1.00 21 5 26 0.13 Practical example F04
Balance 35.00 1.00 18 5 23 0.08 Practical example F10 Balance 45.00
1.00 29 7 36 0.15 Practical example F11 Balance 55.00 1.00 54 40 94
0.26 Comparative example
[0145] According to Table F-2, the influence of the amount of the
hard phase forming alloy powder (the amount of the hard phase
dispersed in the matrix) was investigated. In the sample No. F07 in
which the amount of the hard phase forming alloy powder was less
than 15%, the wear amount of the valve sheet was large because the
amount of the hard phase was insufficient and the plastic flow of
the matrix could not be prevented. Moreover, the hard phase was
insufficient, and Cr was not sufficiently dispersed from the hard
phase to the matrix, whereby the corrosion loss was large. In the
sample No. F08 in which the amount of the hard phase forming alloy
powder was 15%, the wear amount of the valve sheet was remarkably
decreased and the corrosion loss was decreased because the wear
resistance and corrosion resistance of the matrix of the sintered
alloy were improved by the hard phase. When the amount of the hard
phase forming alloy powder was not more than 35%, the wear amount
of the valve sheet and the corrosion loss were decreased according
to the increase in the amount of the hard phase forming alloy
powder. In the sample No. F10 in which the amount of the hard phase
forming alloy powder was 45%, compressibility of the raw powder was
decreased by the increase in the amount of the hard phase forming
alloy powder, whereby the wear amount of the valve sheet and the
corrosion loss were slightly increased, but these were at low
levels. On the other hand, in the sample No. F11 in which the
amount of the hard phase forming alloy powder was greater than 45%,
the influence of the decrease of compressibility was remarkable,
whereby the wear amount of the valve sheet was remarkably increased
and the corrosion loss was increased. Moreover, the wear amount of
the valve was also remarkably increased because the wear particles
of the valve sheet eroded the valve. According to the above
results, when the amount of the hard phase forming alloy powder
(the amount of the hard phase dispersed in the matrix) was 15 to
45%, the wear amounts of the valve sheet and the valve were
small.
Example F-3
[0146] An iron alloy powder as shown in Table F-3, a graphite
powder, and the hard phase forming alloy powder (Co-30% Cr-20%
Mo-17% Fe-3% Si powder) used in the sample No. F04 in the example
F-1 were prepared. In the iron alloy powder, the amount of Mo was
different from that of the iron alloy powder used in the example
F-1. The iron alloy powder, 35% of the hard phase forming alloy
powder, and 1% of the graphite powder were added and mixed.
Furthermore, 0.8 mass parts of zinc stearate as a forming lubricant
was added and mixed with 100 mass parts of the mixed powder, and a
raw powder was mixed. The obtained raw powder was compacted and
sintered in the same way as in the example A-1, and samples Nos.
F12 to F16 were formed. The wear tests and the corrosion tests were
performed in the same way as in the example C-1 for these samples.
The results are shown in Table F-3 with the values of the sample
No. F04 in the example F-1.
TABLE-US-00036 TABLE F-3 Mixing ratio mass % Evaluation item Iron
alloy powder Hard phase Wear amount .mu.m Corrosion Sample
compositions forming Graphite Valve loss No. Fe Mo alloy powder
powder sheet Valve Total mg/cm.sup.2 Notes F12 Balance Balance 0.00
35.00 1.00 61 4 65 0.25 Comparative example F13 Balance Balance
1.00 35.00 1.00 31 5 36 0.16 Practical example F04 Balance Balance
3.00 35.00 1.00 18 5 23 0.08 Practical example F14 Balance Balance
5.00 35.00 1.00 20 5 25 0.12 Practical example F15 Balance Balance
7.00 35.00 1.00 34 6 40 0.15 Practical example F16 Balance Balance
8.00 35.00 1.00 56 8 64 0.27 Comparative example
[0147] According to Table F-3, the influence of the amount of Mo in
the iron alloy powder was investigated. In the sample No. F12 in
which the amount of Mo was less than 1%, the wear amount of the
valve sheet and the corrosion loss were large because Fe matrix was
not strengthened by Mo. However, in the sample No. F13 in which the
amount of Mo in the iron alloy powder was 1%, the wear amount of
the valve sheet was remarkably decreased because the Fe matrix was
strengthened by Mo, and the corrosion loss was decreased because
the corrosion resistance of the Fe matrix was improved. When the
amount of Mo in the iron alloy powder was not more than 3%, the
wear amount of the valve sheet and the corrosion loss were
decreased according to the increase in the amount of Mo in the iron
alloy powder. In the samples Nos. F14 and F15 in which the amount
of Mo in the iron alloy powder was 5 to 7%, compressibility of the
raw powder was decreased by the increase in the hardness of the
iron alloy powder, whereby the density of the green compact was
decreased. As a result, the density of the sintered compact was
decreased, whereby the wear amount of valve sheet and the corrosion
loss were slightly increased, but these were low values. On the
other hand, in the sample No. F16 in which the amount of Mo in the
iron alloy powder was greater than 8%, the influence of the
increase in the hardness of the iron alloy powder was remarkable,
and the density of the sintered compact was remarkably decreased,
whereby the wear amount of the valve sheet and the corrosion loss
were remarkably increased. According to the above results, when the
amount of Mo in the iron alloy powder was 1 to 7%, the wear amount
of the valve sheet was small and the corrosion loss was
reduced.
Example F-4
[0148] The iron alloy powder (Fe-3% Mo powder) used in the example
F-1, the hard phase forming alloy powder (Co-30% Cr-20% Mo-17%
Fe-3% Si powder) used in the sample No. F04 in the example F-1, and
a graphite powder were prepared. The ratio of the graphite powder
was changed as shown in Table F-4, and these powders were added and
mixed. Furthermore, 0.8 mass parts of zinc stearate as a forming
lubricant was added and mixed with 100 mass parts of the mixed
powder, and a raw powder was obtained. The obtained raw powder was
compacted and sintered in the same way as in the example A-1, and
samples Nos. F17 to F22 were formed. The wear tests were performed
in the same way as in the example C-1 for these samples. The
results are shown in Table F-4 with the values of the sample No.
F04 in the example F-1.
TABLE-US-00037 TABLE F-4 Mixing ratio mass % Hard phase Evaluation
item Sam- Iron forming Wear amount .mu.m ple alloy alloy Graphite
Valve No. powder powder powder sheet Valve Total Notes F17 Balance
35.00 0.30 75 4 79 Comparative example F18 Balance 35.00 0.50 42 5
47 Practical example F19 Balance 35.00 0.80 21 5 26 Practical
example F04 Balance 35.00 1.00 18 5 23 Practical example F20
Balance 35.00 1.20 2 6 8 Practical example F21 Balance 35.00 1.50
41 10 51 Practical example F22 Balance 35.00 1.80 68 47 115
Comparative example
[0149] According to Table F-4, the influence of the amount of the
graphite powder (the amount of C in the overall composition) was
investigated. In the sample No. F17 in which the amount of the
graphite powder was less than 0.5%, the wear amount of the valve
sheet was large because Fe matrix of the sintered alloy was not
sufficiently strengthened. In the sample No. F18 in which the
amount of the graphite powder was 0.5%, the wear amount of the
valve sheet was remarkably decreased because the Fe matrix of the
sintered alloy was strengthened. When the amount of the graphite
powder was not more than 1.0%, the wear amount of the valve sheet
was decreased according to the increase in the amount of the
graphite powder. In the sample in which the amount of the graphite
powder was 1.2 to 1.5%, the wear amount of the valve sheet was
increased and the wear amount of the valve was slightly increased
because the Fe matrix of the sintered alloy was hardened and
embrittled. In this case, the total of the wear amounts was not a
problem in practical use. On the other hand, in the sample No. F22
in which the amount of the graphite powder was greater than 1.5%,
this tendency was more remarkable, and therefore the wear amount of
the valve sheet was remarkably increased. Moreover, the wear amount
of the valve was also remarkably increased because the wear
particles of the valve sheet eroded the valve. According to the
above results, when the amount of the graphite powder (the amount
of C in the overall composition) was 0.5 to 1.5%, the wear amounts
of the valve sheet and the valve were small.
Example F-5
[0150] The iron alloy powder (Fe-3% Mo powder) used in the example
F-1, a graphite powder, and a hard phase forming alloy powder as
shown in Table F-5 were prepared. The hard phase forming alloy
powder had a composition in which a ratio of Co and Fe was
different from that of the hard phase forming alloy powder (Co-30%
Cr-20% Mo-17% Fe-3% Si powder) used in the sample No. F04 in the
example F-1. The iron alloy powder, 35% of the hard phase forming
alloy powder, and 1% of the graphite powder were added and mixed.
Furthermore, 0.8 mass parts of zinc stearate as a forming lubricant
was added and mixed with 100 mass parts of the mixed powder, and a
raw powder was obtained. The obtained raw powder was compacted and
sintered in the same way as in the example A-1, and samples Nos.
F23 to F28 were formed. The wear tests were performed in the same
way as in the example C-1 for these samples. The results are shown
in Table F-5 with the values of the sample No. F04 in the example
F-1.
TABLE-US-00038 TABLE F-5 Mixing ratio mass % Evaluation item Hard
phase forming alloy powder Wear amount .mu.m Sample Iron alloy
Compositions mass % Subsitutional Graphite Valve No. powder Co Fe
Cr Mo Si ratio of Fe powder sheet Valve Total Notes F23 Balance
35.00 Balance 0.00 30.00 20.00 3.00 0.00 1.00 14 5 19 Practical
example F24 Balance 35.00 Balance 0.00 30.00 20.00 3.00 0.00 1.00
16 5 21 Practical example F04 Balance 35.00 Balance 0.00 30.00
20.00 3.00 0.00 1.00 18 5 23 Practical example F25 Balance 35.00
Balance 0.00 30.00 20.00 3.00 0.00 1.00 20 5 25 Practical example
F26 Balance 35.00 Balance 0.00 30.00 20.00 3.00 0.00 1.00 34 6 40
Practical example F27 Balance 35.00 Balance 0.00 30.00 20.00 3.00
0.00 1.00 61 7 68 Practical example F28 Balance 35.00 Balance 0.00
30.00 20.00 3.00 0.00 1.00 87 16 103 Comparative example
[0151] According to Table F-5, when Co in the hard phase forming
alloy powder was substituted by Fe, the influence of the
substitutional ratio of Fe was investigated. In the sample No. F23
in which Co in the hard phase forming alloy powder was not
substituted by Fe, the wear amounts were the lowest among the above
examples F and wear resistance was good. When Co in the hard phase
forming alloy powder was substituted by Fe and the substitutional
ratio of Fe was increased, the wear amounts were increased. In this
case, when the substitutional ratio of Fe was not more than 80%
(samples Nos. F04, F24 to F26), the wear amounts were not a problem
in practical use. In the samples Nos. F27 and F28 in which the
substitutional ratio of Fe was more than 80%, the wear amounts were
remarkably increased because the effect of Co was insufficient.
According to the above results, although Co in the hard phase
forming alloy powder could be substituted by Fe, the substitutional
ratio of Fe should be not more than 80%. Furthermore, the
substitutional ratio of Fe was preferably not more than 60%.
Example F-6
[0152] The iron alloy powder (Fe-3% Mo powder) used in the example
F-1, a graphite powder, and a hard phase forming alloy powder as
shown in Table F-6 were prepared. The hard phase forming alloy
powder was formed by adding different amount of Mn in the hard
phase forming alloy powder (Co-30% Cr-20% Mo-17% Fe-3% Si powder)
used in the sample No. F04 in the example F-1. The iron alloy
powder, 35% of the hard phase forming alloy powder, and 1% of the
graphite powder were added and mixed. Furthermore, 0.8 mass parts
of zinc stearate as a forming lubricant was added and mixed with
100 mass parts of the mixed powder, and a raw powder was obtained.
The obtained raw powder was compacted and sintered in the same way
as in the example A-1, and samples Nos. F29 to F32 were formed. The
wear tests were performed in the same way as in the example C-1 for
these samples. The results are shown in Table F-6 with the values
of the sample No. F04 in the example F-1.
TABLE-US-00039 TABLE F-6 Mixing ratio mass % Evaluation item Iron
Hard phase forming alloy powder Wear amount .mu.m Sample alloy
Compositions mass % Graphite Valve No. powder Co Fe Cr Mo Si Mn
powder sheet Valve Total Notes F04 Balance 35.00 Balance 17.00
30.00 20.00 3.00 -- 1.00 18 5 23 Practical example F29 Balance
35.00 Balance 17.00 30.00 20.00 3.00 1.00 1.00 16 5 21 Practical
example F30 Balance 35.00 Balance 17.00 30.00 20.00 3.00 3.00 1.00
14 7 21 Practical example F31 Balance 35.00 Balance 17.00 30.00
20.00 3.00 5.00 1.00 17 13 30 Practical example F32 Balance 35.00
Balance 17.00 30.00 20.00 3.00 7.00 1.00 33 51 84 Comparative
example
[0153] According to Table F-6, the effect of Mn in the hard phase
forming alloy powder (the hard phase) was investigated. In the
samples Nos. F29 to F31 in which the amount of Mn in the hard phase
forming alloy powder was not more than 5%, the alloy matrix of the
hard phase was strengthened by Mn, whereby the wear amounts of the
valve sheets were less than that of the sample No. F04 in which Mn
was not added in the hard phase forming alloy powder. On the other
hand, the wear amounts of the valves were slightly increased
according to the increase in the amount of Mn, because the hard
phase was strengthened. In the sample No. F32 in which the amount
of Mn in the hard phase forming alloy powder was greater than 5%,
the hard phase forming alloy powder was hardened, and
compressibility of the raw powder was remarkably decreased, whereby
the wear amount of the valve sheet was remarkably increased.
Moreover, the wear amount of the valve was also remarkably
increased because the wear particles of the valve sheet eroded the
valve. According to the above results, although wear resistance
could be further improved by adding Mn in the hard phase forming
alloy powder, the amount of Mn in the hard phase forming alloy
powder should not more than be 5%.
Example F-7
[0154] The iron alloy powder (Fe-3% Mo powder) used in the example
F-1, the hard phase forming alloy powder (Co-30% Cr-20% Mo-17%
Fe-3% Si powder) used in the sample No. F04 in the example F-1, a
graphite powder, and a nickel powder were prepared. The iron alloy
powder, 35% of the hard phase forming alloy powder, 1% of the
graphite powder, and a ratio shown in Table F-7 of the nickel
powder were added and mixed. Furthermore, 0.8 mass parts of zinc
stearate as a forming lubricant was added and mixed with 100 mass
parts of the mixed powder, and a raw powder was obtained. The
obtained raw powder was compacted and sintered in the same way as
in the example A-1, and samples Nos. F33 to F38 were formed. The
wear tests were performed in the same way as in the example C-1 for
these samples. The results are shown in Table F-7 with the values
of the sample No. F04 in the example F-1.
TABLE-US-00040 TABLE F-7 Mixing ratio mass % Evaluation item Iron
Hard phase Wear amount .mu.m Sample alloy forming alloy Graphite
Nickel Valve No. powder powder powder powder sheet Valve Total
Notes F04 Balance 35.00 1.00 0.00 18 5 23 Practical example F33
Balance 35.00 1.00 1.00 15 5 20 Practical example F34 Balance 35.00
1.00 2.00 14 5 19 Practical example F35 Balance 35.00 1.00 3.00 14
5 19 Practical example F36 Balance 35.00 1.00 4.00 16 6 22
Practical example F37 Balance 35.00 1.00 5.00 18 7 25 Practical
example F38 Balance 35.00 1.00 7.00 40 10 50 Comparative
example
[0155] According to Table F-7, compared with the sample No. F04 in
which the nickel powder was not added to the raw powder and Ni was
not added in the matrix, in the samples Nos. F33 to F37 in which
the nickel powder was added at not more than 5%, the wear amount of
the valve sheet was decreased and the total of the wear amounts was
decreased. In the sample No. F38 in which the amount of the nickel
powder was greater than 5%, a large amount of Ni-rich austenite
having low wear resistance was formed and remained in the matrix,
whereby wear resistance of the valve sheet was decreased and the
wear amount of the valve sheet was increased. Moreover, the amount
of hard martensite was increased, and the erosion of the valve (the
mating material) was increased, whereby the wear amount of the
valve was increased and the total of the wear amounts was
remarkably increased. Accordingly, although wear resistance was
improved by adding the nickel powder, the amount of the nickel
powder should be not more than 5.0%.
* * * * *