U.S. patent application number 10/690672 was filed with the patent office on 2004-04-29 for hard alloy and w-based composite carbide powder used as starting material.
This patent application is currently assigned to TOSHIBA TUNGALOY CO., LTD.. Invention is credited to Kobayashi, Masaki.
Application Number | 20040079191 10/690672 |
Document ID | / |
Family ID | 32110655 |
Filed Date | 2004-04-29 |
United States Patent
Application |
20040079191 |
Kind Code |
A1 |
Kobayashi, Masaki |
April 29, 2004 |
Hard alloy and W-based composite carbide powder used as starting
material
Abstract
There is disclosed a hard alloy which comprises 5 to 50% by
volume of a metallic binder phase comprising at least one element
selected from cobalt, nickel and iron as a main component, 0 to 40%
by volume of a cubic crystal compound comprising at least one
compound selected from a carbide, nitride and mutual solid solution
of a metal of Group IVB, VB or VIB of the Periodic Table, and the
reminder being hexagonal tungsten carbide and inevitable
impurities, wherein at least one specific element(s) selected from
the group consisting of titanium, zirconium, hafnium, vanadium,
niobium, tantalum, chromium, molybdenum, manganese and rhenium is
dissolved in the crystal of the hexagonal tungsten carbide as a
solid solution in an amount of 0.1 to 3.0% by weight based on the
amount of the tungsten carbide.
Inventors: |
Kobayashi, Masaki;
(Kanagawa, JP) |
Correspondence
Address: |
FOLEY AND LARDNER
SUITE 500
3000 K STREET NW
WASHINGTON
DC
20007
US
|
Assignee: |
TOSHIBA TUNGALOY CO., LTD.
|
Family ID: |
32110655 |
Appl. No.: |
10/690672 |
Filed: |
October 23, 2003 |
Current U.S.
Class: |
75/242 |
Current CPC
Class: |
C22C 29/02 20130101;
C22C 29/08 20130101 |
Class at
Publication: |
075/242 |
International
Class: |
C22C 029/02 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 24, 2002 |
JP |
2002-309855 |
Jan 30, 2003 |
JP |
2003-027343 |
Mar 3, 2003 |
JP |
2003-055291 |
Claims
1. A hard alloy which comprises 5 to 50% by volume of a metallic
binder phase comprising at least one element selected from cobalt,
nickel and iron as a main component, 0 to 40% by volume of a cubic
crystal compound comprising at least one compound selected from a
carbide, nitride and mutual solid solution of a metal of Group IVB,
VB or VIB of the Periodic Table, and the reminder being hexagonal
tungsten carbide and inevitable impurities, wherein at least one
specific element(s) selected from the group consisting of titanium,
zirconium, hafnium, vanadium, niobium, tantalum, chromium,
molybdenum, manganese and rhenium is dissolved in the crystal of
the hexagonal tungsten carbide as a solid solution in an amount of
0.1 to 3.0% by weight based on the amount of the tungsten
carbide.
2. The hard alloy according to claim 1, wherein the specific
element(s) is at least one selected from the group consisting of
titanium, zirconium, hafnium and vanadium.
3. The hard alloy according to claim 1, wherein the specific
element(s) is at least one selected from the group consisting of
niobium and tantalum.
4. The hard alloy according to claim 1, wherein the specific
element(s) is chromium.
5. The hard alloy according to claim 1, wherein the specific
element(s) is at least one selected from the group consisting of
molybdenum, manganese and rhenium.
6. The hard alloy according to claim 1, wherein the specific
element(s) is at least one selected from the group consisting of
titanium, zirconium, hafnium, vanadium, niobium and tantalum, and
the cubic crystal compound is contained in an amount of 1% by
volume or less.
7. The hard alloy according to claim 1, wherein the specific
element(s) is chromium, and chromium is contained in an amount of
0.1 to 10% by weight based on the total amount of the hard
alloy.
8. The hard alloy according to claim 1, wherein the specific
element(s) is at least one of manganese and rhenium, and the at
least one of manganese and rhenium is contained in an amount of 0.1
to 10% by weight based on the total amount of the hard alloy.
9. A tungsten-based complex carbide powder which comprises a
complex carbide powder containing tungsten, carbon, and at least
one specific element(s) selected from the group consisting of
titanium, zirconium, hafnium, vanadium, niobium, tantalum,
chromium, molybdenum, manganese and rhenium, wherein the complex
carbide powder contains 80% by volume or more of hexagonal tungsten
carbide, and the specific element(s) is dissolved in the crystal of
the hexagonal tungsten carbide in an amount of 0.1 to 3.0% by
weight.
10. The tungsten-based complex carbide powder according to claim 9,
wherein the powder contains particles of a cubic crystal compound
comprising tungsten, at least one of carbon and nitrogen, and at
least one selected from the group consisting of titanium,
zirconium, hafnium, vanadium, niobium and tantalum in an amount of
less than 20% by volume.
11. The tungsten-based complex carbide powder according to claim 9,
wherein the crystal of the hexagonal tungsten carbide has at least
one of a lattice constant of a axis of 0.2910 nm or longer and a
lattice constant of c axis of 0.2840 nm or longer.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a hard alloy to be used for
cutting tools, wear resistant tools, corrosion resistant and wear
resistant parts, etc., and particularly to a hard alloy in which
characteristics such as hardness, toughness, strength, wear
resistance, fracture resistance, plastic deformation resistance,
thermal crack resistance, antioxidation property, corrosion
resistance, etc., by adding specific element(s) to crystal of
hexagonal tungsten carbide which is a primary hard phase as a solid
solution, and to a W-based composite carbide powder which becomes a
starting material thereof.
[0003] 2. Prior Art
[0004] A hard alloy produced by mixing, in addition to WC and Co,
other powder of carbides such as TiC, TaC, VC, Cr.sub.3C.sub.2,
etc., subjecting to molding under pressure, and sintering under
heating has been used for various kinds of uses such as cutting
tools, wear resistant tools and parts. Also, by adjusting grain
size of WC, a Co amount, a kind and amount of a carbide to be
added, and the like, alloy characteristics such as hardness,
strength, toughness, heat resistance, oxidation resistance,
corrosion resistance, etc. required for the respective uses are
obtained. With regard to the other carbides to be added, for
example, TiC is added to steel cutting tools in which wear due to a
reaction or welding becomes a problem, TaC and/or ZrC is/are added
to hot-working mold or steel cutting tools in which plastic
deformation at high temperatures becomes a problem, VC and/or
Cr.sub.3C.sub.2 is/are added to a drill to which hardness and
strength are required as a grain growth inhibitor of WC, and
Cr.sub.3C.sub.2 and/or Mo.sub.2C is/are added to wear resistant
parts in which corrosion becomes a problem.
[0005] However, when one of the alloy characteristics is improved
by adding another carbides, there is a problem of antinomy wherein
the other alloy characteristics is lowered. For example, when TiC,
TaC, ZrC or VC is added, strength or toughness is markedly lowered
even when an amount thereof to be added is a little. Also,
Cr.sub.3C.sub.2 improves corrosion resistance or oxidation
resistance of a binder phase, but WC causes alkali corrosion or
preferential oxidation, so that its effect cannot sufficiently be
revealed.
[0006] As a measure of the above problems, it has been proposed
powder (for example, Japanese Provisional Patent Publication No.
Hei. 7-54001, Japanese PCT Provisional Patent Publication No.
2000-512688, Japanese Provisional Patent Publications No. Hei.
10-212165 and No. Hei. 11-236221) for manufacture of a hard alloy
to which other carbides are contained in WC powder, or a hard alloy
(for example, Japanese Provisional Patent Publications No. Hei.
10-298698, Hei. 11-6025, 2001-81526 and Hei. 10-45414) to which
other metals such as Cr, Mn, Re, etc. have been added. The former
is intended to prevent from lowering in strength, toughness, etc.,
while maintaining added effects of the other carbides by dispersing
the fine other carbides uniformly, and the latter is intended to
strengthen a binder phase by alloying other metals.
[0007] Among the prior art references which relate to powder for
producing a hard alloy containing other carbides, in Japanese
Provisional Patent Publication No. 7-54001, there is disclosed a
preparation method of fine complex carbide powder for preparation
of a tungsten carbide-based hard alloy in which mixed powder
comprising tungsten oxide, cobalt oxide, carbon, and further
carbides of V, Cr, Ta and/or Nb each having an average particle
diameter of about 1 .mu.m or lower is subjected to reduction
treatment and carbonization treatment both at 700 to 1200.degree.
C. In Japanese PCT Provisional Patent Publication No. 2000-512688,
there are disclosed powder comprising a transition metal carbide
and Group VIII metal and a process for preparing the same, which
comprises heating a precursor mixed powder which becomes a metal
selected from iron, cobalt and nickel and a transition metal
carbide of a metal selected from tungsten, titanium, tantalum,
molybdenum, zirconium, hafnium, vanadium, niobium and chromium at
1173 to 1773K (900 to 1500.degree. C.). In Japanese Provisional
Patent Publication No. 10-212165, there are disclosed a complex
carbide containing a tungsten carbide obtained by heating a mixed
powder comprising tungsten oxide and chromium oxide or metallic
chromium in hydrogen atmosphere at 700 to 1100.degree. C. to obtain
a solid solution or a intermetallic compound, mixing carbon powder
thereto, and carbonizing in hydrogen and vacuum at a temperature of
1300 to 1700.degree. C., and 0.5 to 2.0% by weight of metal
chromium based on the amount of the tungsten carbide, and a process
for preparing the same.
[0008] In complex carbide powders comprising tungsten carbide and
transition metal, transition metal carbide, iron-group metal and
the like described in these references, transition metal or its
carbide is uniformly and finely dispersed, so that when they are
used as a hard alloy, characteristics such as hardness, strength,
toughness, etc. can be improved but a heating temperature is low so
that an amount of the transition metal dissolved in tungsten
carbide is extremely little, whereby there is no improvement in
characteristics of the tungsten carbide itself. Thus, there is a
problem that an antinomy problem possessed by the hard alloy cannot
be solved.
[0009] Also, in Japanese Provisional Patent Publication No. Hei.
11-236221, there is disclosed a complex carbonitride material
comprising high melting point metals represented by the formula:
(M1m, M2n)(CxNy) wherein M1 and M2 are each metal element having a
high melting point different from each other among Nb, Mo, Ta and
W, m+n=1, 0.0<m<1, x+y.apprxeq.1, x.ltoreq.0.99 and
y.gtoreq.0.01, particularly to (W, Mo) (CN). This is to subject a
(W, Mo)C solid solution which has conventionally been well known to
nitriding synthesis by heating to 500 to 2000.degree. C. in a
nitrogen atmosphere at a pressure of 10 atm or higher. The (W, Mo)
(CN) powder disclosed in this publication has a wide range of an
amount of Mo as a solid solution and when it is employed for a hard
alloy, an effect of making particles fine by the nitrogen can be
expected. However, when an amount of Mo to be dissolved as a solid
solution is large, there are problems that decreases in hardness,
strength, wear resistance, plastic deformation property and
oxidation resistance are remarkable.
[0010] Among the prior art references relating to hard alloys to
which other metal(s) is/are added, in Japanese Provisional Patent
Publication No. Hei. 10-298698, there is disclosed a hard alloy
comprising 3 to 25% by weight of Co and Ni, 0.1 to 3% by weight of
chromium carbide based on the amount of Co and Ni, and the reminder
being tungsten carbide and inevitable impurities, and in Japanese
Provisional Patent Publication No. Hei. 11-6025, there are
disclosed a hard alloy comprising 3 to 25% by weight of Co and Ni
in total, 10 to 30% by weight of Cr in terms of chromium carbide
based on the amount of Co and Ni, and the reminder being tungsten
carbide and inevitable impurities, a coated alloy using the hard
alloy as a matrix and coated cutting tools.
[0011] In these chromium-containing hard alloys disclosed in both
of the publications, a Cr content, a Co/Ni ratio and grain size of
WC are limited to optimum ranges when they are used as cutting
tools, and Cr is dissolved in a metal binder phase, but is not
dissolved in WC as a solid solution, so that there is a problem
that an effect of Cr added cannot sufficiently be shown.
[0012] Also, in Japanese Provisional Patent Publication No.
2001-81526, there is disclosed an iron-based hard alloy comprising
a binder phase which comprises Fe containing 0.35 to 3.0% by weight
of C, 3.0 to 30.0% by weight of Mn, and 3.0 to 25.0% by weight of
Cr. In Japanese Provisional Patent Publication No. Hei. 10-45414,
there is disclosed a hard alloy using titanium compound powder as a
starting material, which powder has a coated film on the surface
thereof, comprising at least one substance selected from the group
consisting of Groups 4a, 5a, 6a metal except for titanium, their
carbide, nitride and carbonitride, and rhenium metal and iridium
metal.
[0013] The hard alloys containing Mn or Re metal disclosed in these
publications are to improve strength, toughness, corrosion
resistance, heat resistance, etc. of the hard alloy by adding these
metals as a solid solution to a metal binder phase, but these
metals are not dissolved in WC, so that an effect of adding Mn or
Re is little and if an amount of these metals to be added is large,
the metal binder phase becomes brittle whereby there are problems
that strength and toughness are lowered.
[0014] The present invention is to solve the above-mentioned
problems, and specifically, an object of the present invention is
to provide a hard alloy in which contradicting alloy
characteristics of the hard alloy are simultaneously improved by
dissolving specific element(s) such as Ti, Zr, V, Ta, Cr, Mn, etc.
into crystalline of WC as a solid solution whereby hardness,
toughness, oxidation resistance, corrosion resistance, etc. of the
WC itself are improved, and to provide W-based composite carbide
powder which becomes a starting material of the hard alloy.
SUMMARY OF THE INVENTION
[0015] The present inventors have studied to improve contradicting
characteristics of hard alloy at the same time for a long period of
time, and as a result, they have found that to improve
characteristics of WC itself is effective, various characteristics
of the alloy can be improved when specific element(s) is/are
dissolved in the crystal of WC, metals belonging to Group IVB (Ti,
Zr, Hf), VB (V, Nb, Ta) or VIB (Cr, Mo) of the Periodic Table
(except for W), and Mn and Re are the most effective as the
specific element(s), and WC dissolved the specific element(s)
therein can be obtained by subjecting a mixed powder of W, C and an
oxide of the specific element(s) to heat treatment, whereby they
have accomplished the present invention.
[0016] That is, the hard alloy of the present invention comprises 5
to 50% by volume of a metallic binder phase comprising at least one
element selected from cobalt, nickel and iron as a main component,
0 to 40% by volume of a cubic crystal compound comprising at least
one compound selected from a carbide, nitride and mutual solid
solution of a metal of Group IVB (Ti, Zr, Hf), VB (V, Nb, Ta), VIB
(Cr, Mo) of the Periodic Table, and the reminder being hexagonal
tungsten carbide and inevitable impurities, wherein at least one
specific element(s) selected from the group consisting of titanium,
zirconium, hafnium, vanadium, niobium, tantalum, chromium,
molybdenum, manganese and rhenium is dissolved in the crystal of
the hexagonal tungsten carbide as a solid solution in an amount of
0.1 to 3.0% by weight based on the amount of the tungsten
carbide.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0017] The hexagonal tungsten carbide in the hard alloy of the
present invention is a material in which at least one of the
specific element(s) selected from the group consisting of Ti, Zr,
Hf, V, Nb, Ta, Cr, Mo, Mn and Re is dissolved in the crystal of WC
as a solid solution. More specifically, there may be mentioned
(W,Ti)C, (W,Zr)C, (W,V)C, (W,Ta)C, (W,Cr)C, (W,Mo)C, (W,Re)C,
(W,Ti,Mo)C, (W,Zr,Cr)C, (W,V,Cr)C, (W,Nb,Mn)C and (W,Ta,Re)C, which
are a complex carbide having the same hexagonal structure as that
of WC. An amount of the specific element(s) to be dissolved in WC
as a solid solution is defined to be 0.1 to 3.0% by weight, since
if it is added in an amount of less than 0.1% by weight, improved
effects in hardness, toughness, oxidation resistance, corrosion
resistance, etc. are little, whereas Ti, Zr, Hf, V, Nb or Ta is
extremely difficult to be dissolved in WC in an amount exceeding
3.0% by weight, and even when Cr, Mo, Mn or Re can be dissolved in
WC in an amount exceeding 3.0% by weight, it accompanies with
lowering in hardness or oxidation resistance, or formation of
brittle sub-carbide material. The amount is preferably 0.3 to 2% by
weight.
[0018] Here, the specific element(s) dissolved in WC crystal has
slightly different characteristics to be provided to the hard alloy
depending on the kind thereof. For example, Ti, Zr, Hf and V
improve hardness, wear resistance, welding resistance, oxidation
resistance, etc., Nb and Ta improve toughness, fracture resistance,
heat resistance, etc., Cr improves toughness, oxidation resistance
and corrosion resistance, and Mo, Mn and Re improve hardness,
toughness, heat resistance, etc.
[0019] In the hard alloy of the present invention, it is preferred
that the specific element(s) is/are at least one selected from the
group consisting of titanium, zirconium, hafnium, vanadium, niobium
and tantalum, and a content of a cubic crystal compound mentioned
hereinbelow is 1% by volume or less, since strength and toughness
are particularly high. Also, it is preferred that the specific
element(s) is chromium, and 0.1 to 10% by weight of chromium is
contained based on the total amount of the hard alloy, since
chromium is also dissolved in the metal binder phase as a solid
solution, so that improved effects of hardness, toughness, heat
resistance, corrosion resistance, oxidation resistance, etc. are
more remarkable. Moreover, it is preferred that the specific
element(s) is/are manganese and/or rhenium, and 0.1 to 10% by
weight of manganese and/or rhenium is/are contained in the total
amount of the hard alloy, since it is/they are also dissolved in
the binder phase, whereby improved effects of hardness, toughness,
heat resistance, etc. are more remarkable.
[0020] The metal binder phase of the hard alloy according to the
present invention comprises an alloy containing iron group metal
(Fe, Co, Ni) as a main component and 30% by weight or less of W is
dissolved therein. More specifically, the binder phase may be
mentioned, for example, Co--W alloy, Co--Re alloy, Co--W--Cr alloy,
Ni--Mo alloy, Ni--Cr--W alloy, Co--Ni--Cr--W alloy, Fe--Ni--W
alloy, Fe--Mo--Cr alloy, Fe--Mn alloy, and the like. An amount of
the metal binder phase is defined to be 5 to 50% by volume, since
if it is less than 5% by volume, micro pores are remained in the
alloy, so that hardness, strength, toughness or fracture resistance
is lowered, while if it exceeds 50% by volume, hardness or wear
resistance is lowered.
[0021] The cubic crystal compound which is an optional component of
the hard alloy according to the present invention may be
specifically mentioned, for example, VC, NbC, TaC, (W,Ti)C,
(W,Zr)C, (W,Ti,Ta)C, (W,Ti,Re)C, TiN, ZrN, HfN, (W,Ti,Ta)--(C,N),
(W,Ti,Mo) (C,N), and the like. Here, the hard alloy of the present
invention may contain Cr.sub.7C.sub.3, Mo.sub.2C, etc. which do not
belong to the cubic crystal compound with a small amount. If the
content of the cubic crystal compound in the hard alloy exceeds 40%
by volume, an amount of WC to which the specific element(s) is/are
dissolved is relatively lowered, so that an improved effect thereof
becomes a little.
[0022] For preparing the hard alloy of the present invention, it is
necessary to use powder in which the specific element(s) has/have
previously been dissolved in the WC crystal as a starting material.
That is, the W-based composite carbide powder of the present
invention comprises complex carbide powder which contains tungsten,
carbon, and at least one specific element(s) selected from the
group consisting of titanium, zirconium, hafnium, vanadium,
niobium, tantalum, chromium, molybdenum, manganese and rhenium,
wherein said complex carbide powder contains 80% by volume or more
of hexagonal tungsten carbide, and 0.1 to 3.0% by weight of the
specific element(s)is/are dissolved in the crystals of the
hexagonal tungsten carbide.
[0023] An amount of the specific element(s) to be dissolved in the
W-based composite carbide powder of the present invention is
defined to be 0.1 to 3.0% by weight, since if it is less than 0.1%
by weight, improved effects on the WC itself such as hardness,
toughness, oxidation resistance, corrosion resistance, etc. are
low, and it is difficult to dissolve the specific element(s) in an
amount exceeding 3.0% by weight in the WC crystal. Here, when the
complex carbide of the present invention is represented by the
chemical formula, it is a material of (W.sub.1-x, M.sub.x)C.sub.y
wherein x and y satisfy the relationship of 0.002<x<0.06 and
0.95<y<1.00 since the specific element(s) is/are substituted
for the W atom in the WC crystal, and taken into the hexagonal
crystal lattice. Provided that M represents at least one of the
specific elements.
[0024] The W-based composite carbide powder of the present
invention comprises WC in which the specific element(s) is/are
dissolved as a main component, and a cubic crystal compound into
which W is dissolved, and W.sub.2C, Cr.sub.3C.sub.2, Mo.sub.2C or
the like into which the specific element(s) is dissolved. If an
amount of the WC in which the specific element(s) is/are dissolved
is less than 80% by volume, improved effects on hardness,
toughness, oxidation resistance, corrosion resistance, etc. due to
the specific element(s) dissolved in WC are little in the hard
alloy to be produced by using the present products.
[0025] Here, the cubic crystal compound which may be contained in
the complex carbide powder comprises W, carbon and/or nitrogen, and
at least one selected from the group consisting of titanium,
zirconium, hafnium, vanadium, niobium and tantalum. Specific
compositions thereof may be mentioned
(W.sub.0.6Ti.sub.0.4)C.sub.0.8, (W.sub.0.06Zr.sub.0.95) C.sub.0.75,
(W.sub.0.45V.sub.0.55) C.sub.0.9, (W.sub.0.65Ta.sub.0.35)
C.sub.0.9, (W.sub.0.5Ti.sub.0.5) (C.sub.0.9N.sub.0.1).sub.0.95,
(W.sub.0.5Ti.sub.0.3Ta.sub.0.2)C.sub.0.9, and the like. These cubic
crystal compounds are formed when the specific element(s) is/are
added exceeding a limit of an amount capable of being dissolved,
and to show added effects of the specific element(s) at the highest
level, the presence of the cubic crystal compound is sometimes
preferred. However, if an amount thereof becomes 20% by volume or
more, it becomes difficult to adjust a ratio of the composition for
producing the hard alloy, and in particular, a problem of lowering
in strength of the hard alloy arises. Also, W.sub.2C is likely
formed when the content of carbon is lower, when the powder is
subjected to heat treatment at higher temperatures, when the
specific element(s) is Cr or Mo, or the like, but to enlarge an
amount of the element(s) to be dissolved, W.sub.2C is rather
preferably contained in an amount of up to 5% by volume.
[0026] In the W-based composite carbide powder of the present
invention, it is preferred that the WC crystal to which the
specific element(s) is/are dissolved has a lattice constant of a
axis of a hexagonal crystal lattice of 0.2910 nm or longer and/or a
lattice constant of c axis of the same of 0.2840 nm or longer,
since dissolution of the specific element(s) in the WC crystal is
complete and uniform whereby improved effects of the various kinds
of characteristics become maximum.
[0027] The hard alloy of the present invention can be produced by
the conventionally employed powder metallurgy method when the
W-based composite carbide powder of the present invention is used
as a starting material. On the other hand, the W-based composite
carbide powder can be obtained, for example, by heating a mixed
powder of WC and TiH.sub.2, a mixed powder of W, TiN and carbon, a
mixed powder of WO.sub.3, TiO.sub.2 and carbon and the like in a
non-oxidative atmosphere or a combined atmosphere of reducing and
carburizing atmospheres at high temperatures. Also, when it is
produced by the following method and conditions, powder with a much
amount of dissolution as well as a uniform dissolution degree and
uniform grain size distribution can be produced. That is, the
W-based composite carbide powder of the present invention can be
produced by subjecting a mixed powder comprising W powder, carbon
powder and oxide powder of the specific element(s) each having a
grain size of 1 .mu.m or less to heat treatment at 1500 to
2000.degree. C. or so in an inert gas atmosphere or under vacuum.
When the heat treatment temperature is higher, an amount of the
specific element(s) dissolved in the powder increases but the WC
crystals become coarse to cause abnormal grain growth. Also, when
Cr or Mn which has a higher vapor pressure is used as the specific
element(s), it is necessary to carry out the procedure at a low
temperature treatment in which an inert gas is introduced and
dissipation thereof shall be prevented.
[0028] In the hard alloy of the present invention, the hexagonal
tungsten carbide into which the specific element(s) is/are
dissolved, which is in the W-based composite carbide powder used as
a starting material has functions of improving hardness, toughness,
heat resistance, corrosion resistance, oxidation resistance, etc.
of the tungsten carbide itself, and the improved characteristics
have functions of improving alloy characteristics or practical
characteristics.
EXAMPLE 1
[0029] By using each powder of commercially available W having an
average particle size of 0.5 .mu.m, carbon black (hereinafter
referred to as "C") having an average particle size of 0.02 .mu.m,
TiO.sub.2, ZrO.sub.2, HfO.sub.2, V.sub.2O.sub.5, Nb.sub.2O.sub.5,
Ta.sub.2O.sub.5, Cr.sub.2O.sub.3, MoO.sub.3 and MnO.sub.2 each
having an average particle size of 0.05 to 0.2 .mu.m, metal Re
having an average particle size of 1.0 .mu.m, and WC (hereinafter
referred to as "WC/F") having an average particle size of 0.5
.mu.m, TiC having an average particle size of 1.2 .mu.m, Mo having
an average particle size of 1.1 .mu.m, WC (hereinafter referred to
as "WC/C") having an average particle size of 3.5 .mu.m, each
powder was weighed with a formulation shown in Table 1, placed in a
pot made of stainless steel with an acetone solvent and balls made
of a hard alloy, mixed and pulverized for 24 hours and then dried
to obtain respective mixed powders. Then, these mixed powders were
each filled in a carbon crusible, and heated after inserting into a
vacuum furnace. Heating was carried out under about 20 Pa vacuum
until 1200.degree. C., and heating thereafter was carried out under
atmosphere and a temperature shown in Table 1 maintaining for 1.0
hour to obtain products of the present invention (present
products): PA to PR and Comparative product: complex carbide
powders of CA to CH. Provided that Comparative product: CH is not
subjected to mixing and heat treatments.
1TABLE 1 Heated Results of Sample Composition Heated temperature
X-ray No. (% by weight) atmosphere (.degree. C.) diffractmetry
Present products PA 93.6W--6.2C--0.2TiO.sub.2 Vacuum 1800 WC +
W.sub.2C about 10 Pa PB 93.0W--6.3C--0.7TiO.sub.2 Vacuum 1800 WC
about 10 Pa PC 91.3W--6.7C--2.0TiO.sub.2 Vacuum 1900 WC + (W, Ti)
about 10 Pa C + W.sub.2C PD 88.7W--7.3C--4.0TiO.sub.2 Vacuum 2000
WC + (W, Ti) about 10 Pa C + W.sub.2C PE 92.7W--6.3C--1.0ZrO.sub.2
Vacuum 1900 WC + W.sub.2C about 10 Pa PF 92.8W--6.2C--1.0HfO.sub.2
Vacuum 2000 WC + W.sub.2C about 10 Pa PG
92.5W--6.5C--1.0V.sub.2O.sub.5 Vacuum 1800 WC about 10 Pa PH
92.6W--6.4C--1.0Nb.sub.2O.sub.5 Vacuum 1900 WC + W.sub.2C about 10
Pa PI 92.7W--6.3C--1.0Ta.sub.2O.sub.- 5 Vacuum 1900 WC + W.sub.2C
about 10 Pa PJ 89.0W--7.0C-- Vacuum 2000 WC + (W, Ta,
2.0Ta.sub.2O.sub.5--2.0TiO.sub.2 about 10 Pa Ti) C + W.sub.2C PK
91.4W--6.6C--2.0Cr.sub.2O.sub.3 0.1 MPa Ar 1800 WC + W.sub.2C PL
92.6W--6.4C--1.0Cr.sub.2O.sub.3 0.1 MPa Ar 1850 WC PM 90.9W--6.6C--
0.1 MPa Ar 1900 WC + 2.0Cr.sub.2O.sub.3--0.5Ta.sub.2O.sub.5 (W,
Cr).sub.2C PN 88.9W--7.1C--4.0MoO.sub.3 Vacuum 1800 WC + W.sub.2C
about 10 Pa PO 92.0W--6.5C--1.5MnO.sub.2 10 kPa Ar 1500 WC + (W,
Mn).sub.2C PP 91.8W--6.6C-- 10 kPa Ar 1550 WC
1.0MnO.sub.2--0.5Ta.sub.2O.sub.5 PQ 92.8W--6.2C--1.0Re Vacuum 1800
WC about 10 Pa PR 91.1W--6.3C--2.0Re-- 0.1 MPa Ar 1800 WC
0.6Cr.sub.2O.sub.3 Comparative products CA 93.8W--6.2C Vacuum 1700
WC about 10 Pa CB 100.0WC/F Vacuum 1600 WC + W.sub.2C about 10 Pa
CC 93.7W--6.2C--0.1TiO.sub.2 Vacuum 1750 WC about 10 Pa CD
99.8WC/F--0.2TiC Vacuum 1800 WC + (W, Ti) about 10 Pa C + W.sub.2C
CE 81.2W--8.8C-- Vacuum 1900 (W, Ti) C + 10.0TiO.sub.2 about 10 Pa
WC + W.sub.2C CF 88.0W--7.0C--5.0Cr.sub.2O.sub.3 0.1 MPa Ar 1800 WC
+ (W, Cr).sub.2C CG 89.0W--6.0C--5.0Mo Vacuum 1800 WC + W.sub.2C
about 10 Pa CH 100.0WC/C -- -- WC
[0030] Complex carbide powders of the thus obtained Present
products PA to PR and Comparative products CA to CH were crushed
and pulverized, and passed through a sieve of 100 mesh to prepare
sample powders for evaluation. With regard to these samples, X-ray
diffraction analysis (tube: Cu, tube voltage; 50 kV, tube current;
250 mA) was carried out 10 and components in the powder were
identified. The results are also shown in Table 1.
[0031] Next, to the respective sample powders was added 30% by
weight of cupper powder (commercially available electrolytic copper
powder: 2.5 .mu.m) and the mixture was mixed by using a mortar, and
after molding by a mold with a pressure of 2 ton/cm.sup.2, these
samples were heated and sintered under vacuum at 1150.degree. C.
for 20 minutes to obtain sample alloys for analyses. Then, these
sample alloys were polished by diamond whetstone and subjected to
lap processing with a diamond paste having an average particle size
of 1 .mu.m, and then, applied to observation and analyses by an
electric field radiation type scanning electron microscope.
[0032] First, presence and distribution of WC and particles other
than WC (W.sub.2C, cubic crystal compound, etc.) were confirmed by
compositional image contrast and element mapping. With regard to WC
and cubic crystal compound, compositional analyses were carried out
by focusing electronic beam to the center potion of a particle
having a relatively large size. Also, a content (% by volume) of
the respective particles constituting the respective sample powders
was obtained by photographs and an image treatment device. These
results are shown in Table 2. Moreover, average particle sizes of
WC, W.sub.2C and cubic crystal compounds were obtained. The results
are shown in Table 3.
2 TABLE 2 Amount of Composition of powder dissolved (% by volume)
Sample element in WC Cubic crystal No. (% by weight) WC W.sub.2C
compound Present products PA 0.12Ti 99.0 1.0 O PB 0.42Ti 100.0 0 0
PC 0.82Ti 93.2 2.6 4.2(W.sub.0.6Ti.sub.0.4)C PD 0.87Ti 80.3 3.4
16.3(W.sub.0.6Ti.sub.0.4)C PE 0.73Zr 98.4 1.6 0 PF 0.85Hf 97.1 2.9
0 PG 0.57V 100.0 0 0 PH 0.70Nb 98.0 2.0 0 PI 0.82Ta 99.0 1.0 0 PJ
0.80Ta + 0.54Ti 86.8 3.2 10.0(W.sub.0.6Ta.sub.0.2Ti.sub.0.2)C PK
1.37Cr 97.6 2.4 0 PL 0.60Cr 100.0 0 0 PM 1.00Cr + 0.42Ta 99.0 1.0 0
PN 2.73Mo 96.0 4.0 0 PO 0.87Mn 98.7 1.3 0 PP 0.62Mn + 0.37Ta 100.0
0 0 PQ 1.00Re 100.0 0 0 PR 1.75Re + 0.35Cr 100.0 0 0 Comparative
products CA 0 100.0 0 0 CB 0 97.9 2.1 0 CC 0.06Ti 100.0 0 0 CD
0.08Ti 98.7 0.4 0.9(W.sub.0.6Ti.sub.0.4)C CE 0.85Ti 39.9 10.4
49.7(W.sub.0.6Ti.sub.0.4)C CF 3.22Cr 92.6 7.4 0 CG 5.00Mo 90.9 9.1
0 CR 0 100.0 0 0
[0033]
3 TABLE 3 Average particle size (.mu.m) Cubic Lattice constants
Sample system (nm) No. WC W.sub.2C compound a axis c axis Present
products PA 3.1 0.8 -- 0.2913 0.2845 PB 2.5 0.6 -- 0.2911 0.2844 PC
2.7 0.9 0.9 0.2917 0.2851 PD 3.6 1.3 2.4 0.2915 0.2850 PE 3.0 0.8
-- 0.2914 0.2849 PF 7.3 2.0 -- 0.2913 0.2846 PG 1.2 0.5 -- 0.2911
0.2841 PH 1.8 0.7 -- 0.2912 0.2847 PI 2.7 0.8 -- 0.2916 0.2850 PJ
3.5 1.1 2.2 0.2919 0.2852 PK 3.1 2.2 -- 0.2911 0.2847 PL 2.0 -- --
0.2914 0.2847 PM 2.4 1.5 -- 0.2912 0.2844 PN 2.4 2.9 -- 0.2915
0.2849 PO 2.5 1.8 -- 0.2911 0.2850 PP 2.4 -- -- 0.2919 0.2841 PQ
3.4 -- -- 0.2914 0.2852 PR 1.7 -- -- 0.2919 0.2847 Comparative
products CA 3.1 0.8 -- 0.2905 0.2837 CB 1.3 0.9 -- 0.2907 0.2835 CC
2.9 0.8 -- 0.2909 0.2841 CD 3.2 1.7 1.4 0.2908 0.2839 CE 2.8 0.8
1.8 0.2917 0.2852 CF 2.2 2.4 -- 0.2902 0.2831 CG 3.2 1.4 -- 0.2909
0.2855 CH 3.5 1.1 -- 0.2906 0.2837
[0034] Next, an interplanar spacing and a lattice spacing were
calculated from the position of a peak of WC (2.theta.=30 to
120.degree.) which was measured by the above-mentioned X-ray
diffraction conditions, and lattice constants were obtained with
respect to each of a axis and c axis by an extrapolation method.
The results are also shown in Table 3.
EXAMPLE 2
[0035] By using complex carbide powders PA, PB, PE, PG, PH, PI, PJ,
PK, PL, PM, PO, PP, PQ and PR as well as CA, CB, CD and CH obtained
in Example 1, respective powders of W, C and metal Re used in
Example 1, and commercially available Co having an average particle
size of 1.0 .mu.m, Ni with 1.2 .mu.m, Fe with 1.0 .mu.m, metal Mn
with 3.5 .mu.m, and TiC, ZrC, VC, NbC, TaC and Cr.sub.3C.sub.2 each
having 1.0 to 1.5 .mu.m, these powders were weighed with a
composition shown in Table 4, inserted in a pot made of stainless
with an acetone solvent and balls made of hard alloy and pulverized
and crushed for 48 hours, and then, dried to obtain respective
mixed powders. Here, a formulated carbon amount was adjusted by
addition of C or W, so that the alloy became medium carbon alloy
(center of a range of a sound phase which does not precipitate free
carbon or Co.sub.3W.sub.3C, Ni.sub.2W.sub.4C) after sintering.
Then, these powders were filled in a mold, and green compacts
having a size of 5.5.times.9.5.times.29 mm were produced with a
pressure of 196 MPa, placed on a sheet comprising alumina and
carbon fiber and heated by inserting into a vacuum atmosphere
furnace. Up to 1200.degree. C., the atmosphere was made vacuum of
about 20 Pa, and thereafter, heating was carried out in the
atmosphere shown in Table 4, and sintering was carried out at
1400.degree. C. for 1.0 hour to obtain hard alloys of Present
products 1 to 14 and Comparative products 1 to 14. Incidentally,
Present product and Comparative product with the same number were
so formulated that the components of the hard alloy and grain size
of WC are substantially the same.
4TABLE 4 Composition Sintering Sample No. (% by weight) atmosphere
Present 1 93.0PA--7.0Co Vacuum about 10 Pa Products 2 93.0PB--7.0Co
Vacuum about 10 Pa 3 92.92E--0.1C--7.0Co Vacuum about 10 Pa 4
93.0PG--7.0Co Vacuum about 10 Pa 5 92.9PH--0.1C--7.0Co Vacuum about
10 Pa 6 93.0PI--7.0Co Vacuum about 10 Pa 7 92.8PJ--0.2C--7.0Co
Vacuum about 10 Pa 8 92.5PK--0.5Cr.sub.3C.sub.2--7.0Co 1 kPa Ar 9
92.0PL--8.0Co 1 kPa Ar 10 91.9PM--0.1C--8.0Co 1 kPa Ar 11
90.0PO--2.0W--8.0Ni 10 kPa Ar 12 89.0PP--3.0W--8.0Ni 10 kPa Ar 13
92.0PQ--8.0Co Vacuum about 10 Pa 14 91.8PR--0.2C--8.0Ee 1 kPa Ar
Comparative 1 93.0CD--7.0Co Vacuum about 10 Pa products 2
62.5CA--30.0CB--0.5TiC--7.0Co Vacuum about 10 Pa 3
92.2CA--0.8ZrC--7.0Co Vacuum about 10 Pa 4
92.2CB--0.1C--0.7VC--7.0Co Vacuum about 10 Pa 5
22.1CA--70.0CB--0.1C--0.8NbC-- Vacuum about 10 Pa 7.0Co 6
82.2CA--10.0CB--0.8TaC--7.0Co Vacuum about 10 Pa 7
90.0CH--1.GTaC--1.4TiC--7.0Co Vacuum about 10 Pa 8
91.0CA--2.0Cr3C2--7.0Co 1 kPa Ar 9 31.3CA--60.0CB--0.7Cr.sub.3C.-
sub.2--8.0Co 1 kPa Ar 10 47.9CA--40.0CB--2.2W--0.4TaC-- 1 kPa Ar
1.5Cr.sub.3C.sub.2--8.0Co 11 58.1CA--30.0CB--3.0W--0.9Mn- -- 10 kPa
Ar 8.0Ni 12 48.0CA--40.0CB--CB--3.0W--0.4TaC-- 10 kPa Ar
0.6Mn--8.0Ni 13 91.1CH--0.9Re--8.0Co Vacuum about 10 Pa 14
19.44CA--60.0CB--0.3C--0.5Cr.sub.3C.sub.2-- 1 kPa Ar
1.8Re--8.0Fe
[0036] The resulting hard alloy sample piece was subjected to wet
polishing processing with a 230 mesh diamond whetstone to produce a
sample with a size of 4.0.times.8.0.times.25.0 mm, and
transverse-rupture strength (hereinafter abbreviated to as "TRS")
was measured by the JIS method. Also, one surface of the same
sample was subjected to lap processing with a diamond past having
an average particle size of 0.3 .mu.m, hardness and fracture
toughness value K1C (IM method) were measured under a load of 196N
using a Vickers indenter. Moreover, micro-structural photograph was
taken by an electron microscope with regard to the lap surface of
the respective samples, an average particle size of WC and contents
of the binder phase and the cubic crystal compound were obtained by
using an image treatment device. These results are shown in Table
5.
5TABLE 5 Amount of Fracture Particle binder Amount of toughness
size phase cubic crystal Sample TRS Hardness value of WC (% by
compound No. (MPa) (HV) (MPa .multidot. m.sup.1/2) (.mu.m) volume)
(% by volume) Present products 1 3160 1640 11.6 3.1 11.8 0 2 3050
1670 10.8 2.5 11.5 0.6(W,Ti)C 3 2850 1660 11.3 3.0 11.6 0.2(Zr,W)C
4 2770 1790 8.9 1.2 11.6 0.3VC 5 3210 1710 10.7 1.8 11.6 0.2NbC 6
3140 1650 11.1 2.7 11.7 0.1TaC 7 2540 1680 10.0 3.4 11.1
4.7(W,Ti,Ta)C 8 2910 1630 11.2 3.0 12.6 0 9 2790 1650 10.5 1.9 13.6
0 10 2780 1570 11.2 2.2 14.7 0 11 2840 1610 10.9 2.3 13.7 0 12 2920
1620 10.5 2.1 13.6 0 13 2750 1620 10.6 3.2 13.5 0 14 2790 1630 12.5
2.4 13.7 0 Comparative products 1 2530 1620 11.3 3.2 11.7
0.8(W,Ti)C 2 2310 1640 10.5 2.5 11.5 2.9(W,Ti)C 3 2420 1610 11.1
3.1 11.7 1.7(Zr,W)C 4 2490 1770 8.8 1.2 11.6 1.9VC 5 2170 1690 10.2
1.7 11.7 1.5NbC 6 1980 1630 10.8 2.8 11.8 0.8TaC 7 2410 1630 9.8
3.3 11.0 9.4(W,Ti,Ta)C 8 2760 1590 10.9 3.0 15.1 0 9 2650 1620 10.2
2.0 14.5 0 10 2610 1530 10.7 2.5 15.8 0.5TaC 11 2730 1590 10.5 2.3
15.0 0 12 2840 1610 10.1 2.1 13.8 0.4TaC 13 2750 1610 10.2 3.1 13.9
0 14 2380 1600 12.0 2.3 14.7 0
[0037] The hard alloys produced by the W-based composite carbide
powder of the present invention are improved in all of hardness,
strength, toughness, etc., as compared with the hard alloy using
the conventional high purity WC, when the composition and the WC
grain size are made almost the same, and for example, in the hard
alloy to which a small amount of TiC or TaC is added, there is a
remarkable effect that strength is highly improved.
* * * * *