U.S. patent application number 12/837720 was filed with the patent office on 2011-01-06 for formable sintered alloy with dispersed hard phase.
This patent application is currently assigned to PARKER HANNIFIN CORPORATION. Invention is credited to John Fulmer, Stephanie Renaud, RICHARD SCOTT.
Application Number | 20110002805 12/837720 |
Document ID | / |
Family ID | 40788871 |
Filed Date | 2011-01-06 |
United States Patent
Application |
20110002805 |
Kind Code |
A1 |
SCOTT; RICHARD ; et
al. |
January 6, 2011 |
FORMABLE SINTERED ALLOY WITH DISPERSED HARD PHASE
Abstract
A method of forming an iron based sintered body which comprises
in % by mass: 0.4 to 1.0% of C; 0.5 to 3.5% of Cr; 0.1 to 1.7% of
Mo; 0.3 to 3.0% of Cu and microstructure of about 20-50% dispersed
martensite in a matrix of fine pearlite is provided. The method
utilizes a step of cooling a sintered article at a rate not
exceeding 0.5.about.C/sec. Ni and/or Mn may also be included in the
method.
Inventors: |
SCOTT; RICHARD; (Cumberland,
ME) ; Renaud; Stephanie; (Lewsiton, ME) ;
Fulmer; John; (Old Orchard Beach, ME) |
Correspondence
Address: |
PARKER-HANNIFIN CORPORATION;HUNTER MOLNAR BAKER MORGAN
6035 PARKLAND BOULEVARD
CLEVELAND
OH
44124-4141
US
|
Assignee: |
PARKER HANNIFIN CORPORATION
Cleveland
OH
|
Family ID: |
40788871 |
Appl. No.: |
12/837720 |
Filed: |
July 16, 2010 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
12339565 |
Dec 19, 2008 |
|
|
|
12837720 |
|
|
|
|
61015024 |
Dec 19, 2007 |
|
|
|
Current U.S.
Class: |
419/25 |
Current CPC
Class: |
C22C 33/0285 20130101;
C22C 38/42 20130101; C22C 38/44 20130101; C22C 38/22 20130101; C22C
38/20 20130101; C22C 38/04 20130101 |
Class at
Publication: |
419/25 |
International
Class: |
B22F 3/24 20060101
B22F003/24; B22F 1/02 20060101 B22F001/02; B22F 3/12 20060101
B22F003/12 |
Claims
1. A method of forming an iron based sintered body having a
microstructure of about 20-50% dispersed martensite in a matrix of
fine pearlite, the method comprising the steps of: providing a
mixture comprising a composition in % by mass: 0.4 to 1.0% of C;
0.5 to 3.5% of Cr; 0.1 to 1.7% of Mo; 0.3 to 3.0% of Cu, the
balance being primarily Fe and unavoidable impurities and
lubricant; placing the mixture in a first mold possessing the
approximate shape of a finished product; subjecting the mold to
compaction pressures of between generally 35 and 65 tsi to produce
a green body compact; sintering the green body compact at a
temperature of between 1120.about.C and 1180.about.C to form a
sintered article; cooling the sintered article at a rate not
exceeding 0.5.about.C/sec; thermally stabilizing the sintered
article; placing the sintered article in a second mold possessing
the desired shape of the finished product; subjecting the second
mold to pressures generally between 50 and 75 tsi.
2. The method of claim 1 wherein the step of sintering the green
body compact is performed in an atmosphere comprising about 90%
nitrogen and 10% hydrogen.
3. The method of claim 1 wherein the step of thermally stabilizing
the sintered article comprises cold treatment and tempering.
4. The method of claim 1, wherein the step of providing a mixture
further includes in % by mass: 0.1 to 0.5 of Mn.
5. The method of claim 1, wherein the step of providing a mixture
further includes in % by mass: 0.1 to 6.0 of Ni.
6. The method of claim 1, wherein the first mold is in the form of
a gerotor gear.
7. The method of claim 1, wherein the second mold is in the form of
a gerotor gear generally at net shape.
8. The method of claim 1, wherein the step of sintering the green
body compact at a temperature of between 1120.about.C and
1180.about.C is performed for about 25 minutes.
9. A method of forming an iron based sintered body having a
microstructure of about 20-50% dispersed martensite in a matrix of
fine pearlite, the method comprising the steps of: providing a
mixture comprising a composition in % by mass: 0.4 to 1.0% of C;
0.5 to 3.5% of Cr; 0.1 to 1.7% of Mo; 0.3 to 3.0% of Cu, the
balance being primarily Fe and unavoidable impurities and
lubricant; placing the mixture in a first mold possessing the
approximate shape of a finished product; subjecting the mold to
compaction pressures of between generally 35 and 65 tsi to produce
a green body compact; sintering the green body compact at a
temperature of between 1120.about.C and 1180.about.C in an
atmosphere comprising about 90% nitrogen and 10% hydrogen for about
25 minutes to form a sintered article; cooling the sintered article
at a rate not exceeding 0.5.about.C/sec; thermally stabilizing the
sintered article; placing the sintered article in a second mold
possessing the desired shape of the finished product; subjecting
the second mold to pressures generally between 50 and 75 tsi.
10. The method of claim 9 wherein the step of thermally stabilizing
the sintered article comprises cold treatment and tempering.
11. The method of claim 9, wherein the step of providing a mixture
further includes in % by mass: 0.1 to 0.5 of Mn.
12. The method of claim 9, wherein the step of providing a mixture
further includes in % by mass: 0.1 to 6.0 of Ni.
13. The method of claim 9, wherein the first mold is in the form of
a gerotor gear.
14. The method of claim 9, wherein the second mold is in the form
of a gerotor gear generally at net shape.
Description
RELATED APPLICATIONS
[0001] This application is a continuation of U.S. Non-Provisional
application Ser. No. 12/339,565 filed Dec. 19, 2008, which claims
the benefit of U.S. Provisional Application No. 61/015,024 filed
Dec. 19, 2007, both of which are hereby incorporated by
reference.
BACKGROUND
[0002] This invention relates to a formable sintered alloy with
dispersed hard phase.
SUMMARY
[0003] At least one advantage of the present invention is provided
by a method of forming an iron based sintered body having a
microstructure of about 20-50% dispersed martensite in a matrix of
fine pearlite, the method comprising the steps of: providing a
mixture comprising a composition in % by mass: 0.4 to 1.0% of C;
0.5 to 3.5% of Cr; 0.1 to 1.7% of Mo; 0.3 to 3.0% of Cu, the
balance being primarily Fe and unavoidable impurities and
lubricant; placing the mixture in a first mold possessing the
approximate shape of a finished product; subjecting the mold to
compaction pressures of between generally 35 and 65 tsi to produce
a green body compact; sintering the green body compact at a
temperature of between 1120.about.C and 1180.about.C to form a
sintered article; cooling the sintered article at a rate not
exceeding 0.5.about.C/sec; thermally stabilizing the sintered
article; placing the sintered article in a second mold possessing
the desired shape of the finished product; and subjecting the
second mold to pressures generally between 50 and 75 tsi.
[0004] At least one advantage of the present invention is provided
by a A method of forming an iron based sintered body having a
microstructure of about 20-50% dispersed martensite in a matrix of
fine pearlite, the method comprising the steps of: providing a
mixture comprising a composition in % by mass: 0.4 to 1.0% of C;
0.5 to 3.5% of Cr; 0.1 to 1.7% of Mo; 0.3 to 3.0% of Cu, the
balance being primarily Fe and unavoidable impurities and
lubricant; placing the mixture in a first mold possessing the
approximate shape of a finished product; subjecting the mold to
compaction pressures of between generally 35 and 65 tsi to produce
a green body compact; sintering the green body compact at a
temperature of between 1120.about.C and 1180.about.C in an
atmosphere comprising about 90% nitrogen and 10% hydrogen for about
25 minutes to form a sintered article; cooling the sintered article
at a rate not exceeding 0.5.about.C/sec; thermally stabilizing the
sintered article; placing the sintered article in a second mold
possessing the desired shape of the finished product; and
subjecting the second mold to pressures generally between 50 and 75
tsi.
BRIEF DESCRIPTION OF THE DRAWING
[0005] Embodiments of this invention will now be described in
further detail with reference to the accompanying drawing, in
which:
[0006] FIG. 1 is a microscopic view of an embodiment of the iron
based sintered material of the present invention;
[0007] FIG. 2 is a wear plot of a prior art gear after an
accelerated pump durability wear test;
[0008] FIG. 3 is a perspective view of a portion of the prior art
gear of FIG. 2 showing wear on the gear surface;
[0009] FIG. 4 is a wear plot of a embodiment of a gear of the
present invention after the same accelerated pump durability wear
test that the prior art gear of FIGS. 2-3 were subjected to;
and
[0010] FIG. 5 is a perspective view of a portion of the gear of
FIG. 4 showing light burnishing on the gear surface.
DETAILED DESCRIPTION OF THE INVENTION
[0011] A microscopic view of an embodiment of the composition of
the present invention is shown in FIG. 1. The lean composition
achieves desired microstructure/properties and associated sliding
wear resistance with reduced content of expensive alloying
ingredients. The constituent ingredients demonstrate sufficient
hardenability to achieve martensitic transformation at cooling
rates attainable in conventional furnaces thereby leveraging
existing installed capacity and deferring capital investment in
specialized furnaces. The constituent ingredients demonstrate
sufficient hardenability to achieve martensitic transformation at
cooling rates attainable in conventional furnaces thereby avoiding
the dimensional distortion penalty associated with rapid quenching
by oil baths and/or gas pressure quenching. The volume fraction of
fine pearlite matrix of generally 70% affords sufficient
formability to achieve a high degree of dimensional accuracy
required of net-shape sintered articles. Forming may be performed
without supplemental part heating, tool heating, intermediate
quenching and thereby avoids the associated operational complexity
and cost of warm/hot forming processes.
[0012] An embodiment of the iron-base alloy of the present
invention comprises a 20 to 50% weight fraction of prealloy steel
of composition A and a 48 to 78% weight fraction of prealloy steel
of composition B to which additional alloying elements (and
lubricant) are added in preparation of a powdered metal blended
mixture. The resulting mixture composition of the embodiment
comprises in % by mass: 0.4 to 1.0% of C; 0.5 to 3.5% of Cr; 0.1 to
1.7% of Mo; 0.3 to 3.0% of Cu; and the balance being primarily Fe
and unavoidable impurities. (The lubricant will volatilize during
sinter and as such is not reflected in the composition %). The
mixture is placed in a mold possessing the approximate shape of the
finished product and subjected to compaction pressures of between
generally 35 and 65 tsi to produce a green body compact. The green
body compact is subsequently sintered at a temperature of between
1120.about.C and 1180.about.C for about 25 minutes in an atmosphere
comprised of 90% nitrogen and 10% hydrogen. The sintered article
subsequently is cooled at a rate not exceeding 0.5.about.C/sec
producing a sinter-hardened composite wear resistant microstructure
of approximately 20 to 50% dispersed martensite in a matrix of fine
pearlite. The sintered article subsequently is subjected to cold
treatment and tempering for thermal stabilization. Upon completion
of thermal treatment, the sintered article is placed in a mold
possessing the desired shape of the finished product and
subsequently subjected to forming pressures generally between 50
and 75 tsi to achieve dimensional refinement enabling production of
discretely toleranced net-shape features. The sintered and formed
article demonstrates acceptable sliding wear properties for pumping
elements employed with ultra low sulfur diesel fuels (Shell MJ04
U.S. Worst Case Diesel) while offering the costs advantages of lean
composition and reduced process complexity in comparison to prior
art.
[0013] In one embodiment, Nickel may be added such that the
resulting mixture composition of the embodiment comprises in % by
mass: 0.4 to 1.0% of C; 0.5 to 3.5% of Cr; 0.1 to 1.7% of Mo; 0.3
to 3.0% of Cu; 0.1 to 6.0% Ni; and the balance being primarily Fe
and unavoidable impurities. In another embodiment, the resulting
mixture composition of the embodiment comprises in % by mass: 0.4
to 1.0% of C; 0.5 to 3.5% of Cr; 0.1 to 1.7% of Mo; 0.3 to 3.0% of
Cu; 0.1 to 0.5% Mn; and the balance being primarily Fe and
unavoidable impurities. In still another embodiment, the resulting
mixture composition of the embodiment comprises in % by mass: 0.4
to 1.0% of C; 0.5 to 3.5% of Cr; 0.1 to 1.7% of Mo; 0.3 to 3.0% of
Cu; 0.1 to 6.0% Ni; 0.1 to 0.5% Mn; and the balance being primarily
Fe and unavoidable impurities.
[0014] In one embodiment, the sintered and formed article may be a
gear, such as a gear for a gerotor. Testing of a sintered and
formed gear in accordance with the present invention was subjected
to an accelerated pump durability test with the results of the
prior art control gear shown in FIGS. 2 and 3 and the results of
the gear of the present invention shown in FIGS. 4 and 5. FIGS. 2
and 4 are wear plots showing the magnitude of the surface wear of
the gear teeth by vector representation. While the wear in FIG. 2
is significantly more than the gear of the present invention shown
in FIG. 4, it is noted that the wear shown in FIG. 4 is magnified
at a scale twice that of FIG. 2 in order to see the wear. It is
also noted that non-wear portions of the wear plot of FIG. 4 caused
by offset have been removed from the original plot to eliminate any
confusion from the wear comparison.
[0015] Although the principles, embodiments and operation of the
present invention have been described in detail herein, this is not
to be construed as being limited to the particular illustrative
forms disclosed. They will thus become apparent to those skilled in
the art that various modifications of the embodiments herein can be
made without departing from the spirit or scope of the invention.
Accordingly, the scope and content of the present invention are to
be defined only by the terms of the appended claims.
* * * * *