A composition containing 30 to 70 percent chromium carbide, 5 to 20 percent soft noble metal, 5 to 20 percent metal fluorides, and 20 to 60 percent metal binder is used in a powdered metallurgy process for the production of self-lubricating components, such as bearings. The use of the material allows the self-lubricating bearing to maintain its low friction properties over an extended range of operating temperatures

Dellacorte, Christopher

Sliney, Harold E.

English

NASA Technical Reports Server

United States Patent 1191 
Sliney et al. 
1.0 
.8 
.6 
[54] METHOD OF MAKING 
CARBIDE/FLUORIDE/SILVER 
COMPOSITES 
[75] Inventors: Harold E. Sliney, Parma; Christopher 
[73] Assignee: The United States of America as 
Dellacorte, Medina, both of Ohio 
represented by the Adminirtrator of 
the National Aeronautics and Space 
Administration, Washington, D.C. 
[21] Appl. No.: 571,058 
[22] Filed: Aug. 23, 1990 
[51] Int. C l . 5  .............................................. B22F 32/00 
[52] U.S. Cl. ........................................ 419/14; 419/30; 
419/32; 419/36; 419/38; 419/39; 419/49; 
419/54; 419/50; 419/57; 419/58; 419/69 
[58] Field of Search ....................... 419/14, 30, 32, 36, 
419/38, 39, 49, 54, 58, 50, 69, 57 
[561 References Cited 
US. PATENT DOCUMENTS 
2,313,070 12/1942 Hensel et al. ......................... 75/136 
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[ill Patent Number: 5,034,187 
[45] Date of Patent: Jul. 23, 1991 
2,852,367 8/1954 Goetzel et al. ....................... 75/201 
2,875,510 3/1959 Wagner et al. .................... 29/182.5 
2,998,641 9/1961 Atkinson et al. .................. 29A82.5 
3,755,164 8/1973 Van Wyk .............................. 252/12 
3,790,239 12/1974 Law et al. .......................... 308/307 
3,929,396 12/1975 Orkin et al. ......................... 308/241 
4,728,448 3/1988 Sliney ................................. 252A2.2 
Primary Examiner-Stephen J. Lechert, Jr. 
Assistant Examiner-Nina Bhat 
Attorney, Agent, or Firm-Gene E. Shook; John R. 
Manning; James A. M a c h  
[571 ABSTRAm 
A composition containing 30 to 70% chromium car- 
bide, 5 to 20% soft noble metal, 5 to 20% metal fluo- 
rides, and 20 to 60% metal binder is used in a powdered 
metallurgy process for the production of self-lubricat- 
ing components, such as bearings. The use of the mate- 
rial allows the self-lubricating bearing to maintain its 
low friction properties over an extended range of oper- 
ating temperatures. 
19 Claims, 1 Drawing Sheet 
0 200 400 600 800 1000 
TEMPERATURE, "C 
https://ntrs.nasa.gov/search.jsp?R=19910017930 2020-03-24T07:00:29+00:00Z
U.S. Patent 
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July 23, 1991 
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5,034,187 
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TEMPERATURE, "C 
5,034,187 
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to about 60% metal binder. Several powder metallurgi- 
cal processes are used for the production of self- 
lubricating components having compositions in these 
ranges. 
The powder metallurgical processes of the present 
invention are used to produce self-lubricating bearings 
which maintain their 10W friction properties over an 
extended range of operating temperatures. These Self- 
lubricating materials can be used at these temperatures 
BRIEF DESCRIPTION OF THE DRAWINGS 
The foregoing, as well as other objects, features, and 
advantages of the invention will become more apparent 
from the following detailed description when taken in 
conjunction with the drawing which is a graph showing 
the friction coefficient of a material prepared in accor- 
Carbide/fluoride/silver self-lubricating composite dance with the present invention plotted against tern- 
perature. 
METHOD OF MAKING 
CARBIDE/nUORIDE/SILVR COMPOSITES 
ORIGIN O F  THE INVENTION 
The invention described herein was made by employ- 
ees of the United States Government and may be manu- 
factured and used by and for the Government for gov- 
ernmental purposes without the payment of m y  royal. 
ties thereon or therefor. 
TECHNICAL FIELD 
This invention is concerned with a method for mak- 
ing a composite material which exhibits low friction and 
wear over a wide temperature range. This invention is 
particularly directed to powder metallurgical processes 
for preparing this material. 
materials were described in the prior art in U.S. Pat. No. 
4,728,448.That patent describes several satisfactory 20 
material compositions and general preparation methods BEST MODE FOR CARRYING OUT THE 
with emphasis on plasma spraying. INVENTION 
The prior art plasma spraying of these materials has 
Produced quality coatings with improved lubricating noble metal and chemically stable fluoride salts are 
Properties. However, it has been found that quality 25 blended in the desired proportions. Powder metallurgy 
control procedures required to assure satisfactory coat- parts produced in accordance with the present inven- 
tion contain about 20 weight percent to about 70 weight 
percent of an oxidation resistant carbide, such as chro- 
coatings, is not suitable for making free standing parts. mium carbide or hafnium carbide. The products further 
5 
10 in oxidizing and reducing atmospheres. 
Powders of chromium carbide, a metal binder, a soft 
by plasma spraying are and 
plasma spraying* capab1e Of producing 
It is, therefore, an object of the present invention to 30 contain from about weight percent to about 5o weight 
provide powder metallurgical processes for producing 
free components such as bearings, bushings, percent soft noble metal, such as silver or gold. The powder metallurgy parts further contain from valve seats, and gears. about 5 weight percent to about 20 weight percent A further object of the invention is to provide im- 
proved processes for making self-lubricating materials 35 
which exhibit low friction and wear Over a wide group 11, or rare earth metals, or mixtures thereof. The 
nal lubrication by oil, grease, or solid lubricants. with the present invention further contains from about 
powder metallurgical processes for producing self- 40 binder. The metal in the binder is an alloy of nickel, 
lubricated bearing and seal materials which are satisfac- 
tory for operation at temperatures from 25" C. or lower have been 
to 900' c. blended they are consolidated to form the composite 
material. This consolidation is accomplished by me- 
metallurgical processes for producing self-lubricated 45 chanical Pressing in a die, cold isostatic Pressing, Or 
materials that are satisfactory in oxidizing atmospheres, rolling followed by heating either by sintering in a non- 
such as air, and reducing atmospheres, such as hydro- oxidizing atmosphere Or by hot Pressing. 
gen, at high temperatures. More particularly, the powders are consolidated by 
cold isostatic pressing at a temperature of about 25' C. 
BACKGROUND ART. 5 0  and a pressure between about 40 Ksi and about 80 Ksi. 
U.S. pat. No. 2,313,070 to Hensel et al is concerned This is followed by sintering at a temperature between 
with a composition which is used in making an elect& about 900' c. to about 1200" C. for about 10 to 30 min- 
cal contact. U.S. Pat. NO. 2,852,367 to Goetzol et a1 is utes. The sintering is performed in hydrogen or inert 
directed to a heat resistant material comprising car- gas at a Pressure of one atmosphere. In another pre- 
bides, borides and hafnium. 55  ferred embodiment, cold isostatic pressing is followed 
U.S. Pat. No. 2,875,510 to Wagner descnies a bear- by hot isostatic pressing at a temperature between about 
ing composition for producing bearings of a powdered 900' c. and about 1200" C. and a pressure between 
material. U.S. Pat. No. 2,998,461 to Atkinson et al is about 20 Ksi and about 60 Ksi. In still another embodi- 
directed to the combination of a carbide with a nobe1 ment the blended powders are hot isostatically pressed, 
metal in a powdered metallurgy composition. U.S. Pat. 60 hot mechanically pressed, or hot rolled without prior 
No. 3,929,396 to Orkin discloses a molded plastic bear- cold compaction at a temperature between about 900' 
ing assembly. C. and about 1200' C. and a pressure between about 20 
Ksi and about 60 Ksi. However, with this single step 
method it is more difficult to obtain near final shape DISCLOSURE OF THE INVENTION 
in percents by weight about 20% to about 70% chro- The consolidated powders may then be densified to 
mium carbide, about 5% to about 50% soft noble metal, produce the finished part. This densification can be 
about 5% to about 20% metal fluorides, and about 20% accomplished by sizing, coining, or hot rolling. This 
fluorides* These fluorides can be from group 
perature range in the absence of any supplemental exter- 
A still further object of the invention is to provide 
parts fabricated from powder in accordance 
2o weight percent to about 60 weight percent metal 
or a mixture thereof. 
After the powders Of the 
Another object of the invention is to provide powder 
8 
This invention is directed to a composition containing 65 parts. 
5.034,187 
3 
step is often not required after hot pressing which USU- 
ally produces fully-dense parts. 
In order to illustrate the beneficial technical effects of 
the invention, blended powders were poured into a steel 
die and cold pressed at 8 Ksi. The resulting compact 
was then carefully placed in a rubber bag and cold 
isostatically pressed at 60 Ksi. The green compact, 
which was about 70% dense, was weighed and mea- 
sured and then sintered in a hydrogen atmosphere at 
1 100" C. for 20 minutes. Heating and cooling rates were 
constant at 10" C./minute. 
The sintered slug had a measured bulk density of 
about 80%. Liquid porosimetry was done on some sam- 
ples which indicated that approximately one-third of 
the remaining porosity was open. The sintering resulted 
in densification, but there were little or no chemical 
reactions between phases. 
The sintered slugs were approximately 10 mm in 
diameter and 25 mm long. T o  make the wear pin speci- 
5 
10 
15 
mens, the slugs were rough machined to an outside 20 
diameter of 9.5 mm with a tungsten carbide tool bit. 
Water was used as grinding lubricant/coolant to pre- 
vent contamination of the parts. The ends of the pin 
were then diamond ground to a radius of 4.76 mm. 
treated in H2 containing a small amount of water vapor 
at 900" C. for 60 minutes to help bring more fluoride 
lubricant to the machined surface. The fluorides have a 
tendency to migrate to the surface at elevated tempera- 
tures. 
The specimens were tested in a pin-on-disk tribome- 
ter. With this configuration, hemispherically tipped pins 
of a composite material made in accordance with the 
invention were placed in sliding contact against disks 
made from a precipitation hardened nickel cobalt chro- 35 
mium superalloy having a hardness of RC 38 to 40 at 
room temperature. 
The pins generated 51 mm diameter wear tracks on 
the disk. Sliding was unidirectional at 0.27 to 5 m/sec 
and loads of 0.5 to 3.0 kg were applied with dead- 
weights. Most of the tests were done at 2.7 m/sec slid- 
ing velocity and 0.5 kg load so that direct comparisons 
of the data could be made to previous tests. The disks 
were heated with a low frequency induction heater. 
Temperature was measured with an infrared pyrometer 
capable of measuring surface temperatures from 100" C. 
to 1400' C.C5%. The test atmosphere was air with a 
relative humidity of 35% at 25" C.. In general, tests 
were run for 30 minutes, then the specimens were re- 
moved from the rig and wear measurements were made. 
A relocation dowel on the specimen holder allowed for 
accurate replacement of the specimens. 
The friction and wear results are given in the table 
and graphed in the drawing. The friction and wear of 55 
the composite/metal couple are similar to results ob- 
tained previously with similar coatings on a metal disk 
sliding against a metal pin. 
Following the machining, the pins are preferably heat 25 
30 
40 
45 
FRICTION 60 . . ..- . --. 
TEMPERATURE, 'C. LOAD, kg COEFFICIENT, p 
RSO 0.5 0.29 * 0.03 _. - 
760 0.5 0.35 f 0.06 
. 350 0.5 0.38 * 0.02 
25 0.5 0.35 f 0.05 65 
The friction for the pins sliding against the disks 
4 
Wear lower at 760' C. to 850" C. than at 25" C. and 350" 
C., but are well within the moderate to low range. 
ALTERNATE EMBODIMENTS OF THE 
INVENTION 
It is contemplated that the consolidation of the pow- 
ders may be accomplished by several other processes in 
sequence. More particularly, the blended powders can 
be consolidated by cold mechanical pressing at 5 Ksi to 
80 Ksi at 25' C. and then hot isostatically pressed at 900" 
C. to 1200" C. at 20 Ksi to 60 Ksi. 
The blended powders may be consolidated by first 
cold mechanical pressing at the aforementioned temper- 
atures and pressures followed by the preferred cold 
isostatic pressing and sintering as set forth above. Still 
another process for consolidation is a single hot me- 
chanical pressing at 900" C. to 1200" C. This hot press- 
ing is carried out at 20 Ksi to 60 Ksi in hydrogen or an 
inert gas environment. 
The blended powders may be cold rolled followed by 
sintering at 900' C. to 1200" C. for ten to thirty minutes. 
This sintering is carried out in hydrogen or inert gas 
environment. 
While several embodiments of the invention have 
been described, it will be appreciated that various pro- 
cedural modifications may be made to the invention 
without departing from the spirit thereof or the scope of 
the subjoined claims. By way of example, the aforemen- 
tioned range of parameters may be extended. It is con- 
templated that higher mechanical and isostatic pres- 
sures may be used where equipment with high pressure 
capabilities is available. 
From the aforementioned description, it is apparent 
that the powdered metallurgy processes of the present 
invention and the plasma spray processes of the prior 
art each have their own advantages depending on the 
intended application. The powder metallurgy processes 
of the present invention have the advantage of produc- 
ing entire parts, while the plasma spray processes are 
only suitable for producing coatings. 
In addition, there is very little waste with the pow- 
dered metallurgy process of the present invention. 
More particularly, very little material is lost during the 
powder metallurgy processing, while much material 
can be lost by overspray during plasma spray processes. 
This is especially important when precious metals, such 
as gold and silver, are among the components. 
Also, composition control of the final product is eas- 
ier by powder metallurgy processes because none of the 
components of the blended powders is selectively lost. 
In the spray process great care is required to achieve the 
desired composition because of the different deposit 
efficiencies of the various components. 
We claim: 
- 1. A method of making a free standing product from 
components of a self-lubricating, friction and wear re- 
ducing composite material consisting essentially of 
about 20-70% by weight carbide, about 5-50% by 
weight soft noble metal, about 5-20% by weight fluro- 
dies, and about 20-60% by weight metal binder, said 
method comprising the steps of 
blending powders of said components in said compos- 
cold compacting said blended powders thereby form- 
heating said composite material thereby forming said 
ite range, 
ing said composite material, and 
ranges from 0.29k0.03 ai 850' C. to 0.35k0.5 at 25" C. free standing product. 
5,034,187 
5 6 
2. A method of making a composite material as 
claimed in claim 1 wherein the blended powders are 
first cold compacted and then sintered. 
3. A method of making a composite material as 
'Iairned in 'Iaim wherein the powders are 
cold compacted by cold mechanical pressing. 
4. A method Of making a material as 
claimed in Claim 3 wherein the blended powders are 
cold mechanically pressed at a temperature of about 25" io cold compacted by cold isostatic pressing. 
C. and a pressure between about 5 Ksi to about 80 Ksi. 
5. A method of making a composite material as 
11. A method of making a composite material as 
claimed in claim 10 wherein the blended powders are 
cold compacted by cold mechanical pressing. 
12. A method of making a composite material as 
5 claimed in claim 11 wherein the blended powders are 
cold mechanically pressed at a temperature of about 25" 
C. and a pressure between about 5 Ksi to about 80 Ksi. 
13. A method of making a composite material as 
claimed in claim 10 wherein the blended powders are 
14. A method of making a composite material as 
claimed in claim 13 wherein the blended powders are 
C. and a pressure between 40 Ksi to about 80 Ksi. 
15. A method of making a composite material as 
claimed in claim 10 wherein the cold compacted pow- 
tween about c. to about 1200" c. at a pressure of 
about 20 ~~i to about 60 ~ ~ i .  
16. A method of making a composite material as 
claimed in claim 2 wherein the blended powders are 
cold compacted by cold rolling. 
17. A method of making a composite material as 
chimed in claim 16 wherein the compacted Powders 
8. A method of making a composite material as 25 are sintered at a temperature between about 900' C. to 
about 1200" C. for about 10 to about 30 minutes at about 
one atmosphere in a gas. 
18. A method of making a composite material as 
claimed in claim 17 wherein the compacted powders 
19. A method of making a composite material as 
claimed in claim 17 wherein the compacted powders 
are sintered in hydrogen gas. 
claimed in claim 2 wherein the blended powders are cold isostatically pressed at a teInperatUre Of about 25' 
cold compacted by cold isostatic pressing. 
of making a composite 6. A as 15 
in wherein the powders are ders are hot isostatically pressed at a temperature be- 
cold isostatically pressed at a temperature of about 25" 
C. and a pressure between about 40 Ksi to about 80 Ksi. 
claimed in claim 2 wherein the cold compacted POW- 
ders are sintered at a temperature of about 900" C. to 
about 1200" C. for about ten minutes to about thirty 
minutes in a gas at a pressure of about one atmosphere. 
claimed in claim wherein the cold compacted pow- 
ders are sintered in an inert gas. 
as 
claimed in claim 7 wherein the cold compacted pow- 30 are sintered in a inert gas. 
ders are sintered in hydrogen gas. 
10. A method of making a composite material as 
claimed in claim 1 wherein the blended powders are 
first cold compacted and then hot pressed. 
7. A method of making a composite material as 20 
A method Of making a 
* * * * *  
35 
40 
45 
50 
55 
65 
UNITED STATES PATENT AND TRADEMARK OFFICE 
CERTIFICATE OF CORRECTION 
PATENTNO. : 5,034,187 
DATED : J u l y  23, 1991 
INVENTOR(S) : Harol d E. SI i ney and Chri stopher De I I acorte 
It is certified that error appears in the above-identified patent and that said Letters Patent is hereby 
Column 4, lines 60 and  61, cancel "fluro-diest' a n d  insert--fluorides 
corrected as shown below: 
Signed and Sealed this 
First Day of December, 1992 
Attest: 
DOUGLAS B. COMER 
Attesting Oficer Acring Commissioner of Parents and Tmdemarks 


Method of making carbide/fluoride/silver composites

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