Powder mixture suitable for sintering to form a self-lubricating solid material
View Patent ↗The invention relates to a novel self-lubricating solid material; to a method of preparing such a material from a powder mixture; to said powder mixture; and to mechanical parts made of said novel material. Said powder mixture comprises a powder of a metal alloy that is a precursor for the matrix of said material, particles of a first solid lubricant such as CeF 3 that are for insertion in said matrix without reacting with said metal alloy, and particles of a second solid lubricant such as WS 2 or MoS 2 for reacting with a component of said metal alloy during sintering of the powder to form a lubricating phase. Said material can be used for fabricating a bushing that is to receive a root of a variable-pitch vane of an airplane turbojet compressor.
1. A powder mixture suitable for sintering to form a self-lubricating solid material, the mixture comprising:
a metal alloy powder that is a precursor for a matrix of the self-lubricating solid material;
particles of a first solid lubricant comprising cerium trifluoride CeF 3 ; and
particles of a second solid lubricant;
wherein:
when the powder mixture is sintered, the first solid lubricant is incorporated into the matrix without reacting with the metal alloy; and
when the powder mixture is sintered, the second solid lubricant reacts with a component of the metal alloy to form a lubricating phase.
2. The powder mixture according to claim 1 , wherein the first solid lubricant is present in the mixture in an amount of about 15% volume or less.
3. The powder mixture according to claim 2 , wherein the first solid lubricant is present in the mixture in an amount of from 5% to 10% by volume.
4. The powder mixture according to claim 1 , wherein the second solid lubricant is present in the mixture in an amount of about 15% by volume or less.
5. The powder mixture according to claim 4 , wherein the second solid lubricant is present in the mixture in an amount of from 5% to 10% by volume.
6. The powder mixture according to claim 1 , wherein the first solid lubricant and the second solid lubricant are present in the mixture in a combined amount of greater than 10% by volume.
7. The powder mixture according to claim 1 , wherein the second solid lubricant comprises tungsten disulfide WS 2 or molybdenum disulfide MoS 2 .
8. The powder mixture according to claim 1 , wherein the lubricating phase comprises at least one sulfur compound of hexagonal structure.
9. The powder mixture according to claim 1 , wherein the metal alloy comprises an alloy based on iron, nickel, or cobalt.
10. The powder mixture according to claim 1 , wherein:
the component of the metal alloy is chromium; and
the lubricating phase comprises Cr 7 S 8 .
11. The powder mixture according to claim 1 , wherein:
the second solid lubricant comprises tungsten disulfide WS 2 or molybdenum disulfide MoS 2 ;
the component of the metal alloy is chromium; and
the lubricating phase comprises Cr 7 S 8 .
12. A powder mixture according to claim 11 , wherein:
the first solid lubricant is present in the mixture in an amount of from 5% to 10% by volume;
the second solid lubricant is present in the mixture lies in an amount of 5% to 10% by volume; and
a sum of the amounts of the first and second solid lubricants is greater than 10% by volume.
13. A method of preparing a self-lubricating solid material, comprising:
preparing the powder mixture according to claim 1 ;
intimately mixing the mixture;
adding a binder to the resulting intimate mixture;
molding the intimate mixture by pressing or injection in a mold to form a blank;
extracting the molded blank from the mold;
evacuating the binder; and
densifying the blank by sintering.
14. A self-lubricating solid material, comprising:
a matrix of a metal alloy;
particles of cerium trifluoride CeF 3 as a first solid lubricant inserted in said matrix; and
a lubricating phase;
wherein:
the particles of the first solid lubricant are present in the matrix but do not react with the metal alloy;
the lubricating phase comprises a reaction product of a second solid lubricant and a component of the metal alloy; and
the lubricating phase comprises a sulfur compound of hexagonal structure.
15. The self-lubricating solid material according to claim 14 , wherein the metal alloy comprises an alloy based on iron, nickel, or cobalt.
16. The self-lubricating solid material according to claim 14 , wherein the sulfur compound of hexagonal structure comprises Cr 7 S 8 .
17. A mechanical part made from the material according to claim 14 .
18. The mechanical part according to claim 17 , consisting of a bushing for receiving a root of a variable-pitch vane of an airplane turbojet compressor.