Friction and wear characteristics of cermet-type metal films at cryogenic temperatures

Abstract Many aerospace applications require wear surfaces to operate in cryogenic environments. Specific applications in the cryogenic regime require bearings and seals to operate at high speeds with heavy loads for relatively short periods, as in turbopumps, or at moderate speeds and loads, as in cooling system pumps. The purpose of this paper is to determine the friction coefficients and wear characteristics of sputter deposited WCCo and TiCNi alloys on Inconel 718 substrates cooled to 20 K. Composition of the deposited films was verified by energy dispersive analysis of X-rays. Wear characteristics were determined using a friction and wear test fixture which utilized a two-stage cryogenic refrigerator to cool the stationary member of the test couple. Wear results as determined by scanning electron microscopy showed the wear of TiCNi coatings to be abrasive and a function of surface finish. WCCo was shown to deform plastically as asperity peaks in the surface appeared to be burnished with minimal debris generation. Coating adhesion was verified by diamond scratch testing.