CHEMICAL AND TRIBOLOGICAL STUDIES OF MOS2 FILMS ON SIC SUBSTRATES

The lubrication of ceramic surfaces is vital to permit the use of ceramics in many types of moving mechanical assembly. This paper reports the results of pin-on-flat friction and wear studies conducted in vacuum on lubricating MoS2 films that were r.f. sputter deposited onto hot-pressed SiC coupons pretreated to alter available surface bonding sites. Pretreatment consisted of chemical etching with HF and HNO3, which removed surface active sites for MoS2 adhesion. Films grown on etched surfaces have shorter wear lives and lower initial friction than similar films grown on non-etched surfaces. The surface chemical interactions of SiC with molybdenum, sulfur and oxygen were also briefly examined using X-ray photoelectron spectroscopy. SiC was observed to form strong bonds with all three species; molybdenum had an interfacial reaction, while sulfur and oxygen competed for strong surface bonding sites.