Tribological performance of mechanically lapped chemical vapor deposited diamond coatings

Polycrystalline diamond layers were deposited onto the titanium alloy Ti-6A l-4V via microwave plasma chemical vapor deposition (CVD). It is shown that the diamond film reduces wear and friction immensely compared with uncoate d titanium/titanium tribe systems. An additional polishing process of the C VD-diamond layer improves the wear behavior even further. An influence of a ir humidity is found. In addition, different ceramic materials (Al2O3, SiC, Si3N4, ZrO2) were tes ted against as-deposited and polished CVD-diamond layers. Al2O3 and Si3N4 e xhibit very good wear behavior accompanied by very low friction against as- deposited CVD-diamond. SiC and ZrO2, however, show somewhat inferior wear a nd friction behavior. Suggestions are made to explain the different perform ance. Again, a wear increase is found with increasing humidity. Polishing o f CVD-diamond layers improves the tribological performance further. (C) 199 9 Elsevier Science S.A. All rights reserved.