FRICTION AND WEAR BEHAVIOR OF AMORPHOUS HYDROGENATED SI1-XCX FILMS

Amorphous hydrogenated Si1-xCx films (a-Si1-xCx:H) (x = 0.65-1) were deposited by r.f. plasma-assisted chemical vapour deposition. Their friction and wear properties were investigated with the help of a conventional ball-on-disk apparatus. These results are correlated with chemical (Si to C atomic ratio), structural (laser Raman spectroscopy) and mechanical (internal stress, hardness and elastic modulus) properties. With increasing silicon content, the film material evolves from diamond-like carbon (DLC) to amorphous SiC-like material. Simultaneously, the values for hardness, elastic modulus and internal stress are reduced by 15% 30%. For a low normal load (1 N) in the ball-on-disk test, a-Si1-xCx:H films (0.7 < x <0.9) show a very low wear rate of both the film and the counterbody, combined with a steady state low friction coefficient of 0.05 in a humid ambient atmosphere. For the higher loads (5 and 10 N), however, this low friction coefficient lasts for only a relatively short time. In this case, the harder DLC films perform tribologically better because of their higher wear resistance, low wear rate of the counterbody and generally low friction coefficient between 0.15 and 0.35 in a humid ambient atmosphere.