TRIBOLOGICAL PROPERTIES OF SMOOTH POLYCRYSTALLINE DIAMOND FILMS

We have used a pin-on-disk tribometer with either a monocrystalline ruby or a 100Cr6 steel ball to evaluate the tribological properties of a series of polycrystalline chemical vapour deposition diamond films. Different polishing treatments of the as-grown films resulted in marked differences of their tribological behaviour. The friction and wear of smooth nanocrystalline diamond films was dependent on the surface morphology and roughness as well as the material transfer from the ball to the film. Microcrystalline films polished by laser irradiation, though being substantially rougher, showed a lower friction and minimal ball wear. Films polished by Ar-microwave plasma etching showed a similar behaviour as the laser-irradiated samples. However, the him with roughness comparable with the laser polished samples produced significantly higher ball wear. An unrivalled tribological performance was obtained with mechanically polished diamond films.