TRIBOLOGICAL CHARACTERISTICS OF SYNTHESIZED DIAMOND FILMS ON SILICON-CARBIDE

The purpose of this research was to explore the use of synthesized diamond films as wear-resistant, low friction materials for tribological applications. The friction and wear of diamond-coated SiC sliding against SiC were studied. The diamond films were deposited by means of the hot filament chemical vapor deposition process. A ball-on-three-flat contact geometry was used in the wear experiments. The experimental results showed that the wear rate of SiC disk specimens was reduced by four orders of magnitude when they were coated with a diamond film. Similarly, the friction coefficient was reduced by almost one order of magnitude. Energy-dispersive X-ray analysis of the worn surface of the diamond indicated that the SiC counterface undergoes tribochemical reactions with the air atmosphere, producing silicon oxide. It is suggested that the low friction coefficient of diamond may be related to the formation of a thin film of graphite at the real area of contact. Wear of the diamond film is then accounted for by the loss of this graphite layer.