Tribological characteristics of polycrystalline diamond films produced by chemical vapor deposition

Abstract

Effects of surface roughness and crystallinity of polycrystalline diamond films on their tribological characteristics, as well as the effects of test environment, have been investigated. Friction and wear characteristics of the diamond films deposited on sintered SiC disks have been examined with a ball-on-disk tester in the absence of any lubricant. The friction coefficients of polished diamond films against SiC and Si₃N₄ balls were below 0.10 at room temperature while those of as-deposited films were around 0.20. The specific wear of counterparts on the polished film was five orders of magnitude smaller than on the as-deposited film. The friction coefficient between the polished diamond film and a AISI 52100 steel ball was about 0.20. Transfer of a small amount of AISI 52100 material to the diamond film was observed along the wear track of the polished diamond surface. Diamond films of high quality were more resistant to wear than the ones of low quality. On the other hand, the friction coefficients were not affected by the crystallinity of the diamond films in the present study. Tribological characteristics of the diamond films deteriorated with increasing sliding speed and ambient temperature. At 600 °C in dry N₂, the friction coefficient of diamond films against a SiC ball was about 0.8, which was about ten times higher than that at room temperature in air.