ANTI-WEAR PERFORMANCE OF POLISHED MICROCRYSTALLINE DIAMOND FILMS SLIDING AGAINST Si3N4 UNDER WATER LUBRICATION

In this work, aiming at enhancing the tribological behavior of chemical vapor-deposited (CVD) diamond and Si3N4 tribo-pair, mechanical polishing is performed on CVD microcrystalline diamond (MCD) films. The tribological performance of as-fabricated polished MCD (MCD-p) films is investigated by ball-on-plate reciprocating friction tests with Si3N4 ceramic balls as the counterparts under water lubrication, where the as-grown MCD films, nanocrystalline diamond (NCD) films and Si3N4 ceramic plate are employed as the contrast specimens. Under a normal load of 10 N and at a reciprocating frequency of 30 Hz for 2-mm distance, the as-fabricated MCD, NCD and MCD-p films exhibit similar steady friction coefficients after run-in state, which are 0.036, 0.032 and 0.035, respectively. Nevertheless, the wear rate of Si3N4 counterparts varies. Due to the plowing effect of as-grown MCD and NCD films, severe abrasion of Si3N4 counterparts can be observed after sliding for 20[Formula: see text]min. For the MCD-p specimen, however, the Si3N4 counterpart exhibits 2–3 orders of magnitude lower wear rate than those sliding against the as-grown MCD or NCD specimen. On the other hand, due to the reciprocating motion failing to form fluid film between the contact surfaces, high friction coefficient (0.092) and rather severe abrasion are observed for the self-mated Si3N4 ceramic contact.