Tribological behavior of sliding diamond-like carbon films under various environments

Abstract

Tribological behaviors of amorphous diamond-like carbon (DLC) films were experimentally evaluated under various environments using a steel ball-on-disk wear-rig at dry sliding surfaces. The DLC films were prepared on Si wafer by r.f. PACVD method using benzene (C 6H 6). Every test was performed under the normal load 4.9 N and sliding velocity of 0.05 m/s, and the coefficients of friction of DLC films were measured with the contact cycle. When the test was performed under a vacuum, the coefficient of friction of DLC films showed a significant fluctuation with the contact cycles, remarkably accompanied with roll-shaped polymeric wear debris. Another test using thermally-baked DLC films showed that the friction was lower and more stable. Under a humidity controlled air, friction of DLC films was also stable. Tests with dry O 2 and N 2 gas were extended to find any other environmental factors which could affect the tribological behavior of DLC films. It was found that tribological behavior of DLC films was dependent on the formation of friction layers which were mainly affected by the environment. In the final discussion of this work, effects of environment on the tribological behavior of DLC films were combined and discussed in terms of tribo-chemistry of DLC films.