Tribological characteristics of diamond-like films deposited with an arc-discharge method

Using an arc-discharge method, we deposited a diamond-like carbon film 600 nm thick on hardened steel. Characterization of the film was carried out with Raman spectroscopy. In dry sliding wear and friction tests, with a hardened steel pin as a counterpart, we obtained a friction coefficient between 10 000 and 20 000 cycles, with the maximum value of 0.18. The value decreased to 0.12 after about 100 000 cycles. We obtained a wear coefficient of 7 × 10^-17 m³/mN. A transfer layer formed on the pin during sliding and probably had the dominating effect on the tribological behavior. We observed in nanoindentation measurments that the film softened in a wear track during the first 20 000 cycles. Although fracture pits on the wear track occurred, fracture is not the dominant failure mechanism of these films. Degradation of good tribological properties was caused mainly by partial wear-through of the film after 370 000 cycles and by a subsequent redeposition of the transfer film on the wear track during prolonged sliding.