Influence of currents on tribological behavior of diamond-like carbon films

Abstract

The diamond-like carbon (DLC) film is vastly applied for low-friction protective films at contact sliding surfaces. This work reported the characteristics and tribological properties of DLC, Cu-doped DLC (Cu-DLC) film and Ti-doped DLC (Ti-DLC) film formed by unbalanced magnetron sputtering system and analyzed the frictional tests and the morphology of wear scars. The current intensity at the sliding interface was set to a constant value in the whole current circuit for exploring the influence of current, including 0 A, 0.5 A, 1 A, 1.5 A and 2 A. The results showed the friction coefficient of DLC film decreased from 0.12 to 0.06–0.08 and then increases rapidly to 0.26 when the current increased to 2 A. The change in trend of friction coefficient of Cu-DLC film with the increase in current was the same with the DLC film. The minimum value was 0.12 at 1 A current. In the case of Ti-DLC film, when the current intensity enhanced from 0 to 2 A, the friction coefficient monotonically increased from 0.06 to 0.29. Furthermore, the wear rate of the films under higher current was larger than the wear rate of the films under lower current. This is due to the fact that frictional heat and Joule heat are generated at a relatively large current to make the surface of the film more susceptible to wear. The wear rate of Ti-DLC film is relatively larger as the arc ablation is the main wear mechanism of Ti-DLC film compared with pure DLC film and Cu-DLC film.