Tribo-mechanism of amorphous carbon films under corrosion solution and various mechanical loads

Abstract Diamond-like carbon films (DLC) as a prominent surface protection coating are used to enhance the tribological performance of engineering components due to their low coefficient of friction (COF), high wear resistance and excellent chemical stability. In recent years, researchers have separately studied the environment-dependent and load-dependent tribological behaviors of DLC films. However, there is few studies about the influence of corrosive media on the load-dependent tribological behaviors of DLC films. In this paper, we explained the tribo-mechanism of chromium doped DLC film (Cr-DLC) in hydrochloric acid (HCl) by combing the effect of load-dependent. For comparison, tribological behaviors of Cr-DLC films in ambient air and distilled water environment were also investigated. It is found that the coefficient of friction of Cr-DLC film complies with the Hertzian elastic contact model in HCl solution. In other words, the COF decreases with the increase of normal contact load except 2 N. The Cr-DLC film shows the highest wear resistance with wear rate of 1.79 × 10−7 mm3/Nm at 5 N. The main wear mechanism at 2 N and 5 N is governed by the formation of a graphite-like transfer film and tribochemical products on friction interfaces; Whereas the wear mechanism for 7 N and 10 N contact load is attributed to the superimposed effect of the high Hertzian contact stress and the corrosion function of chloride ion. The insights acquired from this study can be used to the design of high-performance of DLC coated tribo-systems in corrosive environment.