Tribological behavior of DLC/IL solid–liquid lubricating coatings in a high-vacuum condition with alternating high and low temperatures

In this paper, ionic liquid (IL) diamond-like carbon (DLC)-based solid–liquid lubricating coatings were used to conduct friction and wear experiments under a high-vacuum condition with alternating temperatures between −100 and 150 °C. The results showed that the friction coefficients at 100 and −100 °C were the lowest and the largest, respectively. Considering that the mobility, activity, spreadability, and self-repairing capacity of IL were significantly better at high temperatures compared with those at low temperatures, the DLC film surface slightly graphitized at a relatively high temperature. The disc wear rates were the lowest at room temperature and the highest at 150 °C because the surface graphitization of the DLC film and the large friction coefficient resulted in an increase in wear rate.