Assessment of thermomechanical stability of DLC films deposited by Ne-HiPIMS technology for high-temperature applications

Enhancement of the thermomechanical stability of diamond-like carbon (DLC) coatings is highly demanded by the automotive industry due to graphitization at higher temperatures. This work is devoted to the assessment of the thermomechanical stability of annealed DLC films deposited by increasing Ne up to 50% in high-power impulse magnetron sputtering (HiPIMS) plasma, followed by the evaluation of their tribomechanical properties. The tribological performance of the films was assessed by room-temperature tribological tests after annealing the films, and by high-temperature tribological test at 300 C-degrees in ambient atmosphere. The microstructure and chemical compositions of the films were analyzed, and the hybridization state of the annealed films was determined by x-ray absorption near-edge spectroscopy (XANES). The wear mechanism involved in both high-temperature and annealed films tribological tests with the steel counterpart was the combination of abrasion and adhesion. It was observed that all the films demonstrated stable tribomechanical performance by annealing up to 500 C-degrees, while from 600 C-degrees, the film deposited in pure Ar plasma demonstrated poor tribomechanical performance. In contrast, increasing Ne to 50% in plasma led to an increase in the thermomechanical stability of DLC films to more than 700 C-degrees, and resisting graphitization up to 800 C-degrees.