High Temperature Tribological Properties of Hydrogen-Free Si-DLC Films Using HiPIMS/DCMS Co-Deposition Technique

Silicon doped hydrogen-free diamond-like carbon (Si-DLC) films were prepared using a superimposed high-power impulse magnetron sputtering (HiPIMS) and direct current magnetron sputtering (DCMS) deposition system with anode layer ion source assistance. The composition, microstructure, and tribological properties of Si-DLC films doped with different Si content at elevated temperature (25~500 ℃) were systematically investigated. Raman and XPS were used to analyze the influence of Si doping amount on microstructure, chemical composition and tribological properties of the films before and after high temperature friction. The results showed that Si-DLC film displayed a typical amorphous structure. The proportion of sp³-C/sp²-C in the films gradually increased with the increase of Si dopant. Si atoms in Si-DLC films mainly combined with C and O atoms to form C-Si-C and C-Si-O bonds. The formation of Si-C bonds contributed to the reduction of the internal stress and the improvement of the film-substrate adhesion. At room temperature, Si-DLC coating had a low friction coefficient due to the formation of transfer film. At high temperature, the formation of Si-C bonds was propitious to improve the high temperature stability of Si-DLC film. In addition, the partial oxidation of Si-C bonds to Si-O-C bonds in the friction region enables the film to had both low friction and low wear at high temperature.