Mechanical and tribological behaviors of Ti-DLC films deposited on 304 stainless steel: Exploration with Ti doping from micro to macro

Diamond-like carbon (DLC) films with different Ti doping contents from micro amount to a relatively macro level on a 304 stainless steel substrate were prepared by ion beam assisted enhanced unbalanced magnetron sputtering. The evolution of microstructure, mechanical and tribological behaviors of DLC and Ti-DLC films were systematically investigated, and the wear mechanism of the films with different Ti doping stages was also contrastively discussed. Results revealed that the mechanical behaviors of the Ti-DLC films with micro Ti doping content (1.82 wt%) exhibit a better performance than those of pure DLC film and Ti-DLC films with a relatively macro Ti doping content, which can be attributed to the change of C-C sp(3) bond content. The suitable size and content of TiC nanocrystallites can regulate the carbon matrix and improve the tribological behaviors of the film. While when the larger and more TiC nanocrystallites gradually form with the increased Ti doping content, the 3D structure of the carbon matrix and the surface smoothness could be destroyed and much more TiC involved in the friction process resulting in the high and fluctuating friction coefficients of the Ti-DLC films.