Effects of C content on the microstructure, mechanical and tribological properties of TiAlSiCN coatings

The effects of C doping content on the microstructure, mechanical and tribological properties of TiAlSiCN coatings prepared by ion plating are systematically investigated. The results show that the grain is refined with the C content increases to 17.22 at.%, and the (111) and (200) planes present competitive growth, the high C content promotes the preferred orientation of the (200) planes. The hardness of the coating shows a tendency to increase first and then decrease, the coating with C content of 8.15 at.% achieve the highest hardness, while the elastic strain resistance H/E value decreases monotonically. Moreover, it is found that the amorphous carbon (a-C) structure is precipitated with C content above 12.51 at.%. The wear mechanism of the coating against the Si3N4 counterpart is adhesive, and the coefficient of friction (COF) of the coating decreases from 0.4 to 0.2. Thereinto, the reduction in COF is related to the Hertzian contact area as C content below 8.15 at.%. The COF further reduction is attributed to the generation of graphite lubricated structure. However, the wear rate shows first decrease and then increase. Therefore, the preferential C doping content can improve the mechanical and tribological properties of the coatings.