Wear protective coatings consisting of TiC–SiC–a-C:H deposited by magnetron sputtering

Hard coatings of the composition TixSiyCz which consist of TiC, TiSix, a-SiC and a-C:H, have been deposited with the aim of depositing self-lubricating Ti3SiC2. The films were prepared by reactive unbalanced magnetron sputtering from elemental titanium and silicon targets in the presence of argon and acetylene. The coatings are composed of nanocrystalline TiC and, depending on the composition, of titanium silicides, amorphous hydrogenated carbon and amorphous silicon carbide. Nanohardness values of up to 30 GPa could be obtained for coatings with friction values below 0.25 against steel in an unlubricated pin-on-disk setup. Low friction coefficients against steel were measured for higher concentrations of amorphous carbon at hardness values of approximately 15 GPa. In contrast to coatings composed of titanium, silicon and nitrogen, the hardness maximum is observed at TiC grains sizes of 25 nanometers.