Effect of carbon content on the tribological behaviour of TiCx coatings prepared by reactive HiPIMS

Titanium carbide coatings exhibit a variety of tribological properties depending on their carbon concentration. In the present article, a series of coatings with compositions ranging from pure Ti to high carbon nc-TiC/a-C:H nanocomposites are deposited using high-power impulse magnetron sputtering, HiPIMS. The coatings were wear-tested using a ball-on-disk tribometer under different applied loads, and the resulting wear tracks were analysed by Raman spectroscopy. It is observed that the coefficient of friction and wear resistance improve with increasing carbon content. Furthermore, Raman spectroscopy confirms a graphitization at the sliding contact, and shows that the increase of the applied load leads to the enlargement of the sp ² clusters size which explains the self-adaptive behaviour observed during the sliding experiments. Intriguingly, the elasticity index “H/E" does not correlate with the wear rate results. A modified model that takes into consideration the content ratio of the amorphous carbon phase is herewith suggested. The Model better fits the obtained experimental results and predicts the wear behaviour more effectively.