Influence of composition and structural properties in the tribological behaviour of magnetron sputtered Ti–Si–C nanostructured thin films, prepared at low temperature

Within the frame of this work, low temperature Ti–Si–C films were deposited on high-speed steel and stainless steel substrates by combined dc/rf magnetron co-sputtering. Composition analysis revealed the existence of two distinct regions: (i) a silicon doped sub-stoichiometric titanium carbide zone and (ii) a titanium rich zone. Structural analysis confirmed the different nature of the prepared films within each of the two zones. The residual stress states (σr) were relatively low, and the hardness values ranged between 11 and 27 GPa, with a dependence on the composition as well as on the structural features. The tribological results showed quite similar trends, with both friction coefficients and wear revealing a straight correlation with the composition, and consequently, the different structural arrangements. In general terms, the obtained results showed that the friction coefficient of the samples tended to decrease with increasing CC/CSi atomic ratio, indicating an improvement in tribological behaviour for the samples with the highest carbon contents. In terms of wear resistance, the films with a stoichiometry very close to TiC, Si doped sub-stoichiometric titanium carbide films, presented the best behaviours, revealing that a compromise between the best friction and wear, must be made in order to select the optimum coating.