Physical-mechanical and tribotechnical properties of titanium alloys with Ti–C–Mo–S gradient antifriction coatings

The results of comprehensive investigations of physico-mechanical and tribological properties of (α+β)-titanium alloys with Ti–C–Mo–S antifriction coatings using a coarse-grained VT14 alloy and a nanostructured VT6 alloy as examples are presented. The mechanisms of formation of physico-mechanical and tribological properties of titanium alloys with composite gradient coatings composed of Ti–C–Mo–S, which are deposited by low-temperature magnetron sputtering assisted by gas-discharge plasma treatment are revealed. A significant improvement of the properties of titanium alloys with these coatings is shown. It is found out that hardness of the coatings formed by plasma-assisted magnetron sputtering is higher compared to those deposited by conventional magnetron sputtering. Moreover, adhesion (bonding strength) of these coatings to the substrate is higher. Comparative tribological unlubricated friction tests demonstrated that the average friction coefficient decreased by a factor of 7.9–9.5 and the wear intensity of the surface layer decreased by 2–3 orders of magnitude.