Tribocorrosion and tribological behavior of Ti-DLC coatings deposited by filtered cathodic vacuum arc

In order to improve the tribological and tribocorrosion performance of Ti-DLC films, a series of Ti-DLC films were prepared by filtered cathodic vacuum arc technique by controlling C2H2 flow rate. The microstructure, mechanical properties, tribological and tribocorrosion performance of Ti-DLC films with different C2H2 flow rates were investigated. As the C2H2 flow rate increased from 10 to 140 sccm, the columnar cross-sectional structure of the Ti-DLC films transformed to dense and uniform structure. The increase in C2H2 flow rate also resulted in an initial increase followed by a decrease in hardness and compressive stress. The results showed that the Ti-DLC films on substrate can significantly improve its tribology, anti-corrosion and anti-tribocorrosion properties. Under dry friction condition, the film prepared at 20 sccm with hardness of 49.1 GPa showed low wear rate at a reciprocating frequency of 1 Hz under a load of 2 N (2 N/1 Hz), however, the film was worn through due to the high compression stress at 10 N/5 Hz. The film at 140 sccm showed great tribology performance with the lowest coefficient of friction of 0.017 and the lowest wear rate of 5.91 × 10−8 mm3/N·m at 10 N/5 Hz, which was attributed mainly to the formation of sp2-carbon rich transfer layers on the counterpart. The tribocorrosion properties test demonstrated that the coating prepared at 140 sccm exhibited the best tribocorrosion resistance with the lowest coefficient of friction of 0.055, the lowest wear rate of 3.56 × 10−7 mm3/N·m and high stable value of OCP of 0.116 V under the synergistic action of corrosion and friction.