Effect of Cu content on high-temperature tribological properties and oxidation behavior of Al-Ti-V-Cu-N coatings deposited by HIPIMS

Ti-Al-V-N hard coatings have been widely explored for wear-resistant applications. Introducing soft metal copper (Cu) into hard coating is expected to further improve the tribological performance. Herein, the effect of Cu content on the high-temperature tribological properties and oxidation behavior of Al-Ti-V-Cu-N coatings was studied. With increasing Cu content, the oxidation resistance of the coatings decreased, and promoted the formation of CuO oxide by out-diffusion of Cu at elevated temperatures. At 500 °C, all the coatings exhibited high friction coefficients of 0.84–0.97 due to limited tribo-oxidation. At 600 °C, with increasing Cu content, the friction coefficient decreased from 0.90 to 0.45, and then rebounded to 0.54, which can be attributed to the decrease of AlVO4 phase and the presence of CuO phase. As Cu content increased above 10.7 at.%, a low wear rate of 10−16 m3/N·m was achieved due to the formation of V2O5 and CuO lubricating oxides on worn surfaces, and exhibited oxidation wear.