Effects of V and Cu codoping on the tribological properties and oxidation behavior of AlTiN coatings

Due to their high hardness and superior wear resistance, AlTiN coatings have been extensively investigated and used in the field of cutting tools. In this work, the effects of V and Cu codoping on the tribological properties and oxidation behavior of AlTiN coatings were studied. When the Cu content was increased (from 2.6 to 22.6 at.%) and V content decreased (from 16.7 to 2.7 at.%), the wear rates of Al–Ti–V–Cu–N coatings at RT and 300 °C both sharply increased from 10−15 to 10−14 m3/N·m due to reduced hardness and limited oxidation. At 600 °C, due to outward diffusion and oxidation of Cu, the Al26Ti14V3Cu22N35 coating exhibited the lowest friction coefficient of 0.5 and wear rate of 3.2 × 10−15 m3/N·m. The increase of V content reduced the oxidation resistance of the Al–Ti–V–Cu–N coatings, and the oxidation mechanism of the V-rich Al21Ti12V17Cu3N47 coating involved mainly the outward diffusion of elements Al, V, and Cu and the formation of mixed oxides AlVO4, V2O5, and CuO on the top layer. Increasing the Cu content promoted the outward diffusion and oxidation of Cu and the formation of a smooth top layer of CuO, contributing to excellent wear performance.