Microstructure, oxidation behavior and tribological properties of AlCrN/Cu coatings deposited by a hybrid PVD technique

Achieving high hardness and low friction at elevated temperatures for nitride-based hard coatings has substantial scientific interest and application significance.In this study,Al Cr N/Cu coatings were deposited by a hybrid PVD technique combining arc evaporation from an AlCrtarget and magnetron sputtering from a Cu target in a mixed Ar and Natmosphere.The microstructure,oxidation behavior,and tribological properties of the coatings were investigated.Al Cr N/Cu coatings show a dual-phase structure of (Al,Cr)N solid solution and Cu metallic phase.Excessive sputtering power of the Cu target induces the disintegration of interlayer interfaces of the nano-multilayered geometry,accompanied by a decline in hardness from above 30 GPa to 22.7 GPa.Moreover,the formation of fine Cu O grains on the coating surface is conducive to reducing the friction coefficient of Al Cr N/Cu when exposed to air at high temperatures.The Al Cr N/Cu coating with a sputtering power of 0.5 k W obtains a friction coefficient of 0.39±0.05 after pre-oxidation at 800°C,distinctly lower than that of Al Cr N,which exhibits a friction coefficient of～0.65.The further transformation of Cu O to cubic Cu(Al,Cr)O,which stems from the solid-state reaction of Cu O,AlO,and CrO,would cause a rise in friction coefficient and wear loss.The mechanism of oxidation and tribological behavior of the Al Cr N/Cu coatings related to the temperature and Cu content was discussed.