Effect of low-temperature oxidation on the properties of TiVN/VN multilayer coatings

An extensive study of the surface oxidation process on the properties of TiVN/VN multilayer coatings deposited by RF magnetron sputtering on Mg alloys was performed. TiVN/VN multilayer coatings with a total thickness of 660 nm and different layer numbers of 5, 11, and 33 were oxidized by annealing at 450K under partial oxygen pressure. Electronic, mechanical, and tribological properties of these coatings were characterized by X-ray photoelectron spectroscopy (XPS), scanning electron microscope, nanoindentation measurements, and scratch tester. The experimental results showed that the oxidation of TiVN/VN multilayer coatings leads to better performance in terms of surface roughness, hardness, and wear. The hardness of the coating increased significantly (up to 1400 HV) with the oxidation of the surface due to the release of stresses between each layer after in situ annealing. The decline of the friction coefficient after oxidation can be attributed to the formation of a self-lubricating V2O5 layer on the surface, the presence of which was confirmed by XPS. The findings in this work reveal a new technique for applying a better thin film coating for industrial applications of Mg alloys.