Investigation of (Ti,V)N and TiN/VN coatings on AZ91D Mg alloys

• Higher oxygen contamination was found in Ti containing layers by means of XPS.
• Oxygen diffusion from the substrate surface affected the stoichiometry of coatings.
• Corrosion resistance is correlated with the roughness of coating surfaces.
• TiN, TiVN and TiN/VN coatings were characterized by nanoindentation tests.
• Highest hardness and adhesion strength were obtained from the TiVN coating.

In this study, TiN, TiVN and TiN/VN thin films were coated on AZ91D magnesium alloys using RF magnetron sputtering technique and the influence of these coatings on the structural and mechanical properties of Mg alloys was investigated. The composition, surface morphology, corrosion resistance, mechanical and tribological properties of the coatings were analyzed by x-ray photoelectron spectroscopy (XPS), atomic force microscope (AFM), electrochemical measurements, nano hardness tester and scratch tester, respectively. XPS results showed that at the early stages, oxygen diffusion from the substrate surface affected the stoichiometry of nitride coatings. XPS analysis also revealed the existence of a small amount of oxygen in TiN layers. Surface roughness, corrosion resistance and adhesion strength were all improved significantly with the incorporation of V into the coatings. While the corrosion behaviors of TiVN and TiN/VN multilayer coatings deposited at the same sputtering power are similar, the average hardness and adhesion strength of the TiVN coating were higher.