Improved corrosion resistance in CrN/CrTiSiN multilayer coatings on Ti6Al4V alloy via post-deposition annealing

The main focus of this research is to investigate the influence of air heat treatment on the structural and corrosion behaviour of CrN/CrTiSiN coating layers. This study is motivated by the need to enhance the long-term durability and reliability of Ti6Al4V alloy components, which are extensively used in biomedical implants, aerospace, and marine applications but are susceptible to corrosion and wear in aggressive environments. The primary objective is to correlate the annealing-induced microstructural and phase evolution with the electrochemical performance to identify an optimal treatment for maximizing corrosion protection. CAE-PVD equipment was employed to deposit CrN/CrTiSiN coating onto Ti6Al4V alloy. The coatings were subjected to heat treatment in air at temperatures ranging from 500 °C to 800 °C for 1 h. Characterization included XPS, XRD, TEM, FESEM, PDP, and EIS assays. The findings indicate that the heat treatment process resulted in the formation of new phases including Cr 2 N, Cr 2 O 3 , and SiO 2 . The coating's thickness was determined to be 3 μm, and no significant alterations in the coating's microstructure were detected following annealing. The output of the EIS and polarization tests revealed that the annealed sample exhibited a higher level of corrosion resistance compared to both substrate and as-deposited samples. The improved resistance can be attributed to the presence of Cr 2 N, Cr 2 O 3 , and SiO 2 microconstituents, as well as the high adhesion strength.