Characterization of TiN coatings post-treated by metal-plasma ion implantation process

Abstract

Titanium nitride (TiN) coatings deposited by chemical (CVD) and physical vapor deposition (PVD) processes have been adopted for wear protection of cutting tools and various metallic components for years. To further extend the tribological performance of TiN layers, the metal-plasma ion implantation (MPII) process was used as an effective tool for surface enhancement of TiN coatings. Metal ions can be implanted into TiN coatings to form ternary metal nitrides, displaced metal nitrides, or interstitial metal-atom inclusion compounds. In this study, the wear resistance of TiN coatings was improved by ion implantation of Al by MPII treatment. Analysis of the chemical state by XPS and the calculation of residual stress by XRD suggest that the implanted Al substitutes Ti in the TiN lattice sites, and forms binary AlN or ternary TiAlN compounds. The as-deposited TiN film showed a compressive stress of approximately −12.55 GPa, which was relaxed by the MPII treatment. The formation of AlN/TiAlN improves the wear resistance of TiN film by the reduction of residual stress in the coating. Al implantation enhances the oxidation resistance of TiN at the initial stage of oxidation. Weight gain as a result of the formation of TiO 2 occurred during oxidation. The initial oxidation kinetics follows parabolic behavior with k p=4.12 g 2 cm −4 s −1, higher than that of Al-implanted TiN.