Effects of additional oxygen on the structural, mechanical, thermal, and corrosive properties of TiN coatings

In this study, the influence of additional oxygen on the structural, mechanical, thermal, and corrosive properties of TiN coatings was investigated. A progressive change occurred in the structure from cubic TiN, Ti0.50O0.11N0.39, Ti0.46O0.15N0.39, and Ti0.44O0.28N0.28 to mixed cubic and monoclinic Ti0.39O0.40N0.21, and finally to tetragonal TiO2. Doping oxygen into TiN led to a significant change in hardness owing to the solid solution strengthening effect and the formation of ionic bonds and oxide phases. Ti0.46O0.15N0.39 exhibited the highest hardness of ∼28.8 GPa. The addition of oxygen weakened the thermal stability of the TiN coating owing to the production of more oxides during annealing. After oxidation at 600 °C for 10 h, the Ti0.50O0.11N0.39 coating with an oxide thickness of ∼0.86 μm exhibited an excellent oxidation resistance. The TiO2 coating was not oxidized, thereby maintaining the initial morphology. In addition, the corrosion resistances of the TiON coatings were closely related to the oxygen content, where the low oxygen content compound Ti0.50O0.11N0.39 exhibited the best corrosion resistance.