Thermal Stability of TiAlN and Nanocomposite TiAlSiN Thin Films

TiAlN and TiAlSiN coatings were synthesized by a cathodic arc deposition process. Titanium, Ti₅₀Al₅₀ alloy and AlSi (88 at.% of Al and 12 at.% of Si) alloy targets were adopted as the cathode materials. X-ray diffraction analyses revealed that Ti_0.5Al_0.5N and Ti₄₉Al_0.44Si_0.07N possess a B1-NaCl crystal structure. The lattice constants of the Ti_0.5Al_0.5N and Ti_0.49Al_0.44Si_0.07N calculated from XRD pattern were 0.418 nm and 0.422 nm, respectively. For the high temperature oxidation test, the coated samples were annealed at 900 °C in air atmosphere for 2 hours. In this study, the deposited Ti_0.5Al_0.5N had completely transformed to TiO₂ and Al₂O₃, and Ti_0.49Al_0.44Si_0.07N remained the as-deposited structure after oxidation treatment. It indicated that Ti_0.49Al_0.44Si_0.07N possesses superior oxidation resistance than Ti_0.5Al_0.5N, due to the amorphous SiNx phase existed in the nanocomposite structure. The different oxidation mechanisms of Ti₅₀Al₅₀N and Ti_0.49Al_0.44Si_0.07N at high temperature of 900 °C are developed in this study.