Isothermal Oxidation Behavior of TiN Coatings Deposited by Closed Field Unbalanced Magnetron Sputtering

TiN coatings were successfully prepared by closed field unbalanced magnetron sputtering (CFUBMS) in this study. The microstructure, composition, phase structure, hardness and adhesion of TiN coating were investigated by SEM, EDS, XRD, and nanoindentation/scratch techniques, respectively. Emphatically, the oxidation behaviors of TiN coating were analyzed and discussed at 550, 600 and 650°C, respectively. Results showed that TiN coatings are golden with loose pyramidal structure, and the phases in TiN coating are mostly TiN and a small amount of Ti. The hardness, elastic modulus and bonding strength of TiN coating are about 23 GPa, 288 GPa and 35 N, respectively. The isothermal oxidation tests in a thermal analyzer at 550°C and 650°C for 19 h suggested that TiN coating has better oxidation resistance at 550°C because it was approximately intact at 550°C. However, the oxidation experiments in a muffle furnace at 600°C and 650°C for only 10 h indicated that TiN coatings were slightly oxidized. Therefore, above 600°C, TiN coating will fail due to the formation of the brittle rutile TiO₂ as the oxidation time increases. (paper)