Effects of silicon and multilayer structure of TiAl(Si)N coatings on the oxidation resistance of Ti6Al4V

For improvement of the oxidation resistance of the titanium alloy, multi-layered Ti0.5Al0.5N/Ti0.7Al0.3N and monolayer Ti0.5Al0.5N, Ti0.5Al0.45Si0.05N, Ti0.6Al0.3Si0.1N were deposited on Ti6Al4V alloy by arc ion plating. The isothermal and cyclic oxidation behaviors of the coated alloy were investigated at 650 °C and 750 °C in air. At 650 °C the oxidation resistance of the substrate was significantly improved by all the coatings. At 750 °C, the beneficial effects were maintained by Ti0.6Al0.3Si0.1N and Ti0.5Al0.45Si0.05N but not by Ti0.5Al0.5N and Ti0.5Al0.5N/Ti0.7Al0.3N coatings. The TiAlSiN coating exhibited better oxidation resistance than the TiAlN coating could be attributed to Si addition eliminating defect formation in the TiAlN coating during the oxidation process.