Improving oxidation resistance of γ-TiAl based alloy by depositing TiAlSiN coating: Effects of silicon

To improve oxidation resistance of γ-TiAl based alloys, Ti0.5Al0.4Si0.1N coating was deposited on Ti48Al2Cr2Nb alloy by arc ion plating system. Ti0.5Al0.5N coating was also deposited for comparison. TiAlSiN coating exhibited excellent cyclic oxidation resistance at 900 °C mainly due to Si promoted selective oxidation of Al and formation of a continuous Al2O3 top layer in oxide scale. Another beneficial effect of Si is promoting in situ formation of Ti5Si3 diffusion barrier layer at coating/substrate interface during thermal exposure, which inhibited interdiffusion between coating and alloy, especially nitrogen inward diffusion in alloy and helped the coating maintaining long term oxidation resistance.