Enhanced High Temperature Corrosion Resistance of Al 2 O 3 /Al Composite Coating on γ -TiAl Alloy

Abstract γ-TiAl specimens were coated with an Al2O3/Al composite coating using magnetron sputtering. The corrosion resistance of the coated specimens was investigated in molten salt environment of 100 wt% Na2SO4 at 850 °C. Results show that the Al2O3/Al composite coating improves the high temperature corrosion resistance of γ-TiAl alloy effectively. The good resistance is attributed to the gradient structure of Al2O3/Al composite coating which consists of an Al2O3 top-layer, an Al-rich interlayer and a diffusion layer. The results of corrosion test reveal that the Al2O3, TiO2 and TiAl3 are identified as the main phase structure of the corroded coating surface. Moreover, the sealed coating structure could effectively suppress the erosion of O2-, S2- and Na+, while Al2O3/Al coating with gradient structure exhibits superior crack and spallation resistance.