Corrosion mechanism of γ-TiAl alloy at high temperature in molten salt environment

The high temperature corrosion tests of Ti-48Al-2Cr-2Nb γ-TiAl alloy were carried out with salt mixture of 75% Na₂SO₄ and 25% NaCl (mass fraction) at 800°C. The high temperature corrosion behavior of the alloy and the selective corrosion mechanism of microstructure were also discussed, via oxidation kinetics analysis, scanning electron microscope observation and X-ray diffraction analysis. The results show that the oxide layer mainly composed of TiO₂ and Al₂O₃ is formed during high temperature corrosion. The corrosion path initiates at the lamellar interfaces, and α₂ phases as well as some substructures in γ phase have priorities of corrosion in molten salt environment, which proves the existence of the selective corrosion of lamellar structure. The difference in oxidation resistance between the two phases and the participation of molten salts in intermediate reaction, which accelerates the oxidation process, are considered as the main reasons of selective corrosion of microstructure in the alloy.