Hot corrosion of modified Ti3Al-based alloy coated with thin Na2SO4 film at 910 and 950 °C in air

The hot corrosion behaviour of a modified Ti3Al-based alloy under thin Na2SO4 deposit film was investigated at 910 and 950 °C in air. The corrosion product was identified by XRD and its morphologies on the surface and cross-section were observed by SEM. The alloy suffered from considerable hot corrosion attack. The mass gain versus time curves obtained by TGA exhibited two regions of different kinetics. The whole corroded layer consisted of loose and porous mixture oxides of TiO2, Nb2O5 and Al2O3. Numerous small nodules of corrosion product were observed. An illustrative schematic was established to describe the formation process of such nodules. It seemed that the refractory oxides played a significantly important role in determining the development of hot corrosion attack.