Improving hot corrosion resistance of aluminized TiAl alloy by anodization and pre-oxidation

Abstract

To shield TiAl alloy from hot corrosion attack, a compact protective coating was fabricated by the combination of aluminizing, anodization and pre-oxidation. The hot corrosion behavior of the coated-TiAl specimen was investigated in the mixture salt consisting of 75 wt.% Na2SO4 and 25 wt.% NaCl at 700 °C. Results indicated that the anodization and pre-oxidation were beneficial to the generation of Al2O3 layer, which could act as a diffusion barrier to prevent the molten salts and oxygen from diffusing into the alloy during exposure to a hot corrosion environment while the aluminizing coating could provide sufficient aluminum source to support the continuous formation of Al2O3 layer. Moreover, the internal stress of the coating was reduced due to the formation of a gradient coating consisting of TiAl3 and TiAl2.