Effect of Ta content on high temperature oxidation and hot corrosion resistance of DZ411 superalloy

In order to elucidate the mechanism of the effect of Ta content on the high temperature behaviour of the alloys, the high temperature oxidation and thermal corrosion experiments were carried out on the three alloys with different Ta contents (2.72, 3.10 and 4.00 wt.%). The results of high temperature oxidation and hot corrosion show that because Ta has a higher valence state than Al, it can reduce the indiffusion of O, and the rate at which Ta diffuses within the alloy matrix is relatively slow since it has a larger atomic radius. As a result, the diffusion of the Al element is inhibited as the Ta content increases. Therefore, adding Ta inhibits the formation of Al₂O₃ in the surface oxide and promotes the formation of Cr₂O₃. Thus, Ta promotes oxidised film growth on the sample surface, which inhibits the diffusion of S, O and other elements into the matrix. Additionally, Cr₂O₃ is not easy to dissolve in molten salt, which ultimately makes the alloy have high oxidation resistance and thermal corrosion resistance.