Revealing the effect of Al content on the oxidation of γ'-strengthened cobalt-based superalloys

The effect of Al content (6–9 at%) on the oxidation of multicomponent γ'-strengthened cobalt-based superalloys at 800 ℃–1000 ℃ was revealed by combining experimental and CALPHAD approaches. The results showed that increasing Al content can improve the oxidation resistance of the alloys by promoting the formation of a dense Al2O3 layer and reducing the activity of Ti at 800 ℃ and 900 ℃. However, at 1000 ℃, increasing Al content can promote the formation of Co(W,Mo)O4 and TaTiO4, as well as oxide volatilization, which aggravated the cracking and spallation of the oxide scales and deteriorated the oxidation resistance of the alloys.