Influence of Al content and low oxygen pressure preoxidation on high‐temperature oxidation resistance of Ni–25Cr–xAl–1Si–0.5Y alloys

The influence of Al content and low oxygen pressure preoxidation on the high‐temperature oxidation resistance of the Ni–25Cr–xAl–1Si–0.5Y (x = 0, 1, 3, 5 wt%) alloys were studied. The formation of oxides in low oxygen pressure preoxidation was investigated. The oxidation behavior of alloys with different Al content at 1000°C with and without preoxidation under low oxygen pressure was discussed. A protective oxide film was formed on the surface of alloys with different Al content in low oxygen pressure pre‐oxidation at 950°C for 5 h, but there were great differences in microstructures and properties. With the increase of Al content, the outermost oxide film of the alloy gradually changed from continuous Cr2O3 to Al2O3, and the oxidation resistance of the alloy increased gradually at 1000°C. By comparison, the oxidation resistance of Ni–25Cr–xAl–1Si–0.5Y (x = 0, 1, 3, 5 wt%) alloys can be significantly improved at 1000°C by low oxygen pressure preoxidation treatment.