Effect of Pre-oxidation Temperature on High-Temperature Cyclic Oxidation Resistance of Ni-20Cr-5Al-0.2Y₂O₃ Alloy

Ni-20Cr-5Al and Ni-20Cr-5Al-0.2Y₂O₃ (mass fraction/%) alloys were prepared by powder metallurgic technology. The Ni-20Cr-5Al-0.2Y₂O₃ alloy was first pre-oxidized at different temperatures from 500 ℃ to 1 100 ℃, and then the un-oxidized and pre-oxidized alloys were cyclic oxidized at 1 150 ℃ for 15 h. The effects of Y₂O₃ and pre-oxidation temperature on the high-temperature cyclic oxidation resistance of the alloys were studied. The results show that the high-temperature cyclic oxidation resistance of Ni-20Cr-5Al alloy was improved with the addition of 0.2wt% Y₂O₃. The pre-oxidation can improve the high-temperature oxidation resistance of Ni-20Cr-5Al-0.2Y₂O₃ alloy effectively. Furthermore, when the pre-oxidation temperature was 700 ℃, the alloy achieved the best high-temperature cyclic oxidation resistance. The reason is that a dense protective oxide scale was formed on the surface of the alloy after pre-oxidation, which prevented the alloy from the further oxidation.