Preparation and Oxidation Behaviour of an Al-Si Coating on a Ni3Al Based Single Crystal Superalloy IC21

摘要

An Al-Si coating was prepared on IC21 alloy by powder pack cementation. The cyclic oxidation tests were carried out at 1150°C in air for up to 100 h. The results indicate that the oxidation resistance of IC21 alloy is significantly improved by the Al-Si coating due to the presence of Ni_2Al_3 and P-NiAl enriched outer layer, and Si can effectively supress the outward diffusion of Mo. The oxide scales mainly consist of α-Al_2O_3, which is the favorite to the oxidation resistance. Phase transformation occurred from β-NiAl to γ'-Ni_3Al and γ-Ni in the coating during oxidation. The coating still remained a certain amount of ss phase after oxidation for 100h, which indicate a good protection. The microstructure change evolution was characterized, and the oxidation behavior of the coating was discussed.