Oxidation Behavior of Micro-Regions in Multiphase Ni3Al-Based Superalloys
Ni3Al-based superalloys are widely used in aero-engine parts.In addition to having a good temperature bearing capacity,the oxidation resistance of the alloy is also high.In this work,a multiphase Ni3Al-based superalloy was selected as the experimental material.Three micro-regions(γ'+ γ dendrite,interdendritic β phase,and γ'envelope)containing different phases were obtained by heat treatment.The isothermal oxidation behavior of the micro-regions was studied under 1000℃,where the three micro-regions exhibited different oxidation behaviors at the initial stage of oxidation.The γ'envelope has an obvious double-layer oxide scale showing a cellular bulge.The outer layer is a mixed layer(NiO,NiFe2O4,and Al2O3),and the inner layer is a single Al2O3 layer.However,the γ'+ γ dendrite and the inter-dendritic β phase form a single layer of the Al2O3 film.With increasing isothermal oxidation time,the oxide scale composition of the three micro-regions gradually tends to be the same,forming a dense single Al2O3 layer.
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