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 (gamma ' + gamma dendrite, interdendritic beta phase, and gamma ' envelope) containing different phases were obtained by heat treatment. The isothermal oxidation behavior of the micro-regions was studied under 1000 degrees C, where the three micro-regions exhibited different oxidation behaviors at the initial stage of oxidation. The gamma ' 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 gamma ' + gamma dendrite and the inter-dendritic beta 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.