Oxidation Behavior of Incoloy 825 at 950 °C under Static Air Atmosphere

The oxidation behavior of Incoloy825 alloy at 950 °C under static air atmosphere was investigated. The microstructure and layered structure of the oxide were investigated by isothermal oxidation in static air from 1 to 120 h using SEM, XRD, and STEM. The results show that oxide skin thickness of the sample subjected to oxidation for 60 h is close to 9 μm. When the oxidation time is 120 h, resulting in accelerated oxidation, and the oxidation weight gain rate reaches 1.09 mg cm⁻². The oxide scale is divided into four layers. The first layer is Cr₂O₃ and TiO₂, and voids and cracks appear at the interface combined with the matrix. The second layer is (Cr, Fe, Ti)-oxide, the third layer is (Cr, Fe, Ti, Ni)-oxide, and the fourth layer is a mixed layer of various oxides, which is mainly composed of Cr₂O₃, Fe₂O₃, NiCr₂O₄, FeCr₂O₄ and TiO₂. In addition, obvious peeling areas appear on the surface.