Short-term isothermal oxidation of hot extruded GH3536 Ni-based superalloy in solid and semi-solid temperature ranges

The short-term isothermal oxidation process of hot extruded GH3536 alloy in solid and semi-solid temperature ranges was investigated. The solid oxidation rates at 1200 °C, 1250 °C, 1300 °C were 0.049 mg2cm−4s−1，0.125 mg2cm−4s−1, 0.133 mg2cm−4s−1 respectively, while semi-solid oxidation rates at 1350 °C, 1360 °C, 1367 °C were 0.168 mg2cm−4s−1，0.259 mg2cm−4s−1，0.549 mg2cm−4s−1 respectively. Oxide scales formation and spallation were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) with energy dispersion spectroscopy (EDS). The outer diffusion of Cr3+and Fe3+resulted in formation of Fe2O3 and Cr2O3 granular oxides. Diffusion of Ni2+ promoted spinel formation. NiO intermediate oxidation layer was formed beyond 1300 °C, which was conducive to continuous Cr2O3 inner oxidation layer formation. The growth and spallation of oxide scales were significantly accelerated during semi-solid oxidation. The liquid film in the semi-solid microstructure provided a diffusion channel. The inner oxidation layer was destroyed due to thermal stress and severe deformation of the interface between oxide scales and base alloy, which led to a sharp increase in oxidation rate.