High temperature oxidation behavior of Ni-based superalloy GH586 in air

In this paper, the isothermal oxidation kinetics and oxidation behavior of GH586 superalloy from 800 to 1000 A degrees C were investigated. The oxide scale morphologies of the surfaces and the cross sections after oxidation were characterized by means of X-ray diffraction (XRD) and scanning electron microscope (SEM) equipped with energy-dispersive spectroscopy (EDS). The results show that the growth of the oxide scales on the surface of superalloy GH586 obeys a parabolic law with the activation energy of 241.4 kJ center dot mol(-1) from 800 to 1000 A degrees C. The dense oxide scale formed at 800 A degrees C is mainly composed of Cr2O3, NiCr2O4 and a small amount of TiO2. At 900 A degrees C, the oxide scale is divided into two layers: the outer layer with multiple cracks is mainly composed of Cr2O3 and TiO2, while the inner is a layer of dense Cr2O3. Under the oxide scale, aluminum-rich oxides along the grain boundaries are generated by the internal oxidation. At 1000 A degrees C for 100 h, cracks throughout the whole oxide film accelerate the oxidation rate of Ni-based superalloy GH586 and large blocks of TiO2 in the oxide scale are generated, resulting in the spallation of oxide scale.