High-Temperature Isothermal Oxidation Behavior of Newly Developed Fe–Cr–Ni Austenite Stainless Steel

One of the significant causes of failure in aerospace engine components is high-temperature oxidation. Therefore, it is necessary to investigate the high-temperature oxidation behavior of newly fabricated structural materials for aerospace components. From this perspective, the isothermal oxidation behavior and kinetics of newly developed stainless steel (SS) 08X14H were investigated at 750, 950 and 1050 °C for up to 100 h in an air environment. The weight results demonstrate that oxidation in 08X14H increases with time and temperature and follows a parabolic rate law. Major spallation was observed in samples oxidized for 100 and 24 h at 950 °C and 1050 °C, respectively. Structural and morphological analysis of oxidized samples through X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) of the surface and cross section reveal the phases present and their distribution. The structural results confirm the formation of Fe2O3, Cr2O3, FeCr2O4 and intermediate (Cr, Fe)2O3 oxides in the oxidized samples. Surface morphologies reveal that the formation of a Cr2O3 layer effectively protects the material from further oxidation. At higher temperatures, the coarsening of Fe2O3 oxides takes place, which leads to the formation of loose and porous oxide scale with stress-induced cracks. The spallation of the outermost Fe2O3-rich oxide scale was observed, and the matrix is exposed during the extreme oxidation at 950 and 1050 °C for 100 and 50 h, respectively. The cross-sectional morphologies and elemental mapping results reveal a duplex oxide layer with an outermost Fe2O3 layer followed by an underlying layer of Cr2O3, (Cr, Fe)2O3 and FeCr2O4 spinel beneath the Fe2O3 layer.