Effect of high-temperature on oxidation behavior of 300 M steel

Abstract

The isothermal oxidation experiment was utilized on 300 M steel to investigate the oxidation kinetics, morphology characterization, and the formation mechanism of the oxide scale. The cross-sectional morphologies, elements distribution, and phase composition of the oxide scale in 300 M steel were analyzed using scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), and X-ray diffraction (XRD) techniques. The results revealed that there are three layers formed consisting of the outer layer, hematite (Fe2O3), the intermediate layer, magnetite (Fe3O4), and the inner layer, wustite (FeO) after the oxidation of 300 M steel at elevated temperature. The oxide scale thickness of 300 M steel increased by increasing the oxidation temperature and time. Meanwhile, the columnar void in the Fe3O4 layer grew wider and gradually extended until it transformed into large cavity. The interface between the oxide scale and the steel substrate became uneven and porous. The results of the present work demonstrated that elements Si, Ni, and Cr diffused from the Fe2O3 and Fe3O4 layers into the FeO layer have significant effects on 300 M steel in terms of the oxidation kinetics, morphology characterization, and the formation mechanism of the oxide scale by impeding the outward diffusion of iron cations and the inward diffusion of O2-. However, the effect changed with the appearance of molten FeO-Fe2SiO4 eutectic in the FeO layer when 300 M steel was oxidized at 1200 ℃.