High-Temperature Steam and Atmospheric Oxidation Characteristic of a Heat-Resistant SP2215 Steel

Abstract

The high-temperature oxidation performance of SP2215 has become an important issue when they were used as superheaters and reheaters exposed to two different high-temperature environments. In this study, the oxidation behavior of SP2215 steel was investigated under steam and an atmosphere of 650–800 °C for 240 h. The microstructural and chemical characterization of the samples were performed using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), a glow discharge optical emission spectrometer (GD-OES), and atomic force microscope (AFM). The kinetic curves of oxidation revealed excellent oxidation resistance under both environments, but significant different oxidation characteristics, oxide film composition, and structure were obvious. In the steam experiment, selective intergranular oxidation was evident at relatively low temperatures, which was attributed to the preference absorption of supercritical water molecules at the grain boundary. Conversely, a double-layer structure of outer Fe2O3 and a small amount of Fe3O4 and inner Cr2O3 was formed uniformly at 800 °C. In the high-temperature atmosphere experiment, a protective chromium film was dominant at 650–700 °C, and a loose multicomponent oxide film was formed at 750–800 °C, primarily consisting of Cr2O3, spinel FeCr2O4, and CuO.