LAUSR

The corrosion behavior of heat-resistant steels, including T91, VM12, Super 304H, and Sanicro 25, in high-temperature supercritical carbon dioxide at 650 °C and 15 MPa for 1000 h was investigated. X-ray diffraction, Raman spectroscopy, and glow-discharge optical emission spectrometry were employed to characterize the corrosion products. The results showed that the weight gain of the investigated steels is in the order of T91 > VM12 > Super 304H > Sanicro 25. Compared with the dual layers of Fe3O4 and FexCr3−xO4 on T91 and VM12, the chromia-rich oxide scales on Super 304H and Sanicro 25 enhanced their corrosion resistance. Internal carburization zones were found underneath the oxide scales, indicating the presence of oxidation and carburization reactions in the supercritical carbon dioxide. Moreover, the total carbon uptake into the T91 and VM12 steels approximately followed a parabolic law with experimental time but followed a linear law for the austenitic heat-resistant steel Sanicro 25. A corrosion mechanism that couples oxidation and carburization is summarized and quantified for oxidation and carburization to determine the dominant reaction.