Thermodynamic Analysis of Typical Alloy Oxidation and Carburization in High-Temperature CO2 Atmosphere

The corrosion of structural materials is a crucial issue of the application of supercritical carbon dioxide in the Brayton power cycle system. The oxidation and carburization behaviors of typical alloy materials in high-temperature CO2 environments are studied based on thermodynamic analysis technology, including the analysis of the oxidation and carburization performance of the CO2 atmosphere as well as the corrosion behaviors of alloy elements under 500 °C, 600 °C, and 650 °C. In addition, the oxide film characteristics of T91 and 800H alloys, including phase composition and morphology structure, are studied at 500 °C and 650 °C. Research has found that for the T91, FeCr2O4 and Fe3O4 can form a continuous oxide film layer with coverage and SiO2, VO, and MnCr2O4 oxides are mainly in the inner layer of the oxide film. For the 800H, Cr2O3 and MnCr2O4 can form flakes of oxide film layers, while Al2O3, TiO2, and SiO2 are distributed as scattered grains near the interface between the oxide film and the matrix material. Both T91 and 800H will produce chromium carbides, which will reduce the toughness of the material.