The use of supercritical CO2 (sCO2) and the Brayton cycle is being investigated for use as the working fluid in several next generation technologies including fossil fuel, and nuclear energy generation. However the amount of data for the compatibility of structural materials with sCO2 is lacking, especially at higher temperatures, and a large database for material compatibility needs to be established. We have done preliminary testing at 650-750°C, and 1–300 bar in gaseous CO2 and sCO2. Results show that the temperature of the system is the primary driving force for the compatibility of materials, while the change in pressure has little effect. Tensile tests were performed on samples exposed in sCO2, and little effect was seen on the tensile strength and elongation of the materials due to the change in pressure. More tests are needed to determine the effects on the candidate materials of longer exposure times, and impurities.