Abstract
To analyze the compatibility of structural alloys in supercritical CO2 (sCO2), techniques are needed to quantify any potential alloy degradation. A specific concern for sCO2 environments is the ingress of C into the alloy, which has been observed for more than 50 years in both Fe- and Ni-based alloys. Recently, Glow Discharge Optical Emission Spectroscopy (GDOES) has been increasingly used to measure the concentration of light elements, like C, as a function of depth. As part of a current effort to model the lifetime of structural alloys in sCO2 at 700-800 簞C, several Fe- and Ni-base alloy specimens were analyzed after 1,000-5,000 h exposure in 1 and 300 bar CO2. In general, the specimens exposed at 750簞C showed little or no C ingress. This may be due to the dense external Cr2O3 scale formed on these alloys, which inhibited C transport. At lower temperatures, 550-700 簞C, C ingress was detected in both Fe- and Ni-base alloys.
