Effect of pressure on supercritical CO2 compatibility of structural alloys at 750 °C.

Several power generation technologies have interest in employing a supercritical CO2 (sCO2) cycle but relatively little compatibility work has been conducted at the target pressure range of 200-300 bar, particularly at ≥700 °C. With the goal of utilizing lower pressure data sets (especially with controlled O2 and H2O contents), this initial assessment compared the effect of CO2 pressure at 1-300 bar on the compatibility of potential Fe- and Ni-base structural alloys after 500 h exposures at 750 °C. For highly-alloyed alumina- and chromia-forming alloys, a minimal effect of pressure was observed on the mass change and reaction products, which were similar to those observed in 1 bar dry air, CO2, CO2-0.15%O2 and CO2-10%H2O. After these relatively short exposures, there was no obvious indication of internal carburization and the Cr depletion in the precipitation strengthened Ni-base alloys (740 and 282) was minimal. In addition to coupons, 25 mm long tensile specimens of alloy 740, 247, 310HCbN, and E-Brite (Fe-Cr) were exposed in each condition but did not show any detrimental effect of the high-purity CO2 environments on room temperature tensile properties. [ABSTRACT FROM AUTHOR]