Effect of thickness on degradation of austenitic 347H steel by direct-fired supercritical CO2 power cycle environment

Abstract Austenitic 347H steel of two thicknesses (2.54 and 0.6 mm) was exposed to a simulated direct-fired supercritical CO2 (sCO2) power cycle environment at 650 °C and 1 atm for 1000 h then tensile stressed at room temperature to study the deformation behavior. The thicker 347H formed a protective chromia scale over most of the surface, which minimized carburization of the underlying steel and resulted in no change in mechanical performance. In stark contrast, the thinner 347H formed non-protective Fe-rich oxides over the entire surface, resulting in extensive carburization of the underlying steel. This led to increased strength but significantly reduced ductility, resulting in partially brittle failure. Data availability All relevant data that support this study are available from the corresponding author upon request.