Effect of stress on corrosion behavior of martensitic and austenitic steels in supercritical carbon dioxide at 550 °C and 20 MPa

Abstract

Corrosion of alloys in supercritical carbon dioxide (S-CO2) Brayton cycle power generation systems is a critical issue. In this study, we investigated the corrosion behaviors of martensitic AISI 616 and austenitic AISI 304 exposed to S-CO2 at 550 °C and 20 MPa. The effect of stress loading on the corrosion behavior was studied. A 9-μm-thick double-layer oxide with an outer layer of Fe3O4 and an inner layer of (Fe, Cr)-rich oxide was formed on the surface of the AISI 616. When stress was applied, the oxide layer thickness increased significantly to 15 µm. Stress loading thus promoted carbon deposition, accelerated the oxidation rate, and increased oxide thickness. AISI 304 generated a monolayer of (Fe, Cr)-rich oxide that was much thinner than that of AISI 616 owing to its high Cr content. In addition, the effect of stress on the corrosion of AISI 304 was weaker than that of AISI 616.