Oxidation of Materials in Supercritical Water Environment

摘要

Supercritical water is being considered as a cooling medium for the next generation nuclear reactors because it provides for high thermal efficiency and plant simplification. However, materials corrosion has been identified as a critical problem because of the oxidative nature of supercritical water. A number of Cr-containing ferritic steels as well as austenitic steels have been evaluated for corrosion in SCW environment at temperatures up to 600 deg C after exposure durations of up to 1000 hours. The ferritic steels develop a distinct two-layered oxide structure, consisting of an outer magnetite layer and an inner Fe-Cr oxide spinel layer. Surface modification was noted to improve oxidation resistance of these steels. Austenitic steels exhibited a higher oxidation resistance, but in some cases oxide spallation was observed. Oxide spallation in these steels was mitigated by thermo-mechanical treatments aimed at enhancing the population of low energy grain boundaries.