Corrosion Resistance and Surface Modification of Candidate Alloys under Supercritical Water ondition

摘要

One important task in Gen-IV supercritical water (SCW) reactor design is materials selection. Atpresent, no material has yet been identified that can meet the expected core conditions of the CanadianSCWR concept (850 °C cladding surface temperature for a core outlet temperature of 625 °C). High-Cr steels with excellent corrosion resistance are often susceptible to embrittlement due to theprecipitation of sigma and other phases in the microstructure. Low-Cr steels such as P91 exhibit goodhigh-temperature mechanical properties, but the lack of sufficient Cr content makes this group of alloyscorrode too fast. Recent reports by Japanese researchers suggest that certain fine-grained austeniticstainless steels offer good corrosion resistance in SCW. However, such fine-grained structure couldsuffer from high temperature creep. One possible solution is to use coatings or surface modificationtechniques to improve the surface resistance to corrosion. In this study, we investigated the effect ofvarious surface modification methods on commercial 316L stainless steel. Simple surfacemodification has shown significant improvement in corrosion resistance during SCW exposures.Possible mechanisms for improved corrosion performance are discussed.