Technical Note: Corrosion Resistance of Alloy 33 (Fe-33Cr-32Ni) in Supercritical Water

This study examines the corrosion resistance of wrought Alloy 33 (Fe-33Cr-32Ni) exposed in a static autoclave containing 25 MPa supercritical water at 625°C for 500 h. Gravimetric measurements in combination with electron microscopy analyses showed that the formation of a thin, dense external single-layer Cr₂O₃-based scale provides Alloy 33 with a promising corrosion resistance. However, the microstructure was not stable, as Cr-rich α-ferrite precipitates formed in the subsurface during the short exposure. The suitability of this alloy as a candidate fuel cladding for the Generation IV supercritical water-cooled nuclear reactors concept is discussed in light of the findings presented.