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

Abstract

This study examines the corrosion resistance of wrought Alloy 33 (Fe-33Cr-32Ni) exposed in a static autoclave containing 25 MPa supercritical water (SCW) 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 Cr 2 O 3 -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 sub-surface 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.

Key Processing Factors in Hydrothermal Liquefaction and Their Impacts on Corrosion of Reactor Alloys

“…Among all the candidate construction materials, Alloy 33 has been considered a promising candidate due to its application in similar high-temperature aqueous systems. Based on a previous study [72], Alloy 33, a chromium-based austenitic alloy, was found to develop a thin and compact Cr 2 O 3 -based oxide layer on its surface when exposed to 25 MPa supercritical water at 625 • C for 500 h. This oxide layer acts as a protective barrier, preventing extensive oxidation of the substrate, which suggests its potential suitability for fuel cladding materials. Furthermore, Alloy 33 has demonstrated promising corrosion resistance in high-temperature steam environments up to 800 • C. As a result, Alloy 33 was chosen as a representative high chromium alloy for corrosion studies in simulated HTL environments.…”