Oxidation Behavior of Intermetallic Phase and Its Contribution to the Oxidation Resistance in Fe-Cr-Zr Ferritic Alloy

Abstract

Oxidation resistance of the ferritic Fe-Cr-W-Zr alloy with dispersed Fe2Zr phase were investigated in stagnant air and in static oxygen-saturated liquid Pb-Bi eutectic separately considering the service environment in the advanced generation IV nuclear reactors. A duplex structure including an outer Fe2O3 layer and an inner (Fe,Cr,Zr)2O3 layer is developed after oxidation in air, while a three-layered structure consisting of outer magnetite layer, inner Fe-Cr spinel layer, and internal oxidation zone is formed after oxidation in liquid Pb-Bi eutectic. The dispersed Fe2Zr phase shows delayed oxidation with respect to the α-Fe in air and in liquid Pb-Bi eutectic, which significantly affects the oxidation behaviors of the alloy. After oxidation in air at 923 K, the incorporated Fe2Zr phase in the scale would obstruct the diffusion of metal/oxygen across the scale, resulting in the nonuniform oxidation behavior. After oxidation in static oxygen-saturated liquid Pb-Bi eutectic at 823 K, a reduction in the Fe supply to the magnetite/Fe-Cr spinel interface is present adjacent to the Fe2Zr phase, which might lead to the creation of cavities in the outer magnetite layer with prolonged oxidation time.