Evolution of Cr/Cr₂O₃ interface in Cr-coated zirconium alloy in high temperature steam

<100> textured Cr-coating was deposited on Zr-based nuclear fuel cladding and went through steam oxidation at 1200 °C. The formed Cr₂O₃ layer exhibited thickening-thinning transition characteristic accompanying undulation of the Cr/Cr₂O₃ interface with oxidation progress. Electron microscopy characterization revealed that the convex tips of Cr/Cr₂O₃ interface invariably linked to grain boundaries of residual Cr-coating, which channeled the outward diffusion of Zr atoms consequently reducing Cr₂O₃-grains into Cr-grains. The reduction reaction at the Cr/Cr₂O₃ interface accounts for the interface undulation and consumption of protective oxides. This study is expected to shed light on failure mechanism of protective oxides on ATF Cr-coatings.