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 degrees C. The formed Cr2O3 layer exhibited thickening-thinning transition characteristic accompanying un-dulation 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.