Microstructure evolution and failure mechanism of Cr-coated Zry-4 in air and steam at 1200 °C

The dense and uniform Cr coating is successfully applied to the Zry-4 (zircaloy-4) substrate using multi-arc ion plating as an accident-tolerant fuel cladding. The isothermal oxidation behavior of the Cr-coated Zry-4 is investigated in air and steam at 1200 °C. The mass gain,microstructure evolution and phase composition of the Cr-coated Zry-4 after different oxidation times are compared. The mass gain of Cr-coated Zry-4 in air is higher than in steam. In air, the dense Cr2O3 layer consisted of bulk Cr2O3, while protruding flake Cr2O3 is found on the surface of the Cr coating in steam. The degradation process and oxidation failure mechanism of the Cr-coated Zry-4 in air and steam at 1200 °C are analyzed.