Isothermal experiments on eutectic and oxidation reactions of Cr-coated Zr alloy cladding in steam at 1350 ℃: Behavior, mechanism and kinetics

The isothermal steam oxidation experiments of Cr-coated Zr alloy cladding at 1350 ℃ were conducted, and the influence of Cr-Zr eutectic reaction on the oxidation behavior was investigated. The oxidation duration, ranging from 50 s to 3600 s, covers the cases from the initial formation of eutectic liquid to the complete oxidation of the cladding. The microstructures of the coating and the substrate were characterized. The eutectic-oxidation degradation mechanism of the coating is summarized. The migration of the eutectic liquid and the evolution of Cr-rich phases in the post-oxidation eutectic structure are studied and discussed, confirming the process of ZrCr₂ reacting with α-Zr(O) to form Zr₃Cr₃O. The degraded Cr coating and the Cr retained in ZrO₂ during the migration of the eutectic liquid can hardly affect the oxidation of cladding substrate. However, the Cr-rich phases, which eventually aggregated in the radial center of the cladding, can reduce the oxidation rate.