Transient experiments on oxidation and degradation of Cr-coated Zircaloy in steam up to 1600 °C

The transient oxidation behavior of magnetron-sputtered chromium-coated Zircaloy-4 was studied in steam up to 1600 degrees C, and the microstructural evolution of the coating-substrate system after oxidation was investigated. Coating failure and corresponding rapid oxidation of coating and substrate occurred at 1300-1400 degrees C. It was mainly caused by the thickness decrease of the outer dense Cr2O3 scale, the Zr-Cr eutectic reaction, the Zr-Cr interdiffusion, and the precipitation of ZrO2 along unoxidized Cr grain boundaries. The phase transformation of tetragonal ZrO2-x to cubic ZrO2-y increased the oxidation rate of the Zircaloy-4 substrate at similar to 1500 degrees C through the higher oxygen diffusion coefficient in the cubic phase.

Automated summary

This study investigated the transient oxidation behavior of magnetron-sputtered chromium-coated Zircaloy-4 in steam up to 1600 degrees C, revealing that coating failure and rapid oxidation occurred at 1300-1400 degrees C due to various factors such as thickness decrease of the outer dense Cr2O3 scale and phase transformation of ZrO2-x to cubic ZrO2-y.