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

• DOI: 10.1016/j.corsci.2021.109805
• Publication Date: 2021-08-29T21:24:47Z
• Authors: Junkai Liu; Chongchong Tang; Martin Steinbrück; Jianqiao Yang; Ulrike Stegmaier; Mirco Große; Di Yun; Hans Jürgen Seifert
• Keywords: Zirconium alloy; Tetragonal crystal system

Abstract The transient oxidation behavior of magnetron-sputtered chromium-coated Zircaloy-4 was studied in steam up to 1600 °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 °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 ~1500 °C through the higher oxygen diffusion coefficient in the cubic phase.