Interface stability and microstructural evolution of the (Cr/CrN)24-coated zirconium alloy under different thermal shock temperatures

Thermal shock resistance is highly important to the selection of practical accident tolerance fuel coatings (ATFCs). The performance of three coatings (Cr, CrN and (Cr/CrN)24) prepared by radio frequency magnetron sputtering (RFMS) were compared in thermal shock tests at 900– 1200 °C. The interface stability, microstructural evolution and oxidation behaviors of the (Cr/CrN)24 multilayer coatings were systematically investigated. The results indicate that the thinning of the Cr2O3 layer is related to the evaporation of volatile CrO2(OH)2 during quenching in boiling water. The coatings exhibited severe performance degradation at 1200 °C mainly because of significant mutual diffusion of Cr and Zr, which caused oxygen to diffuse into the substrates and form ZrO2. The relationship between the microstructure evolution and element diffusion is analyzed in detail.