The Fukushima nuclear accident in 2011 exposed the shortcoming of high temperature oxidation resistance of zirconium alloy cladding. For this reason, the concept of accident tolerant fuel was proposed in the international nuclear fuel field. Cr-coated zirconium alloy cladding, as an accident tolerant fuel cladding near-term commercial technology approach, has received extensive attention.

This study aims to study the high-temperature oxidation behavior of Cr-coated Zr-4 alloys at different temperatures.

Cr-coated Zr-4 alloy was prepared by multi-arc ion plating, and oxidized in air atmosphere at 800?1 200 ℃ for 4 h. Scanning Electron Microscope (SEM) and Energy Dispersive Spectrometer (EDS) were used to analyze the surface and cross-sectional micro-morphologies of Cr coated Zr-4 alloy samples before and after high-temperature oxidation and the distribution of elements on the cross section. The orientation image microscopy (OIM), inverse pole figure (IPF) and pole figure (PF) of Cr coated Zr-4 alloy samples were obtained by electron backscatter diffraction (EBSD). The phase of the samples was obtained by glancing angle X-ray diffractometer (XRD).The effect of oxidation temperature on the microstructure, phase, Cr-Zr diffusion layer thickness and oxidation weight gain of Cr-coated Zr-4 alloy were investigated.

The results show that there are a large number of droplets of different sizes on the surface of the Cr-coated Zr-4 alloy samples prepared by multi-arc ion plating, and the Cr coating has a columnar crystal morphology and preferentially grows along the (110) crystal plane. After high temperature oxidation at 800~1 100 ℃ for 4 h, the surface of the sample is oxidized to different degrees, but the un-oxidized Cr coating still remains inside the coating, and no micro-cracks appear on the surface and cross-section of the sample. The thickness of the Cr-Zr diffusion layer increases linearly with the increase of the oxidation temperature, and the oxidation weight gain increases slowly. However, after high temperature oxidation at 1 200 ℃ for 4 h, the Cr coating on the surface of the sample was completely oxidized, a large number of cracks appeared on the surface and cross-section, and the thickness of the Cr-Zr diffusion layer and oxidation weight gain increased sharply.

Therefore, the Cr-coated Zr-4 alloy prepared by multi-arc ion plating exhibited good high temperature resistance at 800~1 100 ℃, while accelerated oxidation occurred at 1 200 ℃.