In-situ study on the tensile property and fracture behavior of Cr coating for nuclear fuel cladding

Abstract

It has been suggested that Cr-coated zircaloy is an excellent material for accident-tolerant fuel (ATF) cladding. It is found that Cr coating shows multi-cracking behavior under external load due to its embrittlement. Different fabrication parameters will lead to different crack resistances of the coatings, but the brittle cracking characteristic is common. The estimation of the strength and structural integrity of the fuel cladding depend on the cracking characteristic of the coating. The Cr coating’s tensile characteristic for ATF cladding was examined utilizing the in-situ mechanical testing method. The surface crack initiation, propagation, and fracture process were captured in real time, and the crack density evolution of two different process parameters was compared. The results demonstrate that the first long channel crack occurs at a small strain, then the crack density increases rapidly and gradually reaches saturation with increasing stress. Different fabrication parameters will change the cracking resistance. Compared with the previous sample, the new sample started to crack at a larger strain, the crack density reached saturation faster with a larger saturated crack density, and the crack resistance is inferior. Many small cracks in different directions were observed near the fracture surface. Moreover, there was no interfacial spallation under stress, demonstrating the Cr coating’s excellent interfacial adhesive property.