In this work, a comparative study was conducted on the tensile behaviors of two representative accident-tolerant cladding coatings, i.e., CrN coating and Cr coating, at both room temperature and 400 °C by in situ tensile testing. The surface and interfacial cracking behaviors of the coatings were experimentally tested and analyzed, with the surface crack densities predicted by a modified shear-lag model. The results showed that CrN coating exhibited brittle fracture at both room temperature and 400 °C, while the failure of Cr coating showed brittle-to-ductile transition when increasing the temperature from room temperature to 400 °C. Moreover, Cr coating exhibited better crack resistance than that of CrN coating under mechanical loading at both temperatures, due to: (i) the higher fracture toughness and ductility of Cr; (ii) better deformation compatibility between Cr coating and Zr-4 substrate. In particular, at 400 °C, Cr coating with excellent plastic deformability exhibited a protective or prohibitive effect on the crack initiation process of the Zr-4 substrate. It is indicated that the mechanical deformation properties and failure mechanisms of Cr and CrN coatings are important factors that should be considered in the selection and evaluation of accident-tolerant coatings.

在这项工作中，通过原位拉伸试验，在室温和400°C下，对两种代表性的耐事故覆层涂层（即CrN涂层和Cr涂层）的拉伸行为进行了比较研究。实验和测试了涂层的表面和界面开裂行为，并通过改进的剪切滞后模型预测了表面开裂密度。结果表明，CrN涂层在室温和400°C时均表现出脆性断裂，而Cr涂层的失效在温度从室温升高至400°C时表现出脆性-延性转变。此外，在两个温度下，Cr涂层在机械载荷下均表现出比CrN涂层更好的抗裂性，这是由于：（i）Cr的断裂韧性和延展性更高；（ii）Cr涂层和Zr-4基材之间具有更好的变形相容性。特别地，在400℃下，具有优异塑性变形性的Cr涂层对Zr-4衬底的裂纹萌生过程表现出保护或抑制作用。研究表明，Cr和CrN涂层的机械变形性能和破坏机理是在选择和评估耐事故涂层时应考虑的重要因素。