Narrow Results

Cr coating on Zr-based fuel tubes is a potential approach for the development of accident tolerant fuels (ATF). To settle the cracking behavior and quantitative evaluation of shear strength of Cr coating under different loading conditions, the average shear strength between Cr coating and zircaloy substrate has been estimated using a modified shear-lag model in this paper. Its key parameters are determined experimentally, and the tensile method has been used to research the cracking behavior of Cr coating under different strain rates. The results show that with the increase of strain rate, the interfacial shear strength increases because of the decrease of cracking spacing, while the shear strength changes erratically with the coating thickness increases. Furthermore, abundant two unequal-crack-spacings and few two equal-crack-spacings are observed which are perpendicular to the loading direction.

Cr coatings were deposited on both the polished and rough substrate using DC magnetron sputtering. The influence of substrate surface roughness on the morphology, crystalline phase and mechanical properties of the coatings were analyzed. The results showed that surface roughness had a significant effect on the surface morphology of the coating, as the coating inherited the surface morphology of the substrate. Surface roughness before and after coating for the polished and rough surfaces were 0.054–0.046 and 0.107–0.563$\mu$m, respectively. The hardness and Young’s modulus of the coating deposited on the polished surface were 5.5 and 188.6GPa, respectively, while the mechanical properties of the coating deposited on the rough surface are about the same. The results showed that the adhesion of the coating can be improved by appropriately increasing the surface roughness.