Diffusion and dissolution mechanism of CrSi coated Zr alloy by experiments and first principles

Accident-tolerant fuel (ATF) represents a critical research direction for enhancing nuclear reactor safety, with Cr-coated zirconium alloy cladding being one of the leading ATF cladding candidates. However, under beyond-design-basis accidents (BDBA) and reactivity-initiated accident (RIA) conditions, the eutectic melting of Cr-Zr poses a significant challenge to cladding integrity and safety. Current research suggests that suppressing elemental diffusion at the Cr/Zr interface is key to designing Cr coatings with enhanced resistance to eutectic melting, with the most effective approach being the introduction of a diffusion barrier layer between the coating and the substrate. In this study, a combined experimental and first-principles simulation approach was employed to investigate atomic diffusion behavior and dissolution mechanisms in CrSi coatings. CrSi coatings were conducted using a multi-arc ion beam physical vapor deposition system, followed by vacuum annealing in the 1800s to examine interfacial diffusion phenomena between the CrSi coating and the zirconium substrate. Meanwhile, the scratch tests and steam oxidation experiments were performed to investigated the CrSi coating performance. Furthermore, first-principles calculations were further conducted to establish interfacial dissolution models for the CrSi coating and the zirconium substrate, elucidating the dissolution mechanisms of Cr and Si atoms in both the HCP-Zr and transformed BCC-Zr phases. This study provides novel insights and theoretical foundations for the development of advanced Cr-Si-containing coatings, facilitating the engineering application of coated zirconium cladding under BDBA and RIA conditions.