SiC as a diffusion barrier: Mitigating Cr-Zr interdiffusion in Cr-coated Zr alloy cladding under high-temperature steam

Although Cr-coated zirconium alloy cladding exhibits promising accident tolerance, its service life under Loss-of-Coolant Accident (LOCA) conditions is severely limited by the detrimental Cr-Zr interdiffusion and the resultant brittle intermetallic formation. To address this problem, a silicon carbide (SiC) interlayer, deposited via radio frequency magnetron sputtering, is introduced as an effective diffusion barrier situated between the Cr coating and the zirconium alloy substrate. The microstructure evolution, interdiffusion behavior of elements, and interface stability of both the Cr/SiC and SiC/Zr interfaces were systematically investigated by high-temperature steam oxidation experiments. The results revealed that the coating system with the SiC barrier layer exhibited a significantly lower oxidation mass gain per unit area with a value of only 1544.45 mg/dm² after exposure to a 1200 °C high-temperature steam environment for 7200 s, which is merely 69.5% of that of the Cr-coated sample. The enhanced oxidation resistance is attributed to the synergistic effect of the SiC barrier layer and the in-situ formed Cr₃Si, ZrC_1-x and Zr₂Si phases, which collectively inhibit Zr-Cr interdiffusion and mitigate coating failure. These findings provide a novel strategy and theoretical foundation for the development of advanced Cr/SiC coatings, with the potential to extend the service life of Cr-coated zirconium alloy cladding under accident conditions.