Enhanced accident tolerance properties of AlCrCuFeMoNbx high entropy coating for nuclear fuel cladding

Abstract

High entropy alloy AlCrCuFeMoNbx (x=0.5, 0.8, 1.4, 2.0) coatings were deposited on Zr-1Nb alloy substrates by magnetron co-sputtering to improve the accident tolerance capability of the nuclear fuel cladding. The structural and accidental tolerant properties of high-entropy alloy coatings have been investigated comprehensively. The results show that coatings with varying Nb contents exhibit amorphous structures. The hardness and elastic modulus of the coatings increase with the Nb content, reaching their maximum values at x = 2.0, which are 11.38GPa and 186.05GPa, respectively. In both the simulated normal operating and accident environment of the nuclear fuel cladding, the oxidation resistance of the coating has been investigated. The best oxidation resistance was achieved at x=0.8 in pure water at 360℃under 18.6MPa for 3 days. The dense Cr2O3 and CrNbO4 oxide films generated on the surface hinder the diffusion of oxygen ions, and account for the lower weight gain 5.10mg/dm2, decreased by 56.4% compared to that of the uncoated zirconium alloy. The coating with x=0.5 showed a drastic reduction in oxidized weight gain by 84.02% compared to the uncoated zirconium alloy in water steam at 1200℃, demonstrating excellent accident tolerance, which is due to the dense α-Al2O3 and CrNbO4 protective layer generated on the surface of the coating. These findings suggest that high entropy alloy coatings have promising accidental tolerance capabilities for nuclear fuel cladding.