The AlNbTiZr medium-entropy alloy (MEA) coatings with different Al contents were prepared on N36 zirconium alloy substrates by RF magnetron co-sputtering. The morphology, microstructure, mechanical properties, surface wettability and corrosion resistance of the AlNbTiZr MEA coatings were studied to evaluate the surface protection behavior of zirconium alloy cladding under operation conditions of a pressurized water reactor. The results showed that all the coatings were composite structures with amorphous and bcc-structured nanocrystals. With the increase of Al content, both the elastic modulus and hardness decreased first and then increased. The hydrophobicity of the coatings was enhanced compared with that of the substrate. The 10.2 at.% Al AlNbTiZr coating had the best corrosion resistance and the minimum oxygen penetration depth, which originated from the formation of a denser oxide layer consisting of Nb₂Zr₆O₁₇ and ZrO₂. This study provides an improved idea for the design and development of Al-containing MEA coating materials for accident tolerant fuel.

Zirconium alloys are subjected to a fast neutron flux in nuclear reactors, inducing the creation of a large number of point defects, both vacancy and self-interstitial. These point defects then diffuse and can be trapped by their different sinks or can cluster to form larger defects, such as vacancy and interstitial clusters. In this work, the trapping capability of small-vacancy clusters (two/three vacancies, V₂/V₃) in the α-Zr doped with alloying elements (Sn, Fe, Cr, and Nb) has been investigated by first-principle calculations. Calculation results show that for the supercells of α-Zr containing 142-zirconium atoms with the two-vacancy cluster, alloying elements of Sn and Nb in the second vacant site (V2) and Cr in the first vacant site (V1) are more easily trapped by two vacancies, respectively. However, the two sites are both captured more easily by two vacancies for Fe in the supercells of α-Zr containing 142-zirconium atoms inside due to the similar value of the Fermi level. For the supercells of α-Zr containing 141-zirconium atoms with the three-vacancy cluster, the alloying element of Sn in the third vacant site (V’3), Fe in the first vacant site (V’1), and Cr and Nb in the second vacant site (V’2) are more easily trapped by three vacancies, respectively.

We investigated the impact of Au ion irradiation on the corrosion behavior of medium-entropy alloy coatings (MEAs), with and without Al addition, in simulated primary water of pressurized water reactors (PWRs). The results indicated the formation of double-layer oxide films on the surfaces of both types of coatings, consisting of outer oxide particles and a protective inner oxide layer. The high-fluence irradiation modified the microstructures of both coatings and accelerated their corrosion kinetics. However, the coating with a slight addition of Al demonstrated superior post-irradiation corrosion resistance owing to its enhanced lattice distortion effect within the system, inhibited atomic diffusion, and reduced impact of irradiation on its phase structure. A comprehensive discussion was carried out on the corrosion processes of the coatings, both irradiated and non-irradiated.

Chromium coatings with excellent corrosion resistance and strong Zr interfacial bonding are economical candidates for accident-tolerant fuel claddings. Irradiation-triggered elemental interdiffusion and interfacial voids severely degrade their service reliability. Ni alloying was introduced into the Cr matrix to obtain composite coatings with improved mechanical properties and irradiation resistance. CrNi coatings with different Ni contents were deposited using magnetron sputtering, whose microstructural features, phase composition, mechanical properties and irradiation behavior were comprehensively characterized by XRD, SEM, TEM and mechanical measurements. The pristine CrNi coatings display compact and uniform microstructural morphologies. Increasing Ni concentration significantly refines the columnar grain architecture and diminishes grain dimensions. Post-irradiation microstructural characterization reveals distinct structural evolution features of CrNi coatings with different Ni contents. Pure Cr and low-Ni coatings present enhanced XRD diffraction intensities and contain high-density irradiation-induced dislocation loops. The 27 at.% Ni coating after irradiation is indicative of irradiation-triggered local recrystallization and defect annihilation. Mechanical tests confirm that moderate Ni alloying (~17 at.%) achieves improved resistance to irradiation-induced hardening through solute–defect interaction effects, whereas excessive Ni (~27 at.%) degrades mechanical properties owing to aggravated lattice disorder, increased free volume, and soft Ni-phase dilution effects.