Changfeng Dong

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.

CeO₂ is widely used as a non-radioactive surrogate for UO₂ because of its fluorite crystal structure and similar thermophysical characteristics. In this study, an FIB-assisted specimen preparation route combined with high-temperature nanoindentation was used to evaluate the micromechanical behavior of CeO₂ from room temperature to 400 °C. Hardness and Young’s modulus were experimentally measured at room temperature, 100 °C, 200 °C, 300 °C, and 400 °C. The load–displacement curves were smooth, and no obvious pop-in events were observed within the tested load range. From 100 °C to 400 °C, both Young’s modulus and hardness decreased approximately linearly with increasing temperature, and linear fitting was used to describe their temperature dependence. The measured Young’s modulus decreased from 191.3 ± 14.0 GPa at 100 °C to 136.7 ± 9.5 GPa at 400 °C, while the hardness decreased from 6.79 ± 0.58 GPa to 5.08 ± 0.48 GPa. The obtained temperature-dependent trend is consistent with previously reported high-temperature nanoindentation data for fluorite-structured oxides. These results provide useful micromechanical data and methodological support for elevated-temperature small-scale mechanical characterization of ceramic nuclear fuel surrogate materials.