Revealing the Effect of Ni Alloying on the Ion Irradiation Response of Cr Coatings

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.