LAUSR

Abstract Ni coatings applied on structural alloys of molten-salt reactors have been shown to enhance corrosion resistance. Due to inherent advantages, the application of electrodeposited (ED) nanocrystalline Ni coatings could provide a progressive upgrade. The effectiveness, however, relies on the production of favorable microstructural attributes for corrosion resistance and their stability in a high-temperature radiation environment. The present study compares the annealed microstructure of electrodeposited nanocrystalline Ni of varying grain sizes: 20 nm, 50 nm, 100 nm and 200 nm. EBSD studies of samples annealed at 650°C revealed a strong texture of //ED fiber component accompanied by the formation of Σ3 twin boundaries. A high fraction of Σ3 twin boundaries desirable for corrosion resistance is found in samples with initial grain sizes of 20 nm and 50 nm. The irradiation stability of as-deposited 20 nm and 50 nm grain-sized samples was evaluated using ion irradiation at 550°C and compared with unirradiated counterparts that had experienced annealing at the same temperature. Irradiation causes a marginal increase in grain growth and texture, and a slight decrease in Σ3 twin fractions. The desirable microstructural attributes for corrosion resistance are largely preserved up to displacement damage of 18.5 dpa in 20 nm and 50 nm grain-sized samples.