Positive role of Y2O3 nanoparticles/matrix interface in enhancing corrosion and irradiation resistance of oxide dispersion-strengthened Ni-based alloys in molten salt environments

The oxide dispersion-strengthened Ni-based alloy, a promising structural material for molten salt reactor cores, exhibits excellent corrosion resistance to molten salts, although the underlying mechanisms remain unclear. In this study, NiMoCr–Y 2 O 3 alloy was prepared using powder metallurgy, and corrosion experiments were conducted on NiMoCr–Y 2 O 3 alloys in FLiNaK molten salts to investigate the effects of the Y 2 O 3 nanoparticles/matrix (Y 2 O 3 -M) interface on corrosion, as well as the synergistic evolution of He irradiation and corrosion. Results from electron probe microanalysis (EPMA) and weight loss analysis indicated that the NiMoCr–Y 2 O 3 alloy exhibited corrosion resistance comparable to that of Hastelloy N (HN) alloy in FLiNaK molten salt. However, under He + ion irradiation, the NiMoCr–Y 2 O 3 alloy significantly outperformed the HN alloy. Meanwhile, only Cr 2 O 3 was detected in the corroded sample via Grazing Incidence Wide-Angle X-Ray Scattering (GIWAXS) and Transmission Electron Microscopy (TEM), while both YCrO 3 and Cr 2 O 3 were observed in the irradiated and corroded sample, accompanied by the disappearance of helium (He) bubbles at the Y 2 O 3 -M interface. The disparity in performance and defect evolution behaviour originates from distinct Cr diffusion mechanisms. Notably, irradiation-corrosion increases the Cr diffusion coefficient in both alloys by approximately an order of magnitude compared to corrosion, due to He bubbles providing fast diffusion pathways. This study reveals the mechanism of the NiMoCr–Y 2 O 3 alloy's superior irradiation-corrosion resistance. These results provide a critical foundation for the development of irradiation-resistant and molten salt corrosion-resistant structural materials in high-temperature molten salt reactors.