Effect of He ions irradiation on corrosion behavior and mechanical responses of SiC in molten FLiNaK salts

• The corrosion behavior and mechanical properties of SiC in molten FLiNaK salt were significantly influenced by pre-irradiation with He ions. • The corroded exfoliation depth exhibited a positive correlation with the irradiation dose. • The Ni impurity in salt played a key role in the irradiation-promoted corrosion. • The hardness of the corroded zone decreased significantly because of the formation of a C-rich layer with a graphite structure. Silicon carbide (SiC) as a promising material in molten salt reactors will be subjected to both irradiation and high-temperature corrosion environment. Chemical vapor deposited SiC samples were irradiated with 400 keV He ions at room temperature and subsequently exposed to FLiNaK salt at 750 °C for 166 h, for investigating the effect of irradiation on the corrosion behavior and mechanical properties of SiC. Results indicated that molten-salt corrosion caused partial surface exfoliation of SiC, resulting in the formation of a C-rich layer with graphite structure. Exfoliation depth exhibited a positive correlation with irradiation doses. The presence of Ni impurity at the corroded boundary indicated that it plays a significant role in the irradiation-promoted corrosion process. Moreover, Ni 2 Si or Ni 31 Si 12 compounds formed by Ni impurity with Si atoms revealed a crystal plane spacing of 1.91 Å. Hardness of irradiated-only SiC initially increased and then decreased slightly with irradiation dose. Moreover, hardness of the corroded zone in irradiated & corroded samples showed a substantial decrease, due to the formation of a C-rich layer with graphite structure. The hardness of the corroded zone increased with irradiation dose, which was mainly attributed to the pinning effect of oversized bubbles through high-temperature annealing during corrosion process.