Nano-slacle mechanical test of irradiated X-750 Ni-based superalloy

This study investigates the effect of helium implantation on mechanical properties of irradiated X-750 Ni-based superalloy used as a spacer material in CANDU reactor. For this purpose, two different irradiation procedures have been carried out including single self-ion (Ni+) irradiation at 400 °C and the implantation of 5000 appm (atomic parts per million) helium followed by Ni ion irradiation at 400 °C up to 1 dpa (displacement per atom). Nano-indentation tests were conducted at room temperature at different depths on both irradiated and un-irradiated materials. The results show that pre-helium implantation enhances the irradiation-induced hardening. The cross-sectional TEM (transmission electron microscopy) observations revealed that generating a high density of small cavities and promoting the formation of larger Frank loops are the main reasons of significant hardening of helium implanted material.