Helium ion irradiation induced swelling and hardening in commercial and experimental ODS steels

The radiation resistance of two promising ferritic ODS steels, PM2000 and 15CRA-3, is studied. More specifically, the effect of helium on these materials is studied by examining the swelling and hardening after He⁺ implantation to ∼1 dpa at 4000 appm/dpa. White light interferometry is used to measure the post-irradiation surface displacement whereas mirco-hardness measurements are carried out to determine the radiation hardening. These methods prove to be very efficient and fast working, thus making good statistics obtainable in a reasonable time. Low swelling is found in both alloys, although the PM2000 shows a lower resistance, with an increased swelling of ∼0.8% dpa⁻¹ at 600 °C, while the 15CRA-3 presents an almost constant swelling of around 0.4% dpa⁻¹ throughout the complete temperature range. Radiation hardening follows a similar trend, whereby hinting towards an annealing mechanism taking place at the interfaces between the very fine distribution of Y₂O₃ nanoparticles and the matrix, interfaces which act as sites of enhanced point defect recombination as well as traps for the implanted helium