Cavity Swelling of 15-15Ti Steel at High Doses by Ion Irradiation

Abstract

The titanium-stabilized austenitic stainless steel Fe-15Cr-15Ni, which shows enhanced resistance to irradiation swelling compared with more traditional 316Ti, has been selected as a core material for fast reactors. Data on the evolution of irradiation swelling in 15-15Ti steels at very high doses, which cannot be easily achieved by neutron irradiation, are still lacking. In this paper, the swelling behavior of the titanium-modified austenitic stainless steel 15-15Ti was investigated by pre-implantation of He at room temperature followed by Ni-ion irradiation at 580 °C to peak doses of 120, 240 and 400 dpa. Relatively small cavities were observed in the zone of helium implantation, while large cavities appeared in the region near the damage peak. A correction formula for the dpa curve was proposed and applied to samples with large swelling. It was found that the steady-state swelling rate of 15-15Ti remains at ~1%/dpa even at high doses. By comparing the swelling data of the helium-implanted and helium-free regions at same doses, 70 dpa and 122 dpa, the suppression of swelling by excessive helium can be deduced at such doses.

Identification of temperature and diffusion effects during helium swelling of the surface layer of a TiTaNbV alloy

“…In comparison with multilayer MeN/Si 3 N 4 films [32], in which the effect of gas swelling is reduced due to the presence of interphase boundaries, and the blistering effect itself is less pronounced, in the case of the alloys under study, the degradation of the near-surface layer is more pronounced, and also has a direct dependence on the irradiation temperature. Moreover, in the case of using these alloys as structural materials for nuclear reactors, high-entropy alloys have significant advantages over traditional stainless steels [33][34][35], which are less resistant to helium blistering, especially at elevated operating temperatures, at which accelerated migration of helium and enlargement of gas-filled inclusions occurs, followed by detonation opening.…”