PRECIPITATION RESPONSE OF 20-PERCENT-COLD-WORKED TYPE 316 STAINLESS-STEEL TO SIMULATED FUSION IRRADIATION

The precipitation response of 20%-cold-worked type 316 stainless steel has been examined after irradiation in HFIR at 380-600°C, after irradiation in EBR-11 at 500°C, and after thermal aging at 600 to 750°C. Eta phase forms during exposure to all environments. It constitutes a major portion of the precipitation response, and is rich in Ni, Si and Mo relative to M23C6 after thermal aging. It is not normally reported in 20%-cold-worked type 316 stainless steel. The eta, M23C6, Laves, sigma, and chi precipitate phases appear at similar temperatures after HFIR, EBR-II, or thermal exposure. There are, however, some differences in relative amounts, size, and distribution of phases among the various environments. Eta phase is the only carbidetype phase observed after irradiation in HFIR from 380-550°C. The large cavities associated with it at 380°C contribute significantly to swelling. Re-solution of fine M23C6, eta, and Laves particles and re-precipitation of massive particles of sigma, M23C6 and chi are observed after recrystallization in HFIR. © 1979.