Irradiation effects on phase stability of precipitates in nickel based oxide dispersion-strengthened superalloys under severe conditions

Konno, Azusa; Ono, Naoko*; Ukai, Shigeharu  ; Kondo, Sosuke*; Hashitomi, Okinobu*; Kimura, Akihiko*

It is essential to develop the structural materials in Very High-temperature Reactors (VHTR) or Gas-cooled Fast Reactors (GFR) which reactor core environment is severe as the temperature is over 1273 K and irradiation level is up to 100 dpa. In the past, Ni-based alloys which are superior to Fe-based alloys as high-temperature strength were studied because of its precipitates for reactor core materials. However, dissolves and reprecipitates at grain boundaries by irradiation at about 873 K. In order to show the suppression of this embrittlement, we newly developed a precipitation type Ni-based Oxide Dispersion-Strengthened (ODS) superalloy in which nano-sizeed oxide particles are finely dispersed. In this research, the stability of cuboidal precipitates under heavy irradiation was studied for newly developed Ni-based ODS superalloys, to explore the suitability of these as core materials. The specimen composition was equivalent to the MS4 produced by modifying the commercial superalloy CMSX10 to which the oxide particles are added.