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

Ni基ODS超合金の過酷環境下における 相の照射効果

金野 杏彩; 大野 直子*; 鵜飼 重治  ; 近藤 創介*; 橋冨 興宣*; 木村 晃彦*

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

現在、1273K以上、100dpaにも及ぶ過酷環境である炉心を有する、高温ガス炉やガス冷却高速炉において、材料開発が積極的に行われてる。従来の研究では、この候補材料として、Fe基合金よりも高温強度に優れるNi基合金が研究されてきたが、高温強度を担保する相は650C・50dpaの条件で相の溶解・結晶粒界への再析出による強度低下と脆化が生じてしまうことが明らかとされた。そこで、我々は、脆化を抑制するために、商用合金のCMSX10に微細な酸化物粒子を分散させることでこれまでのNi基合金を凌駕する析出型Ni基ODS超合金(MS4)を開発した。本研究では、本合金における相の高温重照射影響を評価することを目的とした。

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.