Development of gamma prime-strengthened austenitic Fe-based superalloys - A new ultra high-temperature structural materials

2020 Fiscal Year Final Research Report

• Project/Area Number: 19K22053
• Research Category: Grant-in-Aid for Challenging Research (Exploratory)
• Allocation Type: Multi-year Fund
• Review Section: Medium-sized Section 26:Materials engineering and related fields
• Research Institution: Kyoto University
• Principal Investigator: INUI HARUYUKI 京都大学, 工学研究科, 教授 (30213135)
• Co-Investigator(Kenkyū-buntansha): 岸田 恭輔 京都大学, 工学研究科, 准教授 (20354178) ; 新津 甲大 京都大学, 工学研究科, 助教 (90733890)
• Project Period (FY): 2019-06-28 – 2021-03-31
• Keywords: 鉄基超合金 / 耐熱構造材料 / 2相組織 / 整合析出 / 格子ミスフィット / 高温強度 / クリープ / 単結晶

Outline of Final Research Achievements

Although the excellent high-temperature properties of Ni-based superalloys have been considered to stem from two-phase cuboidal microstructures consisting of FCC (γ) and L12 (γ’) phases, such microstructures have never been formed in heat-resistant steel based on Fe. We have found that L12 solid solutions are formed continuously in the Fe3Ge-Ni3Ge pseudo-binary system and the L12 phase can coexists with FCC-(Fe,Ni) phase up to a chemical composition considerably rich in Fe, forming two-phase cuboidal microstructures. We have further elucidated some guiding principles for alloy design of Fe-based superalloys.

Free Research Field

材料物性

Academic Significance and Societal Importance of the Research Achievements

Fe-rich組成で優に50%を超えるγ’相をCube-On-Cube方位関係で整合析出させたγ-γ’2相組織を実現するのは世界初であり，高温材料や鉄鋼材料の多くの教科書に「Fe基の合金ではγ’相の相分率は10%を超えることはない」との記述を覆す学術的な意義を有する．このような2相組織は構造材料の耐熱性を向上させる上で有用であり，現在の耐熱鋼の耐用温度630℃を遥かに超える耐用温度をもつ新規な鉄基超合金の開発に繋がる研究であり，例えば火力発電所の発電効率を改善し，地球温暖化ガス排出量の大幅な削減に繋がり得るため社会的意義も大きい．