Utilization of Hydrogen as an Alloying Element: New Frontier in Hydrogen Resistant Austenitic Steels

2023 Fiscal Year Final Research Report

• Project/Area Number: 21K14045
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 18010:Mechanics of materials and materials-related
• Research Institution: National Institute for Materials Science (2022-2023); Kyushu University (2021)
• Principal Investigator: Ogawa Yuhei 国立研究開発法人物質・材料研究機構, 構造材料研究センター, 研究員 (30847207)
• Project Period (FY): 2021-04-01 – 2024-03-31
• Keywords: 鉄鋼材料 / オーステナイト / 水素脆化 / 強度・延性 / 固溶強化 / 変形双晶

Outline of Final Research Achievements

In hydrogen energy-ralated equipment and infrastracture, a combined achievement of excellent mechanical properties and hydrogen emrittlement resistance is desired for structural metallic materials. In this study, we aimed to find the way to utilize the strengthening and ductilization effects by solute hydrogen in austenitic steels, which have recently been discovered, in order to solve this problem. Solid solution-hardening and an enhancement of deformation twinning by hydrogen were studied for Fe-Cr-Ni alloy system, elaborating the underlying mechanisms of these two valuable phenomena. Ultimately, the required conditions for the strengthening and ductilization were identified in terms of alloy composition, strain rate, and deformation temperature. A new model for hydrogen-dislocation interaction responsble for the strengthening was proposed.

Free Research Field

材料力学，構造材料

Academic Significance and Societal Importance of the Research Achievements

水素脆化現象は1874年に発見されて以降，橋梁用高力ボルトの遅れ破壊や溶接部材の低温割れなど，水素侵入に伴う破壊事故の要因として工業的にも常に重要技術課題の一つに位置付けられてきた．その中において，水素によって力学特性の向上を示す材料の実例とその発現メカニズムを明示した本研究の成果が，水素侵入を危惧するのではなく，逆に有効利用するという新たな道を切り拓くための一助になることを期待する．また，「水素脆化は材料が高強度化するほど顕著となる」，これが構造材料分野の50年以上に渡る常識であったが，本研究が示す事実はこの従来常識を180度覆すという観点において，その学術的意義は大きい．