Mechanism of hydrogen-induced creep in precipitation-hardened Ni-based superalloys

2021 Fiscal Year Final Research Report

• Project/Area Number: 19K14855
• 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: Kobe Material Testing Laboratory, Co., Ltd
• Principal Investigator: Okazaki Saburo 株式会社神戸工業試験場(生産本部技術開発部), 技術企画室, 研究員 (70780831)
• Project Period (FY): 2019-04-01 – 2022-03-31
• Keywords: 水素脆化 / Ni基超合金 / 析出強化 / 応力緩和 / 延性低下

Outline of Final Research Achievements

In order to clarify the mechanism of hydrogen embrittlement in Ni-based superalloy, stress relaxation tests and tensile tests were conducted by using the hydrogen charged specimens. In stress relaxation tests, it was confirmed that stress relaxation was slightly　increased with increase of hydrogen contents. On the basis of these results, it was inferred that the mechanism of hydrogen embrittlement was not attributed to the enhancement of dislocation motion. In tensile tests, the hydrogen induced ductility loss was observed. In the condition below the room temperature, the recovery of ductility was observed with decrease of temperature, and almost no ductility loss was observed at －196℃. Therefore, it was concluded that the dominant factor of hydrogen induced ductility loss was related to hydrogen diffusivity.

Free Research Field

材料力学

Academic Significance and Societal Importance of the Research Achievements

本研究では，析出強化型Ni基超合金の水素脆化の発現に対し，水素－転位間相互作用は主要因ではなく，水素が変形中に材料内部を拡散できるという条件が破壊に対してより重要な意味をもつことを示した．この知見は，広範な温度範囲における実験データに基づくものであり，種々の水素機器の強度設計に展開できるという点で，学術的および社会的意義は大きいといえる．