2023 Fiscal Year Final Research Report

Effect of stress on hydrogen trapping state and elucidation of hydrogen embrittlement

Research Project

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Project/Area Number	19H00817
Research Category	Grant-in-Aid for Scientific Research (A)
Allocation Type	Single-year Grants
Section	一般
Review Section	Medium-sized Section 26:Materials engineering and related fields
Research Institution	Tohoku University
Principal Investigator	Akiyama Eiji 東北大学, 金属材料研究所, 教授 (70231834)
Co-Investigator(Kenkyū-buntansha)	小山元道東北大学, 金属材料研究所, 准教授 (20722705) 味戸沙耶東北大学, 金属材料研究所, 助教 (20903834) 北條智彦東北大学, 金属材料研究所, 助教 (50442463)
Project Period (FY)	2019-04-01 – 2024-03-31
Keywords	水素脆化 / 遅れ破壊 / 高強度鋼 / 水素トラップ / 昇温脱離分析 / 水素拡散 / 水素 / 破壊
Outline of Final Research Achievements	An apparatus has been developed to achieve hydrogen thermal desorption spectroscopy under stress to elucidate the mechanism of hydrogen embrittlement in high-strength steels. It consists of a tensile testing machine, a vacuum chamber and a quadrupole mass spectrometer, and the temperature is raised by energized heating. In a hydrogenated SCM435 steel with a tensile strength of 1500 MPa, the hydrogen desorption peak shifted towards lower temperatures with stress loading up to 500 MPa, suggesting a decrease in the binding energy between hydrogen and hydrogen trapping sites such as grain boundaries, dislocations and vacancies. The peak returned to the high temperature side when the stress was further increased. This was considered to be due to the introduction of dislocations, vacancies, etc. due to microplastic deformation, which increased the hydrogen trap density. Electrochemical hydrogen permeation tests showed that stress loading enhanced hydrogen diffusion.
Free Research Field	水素脆化, 腐食科学
Academic Significance and Societal Importance of the Research Achievements	水素脆化は、ボルトや自動車用鋼板などの高強度化のニーズが高まる中で、また水素エネルギー利用のため高圧水素ガスにさらされる金属材料の安全を保証する上で重要課題である。水素脆化に及ぼす金属中の水素の存在状態を解析するための昇温脱離分析は、応力条件下で行われた例は無い。本研究では、応力下での水素昇温脱離分析を可能とする、これまでに世界でも例を見ない装置を開発して応力が水素存在状態に及ぼす効果を明らかとした。本手法は水素脆化挙動の解明に有効で、今後更なる発展が期待されるもので、学術的意義があり、また得られる知見は金属材料の水素脆化問題の解決に資すると期待され、社会的意義があると考えられる