Study on hydrogen embrittlement of Ni alloy

2023 Fiscal Year Final Research Report

• Project/Area Number: 21K04702
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 26040:Structural materials and functional materials-related
• Research Institution: National Institute for Materials Science
• Principal Investigator: TSUZAKI Kaneaki 国立研究開発法人物質・材料研究機構, その他部局等, フェロー (40179990)
• Project Period (FY): 2021-04-01 – 2024-03-31
• Keywords: 構造材料 / 水素脆化 / 粒界破壊 / ミクロ組織制御 / Ni合金 / 温間加工

Outline of Final Research Achievements

Cylindrical smooth tensile specimens were prepared from solution-treated and warm-rolled Ni-20mass%Cr alloys, which were melted, forged,rolled, and heat-treated using NIMS facilities. Half of the specimens were exposed to 100MPa hydrogen gas at 270°C for 300 hours to introduce hydrogen atoms uniformly into the specimens. The results of tensile tests at room temperature showed that the solution annealed material showed a decrease in tensile strength from 580 MPa to 340 MPa due to hydrogen charging, whereas the warm-rolled material showed a high tensile strength of 880 MPa even with hydrogen charging, thus achieving the target. Furthermore, microstructural observations confirmed that hydrogen-induced intergranular fracture was suppressed in the warm-rolled material.

Free Research Field

構造金属材料

Academic Significance and Societal Importance of the Research Achievements

本研究の目的は次の二つである： (1) Ni-20%Cr合金の水素脆化粒界破壊の素過程を解明すること；(2)ミクロ組織制御によって耐水素脆性に優れたNi-20%Cr合金を創出すること。FCC金属の水素誘起粒界破壊が不連続かつ離散的に起こるという事実は従来認識を超えるものであり、本研究の成果は金属材料の水素脆性機構の理解に新たな視点を与えるものである。また、本研究で提案実施したミクロ組織制御法は油井管部材にとって実現可能なプロセスであることに加え、部材をさらに高強度化できるため、高深度高腐食井における喫緊課題である高耐食性と高強度を両立させた油井管部材の創製に貢献することができる。