期刊
出版社
ELSEVIER SCIENCE SA
DOI: 10.1016/j.msea.2015.05.083
关键词
Hydrogen embrittlement; Martensite; Grain boundaries; EBSD; Finite element method; Mechanical characterization
类别
资金
- New Energy and Industrial Technology Development Organisation (NEDO) in Japan [14001002]
- Grants-in-Aid for Scientific Research [14001002] Funding Source: KAKEN
The purpose of this paper is to reveal the dominant factors affecting tensile fracture under a hydrogen gas atmosphere. Tensile tests were conducted in hydrogen gas with circumferentially-notched specimens of a commercial tempered martensitic steel. Two specimens were exposed to hydrogen gas for 48 h before tensile testing; the other two specimens were not pre-charged. Longitudinal cracks along the loading direction and a transverse crack perpendicular to the loading direction were observed on a cross section of the non-charged specimen, but there was only one small crack on a cross section of the pre-charged specimen. Electron back scatter diffraction, energy dispersive X-ray spectrometry and finite element method analyses were applied to clarify the relationships among the longitudinal crack, Mn segregation, microstructures of martensitic steel and hydrogen. As a result, it has been demonstrated that Mn segregation and MnS promote hydrogen-assisted cracking in the tempered martensitic steel, causing the longitudinal cracking which is a mechanically non-preferential direction in homogeneous situations. More specifically, we have shown that the role of the Mn segregation is to promote the hydrogen-enhanced decohesion effect (HEDE), which is particularly important for crack propagation in the present case. These considerations indicate that the presence of Mn is crucially important for hydrogen-assisted cracking associated with hydrogen-enhanced localized plasticity (HELP) as well as HEDE. (C) 2015 Elsevier B.V. All rights reserved.
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