Change of crack initiation and propagation modes in hydrogenrelated failure of a precipitation-strengthened NI-based superalloy 718 under internal and external hydrogen conditions

Yuhei Ogawa, Osamu Takakuwa, Saburo Okazaki, Saburo Matsuoka, Hisao Matsunaga

研究成果: 著書/レポートタイプへの貢献会議での発言

抜粋

The influences of internal and external hydrogen on the tensile ductility loss and fracture behaviors of a precipitationhardened Ni-based superalloy 718 were investigated via slow strain rate tensile (SSRT) testing under hydrogen pre-charged conditions (internal hydrogen) or in gaseous hydrogen environments (external hydrogen). Severe degradation of tensile ductility was confirmed both in internal and external hydrogen conditions, and the degree of such degradation became more significant with increasing hydrogen content or hydrogen gas pressures. Moreover, the loss of tensile ductility was more pronounced in internal hydrogen conditions than external hydrogen environments. In association with such degradation of macroscopic tensile ductility, hydrogen also altered fracture mode from ductile microvoid coalescence to some brittle appearances. Whereas typical intergranular fracture combined with a decent fraction of quasi-cleavage fracture appeared on the fracture surface formed in external hydrogen environments, several types of unique faceted characteristics were found on the fracture surfaces in internal hydrogen conditions. The detailed observation of the mid-sectioned lateral surfaces of post-mortem samples successfully revealed that the observed distinctions consisted of the fracture along grain boundaries and {111} crystallographic planes including annealing twin boundaries, besides the frequency of the cracking along twin boundaries evidently increased at higher hydrogen concentration. On the basis of the series of experimental results, the initiation and propagation mechanisms of those hydrogen-induced cracks are discussed in terms of hydrogen distribution, intrinsic deformation character of the material itself as well as the alteration of plastic deformation mode caused by dissolved hydrogen.

元の言語英語
ホスト出版物のタイトルMaterials and Fabrication
出版者American Society of Mechanical Engineers (ASME)
ISBN(電子版)9780791858981
DOI
出版物ステータス出版済み - 1 1 2019
イベントASME 2019 Pressure Vessels and Piping Conference, PVP 2019 - San Antonio, 米国
継続期間: 7 14 20197 19 2019

出版物シリーズ

名前American Society of Mechanical Engineers, Pressure Vessels and Piping Division (Publication) PVP
6B-2019
ISSN(印刷物)0277-027X

会議

会議ASME 2019 Pressure Vessels and Piping Conference, PVP 2019
米国
San Antonio
期間7/14/197/19/19

All Science Journal Classification (ASJC) codes

  • Mechanical Engineering

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  • これを引用

    Ogawa, Y., Takakuwa, O., Okazaki, S., Matsuoka, S., & Matsunaga, H. (2019). Change of crack initiation and propagation modes in hydrogenrelated failure of a precipitation-strengthened NI-based superalloy 718 under internal and external hydrogen conditions. : Materials and Fabrication (American Society of Mechanical Engineers, Pressure Vessels and Piping Division (Publication) PVP; 巻数 6B-2019). American Society of Mechanical Engineers (ASME). https://doi.org/10.1115/PVP2019-93204