Comparison of hydrogen diffusion properties and hydrogen-induced ductility loss of additively and conventionally manufactured 17-4PH stainless steel

• Published in: Engineering failure analysis Vol. 162; p. 108437
• Main Authors: Yamabe, Junichiro, Kato, Soma, Morishita, Kazuyuki, Wada, Kentaro
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.08.2024
• Subjects: 17-4PH steel; Additive manufacturing; Hydrogen embrittlement; Retained austenite; Slow strain-rate tensile testing; Retained austenite; Additive manufacturing; Hydrogen embrittlement; 17-4PH steel; Slow strain-rate tensile testing
• ISSN: 1350-6307; 1873-1961
• DOI: 10.1016/j.engfailanal.2024.108437

•Preparation of 17-4PH steel fabricated by additive manufacturing (AM).•Increased hydrogen solubility of 17-4PH steel produced by AM.•Decreased hydrogen diffusivity of 17-4PH steel produced by AM.•More pronounced hydrogen-induced ductility loss of AM material.•Correlation among ductility loss, hydrogen content and austenite fraction. Hydrogen diffusion properties and hydrogen-induced ductility loss of an as-built 17-4PH stainless steel fabricated by the additive manufacturing (AM) process were investigated using hydrogen-charged specimens exposed to high-pressure gaseous hydrogen and the results were compared with those of a conventionally manufactured 17-4PH steel under solution-treated (ST) and precipitation-hardened (PH) conditions. Peak-aged (H900) and over-aged (H1150) steels were prepared for the PH conditions. The austenite fraction of the additively manufactured materials was at most three times higher than that of the ST material. Except for the H900 material, the saturated hydrogen content of both the additively manufactured and conventional materials was dominated by the austenite in the materials. Hydrogen trapping by Cu precipitation, not the austenite, was considered to be mainly responsible for the saturated hydrogen content of the H900 material. The hydrogen diffusivity for both the additively manufactured and ST materials also decreased with higher austenite fractions. In the uncharged situation, the reduction in area (RA) of the additively manufactured material was larger than that of the conventional materials. In the hydrogen-charged situation, the additively manufactured material had a lower relative reduction in area (RRA) compared to that of the ST material, although their tested tensile strengths were similar. The hydrogen-charged additively manufactured and ST materials had quasi-cleavage (QC) surfaces. Voids elongated in the direction perpendicular to the loading direction, which corresponded to the QC facets, were observed from the longitudinal cross sections of both the additively manufactured and ST materials, suggesting the contribution of hydrogen–dislocation interactions.