PSI - Issue 19

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Available online at www.sciencedirect.com Structural Integrity Procedia 00 (2019) 000 – 000 Structural Integrity Procedia 00 (2019) 000 – 000

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Procedia Structural Integrity 19 (2019) 249–258

Fatigue Design 2019 Tensile and fatigue properties of 17-4PH martensitic stainless steels in presence of hydrogen Jean-Gabriel SEZGIN a *, Junichiro YAMABE a,b a AIST-Kyushu University Hydrogen Materials Laboratory (HydroMate), National Institute of Advanced Industrial Science and Technology (AIST), 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan b Departement of Mechanical Engineering, Fukuoka University, 8-19-1 Nanakuma, Jonan-ku, Fukuoka, 814-0180, Japan Effects of hydrogen on slow-strain-rate tensile (SSRT) and fatigue-life properties of 17-4PH H1150 martensitic stainless steel having an ultimate tensile strength of ~1GPa were investigated. Smooth and circumferentially-notched axisymmetric specimens were used for the SSRT and fatigue-life tests, respectively. The fatigue-life tests were done to investigate the hydrogen effect on fatigue crack growth (FCG) properties. The specimens, tested in air at ambient temperature, were precharged by exposure to hydrogen gas at pressures of 35 and 100 MPa at 270°C for 200 h. The SSRT properties of the H-charged specimens were degraded by hydrogen, showing a relative reduction in area (RRA) of 0.31, accompanied by mixed fracture surfaces composed of quasi cleavage (QC) and intergranular cracking (IG). The fatigue-life tests, conducted under wide test frequencies ranging from 10 -3 Hz to 10 Hz, revealed three distinct characteristics in low- and high-cycle regimes and at the fatigue limit. The fatigue limit was not degraded by hydrogen. In the high-cycle regime, the hydrogen caused FCG acceleration with an upper bound ratio of 30, accompanied by QC surfaces. In the low-cycle regime, the hydrogen caused FCG acceleration with a ratio of ~100, accompanied by QC and IG. The ordinary models such as process competition and superposition models hardly predicted the H-assisted FCG acceleration; therefore, an interaction model, successfully reproducing the experimental FCG acceleration, was newly introduced. Fatigue Design 2019 Tensile and fatigue properties of 17-4PH martensitic stainless steels in presence of hydrogen Jean-Gabriel SEZGIN a *, Junichiro YAMABE a,b a AIST-Kyushu University Hydrogen Materials Laborat ry (HydroMate), Nati n l Institute of Advanced Industrial Science and Technology (AIST), 744 Motooka, N shi-ku, Fukuoka 819-0395 ap b Departement of Mechanical Engineering, Fukuoka University, 8-19-1 Nanakuma, Jonan-ku, Fukuoka, 814-0180, Japan Abstract Effects of hydrogen on slow-strain-rate tensile (SSRT) and fatigue-life properties of 17-4PH H1150 martensitic stainless steel having an ultimate tensile strength of ~1GPa were investigated. Smooth and circumferentially- otched axisymmetric specimens were used for the SSRT and fatigue-life tests, respectively. The fatigue-life tests w re done to investigate the hydrog n effect on fatigue crack growth (FCG) properties. The specimens, tested in air at ambient temperature, were precharg d by exposure to h drogen gas at pressures of 35 and 100 MPa at 270°C for 200 h. The SSRT properties of the H-charged specimens were degraded by hydrogen, showi g a relative reduction in area (RRA) of 0.31, accompanied by mixed fracture surfaces composed of quasi cleavage (QC) an intergranular racking (IG). The fatigue-life tests, conducted under wide test frequencies ranging from 10 -3 Hz to 10 Hz, revealed three distinct characteristics in low- and high-cycle regimes and at the fatigue limit. The fatigue limit was not degraded by h drogen. In the high-cycle regime, the hydrogen caused FCG ac eleration with an upper bound ratio of 30, accompa ied by QC surfaces. In the low-cycle regime, the hydroge ca s d FCG acceleration with a ratio of ~100, ccompanied by QC and IG. The ordinary models such as pro ss comp tition a d superposition models hardly predicted the H-assiste FCG acceleration; therefore, an interaction model, successfully reproducing the experimental FCG acceleration, was newly introduced. Abstract

© 2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the Fatigue Design 2019 Organizers. © 2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the Fatigue Design 2019 Organizers. © 2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the Fatigue Design 2019 Organizers.

Keywords: hydrogen embrittlement, precipitation hardened stainless steels, fatigue life test, fatigue crack growth modelling Keywords: hydrogen embrittlement, precipitation hardened stainless steels, fatigue life test, fatigue crack growth modelling

1. Introduction 1. Introduction

The recent interest attributed to hydrogen in the energy industry raised several problematics related to exposure of material to aggressive environments. In the case of metallic alloys, a degradation of the mechanical and metallurgical properties in presence of hydrogen, also called hydrogen embrittlement (HE), was observed (Brass and Chene 1998; The recent interest attributed to hydrogen in the energy industry raised several proble atics related to exposure of material to aggressive environments. In the case of metallic alloys, a degradation of the mechanical and metallurgical properties in presence of hydrogen, also called hydrogen embrittlement (HE), was observed (Brass and Chene 1998;

2452-3216 © 2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the Fatigue Design 2019 Organizers. 2452-3216 © 2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the Fatigue Design 2019 Organizers.

2452-3216 © 2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the Fatigue Design 2019 Organizers. 10.1016/j.prostr.2019.12.027

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