The Role of Microstructure in Hydrogen-Induced Fatigue Failure of 304 Austenitic Stainless Steel
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fluence of hydrogen on the macroscale mechanical properties of pure metals and alloys has been explored extensively.[1–9] Based on these comprehensive studies, it has been established that the alloy composition as well as the initial microstructure influence the response in either a beneficial or detrimental manner. For example, the susceptibility of austenitic stainless steel to hydrogen embrittlement is dependent on the alloy composition, with higher levels of Ni, Cr and some other elements being beneficial in general since these lower the temperature at which austenite transforms to martensite.[9] The compositional dependencies have been attributed to an increase in the stacking-fault energy as well as to stabilization of the austenite
K.E. NYGREN is with the Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801 and also with the International Institute for Carbon-Neutral Energy Research (WPI-I2CNER), Kyushu University, 744 Moto-oka, Nishi-ku, Fukuoka, Fukuoka 819-0395, Japan. A. NAGAO is with the International Institute for Carbon-Neutral Energy Research (WPII2CNER), Kyushu University and also with the Steel Research Laboratory, JFE Steel Corporation, 2-2-3 Uchisaiwai-cho, Chiyodaku, Tokyo 100-0011, Japan. P. SOFRONIS is with the International Institute for Carbon-Neutral Energy Research (WPI-I2CNER), Kyushu University and also with the Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801; I.M. ROBERTSON is with the Department of Materials Science and Engineering, University of Wisconsin Madison, Madison, WI 53706 and also with the Department of Engineering Physics, University of Wisconsin - Madison, Madison, WI 53706; Contact e-mail: [email protected]. Manuscript submitted December 30, 2019.
METALLURGICAL AND MATERIALS TRANSACTIONS A
phase.[10,11] In addition to the dependencies on the composition, it has been reported that the impact of hydrogen on the mechanical properties is sensitive to the concentration of hydrogen, with an improvement in fatigue properties being reported for hydrogen concentrations above a certain level.[12] However, it has been shown that when the effect of hydrogen on the basic mechanical properties, e.g., yield and tensile strength, of the steel is taken into account, the fatigue life data for different hydrogen concentrations follow a single power-law behavior.[13] The initial finding does highlight the importance of understanding the impact of the hydrogen concentration on the basic mechanical properties. There is less understanding of the influence of hydrogen on the microstructure generated during the plastic deformation that proceeds fracture on the fracture mode, fracture path, fatigue crack growth rate, etc. This is somewhat surprising as most if not all pure metals and their alloys exhibit extensive plastic deformation prior to failure. For example, pure Ni with a hydrogen concentration of 4660 at. ppm exhibited a higher yield and ultimate tensile strength as well as
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