Hydrogen-induced intergranular failure of iron

• Published in: Acta materialia Vol. 69; pp. 275 - 282
• Main Authors: Wang, Shuai, Martin, May L., Sofronis, Petros, Ohnuki, Somei, Hashimoto, Naoyuki, Robertson, Ian M.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01-05-2014; Elsevier
• Subjects: Activation energy; Applied sciences; Dislocations; Evolution; Exact sciences and technology; Failure; Fractures; Hydrogen embrittlement; Intergranular fracture; Iron; Mechanical properties; Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology; Metals. Metallurgy; Microstructure; Transmission electron microscopy; Iron; Hydrogen embrittlement; Transmission electron microscopy; Mechanical properties; Hydrogen; Rupture
• ISSN: 1359-6454; 1873-2453
• DOI: 10.1016/j.actamat.2014.01.060

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The hydrogen embrittlement of a commercial-grade pure iron was examined by using repeated stress-relaxation tests under simultaneous cathodic hydrogen charging. The hydrogen-charged iron, containing an estimated 25.8appm H, fractured after repeated transients, with a total strain of ∼5%. The fracture mode was intergranular. Thermal activation measurements show a decrease in activation volume and free energy, which is consistent with hydrogen enhancing the dislocation velocity. The microstructure beneath the intergranular facets displays a dislocation cell structure more complex than expected for intergranular fracture and this strain-to-failure. It is proposed that hydrogen accelerates the evolution of the dislocation microstructure through the hydrogen-enhanced plasticity mechanism and this work-hardening of the matrix along with the attendant hydrogen concentration at the grain boundaries are crucial steps in causing the observed hydrogen-induced intergranular failure.