The role of stress state on hydrogen cracking in Fe-Si single crystals

X. Chen, T. Foecke, M. Lii, Y. Katz, W. W. Gerberich

Research output: Contribution to journalArticlepeer-review

43 Scopus citations

Abstract

While state-of-stress effects have long been known to play a major role in hydrogen embrittlement, there has been little direct evidence outside of thickness effects on threshold stress intensities. Also, there have been recent mechanisms proposed suggesting that enhanced plasticity effects may be more dominant than enhanced decohesion effects. If true, this would mandate different state of stress effects. The goal here was to settle this issue in at least one material, that being a semi-ductile, iron base single crystal. This was achieved by examining the crack initiation site under various loading and hydrogen interaction conditions in precracked Fe-3wt.%Si single crystals oriented in {001}<010> and {001}<110>. A strong dependency of hydrogen-induced cracking on the state of stress was evidenced by the consistent nature of a mid-section initiation stage and tunneling behaviour during crack propagation. This plane stress vs plane strain effect was quantified by analysing both small scale yielding and discretized dislocation computer solutions of the stress field. It was shown that the former did not provide sufficient stress and hydrogen in the local sense while the latter provided both high stress and hydrogen enrichment to cause decohesion. Finally, an assessment is made as to whether surface observations are helpful in sorting out the micromechanical aspects of cracking. This is addressed by examining surface plasticity with respect to the interior crack profile.

Original languageEnglish (US)
Pages (from-to)997-1017
Number of pages21
JournalEngineering Fracture Mechanics
Volume35
Issue number6
DOIs
StatePublished - 1990

Bibliographical note

Funding Information:
Acknowledgements-The authorsw ould like to thank Dr N. R. Moody of SandiaN ational Laboratoriesf or performing the gas phase hydrogenc harging.T he discussionsw ith Professor R. A. Oriani at the University of Minnesotaw ere stimulatinga nd helpful.T his work was supportedb y the U.S. Departmento f Energy, Basic EnergyS ciencesM, aterials ScienceD ivision under Grant DE-FGO2-84ER45141.

Copyright:
Copyright 2014 Elsevier B.V., All rights reserved.

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