Testing of the decohesion theory of hydrogen-induced crack propagation

Oriani, R. A.; Josephic, P.H.

doi:10.1016/0036-9748(72)90126-3

Cited by 75 publications

(21 citation statements)

References 2 publications

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“…A sufficient level of hydrogen concentration necessary for failure formation may thus only occur periodically, in highly localised regions, explaining the slow crack growth rate. In these microscopic regions, failure may then occur either due to the formation of microvoids [2,14,54], or due to the formation of miniscule cracks [11,12]. In both cases the crack would propagate gradually due to ductile tearing (formation of tear ridges, as observed in Fig.…”

Section: Discussionmentioning

confidence: 99%

Investigation of hydrogen assisted cracking in acicular ferrite using site-specific micro-fracture tests

Costin

Lavigne

Kotousov

et al. 2016

Materials Science and Engineering: A

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Hydrogen assisted cracking (HAC) is a common type of failure mechanism that can affect a wide range of metals and alloys. Experimental studies of HAC are cumbersome due to various intrinsic and extrinsic parameters and factors (associated with stress, hydrogen and the materials microstructure) contributing to the hydrogen crack kinetics. The microstructure of many materials consists of diverse constituents with characteristic features and mechanical properties which only occur in very small material volumes. The only way to differentiate the effect of these individual constituents on the hydrogen crack kinetics is to miniaturise the testing procedures. In this paper we present a new experimental approach to investigate hydrogen assisted crack growth in a microstructural constituent, i.e. acicular ferrite. For this purpose, sharply notched microcantilevers were fabricated with a Focus Ion Beam within this selected microscopic region. Acicular ferrite can be found in many ferrous alloys including ferritic weld metal and has specific features that control its intrinsic susceptibility to HAC. These features were characterised via Electron Backscatter Diffraction and the specimens were subsequently loaded under uncharged and hydrogen charged conditions with a nanoindenter. The outcomes of the testing, demonstrated that the threshold stress intensity factor, Kth, to initiate crack propagation in acicular ferrite ranges between 1.56 MPa m1/2 and 4.36 MPa m1/2. This range is significantly below the values of Kth reported for various ferrous alloys in standard macro-tests. This finding indicates that the mechanisms and resistance to HAC at micro-scale could be very different than at the macroscale as not all fracture toughening mechanisms may be activated at this scale level. Hydrogen assisted cracking (HAC) is a common type of failure mechanism that can affect a wide range of metals and alloys. Experimental studies of HAC are cumbersome due to various intrinsic and extrinsic parameters and factors (associated with stress, hydrogen and the materials microstructure) contributing to the hydrogen crack kinetics. The microstructure of many materials consists of diverse constituents with characteristic features and mechanical properties which only occur in very small material volumes. The only way to differentiate the effect of these individual constituents on the hydrogen crack kinetics is to miniaturise the testing procedures. In this paper we present a new experimental approach to investigate hydrogen assisted crack growth in a microstructural constituent, i.e. acicular ferrite. For this purpose, sharply notched micro-cantilevers were fabricated with a Focus Ion Beam within this selected microscopic region. Acicular ferrite can be found in many ferrous alloys including ferritic weld metal and has specific features that control its intrinsic susceptibility to HAC. These features were characterised via Electron Backscatter Diffraction and the specimens were subsequently loaded under uncharged and hydrogen charged con...

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Section: Discussionmentioning

confidence: 99%

Investigation of hydrogen assisted cracking in acicular ferrite using site-specific micro-fracture tests

Costin

Lavigne

Kotousov

et al. 2016

Materials Science and Engineering: A

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“…However, assuming that hydrogen decreases the critical stress for fatigue-crack propagation, the position of the crack tip shifts before the plastic zone expands, inhibiting the increase in d y . In terms of hydrogen-assisted fatigue-crack propagation, two possible mechanisms have been proposed: one driven by hydrogen-reduced cohesive energy [29,30], and hydrogen-assisted brittle-like fatigue-crack propagation associated with the formation and coalescence of microvoids, which is a rather ductile HELP-related mechanism [6]. When crack propagation is accelerated through a reduction in cohesive energy by hydrogen, local embrittlement at a crack tip assists the crack propagation, which is along a specific crystallographic plane.…”

Section: Discussionmentioning

confidence: 99%

Effects of hydrogen-altered yielding and work hardening on plastic-zone evolution: A finite-element analysis

Sasaki

Koyama

Higashida

et al. 2015

International Journal of Hydrogen Energy

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“…This assumed role of oxides on the crack surfaces is based primarily on observations of high strength steels, in which crack extension in low pressure hydrogen was arrested by introducing oxygen to the gas and was subsequently restarted by removing the contaminant [10,75]. A delay in the resumption of hydrogen-assisted crack extension after removal of oxygen was attributed to the time necessary for hydrogen to reduce the remaining oxygen on the metal surface [75]. The incubation times reported by Loginow and Phelps were attributed to oxides that formed on the surface of the crack tip following loading of the specimen in air which then impeded the ingress of hydrogen [13].…”

Section: Challenges Associated With Sustained Load Cracking Tests 43mentioning

confidence: 99%

Measurement and interpretation of threshold stress intensity factors for steels in high-pressure hydrogen gas.

Dadfarnia

Nibur²,

Marchi³

et al. 2010

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Threshold stress intensity factors were measured in high-pressure hydrogen gas for a variety of low alloy ferritic steels using both constant crack opening displacement and rising crack opening displacement procedures. The sustained load cracking procedures are generally consistent with those in ASME Article KD-10 of Section VIII Division 3 of the Boiler and Pressure Vessel Code, which was recently published to guide design of high-pressure hydrogen vessels. Three definitions of threshold were established for the two test methods: K THi * is the maximum applied stress intensity factor for which no crack extension was observed under constant displacement; 3 K THa is the stress intensity factor at the arrest position for a crack that extended under constant displacement; and K JH is the stress intensity factor at the onset of crack extension under rising displacement. The apparent crack initiation threshold under constant displacement, K THi *, and the crack arrest threshold, K THa , were both found to be non-conservative due to the hydrogen exposure and crack-tip deformation histories associated with typical procedures for sustainedload cracking tests under constant displacement. In contrast, K JH , which is measured under concurrent rising displacement and hydrogen gas exposure, provides a more conservative hydrogen-assisted fracture threshold that is relevant to structural components in which subcritical crack extension is driven by internal hydrogen gas pressure.4 ACKNOWLEDGMENTS

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Testing of the decohesion theory of hydrogen-induced crack propagation

Cited by 75 publications

References 2 publications

Investigation of hydrogen assisted cracking in acicular ferrite using site-specific micro-fracture tests

Investigation of hydrogen assisted cracking in acicular ferrite using site-specific micro-fracture tests

Effects of hydrogen-altered yielding and work hardening on plastic-zone evolution: A finite-element analysis

Measurement and interpretation of threshold stress intensity factors for steels in high-pressure hydrogen gas.

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