Crack growth from internal hydrogen—temperature and microstructural effects in 4340 steel

vne, T. L; Chen, X. F.; Kaczorowski, M.

doi:10.1007/bf02662593

Cited by 94 publications

(43 citation statements)

References 26 publications

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“…Striations approximately 1 mm in spacing were also reported on the intergranular fracture surface of hydrogen-precharged AISI 4340 steel subjected to a compact tensile test under sustained load. 24) The spacing was close to that of martensite lath. Impurity segregation along prior austenite grain boundaries increases susceptibility to HE, 25) but there still is a problem that intergranular fracture is governed by either the cohesive strength of the boundary itself or deformation structures close to the boundaries.…”

Section: Fractographic Featuressupporting

confidence: 54%

Advances in Physical Metallurgy and Processing of Steels. Function of Hydrogen in Embrittlement of High-strength Steels.

Nagumo

2001

ISIJ International

229

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Various models so far proposed for the mechanism of hydrogen embrittlement (HE) of steels are critically reviewed with respect to the manifestation of hydrogen in the fracture process. Recent studies that elucidate the hydrogen states and their relevance to HE are discussed. Particular attention is paid to the role of deformation-induced defects that interact with hydrogen. A model is proposed in which increased vacancy density and agglomeration lead to the promotion of failure. The model ascribes HE to the context of ductile fracture in which vacancies play the primary role.KEY WORDS: hydrogen embrittlement; fracture; lattice defect; fractography; thermal desorption analysis; high-strength steel. Fig. 1. Outline of the proposed mechanisms of HE due to hydrogen states in materials.

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Section: Fractographic Featuressupporting

confidence: 54%

Advances in Physical Metallurgy and Processing of Steels. Function of Hydrogen in Embrittlement of High-strength Steels.

Nagumo

2001

ISIJ International

229

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“…Similar models, albeit with a phenomenological law for degradation of cohesive strength, have also been proposed. 35,36 The interaction of hydrogen with defects in crystalline materials is reviewed at length in Ref. 14.…”

Section: Introductionmentioning

confidence: 99%

Effect of atomic scale plasticity on hydrogen diffusion in iron: Quantum mechanically informed and on-the-fly kinetic Monte Carlo simulations

et al. 2008

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We present an off-lattice, on-the-fly kinetic Monte Carlo (KMC) model for simulating stress-assisted diffusion and trapping of hydrogen by crystalline defects in iron. Given an embedded atom (EAM) potential as input, energy barriers for diffusion are ascertained on the fly from the local environments of H atoms. To reduce computational cost, on-the-fly calculations are supplemented with precomputed strain-dependent energy barriers in defect-free parts of the crystal. These precomputed barriers, obtained with high-accuracy density functional theory calculations, are used to ascertain the veracity of the EAM barriers and correct them when necessary. Examples of bulk diffusion in crystals containing a screw dipole and vacancies are presented. Effective diffusivities obtained from KMC simulations are found to be in good agreement with theory. Our model provides an avenue for simulating the interaction of hydrogen with cracks, dislocations, grain boundaries, and other lattice defects, over extended time scales, albeit at atomistic length scales.

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“…The magnitude of the peak stress, <7 W , is about 3.50ys for a strain-hardening material such as Alloy X-750. Assuming plane strain conditions, the peak hydrostatic stress is about 50% to 60% of the peak normal stress or twice the yield strength, which is within 5% of the peak hydrostatic stress assumed by Gerberich et al (19) This relationship was incorporated into Eq. (2) to estimate the maximum C/C 0 ratios as functions of temperature and yield strength (see Figure 12).…”

mentioning

confidence: 81%

Hydrogen embrittlement, grain boundary segregation, and stress corrosion cracking of alloy X-750 in low-and high-temperature water

Mills

Lebo

Kearns

1999

Metall Mater Trans A

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The nature of intergranular stress corrosion cracking (SCO of Alloy X-750 was characterized in low and high temperature water by testing as-notched and precracked fracture mechanics specimens. Materials given the AH, BH and HTH heat treatments were studied. While all heat treatments were susceptible to rapid low temperature crack propagation (LTCP) below 150°C, Conditions AH and BH were particularly susceptible. Low temperature tests under various loading conditions (e.g., constant displacement, constant load and increasing load) revealed that the maximum stress intensity factors («*"«) from conventional rising load tests provide conservative estimates of the critical loading conditions in highly susceptible heats, regardless of the load path history. For resistant heats, Kfw provides a reasonable, but not necessarily conservative, estimate of the critical stress intensity factor (K,) for LTCP. Testing of as-notched specimens showed that LTCP will not initiate at a smooth surface or notch, but if a crack-like defect is present it readily occurs. Comparison of the cracking response in water with that for hydrogen-precharged specimens tested in air demonstrated that LTCP is associated with embrittlement of grain boundaries by hydrogen generated by the corrosion reaction at the crack tip. Equivalent activation energies for Stage II LTCP rates (11.3 kcal/mol) and hydrogen diffusion (11.5 kcal/mol) indicate that hydrogen diffusion to the peak stress regions ahead of a crack is the rate controlling process. Auger analysis showed that heat treatment and heat-to-heat variability was associated with phosphorus and sulfur segregation to grain boundaries. Above 150°C, rapid cracking does not occur due to an increase in fracture resistance and decrease in the degree of hydrogen enrichment. SCC initiation and growth does occur in high temperature water (>250°C), but crack growth rates are orders of magnitude lower than LTCP rates. The SCC resistance of HTH heats was far superior to that for AH heats as crack initiation times were two to three orders of magnitude greater and growth rates were one to two orders of magnitude lower.

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Crack growth from internal hydrogen—temperature and microstructural effects in 4340 steel

Cited by 94 publications

References 26 publications

Advances in Physical Metallurgy and Processing of Steels. Function of Hydrogen in Embrittlement of High-strength Steels.

Advances in Physical Metallurgy and Processing of Steels. Function of Hydrogen in Embrittlement of High-strength Steels.

Effect of atomic scale plasticity on hydrogen diffusion in iron: Quantum mechanically informed and on-the-fly kinetic Monte Carlo simulations

Hydrogen embrittlement, grain boundary segregation, and stress corrosion cracking of alloy X-750 in low-and high-temperature water

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