Effect of Substitutional Alloying Elements (Al, Si, V, Cr, Mn, Co, Ni, Mo) on the Diffusion Coefficient of Hydrogen in &amp;alpha;-Iron

Hagi, Hideki

doi:10.2320/jinstmet1952.55.12_1283

Cited by 15 publications

(5 citation statements)

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“…These results show that D 0 , and, hence, D L , for the solid-solution composition of this steel, are reduced by two orders of magnitude compared to the lattice diffusivity of H in pure iron, while the activation energy for lattice diffusion is unchanged by alloy addition. These results follow the expected effects of solid-solution alloying elements on D L for interstitial H transport in bcc Fe, [49,50,51] as discussed later.…”

Section: A Alloying Effects On Interstitial Hydrogen Diffusionsupporting

confidence: 86%

“…Heat treatments ensured the single bcc phase without other trap states. The lattice D 0 decreased continuously with increasing amount of these alloying elements, expressed as the summed atomic percentage of M. The log D L vs 1/T relationships for varying atomic percentages of M were linear and parallel to that for pure iron, but shifted to lower rates, [49] showing that solid-solution alloying decreases D 0 while E m is unchanged. Similar trends of alloying effects were found by other investigators in 1Cr-0.5 pct Mo and 2.25Cr-1 pct Mo steels [50] and a Fe-2.25Cr-1 wt pct Mo alloy.…”

Section: H Trap Sites In Aermet 100mentioning

confidence: 83%

“…This finding is in good accordance with the literature. Hagi [49] con- temperature dependence of D L for AERMET 100 is plotted in Figure 1 for E m ϭ 10 kJ/mol. Table IV compares lattice diffusion parameters determined both experimentally and estimated analytically for AERMET 100, as well as summarized literature data for pure iron.…”

Section: A Alloying Effects On Interstitial Hydrogen Diffusionmentioning

confidence: 99%

“…Similar trends of alloying effects were found by other investigators in 1Cr-0.5 pct Mo and 2.25Cr-1 pct Mo steels [50] and a Fe-2.25Cr-1 wt pct Mo alloy. [51] The aforementioned literature data [49,50,51] were used to estimate the dependence of D 0 on atomic percentage of M for alloying with Co, Cr, Mo, and Ni in AERMET 100. The total effect of alloying on D 0 was estimated simply by summing the atomic concentration of each element, without weighting.…”

Section: H Trap Sites In Aermet 100mentioning

confidence: 99%

“…[36,69] Such experimental results are specific to a high migration energy (E m ϭ 30 to 40 kJ/mol) that is at odds with the low (10 kJ/mol) E m value indicated by the present study and substantial literature. [43,49,52] Hydrogen trapping at twin interfaces has not been studied, [48] but it is reasonable to speculate that the crystallographic correspondence of a twin interface results in a low binding energy similar to H trapped at coherent interfaces in iron. Additional work is required to resolve the role of the martensite substructure in the peak 1a trap state.…”

Section: Trap State 1: Peak 1b In Aged Alloymentioning

confidence: 99%

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Hydrogen trap states in ultrahigh-strength AERMET 100 steel

Gangloff

Scully

2004

Metall Mater Trans A

163

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Hydrogen (H) trap states and binding energies were determined for AERMET 100 (Fe-13.4Co-11Ni-3Cr-1.2Mo-0.2C), an ultrahigh-strength steel using thermal desorption methods. Three major H desorption peaks were identified in the precipitation-hardened microstructure, associated with three distinct metallurgical trap states, and apparent activation energies for desorption were determined for each. The lattice diffusivity (D L ) associated with interstitial H was measured experimentally and verified through trapping theory to yield H-trap binding energies (E b ). Solid-solution elements in AER-MET 100 reduce D L by decreasing the pre-exponential diffusion coefficient, while the activation energy for migration is similar to that of pure iron. M 2 C precipitates are the major reversible trap states, with E b of 11.4 to 11.6 kJ/mol and confirmed by heat treatment that eliminated these precipitates and the associated H-desorption peak. A strong trap state with E b of 61.3 to 62.2 kJ/mol is likely associated with martensite interfaces, austenite grain boundaries, and mixed dislocation cores. Undissolved metal carbides and highly misoriented grain boundaries trap H with a binding energy of 89.1 to 89.9 kJ/mol. Severe transgranular hydrogen embrittlement in peak-aged AERMET 100 at a low threshold-stress intensity is due to H repartitioning from a high density of homogeneously distributed and reversible M 2 C traps to the crack tip under the influence of high hydrostatic tensile stress.

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Section: A Alloying Effects On Interstitial Hydrogen Diffusionsupporting

confidence: 86%

Section: H Trap Sites In Aermet 100mentioning

confidence: 83%

Section: A Alloying Effects On Interstitial Hydrogen Diffusionmentioning

confidence: 99%

Section: H Trap Sites In Aermet 100mentioning

confidence: 99%

Section: Trap State 1: Peak 1b In Aged Alloymentioning

confidence: 99%

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Hydrogen trap states in ultrahigh-strength AERMET 100 steel

Gangloff

Scully

2004

Metall Mater Trans A

163

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Iron – Hydrogen – Molybdenum

Korniyenko

2008

Iron Systems, Part 4

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Internal hydrogen embrittlement of ultrahigh-strength AERMET 100 steel

Thomas

Scully

Gangloff

2003

Metall Mater Trans A

135

103

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Near-peak-aged AERMET 100 is susceptible to severe internal hydrogen embrittlement (IHE) at 23 ЊC, if a sufficient diffusible hydrogen content is present, compromising the high toughness of this ultrahigh-strength steel (UHSS). Evidence includes the threshold stress intensity for subcritical IHE (K TH ) as low as 10 pct of the plane-strain fracture toughness (K IC ) and a fracture-mode transition from microvoid coalescence to brittle transgranular (TG) cracking, apparently along martensite lath interfaces and cleavage planes. The K TH value decreases from a K IC value of 132 to 143 MPaΊm to 12 MPaΊm, and the amount of brittle TG fracture increases to nearly 100 pct as the concentration of diffusible H increases from essentially 0 to 8 wppm, with severe embrittlement in the 0 to 2 wppm H regime. The IHE is time dependent, as evidenced by increasing K TH values with increasing dK/dt and K-independent subcritical crack growth rates, and is attributed to diffusional H repartition from reversible trap sites to the stressed crack tip. The partition distance is ϳ1 m, consistent with the fine-scale microstructure of AERMET 100. The causes of the susceptibility of AERMET 100 to TG IHE are very high crack-tip stresses and a reservoir of mobile H trapped reversibly at (Fe,Cr,Mo) 2 C precipitates. These factors enable repartition of H to misoriented martensite lath interfaces and interstitial sites near cleavage planes, with each prone to decohesion along a connected path. Predissolved H also reduces the ductile fracture toughness of AERMET 100 at high loading rates, perhaps due to reduced void growth caused by H trapped strongly at undissolved metal carbides.

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Effect of Substitutional Alloying Elements (Al, Si, V, Cr, Mn, Co, Ni, Mo) on the Diffusion Coefficient of Hydrogen in α-Iron

Cited by 15 publications

References 0 publications

Hydrogen trap states in ultrahigh-strength AERMET 100 steel

Hydrogen trap states in ultrahigh-strength AERMET 100 steel

Iron – Hydrogen – Molybdenum

Internal hydrogen embrittlement of ultrahigh-strength AERMET 100 steel

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