Hydrogen trapping on non metallic inclusions in cr-mo low alloy steels

Garet, M; Brass, A.M.; Haut, C.; Guttierez-Solana, F

doi:10.1016/s0010-938x(98)00008-0

Cited by 97 publications

(43 citation statements)

References 15 publications

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“…However, other researchers have reported that MnS inclusion have moderate binding energies for hydrogen. Further, these inclusions have also been reported to act as reversible trapping sites [57]. The J Q values for the two strips are discussed below, taking into account relevant observations from the literature and the precipitate distribution observed in this study.…”

Section: Effect Of Precipitatesmentioning

confidence: 72%

Effect of manganese content and microstructure on the susceptibility of X70 pipeline steel to hydrogen cracking

Hejazi

Haq

Yazdipour

et al. 2012

Materials Science and Engineering: A

117

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The influence of composition and microstructure on susceptibility to hydrogen induced cracking (HIC) was investigated in high strength pipeline steels, with Mn contents of 1.2% (standard, X70), and 0.5% (medium, MX70). The HIC resistance of the simulated coarse grained heat affected zone microstructures and normalized X70 transfer bar was also investigated. Notched and fatigue pre-cracked samples were charged with hydrogen prior to three point bend tests. The conditional fracture toughness JQ was determined. The results are discussed in relation to grain size, microstructure, composition and the type and distribution of non-metallic inclusions and precipitates. Published as "Effect of manganese content and microstructure on the susceptibility of X70 pipeline steel to hydrogen cracking" AbstractHydrogen, even in very low concentrations, can diffuse to regions of high stress concentration resulting in a degradation of mechanical properties. However, the transport of hydrogen depends on the interaction between hydrogen atoms and microstructural traps which, in turn, is related to microstructure. The influence of composition and microstructure on susceptibility to hydrogen embrittlement was investigated by selecting pipeline steels with different Mn contents, i.e., standard Mn (X70) and medium Mn (MX70) strips. The HAZ (heat affected zone) microstructures of these strips as well as a normlised transfer bar (TB) were also investigated. HAZ simulations were conducted using Gleeble thermo-mechanical machine to simulate a thermal cycle typical of inservice repairs. Notched and fatigue pre-cracked samples were subjected to electrochemical hydrogen charging using a solution of H 2 SO 4 and NaAsO 2 to achieve 2 and 4 ppm hydrogen content. Three point bend tests were conducted on as-received and hydrogen-charged samples. The X70 strip exhibited a higher J Q than the MX70 strip before and after charging, whereas the TB displayed the lowest J Q . The fracture performance of both steels deteriorated almost linearly with an increase in the hydrogen content. Because of their coarser prior austenite grain sizes and the presence of relatively hard bainitic-ferrite structure with martensite/austenite islands, the simulated HAZ microstructures of the two steels demonstrated significantly lower fracture resistance both with and without hydrogen. The results obtained were compared and discussed in relation to the grain size, microstructure, composition and the type and distribution of precipitates in the samples.

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Section: Effect Of Precipitatesmentioning

confidence: 72%

Effect of manganese content and microstructure on the susceptibility of X70 pipeline steel to hydrogen cracking

Hejazi

Haq

Yazdipour

et al. 2012

Materials Science and Engineering: A

117

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“…[14][15][16] In general, under the generalized-plastic domain, applied stress can concentrate mostly at the 2 nd phase particles and hydrogen atoms can be preferentially trapped at those sites like the case of the local-plastic range. Garet et al 43 have reported that the plastic deformation is concentrated at the inclusion, leading to cracking in the bulk of the inclusion, either at the inclusion matrix interface or at sharp extremities. With the experimental result only, however, it is not possible to clearly understand this phenomenon and therefore the numerical curve-fitting method based on appropriate equation is required.…”

Section: Resultsmentioning

confidence: 99%

Determination of Hydrogen Diffusion Parameters of Ferritic Steel from Electrochemical Permeation Measurement under Tensile Loads

Kim

Yun

Jung

2014

J. Electrochem. Soc.

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The hydrogen permeation experiment, performed with a stepwise permeation sequence involving "1 st permeation-desorption-2 nd permeation under loading, demonstrates that fine blister cracks are frequently observed on the steel surface in hydrogen charging side after the 2 nd permeation under the load over 95% of yield strength of the steel. To accommodate the experimental phenomena under the loading conditions, a numerical model is developed for determination of hydrogen diffusion parameters of the sour-resistant ferritic steel evaluated under tensile stress in plastic ranges. To solve the modified diffusion equation, a numerical finite difference method (FDM) is employed. The diffusion parameters determined by curve-fitting with the newly proposed diffusion equation indicates that, with the transition of mechanical domain from local-plasticity to generalized-plasticity, a big increase in the crack formation rate and hydrogen capture rate per irreversible trap are observed. It suggests that the transition probability for hydrogen transport from interstitial lattice site to irreversible trap site increases with the stress level. The high-strength ferritic steels used in the petrochemical industry suffer frequently from hydrogen assisted cracking (HAC) problem when they are used in a sour environment containing H 2 S. 1-3 Atomic hydrogens which result from the reduction of H + ions dissociated from H 2 S become the hydrogen molecule by the recombination reaction (H + H → H 2 ). Since H 2 S dissolved in aqueous environment suppresses this recombination reaction, the hydrogen atoms are easily adsorbed on the steel surface and diffuse into the steel matrix.4,5 The hydrogen atoms absorbed in the steel are reversibly or irreversibly trapped at various metallurgical defects in the steel, often resulting in the HAC failure. 2,6 With the depletion of high quality oil and gas, the HAC failure may become serious engineering problem for the highstrength steel pipes transporting and/or processing the low quality oil and gas containing a large amount of H 2 S.The HAC problem can be classified into two categories depending on the source of hydrogen and stress level; one is hydrogen induced cracking (HIC) occurring under no applied stress 2,6 and the other is sulphide stress cracking (SSC) occurring under applied tensile stress or residual stress. 7,8 In order to understand clearly HAC failure of the steels, the combined effect of hydrogen and applied stress should be evaluated together. A number of considerable efforts have been directed to evaluate the influence of applied tensile stress on the hydrogen diffusion behavior in the steel employing the electrochemical permeation technique.9-12 It has been generally accepted that the applied tensile stress in elastic range has no significant effect on the hydrogen diffusivity but increases the steady-state permeation flux due to the elastically expanded lattice. 10,12,13 On the other hand, a significant decrease in the permeation current has been observed in body centered cubic (BCC...

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“…Lee and Lee [15] considered MnS inclusions to be strong irreversible trapping sites for hydrogen. However, Garet et al [16] reported that MnS particles act as reversible trapping sites since they have moderate binding energies. They also reported that the trapping efficiency increased with sulphur content.…”

Section: Introductionmentioning

confidence: 99%

Effect of microstructure and composition on hydrogen permeation in X70 pipeline steels

Haq

Muzaka

Dunne

et al. 2013

International Journal of Hydrogen Energy

148

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The influence of microstructure and composition on permeation of hydrogen in 1.2 and 0.5 wt.% Mn X70 pipeline steels after different processing was investigated using an electrochemical permeation technique. For 1.2 wt.% Mn (standard Mn) steel, the microstructure of normalised transfer bar was coarse equiaxed ferrite grains. This sample exhibited the highest diffusivity, followed by transfer bar, with a mixed ferriteebainitic ferrite microstructure; and hot rolled strip, with fine elongated ferrite grains. The 0.5 wt.% Mn (medium Mn) strip displayed lower diffusivity than the 1.2 wt.% Mn strip, due to hydrogen trapping by finer ferrite grains and a higher density of carbonitride precipitates. Moreover, the medium Mn strip exhibited a uniform microstructure and consequently similar diffusion coefficients for the edge and centreline regions, whereas the finer grains of the edge region of the standard Mn strip resulted in a lower diffusivity than the centreline region. Copyright © 2012, Hydrogen Energy Publications, LLC. AbstractThe influence of microstructure and composition on permeation of hydrogen in 1.2 and 0.5 wt.% Mn X70 pipeline steels after different processing was investigated using an electrochemical permeation technique. For 1.2 wt.% Mn (standard Mn) steel, the microstructure of normalised transfer bar was coarse equiaxed ferrite grains. This sample exhibited the highest diffusivity, followed by transfer bar, with a mixed ferrite -bainitic ferrite microstructure; and hot rolled strip, with fine elongated ferrite grains.The 0.5 wt.% Mn (medium Mn) strip displayed lower diffusivity than the 1.2 wt.% Mn strip, due to hydrogen trapping by finer ferrite grains and a higher density of carbonitride precipitates.Moreover, the medium Mn strip exhibited a uniform microstructure and consequently similar diffusion coefficients for the edge and centreline regions, whereas the finer grains of the edge region of the standard Mn strip resulted in a lower diffusivity than the centreline region.

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Hydrogen trapping on non metallic inclusions in cr-mo low alloy steels

Cited by 97 publications

References 15 publications

Effect of manganese content and microstructure on the susceptibility of X70 pipeline steel to hydrogen cracking

Effect of manganese content and microstructure on the susceptibility of X70 pipeline steel to hydrogen cracking

Determination of Hydrogen Diffusion Parameters of Ferritic Steel from Electrochemical Permeation Measurement under Tensile Loads

Effect of microstructure and composition on hydrogen permeation in X70 pipeline steels

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