A Mechano-Chemical Coupling for Hydrogen Diffusion in Metals Based on a Thermodynamic Approach (original) (raw)
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In this paper, a finite element (FE) model is developed to investigate lattice hydrogen diffusion in a solid metal under the influence of stress and temperature gradients. This model is applied to a plate with a circular hole which is subjected to temperature and hydrogen concentration gradients. It is demonstrated that temperature gradients significantly influence hydrogen diffusion and hence susceptibility to hydrogen embrittlement when utilizing hydrogen for gas turbines.
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La quantification de la diffusion de l'hydrogène dans les matériaux est d'un grand intérêt pour nombre d'applications industrielles. Notamment, l'évaluation de l'influence de défauts qui pouvant apparaître pendant le processus de fabrication est importante. Dans ces travaux, des défauts de forme très simple, comme des défauts de soudage sont étudiés. L'influence des contraintes sur le profil de concentrations dans une pièce en Al7020 (AZ5G), ainsi que le flux d'hydrogène, le débit de fuite, l'intégrale J a été calculée à l'aide du logiciel ABAQUS pour les cas élastique pure et élasto-plastique. Les résultats montrent une augmentation significative de la concentration d'hydrogène autour de la pointe de fissure, comme attendu, et une distribution différente de l'hydrogène autour du défaut. Un modèle théorique de piégeage basé sur les cinétiques de réactions chimiques et sur les lois de diffusion étendues est présenté.
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The dynamics of hydrogen in metals with mixed grain structure is not well understood at a microscopic scale. One of the biggest issues facing the hydrogen economy is “hydrogen embrittlement” of metal induced by hydrogen entering and diffusing into the material. Hydrogen diffusion in metallic materials is difficult to grasp owing to the non-uniform compositions and structures of metal. Here a time-resolved “operando hydrogen microscope” was used to interpret local diffusion behaviour of hydrogen in the microstructure of a stainless steel with austenite and martensite structures. The martensite/austenite ratios differed in each local region of the sample. The path of hydrogen permeation was inferred from the time evolution of hydrogen permeation in several regions. We proposed a model of hydrogen diffusion in a dual-structure material and verified the validity of the model by simulations that took into account the transfer of hydrogen at the interfaces.
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FE simulation of hydrogen diffusion in duplex stainless steel
International Journal of Hydrogen Energy, 2014
Austenite phase shape a b s t r a c t ABAQUS FE simulations of hydrogen diffusion in duplex stainless steel have been performed. Three models with different ferriteeaustenite configurations have been applied and the hydrogen diffusion and the hydrogen coefficient have been evaluated as a function of austenite phase size and shape and the calculated diffusion coefficients compared to literature. Hydrogen concentration due to stress and plastic strain close to an embedded flaw has also been evaluated. An important observation is that the simulations show that when the austenite phases are saturated with hydrogen there is no large difference in the overall diffusion rate between the small and large phased models, i.e. no influence of tortuosity is observed. The work clearly demonstrates that both microstructure and flaws will influence the hydrogen diffusion and the hydrogen concentration and hence, must be taken into account when evaluating the susceptibility of hydrogen stress cracking in duplex stainless steels.
2013
ABAQUS FE simulations of hydrogen diffusion in duplex stainless steel have been performed. Hydrogen diffusion has been evaluated as a function of austenite phase size and shape. Hydrogen concentration due to stress and plastic strain close to an embedded flaw has also been evaluated. The work clearly demonstrates that both microstructure and flaws will influence the hydrogen diffusion and the hydrogen concentration and hence, must be taken into account when evaluating the susceptibility of hydrogen stress cracking in duplex stainless steels.
Theoretical Methods of Hydrogen Diffusion Calculation in Metals Review
Although there has been a significant amount of experimental research on the diffusion of hydrogen (see reviews in [12-15], very little reliable data available, especially on the distribution at temperatures below room. First principles calculations and classical approaches molecular mechanics has been used to