scholarly journals Numerical Study of Hydrogen Trapping: Application to an API 5L X60 Steel

2012 ◽  
Vol 2012 ◽  
pp. 1-14 ◽  
Author(s):  
Patricia Castaño-Rivera ◽  
Viviana P. Ramunni ◽  
Pablo Bruzzoni
Keyword(s):  
Hydrogen Permeation ◽  
Numerical Study ◽  
Local Equilibrium ◽  
Binding Energies ◽  
Hydrogen Trapping ◽  
Free Energies ◽  
Least Squares Fit ◽  
Permeation Transient ◽  
C 50 ◽  
Trapping Sites

A numerical finite difference method is developed here to solve the diffusion equation for hydrogen in presence of trapping sites. A feature of our software is that an optimization of diffusion and trapping parameters is achieved via a non linear least squares fit. On the other hand, we have demonstrated that usual electrochemical hydrogen permeation tests are enough to assess hydrogen free energies of trapping in the range of −35 kJ/mol to −70 kJ/mol. These conclusions are obtained by assuming the presence of saturable traps in local equilibrium with hydrogen and are validated by means of simulated permeation and degassing transients. In addition, we check our model performing electrochemical hydrogen permeation tests at 30°C, 50°C, and 70°C, on an API 5L X60 as received steel state to study its trapping and diffusion properties considering only one type of trapping site. The binding energies (ΔG) and the trap densities (N) are determined by fitting the theoretical model to the experimental permeation data. The steel presents a high density of weak traps, |ΔG|<35 KJ/mol, namely, N=1.4×10−5 mol cm−3. Strong trapping sites which alter the shape of the permeation transient are also detected; their ΔG values ranged from 57 to 72 KJ/mol.

scholarly journals Numerical Evaluation on Analysis Methods of Trapping Site Density in Steels Based on Hydrogen Permeation Curve

Materials ◽  
2020 ◽  
Vol 13 (17) ◽  
pp. 3712
Author(s):  
Bangshu Yang ◽  
Li Li ◽  
Lin Cheng
Keyword(s):  
Hydrogen Permeation ◽  
Effective Diffusivity ◽  
Trapping Site ◽  
Hydrogen Trapping ◽  
Site Density ◽  
Site Characteristics ◽  
Inappropriate Utilization ◽  
Magnitude Difference ◽  
Trapping Sites ◽  
Permeation Test

Hydrogen permeation techniques have been widely utilized to extract hydrogen effective diffusivity, as well as hydrogen trapping site characteristics in steels. Several methods have been proposed to examine reversible and irreversible trapping site characteristics. However, the inappropriate utilization of these simplified models, as well as incorrect value assignment to the key parameters, can result in several orders of magnitude difference in hydrogen trapping site density. Therefore, in order to evaluate these models and verify their application prerequisites, a serial of hydrogen permeation tests were numerically simulated and examined, separately considering reversible and irreversible hydrogen trapping sites. In the meantime, suggestions were given to conduct hydrogen permeation test more effectively, and evaluate hydrogen trapping site characteristics more precisely.

Reducing Hydrogen Permeation through Metals

2011 ◽  
Vol 312-315 ◽  
pp. 560-565 ◽  
Author(s):  
Maurizio Dapor ◽  
Antonio Miotello
Keyword(s):  
Hydrogen Permeation ◽  
Great Influence ◽  
Metallic Matrix ◽  
Clean Energy ◽  
Parabolic Partial Differential Equation ◽  
Hydrogen Purification ◽  
Hydrogen Trapping ◽  
Simulation Code ◽  
Optical And Mechanical Properties ◽  
Trapping Sites

Metal–hydrogen systems are of great basic and technological interest in connection to the role of hydrogen as a clean energy carrier. Frequently, metal systems are involved in hydrogen purification, storage, and engines making use of this fuel. The presence of hydrogen in a metallic matrix gives rise to modifications of electrical, optical and mechanical properties. Hydrogen accumulation in metals may cause damage to the material by also producing fracture, thus limiting operating lifetime. Reducing the hydrogen permeation is an important task also for the fusion reactors: it is well known, indeed, that tritium is radioactive so that it is very important to be able to confine tritium during the nuclear fusion process. The theoretical study of permeation is thus of fundamental importance to obtain efficient barriers to permeation. Hydrogen trapping sites have a great influence on the hydrogen permeation through a slab sample. The diffusion of the hydrogen in a crystal is generally described by a parabolic partial differential equation with appropriate boundary conditions. The numerical simulation code PHM (Permeation of Hydrogen through Metals), realized for the study of the permeation of hydrogen in presence of trapping sites, is here described and utilized for the analysis of the influence of reversible and irreversible traps on the diffusion of hydrogen in a metal.

scholarly journals The Effect of Microstructural Characteristics on the Hydrogen Permeation Transient in Quenched and Tempered Martensitic Alloys

Metals ◽  
2018 ◽  
Vol 8 (10) ◽  
pp. 779 ◽  
Author(s):  
E. Van den Eeckhout ◽  
T. Depover ◽  
K. Verbeken
Keyword(s):  
Hydrogen Diffusion ◽  
Hydrogen Permeation ◽  
Decisive Role ◽  
Thermal Desorption Spectroscopy ◽  
Ternary Alloys ◽  
Hydrogen Trapping ◽  
Microstructural Characteristics ◽  
Hydrogen Diffusion Coefficient ◽  
Tempering Treatment ◽  
Permeation Transient

This work evaluates the permeation curve characteristics for four quenched and tempered generic, ternary alloys, each containing one specific carbide. The different carbides (W2C, Cr23C6, TiC, and V4C3, respectively) are induced by a quench and tempering treatment. The correlation is made between the different microstructural characteristics, including the carbides and the martensitic matrix, and the observed hydrogen diffusivity and thus the permeation transient. The permeation curves, obtained via the Devanathan and Stachurski method, are therefore compared with thermal desorption spectroscopy and hot extraction results. The delay of the permeation transient can be associated with the overall trap density, while the slope is related to the amount of reversible trapping sites. Generally, the obtained hydrogen permeation transient of the different ternary or Fe–C–X materials correlates with the hydrogen trapping ability. The following order of hydrogen diffusion is determined, i.e., Fe–C–V < Fe–C–Ti << Fe–C–Cr < Fe–C–W. The hydrogen trapping ability of the tempered induced carbides plays a decisive role in the value of the hydrogen diffusion coefficient.

scholarly journals The Positive Role of Nanometric Molybdenum–Vanadium Carbides in Mitigating Hydrogen Embrittlement in Structural Steels

Materials ◽  
2021 ◽  
Vol 14 (23) ◽  
pp. 7269
Author(s):  
Luis Borja Peral ◽  
Inés Fernández-Pariente ◽  
Chiara Colombo ◽  
Cristina Rodríguez ◽  
Javier Belzunce
Keyword(s):  
Diffusion Coefficient ◽  
Hydrogen Embrittlement ◽  
Hydrogen Diffusion ◽  
Hydrogen Permeation ◽  
Fatigue Crack Propagation Rate ◽  
Hydrogen Trapping ◽  
Hydrogen Atoms ◽  
High Hydrogen ◽  
Internal Hydrogen ◽  
Trapping Sites

The influence of hydrogen on the fracture toughness and fatigue crack propagation rate of two structural steel grades, with and without vanadium, was evaluated by means of tests performed on thermally precharged samples in a hydrogen reactor at 195 bar and 450 °C for 21 h. The degradation of the mechanical properties was directly correlated with the interaction between hydrogen atoms and the steel microstructure. A LECO DH603 hydrogen analyzer was used to study the activation energies of the different microstructural trapping sites, and also to study the hydrogen eggresion kinetics at room temperature. The electrochemical hydrogen permeation technique was employed to estimate the apparent hydrogen diffusion coefficient. Under the mentioned hydrogen precharging conditions, a very high hydrogen concentration was introduced within the V-added steel (4.3 ppm). The V-added grade had stronger trapping sites and much lower apparent diffusion coefficient. Hydrogen embrittlement susceptibility increased significantly due to the presence of internal hydrogen in the V-free steel in comparison with tests carried out in the uncharged condition. However, the V-added steel grade (+0.31%V) was less sensitive to hydrogen embrittlement. This fact was ascribed to the positive effect of the precipitated nanometric (Mo,V)C to alleviate hydrogen embrittlement. Mixed nanometric (Mo,V)C might be considered to be nondiffusible hydrogen-trapping sites, in view of their strong hydrogen-trapping capability (~35 kJ/mol). Hence, mechanical behavior of the V-added grade in the presence of internal hydrogen was notably improved.

Numerical study on hydrogen permeation of ferritic steel evaluated under constant load

2016 ◽  
Vol 33 (2) ◽  
pp. 149-161 ◽  
Author(s):  
S. J. Kim ◽  
D. W. Yun ◽  
H. G. Jung ◽  
K. Y. Kim
Keyword(s):  
Ferritic Steel ◽  
Hydrogen Permeation ◽  
Numerical Study ◽  
Constant Load

scholarly journals Hydrogen Trapping in bcc Iron

Materials ◽  
2020 ◽  
Vol 13 (10) ◽  
pp. 2288 ◽  
Author(s):  
Anastasiia S. Kholtobina ◽  
Reinhard Pippan ◽  
Lorenz Romaner ◽  
Daniel Scheiber ◽  
Werner Ecker ◽  
...  
Keyword(s):  
Density Functional ◽  
Atomic Level ◽  
Body Centered Cubic ◽  
Hydrogen Trapping ◽  
Functional Theory ◽  
Bcc Iron ◽  
Ferromagnetic Body ◽  
Fundamental Understanding ◽  
Crystal Lattice Defects ◽  
Trapping Sites

Fundamental understanding of H localization in steel is an important step towards theoretical descriptions of hydrogen embrittlement mechanisms at the atomic level. In this paper, we investigate the interaction between atomic H and defects in ferromagnetic body-centered cubic (bcc) iron using density functional theory (DFT) calculations. Hydrogen trapping profiles in the bulk lattice, at vacancies, dislocations and grain boundaries (GBs) are calculated and used to evaluate the concentrations of H at these defects as a function of temperature. The results on H-trapping at GBs enable further investigating H-enhanced decohesion at GBs in Fe. A hierarchy map of trapping energies associated with the most common crystal lattice defects is presented and the most attractive H-trapping sites are identified.

Gas and solution phase thermochemistry and transition energies of NH2• and NH3•+, and their aquo complexes: an ab initio study

1994 ◽  
Vol 72 (3) ◽  
pp. 471-483 ◽  
Author(s):  
Dake Yu ◽  
Arvi Rauk ◽  
David A. Armstrong
Keyword(s):  
Ab Initio ◽  
Binding Energies ◽  
Solution Phase ◽  
Interaction Energies ◽  
Free Energies ◽  
Transition Energies ◽  
Bonding Interaction ◽  
Ab Initio Structure ◽  
Total Energies ◽  
Free Energy Of Solution

Ab initio calculations were performed on several aquo complexes of NH2•, and NH3•+, and on monomeric parent species. The geometries were optimized at the HF/6-31 + G* level and the vibrational frequencies were calculated. The total energies and the binding energies of complexes were evaluated at the MP2/6-31 + G* + ZPE level of theory. Gas and aqueous solution phase thermodynamic properites of NH2• and NH3•+ and several other species were calculated. The examination of solution phase properties of the radicals was facilitated by study of the structures and transition energies of aquo complexes. H-bonding interaction energies decreased in the order [Formula: see text] but were generally stronger than σ–σ* interactions involving the unpaired electron. From calculations with the CIS method, the weak absorption observed at 520 nm for aqueous NH2• is confirmed as a 2B1 → 2A1 transition, while the stronger NH2• absorption occurring below 250 nm and the absorption of NH3•+, which rises monotonically below 370 nm, are attributed to solvent-to-solute charge transfer bands. The solution free energies and related E0 values for NH2• and NH3•+ are in agreement with those of Stanbury. The ab initio structure studies show that water protons are bound to N, and proton transfer from solvent in reaction [18], NH2• + e− + H2O → NH3 + OH−, is likely to be the dominant redox reaction of NH2• in alkaline solution. The free energy of solution of NH3•+ is shown to be larger than that of [Formula: see text].

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