Hydrogen Embrittlement Of Metals Research Articles

The Effect of Grain Boundary Misorientation on Hydrogen Flux Using a Phase‐Field‐Based Diffusion and Trapping Model

Understanding hydrogen–grain boundary (GB) interactions is critical to the analysis of hydrogen embrittlement in metals. This work presents a mesoscale fully kinetic model to investigate the effect of GB misorientation on hydrogen diffusion and trapping using phase‐field‐based representative volume elements (RVEs). The flux equation consists of three terms: a diffusive term and two terms for high and low angle grain boundary (H/LAGB) trapping. Uptake simulations show that decreasing the grain size results in higher hydrogen content due to increasing the GB density. Permeation simulations show that GBs are high‐flux paths due to their higher enrichment with hydrogen. Since HAGBs have higher enrichment than LAGBs, due to their higher trap‐binding energy, they generally have the highest hydrogen flux. Nevertheless, the flux shows a convoluted behavior as it depends on the local concentration, alignment of GB with external concentration gradient as well as the GB network connectivity. Finally, decreasing the grain size resulted in a larger break‐through time and a larger steady‐state exit flux.

A new approach for in situ electrochemical nanoindentation: Side charging as a promising alternative

Understanding hydrogen embrittlement in metals is an essential task for the energy transition, where hydrogen plays a key role. Besides the economic consequences of embrittlement, safety aspects are a very important factor to consider. Therefore, materials need to be screened in order to evaluate their mechanical response under hydrogen influence. Besides macroscopic mechanical testing, in situ electrochemical nanoindentation and micromechanical testing —in general— represent promising methods as they allow to characterize individual microstructural features. In the established “front-side” charging approach, hydrogen enters the sample at the same surface on which indentation tests are performed. An alternative is “back-side” charging, where hydrogen is introduced at the opposite side of the indentation location. In the present study, a novel “side” charging cell was designed and the results were compared to those obtained by “front-side” charging. For this purpose, a ferritic steel with high chromium content (X6Cr17) underwent a grain coarsening heat treatment to ensure that multiple nanoindentation experiments can be performed within a single grain. A similar grain orientation was tested with both charging approaches. The novel “side” charging cell design outperforms the stiffness of the reference front-side charging cell by 60 %. Both cell designs yielded constant Young's moduli before, during and several hours after charging. The hardness increased during charging due to hydrogen uptake, whereas the hardness settled several hours after charging to the values before charging started. The presence of hydrogen at the indentation side was confirmed by in situ X-ray diffraction using a self-reporting titanium film.

Hydrogen diffusion dynamics on [formula omitted] surface: A mechanism of hydrogen-induced failure

Hydrogen-induced failure (embrittlement as the primary source) is a significant concern for retrofitting existing pipelines to transport hydrogen. One of the major factors associated with hydrogen embrittlement of metals is hydrogen diffusion. Therefore, understanding the modes and dynamics of hydrogen diffusion into metals is critical for understanding better and acting to limit hydrogen-induced damage to metals. It is well established that transition metals catalyze the dissociation of molecular hydrogen into atomic hydrogen even at room temperature. The atomic hydrogen diffuses through the metal surface, and this causes degradation. Understanding atomic hydrogen diffusion dynamics is critical to reducing hydrogen embrittlement. This work presents atomic hydrogen diffusion dynamics along and into Fe(100) surfaces. The results indicated that diffusion of atomic hydrogen along the surface is favored over surface-to-subsurface diffusion. Once hydrogen diffuses to the subsurface layer, the barrier for further hydrogen diffusion into the subsequent layers is relatively lower. The methodology presented here of atomic hydrogen diffusion under dynamic relaxation into metal surface can be used to study the effect of the metal's chemical composition and structure on the hydrogen diffusion rate. This allows for screening various strategies to reduce hydrogen diffusion into metals and guide the design of degradation prevention strategies.

Hydrogen trapping and embrittlement in metals – A review

Hydrogen embrittlement in metals (HE) is a serious challenge for the use of high strength materials in engineering practice and a major barrier to the use of hydrogen for global decarbonization. Here we describe the factors and variables that determine HE susceptibility and provide an overview of the latest understanding of HE mechanisms. We discuss hydrogen uptake and how it can be managed. We summarize hydrogen trapping and the techniques used for its characterization. We also review literature that argues that hydrogen trapping can be used to decrease HE susceptibility. We discuss the future research that is required to advance the understanding of HE and hydrogen trapping and to develop HE-resistant alloys.

Application of Barrier Coatings for Protection Against Hydrogen Embrittlement of Metals

Application of Barrier Coatings for Protection Against Hydrogen Embrittlement of Metals

Review of Hydrogen Embrittlement in Metals: Hydrogen Diffusion, Hydrogen Characterization, Hydrogen Embrittlement Mechanism and Prevention

Hydrogen dissolved in metals as a result of internal and external hydrogen can affect the mechanical properties of the metals, principally through the interactions between hydrogen and material defects. Multiple phenomena such as hydrogen dissolution, hydrogen diffusion, hydrogen redistribution and hydrogen interactions with vacancies, dislocations, grain boundaries and other phase interfaces are involved in this process. Consequently, several hydrogen embrittlement (HE) mechanisms have been successively proposed to explain the HE phenomena, with the hydrogen-enhanced decohesion mechanism, hydrogen-enhanced localized plasticity mechanism and hydrogen-enhanced strain-induced vacancies being some of the most important. Additionally, to reduce the risk of HE for engineering structural materials in service, surface treatments and microstructural optimization of the alloys have been suggested. In this review, we report on the progress of the studies on HE in metals, with a particular focus on steels. It focuses on four aspects: (1) hydrogen diffusion behavior; (2) hydrogen characterization methods; (3) HE mechanisms; and (4) the prevention of HE. The strengths and weaknesses of the current HE mechanisms and HE prevention methods are discussed, and specific research directions for further investigation of fundamental HE mechanisms and methods for preventing HE failure are identified.

Finite Element Modeling of the Behavior of a Hollow Cylinder in a Hydrogen-Containing Environment

The two main research orientations on the problem of hydrogen embrittlement are examined: the study of fundamental principles and the disclosure of micromechanisms and the relation between hydrogen embrittlement and metal aging; the development of models and methods for predicting the kinetics of change in stress-strain state and for evaluating the longevity of structures subjected to hydrogen embrittlement. The state of the problem of hydrogen embrittlement of metals in the first direction is briefly analyzed. More attention is paid to the importance of predicting the behavior of charged metal structures under the influence of hydrogen embrittlement. We then examine the use of finite element modeling using the ANSYS software to compute the calculation analysis of a hollow cylinder subjected to internal and external pressures and hydrogen embrittlement. The cylinder material is nonlinear elastic and its properties depend on the hydrogen concentration at each point of the cylinder. Consideration is given to the influence of the rigidity of the stress state and the hydrogen concentration on the diffusion kinetics of hydrogen in the cylinder body. The problem is solved in time steps. The distributions of the hydrogen concentration and the stresses for a quarter of the volume of the cylinder are given, as well as the graphs of these values ​​according to the thickness of the wall of the cylinder at different times. It is shown that the ANSYS software package adapted to the resolution of such problems can model the behavior of different structures in a hydrogen-containing environment, taking into account the effects caused by both the influence of hydrogen on mechanical properties of the material and by the stress state of the structures, as well as by the influence of the stress state on the interaction kinetics of hydrogen with the structures.

Quantification of solute deuterium in titanium deuteride by atom probe tomography with both laser pulsing and high-voltage pulsing: influence of the surface electric field

Atom probe tomography (APT) has been increasingly used to investigate hydrogen embrittlement in metals due to its unique capacity for direct imaging of H atoms interacting with microstructural features. The quantitativeness of hydrogen measurements by APT is yet to be established in views of erroneous compositional measurements of bulk hydrides and the influence of spurious hydrogen, e.g. residual gas inside the analysis chamber. Here, we analyzed titanium deuteride (approx. 65.0 at%–66.6 at% D) in lieu of hydride to minimize the overlap with residual gas, both with laser pulsing and high-voltage (HV) pulsing. Strategies were deployed to prevent H pick-up during specimen fabrication, including preparing specimens at cryogenic temperature. The measured composition of deuterium by APT with laser pulsing decreases significantly with the applied laser pulse energy, which is interpreted with regards to the strength of the corresponding surface electrostatic field, as assessed by the evolution of charge-state ratio. In contrast, compositional analyses with HV pulsing are roughly independent of the applied experimental parameters, although approx. 15 at%–20 at% off the nominal composition. Aided by plotting paired mass-to-charge correlations, the mechanisms of composition bias in both pulsing modes are discussed. A special emphasis is placed on the local variations of the measured composition as a function of the local electric field across the specimen’s surface, which is not uniform due to asymmetric heat distribution related to the localized laser absorption and the faceted nature of surface caused by the crystallographic structure. Our investigations demonstrate the challenges of quantitative analysis of solute deuterium by APT but nevertheless provide insight to achieving the best possible experimental protocol.

The Role of Hydrogen in Hydrogen Embrittlement of Metals: The Case of Stainless Steel

Hydrogen embrittlement (HE) of metals has remained a mystery in materials science for more than a century. To try to clarify this mystery, tensile tests were conducted at room temperature (RT) on a 316 stainless steel (SS) in air and hydrogen of 70 MPa. With an aim to directly observe the effect of hydrogen on ordering of 316 SS during deformation, electron diffraction patterns and images were obtained from thin foils made by a focused ion beam from the fracture surfaces of the tensile specimens. To prove lattice contraction by ordering, a 40% CW 316 SS specimen was thermally aged at 400 °C to incur ordering and its lattice contraction by ordering was determined using neutron diffraction by measuring its lattice parameters before and after aging. We demonstrate that atomic ordering is promoted by hydrogen, leading to formation of short-range order and a high number of planar dislocations in the 316 SS, and causing its anisotropic lattice contraction. Hence, hydrogen embrittlement of metals is controlled by hydrogen-enhanced ordering during RT deformation in hydrogen. Hydrogen-enhanced ordering will cause the ordered metals to be more resistant to HE than the disordered ones, which is evidenced by the previous observations where furnace-cooled metals with order are more resistant to HE than water-quenched or cold worked metals with disorder. This finding strongly supports our proposal that strain-induced martensite is a disordered phase.

Hydrogen embrittlement controlled by reaction of dislocation with grain boundary in alpha-iron

Hydrogen atoms absorbed by metals in hydrogen-containing environments can lead to the premature fracture of the metal components used in load-bearing conditions. Since metals used in practice are mostly polycrystalline, grain boundaries (GBs) can play an important role in hydrogen embrittlement of metals. Here we show that the reaction of GBs with lattice dislocations is a key component in hydrogen embrittlement mechanism for polycrystalline metals. We use atomistic modeling methods to investigate the mechanical response of GBs in alpha-iron with various hydrogen concentrations. Analysis indicates that dislocations impingement and emission on the GB can provoke it to locally transform into an activated state with a more disordered atomistic structure, and introduce a local stress concentration. The activation of the GB segregated with hydrogen atoms can greatly facilitate decohesion of the GB. We propose a hydrogen embrittlement model that can give better explanation of many experimental observations.

Review of hydrogen-assisted cracking models for application to service lifetime prediction and challenges in the oil and gas industry

Abstract The present manuscript reviews state-of-the art models of hydrogen-assisted cracking (HAC) with potential for application to remaining life prediction of oil and gas components susceptible to various forms of hydrogen embrittlement (HE), namely, hydrogen-induced cracking (HIC), sulfide stress cracking (SSC), and HE-controlled stress corrosion cracking (SCC). Existing continuum models are compared in terms of their ability to predict the threshold stress intensity factor and crack growth rate accounting for the complex couplings between hydrogen transport and accumulation at the fracture process zone, local embrittlement, and subsequent fracture. Emerging multiscale approaches are also discussed, and studies relative to HE in metals and especially steels are presented. Finally, the challenges that hinder the application of existing models to component integrity assessment and remaining life prediction are discussed with respect to identification of model parameters and limitations of the fracture similitude, which paves the way to new directions for further research.

Anisotropy of hydrogen diffusion in nickel single crystals: the effects of self-stress and hydrogen concentration on diffusion

Hydrogen diffusion has an important role in solute-dependent hydrogen embrittlement in metals and metallic alloys. In spite of extensive studies, the complexity of hydrogen diffusion in solids remains a phenomenon that needs to be clarified. In this paper, we investigate the anisotropy of hydrogen diffusion in pure nickel single crystals using both an experimental approach and a thermodynamic development. As a first approximation, experimental data from electrochemical permeation and thermal desorption spectroscopy are described using the classical Fick’s laws and an apparent diffusion tensor. Within a thermodynamic framework, the diffusion equation can be derived from Fick’s laws with an apparent diffusion coefficient which contains an added solute content dependent term β. This term is due to the elastic strain field associated with the insertion of solute atoms. For nickel crystals, the dependence of β on the crystallographic orientation arises from the elastic anisotropy. Additionally, our results elucidate the discrepancies between the thermodynamic model and experimental observations of the effect of the solute concentration on the diffusion process. Moreover, this highlights the importance of the impact of hydrogen on vacancy formation and the subsequent consequences on the anisotropy of the apparent diffusion coefficient.

A critical review and experimental analysis of the equation recommended by ASTM G148-97 and ISO 17081: 2004 for the calculation of the hydrogen diffusivity in metals and alloys

Since its discovery in 1864 by Cailletet [1], hydrogen embrittlement of metals has been the target of several investigations. In 1962 Devanathan and Stachurski [2], developed an electrochemical technique for hydrogen permeation. There are now three methods to produce hydrogen: galvanostatic, potentiostatic and under open circuit potential in an acid medium (OCPAc). Regulations in Refs. [3] and [4] standardized hydrogen permeation only by the potentiostatic method. In the present work an experimental methodology for OCPAc procedure was developed. The authors conclude that the equation of diffusivity proposed by ISO 17081 and ASTM G148-97 [3] and [4] can lead to underestimated diffusivity values. The authors conclude the mathematical model proposed for the OCPAc method presented a satisfactory fit to the experimental data. Diffusivity values were calculated not only for this case but also for all other methods. However, to evaluate and explore the limits of the proposed methodology, the authors recommend its use with other metals and alloys.

Chemomechanical Origin of Hydrogen Trapping at Grain Boundaries in fcc Metals.

Hydrogen embrittlement of metals is widely observed, but its atomistic origins remain little understood and much debated. Combining a unique identification of interstitial sites through polyhedral tessellation and first-principles calculations, we study hydrogen adsorption at grain boundaries in a variety of face-centered cubic metals of Ni, Cu, γ-Fe, and Pd. We discover the chemomechanical origin of the variation of adsorption energetics for interstitial hydrogen at grain boundaries. A general chemomechanical formula is established to provide accurate assessments of hydrogen trapping and segregation energetics at grain boundaries, and it also offers direct explanations for certain experimental observations. The present study deepens our mechanistic understanding of the role of grain boundaries in hydrogen embrittlement and points to a viable path towards predictive microstructure engineering against hydrogen embrittlement in structural metals.

Decohesive Concept of the Interaction of Hydrogen with Metals

We consider some concepts of the interaction of hydrogen with metals (iron and its alloys) under loads in hydrogen-containing media and, in particular, their hydrogen embrittlement. This problem is analyzed in numerous works, where different concepts and models are proposed for the substantiation of the mechanisms of hydrogen embrittlement of metals. However, these concepts do not enable us to understand the dual character of the action of hydrogen on the deformation of metals, i.e., the facilitation of their plastic deformation and embrittlement. We describe the decohesive concept of hydrogen–metal interaction based on which it is possible to explain the processes of plasticization of metals in the initial stage of deformation and their embrittlement in the course of subsequent deformation. We also present a survey of investigations in this direction carried out by researchers of the Karpenko Physicomechanical Institute of the Ukrainian National Academy of Sciences.

Hydrogen defects in tetragonal ZrO2studied using density functional theory

In the energy-structure paradigm, we analyzed the defects that can arise in tetragonal zirconium oxide (T-ZrO2) involving the hydrogen atom or the hydrogen molecule using density functional theory. Our results indicate that the dominant hydrogen defect under reducing conditions is H(·)(0), a complex formed between the hydride ion and a doubly charged oxygen vacancy. This result is consistent with the experimental observation that under reducing conditions, the solubility of hydrogen is proportional to the degree of hypostoichiometry of T-ZrO2. Under oxidizing conditions we found three different hydrogen defects, each predominating in a specific range of the chemical potential of electrons. Starting from the valence band top toward the conduction band bottom, these defects are the interstitial proton, H(·)(i), a complex formed between two hydrogen species and a zirconium vacancy with a net effective charge of (2-), (2H)"(Zr), and finally a complex similar to the latter but with a net effective charge of (4-), (H(2))'''(Zr). In (2H)"(Zr)the two hydrogens exist in the form of hydroxyl groups, while in (H(2))" " (Zr) they exist in the form of a hydrogen molecule. In addition, we found that up to three hydrogen species can favorably accumulate in a zirconium vacancy under oxidizing conditions. The clustering of hydrogen in cation vacancies can be a precursor for the deleterious effects of hydrogen on the mechanical properties and stability of metal oxides, in analogy with hydrogen embrittlement in metals. Finally we observed a red-shift and a blue-shift for the vibrational frequencies of all the hydroxyl groups and all the hydrogen molecules, respectively, in T-ZrO2 when compared to the gas phase frequencies. This is an important characteristic for guiding future experimental efforts to detect and identify hydrogen defects in T-ZrO2. The insights presented in this work advance our predictive understanding of the degradation behavior of T-ZrO2 as a corrosion resistant passive layer, as a gate dielectric and in biomedical applications.

Influence of pH on Hydrogen Absorption in Duplex Stainless Steel

With rising demands, oil and gas exploration of high-pressure high-temperature (HPHT) wells are increasing worldwide. Due to aggressiveness of HPHT environments, piping and equipments are constructed with high-strength corrosion resistant alloys (CRAs). Duplex stainless steel is one of the candidate alloys that offer high strength along with corrosion resistance. It possesses the advantages of both austenitic and ferritic stainless steels and hence, the name duplex or dual phase stainless steel. In order to control corrosion, cathodic protection is commonly being employed on the structures and equipment. Cathodic protection is accomplished by applying a direct current to the structure which causes the structure potential to change from the natural corrosion potential (Ecorr). The required cathodic protection current is supplied by sacrificial anode materials or by an impressed current system. Hydrogen embrittlement (HE) is an associated phenomenon, which results in the production of hydrogen ions, leading to its absorption in the protected metal and subsequent hydrogen embrittlement of metals and welds. To prevent this embrittlement, cathodic protection is closely studied in terms of finding the critical potential, pH, temperature etc. that does not cause hydrogen embrittlement. This paper describes the study carried out to find the role of pH on the absorption of hydrogen in Duplex Stainless steel. It has been observed that at a critical pH, hydrogen intake in the sample is very high, as compared to the pH below and above the critical pH. Critical pH observed for duplex stainless steel is a trade of between hydrogen evolution and absorption for given duplex structure.

First-Principles Study of Molecular Hydrogen Adsorption and Dissociation on AlnCr (n = 1–13) Clusters

Hydrogen adsorption dissociation on clusters is a widely studied subject that provides the opportunity to gain a basic understanding of the complicated nature of many interesting problems, such as hydrogen embrittlement of metals, catalytic processes, hydrogen storage, etc. In this study, I present density functional calculations of H2 adsorption and dissociation on small-sized Al(n)Cr clusters for n = 1-13. My results show that H2 is easily physically absorbed on the top Cr atom of AlnCr clusters with a side-on orientation rather than an end-on orientation. In addition, I investigate a possible dissociation mechanism and dissociation pathway of H2 on selected Al2Cr and Al7Cr. My findings suggest that the hydrogen dissociation behavior on Al(n)Cr clusters characterized by the activation barrier and reaction energy can be tuned by controllable doping. Thus, Al2Cr and Al7Cr clusters might serve as highly efficient and low-cost catalysts for hydrogen dissociation.

Atomic mechanism and prediction of hydrogen embrittlement in iron

Hydrogen embrittlement in metals has posed a serious obstacle to designing strong and reliable structural materials for many decades, and predictive physical mechanisms still do not exist. Here, a new H embrittlement mechanism operating at the atomic scale in α-iron is demonstrated. Direct molecular dynamics simulations reveal a ductile-to-brittle transition caused by the suppression of dislocation emission at the crack tip due to aggregation of H, which then permits brittle-cleavage failure followed by slow crack growth. The atomistic embrittlement mechanism is then connected to material states and loading conditions through a kinetic model for H delivery to the crack-tip region. Parameter-free predictions of embrittlement thresholds in Fe-based steels over a range of H concentrations, mechanical loading rates and H diffusion rates are found to be in excellent agreement with experiments. This work provides a mechanistic, predictive framework for interpreting experiments, designing structural components and guiding the design of embrittlement-resistant materials.

Origin of hydrogen embrittlement in vanadium-based hydrogen separation membranes

Hydrogen embrittlement in metals is a challenging technical issue in the proper use of hydrogen energy. Despite extensive investigations, the underlying mechanism has not been clearly understood. Using atomistic simulations, we focused on the hydrogen embrittlement in vanadium-based hydrogen separation membrane. We found that, contrary to the conventional reasoning for the embrittlement of vanadium, the hydrogen-enhanced localized plasticity (HELP) mechanism is the most promising mechanism. Hydrogen enhances the nucleation of dislocations near the crack tip, which leads to the localized plasticity, and eventually enhances the void nucleation that leads to the failure. Those results provide an insight into the complex atomic scale process of hydrogen embrittlement in vanadium and also help us design a new alloy for hydrogen separation membranes.