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Abstract: White structure flaking (WSF) as a premature wear failure mode in steel rolling element bearings is caused by white etching cracks (WECs) that form in the 1mm zone beneath the contact surface. Hydrogen diffusion into raceways and transient operating conditions have been suggested as drivers of WSF. The initiation and propagation mechanisms for WEC formation are not well understood. This study elucidates WEC initiation processes in hydrogen charged 100Cr6 bearing steel by carrying out two-roller RCF testing. The application of serial sectioning enabled mapping and modelling of entire independent WECs and revealed critical information about initiators. The application of FIB tomography verified initiation mechanisms. The results show strong evidence for subsurface initiation of WECs from inclusions. [Copyright &y& Elsevier]

The transition to a fossil-free energy matrix may require large quantities of hydrogen gas, which could be stored efficiently in underground lined rock caverns (LRCs). Since the consequences of failure can be catastrophic, the LRC design needs to have a small failure probability. However, the current deterministic design practice for LRCs limits the possibility to stringently address geotechnical uncertainties. In this paper, a reliability-based design tool is presented for LRCs. The adaptive directional importance sampling (ADIS) method, which requires a relatively small number of samples, is used with a 3D finite element (FE) model to evaluate small probabilities of failure. An illustrative example based on the LRC in Skallen, southwestern Sweden, demonstrates the implementation and applicability of the developed design tool. The considered uncertainties are related to the geological conditions and the steel lining. The results show that the reliability of this LRC design meets the expected safety requirements. Considering different geological conditions with correlations, at least "good" quality rock mass is needed for the LRC design. An additional sensitivity analysis is performed to study the potential influence of corrosion and hydrogen embrittlement, showing that the LRC design could meet safety requirements for a lower category of the weld quality. [ABSTRACT FROM AUTHOR]

This paper presents the results of an analysis of resistance to hydrogen embrittlement and offers solutions and technologies for manufacturing castings of components for critical applications, such as blades for gas turbine engines (GTEs). The values of the technological parameters for directional crystallization (DC) are determined, allowing the production of castings with a regular dendritic structure of the crystallization front in the range of 10 to 12 mm/min and a temperature gradient at the crystallization front in the range of 165–175 °C/cm. The technological process of making GTE blades has been improved by using a scheme for obtaining disposable models of complex profile castings with the use of 3D printing for the manufacture of ceramic molds. The ceramic mold is obtained through an environmentally friendly technology using water-based binders. Short-term tensile testing of the samples in gaseous hydrogen revealed high hydrogen resistance of the CM-88 alloy produced by directed crystallization technology: the relative elongation in hydrogen at a pressure of 30 MPa increased from 2% for the commercial alloy to 8% for the experimental single-crystal alloy. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this paper is to assess the hydrogen embrittlement sensitivity of carbon gradient heterostructure materials and to verify the reliability of the scratch method. Design/methodology/approach: The surface-modified layer of 18CrNiMo7-6 alloy steel was delaminated to study its hydrogen embrittlement characteristics via hydrogen permeation, electrochemical hydrogen charging and scratch experiments. Findings: The results showed that the diffusion coefficients of hydrogen in the surface and matrix layers are 3.28 × 10−7 and 16.67 × 10−7 cm2/s, respectively. The diffusible-hydrogen concentration of the material increases with increasing hydrogen-charging current density. For a given hydrogen-charging current density, the diffusible-hydrogen concentration gradually decreases with increasing depth in the surface-modified layer. Fracture toughness decreases with increasing diffusible-hydrogen concentration, so the susceptibility to hydrogen embrittlement decreases with increasing depth in the surface-modified layer. Originality/value: The reliability of the scratch method in evaluating the fracture toughness of the surface-modified layer material is verified. An empirical formula is given for fracture toughness as a function of diffused-hydrogen concentration. [ABSTRACT FROM AUTHOR]

Hydrogen embrittlement (HE) remains a pressing issue in materials science and engineering, given its significant impact on the structural integrity of metals and alloys. This exhaustive review aims to thoroughly examine HE, covering a range of aspects that collectively enhance our understanding of this intricate phenomenon. It proceeds to investigate the varied effects of hydrogen on metals, illustrating its ability to profoundly alter mechanical properties, thereby increasing vulnerability to fractures and failures. A crucial section of the review delves into how different metals and their alloys exhibit unique responses to hydrogen exposure, shedding light on their distinct behaviors. This knowledge is essential for customizing materials to specific applications and ensuring structural dependability. Additionally, the paper explores a diverse array of models and classifications of HE, offering a structured framework for comprehending its complexities. These models play a crucial role in forecasting, preventing, and mitigating HE across various domains, ranging from industrial settings to critical infrastructure. [ABSTRACT FROM AUTHOR]

High-pressure proton exchange membrane (PEM) water electrolysis for hydrogen production is a crucial method to achieve low energy consumption, high efficiency, minimal pollution, and seamless integration with storage systems. Despite its potential, the current application of high-pressure PEM water electrolysis faces several challenges. This paper provides a concise analysis of the research advancements in high-pressure PEM water electrolysis for hydrogen production, focusing on technical bottlenecks within high-pressure devices. It explores key issues such as gas cross-permeability, membrane degradation, membrane shedding, and hydrogen embrittlement encountered during high-pressure PEM water electrolysis for hydrogen production. Furthermore, this paper summarizes the latest research directions and proposed solutions based on existing findings, aiming to offer effective references for enhancing the safety, scalability, and industrial application of high-pressure PEM water electrolysis technology. [Display omitted] • State-of-art technology of high-pressure PEMWE for hydrogen production was discussed. • Gas cross-permeability, membrane degradation and hydrogen embrittlement of PEMWE were analyzed. • The latest research directions and proposed solutions for the PEMWE were presented. [ABSTRACT FROM AUTHOR]

Hydrogen can degrade the mechanical properties of steel components, which is commonly referred to as "hydrogen embrittlement" (HE). Quantifying the effect of HE on the structural integrity of components and structures remains challenging. The authors investigated an X70 pipeline steel through uncharged and hydrogen-charged (notched) tensile tests. This paper presents a combination of experimental results and numerical simulations using a micro-mechanics-inspired damage model. Four specimen geometries and three hydrogen concentrations (including uncharged) were targeted, which allowed for the construction of a fracture locus that depended on the stress triaxiality and hydrogen concentration. The multi-physical finite element model includes hydrogen diffusion and damage on the basis of the complete Gurson model. Hydrogen-Assisted degradation was implemented through an acceleration of the void nucleation process, as supported by experimental observations. The damage parameters were determined through inverse analysis, and the numerical results were in good agreement with the experimental data. The presented model couples micro-mechanical with macro-mechanical results and makes it possible to evaluate the damage evolution during hydrogen-charged mechanical tests. In particular, the well-known ductility loss due to hydrogen was captured well in the form of embrittlement indices for the different geometries and hydrogen concentrations. The limitations of the damage model regarding the stress state are discussed in this paper. [ABSTRACT FROM AUTHOR]

Existing natural gas pipelines provide an economic alternative for the transport of hydrogen (H2) in an envisioned hydrogen economy. Hydrogen can dissolve in the steel and cause hydrogen embrittlement (HE), compromising pipeline structural integrity. HE causes subcritical cracking, decreases ductility and fracture toughness, and increases the fatigue crack growth rate (FCGR). This work analyzes the testing standards in gaseous hydrogen used to quantify those effects. Design code ASME B31.12 applicable to hydrogen pipelines has more stringent requirements than ASME B31.8 code commonly used for constructing natural gas pipelines. Differences in materials requirements specified by those codes are summarized. ASME B31.12 pipeline code applies for H2 at a concentration greater than 10% molar. However, recent testing programs acknowledge that H2 degrades steel mechanical properties regardless of its percentage in the blend. This paper discusses how the hydrogen degraded mechanical properties affect pipeline integrity. Decreased mechanical properties cause a drop in the failure pressure of a flawed pipeline, calculated following a fitness for service methodology. There is an increasing risk of subcritical crack growth in H2 as the hardness of base metal and welds increases. This paper analyzes where zones with high hardness and susceptible microstructures are expected in existing pipelines. [ABSTRACT FROM AUTHOR]

With the growing demand for green technologies, hydrogen energy devices, such as Proton Exchange Membrane (PEM) fuel cells and water electrolysers, have received accelerated developments. However, the materials and manufacturing cost of these technologies are still relatively expensive which impedes their widespread commercialization. Additive Manufacturing (AM), commonly termed 3D Printing (3DP), with its advanced capabilities, could be a potential pathway to solve the fabrication challenges of PEM parts. Herein, in this paper, the research studies on the novel AM fabrication methods of PEM components are thoroughly reviewed and analysed. The key performance properties, such as corrosion and hydrogen embrittlement resistance, of the additively manufactured materials in the PEM working environment are discussed to emphasise their reliability for the PEM systems. Additionally, the major challenges and required future developments of AM technologies to unlock their full potential for PEM fabrication are identified. This paper provides insights from the latest research developments on the significance of advanced manufacturing technologies in developing sustainable energy systems to address the global energy challenges and climate change effects. • The AM technologies relevant to PEM fabrication are reviewed. • Corrosion performance of AM materials in the PEM working environment is presented. • The challenges and prospects of AM for PEM fabrication are discussed. • AM has the potential to revolutionize the fabrication of PEM systems. [ABSTRACT FROM AUTHOR]

In this paper, the fatigue crack growth rates of typical pressure vessel material 4130X under different corrosion conditions are investigated, and the effects of corrosion modes and loading frequency on the fatigue crack growth rate of 4130X are discussed. The results show that under the same loading conditions, the pre-corroded crack propagation rate is increased by 1.26 times compared with the uncorroded specimens. The plastic deformation mechanism of the crack tip in air is dominated by phase transformation but the hydrogen introduced by pre-corrosion causes a small number of dislocations at the crack tip. The crack growth rate obtained by corrosion fatigue is four times that of the uncorroded specimen, and the fracture surface shows a strong corrosion effect. The molecular dynamics simulation shows that the hydrogen atoms accumulated at the crack tip make the plastic deformation mechanism dominated by dislocation in the crack propagation process, and the coupling interaction between low frequency and the corrosion environment aggravates the hydrogen embrittlement of the crack tip. In the air condition, the loading frequency has no obvious effect on the crack growth rate: when the frequency decreases from 100 Hz to 0.01 Hz and other conditions remain unchanged, the fatigue crack growth rate increases by 1.5 times. The parameter n in the Paris expression is mainly influenced by frequency. The molecular dynamics simulation shows that low frequency promotes crack tip propagation. [ABSTRACT FROM AUTHOR]

In hydrogen recirculation side channel pumps, the motor rotor is exposed to a high-pressure mixture of steam and hydrogen, which makes hydrogen embrittlement occur in permanent magnets (PMs). A protective coating is necessary for the PMs in high-pressure hydrogen. However, in the process of sleeve interference installation, the protective coating of the PMs is easily damaged. This paper proposes two surface-mounted insert permanent magnet (SIPM) synchronous motor topologies, SIPM1 and SIPM2, in which the retaining sleeves can be eliminated and the PM protective coating is safe in the assembling process. A dovetail PM and rotor core structure is used to protect the PM with higher rotor strength without retaining the sleeve. The electromagnetic performance of the motors with different rotors, including airgap flux density, output torque, torque ripple, and energy efficiency is compared and optimized. It is concluded that the output torque of the SIPM motor can be promoted by 22.4% and torque ripple can be reduced by 2.9%, while the PM volume remains the same as that of the conventional SPM motor. At the same time, the SIPM motor can have lower harmonic contents of back electromotive force (EMF) and rotor loss compared to the SPM motor with a retaining sleeve. Furthermore, the stress of the PM is analyzed under conditions of PM glue action and failure. The proposed SIPM2 has the ability to operate safely at high-speed and high-temperature operating conditions when the PM glue fails. [ABSTRACT FROM AUTHOR]

Austenitic stainless steels (γ-SS) play an important role in the storage of high-pressure hydrogen. However, hydrogen embrittlement (HE) can significantly degrade the mechanical properties of γ-SS. Measuring the distribution of hydrogen in γ-SS is a vital way to learn about HE. In this paper, scanning Kelvin probe force microscopy (SKPFM) and thermal desorption spectroscopy (TDS) have been utilized to analyze the distribution and diffusion of hydrogen in pre-strained SUS316L. Additionally, the McNabb–Foster model is employed to calculate hydrogen in the lattice and phase boundaries along the sample's thickness direction. The results demonstrate that the combination of SKPFM and TDS is an effective approach for studying hydrogen distribution and diffusion in metals. It was observed that hydrogen segregation occurs at the boundary between the martensitic (α′) and austenite (γ) phases. The inhibitory effect of the oxide film on hydrogen diffusion is more significant at lower temperatures. However, it should be noted that the McNabb–Foster model exhibits relatively high accuracy in predicting hydrogen desorption at higher temperatures while disregarding the influence of the native oxide film. [ABSTRACT FROM AUTHOR]

Conventional-sized specimens have been well and widely applied in research on hydrogen embrittlement. However, when the limited-size core components (nozzles and valves, etc.) of hydrogen energy equipment are evaluated for service damage, traditional testing with conventional-sized samples is no longer applicable and micro-sample testing methods are required. In this paper, recent progress in the characterization of hydrogen embrittlement achieved via a small-sized sample tensile test, small punch test and nanoindentation test is reviewed. The commonly used geometries and dimensions of various small-sized specimens are first described and the in situ hydrogen-containing environment testing cases equipped with small-sized specimens are presented, proving the advantages of direct observations of hydrogen influences on the mechanical property and microstructure evolution. Then, the quantitative analysis of hydrogen embrittlement sensitivity involving a small punch test is discussed, with a focus on the comparisons of the hydrogen embrittlement index calculated using different definition methods. Finally, the nanoindentation test of investigation on the interaction between hydrogen and dislocation in metals and the effect of indentation strain rate are summarized. Furthermore, the specific research directions and applications of micro-size specimens for further investigation on hydrogen embrittlement are identified. [ABSTRACT FROM AUTHOR]

This paper studies the hydrogen-assisted microdamage (HAMD) in fully-pearlitic steel. A detailed analysis is provided of the HAMD region in axisymmetric round-notched samples of high-strength eutectoid pearlitic steel under hydrogen embrittlement environmental conditions. The microscopic appearance and evolution of the hydrogen affected region is analyzed from the initiation (sub-critical) to the fracture (critical) situations. The use of very distinct notched samples and their associated stress distributions in the vicinity of the notch tip allows for a study of the key role of the triaxial stress state on hydrogen diffusion and micro-cracking (or micro-damage). The microscopic appearance of the hydrogen-affected zone (the so-called tearing topography surface) resembles micro-damage, micro-cracking or micro-tearing at a micro- or nano-scale due to hydrogen degradation, thus affecting the notch tensile strength and producing hydrogen embrittlement. A micromechanical model is proposed to explain these hydrogen effects on the material on the basis of the lamellar micro- and nano-structure of the pearlitic steel. [ABSTRACT FROM AUTHOR]

In this paper, we present concurrent atomistic-continuum (CAC) simulations of the hydrogen (H) diffusion along a grain boundary (GB), nearby which a large population of dislocations are piled up, in a plastically deformed bi-crystalline bcc iron sample. With the microscale dislocation slip and the atomic structure evolution at the GB being simultaneously retained, our main findings are: (i) the accumulation of tens of dislocations near the H-charged GB can induce a local internal stress as high as 3 GPa; (ii) the more dislocations piled up at the GB, the slower the H diffusion ahead of the slip–GB intersection; and (iii) H atoms diffuse fast behind the pileup tip, get trapped within the GB, and diffuse slowly ahead of the pileup tip. The CAC simulation-predicted local H diffusivity, D pileup − tip , and local stresses, σ , are correlated with each other. We then consolidate such correlations into a mechanics model by considering the dislocation pileup as an Eshelby inclusion. These findings will provide researchers with opportunities to: (a) characterize the interplay between plasticity, H diffusion, and crack initiation underlying H-induced cracking (HIC); (b) develop mechanism-based constitutive rules to be used in diffusion–plasticity coupling models for understanding the interplay between mechanical and mass transport in materials at the continuum level; and (c) connect the atomistic deformation physics of polycrystalline materials with their performance in aqueous environments, which is currently difficult to achieve in experiments. [ABSTRACT FROM AUTHOR]

Hydrogen diffuses in the material and accumulates in dislocations, holes, etc. which will lead to deterioration of the mechanical properties of the material and affect the health state of the structural parts of hydrogen service. In this paper, a characterisation method for the degradation degree of hydrogen-induced properties of materials based on eddy current response signal is proposed. Based on the semi-infinite planar source diffusion model and hydrogen permeation model, an improved hydrogen diffusion and distribution analysis model was established, and an early hydrogen damage eddy current detection model for multilayer conductive structure materials was constructed. The evolution of material properties under the action of hydrogen was analysed, and a linear relationship between hydrogen content and conductivity was obtained. The loss of elongation was selected as the damage index and the relationship between the eddy current response signal and hydrogen embrittlement performance index is established. Experiments verify that the eddy current response signal is sensitive to the performance index and increases with the intensification of hydrogen-induced performance degradation. [ABSTRACT FROM AUTHOR]

Purpose: High-strength martensitic steels having strong hydrogen embrittlement (HE) susceptibility and the metal carbide (MC) nanoprecipitates of microalloying elements such as Nb, V, Ti and Mo in the steel matrix can effectively improve the HE resistance of steels. This paper aims to review the effect of MC nanoprecipitates on the HE resistance of high-strength martensitic steels. Design/methodology/approach: In this paper, the effects of MC nanoprecipitates on the HE resistance of high-strength martensitic steels are systematically described in terms of the types of MC nanoprecipitates, the influencing factors, along with numerical simulations. Findings: The MC nanoprecipitates, which are fine and semicoherent with the matrix, effectively improve the HE resistance of steel through the hydrogen trapping effects and microstructure optimization, but its effect on the HE resistance of steel is controlled by its size, number and distribution state. Originality/value: This paper summarizes the effects and mechanisms of MC nanoprecipitates on HE performance of high-strength martensitic steel and provides the theoretical basis for corrosion engineers to design high-strength martensitic steels with excellent HE resistance and improve production processes. [ABSTRACT FROM AUTHOR]

This document is a guest editorial for a virtual special issue titled "Structural Integrity in the Context of Carbon Neutrality." The issue focuses on the importance of structural integrity in achieving carbon neutrality and features twelve papers that highlight breakthroughs in structural integrity research related to carbon neutrality. The papers cover topics such as suppressing hydrogen embrittlement, improving the reliability of conventional energy conversion systems, understanding fatigue failure mechanisms in gas turbine engines, investigating material properties and damage mechanisms, studying crack growth behavior, and enhancing the fatigue life of welded joints. The authors express their gratitude to the session chairs, reviewers, and authors for their contributions to the special issue. [Extracted from the article]

This paper discusses the effect of reversed austenite (RA) on hydrogen embrittlement (HE) behavior of a high-strength multi-alloyed steel. Three heat treated samples were fabricated by quenching-lamellarization-tempering (QLT) treatment with varying the features of RA. The experimental results revealed that the existence of reversed austenite could reduce the effective diffusion coefficient and HE susceptibility. QLT specimens exhibited the optimization of the strength and HE resistance with 6.7% filmy and stable reversed austenite, which could hinder the hydrogen diffusion, reduce local hydrogen concentration, delay the crack initiation and further arrest the crack propagation. Moreover, a 23% reduction in hydrogen embrittlement susceptibility of QLT specimens was achieved by comparing with quenching-tempering (QT)specimens. However, the interface of RA and matrix was a preferred site for crack initiation. • The role of "lamellarization" on the hydrogen embrittlement was investigated. • Both fraction and stability of revered austenite affected the HE behavior. • The interface of revered austenite and matrix is a preferred site for crack initiation. • The role of RA on the crack propagation was discussed. [ABSTRACT FROM AUTHOR]

The service performance of hot stamped ultra-high strength steel after die punching was evaluated in this paper through typical experiments, including tensile tests, bending tests, and hydrogen embrittlement tests, as well as characterization analysis. The tested samples were prepared through a specially designed tool by considering different die clearances, punch corner radii, and punch shapes. The results showed that the tensile properties are closely related with the selected punching parameters, while the bending properties and hydrogen embrittlement susceptibility are less sensitive to parameters. Furthermore, the laser cutting method was also involved to produce holes on hot stamped parts and compared with the punching samples. It was found that the laser cutting samples performed better in terms of tensile properties and hydrogen embrittlement susceptibility, which were due to the effects of annealing treatment during laser cutting that decreases the material hardness and brings compressive residual stress near the cutting surface, while the bending properties are insensitive to different drilling methods. [ABSTRACT FROM AUTHOR]

Hydrogen embrittlement is a common failure phenomenon observed in metallic materials, leading to cracking or fracturing when subjected to stress or load. The study of hydrogen embrittlement holds significant importance as it enhances our understanding of the properties and behavior of metallic materials. In this paper, we conducted molecular dynamics simulations (MD) to assess the mechanical properties of FeCr alloys, with varying numbers of embedded hydrogen atoms, under tensile conditions. By analyzing the simulation results, we delve into the microscopic mechanism through which hydrogen induces embrittlement damage in the material. Our findings demonstrate that the mechanical properties of alloys decline with an increase in hydrogen atoms. Under stressful conditions, hydrogen atoms inside the crystal exhibit varying degrees of embrittlement. As strain intensifies, dislocations tend to manifest at the aggregates of hydrogen atoms, resulting in cavity formation, increased porosity, and ultimately brittle fracture. [ABSTRACT FROM AUTHOR]

X80 steel is extensively used in hydrogen environments and is susceptible to hydrogen embrittlement (HE). This paper studied the hydrogen-induced cracking (HIC) behavior in the coarse-grained heat-affected zone (CGHAZ) of X80 steel welds, through applying in situ hydrogen-charging tensile experiments, hydrogen permeation experiments, and various surface analysis techniques. It is shown that a few hydrogen atoms can significantly decrease a material's elongation and reduction of area. When the heat input (HI) was 29.2 kJ/cm, the material had minor sensitivity to hydrogen embrittlement. The tensile fractures were ductile without hydrogen. However, the fracture surface exhibited brittle fracture with hydrogen. With increased HI, the HE fracture showed a transition of intergranular fracture→intergranular and transgranular mixed fracture→transgranular fracture. In the presence of hydrogen, the grain boundaries of elongated strips were prone to the formation of intergranular cracks under a tension load, and the hydrogen embrittlement resistance of the bulk lath bainite (LB) was weak. The hydrogen embrittlement susceptibility of pure granular bainite (GB) was lower. Fine LB and GB composite structures could remarkably inhibit intergranular cracks, giving the steel a superior resistance to hydrogen embrittlement. [ABSTRACT FROM AUTHOR]

Cold drawing is a commonly used technique for manufacturing the prestressing steel wires used as structural elements in prestressed concrete structures. As a result of this manufacturing process, a non-uniform plastic strain and residual stress states are generated in the wire. These stress and strain fields play a relevant role as the main cause of the in-service failure of prestressing steel wires in the presence of an aggressive environment, hydrogen embrittlement (HE). In this paper, hydrogen susceptibility to HE is compared in two different commercial cold-drawn wires with the same dimensions at the beginning and at the end of manufacturing that follow different straining paths. To achieve this goal, numerical simulation with the finite element (FE) method is carried out for two different industrial cold-drawing chains. Later, the HE susceptibility of both prestressing steel wires was estimated in terms of the hydrogen accumulation given by FE numerical simulations of hydrogen diffusion assisted by stress and strain states, considering the previously obtained residual stress and plastic strain fields generated after each wire-drawing process. According to the obtained results, the hardening history modifies the residual stress and strain states in the wires, affecting their behavior in hydrogen environments. [ABSTRACT FROM AUTHOR]

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Hydrogen-assisted cracking is one of the most dominant failure modes in metal hydrogen-facing materials. Therefore, the hydrogen-assisted cracking mechanism has been a hot topic for a long time. To date, there is very little published research on numerical methods to describe hydrogen-assisted cracking. This paper presents a new method for the description of hydrogen embrittlement crack growth: an explicit phase-field formulation, which is based on the phase-field description of cracks, Fick's mass diffusion law, and the relationship between hydrogen content and fracture surface energy. A novel computational framework is then developed using the self-developed FEM software DYNA-WD. We numerically calculate several typical conditions in the 3-D coordinates to validate the effectiveness of the proposed computational framework. Specifically, we discuss (i) the failure of a square plate in a hydrogenous environment, (ii) the CT specimen failed with the inner hydrogen, (iii) the plate/failed with the corrosives, and (iv) the failure of the disk test. Finally, the relationship between Mises stress, the concentration of hydrogen, the thickness of the disc, and the loading rate is investigated. [ABSTRACT FROM AUTHOR]

With the progressive expansion of hydrogen fuel demand, hydrogen pipelines, hydrogen storage cylinders and hydrogen refuelling stations (HRSs) are the primary components of hydrogen energy systems that face high-pressure hydrogen environments. Hydrogen embrittlement (HE) is a typical phenomenon in metallic materials, particularly in the high-pressure hydrogen environment, that causes loss of ductility and potentially catastrophic failure. HE is associated with materials, the service environment and stress. The primary mechanisms for explaining the HE of materials are hydrogen-enhanced decohesion, hydrogen-induced phase transformation, hydrogen-enhanced local plasticity, adsorption-induced dislocation emission and hydrogen-enhanced strain-induced vacancy. To reduce the risk of HE for metallic structural materials used in hydrogen energy systems, it is crucial to reasonably select hydrogen-resistant materials for high-pressure hydrogen environments. This paper summarizes HE phenomena, mechanisms and current problems for the metallic structural materials of hydrogen energy systems. A research perspective is also proposed, mainly focusing on metal structural materials for hydrogen pipelines, hydrogen storage cylinders and hydrogen compressors in HRSs from an application perspective. [ABSTRACT FROM AUTHOR]

In this paper, the effects of the skin pass technique on the residual stress and plastic strain fields generated in cold drawn pearlitic steel wires are analyzed. The aim is to find out the optimal conditions to be used in the design of a manufacturing process for obtaining more reliable structural components in terms of the main cause of failure: the hydrogen embrittlement (HE). To achieve this goal, diverse numerical simulations were performed by using finite elements (FE) and considering, on one hand, the first step of a real cold drawing chain, using (i) a conventional drawing die and (ii) modified drawing dies with different soft diameter reductions, and, on the other hand, numerical simulations by FE of the hydrogen diffusion assisted by stress and strain states to estimate the hydrogen distributions. Obtained results revealed the secondary reduction degree as a key parameter in the die design for reducing the drawing-induced residual stress. According to the results, low values of the reduction ratio cause radial distributions of residual stress with significant reductions at both the wire core and at the wire surface. In addition, the hydrogen accumulation at the prospective damage zone (near the wire surface) given by FE simulations is lower in the wires drawn with modified drawing dies including a skin pass zone. [ABSTRACT FROM AUTHOR]

There have been several reviews and numerous papers on hydrogen-embrittlement phenomena and mechanisms in the past few years, but long-standing controversies regarding mechanisms of embrittlement (when hydride phases are not involved) are no closer to being resolved despite all the recent research. These controversies have arisen partly because there have been significant misunderstandings of some of the proposed mechanisms, and some misinterpretation of experimental observations. There has also been a lack of consideration of all the evidence, with some researchers ignoring observations that do not fit their favoured hypothesis. Some recent reviews and papers illustrating the above points are discussed in the present paper, although a comprehensive coverage is not attempted. It is concluded that the adsorption-induced dislocation-emission/void-coalescence mechanism predominates for cleavage-like and intergranular fracture modes that exhibit microscale or nanoscale dimples. Hydrogen-enhanced decohesion, hydrogen-enhanced localised plasticity, and vacancy-based mechanisms may play secondary roles for such fracture modes and could be more important in other cases. [ABSTRACT FROM AUTHOR]

Understanding the impact of hydrogen embrittlement (HE) on the mechanical properties of additively manufactured (AM) metals is of utmost importance for industries utilizing these materials, including critical hydrogen transportation and storage applications. This comprehensive review paper explores the effects of HE on AM alloys, emphasizing the crucial role of microstructure and its influence on HE and hydrogen-induced crack initiation (HICI) and propagation processes. Recent studies indicate that the HE in AM metals may deviate from that observed in conventionally manufactured (CM) metals. The unique characteristics of AM processes may introduce additional factors that affect the complex hydrogen-materials interactions and HE. The hydrogen accumulation at phase interfaces and local reaching of the critical hydrogen concentration represents the primary reason for HICI in AM metals. The specific microstructure of AM and interfaces between phases in the microstructure present crucial factors that influence the HE of AM metals. The interface between phases, which serves as a material structure discontinuity and a location for misfit energy within the structure, can play a critical role in the drop of the HE resistance of certain materials (e.g., martensite/austenite interface in stainless steels, ferrite/perlite interface in low carbon steels, α/β interface in titanium alloys, γ ′ / γ ″ interface in nickel-based alloys, etc.). Titanium and nickel alloys demonstrate comparable microstructural features concerning HE due to the laminar phase structure that develops during heat treatment and the secondary phase allotropy in both metals. However, stainless steels, such as SS316 and SS304, follow a distinct mechanism where austenite to martensite transformation predominantly governs hydrogen embrittlement. It is noteworthy that the effect of hydrogen embrittlement in additively manufactured metals seems to be less pronounced compared to CM metals. A comprehensive investigation of HE mechanisms and their interaction with microstructure according to the HELP + HEDE model can provide valuable insights into the susceptibility of AM metals to HE and HICI. This review underscores the need for continued investigation to ensure the reliable performance of AM metal components exposed to hydrogen and HE in various industrial applications. Also, it provides an in-depth understanding of hydrogen embrittlement in AM metals, providing recommendations for the design, development, and safety introduction of new additively manufactured alloys in hydrogen-based energy solutions. Finally, a perspective on future necessary experiments for exploring the influence of porosity in AM metals on HE, hydrogen-induced crack initiation, and other hydrogen damage mechanisms, including its interaction with microstructure, is given. [Display omitted] • Viewing hydrogen embrittlement (HE)'s impact on mechanical properties in additive manufacturing features its key roles. • Emphasizing the complexity of HE in AM alloys, urging ongoing investigations in hydrogen-rich environments. • Examining AM metals reveals varying HE behavior by alloy (e.g., titanium, nickel superalloys, austenitic stainless steel). • Assessing the microstructure's crucial role in quantifying HE in AM metals. • Exploring innovative solutions for HE in AM alloys in hydrogen-rich environments (e.g., aerospace). [ABSTRACT FROM AUTHOR]

This review paper introduces a research project that seeks to quantify oxygen inhibition of gaseous hydrogen embrittlement with possible application for gas transmission pipelines transporting hydrogen. And it summarizes the compelling laboratory evidence that oxygen may inhibit gaseous hydrogen embrittlement. Quantification of oxygen inhibition of gaseous hydrogen embrittlement is needed to allow evaluation of this approach to the inhibition of hydrogen embrittlement in gas transmission pipelines. The experimental approach is explained as the quantification of the amount of hydrogen entering the steel from gas mixtures containing hydrogen using a purpose-built gas phase permeation cell. [ABSTRACT FROM AUTHOR]

The main cause of in-service failure of cold drawn wires in aggressive environments is hydrogen embrittlement (HE). The non-uniform plastic strains and residual stresses generated after cold drawing play a significant role in the matter of HE susceptibility of prestressing steels. In this paper, a new and innovative design of the drawing scheme is developed, geared towards the reduction in both manufacturing-induced residual stresses and plastic strains. To achieve this goal, three innovative cold drawing chains (consisting in diverse multi-step dies where multiple diameter reductions are progressively carried out in a single die) are numerically simulated by the finite element (FE) method. From the residual stress and plastic strain fields revealed from FE numerical simulations, hydrogen accumulation for diverse times of exposure is obtained by means of FE simulations of the hydrogen diffusion assisted by stress and strains. Thus, an estimation of the HE susceptibility of the cold drawn wires after each process was obtained. Results reveal that cold drawn wire using multi-step dies exhibits lower stress and strain states nearby the wire surface. This reduction causes a decrease in the hydrogen concentration at the prospective damage zones, thereby improving the performance of the prestressing steel wires in hydrogenating environments promoting HE. Thus, the optimal wire drawing process design is carried out using special dies with several reductions per die. [ABSTRACT FROM AUTHOR]

Round-notched samples are commonly used for testing the susceptibility to hydrogen embrittlement (HE) of metallic materials. Hydrogen diffusion is influenced by the stress and strain states generated during testing. This state causes hydrogen-assisted micro-damage leading to failure that is due to HE. In this study, it is assumed that hydrogen diffusion can be controlled by modifying such residual stress and strain fields. Thus, the selection of the notch geometry to be used in the experiments becomes a key task. In this paper, different HE behaviors are analyzed in terms of the stress and strain fields obtained under diverse loading conditions (un-preloaded and preloaded causing residual stress and strains) in different notch geometries (shallow notches and deep notches). To achieve this goal, two uncoupled finite element (FE) simulations were carried out: (i) a simulation by FE of the loading sequences applied in the notched geometries for revealing the stress and strain states and (ii) a simulation of hydrogen diffusion assisted by stress and strain, for estimating the hydrogen distributions. According to results, hydrogen accumulation in shallow notches is heavily localized close to the wire surface, whereas for deep notches, hydrogen is more uniformly distributed. The residual stress and plastic strains generated by the applied preload localize maximum hydrogen concentration at deeper points than un-preloaded cases. As results, four different scenarios are established for estimating "a la carte" the HE susceptibility of pearlitic steels just combining two notch depths and the residual stress and strain caused by a preload. [ABSTRACT FROM AUTHOR]

During a routine start-up exercise of a standby service water pump, a threaded coupling that joined sections of a 41.5 ft (12.7 m) long pump shaft experienced fracture. The pump was taken out of service and examined to determine the cause of fracture. It was apparent early in the examination that the fracture involved hydrogen stress cracking. However, the nature of the corrosive attack suggested an interaction between the threaded coupling and biological organisms living in the freshwater environment of the pump shaft. The organisms had colonized on the coupling, changing the local environment and creating conditions favorable to hydrogen stress cracking. This paper describes the analysis of the fracture of the coupling and provides an example of how biologically induced corrosion can result in unexpected fracture of a relatively basic machine part. [ABSTRACT FROM AUTHOR]

With the background of emission peaks and carbon neutrality, light weight has become an irreversible trend in the development of the automobile industry. It is an inevitable choice to use a large amount of ultra-high-strength steels to realize light weight and safety of automobiles. Ultra-high-strength martensitic steels can be divided into hot-formed steels and cold-formed steels according to the forming process. In recent years, ultra-high-strength martensitic steels have been rapidly developed in automotive battery pack frameworks, door guard beams, bumpers, A-pillars, etc., depending on their good plasticity and advanced forming technology. In this paper, the recent progress of ultra-high-strength martensitic steels for automobiles is systematically reviewed, the mechanisms of alloying, strengthening, and toughening are emphatically expounded, and the hydrogen embrittlement problems in application are summarized. Finally, the prospects of manufacture and application of ultra-high-strength martensitic steels for automobiles in the future are forecasted. [ABSTRACT FROM AUTHOR]

This document is a summary of the 6th International conference on environmentally-assisted cracking (EAC) held in Reston, Washington, DC, USA, from July 16-21, 2023. The conference aimed to bring together researchers in materials, chemistry, and mechanics to develop a better understanding of EAC. The papers published in this special issue of corrosion reviews reflect the conference's focus on EAC in higher temperature environments and the use of experimental and modeling approaches. The document also highlights the need for future studies on the initiation and early stages of EAC, with a particular emphasis on the use of experimental and modeling methods. The organizers express their gratitude to the referees and the Editorial Board of Corrosion Reviews for their assistance. [Extracted from the article]

Purpose: This paper aims to make clear the sensitive zone of subsea pipeline to stress corrosion cracking (SCC) under a disbonded coating. Design/methodology/approach: The change of microenvironment under a disbonded coating in artificial seawater was analyzed by using a rectangular crevice cell. The SCC behavior of subsea pipeline was studied by slow strain rate tensile tests. Findings: The microenvironment at the crevice bottom exhibits obvious acidification, Cl- aggregation and cathodic protection potential (CP) rise. Accordingly, the susceptibility of X70 steels to SCC is high due to the intensive anodic dissolution effect. At the opening, hydrogen atom can access into the steel and induce hydrogen embrittlement effect on account of the applied over-protected CP potential, resulting in a relatively high susceptibility to SCC. The corrosiveness of the microenvironment at crevice middle, however, is mild with proper CP potential; thus, the susceptibility of X70 steel to SCC here is lower than that obtained at the opening and the crevice bottom. Originality/value: A rectangular crevice cell is built to survey the microenvironment evolution under a disbonded coating in situ. The sensitive zone of subsea pipeline to SCC under a disbonded coating is clarified. [ABSTRACT FROM AUTHOR]

In the paper, experimental studies of the hydrogen and pre-strained effect on fracture resistance of steam generator steel 22K were carried out. Special cylindrical samples were loaded up to fracture under a uniaxial tensile test with different pre-strained degrees and hydrogen charged times of the material. Stress-strain curves «Si–ei» were plotted. The true strain «ei» in the local volume was determined using the method of optical-digital image correlation (ODIC). The results showed that the hydrogen influence is practically absent in the elastic area of strain. The fracture energy of steel 22K decreases under the hydrogen influence and pre-strain in all investigated cases. It is shown that during six months of air exposure, with the 0% pre-strained samples release almost all hydrogen. In pre-strained samples, the hydrogen concentration decreased by 1–3% compared to the initial values. This indicates that they have trapped hydrogen that cannot escape on its own. Hydrogen embrittlement (HE) indexes for 0% pre-strained samples at different levels of hydrogen-charging calculated by the strain and energy approaches are equal to each other. There is a difference in the values of the HE index depending on the hydrogen-charge time for pre-strained samples. This indicates that both strain and strength characteristics of the material, which are integrally taken into account in the energy approach, are sensitive to HE. [ABSTRACT FROM AUTHOR]

Transportation and portable applications already use hydrogen as fuel, but it is essential to use highly-efficient hydrogen storage methods to increase its usage in the future. The compressed form is the most utilized for transportation applications, but mechanical compressors have low efficiency when compressing low quantities of gas to high pressure. The most suitable device for hydrogen compression is the Electrochemical Hydrogen Compressor (EHC). It has the same structure as a Proton Exchange Membrane Fuel Cell (PEM-FC), but it works at very high-pressure (700 bar). The present work analyses the monopolar plate of an Electrochemical Hydrogen Compressor prone to hydrogen embrittlement. Irregular shape variations generate peaks of stress magnitude and triaxiality, further contributing to decreasing metal ductility at the local scale. The calculation of the stress field in such components is essential due to the possibility of failure due to the material embrittlement caused by hydrogen. The paper presents a conceptual design of an EHC operating at 700 bar and focuses on the shape and the mechanical stress of the end-plates to have conservative levels of the nominal stress states, which then are taken as the design parameter for providing adequate structural integrity and mechanical reliability to the component. The FEM analysis with Marc software—of MSC Software Corporation—identified the optimal end-plates configuration in circular plan view and active area. The plate, sized to have a deflection no greater than 0.1 m m when the EHC works at 700 bar , should have the minimum thickness of 17 m m. [ABSTRACT FROM AUTHOR]

Hydrogen transportation by pipelines gradually becomes a critical engineering route in the worldwide adaptation of hydrogen as a form of clean energy. However, due to the hydrogen embrittlement effect, the compatibility of linepipe steels and associated welds with hydrogen is a major concern when designing hydrogen-carrying pipelines. When hydrogen enters the steels, their ductility, fracture resistance, and fatigue properties can be adversely altered. This paper reviews the status of several demonstration projects for natural gas-hydrogen blending and pure hydrogen transportation, the pipeline materials used and their operating parameters. This paper also compares the current standards of materials specifications for hydrogen pipeline systems from different parts of the world. The hydrogen compatibility and tolerance of varying grades of linepipe steels and the relevant testing methods for assessing the compatibility are then discussed, and the conservatism or the inadequacies of the test conditions of the current standards are pointed out for future improvement. [Display omitted] • Summarized projects of pure-hydrogen and natural gas-hydrogen blending pipelines. • Discussed the factors affecting hydrogen compatibility of pipeline. • Reviewed the testing methods for assessing hydrogen-steel compatibility. • Presented a new proposal for toughness test for pipeline slow loading condition. • Several challenges facing the high-pressure hydrogen pipelines are outlined. [ABSTRACT FROM AUTHOR]

Pipelines have been installed and operated around the globe to transport oil and gas for decades. They are considered to be an effective, economic and safe means of transportation. The major concern in their operation is corrosion. Among the different forms of corrosion, stress corrosion cracking (SCC), which is caused by stresses induced by internal fluid flow or other external forces during the pipeline's operation, in combined action with the presence of a corrosive medium, can lead to pipeline failure. In this paper, an extensive review of different factors affecting SCC of pipeline steels in various environmental conditions is carried out to understand their impact. Several factors such as temperature, presence of oxidizers (O2, CO2, H2S, etc.), composition and concentration of medium, pH, applied stress, and microstructure of the metal/alloy have been established to affect the SCC of pipeline steels. SCC susceptibility of a steel at a particular temperature strongly depends on the type and composition of the corrosive medium and microstructure. It was observed that pipeline steels with water quenched and quenched and tempered heat treatments, such as those that consist of acicular ferrite or bainitic ferrite grains, are more susceptible to SCC irrespective of solution type and composition. Applied stress, stress concentration and fluctuating stress facilitates SCC initiation and propagation. In general, the mechanisms for crack initiation and propagation in near-neutral solutions are anodic dissolution and hydrogen embrittlement. [ABSTRACT FROM AUTHOR]

This paper attempts to give a broad overview on technologies progress status, effects, perspectives, and issues associated to H 2 NG widespread applications. It deepens and completes the content of previous reviews by including hitherto unreviewed aspects as far as possible. To do so, a holistic approach has been used by surveying technical, energy, environmental, economic and safety issues related to the hydrogen mixtures' use. This review aims to provide support for a broader understanding of the problem, starting from the simple list of mixtures properties up to their impact on both NG pipelines and end-use devices. Hydrogen injection affects several blend characteristics and gas network parameters. Mixing limits are also related to Wobbe index variations and safety aspects due to the flashback risk. Numerous works have shown that hydrogen fractions of 10% allow parameters to be kept within acceptable ranges, and up to 20% are not related to significant risks. • Review of studies on hydrogen-enriched natural gas blends. • Power-to-Gas concept and motivation for hydrogen injection into the gas grid. • Effects of hydrogen in gas pipelines and hydrogen embrittlement issues. • Analysis of effects on end use devices and discussion of safety issues. • Economics aspects and price of hydrogen-methane blends. [ABSTRACT FROM AUTHOR]

As a promising candidate for accident-tolerant fuel (ATF) cladding materials, FeCrAl alloys are susceptible to hydrogen embrittlement (HE) under high-temperature radioactive water environments. Understanding the HE mechanism of FeCrAl is crucial, and studying H 2 dissociative adsorption can provide valuable insights since it is the first step in the HE processes. In this paper, we investigated the H 2 dissociative adsorption on Fe (110) and FeCrAl (110) surfaces using first-principles calculations based on Density Functional Theory (DFT). Our results indicate that the decomposition of H 2 molecules on FeCrAl (110) surfaces is significantly affected by surface elemental effects compared to Fe (110) surfaces. Specifically, Al atoms weaken both the H 2 decomposition and the H binding strength of Al-containing sites. Cr atoms decrease the decomposition tendency of H 2 in certain configurations, but Cr aggregation enhances the binding strength of H atoms on Cr-containing sites. The mechanism underlying the Al/Cr weakening effects on H 2 decomposition is due to the charge deficiency through alloying. Our findings have generalized implications for studying the interactions between iron-based alloys and hydrogen in various applications such as hydrogen storage, transportation, and prevention. • The strength of H 2 –Fe/Cr/Al interactions follow the order: H 2 –Al < H 2 –Cr < H 2 –Fe. • Al atoms have strong weakening effect on H 2 dissociation compared to Fe. • Cr atoms have slight weakening effect on H 2 dissociation compared to Fe. • The Cr aggregation can enhance H 2 –Cr interaction & H binding strength. • The weakening effects of Al & Cr on H 2 dissociation are caused by the charge deficit of Al & Cr after alloying with Fe. [ABSTRACT FROM AUTHOR]

In this work, the failure characteristics of a die-casting die manufactured from conventional hot-worked steel (SKD61) were investigated experimentally. A die with heat-checking failure on its cavity due to high-pressure die casting was employed. Apparently, the microstructural characteristics of the die around the regions exhibiting heat checking were unaltered. However, the hardness values decreased slightly because of the die heating via the injection of molten aluminum alloy, which is the tempering-like effect. Hydrogen was detected in the die around the regions with heat checking, which can slightly reduce the tensile fracture strain, i.e., hydrogen embrittlement (HE). The extent of HE was sensitive to the loading speed, particularly to a low loading speed. When heated to 450 °C, hydrogen gas was detected in a commercial die lubricant, which may lead to hydrogen infiltration in the die. This paper discusses the details pertaining to hydrogen penetration and die failure mechanisms. [ABSTRACT FROM AUTHOR]

The paper presents the research results on assessment of in-service degradation of the 0.17 C-Mn-Si steel of gas transit pipeline operated for 36 years. High degradation degree of the operated steel was manifested in a significant decrease in plasticity characteristics, impact toughness and resistance to stress corrosion cracking and hydrogen embrittlement compared to the as-delivered steel. The tests carried out using the low stress method revealed significant changes in elastic hysteresis, elasticity modulus and relative residual deformation of the steel depending on its state (as-delivered and post-operated ones), demonstrated to be highly sensitive to assess in-service degradation degree of pipeline steels. [ABSTRACT FROM AUTHOR]

This study presents a modeling of spatial and size distributions of precipitates in diffusion-controlled phase transitions in metals. These data are essential for estimating the probability of critical cluster formation, leading to brittle fracture. The practical significance of the current research includes demonstrated ability to estimate the probability of zirconium hydrogen embrittlement based on obtained stochastic characteristics of δ-hydrides (ZrH1.6) morphology. The model includes a statistical analysis of serial calculations based on classical heterogeneous nucleation and growth of plate-shaped inclusions in 3D domain. The approach was verified with experimental data in modeling of θ'-phase (Al2Cu) nucleation and growth in Al–4 wt % Cu alloy. Also the paper includes an appendix with an analytical approach for evaluating the distribution function of inclusions in cluster length and mean projection length, which is the morphology metric correlating with mechanical properties. This analytical solution was also used for the verification of the numerical model. [ABSTRACT FROM AUTHOR]

Blending hydrogen in existing natural gas pipelines compromises steel integrity because it increases fatigue crack growth, promotes subcritical cracking and decreases fracture toughness. In this regard, several laboratories reported that the fracture toughness measured in a hydrogen containing gaseous atmosphere, KIH, can be 50% or less than KIC, the fracture toughness measured in air. From a pipeline integrity perspective, fracture mechanics predicts that injecting hydrogen in a natural gas pipeline decreases the failure pressure and the size of the critical flaw at a given pressure level. For a pipeline with a given flaw size, as shown in this work, the effect of Hydrogen Embrittlement (HE) in the predicted failure pressure is largest when a failure occurs by a brittle fracture. The HE effect on failure pressure diminishes with a decreasing crack size or increasing fracture toughness. The safety margin after a successful hydrostatic test is reduced and therefore the time between hydrotests should be decreased. In this work, all those effects were quantified using a crack assessment methodology (level 2, API 579-ASME FFS) considering literature values for KIH and KIC reported for an API 5L X52 pipeline steel. To characterize different scenarios, various crack sizes were assumed, including a small crack with a size close to the detection limit of current in-line inspection techniques and a larger crack that represents the largest crack size that could survive a hydrotest to 100% of the steel Specified Minimum Yield Strength (SMYS). The implications of a smaller failure pressure and smaller critical crack size on pipeline integrity are discussed in this paper. [ABSTRACT FROM AUTHOR]

This paper investigated the effects of welding and alternating wet-dry seawater on the hydrogen embrittlement (HE) susceptibility of a new nanoparticle-reinforced high-strength steel, dispersion-strengthened-high-strength (DSHS) steel. The results show that welding led to the transformation of granular bainite to tempered martensite. It also promotes grain coarsening as well as an increase in inclusions size and irregular changes in shape. This results in increased susceptibility to HE at the welded joint (WJ). After wet-dry cycle corrosion in seawater, corrosion products impede the oxygen transfer and promote the hydrogen evolution reaction, so the hydrogen production increases. The decrease in the protection of corrosion products at the WJ and the decrease in NbC content led to an increase in hydrogen production but a decrease in hydrogen trapping capacity. Therefore, the WJ HE sensitivity of DSHS steel is further increased. • The effect of welding and alternating wet-dry environment on the HE of DSHS steels was studied. • Simulation of hydrogen permeation under alternating wet-dry environment using a modified Devanathan-Stachurski cell. • The microstructure and inclusions are the main factors affecting the HE of the material in its initial state. • Hydrogen production is the main factor for the susceptibility of DSHS steels to HE under alternating wet-dry environment. [ABSTRACT FROM AUTHOR]

Some key structural parts made of welding titanium alloys usually serve in hydrogen environment in aerospace, ship building and chemical industries. To investigate the hydrogen embrittlement (HE) behaviors of the welded titanium alloy joints and the impact factors, the TC4 titanium alloy joints welded by laser welding method were first treated by ultrasonic surface rolling process (USRP). Then, slow-rate tensile tests were conducted under electrochemical hydrogen charging condition to compare the mechanical properties of the TC4 laser welded joints before and after USRP. On this basis, the HE behaviors and mechanisms of the USRP-treated TC4 laser welded joint and the USRP-untreated one were discussed in detail. The results show that USRP could significantly improve the anti-hydrogen embrittlement behaviors of the TC4 laser welded joint, which could be attributed to the grain refinement and residual compressive stress in the deformation layer induced by USRP. The results of this paper provide a theoretical basis for the design of anti-hydrogen embrittlement metal materials. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this paper is to find a new method to evaluate the hydrogen embrittlement performance of heterogeneous materials and thin film materials. Design/methodology/approach: The changes of hydrogen embrittlement properties of steel were studied by electrochemical hydrogen charging test and scratch test. The microstructure and properties of the alloy were analyzed by hardness tester, scanning electron microscope and three-dimensional morphology. The fracture toughness before and after hydrogen charging was calculated based on the scratch method. Findings: The results showed that the hydrogen-induced hardening phenomenon occurs in the material after hydrogen charging. The scratch depth and width increased after hydrogen charging. The fracture toughness obtained by the scratch method showed that hydrogen reduces the fracture toughness of the material. The comparison error of fracture toughness calculated by indentation method was less than 5%. Originality/value: The results show that the scratch method can evaluate the hydrogen embrittlement performance of the material. This method provides a possibility to evaluate the hydrogen embrittlement of thin-film and heterogeneous materials. [ABSTRACT FROM AUTHOR]