Hydrogen Trapping Research Articles

Synergic effects of temperature and pressure on the hydrogen diffusion and dissolution behaviour of X80 pipeline steel

Gas-phase hydrogen permeation experiments were conducted on X80 steel at temperatures from −15℃ to 60℃ and hydrogen pressures of 1, 4, 8 MPa. Hydrogen trap densities were determined, and a method for calculating nonlinear hydrogen concentration distribution was established and verified. Results reveal different temperature dependencies for hydrogen concentrations at varying pressures. At 4 and 8 MPa, the hydrogen concentration increases with temperature, whereas at 1 MPa, it initially decreases before increasing. Additionally, the influences of hydrogen pressure, hydrogen trap binding energy, and hydrogen trap density on this trend are discussed.

Effect of tempering temperature on mechanical properties and hydrogen embrittlement resistance of a dual-precipitation-hardened martensitic steel

ABSTRACT The effects of dual-precipitation on the mechanical properties and hydrogen embrittlement (HE) resistance of a Ti-Mo-alloyed martensitic steel were investigated using a quenching and tempering (QT) procedure. The precipitate-free QT200 sample exhibited high tensile strength and brittle fracture after hydrogen charging. In contrast, the QT300 sample demonstrated a dual-precipitation constitution of (Ti, Mo)C and ϵ-carbide, achieving a high yield strength (∼1400 MPa) without sacrificing tensile ductility (∼10%). More importantly, it showed higher resistance to HE (elongation loss: ∼4.2%) compared to the low-strength QT400 sample. The unusual HE susceptibility of the QT300 samples can be attributed to a higher hydrogen trapping ability of ϵ-carbide compared to (Ti, Mo)C precipitates. This results in high densities of irreversible hydrogen trapping sites and a completely ductile fracture mode characterised by numerous dimples.

Surrogate model-based assessment of particle damage behaviour of Al[sbnd]Zn[sbnd]Mg alloy

Recent research has found some intermetallic compound particles with even stronger hydrogen trapping capacity (e.g., Al7Cu2Fe) than the age-hardening precipitates that are reported to be the origin of hydrogen embrittlement in aluminium. Such intermetallic compound particles can reduce hydrogen concentration at the interface between the precipitates and aluminium by absorbing hydrogen in their interiors, thus preventing the hydrogen embrittlement of aluminium. However, this cannot be achieved if the particles, which have absorbed large amounts of hydrogen, are damaged due to hydrogen embrittlement. In this study, the hydrogen embrittlement of aluminium was observed in situ by X-ray CT, and the damage behaviour was analysed of all the particles that were located in the gauge section of a single tensile specimen. After exhaustive quantification of the size, shape, and spatial distribution of the particles, coarsening processes identified highly correlated design variables. Subsequently, particle damage behaviour was analysed utilizing a surrogate model using a support vector machine. The damage to Al7Cu2Fe particles could be described only by design variables representing size and shape, while those representing spatial distribution were removed through the coarsening processes. No change was observed in the damage behaviour of Al7Cu2Fe particles with increasing hydrogen concentrations, and it was concluded that the dispersion of Al7Cu2Fe particles is effective in preventing hydrogen embrittlement of aluminium. The contribution of damaged particles to the formation of fracture surfaces and the damage behaviour of Mg2Si particles, where damage is accelerated by hydrogen, were also analysed.

Premature Damage in Bearing Steel in Relation with Residual Stresses and Hydrogen Trapping

In this study, premature damage in cylindrical roller bearings made of 100Cr6 (SAE 52100) was investigated. For this purpose, full bearing tests were carried out using two different lubricant formulations with similar viscosities. Published research has pointed out the occurrence of tribo-chemical reactions that cause lubricant degradation and the release of hydrogen in tribo-contact. Hydrogen content measurements were conducted on tested samples, and these measurements showed dependence on the lubricant formulations. Hydrogen diffusion and trapping were identified as significant factors influencing premature damage. The measurement of trapping energies was conducted by thermal desorption spectroscopy, whereas residual stresses, which influence hydrogen diffusion and accumulation, were measured using X-ray diffraction. The measured trapping energies indicated that rolling contact caused the creation and release of hydrogen traps. Over-rolling resulted in changes in residual stress profiles in the materials, demonstrated by changes in stress gradients. These can be directly linked to subsurface hydrogen accumulation. Hence, it was possible to determine that the location of the microstructural damage (WEC) was correlated with the residual stress profiles and the subsurface von Mises stress peaks.

An insight into hydrogen and carbon dioxide displacement and trapping efficiencies in carbonate formations through NMR and core flooding

The complex pore structure of carbonates can influence gas storage process to different extents, depending on stored gas type. Hence, investigating gas displacement and residual trapping in such formations is crucial. Here, several CO2 and H2 core flooding experiments were performed using three carbonate samples. The drainage process is followed by brine imbibition to test gas residual trapping. Additionally, nuclear magnetic resonance (NMR) T2 spectra measurements were conducted at different stages. The results show that H2 had less displacement efficiency in carbonates compared to CO2. The pore structure has a noticeable impact on CO2 displacement efficiency. However, H2 displacement efficiency is less sensitive to rock properties. The NMR-T2 measurements show that CO2 partially saturated medium-sized pores and almost filled all macropores during drainage. After imbibition, large pores are slightly re-saturated with brine with varying degrees compared to their initial brine saturations. H2 shows lower residual trapping efficiency compared to CO2.

Hydrogen trapping and embrittlement in a second-generation Ni-based single crystal superalloy

This study explores the hydrogen trapping capability and hydrogen embrittlement (HE) of a second-generation single crystal (SX) superalloy. Embrittlement susceptibility is greater as the duration of hydrogen charging is extended. The presence of hydrogen induces cleavage, micro-crack formation and denser slip traces. Moreover, hydrogen facilitates the formation of nano-voids and the activation of high-density dislocations, leading to denser slip bands which serve as initiation sites for micro-cracks. In addition, the desorption activation energy of hydrogen trapped at dislocations and soluble in the γ matrix is 33.7 kJ/mol, and hydrogen trapped at the γ/γ′ interface and vacancies is 42.4 kJ/mol. First-principles calculations have indicated that hydrogen reduces the binding strength at the γ/γ′ interface, which promotes the propagation of micro-cracks.

Nano hydride precipitation-induced disappearance of yield drop in zirconium alloy at elevated temperature

Hydrogen-induced variations in mechanical behavior of zirconium alloys impose detrimental influence on nuclear fuel cladding integrity. This work reports a disappearance of intrinsic yield drop in a recrystallized zirconium alloy following hydrogen-charging treatment. Microstructure characterizations reveal that the nano-hydrides precipitation, mediated by second phase particles Zr(Fe,Cr)2 acting as hydrogen trapping sites, leads to emission of substantial dislocations in α-matrix grains due to strong strain concentrations, as identified by high-angular resolution EBSD. These mobile dislocations preserved at elevated temperatures can maintain the applied plastic strain and impede rapid dislocation multiplication as well, a conclusion validated by comparative analysis of dislocation densities prior to and near yielding stage. These findings are expected to shed light on the underlying mechanisms governing the interaction between hydrogen and microstructural defects in Zr-based nuclear fuel cladding materials.

Microstructural Dependence of the Impact Toughness of TP316H Stainless Steel Exposed to Thermal Aging and Room-Temperature Electrolytic Hydrogenation.

This work deals with the effects of two individual isothermal aging experiments (450 °C/5000 h and 700 °C/2500 h) and the subsequent room-temperature electrolytic hydrogen charging of TP316H stainless steel on its Charpy V-notch (CVN) impact toughness and fracture behavior at room temperature. Microstructural analyses revealed that aging at 700 °C resulted in the abundant precipitation of intermediary phases, namely, the Cr23C6-based carbide phase and Fe2Mo-based Laves phase, whereas aging at 450 °C resulted in much less pronounced precipitation of mostly intergranular Cr23C6-based carbides. The matrix phase of 700 °C-aged material was completely formed of austenitic solid solution with a face-centered cubic (FCC) crystal structure, whereas an additional formation of ferritic phase with a base-centered cubic (BCC) structure was detected in 450 °C-aged material. The performed microstructure observations correlated well with the obtained values of CVN impact toughness, i.e., a sharp drop in the impact toughness was observed in the material aged at 700 °C, whereas negligible property changes were observed in the material aged at 450 °C. The initial, solution-annealed (precipitation-free) TP316H material exhibited a notable hydrogen toughening effect after hydrogen charging, which has been attributed to the hydrogen-enhanced twinning-induced plasticity (TWIP) deformation mechanism of the austenitic solid solution. In contrast, both aging expositions resulted in significantly lowered hydrogen embrittlement resistance, which was likely caused by hydrogen trapping effects at the precipitate/matrix interfaces in thermally aged materials, leading to a reduced TWIP effect in the austenitic phase.

Influence of hydrogen uptake on additive manufacturing and conventional austenitic stainless steels 316L

This study investigates the hydrogen embrittlement resistance of 316L stainless steels fabricated via conventional manufacturing (CM) and directed energy deposition (DED) additive manufacturing (AM). The hydrogen effect on the mechanical properties of these samples has been examined through a combination of microstructural investigation correlated with hydrogen solubility and trapping. Results show the CM sample has a lower solubility of hydrogen with a relatively low dislocation density. In the case of the as-built AM sample, the higher amount of hydrogen is linked with a deterioration in the mechanical behaviours of the steel (strength/elongation) and a higher hydrogen embrittlement sensitivity. This deterioration can be attributed to the higher misorientation density in AM material with a larger grain size. Conventionally, global hydrogen concentration is measured from thermal desorption spectroscopy (TDS), however this study presents a new measurement using glow discharge optical emission spectroscopy (GDOES). This method provides a new insightful understanding of hydrogen embrittlement with local hydrogen distribution and a comparison for existing standards.

First-Principles study of hydrogen solubility and embrittlement of Cr23C6 in nickel-based alloys

This research examines the crucial role played by Cr23C6 carbides in hydrogen trapping and their subsequent impact on the mechanical properties of the material. The hydrogen solution energies at different defect sites within the bulk phase of Cr23C6 and the Ni/Cr23C6 interface were analyzed using first-principles computations. This study underscores the notable vulnerability of nickel-based alloys to hydrogen embrittlement as the carbide content increases. Substantial hydrogen enrichment at the Ni/Cr23C6 interface, particularly at octahedral interstitial sites on the Ni side and C vacancies at the interface, was identified through comprehensive atomistic simulations. This enrichment negatively affects separation at the interface, indicating an increased risk of brittle fracture in the presence of hydrogen. By providing insights into the microscopic processes involved, our results seek to contribute to the development of nickel-based alloys that are more resistant to hydrogen, thereby influencing material selection and treatment in industrial applications prone to hydrogen embrittlement.

Multi-scale structural heterogeneity promoting hydrogen embrittlement in additively manufactured pure nickel

In this study, how physical differences in the microstructure of additively manufactured (AM) pure Ni affect its susceptibility to hydrogen embrittlement (HE) are investigated. The presence of high-density dislocation cells (DCs) and grain boundaries in AM Ni could absorb more hydrogen therein, with the DC boundaries serving as reversible hydrogen trapping sites. The DC boundaries overlapped with the grain boundaries might lead to an enhanced hydrogen diffusion therein for AM Ni. Consequently, an increased depth of hydrogen-affected region and accelerated failure process were observed in AM Ni during tensile testing due to intergranular cracking. Furthermore, the HE resistance can be slightly improved by a dislocation-cell elimination heat treatment for AM Ni-800, but it remains lower than that of traditionally manufactured Ni, primarily due to the residue of bi-modal grains with small grains along the molten pool boundaries. The underlying HE mechanism based on the structural heterogeneities at different scales for pure Ni is discussed.

Multi-scale approach to hydrogen susceptibility based on pipe-forming deformation history

Hydrogen-induced-cracking initiates without external loading due to residual stresses. Pipe manufacturing process composed of crimping, U-ing, O-ing, and expansion has a major impact on local hydrogen concentration, as strain pattern evolves from one forming step to another, causing residual stresses that serve as driving force for hydrogen diffusion. The novelty of the presented work lies in the development of a multi-scale approach that links the residual stresses from the macroscopic pipe-forming process with locally dissolved hydrogen atoms in microstructure under the consideration of microstructural heterogeneities to identify areas susceptible to hydrogen-induced-cracking. First, a 3d-pipe-forming-model was built. Second, representative volume elements with lattice defects were generated to analyze hydrogen trapping in microstructure. Third, representative volume elements were placed in the pipe via sub-modeling, so that local loading history of the pipe was assigned to microstructure models. At the end of the pipe-forming process, representative volume elements were loaded with hydrogen on the surface and final hydrogen concentration was simulated based on residual stresses, considering microstructural effects such as grain size/shape, crystallographic texture and hydrogen traps, e.g. dislocations, voids and inclusions. On meso-/macroscale, a combined isotropic–kinematic hardening material model was implemented, while on microscale, a phenomenological crystal-plasticity-hydrogen-diffusion model was coded. According to the multi-scale simulations under the consideration of microstructural effects the bottom center position in the pipe was detected to be critical to hydrogen-induced-cracking as the maximum local hydrogen concentration was predicted at that location. Based on the loading history hydrogen-induced-cracking susceptibility increases from voids to hard and soft non-metallic inclusions.

Influence of hydrogen ingress and capture on the mechanical properties of spray formed 2195 aluminum alloy

The current research has focused on the hydrogen capturing and its impact on the mechanical properties of spray-formed 2195 (SF2195) aluminum alloy. Microstructure characterization, thermal desorption spectra (TDS) and hydrogen trapping of characteristic microstructure, are used to investigate the generation, migration and trapping of hydrogen. The retention of moisture in the carrier gas is believed to induce high concentration of hydrogen and the amorphous Al2O3 layer within the SF2195 billet, and the local retention of carrier gas brings about pores with the Al2O3 layer on the inner wall. High concentration of hydrogen is captured in the hot-rolled alloy while around 60 % of the hydrogen can be eliminated during the solution-quenching. Particles of T1 phase trap large quantity of hydrogen and the high-density dislocations developed from the pre-stretch promote the migration of hydrogen towards dispersoids and precipitates. The presence of hydrogen and Al2O3 layer contributes to the reduced plasticity of SF2195 alloy. The spreading of flattened pores can induce intensified hydrogen damage effect in local regions and thus contribute to the unusually decreased ductility along the thickness direction in the T8 aged alloy.

Effect of hydrogen on the microstructural evolution and local mechanical properties of 430 ferritic stainless steel at high-temperature conditions

The present study investigated the impact of hydrogen on the microstructural evolution and mechanical properties of 430 ferritic stainless steel at high-temperature conditions. Hydrogen trap sites were analyzed at high temperatures using thermal desorption spectrometry through high-temperature hydrogen atmosphere charging and electrolytic hydrogen charging. The microstructural evolution was characterized using scanning electron microscopy and electron backscatter diffraction. The nanoindentation technique was employed to analyze the local mechanical properties of ferrite matrix, grain boundaries, and M23C6/matrix interfaces. Hydrogen trap sites in 430 ferritic stainless steel included ferrite crystal lattice, grain boundaries, intragranular dislocations, and M23C6/matrix interfaces where hydrogen could not intrude at room temperature. At high temperatures, hydrogen caused a decrease in grain size. Furthermore, at high temperatures, hydrogen altered the crystal orientation and texture of the ferrite matrix. There was an increase in the number of ferrite grains with (001) and (101) orientation increase and the formation of a new α-fiber texture. Hydrogen inhibited the triggering of the slip system in body centered cubic crystal lattice and induced an increase in dislocation density and internal stress. While hydrogen at high temperatures had a minimal impact on the matrix strength limit, it reduced the strength limit of the near grain boundaries and (Fe, Cr)23C6 precipitates. The influence of hydrogen on the microstructural evolution and mechanical properties of 430 ferritic stainless steel could be elucidated by the mechanisms of hydrogen enhanced decohesion, hydrogen-enhanced localized plasticity, and hydrogen enhanced specific crystal plane rotation suggested in the present study.

Resolving Hydrogen Trapping Sites in Steels at Ultra-High Resolution Using Cryogenic Atom Probe Tomography

Resolving Hydrogen Trapping Sites in Steels at Ultra-High Resolution Using Cryogenic Atom Probe Tomography

Influences of (Al, Ca, Si, Nb, Mn)-oxy-sulfide inclusions on corrosion degradation for newly designed 17–4 martensitic PH steel in simulated geothermal environments

Influences of (Al, Ca, Si, Nb, Mn)-oxy-sulfide inclusions on hydrogen trapping and stress corrosion cracking in a newly designed 17–4 martensitic PH steel were carried out under simulated geothermal environments based on experiments and calculations. The results indicate that CaS and MnS in inclusions are not only prone to preferential dissolution, but also more likely to become hydrogen trapping sites at the interface with matrix than other components. The number of pits rapidly increase before the sample fracture at 159.25 h, while cracks around external pits and internal gourd-like cavities are probably attributed to the uneven expansion of inclusion-triggered pits.

Computer simulations on the microscopic mechanisms for the nucleation of hydrogen bubbles in aluminum

Trapping of multiple hydrogen (H) atoms inside vacancies in aluminum (Al) is related to the formation of H bubbles, which ultimately results in embrittlement of the material. However, the formation mechanisms of H bubbles are still not well known. In this work, we perform systematical ab initio simulations to study the trapping of H atoms inside vacancies, and its influence on the growth of vacancies. It is found that monovacancy can trap as many as 8 H atoms, forming Vac1H8. H atoms prefer the off-center positions close to tetrahedral sites in vacancy. The shortest H–H bond length in vacancy is 2.10 Å among H atoms, which suggests that it is impossible to form H2 molecule in monovacancy. The accumulation of H atoms reduces the vacancy formation energy closest to Vac1Hm, promoting the formation of new vacancy. The newly produced vacancy can bind tightly with Vac1Hm and form Vac2Hm. With the similar way, the continuous formation of new vacancies and aggregation of H atoms may ultimately result in growth of VacnHm and formation of superabundant vacancies and H bubbles in Al.

Roles of lattice and grain boundary on hydrogen diffusion and trap behaviors in single-and poly-crystalline CrCoNi medium-entropy alloy

In this study, single-crystalline and poly-crystalline CrCoNi alloys are utilized as model systems to analyze the distinct roles of each GB and interstitial lattice sites. To effectively reveal hydrogen behavior, both electrochemical and gaseous hydrogen pre-charging methods are applied. Hydrogen content, diffusivity, and trap behaviors are quantified using thermal desorption analysis and hydrogen permeation tests, which determines (1) changes in hydrogen behavior depending on the presence of GB and (2) alterations in hydrogen behavior depending on lattice crystallographic orientation. The results indicate that GB and interstitial lattice sites exhibit comparable binding energies for hydrogen trapping. However, the introduction of GB alters the primary trapping sites from interstitial lattice sites to GB. In this case, the hydrogen content in the poly-crystalline alloy is determined by the trap site density of the primary trapping site. On the other hand, in the single-crystalline alloy, where only interstitial lattice sites exist, the crystallographic orientation of the hydrogen-charged plane is an important variable that determines hydrogen content and hydrogen diffusivity. Such insights contribute to a deeper understanding of hydrogen behavior within a more intricate microstructure, suggesting the alloy design approach to enhance resistance to HE.

Effects of pre-strain on hydrogen-induced stress corrosion cracking behavior of Q345R steel in hydrofluoric acid vapor environment

This study investigates microstructure, hydrogen diffusion properties, and stress corrosion cracking (SCC) behavior of Q345R steel subject to pre-applied strains of 1%, 3%, and 5%. The relationship between microstructure and SCC susceptibility in hydrofluoric acid (HF) vapor is examined. It is found that pre-strain cannot change the microstructure of Q345R steel but increases dislocation density. The increasing SCC sensitivity of Q345R steel in HF vapor is associated with the dislocation density induced by pre-strain. With increasing pre-strain, dislocation density and reversible hydrogen trap increase, and interaction between hydrogen and dislocation accelerates hydrogen-induced SCC. In addition, irreversible hydrogen traps caused by high pre-strain can severely aggravate hydrogen-induced SCC, resulting in high SCC vulnerability.

Modelling neutron damage effects on tritium transport in tungsten

A damage-induced hydrogen trap creation model is proposed, and parameters for tungsten are identified using experimental data. The methodology for obtaining these parameters using thermo-desorption analysis spectra data is outlined. Self-damaged and optionally annealed tungsten samples have undergone TDS analysis, which has been analysed to identify the properties of extrinsic traps induced by the damage and to determine how they evolve with damage and annealing temperature. A parametric study investigated the impact of the damage rate and temperature on tritium inventories in tungsten. Tritium transport simulations have been performed with FESTIM considering a 1D model of a 2 mm sample of tungsten with damage rates and temperatures varying from 0– 102 dpa/fpy and 600–1300 K, respectively. The results show that after 24 h simultaneous exposure to neutron damage at 102 dpa/FPY and tritium implantation at 700 K, tritium inventories can increase by up to four orders of magnitude when damaged at a rate of 102 dpa/FPY compared to undamaged, defect-free tungsten, increasing further to five orders of magnitude after one full power year. The time taken to reach retention saturation shows the need for kinetic models of trapping properties on time scales relevant to reactor operation. The trap-creation model parameterisation procedure can be used to investigate neutron damage effects on other fusion-relevant materials such as EUROFER, Inconel and more.