Hydrogen Trapping Behavior Research Articles

Comparative study of non-metallic inclusions on the critical size for HIC initiation and its influence on hydrogen trapping

In the present work, the critical crack nucleation size and the hydrogen trapping capability of inclusion were discussed with a numerical simulation considering the factors of inclusion/matrix heterojunction. The results showed that the inclusion composition had a significant effect on hydrogen capacity and its critical nucleation size of hydrogen-induced cracking (HIC). The MnS inclusions exhibited a larger critical size tolerance of HIC nucleation (approximately 2.5 μm), but for some typical oxide inclusions, it ranged between 0.1 and 0.4 μm. In addition, two sheets of steel containing different composition, morphology, and distribution of inclusions were studied by the standard-based test and thermal desorption spectroscopy (TDS) to evaluate the HIC susceptibility and hydrogen trapping behaviour. The results complementarily demonstrated that when controlling the non-metallic inclusions into the proper size and compound with MnS into the sphere, the HIC resistance of steel could be efficiently improved.

Microstructural based hydrogen diffusion and trapping models applied to Fe–C[sbnd]X alloys

Hydrogen embrittlement of modern high strength steels consists of different interacting time-dependent mechanisms. One of these mechanisms is hydrogen diffusion and trapping to accumulate hydrogen in critical areas with high mechanical loads. Therefore, understanding hydrogen diffusion and trapping behavior of carbides containing high strength steels is an essential part to effectively increase the hydrogen resistance. For that purpose, a microstructural based model was developed and parametrized to Fe–C–V and Fe–C–Ti alloys. Generalized analytical equations were derived to describe the evolution of different kinds of trap densities with the measured carbide mean radius, annealing temperature or dislocation density. Finally, the models support the idea of hydrogen trapping at carbon vacancies and coherent interface positions. In future, these models are well suited for finite element process simulations of industrial components to predict the local solubility and chemical diffusion as demonstrated in the last section of this work.

Effect of Microstructure on Hydrogen Induced Cracking and Hydrogen Trapping Behavior of X100 Pipeline Steel

Effect of Microstructure on Hydrogen Induced Cracking and Hydrogen Trapping Behavior of X100 Pipeline Steel

First-principles calculation on the structure stability, hydrogen trapping behaviour, and adhesion properties of the Zr(0001)[sbnd]ZrC(100) interface

The structure stability, hydrogen trapping behaviour, and adhesion properties of the Zr(0001)ZrC(100) interface are investigated by first-principle calculations. Periodically distributed distortion and stress-relaxed regions with lengths of 16.6 Å are formed to relax the lattice mismatch at the Zr(0001)ZrC(100) interface. Homogeneous covalent 3ZrC bonds are formed in the distortion region. The interfacial sinking effect exists only in the interface stress-relaxed region where the interstitial hydrogen has a considerably lower formation energy of −0.61 eV after the zero-point energy correction, than those in the interface distortion region, Zr, and ZrC bulk of 0.95, −0.10, and 1.30 eV, respectively. After the interstitial sites in the interface stress-relaxed region are fully occupied by hydrogen, the interface energy is significantly reduced from 2.34 to 1.52 J/m2. The work of separation Wsep along the interface is approximately 3.78–3.91 J/m2, while the brittle fracture of the Zr(0001)ZrC(100) interface always occurs at the Zr matrix (along the Zr1 layer) with the lowest Wsep of 3.18–2.95 J/m2. Hydrogen-induced electron localisation exists at the interface, which reduces the interface structure stability. In addition, a hydrogen passivation layer forms owing to the formation of ZrH and CH bonds at the interface.

Investigation of hydrogen diffusion and trapping behavior under tensile stresses in a container steel

Abstract Hydrogen embrittlement is the interaction between stress and hydrogen existing in materials or absorbed from environment. Exploring the hydrogen diffusion behavior under action of static tensile stress is necessary to understand the mechanisms of hydrogen embrittlement which happens before yielding. In this work, a new method was utilized to do research on hydrogen diffusion behavior of a container steel through hydrogen permeation tests under three static stress points, which can be realized by combining slow strain rate machine and Devanathan-Stachurski cells. Results demonstrated that with the increasing of static stress within elasticity, the hydrogen diffusion coefficient increases, the density of irreversible traps (M7C3 and Cu-rich particles) decreases, and some of irreversible traps would transform to reversible traps at the same time. Irreversible hydrogen traps have been believed to improve resistance to hydrogen embrittlement, which had been studied here that is not reliable for application of those structural parts bearing stress.

Hydrogen Trapping Behavior in Vanadium Microalloyed TRIP-Assisted Annealed Martensitic Steel

Transformation induced plasticity (TRIP)-assisted annealed martensitic (TAM) steel combines higher tensile strength and elogangtion, and has been increasingly used but appears to bemore prone to hydrogen embrittlement (HE). In this paper, the hydrogen trapping behavior and HE of TRIP-assisted annealed martensitic steels with different vanadium additions had been investigated by means of hydrogen charging and slow strain rate tensile tests (SSRT), microstructral observartion, and thermal desorption mass spectroscope (TDS). Hydrogen charging test results indicates that apparent hydrogen diffusive index Da is 1.94 × 10−7/cm2·s−1 for 0.21wt.% vanadium steel, while the value is 8.05×10−7/cm2·s−1 for V-free steel. SSRT results show that the hydrogen induced ductility loss ID is 76.2% for 0.21wt.%V steel, compared with 86.5% for V-free steel. The trapping mechanism of the steel containing different V contents is analyzed by means of TDS and Transmission electron microscope (TEM) observations. It is found out that the steel containing 0.21wt.%V can create much more traps for hydrogen trapping compared with lower V steel, which is due to vanadium carbide (VC) precipitates acting as traps capturing hydrogen atoms.The relationship between hydrogen diffusion and hydrogentrapping mechanism is discussed in details.

Role of retained austenite in hydrogen trapping and hydrogen-assisted fatigue fracture of high-strength steels

The Interaction of hydrogen with retained austenite under fatigue loading of dual-phase and complex-phase high-strength steels with strength of about 1200 MPa was studied. A load-controlled fatigue test was performed in the air with the maximum applied tensile strength of 900 MPa, which is just below the offset yield point of the studied steels. The trapping of hydrogen accumulated into the studied steels under the fatigue loading was studied by thermal desorption spectroscopy. Measurements of hydrogen trapping evolution and microstructure changes during fatigue testing reveal a complicated hydrogen trapping behavior driven by hydrogen interaction with deformation defects and retained austenite. Hydrogen concentration increases in the studied steels during the fatigue testing in the air without preceding hydrogen charging. The fracture surfaces were studied by scanning electron microscopy evidencing the relationship between the hydrogen concentration increase related to retained austenite and initiation of the intergranular fatigue fracture. The role of retained austenite in hydrogen-assisted fatigue cracking is discussed and a possible mechanism of the hydrogen-assisted fatigue crack initiation in the high-strength steels is proposed.

A mechanistic study on the hydrogen trapping property and the subsequent electrochemical corrosion behavior of quenched and tempered steel

The hydrogen-facilitated anodic dissolution of steel is an interesting experimental phenomenon, but the persistent gaps in this knowledge area are great. The changes in the Tafel slopes and the reaction rates of steel that has been cathodically charged with hydrogen are interpreted mainly in the context of hydrogen trapping and de-trapping behaviors of steel using a variety of electrochemical methods. This study reveals that the increase in the anodic current density and the decrease in the polarization resistance are attributed primarily to the hydrogen-induced lattice expansion. Based on the Tafel-slope change, the oxidation of hydrogen cation partly contributed to the increase in the total anodic current density together with the dominant anodic reaction of the steel dissolution. The electrochemical permeation measurements showed much slower effusion kinetics of the hydrogen that has been trapped at the ε-carbide particles, and the trapping and de-trapping behavior at the fine particles are one of the controlling factors of the hydrogen-enhanced anodic dissolution of steel. From an engineering aspect, it is believed that the current study will provide an important insight into future perspectives on stress corrosion cracking failure occurring in various high-strength steels.

Role of microstructure on electrochemical hydrogen permeation properties in advanced high strength steels

The hydrogen permeation process in steels is closely associated with the microstructure of steels that greatly affect hydrogen trapping and hydrogen diffusion behaviors. In this study, the electrochemical hydrogen permeation experiment using a modified Devanathan-Stachurski (D-S) cells was employed to evaluate the hydrogen permeation properties in advanced high strength steels with four types of microstructures (from single phase, dual phase to complex phase). Results showed that both phase interfaces and retained austenite (RA) could act as the trapping sites for hydrogen and consequently reduced the hydrogen diffusion coefficient in steels. Furthermore, it was suggested that the role of RA on hydrogen trapping behaviors depended on its morphology. Finally, the lattice diffusion coefficient (DL) in each steel was determined and the correlations between the microstructure in steels and hydrogen evolution reaction (HER) kinetics were also investigated.

Hydrogen trapping in alloys studied by thermal desorption spectrometry

Thermal desorption spectrometry (TDS) is a powerful experimental technique used to characterize hydrogen trapping in metals. The passage of hydrogen through a metal is hindered by lattice imperfections, which tend to attract and bind it. The susceptibility of materials to hydrogen embrittlement is directly related to the interaction between traps (defects) and hydrogen. Since trapping affects the metal's diffusivity, it has a major influence on the hydrogen assisted cracking (HAC) phenomenon. Hydrogen trapping is usually evaluated on the basis of reaction controlled mechanisms. Our studies are based on the measurements of temperatures of the gas desorption, the heating rate, and the activating energy. This paper reviews TDS′ applications in quantitative studies of hydrogen trapping and release behavior in crystalline metals. We will discuss both the mechanisms proposed for hydrogen embrittlement in hydride and non-hydride systems and the differences between hydrogen effects on light and heavy metals alloys. In this paper, we compared between duplex Ti–6Al–4V, magnesium (Mg) alloys, and duplex stainless steels (DSS) which can create hydrides in certain conditions. We discuss hydrogen-induced second phases formation, hydrogen's physical trapping, and how these processes affect hydrogen embrittlement in those alloys. In this research, we give another aspect to the trapping mechanism exposed to different hydrogen charging environments by low and high hydrogen fugacity. The main factors controlling the embrittlement phenomenon are the irreversible activation trapping energy, hydrogen fugacity, and second phases' contents. The trapping mechanisms in duplex Ti–6Al–4V, Mg, and DSS and the prediction of failure will be discussed in detail.

Thermal desorption analysis for hydrogen trapping in microalloyed high-strength steels

Hydrogen can have an extreme degradation effects in steels, particularly concerning the mechanical properties. These effects can lead to hydrogen-assisted cracking in microalloyed high-strength steels during fabrication and/or operation in industrial applications. In order to study these effects, electrochemically charged tensile specimens were tested to elucidate the degradation of their properties. The carrier gas hot extraction (CGHE) method, which functionally combines a mass spectrometer with a thermal desorption analysis (TDA) process, was used for the detection of ultra-low diffusible hydrogen concentrations in the material specimens. The mass spectrometer provided rapid and automatic determination of hydrogen concentration, whereas the TDA presented the activation energy within the respective test specimen at the specific temperature. Additionally, specimen temperature was carefully monitored to reduce the evaluation error for local effusion peaks. A quenching and deformation dilatometer was used for the analysis of typical heat-affected zones during the welding process for a high reproducibility of the homogenous microstructures that were studied. The present work shows the interaction between hydrogen and lattice defects in different microalloyed materials and heat-affected zones of weldable fine-grained steels. These steels were prepared in a quenched and tempered condition and in a thermo-mechanically rolled condition. These preparations were made according to German standard DIN EN 10025-6 and to DIN EN 10149-2, respectively. The trapping characteristics of two steel grades, S690QL and S700MC, were studied with respect to the activation energy dependent on carbon content and microalloying elements such as Ti, Nb, Mo, Cr, and V. The two steel grades exhibited several types of traps: carbide formations, dislocations, and/or grain boundaries were common, which can influence activation energy and hydrogen solubility. The type and dimension of inclusions or particles also affected the hydrogen trapping behavior. A decrease of carbon and specific alloying elements in thermo-mechanically hot rolled steels led to a change in the activation energy binding the trapped hydrogen. This thermo-mechanically hot rolled steel revealed an increased interaction between hydrogen and precipitations. The higher carbon content in the quenched and tempered steel led to a higher interaction between hydrogen and iron carbide, specifically in the martensitic phase. Furthermore, the trapping behavior in heat-affected zones showed a significant increase in activation energy, especially in the coarse-grained microstructure. These previously mentioned various effects were studied to better understand the degradation of mechanical properties in these two steels.

Effect of bainite in microstructure on hydrogen diffusion and trapping behavior of ferritic steel used for sour service application

Abstract

Hydrogen trapping in high strength 0Cr16Ni5Mo martensitic stainless steel

Hydrogen trapping behavior has been investigated by means of thermal desorption spectroscopy (TDS) for a high strength steel after it was tempered at the temperatures of 430 °C, 500 °C and 520 °C, respectively. The loss of ductility was characterized by slow strain rate test (SSRT) and microscopic observation. It shows that with hydrogen charging the fracture feature transfers from ductile to brittle, resulting in the loss of ductility. Undeformed microstructure immediately beneath the fracture surface in charged specimen corresponds to badly ductility compared to the obviously streamline plastic deformation in uncharged specimen. The activation energies for the peaks present in the TDS analysis are calculated for all tested steel and the activation energies for all temperature peaks are similar, corresponding to the similar types of hydrogen traps.

STUDY ON HYDROGEN EMBRITTLEMENT SUSCEPTIBILITY OF 1000 MPa GRADE 0Cr16Ni5Mo STEEL

0Cr16Ni5Mo steel is the most popular material used for fasteners and bolts in the marine engineering equipment. With the light weight trend of equipment, the strength grades of the steel become higher. 0Cr16Ni5Mo steel combines high strength, high hardness and high fracture toughness with good ductility. However, high strength steel is prone to degradation by hydrogen, resulting in the loss of its excellent mechanical properties. And the presence of diffusible hydrogen near a notch tip is easily to cause crack propagation. The susceptibility to hydrogen embrittlement of steel is largely determined by the hydrogen diffusivity and the behaviors of hydrogen trapping in the steel. Therefore, the hydrogen trapping behaviors of 1000 MPa grade 0Cr16Ni5Mo steel have been investigated by means of thermal desorption spectroscopy (TDS). Meanwhile, the hydrogen embrittlement susceptibility of the notch and smooth specimens was evaluated by slow strain rate tests (SSRT), and the fracture morphology was also observed. The results showed that the main hydrogen traps of experimental steel was contained dislocations and grain boundaries. The elongation of hydrogen charged specimens was decreased obviously rather than tensile strength. With the increase in hydrogen concentration, the fracture surfaces of hydrogen charged specimens was displayed a transition from ductile microvoid coalescence to a mixed morphology of dimples, quasicleavage and intergranular features. The steel had little irreversible hydrogen due to less C content, and had much susceptibility with reversible hydrogen contained. The model of hydrogen induced stress was calculated on basis of *收到初稿日期: 2015-01-12,收到修改稿日期: 2015-05-16 作者简介:孙永伟,男, 1986年生,博士生 DOI: 10.11900/0412.1961.2015.00033 第1315-1324页 pp.1315-1324

Evaluation of hydrogen trapping mechanisms during performance of different hydrogen fugacity in a lean duplex stainless steel

Hydrogen trapping behavior in a lean duplex stainless steel (LDS) is studied by means of thermal desorption spectrometry (TDS). The susceptibility of a metal to hydrogen embrittlement is directly related to the trap characteristics: source or sink (reversible or irreversible, respectively). Since trapping affects the metal's diffusivity, it has a major influence on the hydrogen assisted cracking (HAC) phenomenon. It is known from previously published works that the susceptibility will depend on the competition between reversible and irreversible traps; meaning a direct relation to the hydrogen's initial state in the steel. In this research the trapping mechanism of LDS, exposed to different hydrogen charging environments, is analyzed by means of TDS. The TDS analysis was supported and confirmed by means of X-ray diffraction (XRD), hydrogen quantitative measurements and microstructural observations. It was found that gaseous charging (which produces lower hydrogen fugacity) creates ∼22% higher activation energy for hydrogen trapping compared with cathodic charging (which produces higher hydrogen fugacity). These results are due to the different effects on the hydrogen behavior in LDS which causes a major difference in the hydrogen contents and different hydrogen assisted phase transitions. The highest activation energy value in the cathodic charged sample was ascribed to the dominant phase transformation of γ → γ∗, whereas in the gaseous charged sample it was ascribed to the dominant formation of intermetallic compound, sigma (σ). The relation between hydrogen distribution in LDS and hydrogen trapping mechanism is discussed in details.

Modelling the influence of austenitisation temperature on hydrogen trapping in Nb containing martensitic steels

Hydrogen trapping behaviour is investigated by means of thermokinetic simulations in a martensitic steel. The heat treatment consists of austenitisation followed by quenching and tempering. The model prescribes a minimum in hydrogen trapping at an austenitisation temperature of 1050 °C. Below this temperature, austenite grain boundaries are the prevailing trap, whereas niobium atoms in solid solution are the main traps above 1050 °C. The model describes precisely the experimental results.

The Role of Cr in H Desorption Kinetics in Rapidly Solidified Al

Hydrogen desorption kinetics for rapidly solidified high purity Al and Al-Cr alloy foils containing 1.0, 1.5 and 3.0 at % Cr were investigated by means of thermal desorption analysis (TDA) at a heating rate of 3.3°C/min. For the first time, it was found that oxide inclusions of Al2O3 are dominant high-temperature hydrogen traps compared with pores and secondary phase precipitates resulted in rapid solidification of Al and its alloys. The correspondent high-temperature evolution rate peak was identified to be positioned at 600°C for high purity Al and shifted to 630°C for Al-Cr alloys. Amount of hydrogen trapped by dislocations increases in the alloys depending on Cr content. Microstructural hydrogen trapping behaviour in low-and intermediate temperature regions observed here was in coincidence with previous data obtained for RS materials using thermal desorption spectroscopy (TDS). The present results on hydrogen thermal desorption evolution indicate that the effect of oxide surface layers becomes remarkable in TDA measurements and show advantages in combinations of both desorption analysis methods to investigate hydrogen desorption kinetics in materials.

Evaluation of the Effect of TiC Precipitates on the Hydrogen Trapping Capacity of Fe-C-Ti Alloys

The present work evaluates the hydrogen trapping behavior of different laboratory cast generic Fe-C-Ti martensitic alloys. Titanium carbides were precipitated in the materials by well-designed heat treatments. A quenched and tempered martensitic matrix with final strength above 1000 MPa was aimed for and verified by means of hardness measurements. Tempering allowed generating precipitates with different characteristics in terms of coherency, size and distribution due to the secondary hardening effect, as was evaluated by transmission electron microscopy. The hydrogen trapping capacity of the TiC precipitates was investigated by thermal desorption spectroscopy, while melt extraction was performed to determine the amount of hydrogen present after cathodic hydrogen charging. Generally, it could be concluded that the incoherent particles in the quenched material were not able to trap hydrogen, whereas the quenched and tempered material trapped hydrogen at the interface of small probably coherent TiC.

Hydrogen trapping in high strength martensitic steel after austenitized at different temperatures

Hydrogen trapping behavior has been investigated by means of thermal desorption spectrometry (TDS) for a high strength steel after it is austenitized at the temperature range of 880–1250 °C, oil quenched, and tempered at 200 °C. Results show that with increasing austenitizing temperature, the pre-charged hydrogen concentration in the steel first decreases and then increases, being the lowest value at the austenitizing temperature of 1050 °C. The variation of hydrogen concentration with austenitizing temperature is related to the differences in the prior austenite grain size and solute Nb content, which may act as shallow hydrogen traps in the steel. The difference in the pre-charged hydrogen concentration can account for the previously reported result on delayed fracture resistance of the steel after austenitized at different temperatures.

Influence of experimental parameters on thermal desorption spectroscopy measurements during evaluation of hydrogen trapping

Thermal desorption spectroscopy (TDS) was performed on two steels, (i) S550MC (an industrial, micro-alloyed high strength low alloy steel), and (ii) C075, a lab cast TiC containing steel. The influence of experimental parameters was studied which were related to hydrogen charging, sample features and the TDS measurement itself. It was found that the experimental conditions can significantly influence the TDS results. The results indicated that all experimental parameters are important in hydrogen related research and a reproducible experimental procedure is important in order to guarantee a reproducible analysis of the hydrogen trapping behavior by means of thermal desorption spectroscopy.