Hydrogen Damage Research Articles

A model for high temperature hydrogen attack in carbon steels under constrained void growth

Petrochemical vessels exposed to high temperature and high pressure hydrogen gas may suffer from high temperature hydrogen attack (HTHA). HTHA is a hydrogen-induced degradation of carbon steels whereby internal hydrogen reacting with carbides forms methane gas bubbles, mainly on grain boundaries (GBs), with an associated loss in strength that can result in premature fracture of structural components. The design of equipment against HTHA is primarily based on the use of the empirical Nelson curves which are phenomenological and do not account for the underlying failure mechanisms and the material microstructure. Starting from the underlying deformation and fracture mechanisms, we present a simple constraint-based model for failure of steels by HTHA which involves growth of GB voids due to coupled diffusion of atoms along the GBs and creep of the matrix surrounding the voids. Since voids form only on some of the GBs, the uncavitated GBs geometrically constrain the growth of voids on the cavitated ones. The model is used to study void growth in HTHA of 21/4Cr–1Mo steel both in the presence and absence of externally applied stress. In the latter case, the model predictions are in good agreement with experimental results. Lastly, the model is used to develop a Nelson-curve type diagram in the presence of external stress in which the curves demarcating the safe/no-safe regimes are functions of the time to failure. This diagram though should be viewed as the result of the application of a new methodology toward devising mechanism-based Nelson curves and not as proposed new Nelson curves for the steel under investigation.

Role of point defects in hydrogen damage at α-Cr2O3/α-Fe2O3 (0001) interface

Point defects at the actual α-Cr2O3/α-Fe2O3 (0001) interface control the passive film's protective properties, and their interaction with hydrogen is a crucial factor, which determines whether possibility of hydrogen damage can be reduced or not. We study the role of point defects in hydrogen damage at α-Cr2O3/α-Fe2O3 (0001) interface using density functional theory. It is found that Cr vacancy and Fe vacancy at the interface trap H with the lowest binding energy −2.908 eV and −2.798 eV, respectively. The solute atoms such as Zn, Ni and Cu at the interface trap H with negative binding energies, in which the minimum binding energy is −1.603 eV for Cu doped interface with H. Alloying elements Al, Ti, V, Mn, Nb and Mo at the interface lead to positive H binding energies, meaning they could not trap H atom. These results confirm that Cr vacancy, Fe vacancy and alloying elements Ni, Cu, and Zn play significant roles in hydrogen damage at the interface of passive films, while alloying elements Mn, Mo, Ti, Nb, Al and V can weaken the possibility of hydrogen damage at the interface of passive films. Our findings provide guiding significance of choosing proper alloying elements to obtain hydrogen damage-resistant steels in industry.

Sulfate‐reducing bacteria‐assisted hydrogen‐induced stress cracking of 2205 duplex stainless steels

AbstractThe paper presents the results of a laboratory investigation of the microbiologically assisted hydrogen‐induced stress cracking (HISC) of 2,205 duplex stainless steel (DSS). The testing of susceptibility toward HISC was performed with two different methods. Precharged in sulfate‐reducing bacteria (SRB), inoculated medium samples were subjected to slow strain‐rate testing in artificial seawater. In situ constant load tests were performed directly in SRB‐inoculated medium under hydrogen charging at 70% of the ultimate tensile strength. Samples tested in the biotic (SRB) conditions showed a considerable loss of ductility as compared to those tested in sterile conditions. Quantitative characteristics of fracture surfaces indicated increased susceptibility to HISC of biotic samples, therefore, suggesting a role of SRB in promoting hydrogen damage of DSS.

Prevention of Hydrogen Damage Using MoS₂ Coating on Iron Surface.

The prevention of hydrogen penetration into steels can effectively protect steels from hydrogen damage. In this study, we investigated the effect of a monolayer MoS2 coating on hydrogen prevention using first-principles calculations. We found that monolayer MoS2 can effectively inhibit the dissociative adsorption of hydrogen molecules on an Fe(111) surface by forming a S–H bond. MoS2 coating acts as an energy barrier, interrupting hydrogen penetration. Furthermore, compared with the H-adsorbed Fe(111) film, the work function of the MoS2-coated film significantly increases under both equilibrium and strained conditions, indicating that the strained Fe(111) film with the MoS2 coating also becomes more corrosion resistant. The results reveal that MoS2 film is an effective coating to prevent hydrogen damage in steels.

Prevent hydrogen damage in α-Cr2O3/α-Fe2O3 (0 0 0 1) interface

By means of first-principles calculations based on the density-functional theory, we investigate the vacancy trappings prevent hydrogen damage in two dimension α-Cr2O3/α-Fe2O3 (0 0 0 1) interface structure. Our calculations show that H atoms prefer to occupy the unoccupied O atoms octahedral interstitial site (Osite) in the center of the interface structure without vacancy defect, weakening the cleavage strength of Fe and O atoms and decreasing the work function and stability of interface structure. To prevent hydrogen damage in this interface structure, we model three Fe, Cr and O vacancy defects in this interface structure, respectively. Fe and Cr vacancy defects with lower H binding energy and higher work function, are better hydrogen trappings compared to O vacancy. These results confirm the Fe and Cr vacancy defects are effective hydrogen trappings to prevent hydrogen damage for passive film of steel, which has significant practical implications.

水素損傷評価 (Part. 7)

水素損傷評価 (Part. 7)

Effect of H on elastic properties of Mg<sub>2</sub>Si by the first principles calculation

The mechanical properties of Al-Mg-Si-type aluminum alloys may degenerate due to the hydrogen damage during servicing in hydrogen environment. The Mg<sub>2</sub>Si is the main strengthening phases in Al-Mg-Si-type aluminum alloys. Therefore, the mechanical properties of Mg<sub>2</sub>Si directly determine the strengths of Al-Mg-Si-type aluminum alloys. In this work, the effects of hydrogen atoms on the mechanical properties of Mg<sub>2</sub>Si are investigated by first principle calculation, which is based on the density function theory. First of all, we calculate the single crystal elasticity constants of <i>C</i><sub>11</sub>, <i>C</i><sub>12</sub> and <i>C</i><sub>44</sub>. Then the elasticity modulus, Poisson’s ratio and hardness of polycrystalline are calculated by using the crystal elasticity constants. Furthermore, we also calculate the tensile properties of Mg<sub>2</sub>Si with and without H atoms. The difference between the densities of states with and without H atoms is used to investigate the change of Mg<sub>2</sub>Si induced by H atoms. The results show that hydrogen atoms significantly reduce the shear modulus and elastic modulus of Mg<sub>2</sub>Si, resulting in the strength and hardness decreasing, but the toughness increasing. The calculations of tensile properties indicate that H atoms reduce the fracture strength but enhance the fracture elongation of Mg<sub>2</sub>Si. The analysis of density of states indicates that hydrogen atoms will induce the properties of Mg<sub>2</sub>Si to transform from semiconductor to metal properties. The calculated results in this paper can provide a reference basis for revealing the mechanism of strength reduction of Mg<sub>2</sub>Si materials in a hydrogen environment.

Atom doping in α-Fe2O3 thin films to prevent hydrogen permeation

Prevention of hydrogen (H) penetration into passive films and steels plays a vital role in lowering hydrogen damage. This work reports effects of atom (Al, Cr, or Ni) doping on hydrogen adsorption on the α-Fe2O3 (001) thin films and permeation into the films based on density functional theory. We found that the H2 molecule prefers to dissociate on the surface of pure α-Fe2O3 thin film with adsorption energy of −1.18 eV. Doping Al or Cr atoms in the subsurface of α-Fe2O3 (001) films can reduce the adsorption energy by 0.03 eV (Al) or 0.09 eV (Cr) for H surface adsorption. In contrast, Ni doping substantially enhances the H adsorption energy by 1.08 eV. As H permeates into the subsurface of the film, H occupies the octahedral interstitial site and forms chemical bond with an O atom. Comparing with H subsurface absorption in the pure film, the absorption energy decreases by 0.01–0.22 eV for the Al- and Cr-doped films, whereas increases by 0.82–0.96 eV for the Ni-doped film. These results suggest that doping Al or Cr prevents H adsorption on the surface or permeation into the passive film, which effectively reduces the possibility of hydrogen embrittlement of the underlying steel.

Impact of Hot Bending on the High-Temperature Performance and Hydrogen Damage of 2.25Cr-1Mo-0.25V Steel

The impact of hot bending forming process on the high-temperature mechanical properties and hydrogen damage of 2.25Cr-1Mo-0.25V steel was investigated by scanning electron microscope (SEM), transmission electron microscope (TEM), energy-dispersive spectrum (EDS) and the slow strain rate tensile (SSRT) test in high-temperature hydrogen environment. The samples containing hot bending residual influence were extracted from a real hydrogenation reactor shell fabricated through hot bending–welding process. SEM images of the material demonstrated that the density and size of carbides in 2.25Cr-1Mo-0.25V increased after forming. TEM and EDS results revealed that ferrite matrix of the formed material was purified. The mechanical properties measured by SSRT test manifested that 2.25Cr-1Mo-0.25V was softened after forming. Moreover, it was observed that high-temperature hydrogen environment embrittled the material and the susceptibility to hydrogen damage increased after forming. The role of hot bending process on the evolution of mechanical properties and hydrogen damage susceptibility was discussed. Possible mechanism for the impact of hot bending process on the high-temperature hydrogen damage was proposed.

Relationship between microstructural features in pipeline steel and hydrogen assisted degradation

Abstract The contributions of various microstructural features towards hydrogen-assisted degradation in API 5L X80 pipeline steel have been investigated. The current study was conducted on specimens obtained from the top surface and mid-thickness layers. After microstructural characterization on the RD-TD plane of each specimen, the mechanical response was investigated with and without in-situ hydrogen charging; before probing the electrochemical behavior in hydrogen producing and non-hydrogen producing corrosive environments. Despite reduced tensile and yield strengths, the mid-thickness layer showed relatively greater resistance to failure under both testing conditions. The increased susceptibility to hydrogen damage at the top surface layer was linked to higher strength and lower ductility. Also, the microstructure at the mid-thickness region contained mainly acicular ferrite, while the top surface was dominated by bainitic-acicular ferrite. In addition, the crystallographic orientation of grains spread towards 〈111〉‖ND and 〈110〉‖ND texture fibers (specifically, 〈123〉‖ND) at the mid-thickness; unlike the top surface which had mostly 〈001〉‖ND textured grains (specifically, 〈013〉‖ND).

Experimental investigation on deuterium effects on the tensile performance of two types of China Reduced Activation Ferritic-Martensitic steels

The present work is aimed to study on the effect of deuterium on mechanical properties of two martensitic steel, i.e. CLAM steel and CLF-1 steel. Tensile tests were operated at room temperature before and after deuterium charging. The results showed the ultimate tensile stress and area reduction coefficient of both steels were decreased after deuterium charging. The shrinkage rates of hydrogen induced reduction of area of CLAM steel and CLF-1 steel were 18.65% and 45.98%, respectively, which showed poor resistance to hydrogen embrittlement. This may be related to a lot of lath martensite phase in both steels. And the mechanism of even more sensitive to hydrogen damage for CLF-1 steel is probably due to its finer prior austenite and lath martensite phase, higher contents of carbide particles, as well as more hydrogen content and lower diffusivity.

HELP versus HEDE in progressively cold-drawn pearlitic steels: Between Donatello and Michelangelo

Abstract This paper reviews previous research by the author in the field of hydrogen effects on progressively cold-drawn pearlitic steels in terms of hydrogen degradation (HD), hydrogen embrittlement (HE) or, at the micro-level, hydrogen-assisted micro-damage (HAMD), thus affecting their microstructural integrity and compromising the (macro-)structural integrity of civil engineering structures such as prestressed concrete bridges. In particular, the two classical hydrogen-assisted deterioration micro-mechanisms are discussed, namely, hydrogen-enhanced localized plasticity (HELP) and hydrogen-enhanced decohesion (HEDE), together with their role in the embrittlement process as a function of the degree of cold-drawing undergone by each steel (associated with a different level of microstructural orientation of pearlitic colonies and lamellae). It is seen that hydrogen effects in pearlitic microstructure (either oriented or not) are produced at the finest micro-level by plastic tearing in the form, in general, of hydrogen damage topography (HDT) with different appearances depending of the cold drawing degree, evolving from the so-called tearing topography surface (TTS) in hot-rolled (not cold-drawn at all) or slightly cold-drawn pearlitic steels to a sort of enlarged and oriented TTS (EOTTS) in heavily drawn steels (the pronounced enlargement and marked orientation being along the wire axis or cold drawing direction). Whereas the pure TTS mode (null or low degree of cold drawing) resembles the Michelangelo stone sculpture texture (MSST), the EOTTS mode does the same in relation to the Donatello wooden sculpture texture (DWST).

Hydrogen damage in metals

In corrosive environment, the hardness along the depth direction and crack propagation direction of specimen is affected by hydrogen concentration and stress. In this paper, micro-hardness tester was employed to quantitatively evaluate the hydrogen distribution in metals. Hydrogen saturated value and hydrogen saturated layer of specimens were obtained. The experimental results demonstrated that hydrogen concentration behavior in a known equibiaxial stress environment can be verified experimentally using micro-hardness technique. There is a simple additive relationship between the hydrogen-induced micro-hardness increment and the stress-induced micro-hardness increment in Vickers micro-hardness measurement. The hydrogen distribution of specimens was analyzed by taking the change of the micro-hardness increment along the depth direction and crack propagation direction of specimens as the indicator.

Hydrogen embrittlement of super duplex stainless steel – Towards understanding the effects of microstructure and strain

The effects of austenite spacing, hydrogen charging, and applied tensile strain on the local Volta potential evolution and micro-deformation behaviour of grade 2507 (UNS S32750) super duplex stainless steel were studied. A novel in-situ methodological approach using Digital Image Correlation (DIC) and Scanning Kelvin Probe Force Microscopy (SKPFM) was employed. The microstructure with small austenite spacing showed load partitioning of tensile micro-strains to the austenite during elastic loading, with the ferrite then taking up most tensile strain at large plastic deformation. The opposite trend was seen when the microstructure was pre-charged with hydrogen, with more intense strain localisation formed due to local hydrogen hardening. The hydrogen-charged microstructure with large austenite spacing showed a contrasting micro-mechanical response, resulting in heterogeneous strain localisation with high strain intensities in both phases in the elastic regime. The austenite was hydrogen-hardened, whereas the ferrite became more strain-hardened. SKPFM measured Volta potentials revealed the development of local cathodic sites in the ferrite associated with hydrogen damage (blister), with anodic sites related to trapped hydrogen and/or micro voids in the microstructure with small austenite spacing. Discrete cathodic sites with large Volta potential variations across the ferrite were seen in the coarse-grained microstructure, indicating enhanced susceptibility to micro-galvanic activity. Microstructures with large austenite spacing were more susceptible to hydrogen embrittlement, related to the development of tensile strains in the ferrite.

Evaluation of hydrogen damage in a fire tube using microstructure/mechanical properties studies

In this paper, a damaged fire tube of H-500 vessel in Naftshahr operational area was investigated. The damages were reported as circumferential cracks at the joint of the fire tube to oval flange, which was led to leakage at U-turn section, local corrosion at the welding lines and observing scales at the outer surfaces of the fire tube. Microstructure studies were conducted at different zones (base metal, HAZ, welding line and cracked areas) for a cracked U-turn of the fire tube using optical microscopy, scanning electron microscopy (SEM) and SEM/EDS analysis. The results showed that the initial microstructure of the fire tube was laminar ferritic-pearlitic, whereas, the heat affected zone of the welding line contained grain boundary and Widmanstatten ferrite. MnS particles were also seen in the microstructure with elongated morphology and circumferential cracks. At the HAZ of welding lines, step-wise cracking was observed as an accumulation of the voids around MnS particles. This could be an indicative of hydrogen induced cracking (HIC). Mechanical properties (hardness, impact energy and tensile strength) of the four studied zones were investigated and showed that all the properties were in agreement with the standard values for ASTM A516 Gr 70 N, the steel of the fire tube, and their variation was based on the microstructural evolution. Therefore, these results showed no probability of hydrogen embrittlement.

Hydrogen damage in 34CrMo4 pressure vessel steel with high tensile strength

Various efforts have been made to improve the safety of high-pressure gas cylinders for hydrogen or natural gas with high strength steel liners. Metal liners with high tensile strength have a safety concern, particularly with hydrogen gas or hydrogen generating environments. The hydrogen can permeate into the liner material, and make the material brittle, causing hydrogen damage. This study investigated resistance to hydrogen damage for two kinds of 34CrMo4 steel with different strength levels. Hydrogen was charged with the electrochemical method, and the material strength was measured by the small punch testing technique. Hydrogen concentration of the specimen was also measured for every testing condition, with various charging periods. The specimens with high tensile strength absorbed more hydrogen than the regular tensile strength specimens. The absorbed hydrogen caused internal damage of intergranular cracking and blistering. Material ductility at failure decreased, as the hydrogen concentration of the specimen increased. But the hydrogen concentration had virtually no effect on the strength of the materials with hydrogen. These results confirm that the susceptibility to hydrogen damage of the high tensile strength materials is much higher than that of the materials with regular strength. If the metal liner of a hoop-wrapped cylinder vessel of type II has high tensile strength, general corrosion at the liner surface can cause a hydrogen rich environment, and the cylinder can suffer hydrogen damage and embrittlement. Therefore, controlling the strength level under an optimal level is critical for the safety of a cylinder made with 34CrMo4 steel.

Interaction between plastic deformation and hydrogen damage behavior of 30CrMnSiNi2A steel

The interaction between plastic deformation and hydrogen damage behavior of 30CrMnSiNi2A steel was investigated by pre-strain tensile tests and hydrogen charging by electrochemical method. This paper mainly contains two parts. The plastic deformation was restrained by hydrogen-charged, and the effect of hydrogen brittleness damage behavior was accelerated by pre-plastic deformation measure. Tensile pre-strian tests with hydrogen charging at current density from 0 to 50 mA/cm2 for 120 min were performed at room temperature. Both rate of reduction in areaand elongation were decreased due to the transition from ductile to brittle fracture by hydrogen charging, which meant the ability of plastic deformation was reduced by hydrogen. With hydrogen concentration increasing, yield strength also increased indicating that the plastic deformation forming conditions of steel were improved by hydrogen. Hydrogen content increased with pre-strain measured by glycerol gas collection method. Due to the pre-strain measure before hydrogen charging, the reduction of area and elongation were further reduced, while the strength was unexpectedly low. It was because pre-strain promoted the formation of hydrogen-induced crackings (HIC). This proved that the plastic deformation promoted the generation of hydrogen damage.

Hydrogen effect on the fatigue behavior of LBM Inconel 718

For several years, Inconel 718 made by Laser Beam Melting (LBM) has been used for components of the Ariane propulsion systems manufactured by ArianeGroup. In the aerospace field, many components of space engines are used under hydrogen environment. The risk of hydrogen embrittlement (HE) can be therefore a first order problem. Consequently, to improve the HE sensitivity of LBM Inconel 718, a systematic approach needs to be developed to characterize the microstructure at different scales and its interaction with hydrogen. This study addresses the impact of gaseous hydrogen on the material mechanical behavior under fatigue loadings. In a first step, the low cycle fatigue behavior under 300 bar of hydrogen gas has been evaluated with specimen loaded at a constant load ratio of R=0.1 and a frequency of 0.5 Hz. A reduction in the cycle number of fracture is shown. This reduction of fatigue life is a consequence of the impact of hydrogen damage processes. The impact of hydrogen is evaluated at the stages of crack initiation, crack propagation. These results are discussed in relation with the hydrogen embrittlement mechanisms and particularly in terms of hydrogen / plasticity interactions. To achieve this, the fracture surface morphology was first examined using scanning electron microscopy and second samples near the fracture surface were extracted using Focused-Ion Beam machining from regions containing striation. The main result observed is a reduction of the size of dislocation organization in relation with a decrease of the striation distance.

Broadening Horizons – Welcome to Advanced Theory and Simulations

We are proud to present the inaugural issue of our new interdisciplinary premium journal Advanced Theory and Simulations, addressing the growing importance of the development and application of theoretical methods, modeling and simulation approaches in all natural science, medicine and engineering areas. Reflecting the broad scope of the new journal, we are pleased to be supported by the members of a topically and geographically diverse Editorial Advisory Board of leading scientists in their respective fields: Jean-Luc Brédas (Georgia Institute of Technology, Atlanta, USA), Emily Carter (Princeton University, USA), Maytal Caspary Toroker (Technion IIT, Haifa, Israel), Liang Chen (Ningbo Institute of Industrial Technology, Zhejiang, China), Clémence Corminboeuf (Ecole polytechnique fédérale de Lausanne, Switzerland), Bert de Groot (Max Planck Institute for Biophysical Chemistry, Göttingen, Germany), Stefan Grimme (University of Bonn, Germany), Chi-Ok Hwang (Gwangju Institute of Science and Technology, South Korea), Natalie Kalev-Kronik (Hadassah Medical Center, Jerusalem, Israel), Toshihiro Kawakatsu (Tohoku University, Sendai, Japan), Alexei Khokhlov (Moscow State University, Russia), Kurt Kremer (Max Planck Institute for Polymer Research, Mainz, Germany), Leeor Kronik (Weizmann Institute of Science, Rehovoth, Israel), Jürgen Kurths (Potsdam Institute for Climate Impact Research, Germany), Javier Llorca (Madrid Institute for Advanced Studies of Materials, Spain), Jinhu Lu (Research Center for Network Science, Beijing, China), Siewert-Jan Marrink (University of Groningen, The Netherlands), Yifei Mo (University of Maryland, College Park, USA), Rosalba Perna (Stony Brook University, USA), Zhigang Shuai (Tsinghua University, Beijing, China), Berend Smit (University of California, Berkeley, USA), Sean Smith (University of New South Wales, Sydney, Australia), Richard M. W. Wong (National University of Singapore), Xin-Cheng Xie (Peking University, Beijing, China), Yong-Wei Zhang (Institute of High Performance Computing, Singapore). The current first issue already provides a first glimpse at some of the topical range Advanced Theory and Simulations intends to cover, presenting work on semiconductor interfaces, on non-amphiphilic structures, on one-dimensional materials, on the theory of critical distances, or on hydrogen damage protection. We sincerely hope that you enjoy reading this very first issue of the new journal and look forward to receiving soon some of your best research for publication. The Editorial Team of Advanced Theory and Simulations

Passivation of hydrogen damage using graphene coating on α-Fe2O3 films

We report the demonstration of graphene as a passive layer that prevents hydrogen damage of steels. The effectiveness of the hydrogen damage inhibition is evaluated using graphene on α-Fe2O3 films. It's been observed that the work function increases under both compressive and tensile strains compared with α-Fe2O3 films without graphene coating, which indicates that the graphene coating strained surface layer became more corrosion resistant. The investigation of strain effect on the work function would help fundamentally understand the corrosion behavior. Our findings confirm that the graphene coating is an effective means to inhibit corrosion, even on deformed steels.