Hydrogen-induced Cracking Research Articles

Exploring the hydrogen embrittlement behavior in nickel-economized austenitic stainless steel: Investigating the role of manganese in modifying hydrogen-induced crack mechanisms

The hydrogen embrittlement (HE) susceptibility in nickel-economized austenitic stainless steels (NEASSs) with varying manganese content was explored based on the statistical results of hydrogen-induced cracks (HICs) characterization after slow strain rate tensile (SSRT). With almost the same initial microstructure, manganese modifies the deformation patterns of NEASSs by adjusting stacking fault energy, which essentially influences the initiation and propagation mechanisms of HICs and eventually results in different brittle fracture modes. Additionally, different ways of HIC initiation and propagation caused significant differences in brittle-fracture areas and HICs lengths after SSRT tests, which resulted in great variations in HE susceptibility between NEASSs.

Annealing cracking in Zr and a Zr-alloy with low hydrogen concentration

Hydrogen embrittlement, also known as hydrogen-induced cracking, is a longstanding concern for zirconium (Zr) and its alloys. The affinity for hydrogen in zirconium results in the formation of brittle hydrides. Hydrides are conventionally thought to facilitate crack propagation, and the prevailing recommendation to hinder hydride embrittlement involves reducing the hydrogen concentration in the material and applying slow cooling to reduce thermal stresses. Here, in Zr with a maximum hydrogen concentration of 43 wppm, we show that cracks initiate unexpectedly after annealing, a step that involves slow cooling and no external stress. With a suite of high-resolution microscopy, we show that annealing cracks initiate at prismatic δ-hydrides, whose presence is unexpected. The microscopic annealing crack paths are consequently crystallographic, following the habit plane of these prismatic δ-hydrides. The commonly reported γ-hydride and δ-hydrides that develop on the basal plane are found not to initiate cracks. We rationalize that prismatic δ hydrides result from the intergranular thermal residual stresses that develop during slow cooling. This finding of uncommon annealing cracking further advances the mechanistic understanding of hydride embrittlement in zirconium and can lead to new strategies for design and fabrication of advanced zirconium alloys for harsh environments.

Quantitative analysis of local plasticity accompanying hydrogen-related fracture in low-carbon martensitic steel

In this study, the local plasticity accompanying hydrogen-related fracture in a low-carbon martensitic steel was quantitatively investigated by correlative microscopy analysis combining digital image correlation technique and electron backscatter diffraction. The results revealed that strain localization occurred mainly in the bulk of martensite blocks and at prior austenite grain boundaries, both with and without the presence of hydrogen. Moreover, hydrogen enhanced strain localization during deformation and facilitated crack nucleation and propagation. The quantitative analysis showed that the hydrogen-related quasi-cleavage cracking was closely related to the local plastic deformation, and increasing hydrogen content decreased the local strain level required for quasi-cleavage cracking. It was found that strain localization also occurred around the intergranular cracks, suggesting that hydrogen-induced intergranular cracking was not a classical simple decohesion process and strain localization was involved in the sequence of hydrogen-induced intergranular cracking. These findings shed light on the understanding of the intrinsic nature of hydrogen embrittlement.

Uncovering the origin of critical hydrogen concentration for initiation of hydrogen-induced cracking and its relation to inclusion type and size

This paper presents a theoretical criterion and approach for determining the relationship between the critical hydrogen concentration for hydrogen-induced cracking (HIC) initiation and the type and size of non-metallic inclusions. We used plate-like MnS and sphere-like Al2O3 as representative inclusions for in-depth analyses. Our results indicate that decreasing inclusion size increases the hydrogen concentration required for HIC initiation, particularly in the range of small inclusion sizes. Al2O3 exhibits a higher susceptibility to HIC than MnS. Each type of inclusion has a specific hydrogen concentration below which crack initiation cannot begin. The critical concentration for HIC initiation in the entire steel corresponds to the lowest value among these concentrations. This study provides a quantitative and comprehensive solution to this issue.

Enhancing wear and corrosion resistance of electroless Ni-P coatings in CO2-saturated NaCl solution through polytetrafluoroethylene incorporation

In the realm of oil and natural gas, material durability is compromised by sand particle abrasion, corrosive media, and hydrogen-induced cracking. This study investigates the impact of PTFE on wear and corrosion resistance of Ni-P coatings in a CO2 environment. Hydrogen barrier properties of the substrate, Ni-P, and PTFE are evaluated using the Devanathan-Stachursky cell. Results show that incorporating PTFE enhances the coating's wear and corrosion resistance, and hydrogen barrier performance compared to substrate and Ni-P alone. The coating effectively hinders corrosive media transmission. A comprehensive analysis of the Ni-P-PTFE corrosion mechanism is provided, along with a robust corrosion model.

Influence of metallurgical factors on the hydrogen induced cracking of carbon steel wires in H2S-containing environments

Flexible pipes armor wires used in offshore oil and gas fields can corrode if water and acid gases, such as H2S, build up in the annulus. Such an environment may provide the conditions for hydrogen-induced cracking (HIC) depending on the corrosive solution composition and the metallurgical characteristics of the armor wire, such as microstructure and microhardness. The critical zones of HIC incidence were investigated for tensile and pressure armor wires with carbon content of 0.7 and 0.3 wt% C, respectively. Results were obtained through immersion testing and hydrogen permeation measurements in near neutral substitute ocean water (solution A) and standard acid solution (solution B) at ambient temperature bubbled with a gas mixture (1 % H2S + 99 % N2). Scanning electron microscope (SEM) and computed tomography (CT) evidenced the microstructure and microhardness features associated to crack morphology and location. According to the results, the increase of carbon content in cold drawn steels promoted the accumulation of hydrogen mainly in regions of high microhardness, inducing a high density of cracks in a stepwise cracking (SWC) propagation. This indicates that the driving force for HIC was associated with metallurgical factors, such as microhardness, the presence of hydrogen trapping sites of high energy, dislocations and ferrite/cementite morphology and distribution, occurring even in the absence of non-metallic inclusions. Additionally, environmental conditions, such as the low pH found in solution B, increased the criticality of HIC. Both materials presented a crack sensitivity ratio (CSR) that grew over time in solution B, but no cracks were observed in the pressure armor wire tested in solution A. Hydrogen permeation curves were delayed for both tested armor wires in solution A due to its near neutral pH characteristic. Hydrogen diffusivity (Deff) of the tensile armor wire was lower than the pressure armor wire, indicating the presence of a higher density of hydrogen trapping sites in a harder and elongated pearlite.

Impact and Detection of Hydrogen in Metals

AbstractThe widespread use of hydrogen as an energy carrier is considered one of the most important keys to achieving the decarbonization necessary for the energy transition in numerous areas of technology and society. Not least due to the associated contact of metallic components with (pressurized) hydrogen, there is a latent risk of hydrogen-induced cracking (“hydrogen embrittlement”). The cause of damage is the hydrogen absorbed by the material, which is mobile via interstitial lattice diffusion. In high-strength steels with a tensile strength of more than 800 MPa, even very low diffusive hydrogen contents of less than 1 ppm (parts per million) can have a crack-inducing effect. Hence, dedicated, highly accurate analytical and testing methods are required for the detection of hydrogen and its effect on the mechanical properties of metals. This paper summarizes the current state of knowledge regarding hydrogen embrittlement and reviews the analytical, mechanical, and fractographic investigation methods for detecting hydrogen in metals.

New insight into the fitness of 13Cr stainless steel in H2S-containing environment at high temperature

In the oil and gas industry, the selection of tubing and casing materials is required to follow international standard ISO 15156. However, it does not provide guidance on selecting stainless steel materials for H2S-containing wells above 232 °C, which raises uncertainty about the suitability of 13Cr steel. This work focuses on investigating the mechanical degradation and failure mechanisms of 13Cr stainless steel exposed to high-temperature conditions and proposed a creep constitutive model. Then, the corrosion and cracking mechanisms of 13Cr stainless steel at temperatures ranging from 150 °C to 350 °C were elucidated. Results show that 13Cr stainless steel meets the current material selection criteria (GB/T34907-2017) for mechanical properties and creep resistance. In the range of 150–250 °C, the localized corrosion is dominant, and stress-oriented hydrogen-induced cracking occurs at 150 °C. As the temperature increases from 250 °C to 350 °C, although the maximum value of uniform corrosion rate is as high as 0.2960 mm/a, the cracking does not happen. Therefore, with the implementation of suitable protective measures, 13Cr stainless steel can be utilized in wells that the temperatures ranging from 250 °C to 350 °C and H2S partial pressures up to 0.17 MPa. This aligns with the global carbon-neutral agenda.

Rapid evaluation of the critical condition for hydrogen-induced cracking in ultrahigh-strength automotive steel sheets: A semiquantitative investigation based on U-bend specimens

The production of automotive steel plates, which involves pickling, electroplating, and welding among other steps, introduces hydrogen. Additionally, during the service life of components fabricated using such plates, electrochemical corrosion occurs, and hydrogen atoms are introduced. The hydrogen atoms are adsorbed and diffused into the interior of the metal, accumulating at any defects. Automotive parts are commonly fabricated using cold forming techniques. The hydrogen embrittlement sensitivity of ultrahigh-strength automotive sheets (UHSSs) is influenced by the stress, concentration of diffusible hydrogen, and plastic strain resulting from the cold forming process. The standard methods for quantitative studies on the UHSS hydrogen embrittlement sensitivity, such as the constant-load testing and low-strain-rate testing, require a specialized equipment and extended experimental period, making them impractical for original automotive equipment manufacturers. This study focuses on the use of the quenching and partitioning (QP) steel QP1180, which contains residual austenite, and martensite steel MS1500, which has a low deformation ability but high strength, as research objects. The equivalent strain and stress were controlled by adjusting the bending radius and U-bend opening distance, while the diffusible hydrogen concentration was charged through immersion. The fracture time of the U-bend sample was recorded, and the critical diffusible hydrogen concentration for hydrogen-induced cracking was measured. Additionally, the stress distribution during the U-bending process was simulated using the finite-element method. To evaluate the hydrogen embrittlement resistances of QP1180 and MS1500, the area enclosed by the load stress and equivalent strain (bending radius) and fracture time were semiquantitatively determined. Finally, the hydrogen-induced delayed fracture space regions of QP1180 and MS1500 were determined in the three-dimensional space, with equivalent strain, load stress, and diffusible hydrogen concentration as coordinate axes. This provided a convenient and reliable means of determination of the critical conditions for a safe service and rapid evaluation of the hydrogen embrittlement sensitivity of ultrahigh-strength automotive sheets.

An experimental and statistical study on the characteristics of non-metallic inclusions that serve as hydrogen-induced crack nucleation sites in pipeline steel

This study consists of a statistical study to identify spatial distribution parameters of non-metallic inclusions (NMIs) at hydrogen-induced cracking (HIC) nucleation sites in both low-strength and high-strength steel pipes. The electrochemical cathodic charging method was used to induce HIC in pipeline steel plates, and the nucleation of the HIC was monitored using straight beam ultrasonic testing. Optical microscopy (OM) and scanning electron microscopy (SEM) were used to evaluate the shape, size, area fraction, and separation distance of NMIs. The hydrogen microprint technique (HMT), electron backscattered diffraction (EBSD) analysis, and finite element (FE) stress analysis were performed to characterize HIC nucleation sites. The findings showed that cubical and spinal NMIs, characterized by strong hydrogen trapping capacity due to high misfit strain and von Mises stress, are favored sites for HIC nucleation. The main finding of this study is that the shape and sharpness of NMIs are the factors that determine when NMIs will be a HIC nucleation site, rather than size, as generally accepted.

Designing Around Hydrogen Embrittlement

Abstract There are issues to work out before hydrogen can see widespread use as a fuel. One such barrier is a condition called hydrogen embrittlement, also known as hydrogen-assisted cracking or hydrogen-induced cracking, which causes cracks in steel tanks and pipes exposed to hydrogen.

Hydrogen induced cracking behavior of the dual-phase Co30Cr10Fe10Al18Ni30Mo2 eutectic high entropy alloy

In this paper, the hydrogen induced cracking behavior of the Co30Cr10Fe10Al18Ni30Mo2 eutectic high entropy alloy was studied. The results showed that the strength and ductility of the alloy decreased after hydrogen pre-charging, and quasi-cleavage fracture features and hydrogen-induced cracks were found. Moreover, the cracks induced by hydrogen pre-charging were found to propagate along the two-phase interface and inside the BCC phase.

Experimental observations of nucleation and crack growth paths of hydrogen-induced cracking in pipeline steel

The microstructural features that favor hydrogen-induced cracking (HIC) in internal, middle, and external layers of pipeline steels were investigated. The electrochemical cathodic charging was used to induce HIC, and straight beam ultrasonic inspection was identified in which steel layers HIC nucleate and grow. The cracked plates were examined by optical microscope and scanning electron microscope (SEM). The hydrogen microprint technique (HMT) was used to visualize the site of high hydrogen concentrations. Electron backscatter diffraction (EBSD) was used to analyze the role of crystallographic texture in HIC pathways. The results revealed that HIC nucleation and growth are influenced by the segregation degree and inclusion contents, which are higher in the internal surface layer of our studied steels but not consistently so in the middle thickness layer. Further, HIC nucleated in cuboidal and spinal inclusions and propagated along ferrite/pearlite bands with high misorientations. The HMT results showed that hydrogen is present in pearlite colonies, grain boundaries, and non-metallic inclusions. The results indicated that HIC is not solely controlled by the crack geometry.

Effect of pre-strain on hydrogen induced cracking of PAW welded 304 austenitic stainless steel

Strain-hardened austenitic stainless steel (γ-SS) is extensively used in high-pressure hydrogen systems after welding. The weld may experience varying degrees of hydrogen embrittlement (HE) with different levels of pre-strain, which seriously threatens the reliability of hydrogen systems. Therefore, it is vital to research the effect of pre-strain on hydrogen-induced cracking of γ-SS welds. In this research, the impact of hydrogen on the mechanical properties of type 304 γ-SS plasma arc welding (PAW) welds with different levels of pre-strain are studied through slow strain rate tensile (SSRT) test. The pre-strain of the weld after hydrogen charging is optimized, then the causes of hydrogen-induced cracking are illustrated by microstructure analysis. The weld metal zone (WMZ) has a greater HE susceptibility than the base metal zone (BMZ). The HE susceptibility of the weld can decrease after solution-treated. The fracture of the weld with pre-strain of 5% is mainly due to dislocation and ferrite increasing the HE susceptibility. When the pre-strain is above 10%, the weld metal and the base metal have undergone a severe transformation from austenite to α′ martensite. The content of α′ martensite rises with the rising pre-strain. The HE susceptibility of the weld is greater than the base metal due to the influence of dislocations and ferrite. The brittle fracture is initiated primarily at the phase boundary. The strength of welds can be improved while keeping good HE resistance with pre-strain of 5%.

The effect of V8C7 size on hydrogen diffusion behavior and hydrogen induced cracking in pipeline steel

This study revealed the relationship between V8C7 size and hydrogen diffusion behavior as well as hydrogen induced cracking (HIC) in pipeline steel. Hydrogen permeation and HIC susceptibility tests were implemented on five conditions with different V8C7 sizes but identical volume fractions. The results proved that with increasing of V8C7 size, the hydrogen effective diffusivity was first decreased and then increased. Increasing the proportion of small size (coherent and semi-coherent) V8C7 increased the effective hydrogen trapping densities, decreased hydrogen diffusion coefficient, improved the distribution of diffusible hydrogen atoms and then the HIC susceptibility of steels was decreased.

Molecular dynamics modeling of hydrogen-induced plastic deformation and cracking of ɑ-iron

In this work, molecular dynamics modeling was conducted to study hydrogen (H)-induced plastic deformation and cracking of polycrystal α-Fe. Under cyclic loading, the number of vacancies and the stress intensity increase with H atom concentration and the number of loading cycles. However, the effect of cyclic loading on cracking is not as significant as the increment of H concentration. As the H concentration increases, the dislocation generation and emission are enhanced in the {110}<111> slip system, but are inhibited in other slip systems. There is a critical H atom concentration, below which the plastic deformation of α-Fe is facilitated by H atoms. When the critical H concentration is exceeded, the dislocation emission is inhibited by H atoms at grain boundaries, where the H atoms can pin dislocations, causing piling-up of the dislocations to generate a stress concentration.

Hydrogen embrittlement in a metastable high Mn TWIP-assisted steel: Correlation between grain size and hydrogen-enhanced ε-martensite

The correlation between hydrogen-enhanced deformation-induced ε-martensite and hydrogen embrittlement at two different grain sizes has been investigated in a metastable high Mn steel. The variation in the fraction of ε-martensite was detected to be 34% for coarse grain (CG) and 10% in (FG) after hydrogen charging. The significant difference in ε-martensite fraction between CG and FG was attributed to a higher concentration of hydrogen per unit area (CHgb) of high-angle boundaries (θ > 15°) in CG compared with FG one, which caused a local decrease of stacking fault energy (SFE) at the vicinity of these boundaries in favor of martensitic transformation. Intergranular cracks were identified as the primary form of hydrogen damages, occurring more frequently than transgranular features in both alloys. The drastic hydrogen embrittlement in CG was attributed firstly to higher hydrogen concentration per grain boundary unit area and secondly to the more severe hydrogen cracking in CG than FG resulting from explosive hydrogen-enhanced martensite formation. In the FG , deformation twins and single-variant ε-martensite were the primary mechanisms triggering intergranular crack nucleation. However, they played a dual role in crack propagation, either arresting or facilitating crack growth. They were capable of arresting the crack if suitably aligned with the direction of crack propagation and the tensile axis. Conversely, in CG structure, the intense impingement of multiple-variant ε-martensite grains with each other and with grain boundaries can create severe microstructural stress concentration zones, promoting severe hydrogen-induced cracking.

A coupled diffusional-mechanical model accounting for hydrogen enhancements of strain-induced dislocations and vacancies

Informed by the current understanding of hydrogen-dislocations/vacancies interactions, a coupled diffusional-mechanical model accounting for hydrogen-enhanced strain-induced dislocations and vacancies is developed. This model is applied to capture hydrogen diffusion and trapping in the uniaxially tensioned column and type-I loaded crack specimens of nickel alloy, with special attentions paid to the influence of hydrogen-vacancies interaction on them, which is seldom discussed in previous studies. The results show that the hydrogen-enhanced hardening rate and the hydrogen-promoted vacancy enrichment for the nickel alloys observed in experiments can be addressed well by the present model. The strain-induced vacancies rather than dislocations dominate the hydrogen trapping behavior, due to their higher hydrogen binding energies for the nickel alloy. The hydrogen-saturated state of vacancies can heavily impact hydrogen diffusion/trapping, which could be characterized by the effective trap concentration. The supersaturated vacancies caused by hydrogen-enhanced strain-induced vacancies can promote void growth through vacancy condensation, thus accelerating plastic localization or interface rupture. For the type-I loaded blunt crack specimen, the hydrogen-enhanced dislocation multiplication contributes to intergranular cracking in the pressure valley, while hydrogen-enhanced vacancy generation facilitates void growth in the plastic zone, both of which can exacerbate plastic localization ahead of crack tip. A quantitative model for plasticity localization that accounts for the influences of hydrogen-induced IG cracking and void growth would be helpful in physically based modeling of hydrogen embrittlement.

Hydrogen Embrittlement Behavior of a Commercial QP980 Steel

The hydrogen embrittlement (HE) behavior of a commercial QP980 steel is studied in this work. The HE susceptibility results indicate that QP980 suffers from a severe HE, and the fracture mode transforms from ductile dimpling to brittle quasi-cleavage under the attack of hydrogen. The EBSD results show that strain-induced martensite transformation can rarely occur at a strain close to the HE fracture strain, which is mainly attributed to the high mechanical stability of austenite. The TKD-KAM analysis results indicate that hydrogen-induced strain localization in martensite can be mitigated by the hydrogen-trapping effect of surrounding austenite, while it is most pronounced in martensite adjacent to ferrite. Correspondingly, HE cracking is considered to initiate in martensite adjacent to ferrite under the synergistic action of HELP and HEDE mechanisms, and then cracks can propagate through ferrite or along phase interfaces. Our findings suggest that to further improve the HE resistance of QP steel with stable austenite, it is necessary to consider introducing effective hydrogen-trapping sites (such as carbides, film austenite) into martensite, which is deemed to be beneficial for increasing the resistance against hydrogen-induced cracking initiation in martensite.

Hydrogen-induced cracking of X70 steel affected by sulfate-reducing bacteria and cathodic potential: experiment and density functional theory study

Submarine pipeline are often exposed to the risk of hydrogen embrittlement from the dual action of marine sulfate-reducing bacteria (SRB) and cathodic protection (CP). In this work, hydrogen permeation test, slow strain rate tensile (SSRT) experiments, and density functional theory (DFT) were used to explain the hydrogen embrittlement (HE) mechanism of subsea pipeline steel under the action of SRB and CP. When the applied CP potential is increased from −850 mV to −1200 mV, the hydrogen seepage current increases 1.8 times. And the tensile specimens pre-charged with hydrogen exhibit significant hydrogen embrittlement behavior. DFT calculations show that the increased concentration of hydrogen atoms on the material surface decreases the diffusion potential barrier, leading to a larger hydrogen seepage current. In addition, the aggregation of hydrogen atoms in the steel weakens the chemical bonds between Fe atoms, leading to hydrogen embrittlement.