Effect Of Hydrogen Embrittlement Research Articles

Hydrogen-enhanced fatigue crack growth of martensitic stainless steel: A predictive model and experimental validation

Atomic hydrogen (H) diffusion in metallic structures affects the mechanical properties of steel alloys. However, the effect of hydrogen embrittlement on the fatigue crack propagation rate (FCGR) is not fully understood, and serious uncertainties can affect the design and inspection schedules of hydraulic turbine runners based on the defect-tolerance approach. The FCGR in a complex microstructure such as tempered martensitic stainless steel is governed by the H content, stress distribution, and microstructure at the crack tip. The synergetic interactions between these parameters should be kinetically studied as the crack propagates. In this study, an original model was proposed to predict the influence of H on the fatigue crack propagation rate. The model was developed specifically for tempered martensitic stainless steels containing austenite. Subsequently, it was validated through experiments performed on 415 martensitic stainless steel containing 20% of reformed austenite (RA). The material’s FCGR was tested in its raw condition, also after charging with H. Compact tension (CT) specimens were tested at two constant stress intensity factor ranges (ΔK = 8 MPa.m0.5 and 15 MPa.m0.5) and three cyclic loading frequencies (f = 35 Hz, 3.5 Hz, and 0.35 Hz). The results show a very good agreement with the predictions of the model. Moreover, both the model and the experimental results reveal that there is a critical ΔK that is dependent on the loading frequency at which the impact of H on the FCGR is maximum. Moreover, as predicted by the model, a decrease in the loading frequency led to an increase in the susceptibility of the FCGR to H.

A local stress criterion to assess the effects of hydrogen embrittlement on the fracture strength of notched tensile specimens

This work addresses the applicability of a local criterion incorporating the coupling of critical stress and a critical hydrogen concentration to predict hydrogen embrittlement effects on the fracture strength of high strength steels using notched round specimens with different notch root radii. The numerical simulations incorporating a relatively simple hydrogen transport model provide strong support for the adoption of a failure criterion in terms of achieving a critical level of tensile stress coupled to the local hydrogen concentration, which, in turn, enable the construction of a failure locus for the degraded material. For the cases analyzed here, construction of such a failure locus based on a critical combination of maximum principal stress and hydrogen concentration enabled predictions of fracture strength for hydrogen-charged tensile specimens which are in very good agreement with experimental data. Overall, the results presented here lend additional support for further developments of a local stress-based criterion to predict hydrogen embrittlement effects on the fracture strength of high strength steels.

An experimental fracture mechanics study of the combined effect of hydrogen embrittlement and loss of constraint

This work presents a systematic investigation of the combined effect of hydrogen embrittlement and loss of constraint. The fracture mechanics experiments are performed on an advanced martensitic high strength steel using a single-edge-notch bend specimen, with different crack over height ratio, subjected to electrochemical in-situ hydrogen charging at various loading rates. It is found that the environmentally driven ductile-to-brittle transition region in fracture toughness is obtained for both the high and low constraint specimen configurations. This region is characterized by a change from transgranular dimple rupture to an intergranular mode of fracture. The transition region for the low constraint specimen is shifted towards longer hydrogen exposure times, which is an effect of the reduced hydrostatic stress ahead of the crack front compared to the high constraint specimen. The low constraint specimen exhibits significant plastic straining, which is reflected in a significant decrease in the fracture toughness due to hydrogen assisted transgranular dimple rupture.

Blending hydrogen in existing natural gas pipelines: Integrity consequences from a fitness for service perspective

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

Nanomechanical characterization of the hydrogen effect on high strength steels

The effect of hydrogen charging on nanohardness (HIT), elastic work (Welast), and plastic work (Wplastic) was investigated using nanoindentation. To accomplish this, two high-strength low-alloy steels (AISI 4130 M and AISI 4137 M) were tested using electrochemical nanoindentation with different loading rates (5 mN/min and 15 mN/min). Additionally, a continuous multicycle (CMC) indentation loading profile was proposed to assess the hydrogen embrittlement (HE) effect on AISI 4130 M steel. Under a current density of 0.5 mA/cm2 and 5 mN/min loading rate, AISI 4137 M steel exhibited a 30.6% reduction in Welast and a 9.8% increase in HIT value. In contrast, under the same conditions, Welast increased by 5.0% for AISI 4130 M steel. For the CMC indentation tests conducted on AISI 4130 M steel, both HIT and Welast values were affected, as evidenced by a reduction between 7% and 10% in HIT and between 4% and 22% in Welast. The lower deformation rates resulting from long-term CMC-type indentations enable hydrogen to follow the dislocation movement. In the experimental setup under study, the hydrogen-induced softening caused by the shielding of the elastic fields was observed as a reduction in nanohardness.

Enhancement of hydrogen embrittlement resistance in a Fe-18Mn-0.6C twinning induced plasticity steel by copper alloying

The effect of Cu alloying on hydrogen embrittlement (HE) in TWIP steel was studied using the low-speed linearly increasing stress test (LIST) with simultaneous cathodic hydrogen charging. Cu alloying influenced HE resistance by the following mechanism. (i) Cu alloying increased the stacking fault energy, which canceled out the embrittling effect of hydrogen on promoting local plasticity and mechanical twins/dislocations concentration. (ii) Cu alloying refined the austenite grains, especially after low-temperature (700 °C) annealing and thus delayed mechanical twinning that causes an increased hydrogen concentration. (iii) Cu alloying caused the formation of a Cu-rich surface which reduced the diffusible hydrogen content, particularly for the steel annealed at 900 °C. (iv) Cu alloying dispersed mechanical twins by Cu precipitate/Cu-rich clusters, which homogenized the diffusible hydrogen and decreased the local hydrogen concentration at the HE vulnerable interfaces. Mechanism (iv) in the 700 °C annealed Cu-alloyed TWIP steel produced the greatest increase in HE resistance.

Corrosion and Mechanical Behavior of the As-Cast and Solid-Solution-Treated AM50 Magnesium Alloy in Different Media

Hydrogen embrittlement and the anodic dissolution mechanism are two important aspects of the corrosion behavior of magnesium alloys. Here, to evaluate the effects of these two aspects on the corrosion failure of magnesium alloys under stress, the stress and corrosion behaviors of the AM50 magnesium alloy in air, deionized water, and NaCl solution after solid-solution (T4) treatment were investigated by X-ray diffraction, scanning electron microscopy, slow strain rate tensile testing, and vacuum dehydrogenation. The as-cast AM50 magnesium alloy was mainly composed of the α-Mg and β-Mg17Al12 phases. After T4 treatment, the amount of the β-Mg17Al12 phase was significantly reduced, and only a small amount existed at the grain boundaries. After T4 treatment, the stress corrosion resistance in deionized water improved, but it decreased in an NaCl environment. Dehydrogenation experiments showed that the effect of hydrogen on the corrosion process was weakened owing to the decrease of the β-Mg17Al12 phase after solution treatment. The effects of hydrogen embrittlement and the anodic dissolution mechanism on the corrosion behavior of the AM50 magnesium alloy under stress were different. In deionized water, the hydrogen embrittlement mechanism played the major role, while the anodic dissolution mechanism played the major role in the presence of Cl- ions.

Atomistic insights into stress corrosion cracking of α-Fe in supercritical water: The coupling effect of hydrogen embrittlement and intergranular corrosion

Mechanistically understanding stress corrosion cracking (SCC) of Fe-based alloy under extremely high-temperature and high-pressure conditions is a key challenge for designing and optimizing structural materials of the supercritical water (SCW) reactors. The mechanism of SCC of α-Fe in supercritical water has been investigated by reactive force-field molecular dynamics simulations, and it is obtained that SCC is caused by the coupling effect of hydrogen embrittlement and intergranular corrosion. Hydrogen atoms in metals induce vacancy formation when the loaded stress is larger than the threshold stress, resulting in forming stable vacancy-hydrogen clusters. These stable vacancies pin grain boundary (GB) and act as stress concentrators under sufficient tensile stress, leading to the generation of more vacancies. A large number of vacancies in GB promote intergranular corrosion which directly results in materials failure.

Improving the Quantification of Deuterium in Zirconium Alloy Atom Probe Tomography Data Using Existing Analysis Methods

Abstract Zirconium alloys are common fuel claddings in nuclear fission reactors and are susceptible to the effects of hydrogen embrittlement. There is a need to be able to detect and image hydrogen at the atomic scale to gain the experimental evidence necessary to fully understand hydrogen embrittlement. Through the use of deuterium tracers, atom probe tomography (APT) is able to detect and spatially locate hydrogen at the atomic scale. Previous works have highlighted issues with quantifying deuterium concentrations using APT due to complex peak overlaps in the mass-to-charge-state ratio spectrum between molecular hydrogen and deuterium (H2 and D). In this work, we use new methods to analyze historic and simulated atom probe data, by applying currently available data analysis tools, to optimize solving peak overlaps to improve the quantification of deuterium. This method has been applied to literature data to quantify the deuterium concentrations in a concentration line profile across an α-Zr/deuteride interface.

Hydrogen Embrittlement and its Effect on Fatigue Life of Nitrided Steel in Gigacycle Fatigue: Analysis and Modelling

This paper deals with the effect of hydrogen embrittlement on the fatigue life of steels. This phenomenon is typical for the gigacycle fatigue region, but we also encounter it in surface-treated materials. in which a subsurface crack initiation has occurred. In samples in which the fracture is affected by the presence of hydrogen embrittlement, subsurface fatigue crack initiation occurs. In this work we observe the change in toughness and local elastic modulus depending on the hydrogen diffusion of hydrogen over time.

Hydrogen Blending in Gas Pipeline Networks—A Review

Replacing fossil fuels with non-carbon fuels is an important step towards reaching the ultimate goal of carbon neutrality. Instead of moving directly from the current natural gas energy systems to pure hydrogen, an incremental blending of hydrogen with natural gas could provide a seamless transition and minimize disruptions in power and heating source distribution to the public. Academic institutions, industry, and governments globally, are supporting research, development and deployment of hydrogen blending projects such as HyDeploy, GRHYD, THyGA, HyBlend, and others which are all seeking to develop efficient pathways to meet the carbon reduction goal in coming decades. There is an understanding that successful commercialization of hydrogen blending requires both scientific advances and favorable techno-economic analysis. Ongoing studies are focused on understanding how the properties of methane-hydrogen mixtures such as density, viscosity, phase interactions, and energy densities impact large-scale transportation via pipeline networks and end-use applications such as in modified engines, oven burners, boilers, stoves, and fuel cells. The advantages of hydrogen as a non-carbon energy carrier need to be balanced with safety concerns of blended gas during transport, such as overpressure and leakage in pipelines. While studies on the short-term hydrogen embrittlement effect have shown essentially no degradation in the metal tensile strength of pipelines, the long-term hydrogen embrittlement effect on pipelines is still the focus of research in other studies. Furthermore, pressure reduction is one of the drawbacks that hydrogen blending brings to the cost dynamics of blended gas transport. Hence, techno-economic models are also being developed to understand the energy transportation efficiency and to estimate the true cost of delivery of hydrogen blended natural gas as we move to decarbonize our energy systems. This review captures key large-scale efforts around the world that are designed to increase the confidence for a global transition to methane-hydrogen gas blends as a precursor to the adoption of a hydrogen economy by 2050.

Effect of hydrogen embrittlement on the characteristics of copper-based shape memory alloy

Because of the good shape memory effect and superelasticity, copper-based shape memory alloys (SMAs) with aluminum and beryllium as binary and ternary elements are widely used in many applications (Cu-Al-Be SMAs). However, they are prone to corrosion in atmospheric conditions. This alloy is susceptible to corrosion due to hydrogen. This affects the characterization of the SMAs by absorbing the hydrogen and results in hydrogen embrittlement, makes changes in SME and SE effect. The process of hydrogen absorption was carried out under electrolytic charging under constant current density and the charged specimens were aged in the air at room temperature. The results show the decrement in SME from 99.8 % to 62%, and the tensile test revealed an increment in the transformation stress level from 200MPa- 290MPa in the case of the charged specimen.

Effects of Temperature and Applied Potential on the Stress Corrosion Cracking of X80 Steel in a Xinzhou Simulated Soil Solution.

In this research, the stress corrosion cracking (SCC) behavior of X80 pipeline steel in a Xinzhou soil environment at different temperatures and applied potentials was studied with a slow strain rate test (SSRT), potentiodynamic polarization curve measurements, and scanning electron microscopy (SEM). When a higher anodic potential was applied, anodic dissolution occurred at the crack tip and on the crack wall. The cracking mechanism of X80 steel in Xinzhou soil solution is anodic dissolution (AD). At positive cathodic potentials, X80 steel is under an anodic polarization state at the crack tip and under a cathodic polarization state at the crack wall. The SCC of X80 steel is affected by the combined effects of anodic dissolution (AD) and hydrogen embrittlement (HE). At more negative cathodic potentials, both crack tips and crack walls are under cathodic polarization. The SCC of X80 steel is dominated by hydrogen embrittlement (HE). SCC susceptibility has the same variation trend with potentials at different temperatures. The susceptibility to SCC increases notably as the temperature increases at weak cathodic potentials and open circuit potential due to the effect of temperature on the corrosion potential and the diffusion of atoms.

Study on fracture evaluation in hydrogen environment in 316L stainless steel used in high pressure hydrogen tank

In today’s growing pollution, hydrogen fuel vehicles are an important alternative to electric vehicles. For Type-4 Hydrogen Tank, a steel boss is normally used for valve mounting. The process of hydrogen embrittlement on steel plays a detrimental role. So, studies on the effect of hydrogen embrittlement on the threaded part of 316L stainless steel boss required for fastening of the valve for the 70 MPa compressed H2 tank have been carried out. For analysis, HEDE mechanism and Paris-Erdogan Law are used. For different values of initial crack length, the critical crack lengths are obtained for a particular loading cycle. The same calculation is repeated for different loading cycles. The analysis result shows that the critical crack length increases with the number of loading cycles. The critical crack length is higher 2% to 4% if the effect of hydrogen embrittlement is taken into account. So, for high pressure hydrogen tanks it is essential to consider the effect of hydrogen embrittlement.

Safety margin on the ductile to brittle transition temperature after hydrogen embrittlement on X65 steel

Hydrogen embrittlement is a phenomenon that affects the mechanical properties of steels intended for hydrogen transportation. One affected by this embrittlement is the Ductile to Brittle Transition Temperature (DBTT), which characterizes the change in the failure mode of the steel from ductile to brittle. This temperature is conventionally defined and compared to the operating temperature as an acceptability criterion for codes. Transition temperature does not depend only on the material, but also on specimen geometry particularly the thickness. Generally, the transition temperature is defined for the conservative reason by Charpy impact test. Standard Charpy specimens are straight beams with a thickness of 10 mm. For thin pipes, it is impossible to extract these standard specimens. One uses in this case Mini-Charpy specimens with a reduced thickness due to pipe curvature. This paper aims to quantify the effect of hydrogen embrittlement on the transition temperature of pipe steel (API 5L X65) using two types of Charpy specimens.

Hydrogen Stress Cracking Resistance and Hydrogen Transport Properties of ASTM A508 Grade 4N

Low alloy steels combine relatively low cost with exceptional mechanical properties, making them commonplace in oil and gas equipment. However, their strength and hardness are restricted for sour environments to prevent different forms of hydrogen embrittlement. Materials used in sour services are regulated by the ISO 15156-2 standard, which imposes a maximum hardness of 250 HV (22 HRC) and allows up to 1.0 wt% Ni additions due to hydrogen embrittlement concerns. Low alloy steels that exceed the ISO 15156-2 limit have to be qualified for service, lowering their commercial appeal. As a result, high-performing, usually high-nickel, low alloy steels used successfully in other industries are rarely considered for sour service. In this work, the hydrogen stress cracking resistance of the high-nickel (3.41 wt%), quenched and tempered, nuclear-grade ASTM A508 Gr.4N low alloy steel was investigated using slow strain rate testing as a function of applied cathodic potential. Results showed that the yield strength and ultimate tensile strength were unaffected by hydrogen, even at a high negative potential of −2.00 VAg/AgCl. Hydrogen embrittlement effects were observed once the material started necking, manifested by a loss in ductility with increasing applied cathodic potentials. Indeed, A508 Gr.4N was less affected by hydrogen at high cathodic potentials than a low-strength (yield strength = 340 MPa) ferritic-pearlitic low alloy steel of similar nickel content. Additionally, hydrogen diffusivity was measured using the hydrogen permeation test. The calculated hydrogen diffusion coefficient of the ASTM A508 Gr.4N was two orders of magnitude smaller when compared to that of ferritic-pearlitic steels. Hydrogen embrittlement and diffusion results were linked to the microstructure features. The microstructure consisted of a bainitic/martensitic matrix with the presence of Cr23C6 carbides as well as Mo- and V-rich precipitates, which might have played a role in retarding hydrogen diffusion, kept responsible for the improved HE resistance.

Zinc Coatings for High-Strength Low Alloy Steels: Comparison of Microstructure and Hydrogen Embrittlement During Heat Treatment

In this paper, the effect of hydrogen embrittlement in High-strength low-alloy steel (HSLA) material was studied. HSLA steels are known for their susceptibility to hydrogen induced failure especially when subjected to hydrogen rich environment. In this research, samples from HSLAS were surface-treated using chemical vapor deposition (CVD) techniques, followed by direct Zinc coating using physical vapor deposition (PVD). Other samples were additionally post-heat treated at a temperature of 260∘C for 4[Formula: see text]h to optimize the coating process. The hydrogen embrittlement test was performed by immersing the tensile samples in a solution containing H2SO4diluted with water for 24[Formula: see text]h. Hardness, and mechanical properties were evaluated using tensile testing. XRD and SEM were used for microstructural and topographical features’ examination of the treated samples. The results indicate that the samples of combined [Formula: see text] coating that was backed at 260∘C show superior resistance to hydrogen embrittlement compared to other conditions. This could be attributed to the buildup of a strong outer layer that prevents hydrogen from diffusing towards the base HSLAS material. The greater mechanical properties are possibly due to the reduction of hydrogen amount generated by the surface reaction associated by the formation of Zn(N[Formula: see text] phase and the reduction of hydrogen amount passed through Zn and C3N4layers.

Combined effect of hydrogen embrittlement and corrosion on the cracking behaviour of C110 low alloy steel in O2-contaminated H2S environment

The cracking behavior of sulfide stress cracking resistant C110 steel in O2-contaminated H2S environment was investigated by cracking and corrosion simulation tests. With the increase of O2 partial pressure, the cracking susceptibility and corrosion rate of C110 steel significantly increased. The O2 ingress affects the whole cracking behaviour involving a multi-stage process: the oxidation reactions of H2S, the corrosion reactions on the metal surface and the degradation and cracking of martensitic multiscale boundaries. The cracking mechanism of C110 steel in H2S and O2-containing environment is attributed to the combined effect of hydrogen embrittlement and anodic dissolution.

Stress Corrosion Cracking of Additively Manufactured Alloy 625.

Laser bed powder fusion (LPBF) is an additive manufacturing technology for the fabrication of semi-finished components directly from computer-aided design modelling, through melting and consolidation, layer upon layer, of a metallic powder, with a laser source. This manufacturing technique is particularly indicated for poor machinable alloys, such as Alloy 625. However, the unique microstructure generated could modify the resistance of the alloy to environment assisted cracking. The aim of this work was to analyze the stress corrosion cracking (SCC) and hydrogen embrittlement resistance behavior of Alloy 625 obtained by LPBF, both in as-built condition and after a standard heat treatment (grade 1). U-bend testing performed in boiling magnesium chloride at 155 and 170 °C confirmed the immunity of the alloy to SCC. However, slow strain rate tests in simulated ocean water on cathodically polarized specimens highlighted the possibility of the occurrence of hydrogen embrittlement in a specific range of strain rate and cathodic polarization. The very fine grain size and dislocation density of the thermally untreated specimens appeared to increase the hydrogen diffusion and embrittlement effect on pre-charged specimens that were deformed at the high strain rate. Conversely, heat treatment appeared to mitigate hydrogen embrittlement at high strain rates, however at the slow strain rate all the specimens showed a similar behavior.

Investigation on the SCC behavior of ZL101A aluminum alloy in simulated marine environments

Stress corrosion cracking (SCC) behavior of ZL101A aluminum alloy in solution and thin electrolyte layer (TEL) with different pH was investigated in detail. The results indicated that the precipitated phases of ZL101A were composed of α-Al/Si eutectic crystal phase and Si–Mg–Fe precipitated phase, which accelerated the formation of corrosion pits. ZL101A presented the highest SCC susceptibility in pH = 4 solution compared with pH = 7 and 10 solutions, which was mainly attributed to the enhanced synergistic effect of anodic dissolution, stress and hydrogen embrittlement. The basically similar SCC susceptibilities in TEL environments were mainly controlled by the anodic dissolution, which was attributed to the high diffusion rate of O2 in the thin electrolyte film.