High-pressure Hydrogen Environment Research Articles

Development of a regulator for high-pressure hydrogen charging and storage system

Hydrogen emerges as a promising alternative energy source, particularly in fuel cell applications, necessitating efficient and safe charging and storage systems. This paper presents the design and development of a specialized regulator tailored for high-pressure hydrogen environments. Focusing on precision control, the regulator ensures optimal performance and safety during charging and storage phases. In order to improve the unstable response characteristics of the existing commercial hydrogen regulator, which has the same differential pressure generation site and pressure control site, a regulator operating at an ultra-high pressure of 105 MPa was designed by separating the differential pressure site and the control site. And structural safety and performance of the regulator were predicted through structural and flow analysis. The results of structural and flow analysis of a 105 MPa high-pressure regulator that can be used for high-pressure hydrogen charging and storage systems were compared with the experimentally measured values.

An in-situ view cell system for investigating swelling behavior of elastomers upon high-pressure hydrogen exposure

The transition to hydrogen as a clean and efficient energy carrier is impeded by challenges in the compatibility of hydrogen with materials used within hydrogen infrastructure. Elastomers, crucial in sealing components, often exhibit premature failures in high-pressure hydrogen environments due to excessive swelling. This study employs an innovative in-situ view cell system to assess the swelling behavior of hydrogenated nitrile butadiene rubber (HNBR) under various hydrogen conditions. The system, designed to withstand pressures up to 96.5 MPa, incorporates Digital Image Correlation (DIC) for strain measurements and volume estimation. Results reveal non-linear volume increases during depressurization, challenging conventional assumptions. Furthermore, investigations into peak hydrogen pressures and pressure-holding scenarios during decompression highlight complex swelling trends. The introduction of a novel computer vision (CV) method enhances precision in volume estimation, overcoming DIC limitations. The study provides insights into mitigating elastomer swelling, crucial for developing robust materials to support future hydrogen-driven energy systems.

The Impact of Impurity Gases on the Hydrogen Embrittlement Behavior of Pipeline Steel in High-Pressure H2 Environments.

The use of hydrogen-blended natural gas presents an efficacious pathway toward the rapid, large-scale implementation of hydrogen energy, with pipeline transportation being the principal method of conveyance. However, pipeline materials are susceptible to hydrogen embrittlement in high-pressure hydrogen environments. Natural gas contains various impurity gases that can either exacerbate or mitigate sensitivity to hydrogen embrittlement. In this study, we analyzed the mechanisms through which multiple impurity gases could affect the hydrogen embrittlement behavior of pipeline steel. We examined the effects of O2 and CO2 on the hydrogen embrittlement behavior of L360 pipeline steel through a series of fatigue crack growth tests conducted in various environments. We analyzed the fracture surfaces and assessed the fracture mechanisms involved. We discovered that CO2 promoted the hydrogen embrittlement of the material, whereas O2 inhibited it. O2 mitigated the enhancing effect of CO2 when both gases were mixed with hydrogen. As the fatigue crack growth rate increased, the influence of impurity gases on the hydrogen embrittlement of the material diminished.

Experimental and numerical study on high-cycle fatigue performance of austenitic stainless steel with pre-charged hydrogen

High-cycle fatigue performance is one of the crucial issues for hydrogen diaphragm compressors, as hydrogen embrittlement affects the components in a high pressure hydrogen environment. In this study, the high-cycle fatigue response of MP7, a novel material of austenitic stainless steel designed for hydrogen diaphragm compressors, is investigated by tests and by numerical ways using the Crystal Plasticity Finite Element Method (CPFEM). The uniaxial tensile tests and fatigue tests are carried out on MP7 specimens with different levels of pre-charged hydrogen. The analysis indicates that, even for MP7 with the improved hydrogen resistance performance, both the ductility and the fatigue limit are still affected by the pre-charged hydrogen in a considerable way. Based on the principles of crystal plasticity theory, a CPFEM model is established and a fatigue life prediction model for austenitic stainless steel with pre-charged hydrogen is proposed. This model successfully predicts the fatigue life under different hydrogen contents and stress amplitudes, and the predicted fatigue lives are well-fitted to S-N curves within a two-fold error band.

Effect of Hydrogen Pressure and Punch Velocity on the Hydrogen Embrittlement Susceptibility of Pipeline Steels Using Small Punch Tests under Gaseous Hydrogen Environments at Room Temperature

The in situ small punch (SP) test method is a simple screening technology developed to assess the hydrogen embrittlement (HE) characteristics of structural steels. This method can easily adjust the influencing parameters such as test temperature, gas pressure, and punch velocity depending on the hydrogen service environment. With increased hydrogen consumption, using pipelines for mass hydrogen transportation is being considered. This study evaluated the HE susceptibility of API-X52 and API-X70 steels, considering the hydrogen usage environment. The study investigated the effects of hydrogen pressure and punch velocity on the HE behaviors of each pipe steel at room temperature using the SP energy and relative reduction in thickness (RRT) to determine their effect on HE susceptibility quantitatively. The study found that hydrogen pressure produced a different HE effect; the lower the hydrogen pressure, the more HE was relieved. Particularly, when the punch velocity was high, such as 1 mm/min, the HE effect was significantly relaxed. However, when the punch velocity was below 0.01 mm/min, HE occurred even at low hydrogen pressure conditions, meaning hydrogen diffusion within the specimen during the SP testing reached a critical hydrogen concentration to create a brittle fracture. Both pipeline steels showed similar HE behaviors under a wide range of H2 pressures and punch velocities, showing an inverse S-curve for quantitative factors of SP energy and RRT against the H2 pressure at 1.0 mm/min punch velocity. The study classified the observed HE behaviors into four types based on quantitative and qualitative aspects. These findings confirm that the in situ SP test is a useful screening technique, and the factor RRT can be effectively applied to the HE screening of pipeline steels in low and high-pressure hydrogen environments.

Hydrogen Embrittlement Characteristics of Tempered Martensitic Steels under Electrochemical and High-Pressure Hydrogen Environments

The effect of hydrogen charging methods on the hydrogen embrittlement characteristics of tempered martensitic steels were discussed in terms of hydrogen diffusion behavior. Two tempered martensitic steels with different Si content were fabricated by quenching and tempering. The steel with high Si content had a lower cementite fraction because the addition of Si changed the morphology of cementite from a long film-like shape to a short-rod shape by suppressing the precipitation and growth of the cementite. To evaluate the hydrogen embrittlement resistance of the two tempered martensitic steels with different Si content, slow strain-rate tensile testing was employed after introducing hydrogen using three types of hydrogen charging methods (ex-situ electrochemical hydrogen charging, in-situ electrochemical hydrogen charging, and in-situ high-pressure gaseous hydrogen environment). For the hydrogen pre-charged tensile specimens using the ex-situ electrochemical charging method, the steel with high Si content had a better hydrogen embrittlement resistance, with a higher relative reduction in area. On the other hand, there was no significant difference in the relative notch tensile strength of the two tempered martensitic steels with different Si content, regardless of the hydrogen charging methods. In addition, the ex-situ hydrogen charging method exhibited higher relative notch tensile strength compared to the in-situ hydrogen charging method due to the release of hydrogen during the tensile test, after exsitu hydrogen charging. This implies that hydrogen embrittlement resistance can be differently estimated depending on the kind of hydrogen charging methods.

Effects of Cr, Mn, and Fe on the hydrogen solubility of Ni in high-pressure hydrogen environments and their electronic origins: An experimental and first-principles study

Effect of the addition of Cr, Mn, or Fe to Ni on the material's hydrogen solubility are investigated to establish guidelines for designing materials authorized to use in high-pressure hydrogen environments. The exposure to 100 MPa hydrogen gas at 160 °C reveals that the addition of 30 wt%Fe to Ni decreases the hydrogen solubility by 40%, while the addition of 20 wt%Cr to Ni increases it by 65%. Surprisingly, incorporating 20 wt%Mn causes a remarkable increase of 992%. By employing a combined approach of a random alloy model based on the special quasi-random structure and first-principles calculations, we are able to semi-quantitatively predict the effects of these alloying elements on hydrogen solubility. Moreover, the deconvolution of hydrogen bonding energy into its volumetric, mechanical, and chemical components clarifies that the significant impact of Mn is primarily attributed to a substantial expansion of the lattice constant.

Designing functionalized graphene-stitched-SiC/fluoropolymer novel composite coating with excellent corrosion resistance and hydrogen diffusion barrier properties

The investigation on ordinary hydrogen barrier composite coatings has been limited in terms of corrosion and high-pressure hydrogen environments, which significantly restricts its practical and industrial applications. Herein, a unique nanohybrid two-dimensional (2D) filler, constituting poly-dopamine (PDA) functionalized graphene (Gr) nanosheets and covalently bridged silicon carbide (SiC) nanoflakes assisted by 3-Isocyanatopropyltrimethoxysilane (IPTMS) via hydrolysis reaction, was innovatively proposed and incorporated into fluoroethylene vinyl ether resin (FEVE) to fabricate final composite coating by spin-coating technique. The hydrogen gas barrier and long-term anti-corrosion performances could be simultaneously enhanced by precisely collaborative effects of interfacial interactions fortification among Gr, SiC, and polymer phase as well as centrifugal force promoted Gr orientation during the spinning process. The optimum sample demonstrated high |Z|0.01Hz values of 3.1 × 1011 Ω cm2 and 3.37 × 1011 Ω cm2 throughout 90 d saltwater immersion and 6-day 1.5 MPa pressurized hydrogen environment exposure respectively. Moreover, its permeability coefficient decreased by 75.66% compared to the pure sample. Other significant properties including 30d constant salt-spray attack tolerance and high adhesion strength of 12.46 MPa were also achieved to meet industrial demands. This work provided paramount inspiration for designing composite coatings for hydrogen transportation pipeline protection and hydrogen energy usage.

Different augmentations of absorbed hydrogen under elastic straining in high-pressure gaseous hydrogen environment by as-quenched and as-tempered martensitic steels: combined experimental and simulation study

Hydrogen embrittlement (HE) behavior of as-quenched and as-tempered martensitic steels under elastic straining in a high-pressure gaseous hydrogen environment was studied for the first time. The difference in the total content of defects acting as H trap sites has the highest contribution to the increase in absorbed hydrogen content under the elastic loading. The hydrogen-induced fracture occurred in the as-quenched specimen during elastic straining in hydrogen environment, while the tempered specimen did not fracture under the elastic loading. Higher accumulation of the dislocations near the main crack initiation sites (prior austenite grain boundaries (PAGBs)) in the as-quenched specimen will be the main source of the hydrogen to the potential flaw to crack to initiate. H accumulated near PAGBs enhances dislocation slip along {011} planes and helps transgranular crack propagation. Due to less possibility to provide the critical local amount of hydrogen at PAGBs for the crack to initiate, the as-tempered specimen remained unfractured.

Mechanical and Rotating Bending Fatigue Properties of 18Cr-4.8Ni-0.03C Stainless Steel in High-Pressure Hydrogen Environment

The mechanical and fatigue properties of 18Cr-4.8Ni-0.03C stainless steel were measured under high-pressure gaseous hydrogen. Slow-strain-rate tensile (SSRT) tests were carried out at temperatures of 228 K, 293 K, and 363 K under 105 MPa high-pressure gaseous hydrogen and 0.1 MPa nitrogen. The relative tensile strength was 0.98 or higher at all temperatures, confirming that this steel has good hydrogen compatibility. Rotating bending fatigue tests were carried out at room temperature under 88 MPa high-pressure gaseous hydrogen and air. Fatigue limits were found in both types of atmosphere. No deterioration of the fatigue limit was observed in the specimen tested under 88 MPa high-pressure gaseous hydrogen. Surface cracks were observed in the parallel part of the rotating bending fatigue test specimen that was unbroken at 107 cycles in both types of atmosphere.

Dependence of the mechanical properties of a metastable austenitic stainless steel in high-pressure hydrogen gas on machining-induced defects

The susceptibility of metastable 304L to embrittlement in a high-pressure gaseous hydrogen environment was studied from the viewpoint of changes in mechanical properties. The high pressure hydrogen gas leads to deterioration of mechanical properties, which may be accelerated by the presence of surface defects. The tensile specimens were cut with different machining parameters to change the density of the different defects caused by the machining. The maximum dislocation density caused by machining, rather than the maximum strain-induced martensite increased the sensitivity to hydrogen embrittlement.

Effect of high-pressure hydrogen environment in elastic and plastic deformation regions on slow strain rate tensile tests for iron-based superalloy A286

To investigate the effects of a high-pressure hydrogen environment in the elastic and plastic deformation regions, we performed slow strain-rate tensile tests of iron-based superalloy A286 at 150 °C by switching the atmosphere from 70 MPa hydrogen to air during the tests. The relationship between the nominal strain exposed to a hydrogen environment and the relative reduction in area (RRA) revealed that in the plastic deformation region, the RRA value decreased gradually depending on the nominal strain exposed to hydrogen, but in the elastic deformation region, the RRA value decreased rapidly. The RRA value further decreased when the stress cycle was applid in the elastic region. The fracture surface exhibited an intragranular slip plane fracture similar to that of the hydrogen-charged specimen. These phenomena suggest that the lattice decohesion theory is dominant in the elastic region, where hydrogen embrittlement occurs owing to an increase in the content of dissolved hydrogen.

Overview of hydrogen-resistant alloys for high-pressure hydrogen environment: on the hydrogen energy structural materials

Abstract With the progressive expansion of hydrogen fuel demand, hydrogen pipelines, hydrogen storage cylinders and hydrogen refuelling stations (HRSs) are the primary components of hydrogen energy systems that face high-pressure hydrogen environments. Hydrogen embrittlement (HE) is a typical phenomenon in metallic materials, particularly in the high-pressure hydrogen environment, that causes loss of ductility and potentially catastrophic failure. HE is associated with materials, the service environment and stress. The primary mechanisms for explaining the HE of materials are hydrogen-enhanced decohesion, hydrogen-induced phase transformation, hydrogen-enhanced local plasticity, adsorption-induced dislocation emission and hydrogen-enhanced strain-induced vacancy. To reduce the risk of HE for metallic structural materials used in hydrogen energy systems, it is crucial to reasonably select hydrogen-resistant materials for high-pressure hydrogen environments. This paper summarizes HE phenomena, mechanisms and current problems for the metallic structural materials of hydrogen energy systems. A research perspective is also proposed, mainly focusing on metal structural materials for hydrogen pipelines, hydrogen storage cylinders and hydrogen compressors in HRSs from an application perspective.

Effect of manganese content on the hydrogen embrittlement of twinning-induced plasticity (TWIP) steels under hydrogen charging and hydrogen environment

The hydrogen embrittlement behavior of two stabilized austenitic twinning-induced plasticity (TWIP) steels under high-pressure thermal hydrogen charging and hydrogen environment were investigated by slow strain rate tensile and fatigue crack growth tests. The results show that the two TWIP steels with Mn content (16% and 25%) do not produce strain-induced martensite after deformation, but both show a certain susceptibility to hydrogen embrittlement after hydrogen charging, in which the TWIP steel with higher Mn content shows weaker hydrogen embrittlement. This is mainly due to the high hydrogen embrittlement susceptibility of deformation twins. In the H2 environment, compared with slow strain rate tensile tests, fatigue crack growth tests is more likely to reflect the hydrogen embrittlement susceptibility of the TWIP steel, and the hydrogen environment is more likely to promote the crack growth of the TWIP steel with lower Mn content. This is related to the inter-granular cracking of TWIP steel with low Mn content under H2 environment. The increase of Mn content reduces the hydrogen diffusion coefficient and hydrogen solubility of TWIP steel, which is also one of the reasons for the weak hydrogen embrittlement of TWIP steel with high Mn content in hydrogen charging and hydrogen environment.

A Study of Hydrogen Embrittlement of SA-372 J Class High Pressure Hydrogen Storage Seamless Cylinder (≥100 MPA).

The spinning process will lead to changes in the micro-structure and mechanical properties of the materials in different positions of the high-pressure hydrogen storage cylinder, which will show different hydrogen embrittlement resistance in the high-pressure hydrogen environment. In order to fully study the safety of hydrogen storage in large-volume seamless steel cylinders, this chapter associates the influence of the forming process with the deterioration of a high-pressure hydrogen cylinder (≥100 MPa). The anti-hydrogen embrittlement of SA-372 grade J steel at different locations of the formed cylinders was studied experimentally in three cylinders. The hydrogen embrittlement experiments were carried out according to method A of ISO 11114-4:2005. The relationship between tensile strength, microstructure, and hydrogen embrittlement is analyzed, which provides comprehensive and reliable data for the safety of hydrogen storage and transmission.

Predictive environmental hydrogen embrittlement on fracture toughness of commercial ferritic steels with hydrogen-modified fracture strain model

In this work, a practical numerical model with few parameters was proposed for the prediction of environmental hydrogen embrittlement. The proposed method adopts hydrogen enhanced plasticity-based mechanism in a fracture strain model to describe hydrogen embrittlement. Fracture toughness degradation of three commercial steels SA372J70, AISI4130 and X80 in high pressure hydrogen environment were investigated. Firstly, governing equations for hydrogen distribution and material damage evolution was established. Hydrogen enhanced localized flow softening effect was coupled within fracture strain dependency on stress triaxiality. Then, the numerical implementation and identification process of model parameters was described. Model parameters of the investigated steels were determined based on experiment results from literatures. Finally, with the calibrated model, fracture toughness reduction of the steels was predicted in a wide range of hydrogen pressure. The prediction results were compared with experimental results. Reasonable accuracy was reached. The proposed method is an attempt to reach balance between physical accurate prediction and engineering practicality. It is promising to provide a simplified numerical tool for the design and fit for service evaluation of hydrogen storage vessels. • Hydrogen embrittlement prediction model with few parameters was proposed. • Identification of model parameters with a few support of experiments. • Simplified Fracture toughness prediction model with acceptable accuracy.

Effect of Functional Fillers on Tribological Characteristics of Acrylonitrile Butadiene Rubber after High-Pressure Hydrogen Exposures.

In a high-pressure hydrogen environment, the sealing rubber material is swelled by hydrogen, and the mechanical and tribological properties are reduced, causing various problems in the sealing performance. The focus of this study was the effect of the filler type and content on the tribological characteristics of rubber after exposure to high-pressure hydrogen. Acrylonitrile butadiene rubber specimens were exposed to high-pressure hydrogen at 96.6 MPa, and the change in the amount of wear with time after exposure was observed. The wear test was performed using a pin-on-disc ball tip to measure the amount of wear before and after hydrogen exposure of the materials under fixed revolutions per minute and normal load. Scanning electron microscopy was used to observe the wear track and cross section of the specimen to examine the changes in the wear mechanism after hydrogen exposure and to analyze the wear mechanism for each filler. The results of this study are expected to contribute to the evaluation of the tribological properties of the sealing materials used in hydrogen environments.

Influence of Specimen Surface Roughness on Hydrogen Embrittlement Induced in Austenitic Steels during In-Situ Small Punch Testing in High-Pressure Hydrogen Environments

An in-situ small punch (SP) test method has recently been developed as a simple screening technique for evaluating the properties of metallic materials used in high-pressure hydrogen environments. With this method, the test conditions including temperature and gas pressure can easily be adjusted to those used in practice. In this study, specimens of STS316L steel and 18 wt% Mn steel were prepared at two different surface roughness, fabricated using wire-cutting and mechanical polishing. Their effects on hydrogen embrittlement (HE) were evaluated using in-situ SP testing at both room temperature and a lower temperature where HE was shown to occur under 10 MPa hydrogen. Both steels were evaluated using two variables obtained from in-situ SP testing, the SP energy, and the relative reduction of thickness (RRT), to quantitatively determine the effect of specimen surface roughness on HE susceptibility. Their fracture characteristics due to HE under 10 MPa hydrogen showed little difference with surface finish. Surface roughness had a negligible influence on these quantitative factors describing HE, indicating that it is not a dominant factor to be considered in in-situ SP testing when it is used to screen for HE compatibility in steels used in high-pressure hydrogen environments.

Hydrogen embrittlement resistance of TWIP (twinning-induced plasticity) steel in high pressure hydrogen environment

The behavior of as-received and cold-rolled Fe–25Mn–10Ni–0.65C twinning-induced plasticity steel in hydrogen environment was investigated using fatigue crack growth rate tests. The results show that TWIP steel shows weak hydrogen embrittlement susceptibility, which is due to the formation of deformation twins at the crack tip without strain-induced martensite. Hydrogen can promote the formation of deformation twins and may accumulate in the twin beam, which causes fatigue cracks in TWIP steel to propagate along the twin and slip bands in hydrogen environment. Cold rolling can substantially improve the hydrogen embrittlement resistance and fatigue resistance of TWIP steel.

Quantitative evaluation of hydrogen embrittlement susceptibility in various steels for energy use using an in-situ small punch test

Recently, as hydrogen has been increasingly applied in the field of new energy, it has become necessary to evaluate the mechanical characteristics of hydrogen embrittlement (HE) when materials are used to reduce costs as well as ensure safety in hydrogen facilities. However, to obtain a large amount of data in a short period of time and ensure reliability when selecting materials used in hydrogen energy applications, a simple test method for screening the HE susceptibility of materials under high-pressure hydrogen environments should be established and applied. In this study, the HE behaviors of three structural steels to be used in the hydrogen energy field were examined at room temperature and low temperatures under high-pressure hydrogen environments using the newly established in-situ small punch test method. The effects of test temperature and punch velocity on the HE susceptibility of each steel were quantitatively evaluated using the characterizing factor, known as the relative reduction of thickness.