Hydrogen Compatibility Research Articles

Safe pipelines for hydrogen transport

The hydrogen compatibility of two X65 pipeline steels for transport of hydrogen gas is investigated through microstructural characterization, hydrogen permeation measurements and fracture mechanical testing. The investigated materials are a quenched and tempered pipeline steel with a fine-grained homogeneously distributed ferrite-bainite microstructure, and hot rolled pipeline steel with a ferrite-pearlite banded microstructure. All tests are performed both under electrochemical and gaseous hydrogen charging conditions. A correlation between electrochemical hydrogen charging and gaseous charging is determined. The results point to inherent differences in the interaction between hydrogen and the two material microstructures. Further research is needed to unveil the influence of material microstructure on hydrogen embrittlement.

Determination of hydrogen compatibility for Cu-Al-Ni-Fe-Mn cast alloys prepared by varying Al and Ni contents

Hydrogen compatibility of Cu-Al-Ni-Fe-Mn cast alloys was investigated via slow strain rate tensile tests in high-pressure hydrogen gas. Four types of alloys were prepared by varying the Al and/or Ni contents. Larger Al and Ni contents resulted in more elongated microstructures with smaller grains and more precipitates, respectively. The tensile strength of the alloys increased with larger Al and/or Ni contents, whereas the ductility decreased only by adding a larger amount of Al. The maximum tensile strength was produced by adding larger amounts of both Al and Ni, which was fairly higher than those of stable austenitic stainless steels. Despite the difference in the microstructures and tensile strengths of the alloys, the hydrogen contents and hydrogen diffusivities showed no substantial difference. Additionally, their reduction in area measured after the tensile tests was not degraded by the high-pressure hydrogen gas, revealing an excellent resistance to hydrogen embrittlement.

Study on the Influence of Hydrogen Blended Transportation on the Safety of Existing X70 Steel in Gas Distribution Pipeline Network

Coal to gas is one of the natural gas sources utilized in Beijing, with a hydrogen blend concentration range from 1% to 3% and reaching up to 5% in specific cases. In order to evaluate the safety of transporting hydrogen blended natural gas with X70 pipeline steel in distribution pipelines, this study first conducted the slow strain rate tensile tests under a total pressure of 4 MPa in hydrogen environment. The results show that X70 steel exhibits highly sensitive to a hydrogen blending ratio of 5%. Subsequently, four types of hydrogen compatibility tests were conducted in the above sensitive hydrogen partial pressure include the impact toughness test, fracture toughness test, fatigue crack growth test, and fastening disk pressure test. The findings demonstrated that hydrogen blended natural gas has virtual no effect on the impact and fracture toughness, with only 10% reduction in fatigue crack growth threshold. Finally, based on fatigue life analysis by fracture mechanics evaluation, it can be concluded that the existing natural gas pipe of X70 steel is capable to operate safely over 40 years under a total pressure of 4 MPa with a hydrogen blend concentration of 5%.

Hydrogen embrittlement behaviors during SSRT tests in gaseous hydrogen for cold-worked type 316 austenitic stainless steel and iron-based superalloy A286 used in hydrogen refueling station

To consider an appropriate evaluation method for hydrogen compatibility, slow strain rate tensile (SSRT) tests were conducted on high strength piping materials, cold-worked type 316 austenitic stainless steel (SUS316CW) and iron-based superalloy A286, used in hydrogen stations for two years.SUS316CW, used at room temperature in 82 MPa gaseous hydrogen, contained 7.8 mass ppm hydrogen. The SSRT test of SUS316CW was conducted in nitrogen at −40 °C. The fracture surface showed dimples, and no hydrogen embrittlement behavior was observed. While, the SSRT test of SUS316CW in 70 MPa gaseous hydrogen at −40 °C showed a slight decrease in reduction area and a brittle fracture morphology in the outer layer. This was considered to be the effect of high-pressure gaseous hydrogen during the SSRT test in addition to the pre-contained hydrogen.A286, used at −40 °C in 82 MPa gaseous hydrogen, contained negligible hydrogen (0.14 mass ppm). SSRT tests were conducted at 150 °C in 70 MPa gaseous hydrogen and in air, and showed a low relative reduction in area (RRA) value. To investigate the decrease in the RRA, we switched the gas from hydrogen to air in the middle of the SSRT test and closely examined the RRA values and fracture morphology including side cracks. The hydrogen embrittlement was found to originate from the elastic deformation region. Stress cycling in the elastic deformation region also accelerated the effect of hydrogen. These were attributed to an increase in the lattice hydrogen content. While in the plastic deformation region, hydrogen trapped in the defects and hydrogen through the generated surface cracks increased the hydrogen content at the crack tips, reducing the RRA value. And there was a good correlation between the crack lengths and RRA values.Then, hydrogen embrittlement mechanism depends on the operating conditions (stress and temperature) of the material, and evaluating the hydrogen compatibility of materials by controlling their hydrogen content and strain according to the service environment is desirable.

Failure probability analysis of hydrogen doped pipelines based on the Bayesian network

Damage from hydrogen, such as hydrogen embrittlement in natural gas pipelines, is a possibility. There are currently lacking ways for calculating the failure of hydrogen doped pipelines quantitatively; instead, research on the safety of them is mostly concentrated on hydrogen compatibility tests and consequence analysis. A method for quantifying hydrogen doped pipelines losses using Bayesian network-based failure probability analysis is presented. The influence of hydrogen on pipeline failure is introduced using the expert scoring method based on the analysis of historical failure data for gas pipelines. The failure probabilities of various components of hydrogen doped pipelines are then quantified by combining fuzzy mathematical theory and hierarchical analysis, which is subsequently utilized as prior probabilities to input into the Bayesian network for quantitative calculation. The results show that the Bayesian network can more accurately quantify the failure probability of hydrogen doped pipelines. They also show that the Bayesian network can provide a practical approach for quantitative risk assessment and safety evaluation, as well as a decision basis for the prevention of hydrogen doping pipeline failure accidents.

A comparative analysis of the regulations, codes and standards for on-board high-pressure hydrogen storage cylinders

Hydrogen storage cylinder is an important component in high-pressure gaseous hydrogen (HPGH2) storage system, and plays a key role in hydrogen-powered transportation including land vehicles, ships and aircrafts. Over the past decade, the number of hydrogen fuel cell vehicles (HFCVs) has rapidly increased worldwide. In order to promote the application of hydrogen storage cylinder, guide its design, manufacture, inspection and testing, a series of regulations, codes and standards have been issued. The Chinese national standard, GB/T 42612, for type IV hydrogen storage cylinders has also been issued. This paper first gives a brief overview to these regulations, codes and standards. Furthermore, the specifications including scope, category, filling cycles, service life, materials, design, manufacture, qualification tests and periodic inspections are analyzed and compared. Issues about evaluation method for hydrogen compatibility of non-metallic materials, welded joints of plastic liner, joint between boss and liner are also discussed. Notably, the performance requirements in GB/T 42612 are generally in accordance with the international ones, but the requirements of materials, design and manufacture are more detailed.

Fabrication and volume loading studies for Mo30W matrix surrogate cermets

Ceramic-metallic composite (cermet) fuel forms are promising options for use in nuclear thermal propulsion (NTP) due to their high melting point, inherent hydrogen compatibility, retained strength at high temperatures, and high thermal conductivity. Spark plasma sintering was used to fabricate cermet materials, resulting in improved microstructural characteristics. An alloy of molybdenum with 30 wt% tungsten was used as the matrix material. Spherical yttria stabilized zirconia (YSZ) and both spherical and angular hafnium nitride (HfN) were used as surrogate fuel particles for the cermets. Utilizing a new lab-scale particle coating method, high density composites with excellent particle-matrix interfaces were fabricated. The effects of volume loading on the microstructure of the matrix were also examined, testing particle loadings up to 90 vol%. Initial stage sintering models were applied to understand the effects of the added particles on the sintering of the Mo30W matrix. Recommendations for fabrication of uranium bearing cermets using Mo30W are also included.

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.

Technological Support for Evaluation of Hydrogen Compatibility of Materials in Laboratory Conditions

Materials selection for hydrogen service is needed to support the deployment of hydrogen as a fuel as well as the development of codes and standards for stationary hydrogen use, hydrogen vehicles, refueling stations, and hydrogen transportation. Hydrogen energy infrastructure is currently in the process of development and in preparation for mass transportation of hydrogen gas and methane-hydrogen media involves significant use of the existing network of gas pipelines and formation of a network of hydrogen pipelines. Materials property measurement is needed on deformation, fracture and fatigue in hydrogen-containing media. Determination of steel properties such as strength, crack and fatigue resistance are priority to ensure safe design of pipelines transporting hydrogen gas or methane-hydrogen mixture. At the same time, there is a problem in technological support for evaluation of hydrogen compatibility of materials in laboratory conditions for evaluation of hydrogen embrittlement, depending on hydrogen concentration, methods and modes of loading, temperature, pressure and actual properties of materials.

Physical Modeling of Steel Resistance to Hydrogen Embrittlement

Hydrogen can be used in the same energy processes as natural gas and become a tool for implementing the transition to a sustainable low-carbon economy. The level of contamination resulting from controlled combustion of hydrogen or methane-hydrogen mixture is relatively low, which will significantly reduce CO2 emissions. However, the use of hydrogen can involve considerable difficulties associated with the hydrogen compatibility of materials. With the increase in the production, storage and transportation of hydrogen gas, including through gas pipelines, hydrogen-resistant materials are needed. The main problem with hydrogen is its embrittling effect. Under the influence of hydrogen, pipelines materials can probably have the following: hydrogen charging of the surface layer under pressure, loss of plasticity at tensile loads, formation of cracks and blisters (by decogesia mechanism), diffusion to the stress concentrator according to adsorption theory, accumulation of hydrogen at the top of the crack (which can lead to cracking) and so on. To assess the possibility of using a pipeline system for transportation of hydrogen gas in large volumes, it is necessary to know hydrogen compatibility of pipe steel. Physical modeling of steel resistance to hydrogen embrittlement can be carried out using electrochemical and gas charging methods.

Super-Grignard reagents (R2Mg·LiCl) mediated covalent-anionic-radical polymerization capable of low Đ and reactive hydrogen compatibility

The precise synthesis of polymer with narrow molecular weight distribution (Đ) and well-defined architectures is very essential to exploring the functions and properties of polymer materials. Here, a universal polymerization method capable of low Đ and reactive hydrogen compatibility is reported by introducing super-Grignard reagents (R2Mg·LiCl) into polymer chemistry. Under mild conditions, various monomers, including nonpolar polystyrene and 4-methoxystyrene that cannot be initiated by Grignard reagents, and polar methacrylate, are successfully polymerized with full monomer conversion and low Đ. This approach is amenable to wide varieties of initiators, polymerization temperature, and feed ratio, which makes it attractive for applications in polymer synthesis. By adding methanol and water during the polymerization process, the reactive hydrogen compatibility of this method is confirmed, which makes this method avoid the rigorous restriction on polymerization conditions of anionic polymerization. Moreover, chain extension polymerization and block copolymerization are achieved and demonstrate the livingness of chain propagation, enabling the facile synthesis of well-defined macromolecular architectures. This work therefore expands the methodology libraries of living polymerization, which may cause inspirations to polymer science.

Turbo-Grignard Reagent Mediated Polymerization of Styrene under Mild Conditions Capable of Low Đ and Reactive Hydrogen Compatibility

Turbo-Grignard Reagent Mediated Polymerization of Styrene under Mild Conditions Capable of Low <i>Đ</i> and Reactive Hydrogen Compatibility

Synthesis, thermal conductivity, and hydrogen compatibility of a high melt point solid solution uranium carbide, (U0.2Zr0.8)C

Uranium-zirconium carbides, (U,Zr)C, have been previously considered for nuclear thermal propulsion (NTP) reactors due to their high melting point, low neutron cross section, and good hydrogen compatibility. Fuel in NTP reactors would operate under extreme environments: high temperatures (∼3000 K) and under H2 exposure. Despite (U,Zr)C fuels showing promise for extreme environment operation, very little is known about their thermal conductivity as a function of temperature and their H2 compatibility at temperatures over 2500 K. In this work, phase pure UyZr1-yCz with y = 0.1, 0.2, 0.3 and z = 0.8, 0.85, 0.93 was synthesized and high density (U0.2Zr0.8)C samples were fabricated via spark plasma sintering. The thermal diffusivity, specific heat, and thermal expansion of (U0.2Zr0.8)C were measured, from which the thermal conductivity up to 1473 K was calculated for the first time. Furthermore, (U0.2Zr0.8)C samples with different geometries were exposed to H2 at 2600 K for 3 h using the compact fuel element environmental test facility at NASA Marshall Space Flight Center. Both samples performed remarkably well under hot hydrogen attack and no macroscopic cracking was identified. The combination of the relatively high thermal conductivity of these fuels, compared to UO2 for example, which increases with temperature, and their remarkable hydrogen compatibility make them excellent candidates for NTP reactors.

Hydrogen Compatibility of Polymers for Fuel Cell Vehicles

Hydrogen Compatibility of Polymers for Fuel Cell Vehicles

Slip transmission and voiding during slip band Intersections in Fe70Ni10Cr20 stainless steel

Slip blockage during slip band intersections impacts mechanical properties of crystalline materials. Molecular dynamics simulations of eight band intersections in Fe70Ni10Cr20 alloys revealed that secondary bands always transmit into ε bands more easily than into twin bands. While this is surprising because the ε-phase has a different crystal structure from the matrix, our finding that twins do not possess easy crystallographic pathways for transmission explains this phenomenon. We also found that the band intersection regions preferentially nucleate voids. These findings provide understanding of the deformation and damage behavior of FCC metals. For example, since hydrogen promotes ε-bands, our findings can help understand hydrogen compatibility.

Hydrogen Compatibility of Polymers for Fuel Cell Vehicles

So far, hydrogen compatibility of polymer materials was investigated, focusing on gaining insight in general degradation mechanisms. However, this is not yet sufficient for purposes of safety and performance requirements, for example, in the automotive industry and especially, the corresponding advanced material development, which needs meaningful and comprehensive data for prospective long time intervals. Therefore, herein, the applicability of forced aging regimes and the suitability of different analytical techniques for clarification of the underlying mechanisms are focused on. The study analyzes the behavior of polyether ether ketone, (thermoplastic) polyurethane and fluoroelastomer materials after prolonged aging in hydrogen atmosphere under pressure as it occurs in hydrogen fuel‐cell vehicles. Material changes are investigated by electron microscopy, thermogravimetry, differential scanning calorimetry, and gas sorption measurements. Especially thermogravimetry turns out to indicate subtle material changes that are important indications for material choice.

An experimental study for qualifying hydrogen compatibility of austenitic stainless steel under low temperature

An experimental study for qualifying hydrogen compatibility of austenitic stainless steel under low temperature

Electrochemical Study on Hydrogen Entry Initiationin SSRT of Low Alloy Steel in High-Pressure Hydrogen Gas

The application of concurrent cathodic hydrogen charging SSRT is being investigated as an alternative to SSRT in high-pressure hydrogen gas, which is used to evaluate the hydrogen compatibility of metallic materials. There are some differences in the stress-displacement behavior and the fracture surface between the two tests. These differences can be attributed to the difference in the timing of the onset of hydrogen entry in the two environments. In SSRT of low-alloy steel in high-pressure hydrogen gas, the amount of absorbed hydrogen up to the yield stress is small and increases rapidly after plastic deformation, Whereas, since in concurrent cathodic hydrogen charging, hydrogen entry is initiated as soon as begins, it is necessary to determine an apporopriate start time. The surface changes of SCM435 specimens during SSRT in NaOH solution were analyzed by electrochemical measurements, and the breakdown of the oxide film that inhibits hydrogen entry during SSRT in high-pressure hydrogen gas was discussed. As a result, the impedance at low frequencies decreased immediately after the yield point, which was attributed to the decrease in the reaction resistance of the oxide film. The rest potential decreased immediately after the yield point and immediately after the fracture, which were attributed to the exposure of the fresh surface due to the breakdown of the oxide film. From these results, it was clear that hydrogen charging in the concurrent cathodic hydrogen charging SSRT should be started just after the yield point.

Differences between internal and external hydrogen effects on slow strain rate tensile test of iron-based superalloy A286

To investigate the evaluation method of hydrogen compatibility of A286 superalloy in high pressure hydrogen gas, SSRT tests of hydrogen-charged specimens were conducted at ambient temperature at various strain rates. The relative reduction in area (RRA), one of the ductility parameters, was determined. The hydrogen content in the hydrogen-charged specimen was the same as the equilibrium hydrogen content on the specimen surface at 150 °C in 70 MPa hydrogen gas. The strain rate dependence of RRA was smaller than that of RRA obtained in 70 MPa hydrogen gas at 150 °C. All the hydrogen-charged specimens showed slip-plane fractures in the grains in their cores. However, the specimens in 70 MPa hydrogen gas at 150 °C showed fracture surfaces morphology ranging from dimples to quasi-cleavages and intergranular fractures with decreasing strain rate. These dissimilarities are expected to arise from differences in the hydrogen concentration behaviors of the specimens during the deformation process.

Test Method to Establish Hydrogen Compatibility of Materials in High Pressure Hydrogen Gas Environments for Fuel Cell Vehicles

Test Method to Establish Hydrogen Compatibility of Materials in High Pressure Hydrogen Gas Environments for Fuel Cell Vehicles