Transmission, Distribution & Storage
Influence of Thermal Treatment on SCC and HE Susceptibility of Supermartensitic Stainless Steel 16Cr5NiMo
Apr 2020
Publication
A 16Cr5NiMo supermartensitic stainless steel was subjected to different tempering treatments and analyzed by means of permeation tests and slow strain rate tests to investigate the effect of different amounts of retained austenite on its hydrogen embrittlement susceptibility. The 16Cr5NiMo steel class is characterized by a very low carbon content. It is the new variant of 13Cr4Ni. These steels are used in many applications for example compressors for sour environments offshore piping naval propellers aircraft components and subsea applications. The typical microstructure is a soft-tempered martensite very close to a body-centered cubic with a retained austenite fraction and limited δ ferrite phase. Supermartensitic stainless steels have high mechanical properties together with good weldability and corrosion resistance. The amount of retained austenite is useful to increase low temperature toughness and stress corrosion cracking resistance. Experimental techniques allowed us to evaluate diffusion coefficients and the mechanical behaviour of metals in stress corrosion cracking (SCC) conditions.
Effect of Hot Mill Scale on Hydrogen Embrittlement of High Strength Steels for Pre-Stressed Concrete Structures
Mar 2018
Publication
The presence of a conductive layers of hot-formed oxide on the surface of bars for pre or post-compressing structures can promote localized attacks as a function of pH. The aggressive local environment in the occluded cells inside localized attacks has as consequence the possibility of initiation of stress corrosion cracking. In this paper the stress corrosion cracking behavior of high strength steels proposed for tendons was studied by means of Constant Load (CL) tests and Slow Strain Rate (SSR) tests. Critical ranges of pH for cracking were verified. The promoting role of localized attack was confirmed. Further electrochemical tests were performed on bars in as received surface conditions in order to evaluate pitting initiation. The adverse effect of mill scale was recognized.
The Effect of Hydrogen on the Nanoindentation Behavior of Heat Treated 718 Alloy
Oct 2020
Publication
In this study the effect of precipitates on the surface mechanical properties in the presence of hydrogen (H) is investigated by in situ electrochemical nanoindentation. The nickel superalloy 718 is subjected to three different heat treatments leading to different sizes of the precipitates: (i) solution annealing (SA) to eliminate all precipitates (ii) the as-received (AR) sample with fine dispersed precipitates and (iii) the over-aged (OA) specimen with coarser precipitates. The nanoindentation is performed using a conical tip and a new method of reverse imaging is employed to calculate the nano-hardness. The results show that the hardness of the SA sample is significantly affected by H diffusion. However it could be recovered by removing the H from its matrix by applying an anodic potential. Since the precipitates in the OA and AR samples are different they are influenced by H differently. The hardness increase for the OA sample is more significant in −1200mV while for the AR specimen the H is more effective in −1500mV. In addition the pop-in load is reduced when the samples are exposed to cathodic charging and it cannot be fully recovered by switching to an anodic potential.
Investigation of Mechanical Tests for Hydrogen Embrittlement in Automotive PHS Steels
Aug 2019
Publication
The problem of hydrogen embrittlement in ultra-high-strength steels is well known. In this study slow strain rate four-point bending and permeation tests were performed with the aim of characterizing innovative materials with an ultimate tensile strength higher than 1000 MPa. Hydrogen uptake in the case of automotive components can take place in many phases of the manufacturing process: during hot stamping due to the presence of moisture in the furnace atmosphere high-temperature dissociation giving rise to atomic hydrogen or also during electrochemical treatments such as cataphoresis. Moreover possible corrosive phenomena could be a source of hydrogen during an automobile’s life. This series of tests was performed here in order to characterize two press-hardened steels (PHS)—USIBOR 1500® and USIBOR 2000®—to establish a correlation between ultimate mechanical properties and critical hydrogen concentration.
Research of Nanomaterials as Electrodes for Electrochemical Energy Storage
Jan 2022
Publication
This paper has experimentally proved that hydrogen accumulates in large quantities in metal-ceramic and pocket electrodes of alkaline batteries during their operation. Hydrogen accumulates in the electrodes in an atomic form. After the release of hydrogen from the electrodes a powerful exothermic reaction of atomic hydrogen recombination with a large energy release occurs. This exothermic reaction is the cause of thermal runaway in alkaline batteries. For the KSL-15 battery the gravimetric capacity of sintered nickel matrix of the oxide-nickel electrode as hydrogen storage is 20.2 wt% and cadmium electrode is 11.5 wt%. The stored energy density in the metal-ceramic matrix of the oxide-nickel electrode of the battery KSL-15 is 44 kJ/g and in the cadmium electrode it is 25 kJ/g. The similar values for the KPL-14 battery are as follows. The gravimetric capacity of the active substance of the pocket oxide-nickel electrode as a hydrogen storage is 22 wt% and the cadmium electrode is 16.9 wt%. The density of the stored energy in the active substance oxide-nickel electrode is 48 kJ/g and in the active substance of the cadmium electrode it is 36.8 kJ/g. The obtained results of the accumulation of hydrogen energy in the electrodes by the electrochemical method are three times higher than any previously obtained results using the traditional thermochemical method.
Linking Ab Initio Data on Hydrogen and Carbon in Steel to Statistical and Continuum Descriptions
Mar 2018
Publication
We present a selection of scale transfer approaches from the electronic to the continuum regime for topics relevant to hydrogen embrittlement. With a focus on grain boundary related hydrogen embrittlement we discuss the scale transfer for the dependence of the carbon solution behavior in steel on elastic effects and the hydrogen solution in austenitic bulk regions depending on Al content. We introduce an approximative scheme to estimate grain boundary energies for varying carbon and hydrogen population. We employ this approach for a discussion of the suppressing influence of Al on the substitution of carbon with hydrogen at grain boundaries which is an assumed mechanism for grain boundary hydrogen embrittlement. Finally we discuss the dependence of hydride formation on the grain boundary stiffness
Hydrogen Effects in Non-ferrous Alloys: Discussion
Jun 2017
Publication
This is a transcript of the discussion session on the effects of hydrogen in the non-ferrous alloys of zirconium and titanium which are anisotropic hydride-forming metals. The four talks focus on the hydrogen embrittlement mechanisms that affect zirconium and titanium components which are respectively used in the nuclear and aerospace industries. Two specific mechanisms are delayed hydride cracking and stress corrosion cracking.
This article is a transcription of the recorded discussion of the session ‘Hydrogen in non-ferrous alloys’ at the Royal Society Discussion Meeting Challenges of Hydrogen in Metals 16–18 January 2017. The text is approved by the contributors. M.P. transcribed the session. M.A.S. assisted in the preparation of the manuscript.
Link to document download on Royal Society Website
This article is a transcription of the recorded discussion of the session ‘Hydrogen in non-ferrous alloys’ at the Royal Society Discussion Meeting Challenges of Hydrogen in Metals 16–18 January 2017. The text is approved by the contributors. M.P. transcribed the session. M.A.S. assisted in the preparation of the manuscript.
Link to document download on Royal Society Website
Hydrogen Diffusion Mechanism around a Crack Tip in Type 304L Austenite Stainless Steel Considering the Influence of the Volume Expansion of Strain-Induced Martensite Transformation
Sep 2019
Publication
Strain-induced martensite transformation (SIMT) commonly exists around a crack tip of metastable austenite stainless steels. The influence of the volume expansion of the SIMT on the hydrogen diffusion was investigated by hydrogen diffusion modelling around a crack tip in type 304L austenite stainless steel. The volume expansion changed the tensile stress state into pressure stress state at the crack tip resulting in a large stress gradient along the crack propagation direction. Compared to the analysis without considering the volume expansion effect this volume expansion further accelerated the hydrogen transport from the inner surface to a critical region ahead of the crack tip and further increased the maximum value of the hydrogen concentration at the critical position where the strain-induced martensite fraction approximates to 0.1 indicating that the volume expansion of the SIMT further increased the hydrogen embrittlement susceptibility.
Experimental Investigation of the Effect of Hydrogen on Fracture Toughness of 2.25Cr-1Mo-0.25V Steel and Welds after Annealing
Mar 2018
Publication
Hydrogen embrittlement (HE) is a critical issue that hinders the reliability of hydrogenation reactors. Hence it is of great significance to investigate the effect of hydrogen on fracture toughness of 2.25Cr-1Mo-0.25V steel and weld. In this work the fracture behavior of 2.25Cr-1Mo-0.25V steel and welds was studied by three-point bending tests under hydrogen-free and hydrogen-charged conditions. The immersion charging method was employed to pre-charge hydrogen inside specimen and the fracture toughness of these joints was evaluated quantitatively. The microstructure and grain size of the specimens were observed by scanning electron microscopy (SEM) and by metallurgical microscopy to investigate the HE mechanisms. It was found that fracture toughness for both the base metal (BM) and the weld zone (WZ) significantly decreased under hydrogen-charged conditions due to the coexistence of the hydrogen-enhanced decohesion (HEDE) and hydrogen-enhanced localized plasticity (HELP) mechanisms. Moreover the formation and growth of primary voids were observed in the BM leading to a superior fracture toughness. In addition the BM compared to the WZ shows superior resistance to HE because the finer grain size in the BM leads to a larger grain boundary area thus distributing more of the diffusive hydrogen trapped in the grain boundary and reducing the hydrogen content.
Large-scale Compressed Hydrogen Storage as Part of Renewable Electricity Storage Systems
Mar 2021
Publication
Storing energy in the form of hydrogen is a promising green alternative. Thus there is a high interest to analyze the status quo of the different storage options. This paper focuses on the large-scale compressed hydrogen storage options with respect to three categories: storage vessels geological storage and other underground storage alternatives. In this study we investigated a wide variety of compressed hydrogen storage technologies discussing in fair detail their theory of operation potential and challenges. The analysis confirms that a techno-economic chain analysis is required to evaluate the viability of one storage option over another for a case by case. Some of the discussed technologies are immature; however this does not rule out these technologies; rather it portrays the research opportunities in the field and the foreseen potential of these technologies. Furthermore we see that hydrogen would have a significant role in balancing intermittent renewable electricity production.
A Panoramic Analysis of Hydrogen Utilization Systems Using an Input-output Table for Next Generation Energy Systems
Apr 2017
Publication
The objective of this study is to analyze a government proposal from a panoramic perspective concerning the economic and environmental effects associated with the construction and operation of hydrogen utilization systems by the year 2030. We focused on a marine transport system for hydrogen produced offshore hydrogen gas turbine power generation fuel cell vehicles (FCVs) and hydrogen stations as well as residential fuel cell systems (RFCs). In this study using an Input-Output Table for Next Generation Energy Systems (IONGES) we evaluated the induced output labor and CO2 emissions from the construction and operation of these hydrogen technologies using a uniform approach. This may be helpful when considering future designs for the Japanese energy system. In terms of per 1 t-H2 of hydrogen use CO2 reductions from the use of FCVs are considerably higher than the additional CO2 emissions from foreign production and transportation of hydrogen. Because new construction of a hydrogen pipeline network is not considered to be realistic RFCs is assumed to consume hydrogen generated by refining town gas. In this case the CO2 reductions from using RFCs will decline under the electricity composition estimated for 2030 on the condition of a substantial expansion of electricity generation from renewable energy sources. However under the present composition of electricity production we can expect a certain amount of CO2 reductions from using RFCs. If hydrogen is directly supplied to RFCs CO2 reductions increase substantially. Thus we can reduce a significant amount of CO2 emissions if various unused energy sources dispersed around local areas or unharnessed renewable energies such as solar and wind power can be converted into hydrogen to be supplied to FCVs and RFCs.
Impact of Depth on Underground Hydrogen Storage Operations in Deep Aquifers
Mar 2024
Publication
Underground hydrogen storage in geological structures is considered appropriate for storing large amounts of hydrogen. Using the geological Konary structure in the deep saline aquifers an analysis of the influence of depth on hydrogen storage was carried out. Hydrogen injection and withdrawal modeling was performed using TOUGH2 software assuming different structure depths. Changes in the relevant parameters for the operation of an underground hydrogen storage facility including the amount of H2 injected in the initial filling period cushion gas working gas and average amount of extracted water are presented. The results showed that increasing the depth to approximately 1500 m positively affects hydrogen storage (flow rate of injected hydrogen total capacity and working gas). Below this depth the trend was reversed. The cushion gas-to-working gas ratio did not significantly change with increasing depth. Its magnitude depends on the length of the initial hydrogen filling period. An increase in the depth of hydrogen storage is associated with a greater amount of extracted water. Increasing the duration of the initial hydrogen filling period will reduce the water production but increase the cushion gas volume.
Location-dependent Effect of Nickel on Hydrogen Dissociation and Diffusion on Mg (0001) Surface: Insights into Hydrogen Storage Material Design
Apr 2021
Publication
Density functional theory (DFT) calculations have been performed to investigate the hydrogen dissociation and diffusion on Mg (0001) surface with Ni incorporating at various locations. The results show that Ni atom is preferentially located inside Mg matrix rather than in/over the topmost surface. Further calculations reveal that Ni atom locating in/over the topmost Mg (0001) surface exhibits excellent catalytic effect on hydrogen dissociation with an energy barrier of less than 0.05 eV. In these cases the rate-limiting step has been converted from hydrogen dissociation to surface diffusion. In contrast Ni doping inside Mg bulk not only does little help to hydrogen dissociation but also exhibits detrimental effect on hydrogen diffusion. Therefore it is crucial to stabilize the Ni atom on the surface or in the topmost layer of Mg (0001) surface to maintain its catalytic effect. For all the case of Ni-incorporated Mg (0001) surfaces the hydrogen atom prefers firstly immigrate along the surface and then penetrate into the bulk. It is expected that the theoretical findings in the present study could offer fundamental guidance to future designing on efficient Mg-based hydrogen storage materials.
HyUnder – Hydrogen Underground Storage at Large Scale: Case Study Spain
Aug 2015
Publication
Hydrogen as an energy carrier is understood as a system capable of storing energy for a later use in a controlled manner. Surplus electricity from renewable energy serves for green hydrogen generation via electrolysis. Once produced the hydrogen is stored for later consumption. This paper describes the Spanish Case Study of the HyUnder project which aims to evaluate the potential of underground hydrogen storage for large-scale energy storage along Europe analysing besides the Spanish Case France Germany the Netherlands Romania and the United Kingdom. This case study has considered for the assessment the competitiveness of hydrogen storage against other large scale energy storage concepts the geological potential for hydrogen storage in the region how to embed the hydrogen energy storage in the energy market and the possible business cases in four different applications: transport Power to Gas re-electrification and industry taking into account all the economic aspects such us the electrolyser OPEX and CAPEX or the cavern electricity and water costs. It is shown that the Spanish geology can provide four technical options for hydrogen underground storage. Results have shown the interest of the technology in short – medium term especially linked to certain conditions of high intermittent renewable energy penetration in the Spanish power grid that result in surplus or residual electricity. Hydrogen storage is interesting because it can integrate renewable energy systems in other sectors which do not have overcapacity and a high use of fossil fuels as the natural gas sector and the transport sector. Moreover all the economic issues have been analysed for two different horizons 2025 and 2050; concluding that the average price of electricity is the main cost. From the financial results transport application represents a business case which although in order has enough values of hydrogen demand to be stored combination of different applications must be needed in order to make sense to the development of the cavern.
Hydrogen Storage in Pure and Boron-Substituted Nanoporous Carbons—Numerical and Experimental Perspective
Aug 2021
Publication
Nanoporous carbons remain the most promising candidates for effective hydrogen storage by physisorption in currently foreseen hydrogen-based scenarios of the world’s energy future. An optimal sorbent meeting the current technological requirement has not been developed yet. Here we first review the storage limitations of currently available nanoporous carbons then we discuss possible ways to improve their storage performance. We focus on two fundamental parameters determining the storage (the surface accessible for adsorption and hydrogen adsorption energy). We define numerically the values nanoporous carbons have to show to satisfy mobile application requirements at pressures lower than 120 bar. Possible necessary modifications of the topology and chemical compositions of carbon nanostructures are proposed and discussed. We indicate that pore wall fragmentation (nano-size graphene scaffolds) is a partial solution only and chemical modifications of the carbon pore walls are required. The positive effects (and their limits) of the carbon substitutions by B and Be atoms are described. The experimental ‘proof of concept’ of the proposed strategies is also presented. We show that boron substituted nanoporous carbons prepared by a simple arc-discharge technique show a hydrogen adsorption energy twice as high as their pure carbon analogs. These preliminary results justify the continuation of the joint experimental and numerical research effort in this field.
Graphene Oxide/metal Nanocrystal Multilaminates as the Atomic Limit for Safe and Selective Hydrogen Storage
Mar 2016
Publication
Interest in hydrogen fuel is growing for automotive applications; however safe dense solid-state hydrogen storage remains a formidable scientific challenge. Metal hydrides offer ample storage capacity and do not require cryogens or exceedingly high pressures for operation. However hydrides have largely been abandoned because of oxidative instability and sluggish kinetics. We report a new environmentally stable hydrogen storage material constructed of Mg nanocrystals encapsulated by atomically thin and gas-selective reduced graphene oxide (rGO) sheets. This material protected from oxygen and moisture by the rGO layers exhibits exceptionally dense hydrogen storage (6.5 wt% and 0.105 kg H2 per litre in the total composite). As rGO is atomically thin this approach minimizes inactive mass in the composite while also providing a kinetic enhancement to hydrogen sorption performance. These multilaminates of rGO-Mg are able to deliver exceptionally dense hydrogen storage and provide a material platform for harnessing the attributes of sensitive nanomaterials in demanding environments.
Tetrahydroborates: Development and Potential as Hydrogen Storage Medium
Oct 2017
Publication
The use of fossil fuels as an energy supply becomes increasingly problematic from the point of view of both environmental emissions and energy sustainability. As an alternative hydrogen is widely regarded as a key element for a potential energy solution. However differently from fossil fuels such as oil gas and coal the production of hydrogen requires energy. Alternative and intermittent renewable energy sources such as solar power wind power etc. present multiple advantages for the production of hydrogen. On the one hand the renewable sources contribute to a remarkable reduction of pollutants released to the air and on the other hand they significantly enhance the sustainability of energy supply. In addition the storage of energy in form of hydrogen has a huge potential to balance an effective and synergetic utilization of renewable energy sources. In this regard hydrogen storage technology is a key technology towards the practical application of hydrogen as “energy carrier”. Among the methods available to store hydrogen solid-state storage is the most attractive alternative from both the safety and the volumetric energy density points of view. Because of their appealing hydrogen content complex hydrides and complex hydride-based systems have attracted considerable attention as potential energy vectors for mobile and stationary applications. In this review the progresses made over the last century on the synthesis and development of tetrahydroborates and tetrahydroborate-based systems for hydrogen storage purposes are summarized.
Evaluation of Hydrogen-induced Cracking in High-strength Steel Welded Joints by Acoustic Emission Technique
Feb 2020
Publication
Hydrogen-induced cracking behavior in high-strength steel mainly composed of martensite was analyzed by acoustic emission (AE) technique and finite element method (FEM) in slow strain-rate tensile (SSRT) tests and welding tests. The crack initiation was detected by the AE signals and the time evolution of stress concentration and hydrogen diffusion were calculated by FEM. The effect of hardness and plastic strain on the hydrogen diffusion coefficientwas explicitly introduced into the governing equation in FEM. The criterion and indicator parameter for the crack initiation were derived as a function of maximum principal stress and locally accumulated hydrogen concentration. The results showed that the cracking criterion derived by AE and FEM is useful for predicting the cold cracking behavior and determining the critical preheat temperature to prevent hydrogeninduced cracking.
Effect of the Strain Rate on the Fracture Behaviour of High Pressure Pre-Charged Samples
Dec 2018
Publication
The aim of this work is to study the effect of the displacement rate on the hydrogen embrittlement of two different structural steels grades used in energetic applications. With this purpose samples were pre-charged with gaseous hydrogen at 19.5 MPa and 450 °C for 21 h. Then fracture tests of the pre-charged specimens were performed using different displacement rates. It is showed that the lower is the displacement rate and the largest is the steel strength the strongest is the reduction of the fracture toughness due to the presence of internal hydrogen.
Molecular Dynamics Studies of Hydrogen Effect on Intergranular Fracture in α-Iron
Nov 2020
Publication
In the current study the effect of hydrogen atoms on the intergranular failure of α-iron is examined by a molecular dynamics (MD) simulation. The effect of hydrogen embrittlement on the grain boundary (GB) is investigated by diffusing hydrogen atoms into the grain boundaries using a bicrystal body-centered cubic (BCC) model and then deforming the model with a uniaxial tension. The Debye Waller factors are applied to illustrate the volume change of GBs and the simulation results suggest that the trapped hydrogen atoms in GBs can therefore increase the excess volume of GBs thus enhancing intergranular failure. When a constant displacement loading is applied to the bicrystal model the increased strain energy can barely be released via dislocation emission when H is present. The hydrogen pinning effect occurs in the current dislocation slip system <111>{112}. The hydrogen atoms facilitate cracking via a decrease of the free surface energy and enhance the phase transition via an increase in the local pressure. Hence the failure mechanism is prone to intergranular failure so as to release excessive pressure and energy near GBs. This study provides a mechanistic framework of intergranular failure and a theoretical model is then developed to predict the intergranular cracking rate
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