Hydrogen, the first and smallest element of the classification, is the source of damage in materials, most often by causing brittle fractures. Its high diffusivity in the atomic state and its instability are the cause. The processes of implementation and the conditions of use of materials must thus take into account the risk of contamination and sensitization related to the possible presence of hydrogen.
After a first series of conferences on hydrogen embrittlement in 2010 and 2016, which had a very good audience, the A3TS proposes, at the initiative of the Ile de France section, to take up this subject again by devoting 4 half-days to it successively addressing : Damage to metallic materials caused by hydrogen, Hydrogen and surface treatments seen both as problems and solutions, the problems of pressurized hydrogen, what questions to ask in the face of the production, transport and use of hydrogen in the systems of today and tomorrow.
The speakers, recognized specialists in the behavior of materials in the presence of hydrogen, will update and deepen the knowledge on this subject and answer the questions of the public concerned by the relations "products, environments, treatments and materials.
REGISTRATION AND INFORMATION
RATES
A3TS member: 290 € HT (348 € TTC)
Non-member: 345 € HT (414 € TTC)
Judicial expert: 150 € HT (180 € TTC)
Speaker 1 day: Offered
Speaker 2 days / student / retired: 100 € HT (120 € TTC)
Commercial space (composed of a table and two chairs): 500 € HT (600 € TTC)
WELCOME & RECEPTION
The reception and registration of participants will take place on Tuesday, October 4, 2022 at the A3TS reception from 8:30 am:
l'ASIEM
6 rue Albert de Lapparent
75007 PARIS
REGULATIONS
Payments must be made before the event by bank transfer or by card directly online below.
A certificate of participation will be sent upon receipt of the registration. A3TS reserves the right to refuse reimbursement of participation fees for cancellation requests made after September 25, 2022.
Your registration will take effect upon receipt of your payment.
abstracts of the presentations
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Hydrogen is an energy carrier that will play a major role in the energy transition, and in particular in the development of electrochemical devices such as fuel cells and electrolyzers, which will be particularly important, for example, in the transition from gasoline-powered cars to electric cars. Hydrogen is by far the most abundant element in the known universe; nevertheless, in almost all cases, it exists on Earth only in association with other atoms in more or less complex molecules. Hydrogen is therefore not a primary energy, and its use will therefore require extracting it from these molecules, making it interact with matter in electrochemical devices, storing it and transporting it. The interaction with matter will also require a certain level of knowledge in materials science. Through some questions that seem obvious, but are far from being so, about the origin of hydrogen, its absence on Earth as a molecule, its interaction with matter, and how to extract electrons from it, the presentation will briefly introduce some important aspects of this new hydrogen economy and related technologies.
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This presentation will be devoted to the description of two damage modes encountered in pressure equipment, whose common point is that they are related to the introduction of hydrogen in the material in contact with the environment. These are the cracking phenomena developing at temperatures close to ambient in a wet H2S environment, where hydrogen is introduced via corrosion reactions, and the attack of steels under hot hydrogen pressure, where hydrogen is introduced by dissociation of gaseous dihydrogen.
For each of these degradation modes, we will expose the industrial sectors concerned, the phenomena at stake, the types and morphology of defects encountered (HTHA, HIC, SSC...) and the factors that influence the appearance of damage (factors related to the materials used or the environment).
The non-destructive examinations that allow to search for these damages in the equipment will be briefly described.
Given the characteristics of these damages, particularly in terms of facies and dimensions, the examinations mostly deployed for their detection and characterization are based on the ultrasound method. This involves the use of techniques described as "advanced", such as multi-element ultrasound (with or without beam formation), and TOFD (Time Of Flight Diffraction). Their specific settings, depending on the type of damage sought, gives rise to the generation of ultrasound images whose exploitation allows to decide on its presence, its extension in the controlled component, and, as far as possible, on its level of severity.
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The phenomenon of hydrogen embrittlement (HE) of metallic materials is a major industrial issue in many sectors. In service, the sources of hydrogen are multiple, ranging from corrosion to cathodic protection, including the transport and storage of hydrogen gas under pressure. Thus, the knowledge of hydrogen entry and degradation mechanisms for each material according to external constraints (mechanical and environmental) is necessary in order to select the most suitable alloys for the service conditions and/or to implement strategies to avoid the risks of premature failure.
The external FPH passes a priori through a hydrogen entry step, potentially assisted by stress or plastic deformation. Hydrogen can then remain on the near surface or be redistributed in the microstructure and the stress and strain fields. It can then affect the mechanical or fatigue behavior of the material and facilitate the appearance of cracks. The propagation phase is generally strongly accelerated for most alloys tested under hydrogen loading.
The objective of this paper is to highlight the links and differences in the behavior of hydrogen in some classes of materials. This will be done first by more fundamental studies of hydrogen in alloys, in particular its diffusivity and solubility, two determining factors in the choice of methods for characterizing alloys. Then, the impact of hydrogen on the behavior of different alloys of stainless steel, nickel base and aluminum is looked at from the point of view of the conditions and quantities of hydrogen entering the material. These results are discussed with respect to the actual loading conditions in service.
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If additive manufacturing corresponds to processes that are very popular today, in particular laser fusion on powder bed, it remains that the microstructures inherited from these processes deserve to be studied closely because they differ, in some aspects, from the microstructures obtained by more conventional elaboration and shaping processes. The immediate consequence is that the study of the durability of parts manufactured by laser fusion on powder bed also reserves its share of surprises, good or bad. The example chosen here is that of 17-4PH martensitic stainless steel with structural hardening. In the H900 metallurgical state, it differs from steel produced by conventional metallurgy in that it has a significantly higher austenite reversion content. This results in a sensitivity to environmentally assisted cracking (EAC) different from that of conventional steel, and which, depending on the test conditions, can be linked to differences in terms of interactions with hydrogen (solubility, diffusion, hydrogen / dislocations interaction) and/or sensitivity to localized corrosion (passivation and pitting).
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In order to bring elements of understanding to the phenomenon of hydrogen embrittlement, we have been trying for several years and within the framework of numerous studies to evaluate the impact of the various metallurgical heterogeneities (grain boundaries, dislocations, precipitates, gaps...) on the processes of diffusion and trapping of hydrogen. This approach allows to question the implication of the interactions between these heterogeneities and hydrogen on the mechanical behaviors, and more particularly on the damage mechanisms assisted by hydrogen. This work has been conducted on various model and industrial materials such as nickel and its alloys, stainless steels and martensitic steels using experimental approaches (permeation, TDS, GD-OES, SKPFM...) with and without mechanical couplings, associated with multi-scale numerical approaches (atomistic calculations, finite elements...). Among the main results obtained, and depending on the material, we have identified a major role of hydrogen mobility and reversible trapping on plasticity (hardening and softening) and on the mechanisms of damage, initiation and crack propagation under hydrogen. On the other hand, we have also highlighted the implication of hydrogen-lacquer interactions in the modification of elastic properties. Finally, we have obtained some answers as to the role of the nature of the grain boundaries in the diffusion and trapping of hydrogen on the one hand and on the other hand on the mechanisms of fracture under hydrogen.
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Green or renewable energies appear as alternatives to mitigate climate change linked to the massive use of fossil fuels such as oil. It is in this context that the so-called clean hydrogen is currently attracting a lot of interest. The technological and economic mastery of this new hydrogen sector (production, conditioning - compression, storage, transport and use), as an energy vector, can contribute in a sustainable way to the energy transition of the next decades.
Mechanical engineering is a key supplier in this value chain as it is involved at all levels. It is known that hydrogen at high pressure can have a significant impact on materials and equipment. Understanding and controlling its influence on the behavior of these new systems will contribute to the strategic positioning of the industries involved. The HyMEET (Hydrogen Material and Equipment Engineering and Testing Center) project, led by CETIM, aims to help the sector's industrialists to meet this challenge by equipping themselves with test facilities for testing and validating materials under high hydrogen pressure. These new mechanical systems integrate tribological problems which are of great interest because they are decisive in the choice of materials.
The acquisition of the Plint TE-60 tribometer, capable of operating under hydrogen gas, will make it possible not only to reproduce the kinematic and tribological conditions of certain applications (injectors, hydrogen compressors, valves, pipes, O-rings, etc.) but also to test the interactions of materials under this environment. This tribometer, classified Atex, will be equipped with a system that will allow to control the pressure, the temperature of the chamber and the environment in which the tests will be performed. The three-station reciprocating tribometer, mounted in a high-pressure chamber (max. 80 bar) of one liter volume, is capable of operating simultaneously in ball/plane and plane/plane configurations. Tests can be performed with temperatures ranging from -55°C to 150°C. The maximum load, maximum frequency and maximum displacement are 50 N, 5 Hz and 20 mm, respectively. The device allows to follow in real time the evolution of the friction coefficient.
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With the decline of fossil fuels and the need to develop green energies to save the climate, hydrogen appears as one of the most promising energy sources in the near future. However, the development of H2 energy will require the construction of a complete industrial chain, including production plants, mainly through the development of efficient fuel cells or cracking processes, transport and storage, the production of safe vehicles and the development of H2 refueling station networks in the different European countries.
From a material qualification point of view, several questions arise since hydrogen can be absorbed by metallic materials with well known risks of embrittlement and premature failure if the service conditions are not controlled.
In a first approach to assess the risk of failure of pipeline materials, an X65 welded steel identified as possibly susceptible to hydrogen-assisted cracking was tested under 100 bar of hydrogen through a variety of experimental techniques (slow tensile, toughness, internal cracking, permeability, thermodesorption analyses...). The effect of degraded operating conditions was also evaluated (H2S contamination, presence of moisture...)
The paper presents a synthesis of the results. A specific point will also be made on the conditions of evaluation of the toughness and the inconsistencies which can exist in certain standards used to qualify materials for hydrogen service.
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The experimental study of hydrogen embrittlement (HE) requires the mobilization of many experimental techniques such as electrochemical permeation with and without stress, thermal desorption spectroscopy (TDS), GD-OES, SKPFM, mechanical tests and nano-indentation (monotonic or cyclic) under hydrogen.... The objectives of these techniques, which are qualitative, semi-quantitative or quantitative, are to evaluate the processes of hydrogen diffusion and trapping, to characterize the hydrogen states and to question the impact of the solute on the mechanical properties. However, many of these approaches require the implementation of very detailed and complex experimental protocols, moreover, the results obtained can be analyzed using theoretical models or simulation methods (e.g. finite elements) with boundary conditions whose validity may be questionable with respect to the test conditions, the nature of the material, and even the evolution of the hydrogen states and its interactions with metallurgical defects. The objective of this work is to propose a critical analysis by indicating the advantages and limitations of the main experimental techniques that are used to characterize and measure hydrogen in metallic materials. This approach will be the occasion to give a number of recommendations.
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The interaction between hydrogen and various metallic materials has been reported and discussed in the literature. It has been found that hydrogen significantly affects the mechanical properties. This small chemical element penetrates between the crystalline sites of the metal structure and reduces its ductility and service life [1].
Coatings present an excellent solution to protect such a material and give it multifunctional properties. Coatings are widely considered as a good solution for designing hydrogen barriers to trap adsorbed hydrogen and prevent its diffusion to the substrate.
The objective of our work is the development of new generations of hydrogen barrier coatings to protect metallic components used under hydrogen. After three years of work on this research project, we have successfully developed a new AlTiW thin film deposited by the magnetron sputtering technique [2].
The functional properties of the coating such as corrosion resistance and thermal stability as well as its protective performance for steels in a hydrogen environment were studied. The influence of tungsten content on the microstructure, thermal stability, mechanical properties, corrosion resistance and inhibition of hydrogen permeation in the coating was analyzed. XRD, DSC and TEM analyses were performed to verify the amorphous state of the coating and to determine the glass transition and crystallization temperatures.
Two chemical and electrochemical loading methods were used to expose the coated steels to hydrogen. The incorporation of tungsten into the AlTi binary coatings greatly improved their resistance to hydrogen absorption. The results obtained confirm that the addition of W improved the mechanical properties of the coating (hardness and Young's modulus) and the Al45Ti38W17 coating exhibited the best hydrogen barrier behavior.
Currently, we are working on improving the efficiency of the coatings and developing other nanostructured thin films for use in different conditions and real-world applications.
Key words : Barrier coatings, Thin films, Magnetron sputtering, Hydrogen embrittlement, Electrochemical and mechanical properties.
Acknowledgements : European Regional Development Fund (ERDF) and the Public Interest Group (GIP52).
References:
[1] A. Alhussein, J. Capelle, J. Gilgert, S. Dominiak, Z. Azari, Influence of Sandblasting and Hydrogen on Tensile and Fatigue Properties of Pipeline API 5L X52 Steel, Int J Hydrogen Energy 36 (2011) 2291.
[2] I. Lakdhar, A. Alhussein, J. Capelle, J. Creus, Al-Ti-W alloys deposited by magnetron sputtering: Effective barrier to prevent steel hydrogen embrittlement, Applied Surface Science 567 (2021) 150786.
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Hydrogen is emerging as one of the main energy carriers. One of the solutions envisaged for long distance transport is to circulate it diluted in city gas, in the existing network. The main problem with this solution is the embrittling effect of hydrogen on the steel pipes. The approach proposed in this study consists in the application of a physical barrier by the cold spray process, which has the function of preventing, or at least limiting, the penetration of hydrogen into the steels and thus avoiding their embrittlement.
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Prestressing tendons are crucial elements of prestressed concrete structures. They are vulnerable to corrosion, especially stress corrosion, as they are stressed up to 80% of their maximum breaking strength. This stress corrosion can lead in some cases to the failure of wires or entire strands, thus endangering the structure as well as the users. It is therefore important to know the damage mechanisms specific to these elements in order to predict their degradation kinetics and to implement preventive or even curative measures. Galvanization and cathodic protection of these cables are ways to limit their vulnerability to corrosion, even if certain precautions must be applied to avoid the opposite effect. Another innovative solution in prestressing is the use of stainless steel.
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To improve corrosion protection of steel, sacrificial coatings of electroplated zinc or zinc alloys can be applied. An integral part of a typical electroplating sequence is a pre-treatment step. During both electroplating and pre-treatment, developed atomic hydrogen is able to diffuse into the crystal lattice of a base material, what leads to unwanted hydrogen-induced embrittlement of coated parts. Especially, when high strength steel is used as a base material, a risk of reaching a critical hydrogen concentration is relatively high.
In order to minimize the risk of damage caused by hydrogen embrittlement, all critical process steps need to be carefully monitored. Here crucial are: the choice of a proper inhibitor for the pickling as well as selection of a suitable electrolyte together with optimal application parameters and an appropriate de-embrittlement sequence.
There are several methods to analyze the risk of hydrogen embrittlement in the electroplating process. The goal of this study was to apply a C-Ring technique, described in the DIN 50969 Part 2 standard, to identify factors having a major influence on hydrogen embrittlement in zinc and zinc alloy electroplating. Furthermore, suitable prevention strategies have been discussed.
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Often when a zinc plated screw breaks, showing an intergranular surface containing "spherical cavities", we tend to conclude that it is a problem of hydrogen embrittlement (FPH) and to look for the limit content that this coated part can store before becoming brittle...
This questioning is the first sign of a lack of knowledge of the phenomenon associated with the catastrophic sudden rupture that interests us. Indeed, the quantification of the total hydrogen content using a thermal desorption spectrometer (TDS) does not allow in any case to bring a relevant information to decide on the origin of the dispute.
To have a better idea of what can lead to a rupture by FPH, it will be interesting to ask other questions that we propose to develop during this presentation:
Do heat treatments in atmosphere induce FPH?
Why does the "degassing" treatment make the coated part less fragile?
Is the term "outgassing" really appropriate?
All these questions will allow us to introduce the concepts associated with the distribution of hydrogen and the evolution of this distribution during the various stages of the manufacturing process and the use of the coated product.
This approach associated with the impact of hydrogen on electrolytically coated parts can be extended to all the difficulties that steels working under hydrogen may encounter: stress corrosion, working in H2S environment, cold embrittlement during welding, corrosion phenomena (pitting, ...), difficulty related to a galvanic protection, working in pressurized hydrogen environment (fatigue, creep), ...
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The ingress of hydrogen into structural alloys, including high-strength steels, superalloys, and aluminum alloys causes premature and catastrophic failures, threatening their reliability and durability. For instance, high strength steels known for their crucial applications in aerospace and fastener industries as landing gears and high strength structural bolts, anchor rods etc. can suffer from premature failures due to hydrogen embrittlement (HE). However, understanding the hydrogen induced failure mechanism(s) is challenging because of the complex microstructure of these materials. However, understanding the hydrogen induced failure mechanism(s) of these materials is challenging, because their complex microstructure can significantly interfere with fracture and hydrogen diffusion process. The conventional test methodologies available to evaluate HE susceptibility are either significantly time consuming, or involve cost and complexities for set up. Therefore, a rapid fracture test in four-point bending is proposed to assess hydrogen embrittlement (HE) susceptibility of these materials. The novelty of this technique is the rapid rate of loading, whereas conventional approaches require prolonged slow strain rate testing. The essential fractographic features required to identify the mechanisms of HE failure remain evident, despite the fast loading conditions. To demonstrate these attributes, two cases were considered: (a) two quenched and tempered (Q & T) steels with similar strength levels having different steel chemistry, and (b) two Q & T steels with different strength levels having same steel chemistry, were tested with and without pre-charging of hydrogen (H). The test results show striking differences in HE susceptibility among the materials in both the cases. Microstructural characterization and assessment were performed primarily based on Transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Stress coupled hydrogen diffusion finite element analysis was also performed to calculate both stress and hydrogen concentration distributions. The study indicates that local plasticity and microstructure can have significant influences on hydrogen induced cracking, as compared to the global microstructure affecting hydrogen transport kinetics. The study also shows that the current approach is capable of quantifying HE susceptibility by being responsive to key factors affecting embrittlement, thus developing further understanding on the HE of martensitic steels.
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Zn-Fe alloys have been of particular interest in recent years in the field of corrosion protection due to changing environmental standards that impact certain metal salts [1-3]. According to the literature, increasing the iron content in the zinc alloy deposit is accompanied by a decrease in the faradic yield by promoting the hydrogen evolution reaction (HER) [4]. For some applications, it is necessary to be able to evaluate the impact of the hydrogen uptake evolution reaction on the properties of coated steels.
The Performa 226 process, patented by Coventya and the Utinam Institute, allows the production of Zn-Fe coatings with a corrosion resistance similar to that of current industrial references. Within the framework of the ATLAS project, led by the IRT M2P, work on the understanding, the control and the optimization of the global process has been carried out in order to meet the specifications of the industrial partners of the project. As such, a study on hydrogen embrittlement during the electrodeposition of a Zn-Fe deposit comprising 8 to 9% of iron has been conducted.
This study, carried out on a laboratory scale, then on an industrial scale, has made it possible to highlight the influence of surface preparation and degassing on the mechanical properties of a steel coated with Zn-Fe 8-9%. In this study, the quantitative determination of the light elements incoporated in the electrolytic deposit, in particular hydrogen, was carried out by hot extraction and then the impact on the mechanical properties of the steels coated by two different methods was evaluated. Thus, slow tensile tests were compared to embrittlement tests according to ASTM F519, all performed on notched specimens of AISI 4340 steel [5-6]. The results obtained by the two methods will be presented and discussed in relation to the observed fracture surfaces and the measured hydrogen contents.
[1]. S. Amirat, R. Rehamnia, M. Bordes, and J. Creus, 2013, Materials and Corrosion, 64, 328-334.
[2]. J. He, D. W. Li, F. He, Y. Liu, Y. Liu, C. Zhang, F. Ren, Y. Ye, X. Deng and D. Yin, 2020, Materials Science and Engineering, C117, 111295.
[3]. D. Rashmi, G. P. Pavithra, B. M. Praveen, D. Devapal, K. O. Nayana, and S. P. Hebbar, 2020, Jounal of Bio- and Tribo-Corrosion, 6, 84-92.
[4]. H. Nakano, S. Arakawa, S. Oue, and S. Kobayashi, 2015, Materials Transition, 56, 1664-1669.
[5]. J. Bellemare, S. Laliberté-Riverin, D. Ménard, M. Brochu and F. Sirois, 2020, Metallurgical and Materials Transactions A, 51, 3054-3065.
[6]. T. Das, S. V. Brahimi, J. Song, and S. Yue, 2021, Corrosion Science, 190, 109701.
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The development of the hydrogen sector is part of the decarbonization process and the objectives set by the States in the short and medium term as an alternative to fossil fuels.
The extended use of this molecule in multiple applications leads to new problems of material selection due to its size, explosive character and diffusivity. Indeed, the latter is one of the main characteristics of hydrogen, which distinguishes it from other fluids with respect to the causes of damage. Although the diffusivity of hydrogen varies considerably depending on the material and the temperature, it is nevertheless always several orders of magnitude higher than the diffusivities of other species. Therefore, the widespread occurrence of hydrogen damage is directly related to the ease of hydrogen absorption in metals and the high mobility of hydrogen in them.
All metallic materials present a certain degree of sensitivity to hydrogen which will depend on its chemical composition, microstructure, heat treatment, mechanical resistance, etc. Thus, multidisciplinary knowledge of coupled phenomena is necessary to understand the phenomenon of hydrogen embrittlement (HE). The definition of the average representative characteristics of the material (grain size, grain boundaries, precipitates, dislocation density...), as well as the different states of hydrogen (trapped and diffusible hydrogen) are essential when evaluating the FPH. Other parameters such as the stress and strain state of the part in the hydrogen environment are also essential.
We will examine the problem of degradation of metals exposed to hydrogen gas through fatigue, slow tensile strength tests (SSRT) and fracture mechanics (K1C, K1H). These tests are part of the mechanical tests used for the qualification of materials in a high pressure hydrogen environment. Fundamental aspects of HPF such as how hydrogen affects cracking resistance, ductility and other mechanical properties will be highlighted. In addition, these tests will be described and special attention will be given to factors that may influence the results such as temperature, gas purity and loading rate.
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In recent years, the need to reduce greenhouse gas emissions has led to increased interest in the use of hydrogen as an energy carrier. In the development of a hydrogen economy, it is important to ensure the structural integrity of many transportation and storage components, which raises the question of the compatibility of alloys exposed to high pressures of hydrogen gas. This issue is particularly relevant when considering the presence of cracking-type defects within the structural component. It is precisely in order to provide answers to this type of questioning that the HYCOMAT platform was designed from 2005 and progressively deployed from 2008 at the Pprime Institute. It consists today of 2 mechanical test benches under gas pressure with different characteristics, a permeation cell and an aging cell under pressure fed by a pressurized gas network. This set allows to realize a wide range of mechanical tests under static, monotonic or cyclic solicitation in a wide range of pressure and temperature, with or without pre-exposure etc.
The objective of this presentation is to present these equipments and the associated metrology, and to illustrate the capabilities with results concerning mainly the fatigue cracking behavior of ferritic materials under high hydrogen pressure.
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This study is part of the French-ANR industrial chair Messiah (Mini-tests for In-Service Monitoring of Structures with Application to Hydrogen Transport). The design of structures requires an understanding of the crack propagation properties of the materials used. To do this, standardised mechanical tests on cracked specimens are mainly used. To be considered valid, these tests must be performed on specimens that are large enough in relation to the size of the fracture development zone. These dimensions are of the order of a few centimeters, but they are more larger as the material is more tough. However, the use of sub-size specimens is unavoidable in several cases: (i) specimens extracted from in-service srtucture in order to have in-service behaviour or during their reception, (ii) during the development of new materials in limited quantities, (iii) when the structure does not allow specimens to be extracted according to the recommendations of the standards (e.g. thin structure). In all these cases, it is difficult or impossible to perform "valid" tests according to the standards. One approach to solve this problem would be to establish procedures for accessing macroscopic properties from sub-size specimens. This study is carried out on a gas linepipe steel (Vintage API grade X52). Firstly, a test campaign is carried out on usual size CT specimens according to the ASTM E1820 standard. The same process is repeated for sub-size CT (mDCT) specimens. The sub-size specimens does not allow to measure the crack opening (CMOD) at the position recommended by the standard. It is then necessary to modify this procedure using FEM analysis in order to access to J-Δa crack propagation curve. The use of sub-size specimens allows to show a strong anisotropy on fracture. Very reproducible results are obtained. A strong size effect is also shown: the J-Δa crack curves on sub-size specimens are systematically located below those of standard CTs specimens.
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Natural Gas (NG) is a fuel that can support the transition from high-emission fossil fuels to renewable energies, in particular by compensating for the intermittency of renewable energies. The gas infrastructure will have to handle a range of greener gases such as biomethane and green hydrogen. Initially, a NG + H2 mix will be transported in the existing network, then in a second phase, when the hydrogen economy is more mature, dedicated pipelines for the transport of pure hydrogen will have to be built.
However, the option of using the existing natural gas system raises the question of how much hydrogen gas can be mixed with the natural gas while ensuring safe operating conditions for the pipe, especially in the presence of crack-type defects. In this regard, the present study was undertaken to obtain an initial assessment of the impact of hydrogen gas content in natural gas on the resistance to crack propagation of pipeline girth welds. For this purpose, toughness and fatigue crack propagation tests were performed at room temperature on a servo-hydraulic machine equipped with an autoclave allowing the conduct of tests under hydrogen, natural gas and mixture. The CT specimens used in these tests were taken from different circular welds representative of those present in the network (respectively from 350 and 900 mm diameter pipes and 7 and 13 mm thick pipes) so that the crack plane is located in the joint. Two pairs of steel and welding process were studied, namely a modern L485 steel pipe (X70) welded by mechanized welding process (GMAW) and a vintage pipe (X60) made of carbon steel with a manual cellulosic electrode process (SMAW). Two environmental conditions have been considered so far, namely a representative NG including 9 minor species and a 25%H-NG mixture with a total pressure of 8.5 MPa. The fracture toughness results for both weld types indicate no significant effect of hydrogen on the K values, while the plastic opening and CTOD values are affected to different degrees. In addition, fatigue crack growth rates are improved by more than an order of magnitude in the 25% H-NG mixture in the high ΔK region compared to NG. Additional analyses, including microfractographic observations, are presented to interpret these results.
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Hydrogen could well become a major player in the energy transition and beyond, in the future global energy landscape. Its properties, uses and associated production processes are very varied and contribute to the adaptability of this energy carrier to a large number of situations, whether for mobility, housing or even the management of renewable energy. Significant progress has been made in recent years, making the large-scale deployment of this technology for energy storage, distribution and production credible. However, a number of challenges remain to be met, notably in terms of energy performance (conversion efficiency and sustainability) and cost. Researchers at the PERSEE Center have been working for about thirty years on improving the processes in question, following a dual approach, system and materials. Some of the materials developed at the Center, catalysts and membranes, for fuel cells, electrolysis or photocatalysis will be presented and with them the approach followed to meet the expectations and attempt to achieve the objectives set by the scientific community.
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Hydrogen is widely used by basic industries, such as the steel industry and by petrochemicals. More recently, hydrogen has been identified as a key energy carrier to replace fossil fuels derived from oil, natural gas and coal which are widely used by these industrial segments and for mobility. In this context of energy transition and with the objective of reducing the effects of global warming by greenhouse gases, the hydrogen industry has a major role to play throughout its value chain (from production, including the use of renewable energies, transport, storage to applications). One of the means of transporting pressurized hydrogen to end-uses (industry or mobility stations) are steel pipelines, with specific mechanical properties and framed by codes such as EIGA IGC Doc 121/14 and ASME B.31-12. These codes allow to control or avoid the embrittlement of steel by hydrogen, by limiting the mechanical strength of steel and by defining adequate pressures. The purpose of this paper is to describe the specifications of commonly used steel grades, the mechanical properties required for the transportation of hydrogen under pressure, the damage modes by static fracture, fatigue and hydrogen-assisted corrosion, the non-destructive inspection techniques applicable to pipeline inspection and attempts to answer the question of the reuse of natural gas pipeline systems for hydrogen service.
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Hydrogen can be present at several stages of heat treatment: carburizing, nitriding, carbonitriding, nitrocarburizing, recruiting with protective atmosphere, quenching, hyperquenching... It seems likely that it can be introduced into the metallographic structure during one or more of these phases. Thus, phenomena of degradation of the quality of materials by hydrogen are known: embrittlement, cracking, hydrogen attack... Despite these damaging phenomena of hydrogen for materials, this molecule has a large number of advantageous characteristics for the success of heat treatments. In this paper, we :
Let's talk about the mechanisms by which hydrogen can be present in a heat treatment chamber
Let's list the properties of hydrogen that are useful for thermo-chemical processes
We remind you of the safety rules and good practices for its safe use.
Each gas used in a heat treatment has a strong influence on the process parameters. In addition to these, in the case of hydrogen, the safety strategy plays a central role. In this work, we identify the checks to be made to ensure compliance with the standard NF EN 746-3 A1.