Papers by Keyword: Hydrogen Embrittlement

Abstract: The transition to hydrogen-based energy systems presents a critical need for materials capable of withstanding the harsh conditions of hydrogen storage. Our project addresses this challenge by developing a multilayer steel designed specifically for hydrogen environments. This material combines austenitic steel, known for its resistance to hydrogen embrittlement, with carbon steel, which provides strength and cost efficiency. Hydrogen embrittlement poses a well-known issue in the storage and transport of hydrogen, often degrading various metals. Although many stainless steels provide superior resistance, its high-cost limits widespread application. Our solution involves a multilayer approach, where austenitic layer serves as the primary barrier against hydrogen-induced degradation, and the carbon steel layer ensures the material’s structural strength under high pressure. The manufacturing process involves hot roll bonding, where the surfaces of the two materials are cleaned of oxides, welded together, heated up to 1200 °C, and then hot rolled to form a strong bond. This method not only strengthens the material but also makes it a potential solution for large-scale hydrogen storage applications.

Abstract: Burning fossil fuels releases greenhouse gases into the atmosphere, causing global warming and climate change. Reducing climate impacts can be achieved by switching to carbon-free energy sources, and hydrogen as a carbon-free energy carrier can be a key parameter. The use of a mixture of natural gas and hydrogen is a much-discussed option. The use of this mixture in industry, e.g. as fuel for gas-fired power plants, would lead to a lower environmental burden due to reduced greenhouse gas emissions. Efficient and economically acceptable distribution of hydrogen is important. The best option is to transport the gas using existing pipeline systems. Hydrogen degrades the mechanical properties of most structural metal materials, especially steel. Describing the degradation of materials exposed to a hydrogen environment is a key parameter for the use of existing natural gas transport infrastructure. For the experiment, X52 steel was used, which is the base material for the natural gas distribution network. Electrolytic saturation was used to charge the material with hydrogen. Different saturation times were tested. The mechanical properties were determined by the notch impact test.

Abstract: The article deals with the influence of process parameters on the properties of the protective coating deposited by Cold Spray technology on X52 pipeline steel. Part of the work is the evaluation of the effect of heat treatment on the resulting properties of the coating. Diamalloy 1003 powder was deposited on X52 steel substrate using four different process parameters, and then the samples were heat treated at 600°C, 800°C and 1000°C. The evaluation of results included analysis of microstructure, porosity and microhardness. The results show that heat treatment has a significant effect on the properties of the coating. The lowest porosity values for all tested parameters were achieved after heat treatment of 1000°C/1 hour.

Abstract: Steel hydrogen embrittlement (HE), a complex and multifaceted issue, can lead to sudden and catastrophic failure, without significant plastic deformation, making it a critical concern in the industrial sector. The present investigation focuses on the evaluation of HE effects regarding microstructure, mechanical properties degradation and type of fracture of AISI 1010 low-carbon steel, after accelerated hydrogen cathodic charging. Hydrogen was diffused electrolytically in 0.2 Μ H₂SO₄ solution, containing 3g/L of NH₄SCN, using a cathodic current density of 10 and 20 mA/cm², for 6 and 18 h. Mechanical properties were investigated through slow-rate tensile tests, as well as Charpy V-notch (CVN) impact tests, to determine the value of fracture toughness, both in uncharged and electrochemically pre-charged specimens. Vickers microhardness tests were conducted on the cross-sections of the hydrogen charged samples to evaluate embrittlement susceptibility, due to the presence of dissolved hydrogen. The microstructure modification was carried out through light optical (LOM) and scanning electron microscopy (SEM), in conjunction with an energy-dispersive X-ray detector (EDS). Slow scan X-ray diffraction (SSXRD) was also conducted for crystal structure analysis. The microstructure analysis showed the presence of large amounts of secondary cracks and cavities into the steel matrix, due to hydrogen diffusion and its accumulation at various sites. Hydrogen charging caused a significant gradual elongation decrease of the parent material, from 25% to 6.73%, in case of embrittlement at 20 mA/cm² for 18h. Accordingly, after 18 h of exposure, the impact energy decrement was determined at 31.5%, at a current density of 10 mA/cm², whereas the corresponding reduction at 20 mA/cm² reached 68%.

Abstract: Hydrogen embrittlement (HE) is a well-known issue, especially with ultrahigh-strength steels (UHSS). Various testing methods are utilised to study HE, but they typically require tensile test equipment, or are impractical due to limited stress control with standard geometries. We have developed a novel Tuning-fork test (TFT) to study HE susceptibility of steels with a new specimen geometry, which can be stressed accurately without tensile test equipment. The test method utilises in situ electrochemical hydrogen charging and constant displacement for stressing of the notched specimens by bending. Crack initiation and propagation are controlled with an isolated tensile stress region, and the failure process is monitored with a loadcell. TFT is a simple and fast testing method, which allows ranking of UHSSs, and to investigate, e.g., microstructural effects on susceptibility to HE and H-induced fracture processes. Here in this study, we present the state-of-the-art with the improved more precise second-generation TFT setup, which benefits from a more sensitive loadcell and a more stable fine-tuneable differential screw adjustment. We extend TFT to testing of martensitic steels with nominal hardness from 400 HBW to 600 HBW with the Incremental step loading technique (ISLT). The results show that TFT with ISLT is well applicable for ranking ultrahigh-strength steels based on their susceptibility to HE. Force-time data from ISLT can also be used for the determination of a material-specific threshold stress level, and the last step for the calculation of a crack initiation-time and time-to-fracture. However, the current manual operation of the loading screw can still limit maximum duration of a test.

Abstract: Austenitic stainless steels are commonly used for hydrogen storage and transportation. These alloys have a high nickel (Ni) content, which increases alloy cost. In this study, high manganese (Mn) austenitic alloys were evaluated as potential lower cost alternatives. Two heats of high Mn alloys with different stacking fault energies (SFE) of ~29 mJ·m^-2 and 49 mJ·m^-2 were acquired. Additionally, a new vanadium (V)-microalloyed high Mn alloy was designed to achieve a SFE of 47 mJ·m^-2 to minimize planar slip deformation mechanisms. Post-processing via cold working in conjunction with aging was also performed on the V-microalloyed high Mn steel. Hydrogen embrittlement sensitivity was investigated using circumferential notch tensile specimens cathodically charged with hydrogen in a 0.05M NaOH electrolytic solution. The alloys were compared to a cold-worked 316L stainless steel, which exhibited no strength loss due to hydrogen. The high Mn alloys with SFE of ~29 mJ·m² and 49 mJ·m^-2 had notch strength losses of 11 and 6 pct, respectively. The V-microalloyed high Mn steel in the as-hot-rolled condition had a notch strength loss of 17 pct. The V-microalloyed high Mn steel in the cold worked and aged condition indicated no notch strength loss in hydrogen, which was comparable to the performance of the 316L stainless steel.

Abstract: Hydrogen embrittlement (HE) is increasingly becoming a critical issue for using high-strength steels in the automotive and infrastructure industries. To overcome the risk posed by HE of structural components under a hydrogen uptake environment in long-term service, it is necessary to clarify the mechanism of HE. In the present study, the presence of hydrogen-enhanced strain-induced vacancies (HESIVs)—one type of defect associated with proposed HE mechanisms—was validated by low-strain-rate tensile tests with in-situ electrochemical hydrogen charging for tempered martensitic steel showing quasi-cleavage fracture with a tensile strength. The effect HESIVs on the mechanical properties of tempered martensitic steel was also studied. The combined use of low-temperature thermal desorption spectroscopy and tensile tests led to the following observations: (i) hydrogen enhanced the accumulation of vacancy-type defects under plastic strain, (ii) accumulated vacancy-type defects adversely affected the ductility of the tempered martensitic steel after hydrogen release, and (iii) aging at 150 °C after applying a given plastic strain with hydrogen charging decreased the amount of newly formed vacancy-type defects and resulted in recovery of ductility.

Abstract: Severe plastic deformation processing and subsequent aging treatment have been known to be effective for achieving higher strength than the conventional aging treatment in aluminum alloys. This study prepared the Al-Cu-Mg-based alloy sample, Al-5.3Cu-2.8Mg (mass%). The alloys were solution treated at 480, 495 and 505°C, and cold-rolled by 90%. The effect of process condition and test environment on tensile properties in cold-rolled Al-Cu-Mg alloys was investigated. Results confirm that strength and ductility were improved with increasing the solution heat treatment temperature regardless of test environment. 0.2% proof stress and ultimate tensile strength were higher than aging treatment specimens, but elongation to failure was lower than aged one. Hydrogen embrittlement susceptibility increased with increasing solution treatment temperature. Ductile fracture with many dimples is observed in both cold-rolled and aged specimens. Second-phase particles were observed at the bottom of the dimples. There was no significant difference in fracture surface between the different test environments.

Abstract: The growing interest towards hydrogen technologies and their implementation in the hydrocarbon and chemical process industry makes maintenance planning of storage and transport equipment an emerging safety aspect. With respect to high-pressure working equipment, Risk-Based Inspection methodology (RBI) aims at minimizing the risk of loss of containment due to materials’ deterioration mechanisms. This set of procedures focuses on the mechanical integrity of equipment to achieve crucial risk mitigation by means of risk-informed inspection planning and maintenance activities. In addition, hydrogen-induced damages are often generalized or even neglected by the existing RBI standards and recommended practices. On this basis, high-pressure vessels, process piping and storage tanks working in gaseous or liquid hydrogen environments, which are exposed to hydrogen-induced deterioration mechanisms, might be subjected to an inaccurate evaluation of the associated risk and hazards when these RBI standards are applied. For this reason, this work proposes a review of the pipelines steels commonly used for gaseous hydrogen transport to investigate the possible limitations of the standard RBI planning methodologies, when applied to hydrogen technologies. More accurately, the pipeline steels’ susceptibility to hydrogen-induced degradations mechanisms will be discussed to underline assumptions and hypothesis limiting the conventional RBI applicability. Therefore, the overall suitability of standard RBI planning with respect to hydrogen equipment is discussed, highlighting possible relevant gaps as a general result.

Abstract: 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.