Search Results (128)

To address the issues of hydrogen embrittlement, creep, and fatigue that commonly occur in the welds of hydrogen production reactor operating under hydrogen exposure, high temperature and high pressure, this study proposes adding Si and Mo as reinforcing elements to the welding materials to enhance weld performance. Given the varying performance requirements of different weld layers in the stacked weld, a gradient performance optimization method for the stacked weld of hydrogen production reactors based on the response surface methodology (RSM)–genetic algorithm (GA) is proposed. Using tensile strength, the hydrogen embrittlement sensitivity index, fatigue strain strength, creep rate and weld performance evaluation indices, a high-precision regression model for Si and Mo contents and weld performance indices was established through RSM and analysis of variance (ANOVA). A multi-objective optimization mathematical model for gradient improvement of the stacked weld was also established. This model was solved using a GA to obtain the optimal element content combination added to the welding wire and the optimal weld thickness for each weld layer. Finally, submerged arc welding experiments of the stacked weld were conducted according to the optimization results. The results show that the tensile strength of the base layer, filling layer and cover layer of the stacked weld increased by 5.60%, 6.16% and 4.53%, respectively. Hydrogen embrittlement resistance increased by 70.56%, 52.40% and 45.16%, respectively. The fatigue and creep resistance were also improved. The experimental results validate the feasibility and accuracy of the proposed optimization method. Full article

In the framework of hydrogen production and storage for clean energy generation, the resistance to hydrogen embrittlement of a newly developed austenitic stainless steel is presented. Gas-atomized metal powders prepared from secondary-sourced metals were employed to manufacture test specimens with Laser Powder Bed Fusion (LPBF) technology. After machining and exposure to a controlled, pressurized hydrogen atmosphere at high temperature, the effect of hydrogen charging on the mechanical performance under static and dynamic conditions was investigated. The stabilizing effect of the optimized chemical composition is reflected in the absence of degradation effects on Yield Stress (YS), Ultimate Tensile Stress (UTS), and fatigue life observed for specimens exposed to hydrogen. Moreover, despite a moderate reduction in the elongation at fracture observed by increasing the hydrogen charging time, ductility loss calculated as Relative Reduction of Area (RRA) remains substantially unaffected by the duration of exposure to hydrogen and demonstrates that the austenitic steel is capable of resisting hydrogen embrittlement (HE). Full article

This study investigates the mechanical behavior of X52 steel pipes and their weld regions under pure hydrogen transport conditions, with a focus on assessing potential hydrogen embrittlement risks. Through experimental analysis, the research evaluates how different pipeline regions—including the base metal, weld metal, and heat-affected zones—respond to varying hydrogen pressures. Key mechanical properties such as elongation, fracture toughness, and crack growth resistance are analyzed to determine their implications for structural integrity and safety. Based on the findings, this study proposes criteria for the safety evaluation of X52 pipelines operating in hydrogen service environments. The results are intended to inform decisions regarding the repurposing of existing pipelines or the design of new infrastructure dedicated to pure hydrogen transport, offering insights into material performance and critical safety considerations for hydrogen pipeline applications. Full article

This paper assesses experimentally and theoretically the hydrogen-assisted cracking sensitivity of an ultrahigh-strength lath martensitic steel, recently used to manufacture tendon rods for structural engineering. The experimental values of the J-integral were obtained by tensile testing up to failure precracked SENT specimens in air, as an inert environment and in a thiocyanate aqueous solution, as a hydrogen-promoter medium. In parallel, the theoretical resources necessary to apply the Dugdale cohesive model to the SENT specimen were developed from the Green function in order to predict the J-integral dependency on the applied load and the crack size, with the cohesive resistance being the only material constant concerning fracture. The comparison of theoretical and experimental results strongly supports the premise that the cohesive crack accurately models the effect of the mechanisms by which the examined steel opposes crack propagation, both when in hydrogen-free and -embrittled conditions. The identification of experimental and theoretical limit values respectively involving a post-small-scale-yielding regime and unstable extension of the cohesive zone allowed for the value of the cohesive resistance to be determined, its condition as a material constant in hydrogen-free medium confirmed, and its strong decrease with hydrogen exposure revealed. Full article

This study investigates the tensile behaviors of wrought 44W steel, Monel 400, 304L austenitic stainless steel, and arc-directed energy deposited (arc-DED) 308L austenitic stainless steel under simulated hydrogen environments to evaluate their endurance to hydrogen embrittlement (HE). The specimens were subjected to cathodic hydrogen charging in an alkaline solution, followed by uniaxial tensile testing at a strain rate of 0.2 min⁻¹. Based on measurements of elongation and toughness, the resistance to HE was ranked as follows: 304L stainless steel > Monel 400 > arc-DED 308L stainless steel > 44W steel. Notably, no significant changes were observed in the yield strengths, ultimate tensile strengths, or elastic modulus of 304L austenitic stainless steel, Monel 400, and 44W steel across all the levels of hydrogenation. However, the arc-DED 308L stainless steel exhibited a slight increase in these properties, attributed to its unique microstructural characteristics and strengthening mechanisms inherent to additive manufacturing processes. These outcomes contribute to a better understanding of the mechanical performance and suitability of these structural alloys in hydrogen-rich environments, highlighting the superior HE resistance of 304L stainless steel and Monel 400 for such applications. Full article

For over five decades, blending hydrogen into existing natural gas pipelines has been explored as a potential solution to reduce greenhouse gas emissions. Despite its promise, implementing this approach has been slow due to concerns about hydrogen embrittlement (HE) and its interactions with various metals. Stainless steel alloys like 316L are commonly used in hydrogen service due to their superior resistance to HE. However, the impact of additive manufacturing (AM) on 316L’s susceptibility to HE when subjected to gas charging has not been thoroughly investigated. To fill this knowledge gap, we created conventionally manufactured and AM 316L tensile bars and solubility specimens, which were then exposed to hydrogen-blended natural gas at 10 MPa with a 50% blend and 100% pure H₂. Both conventionally manufactured and additively manufactured specimens had as-received/printed samples that were used as controls. The samples underwent mechanical evaluation through tensile testing and hot chemical extraction to assess hydrogen solubility. Further analysis revealed significant changes in the microstructure near the fracture area of the soaked samples using scanning electron microscope fractography and metallography. These findings were compared with our previous work on traditionally produced 316L bar stock, which demonstrated that AM processing conditions can yield superior performance in terms of resistance to HE. Notably, this study provides valuable insights into the effects of AM on 316L’s susceptibility to HE when subjected to gas charging. The results have significant implications for the development and implementation of AM 316L for hydrogen/natural gas applications in pressure regulators when AM processing conditions are well-controlled. This article is a revised and expanded version of a paper entitled “Effect of Hydrogen-Blended Natural Gas on Additive Manufactured 316L Stainless Steel in Pressure Regulator Environments”, which was presented at TMS in Las Vegas, March 2025. Full article

The concealment and delayed characteristics of hydrogen embrittlement (HE) pose significant challenges for the development of hydrogen-resistant materials. As a novel category of multi-principal-element alloys, high-entropy alloys (HEAs) have emerged as ideal candidates for the next generation of hydrogen-resistant alloys due to their unique design philosophy, which endows them with excellent mechanical properties, corrosion resistance, high-temperature stability, and hydrogen embrittlement resistance. In recent years, research on the hydrogen embrittlement resistance of HEAs has attracted extensive attention. This review systematically summarizes the hydrogen embrittlement mechanisms in both conventional alloys and HEAs, critically analyzes the contradictions and controversial issues in the current literature, proposes design strategies for hydrogen embrittlement-resistant HEAs, and discusses future research directions in this field. Full article

316L stainless steel is widely employed in various industrial sectors, including shipbuilding, offshore plants, high-temperature/high-pressure (HTHP) piping systems, and hydrogen infrastructure, due to its excellent mechanical stability, superior corrosion resistance, and robust resistance to hydrogen embrittlement. This study presents 316L stainless steel alloys fabricated via hot isostatic pressing (HIP), conducted at 1300 °C and 100 MPa for 2 h, incorporating Cr₂N powder and an optimized Ni/Mn ratio based on the nickel equivalent (Ni_eq). During HIP, Cr₂N decomposition yielded a uniformly refined, dense austenitic microstructure, with enhanced corrosion resistance and mechanical performance. Corrosion resistance was evaluated by potentiodynamic polarization in 3.5 wt.% NaCl after 1 h of OCP stabilization, using a scan range of −0.25 V to +1.5 V (Ag/AgCl) at 1 mV/s. Optimization of the Ni/Mn ratio effectively improved the pitting corrosion resistance and mechanical strength. It is cost-effective to partially substitute Ni with Mn. Of the various alloys, C13Ni-N exhibited significantly enhanced hardness (~30% increase from 158.3 to 206.2 HV) attributable to nitrogen-induced solid solution strengthening. E11Ni-HM exhibited the highest pitting corrosion resistance given the superior PREN value (31.36). In summary, the incorporation of Cr₂N and adjustment of the Ni/Mn ratio effectively improved the performance of 316L stainless steel alloys. Notably, alloy E11Ni-HM demonstrated a low corrosion current density of 0.131 μA/cm², indicating superior corrosion resistance. These findings offer valuable insights for developing cost-efficient, mechanically robust corrosion-resistant materials for hydrogen-related applications. Further research will evaluate alloy resistance to hydrogen embrittlement and investigate long-term material stability. Full article

Interest in hydrogen is rapidly growing due to rising greenhouse gas emissions and the depletion of fossil fuel reserves. Additive manufacturing (AM) is extensively employed to produce high-quality components, with a strong focus on enhancing mechanical properties. The efficiency and cost-effectiveness of AM have further increased interest in its application to manufacturing components capable of withstanding demanding conditions, such as those encountered in hydrogen technology. In this study, 316L stainless steel specimens were fabricated using AM via the selective laser melting (SLM) technique. The specimens then underwent various post-processing heat treatments (PPHT). A subset of these specimens, measuring 50 × 50 × 3 mm³, was tested as electrodes in a water electrolysis cell for oxyhydrogen (HHO) gas production. The HHO gas flow rate and electrolyzer efficiency were evaluated at 60 °C under varying currents. The remaining AM specimens were evaluated for their susceptibility to hydrogen embrittlement under various hydrogen storage conditions, including testing at both room and cryogenic temperatures. Tensile and Charpy impact specimens were fabricated and tested before and after hydrogen charging. The fracture surfaces were analyzed using scanning electron microscopy (SEM) to assess the influence of hydrogen on fracture characteristics. Additionally, as-rolled stainless-steel specimens were examined for comparison with AM and PPHT 316L stainless steel. The primary objective of this study is to determine the most efficient alloy processing condition for optimal performance in each application. Results indicate that PPHT 316L stainless steel exhibits superior performance both as electrodes for HHO gas production and as a material for hydrogen storage vessels, demonstrating high resistance to hydrogen embrittlement. Full article

This work deals with the effects of a non-electrochemically deposited copper- or nickel–phosphorus-based coating on the resulting resistance of traditional X42 grade pipeline steel against hydrogen embrittlement (HE). The susceptibility to HE was determined by the evaluation of the hydrogen embrittlement index (HEI) from the results of conventional room-temperature tensile tests using cylindrical tensile specimens. Altogether, three individual material systems were studied, namely uncoated steel (X42) and two coated steels, specifically with either a copper-based coating (X42_Cu) or a nickel–phosphorus-based coating (X42_Ni-P). The HEI values were calculated as relative changes in individual mechanical properties corresponding to the non-hydrogenated and electrochemically hydrogen-precharged tensile test conditions. Both applied coatings considerably improved the hydrogen embrittlement resistance of the investigated steel in terms of decreasing the HEI values related to the changes in the yield stress, ultimate tensile strength, and reduction of area. In contrast, the hydrogenation of both coated systems had detrimental effects on the value of total elongation, which resulted in an increase in the corresponding HEI value. This behavior was likely related to the earlier onset of necking during tensile straining due to strain localizations induced by the coatings’ surface imperfections. The findings from fractographic observations indicated that both studied coatings acted like protective barriers against hydrogen permeation. However, the surface quality in terms of pores and other superficial defects in the considered coatings remains a challenging issue. Full article

The widespread adoption of electric vehicles (EVs) has introduced new challenges in drivetrain lubrication, particularly concerning electrical corrosion, frictional wear, and hydrogen embrittlement. While polyalphaolefin (PAO)-based lubricants are commonly used, they struggle under high-speed and high-torque conditions. In contrast, polyphenyl ether (PPE)-based lubricants offer superior wear resistance and effectively suppress hydrogen generation, making them promising for EV applications. This study examines the effects of current direction and magnitude on tribofilm formation and frictional behavior in a PPE-lubricated environment. The results show that PPE exhibits unique tribofilm adhesion characteristics influenced by electrical conditions, unlike PAO. Surface analysis reveals that the tribofilm mainly consists of amorphous carbon, and friction under an electrical bias induces PPE oxidation, with oxidation products forming more readily at the positive electrode. Tribofilm formation correlated with increased friction and wear, particularly under currents of 10 mA or higher. Although PPE is more sensitive to electrical influences than PAO, it exhibits excellent wear resistance and maintains a low coefficient of friction even under electrification. This suggests that PPE could be suitable for lubrication in electrical environments and may serve as a promising lubricant for EV drive systems and similar applications. Full article

This study elucidated the effect of Ti–Mo microalloying on the hydrogen embrittlement (HE) resistance and fracture behavior of warm-rolled Fe-5.6Mn-0.16C-1Al (wt%) steel. After intercritical annealing, both steels, i.e., without and with Ti–Mo microalloying, showed ultrafine ferrite (α) and austenite (γ_R) duplex microstructure. The addition of Ti–Mo to 5.6Mn steel reduces the volume fraction of γ_R, facilitating the formation of (Ti, Mo)C carbides in α phase and further refining the final microstructure. The product of ultimate tensile strength (UTS) and total elongation (TEL) of 5.6MnTiMo can be as high as 35 GPa·% with an ultra-high yield strength of above 1.2 GPa. Furthermore, the addition of Ti–Mo also had a significant effect on the resistance to HE of medium Mn steels. Firstly, the limited (Ti, Mo)C carbides precipitated in γ_R could act as irreversibly trap sites to capture a considerable amount of H, effectively increasing the C_H (Diffusible Hydrogen Content). Additionally, 5.6MnTiMo displayed higher γ_R stability, resulting in a reduced susceptibility to HE. The H-assisted microcracks mainly formed inside γ(α′) and extended along γ(α′) grain boundaries, leading to intergranular cracking and premature fracture. Full article

Hydrogen is a promising eco-friendly energy source, but its embrittlement effect on structural materials remains a significant challenge. This study investigates the notch sensitivity of 316L stainless steel under in situ electrochemical hydrogen charging, with a focus on mechanical degradation and fracture behavior. By examining the influence of notch geometry and hydrogen exposure, this research highlights the role of stress concentration in hydrogen embrittlement. The findings contribute to understanding hydrogen-induced material failure, offering insights for both industry practitioners in the energy sector and academic researchers. This study also underscores the need for further research on hydrogen-resistant materials and structural safety considerations in hydrogen applications. Full article

The hydrogen embrittlement susceptibility of a newly developed 1700 MPa-grade ultra-high-strength steel with a primary austenite grain size of 4 μm was studied and the mechanical properties and microstructure were characterized. The results show that the hydrogen content in the steel increases with the extension of charging time: the value reached 0.35 wppm with a charging time of 96 h. On the contrary, the fracture mode of the experimental steel remained ductile after hydrogen charging, and the elongation and the section shrinkage showed little difference, indicating an excellent resistance to hydrogen embrittlement, which could be ascribed to the refined microstructure and good cleanliness of the experimental steel. Full article

This study examines the microstructural evolution and mechanical properties of A500 bulletproof steel joints welded with austenitic stainless steel (ER371) and ferritic (T91) filler materials. While austenitic fillers are traditionally used in bulletproof steel welding to prevent cracking and hydrogen embrittlement, their lower hardness creates a potential weakness in welded joints. This research explores an alternative approach using a newly developed ferritic filler material to achieve strength matching with the base material. Detailed microstructural characterization was conducted using Optical Microscopy (OM) and Scanning Electron Microscopy (SEM), while mechanical properties were evaluated through tensile testing, impact testing, and hardness measurements. The results revealed significantly different mechanical behaviors between the two filler materials, with the ferritic filler achieving superior weld metal hardness (470 HV1) compared to the austenitic filler (185 HV1) in WZ. The fine-grained heat-affected zone (FGHAZ) exhibited the highest hardness (518 HV1) in A500-T91 joints and (480 HV1) in A500-ER371 joints, while ballistic testing demonstrated enhanced penetration resistance with the ferritic filler material. Full article