The use of hydrogen-blended natural gas presents an efficacious pathway toward the rapid, large-scale implementation of hydrogen energy, with pipeline transportation being the principal method of conveyance. However, pipeline materials are susceptible to hydrogen embrittlement in high-pressure hydrogen environments. Natural gas contains various impurity gases that can either exacerbate or mitigate sensitivity to hydrogen embrittlement. In this study, we analyzed the mechanisms through which multiple impurity gases could affect the hydrogen embrittlement behavior of pipeline steel. We examined the effects of O₂ and CO₂ on the hydrogen embrittlement behavior of L360 pipeline steel through a series of fatigue crack growth tests conducted in various environments. We analyzed the fracture surfaces and assessed the fracture mechanisms involved. We discovered that CO₂ promoted the hydrogen embrittlement of the material, whereas O₂ inhibited it. O₂ mitigated the enhancing effect of CO₂ when both gases were mixed with hydrogen. As the fatigue crack growth rate increased, the influence of impurity gases on the hydrogen embrittlement of the material diminished.

This study systematically investigated the influence of aging temperature variations on the evolution of Cu-rich precipitates and dislocation distribution characteristics in 17-4PH stainless steel through comprehensive electrochemical testing and microstructural characterization. The mechanism by which microstructural features govern electrochemical corrosion behavior was elucidated. Experimental results demonstrated that within the aging temperature range of 480–620 °C, matrix dislocations consistently maintained non-uniform distribution characteristics, though their regional heterogeneity exhibited a decreasing trend with increasing temperature. The precipitation behavior of copper followed an evolutionary sequence: transitioning from dispersed copper precipitates to finely distributed Cu-rich precipitates with high numerical density, ultimately progressing to coarsening and agglomeration. The corrosion resistance of the material initially improved before subsequent degradation, accompanied by a morphological transition of surface corrosion features from characteristic elongated striations to elliptical patterns. Samples aged at 580 °C for 4 h exhibited optimal corrosion resistance. Mechanistic analysis revealed that reduced dislocation density heterogeneity effectively minimized electrochemical potential differences between micro-regions, while elemental segregation induced by Cu-rich precipitates coarsening intensified local electrochemical inhomogeneity. These two mechanisms cooperatively regulated the overall corrosion resistance evolution of the material.

W-modified TiAlN coatings were developed as hydrogen permeation barrier coatings for magnetic materials. TiAlN and TiAlN-W coatings with comparable thicknesses of approximately 1.5 μm were deposited on Fe and NdFeB substrates by physical vapor deposition. GIXRD and SEM results showed that W modification was associated with a change from weakly crystalline, columnar TiAlN to a more compact, low-crystallinity W-modified Ti–Al–N coating with amorphous/nanocrystalline features inferred from the broad diffraction response. XPS analysis identified low-valence W-related species, such as W–N/Wⁿ⁺-related bonding, together with overlapping Ti 3p/W–O_x contributions and surface oxide/oxynitride species, indicating a modified surface and near-surface chemical environment. Electrochemical hydrogen permeation tests on Fe substrates showed that TiAlN reduced the steady-state current density from 2.54 ± 0.86 to 0.55 ± 0.08 μA cm⁻², corresponding to a permeation reduction factor of 4.68 ± 0.16. In contrast, TiAlN-W showed no obvious hydrogen breakthrough during the 15,000 s test period, and the current density remained below the practical detection limit of 0.01 μA cm⁻², giving a lower-bound permeation reduction factor of >250. In high-pressure H₂ exposure tests, the TiAlN-W-coated NdFeB sample remained macroscopically intact after exposure to 5 MPa H₂ at 23 °C for 24 h, whereas the uncoated and TiAlN-coated samples were pulverized. The markedly improved hydrogen permeation resistance is associated primarily with the more compact cross-sectional morphology and W-modified coating structure.

Local chemical heterogeneity is a typical feature of selective laser melted (SLM) austenitic stainless steel and is closely related to its hydrogen-assisted deformation behavior. In this work, molecular dynamics simulations are performed to investigate the effects of local segregation on stacking fault energy, hydrogen diffusion, and dislocation motion in austenitic stainless steel. Three representative alloy compositions, Fe₇₁Cr₁₇Ni₁₂, Fe₇₁Cr₂₃Ni₆, and Fe₇₁Cr₁₁Ni₁₈, are used to describe local composition variation associated with segregation in SLM-relevant austenitic stainless steel. The results show that Ni-rich regions exhibit relatively higher stacking fault energy and faster hydrogen diffusion, whereas Cr-rich regions show lower stacking fault energy and reduced hydrogen mobility. Hydrogen further decreases the stacking fault energy in all three alloy models and exerts a stronger influence on local defect energetics than composition variation alone. Shear simulations indicate that elemental segregation itself has only a limited direct effect on dislocation motion, whereas its interaction with hydrogen leads to a more evident retardation of partial dislocation propagation within the segregation region. These findings highlight the coupled roles of local composition variation and hydrogen in governing defect evolution and local deformation behavior in segregation-containing regions.

A Fe₅Cu₅V₃₀Ti₃₀Nb₃₀ high-entropy alloy film was designed as a Cr- and Al-free metallic sensing layer for thin-film strain gauges in high-pressure hydrogen environments. CALPHAD calculations predicted a BCC/B2-type phase field, while XRD, EBSD and GIXRD results supported a BCC-type structure without direct confirmation of long-range B2 ordering. Fe₅Cu₅V₃₀Ti₃₀Nb₃₀ films deposited on Si reference substrates at 150 and 300 W retained broad BCC-type diffraction features. The 300 W film showed a more continuous cross-sectional morphology, good metallic conductivity and a comparable nanomechanical response with slightly higher hardness. Device-level tests were then performed using Cr/AlN/Fe₅Cu₅V₃₀Ti₃₀Nb₃₀ TFSGs on 316L stainless-steel substrates. The devices exhibited average absolute apparent zero shifts of 16.08 με in 12 MPa N₂ and 17.79 με in 12 MPa H₂, with an additional H₂-associated apparent response of only 1.71 με. Static tensile tests in 12 MPa H₂ confirmed a linear strain response with a gauge factor of 1.72 ± 0.01.