Search Results (2,600)

Additive manufacturing (AM) of stainless steel has been gaining industry attention in recent years due to the need to manufacture complex steel components. Many sectors stand to benefit from the design flexibility, customization, and rapid production capabilities of AM. However, the industry’s adoption of this technology remains limited due to concerns about the mechanical integrity and reliability of AM products. This experimental study examines the wear and tribological behavior of Wire Arc Additive Manufactured (WAAM) austenitic stainless steel 316L. Pin-on-disk tests were conducted using a 5 mm tungsten carbide ball under dry sliding conditions at normal loads of 1.5 and 2.5 N and sliding speeds between 0.03 and 0.229 m/s. The results showed that the coefficient of friction remained relatively stable at approximately 0.6, while wear volume generally decreased with increasing sliding speed. Lower normal loads resulted in lower wear volume, whereas the wear factor showed only limited sensitivity to the applied load. Optical microscopy revealed a ferrite–austenite microstructure with residual δ-ferrite that contributes to the observed wear behavior. These findings demonstrate the suitability of WAAM-produced 316L stainless steel for tribological applications requiring stable frictional performance. Full article

Laser powder bed fusion (LPBF) produces microstructural anisotropy that influences hydrogen transport and passive film stability, yet the mechanistic relationship between build orientation, passive film chemistry, and corrosion behavior remains insufficiently understood. This study investigates how LPBF build orientation governs hydrogen-assisted passive film degradation by correlating electrochemical behavior with passive film chemistry. Additively manufactured 316L stainless steel specimens were fabricated in two build orientations, horizontal (0°) and vertical (90°), and subjected to electrochemical hydrogen charging for durations ranging from 2 to 36 h. Corrosion behavior was evaluated using open-circuit potential (OCP), electrochemical impedance spectroscopy (EIS), linear polarization resistance (LPR), and potentiodynamic polarization (PDP), while X-ray photoelectron spectroscopy (XPS) was employed to characterize hydrogen-induced changes in passive film chemistry. The electrochemical response showed that hydrogen charging progressively reduced the corrosion resistance of both build orientations. However, the degradation exhibited a non-monotonic dependence on charging duration, with intermediate charging durations suggesting transient repassivation before renewed deterioration during prolonged hydrogen exposure. EIS analysis revealed a substantial decrease in the fitted total resistance (R_total = R_ct + R_po), from 1.44 to 0.27 kΩ cm² for the 0° specimens and from 4.23 to 0.55 kΩ cm² for the 90° specimens. Potentiodynamic polarization showed that prolonged hydrogen charging increased the corrosion current density from 20.99 to 98.91 μA cm⁻² for the 0° specimens and from 0.79 to 46.86 μA cm⁻² for the 90° specimens. XPS analysis revealed progressive depletion of protective oxide species (Fe₂O₃, Cr₂O₃, Mo oxides, and lattice oxygen) together with enrichment of hydroxide-rich species, resulting in a lower O²⁻/OH⁻ ratio and transformation of the passive film into a more porous and less protective surface layer. These chemical changes were more pronounced in the 90° build orientation and were consistent with the greater reduction in passive film stability observed from the electrochemical measurements. The combined electrochemical and XPS analyses establish that LPBF build orientation governs hydrogen-assisted corrosion through its influence on microstructural anisotropy, hydrogen transport, passive film chemistry, and the resulting electrochemical response, providing mechanistic insight into the corrosion behavior of additively manufactured 316L stainless steel in hydrogen-containing environments. Full article

Forgings currently have long lead times, motivating technology developments that produce parts with forge-like properties and have shorter timelines. Solid-state processes such as additive friction stir deposition (AFSD) offer this potential; however, large-scale deposition of high-temperature materials remains limited by tool durability, thermal management, and process stability. In this study, new polycrystalline cubic boron nitride (PCBN) AFSD tools, integrated with a liquid-cooled tool holder, are developed and evaluated for bulk deposition of 316 L stainless steel. Tool geometry modifications, including increased puck diameter and a drafted feed exit orifice, enabled graphite-free deposition by mitigating feedstock swaging. A minimum deposition rate is identified that maintains stable material flow and avoids excessive actuator forces. Comparing the use of PCBN tools with different shank materials shows that tungsten carbide shanked tools have improved thermal management relative to tools with a nickel-based shank. This improved thermal regulation resulted in more stable deposition, reduced tool wear, and successful multi-layer builds. Additionally, the use of a fully enclosed inert gas environment reduces surface oxidation and interlayer oxide formation. Electron microscopy was used to reveal limited tool-related contamination in the deposition. The contamination observed was dispersed boron nitride particles rather than continuous interfacial layers of tool material as observed in other literature. These results demonstrate that PCBN tooling combined with active cooling can enable stable, bulk AFSD of high-temperature alloys. Full article

Defects such as lack-of-fusion pores, keyhole pores, and thermal cracks are inherent to additively manufactured (AM) components and significantly degrade their mechanical performance, yet their quantitative influence on the strength of AM structures remains insufficiently understood. In this study, a columnar-grained microstructure of AM 316L stainless-steel pipe material containing explicit pores and cracks was reconstructed using the Monte Carlo method based on SEM observations and was incorporated into a calibrated crystal plasticity finite element model. The reconstructed columnar-grain width agreed with the measured value, and the predicted yield strengths of both defect-free and defect-containing material matched tensile measurements, confirming the accuracy of the micromechanical framework. Moreover, the influences of the pore diameter, crack length, pore arrangement, and porosity on the circumferential and axial yielding were systematically investigated. Results showed that increasing the size of the pore and porosity reduced the circumferential and axial yield strengths simultaneously with distinct extents. Cracks exhibited pronounced directional sensitivity: circumferential cracks mainly reduced axial capacity, whereas an axial crack reduced circumferential strength significantly, indicating that crack-induced degradation is governed by the interaction between crack orientation and loading direction. Directional pore arrangements produced anisotropic responses, whereas random arrangements reduced this anisotropy and resulted in a quasi-isotropic response, although clustering at higher porosity intensified local stress-concentration interactions and further lowered load-bearing capacity. The results clarify the mechanisms of defect-induced stress concentration and local plastic evolution and provide a quantitative basis for defect-tolerance assessment and quality control of AM components. Full article

Triply periodic minimal surface (TPMS) lattices are an emerging class of cellular architectures whose smooth, mathematically defined surfaces enable highly tailorable mechanical performance. This study quantifies the compressive elastic response of three sheet-based TPMS topologies, i.e., Diamond, Gyroid, and Lidinoid, through finite element (FE) analysis and experimental validation. For each topology, the effective Young’s modulus was computed by single-cell finite element analysis under uniaxial compression boundary conditions on a 2 mm unit cell across five wall thicknesses (0.35, 0.45, 0.65, 0.95, and 1.30 mm), corresponding to relative densities from approximately 25% to 95%. Experimentally, cylindrical specimens of 316L stainless steel at 70% relative density were fabricated by laser powder bed fusion (LPBF) and tested in uniaxial compression with a strain rate of 10⁻³ s⁻¹ per ISO 13314:2011 (i.e., 0.02 mm/s). The Diamond topology exhibited the highest effective modulus across the full density range, followed by Lidinoid and Gyroid. FE predictions agreed with experimental moduli within 4.7% for Diamond (100.2 GPa vs. 95.5 ± 3.9 GPa), 0.04% for Gyroid (79.8 GPa vs. 79.8 ± 0.88 GPa), and 1.5% for Lidinoid (85.6 GPa vs. 86.9 ± 3.5 GPa). Moreover, the Gibson–Ashby exponents determined span the range from stretching- to bending-dominated deformation with n = 1.69 for Diamond, 1.74 for Lidinoid, and 2.08 for Gyroid. Single-cell FE analysis accurately captured the effective elastic response of LPBF 316L stainless steel TPMS lattices examined. Full article

The transition to a decarbonized energy infrastructure relies on repurposing existing pipelines for hydrogen–methane mixtures, which introduces significant concerns regarding hydrogen embrittlement. Accordingly, a coupled Multiphysics phase-field model was developed to predict hydrogen-assisted failure in elastic–plastic solids. This framework is numerically implemented via the finite element method to predict the structural integrity of pipeline steel strength classes representative of API 5L X65, X70, and X80 by explicitly accounting for elastoplastic deformation, hydrogen trapping effects, and stress-driven diffusion. By computing crack growth resistance curves across various scenarios, it has been demonstrated the capability of the model to capture material sensitivities by varying hydrogen–methane blend compositions, operational pressures, and the elastoplastic deformation behavior of different strength grades. The investigation revealed that methane limits surface hydrogen coverage, thereby mitigating the crack-tip decohesion mechanism. Furthermore, the model indicates that at a pressure of 7.5 MPa, a 15 vol% hydrogen–methane blend enables these materials to retain 80–90% of their fracture toughness and exhibit ductile failure. Finally, higher-strength steel classes (representative of X80) demonstrate greater susceptibility to hydrogen embrittlement under these conditions due to yield stress-amplified hydrostatic stress, whereas lower-strength steels exhibit greater defect tolerance for the hydrogen-blend transition. Full article

Hydrogen diffusion plays a central role in the susceptibility of steels to hydrogen embrittlement, yet reported diffusivity values often exhibit significant variability due to differences in experimental methodology. Gaseous hydrogen permeation experiments, while more representative of service conditions, are highly sensitive to surface boundary conditions and trapping effects, which can bias the diffusivity obtained from analysis. In this work, a gaseous hydrogen permeation methodology was developed at the High-Performance Powertrain Materials Laboratory (HPPM) at the University of British Columbia, Okanagan. A dedicated gas management system (GMS) was implemented to enable controlled pressure step transients, allowing partial permeation transients to be collected under gaseous charging conditions. This approach was applied to commercially pure iron and API 5L X60 pipeline steel to evaluate diffusion and trapping behaviour across materials with differing microstructural complexity. The results demonstrate that diffusivity obtained from transients spanning the full charging–discharging range (0–2 MPa) reflects an effective parameter influenced by reversible hydrogen trapping, whereas transients measured over incremental pressure steps (1–2 MPa) provide a more consistent estimate of lattice-controlled diffusion. The application of palladium coatings to the charging surface was found to promote hydrogen entry, reducing surface impedance effects and further improving agreement with Fickian diffusion behaviour. Full article

Cobalt–nickel–copper alloys were electrodeposited over a range of current density and with three different aqueous electrolytes having variable metal ion ratios, in order to examine changes in the deposit composition and to use them as cathodes for nitrate electrolysis. The alloys were electrodeposited galvanostatically from a citrate electrolyte onto rotating cylindrical steel substrates. The electrodeposition process exhibited anomalous codeposition behavior, favoring Co reduction over Ni and Cu. These electrodeposits were then used to examine their ability to reduce nitrate in simulated wastewater with 50 mg-N/L of NO₃⁻, sodium chloride, and sodium sulfate. Nitrate conversion and selectivity were characterized after electrolysis in a single-compartment cell with the alloys serving as the working electrode. Despite co-evolving hydrogen, the electrodeposited alloys were effective at generating both N₂ at high electrolysis current densities and ammonia species at lower values, with the deposit composition also affecting the conversion and products. It is the first demonstration of using Co-Ni-Cu ternary alloys for nitrate reduction. Full article

With contemporary advancements in additive manufacturing (AM), it has become possible to obtain hull structures for spacecraft made of relatively cheap materials. The possibility of substituting super-austenitic stainless steel Avesta SMO 254 X1NiCrMoCuN20-18-7 (EN 10088) for that already used in the Starship SpaceX 304 L-Modified is focused on achieving better thermal stability and durability in extreme conditions. The Directed Energy Deposition Arc (DED-Arc) method for AM has enabled the production of high-strength-to-weight ratios. The aim is to engage low-cost material with treatment optimization to provide greater corrosion resistance and high yield and tensile strength. For the DED-Arc, a filler wire was selected for the welding source, Fronius TPS 400i. A simulation via the RoboDK Robot Development Kit for the FANUC ARC Mate 100ID10L is provided. Additional shot pining/vibration treatment is proposed for the finished structure, which can be a substitute for the cold-worked initial metal. A comparison is made for stainless steel that has already been tested for space travel. Regimes for the manufacturing process are proposed, with representative samples of Avesta SMO 254 obtained and tested using microhardness measurements, microcracking detection, porosity measurements, interface zone assessment, and microstructural analysis. The DED-Arc process can be applied to large-space shell manufacturing. A comparison is made with a focus on the mechanical and corrosion advantages. For Avesta SMO 254, microhardness measurements ranged from 235 to 246 HV1 and increased after treatment. The controlled parameters provided a maximum heat input of 0.7 KJ/mm, no defects, and a fine microstructure. The successful use of stainless steel with AM increases the potential for multiple space missions. The advanced method shows high quality, allows cost savings and provides extended service life. Full article

Hydrogen-induced cracking (HIC) is a possible failure mode of high-strength pipeline steel welded joints. The HIC susceptibility of shielded metal arc-welded joint of X100 pipeline steel was investigated using the slow strain rate tensile test (SSRT) under current densities of 2 mA/cm², 5 mA/cm², 10 mA/cm², 20 mA/cm², and 30 mA/cm². Hydrogen diffusion behavior, distribution of microstructures, and inclusions in the welded joint were also surveyed and characterized. The SSRT results indicated that the welded joint exhibited a higher hydrogen embrittlement index than the base metal (BM) under the same current density, showing a higher HIC sensitivity than the BM. The weld metal (WM) showed a lower hydrogen diffusivity (5.38 × 10⁻⁵ cm²·s⁻¹) than the BM (6.23 × 10⁻⁵ cm²·s⁻¹). The martensite–austenite (M-A) constituent area fraction in the WM was higher than that in the coarse-grained heat-affected zone (CGHAZ), fine-grained HAZ (FGHAZ), and BM. The inclusion amount in the WM was larger than that in the BM. In addition, the high HIC vulnerability of the X100 steel welded joint was also associated with a coarse grain size in the WM. Full article

Spent water-based drilling fluids generated during the construction of technological wells impose substantial environmental, water-management, transportation, and energy burdens. Conventional practices, including storage in temporary pits, prolonged settling, and off-site disposal, do not enable process-water recovery and require repeated handling of suspensions with a high solids content. This study evaluates a pressure-driven cylindrical hydrodynamic disperser as the central component of a compact on-site treatment system. Unlike conventional mechanical mixers, the disperser contains no driven shaft within the active chamber. Particle–reagent contact is intensified through controlled jet shear, vortex-induced redistribution, and the motion of freely moving steel balls. Field-derived drilling fluids containing 30–40 wt.% solids, with densities of 1.12–1.17 g/cm³, pH values of 7.4–8.2, and median particle sizes of 15–50 μm, were treated at velocity gradients of 500–1500 s⁻¹ for 60–180 s using Superfloc N-300 dosages of 0–100 g/t. The optimal operating conditions were G = 1300 s⁻¹, τ = 150 s, and D = 50 g/t. Under these conditions, the separation efficiency reached 91–93%, the residual suspended-solids concentration decreased to 120–130 mg/L, process-water recovery reached 80%, sludge volume decreased by 40–60%, and specific energy consumption was approximately 0.30 kWh/m³. More intensive treatment increased the separation efficiency to 94–95% but resulted in a less favorable balance among energy consumption, reagent dosage, and resource recovery. Compared with mechanical mixing, the selected treatment system reduced flocculant consumption by 37.5%, treatment time by more than threefold, and specific energy consumption by 40%. These results support the use of modular on-site systems for process-water recirculation and reduced sludge-transport requirements at remote drilling sites. Full article

To address the challenges of low image quality and difficult feature extraction of weld beads caused by the complex dynamics of the molten pool, intense arc light, and spatter interference during wire arc additive manufacturing (WAAM) of 316L stainless steel, this paper develops a binocular vision-based dynamic molten pool tracking system and conducts image processing and feature analysis. Two high-speed CMOS cameras are employed to capture images of the molten pool and weld bead. Camera calibration is performed to convert pixel coordinates to world coordinates. The denoising performance of five filtering methods, namely mean, Gaussian, median, maximum, and minimum filters, is systematically compared, and the minimum filter is selected for noise reduction. Adaptive threshold binarization, adapthisteq image enhancement, and morphological threshold segmentation are integrated to effectively separate the weld bead from the background. Four edge detection algorithms—Sobel, Robert, Laplacian, and Canny—are compared, and the Canny algorithm combined with Hough transform line fitting is determined to achieve complete and continuous extraction of the weld bead contour. The Intersection over Union (IoU) metric is introduced for image quality screening. When IoU is set to 0.3, the detection accuracy exceeds 90%, effectively eliminating defective images caused by spatter, explosion, trailing, and other disturbances. The proposed method facilitates stable extraction of geometric parameters (e.g., pixel area of the weld bead and height/width of the molten pool), thereby offering a feasible image-processing solution for dynamic molten-pool monitoring and online quality assessment of 316L stainless steel components fabricated by wire arc additive manufacturing. Full article

AISI 316L stainless steel (316L SS) exhibits inadequate corrosion resistance in chloride-containing soils. Fe-based amorphous coatings (Fe-ACs), owing to their high Cr, Mo, and W contents and defect-free amorphous structure, are promising candidates for superior protection. In this work, the corrosion behavior of 316L SS and an Fe-based amorphous coating (Fe-AC) fabricated by high-velocity oxygen-fuel (HVOF) spraying was systematically compared by burial in Daqing saline soil (25% water content) with 0, 1.0, and 2.0 wt.% NaCl for 15–55 days. Corrosion rates were measured via mass loss, and surface morphology, elemental distribution, and phase constitution were characterized using OM, SEM/EDS, and XRD. Electrochemical impedance spectroscopy and potentiodynamic polarization were employed to assess passive-film stability and charge-transfer resistance. The Fe-AC consistently exhibited an extremely low corrosion rate (below 0.01 mm y⁻¹), nearly independent of NaCl concentration and exposure time, with only sporadic rust spots and the formation of a compact Cr/Mo/W-enriched passive film. In contrast, after 55 days in soil containing 2.0 wt.% NaCl, the 316L SS showed a corrosion rate of 0.0562 mm y⁻¹—six times that of the Fe-AC—accompanied by severe pitting (pit depth up to 3.6 mm) and loose corrosion products (γ-FeOOH and α-Fe₂O₃). Electrochemical tests confirmed that the charge-transfer resistance of the Fe-AC under the 0% NaCl condition reached 1.16 × 10⁶ Ω cm² and its breakdown potential exceeded 1.12 V, far outperforming 316L SS (2.30 × 10³ Ω cm² and 0.22 V, respectively). The novelty of this study lies in the systematic evaluation of the buried corrosion performance of HVOF-sprayed Fe-based amorphous coatings versus 316L SS in an actual saline soil and in elucidating the synergistic passivation mechanism of Cr, Mo, and W. This passive film effectively impedes chloride ingress and maintains high impedance over extended periods. Full article

The structure–activity relationship of three oxyphosphonate inhibitors differing in heteroatom type (C, N, S) was examined to clarify their influence on the pitting corrosion resistance of ferritic–martensitic steel EP-450 in chloride media. Gravimetric tests in 10% FeCl₃, supported by surface microscopy and adsorption analysis, showed that EP-450 is highly susceptible to localized attack, with pits nucleating preferentially at carbide-enriched, chromium-depleted regions. Addition of dimethyl(1-hydroxycyclohexyl)phosphonate reduced the corrosion rate from 49 to 33 mm/year at 2.0 g/L, corresponding to ≈33% protection, while the nitrogen-containing dimethyl[1-(2-ethoxyethyl)-4-hydroxypiperidin-4-yl]phosphonate produced the largest decrease in mass loss, exceeding a 55% reduction under identical conditions. The sulfur-bearing dimethyl(4-hydroxytetrahydro-2H-thiopyran-4-yl)phosphonate afforded an intermediate effect. Adsorption analysis for the cyclohexyl derivative suggested mixed physisorption–chemisorption with limited surface coverage, while heteroatom substitution (N or S) is consistent with a change in adsorption configuration and interfacial packing that can yield a more compact protective layer. The observed inhibition efficiency increased in the sequence C < S < N, which is interpreted empirically in terms of heteroatom-dependent adsorption geometry and film integrity rather than conjugation-driven activation of the P=O group. Full article

Coiling temperature is a pivotal process parameter for hot-rolled strip steel, which directly determines the microstructure and mechanical properties of final products. Affected by the coupling of multiple process variables, coiling temperature presents strong nonlinearity and complex time-varying characteristics. Traditional heat transfer mechanism models, Random Forest (RF), Extreme Learning Machine (ELM) and single Long Short-Term Memory (LSTM) networks fail to fully explore the deep correlation among variables. In addition, their hyperparameters are generally selected by manual trial-and-error, leading to unsatisfactory prediction accuracy and poor robustness in practical production. To address the above limitations, this paper proposes a novel prediction model named WOA-CNN-GRU-SE, where the Whale Optimization Algorithm (WOA) is adopted for parameter optimization. Firstly, Convolutional Neural Network (CNN) is utilized to extract local coupling features from various working condition parameters. Secondly, the Squeeze-and-Excitation (SE) attention mechanism is applied to adaptively recalibrate channel weights, which enhances key features closely related to temperature variation and suppresses redundant interference information. Afterwards, Gated Recurrent Unit (GRU) is employed to conduct in-depth learning of temporal features. Furthermore, WOA is used to globally optimize critical hyperparameters, including learning rate, the number of GRU hidden units and L2 regularization coefficient, so as to eliminate the drawbacks of manual parameter tuning. Comparative experiments are conducted on actual production data from a hot rolling line. The results demonstrate that the proposed model outperforms CNN-GRU, CNN-GRU-SE, LSTM, RF and ELM in prediction performance. Its hit rate reaches 92.56% within the industrial error range of ±6 °C. This model effectively realizes accurate prediction of coiling temperature under complex working conditions and possesses great application potential in industrial practice. Full article