Search Results (1,631)

The service performance of austenitic stainless steel is substantially affected by the presence of residual ferrite. In this paper, as-cast 12.5% Ni 316L austenitic stainless steel billets are taken as the research object, and samples are selected from the edge, quarter-thickness, and center positions of the billet, as well as two directionally solidified specimens prepared at different withdrawal speeds. By means of metallographic analysis, Thermo-Calc thermodynamic calculations, and EBSD phase analysis, the characteristics of residual ferrite and precipitated phases in the two types of as-cast 12.5% Ni 316L stainless steel were systematically investigated. The results show that the ferrite morphologies at the edge, quarter-thickness, and center positions of the billet are granular and short-rod, skeletal, and clustered net-like and lath-like, respectively. The ferrite morphologies of the two directionally solidified specimens are similar, both being predominantly skeletal structures; the main difference is that in the high-withdrawal-speed directionally solidified specimen (No. 2), the ferrite is finer and more densely distributed. The residual ferrite contents measured at the edge, quarter-thickness, and center positions of the billet are 4.88%, 5.90%, and 8.99%, respectively; those of directionally solidified specimens No. 1 and No. 2 are 6.4% and 7.7%, respectively. For the billet, the ferrite content increases progressively from the edge to the center. Regarding precipitated phases, the edge of the billet exhibits a mixed microstructure of secondary precipitates, namely Sigma phase and Chi phase; at the quarter-thickness position, the coupled precipitation of these two phases is more pronounced; at the center, part of the ferrite has completely decomposed, with the Chi phase disappearing and only the Sigma phase remaining. In the two directionally solidified specimens, only a small amount of the Sigma phase is precipitated as secondary phases, and the ferrite remains relatively intact. Based on the morphology analysis of the ferrite structure, the solidification mode of the billet is determined to be the FA mode, which is consistent with both the Scheil calculation results and the chromium-nickel equivalent calculation results; however, it differs from the thermodynamic equilibrium solidification results obtained using Thermo-Calc. Full article

Accurate high-temperature field characterization is important for explosion diagnostics, laser–matter interaction, combustion monitoring, and related thermal processes. This work presents an integrated thermometry framework combining fiber-optic spectrometry with monochrome imaging. Its central contribution is not a new multispectral principle or optimization algorithm, but an integration-time-dependent radiometric calibration framework coupled with representative spectral-emissivity transfer under clearly stated applicability conditions. Its central element is a three-parameter radiometric calibration model in which camera integration time is explicitly included, so that radiance conversion can be performed across the experimentally calibrated integration-time range without repeating a separate fixed-exposure calibration for each setting. Multiwavelength spectral radiance is used to jointly retrieve temperature and a continuous, second-order polynomial emissivity function with a genetic algorithm serving as the global optimizer. The emissivity function obtained from a representative spectral sampling region is then transferred to the imaging model for pixelwise temperature inversion; this step assumes that the material and surface state are sufficiently uniform over the region to which the function is applied. The method is examined using steady-state tungsten–halogen-lamp measurements with nominal color temperatures of 2200–2800 K and a transient laser-heated 316L stainless-steel case. Agreement with a Wien-based estimate is used as an internal spectral-consistency check rather than as an independent traceable accuracy validation. In the transient case, the retrieved spectral-field-of-view temperature increased from 2311.9 to 2398.5 K over 50–60 s, and the reconstructed images reproduced the corresponding increase in the central high-temperature region. The present results demonstrate the feasibility of coupling integration-time-dependent calibration with measured spectral-emissivity transfer for two-dimensional temperature reconstruction, while the achievable absolute accuracy remains subject to detector linearity, emissivity-model validity, spatial emissivity uniformity, radiometric calibration, and independent reference validation. Full article

Metal additive manufacturing based on Fused Filament Fabrication (FFF) of metal-filled polymers is emerging as a cost-effective alternative to conventional processes such as Metal Injection Molding (MIM), but its industrial relevance remains limited by challenges in densification and mechanical performance. This study presents an exploratory investigation of a low-cost FFF process using 316L stainless steel filament for industrial applications in railway maintenance. A Taguchi L8 design was employed as a screening approach to evaluate the influence of key printing parameters, followed by sintering using both internal and external configurations. The mechanical response depended strongly on sintering temperature: sintering at 1350 °C increased the ultimate tensile strength to 216–278 MPa and Young’s modulus to 63–109 GPa, while the apparent porosity remained between 12.6% and 16.9%. In the exploratory main-effects analysis of variance (ANOVA), none of the investigated printing parameters had a statistically significant effect on the measured responses (p > 0.05). For porosity at 1350 °C, nozzle diameter nevertheless showed the largest descriptive contribution (23.81%, F = 2.06, p = 0.2241). Overall, porosity introduced during the printing stage remained a major limitation of the process. Although the achieved properties remain below those of conventionally processed 316L, the process demonstrates potential for non-structural and cost-sensitive applications. Because each factor combination was tested once, the ANOVA and signal-to-noise (S/N) results are interpreted as exploratory screening and response ranking rather than confirmatory inference or independent evidence of robustness. Full article

A systematic numerical simulation and analysis of the temperature field were conducted for the laser cladding process of CuCrZr alloy onto a 316L stainless steel substrate. First, the thermal properties of the material (density, thermal conductivity, and specific heat capacity) as a function of temperature were calculated using JMatPro software. The equilibrium phase diagram of the CuCrZr alloy was obtained using Thermo-Calc, clarifying the stability of each phase and the solid–liquid phase transition ranges. Based on these findings, three-dimensional transient heat transfer models for single-layer single-pass and single-layer multi-pass cladding were established using ANSYS finite element software and a double-ellipsoidal moving heat source model. The effects of laser power on the evolution of the temperature field, peak temperature, and thermal cycling characteristics were systematically investigated. The simulation results indicate that the temperature field exhibits typical rapid heating and rapid cooling characteristics; the peak temperature increases significantly with rising laser power, and the extent of the high-temperature region expands. A combined analysis of the phase diagram and temperature field results indicates that the peak cladding temperature exceeds the complete melting temperature of the alloy, ensuring sufficient melting. This study provides a reliable theoretical foundation and data support for optimizing laser cladding process parameters, predicting the microstructure of the cladding layer, and controlling thermal stress. Full article

Finger fractures are common and potentially disabling. Certain complex injuries, particularly with small fragments and/or open wounds, are not manageable with conventional orthopedic hardware. We created 3D-printed finger fracture fixators using polylactic acid (PLA) and polyethylene terephthalate glycol (PETG). We tested flexion stiffness and lateral stiffness, before and after sterilization for surgical use, and compared them against standard 316L surgical stainless-steel (SSS) wires. Because PLA and PETG are compromised at high temperatures, these were sterilized using hydrogen peroxide gas plasma, while the SSS wires were autoclaved. The PLA fixators demonstrated greater flexion stiffness, and equivalent lateral stiffness, to the SSS wires, both before and after sterilization. The PETG fixators demonstrated inferior flexion stiffness and lateral stiffness to the SSS wires, and these properties worsened with sterilization. The PLA fixator was then applied to a cadaveric hand in static and dynamic configurations, and demonstrated excellent radiolucency for visualization of bone alignment and healing. This novel PLA device secures numerous surgical stainless-steel wires, maintains greater flexion stiffness and equivalent lateral stiffness compared to the wires even after sterilization, allows for static and dynamic fixation with compact, lightweight, and modular radiolucent components, and is both low-cost and customizable on demand, which may benefit under-resourced communities. Full article

This study investigates the effect of high-temperature hydrogen exposure on the structure and properties of Cr₂O₃/Al₂O₃-based detonation coatings deposited on AISI 316L stainless steel. Bilayer and gradient coatings were exposed to hydrogen at 1000 °C for 3, 4, and 5 h and subsequently characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDS), surface profilometry, and thermal desorption spectroscopy (TDS). One independent specimen was examined for each combination of coating architecture and hydrogen exposure duration. Therefore, the present study was designed as an exploratory comparative investigation rather than a statistically powered study. The principal α-Al₂O₃ and Cr₂O₃ phases remained detectable after all exposure durations, indicating preservation of the main oxide phases. SEM/EDS analysis revealed microcracks, local defects, and heterogeneous surface regions, with more pronounced localized damage in the bilayer coatings. The Ra values of the bilayer coatings were 1.385, 0.833, and 1.207 μm after 3, 4, and 5 h, respectively, whereas the corresponding values for the gradient coatings were 1.049, 1.337, and 1.049 μm. The minimum Ra of 0.833 μm after 4 h in the bilayer coating coincided with SEM/EDS evidence suggesting local coating damage and possible thinning. TDS showed the most intense hydrogen desorption for the gradient coating after 3 h. Overall, the observed results suggest that coating architecture influences surface evolution and hydrogen-retention behavior under the investigated high-temperature hydrogen exposure conditions. Full article

Background: Micro-reservoirs in implant surfaces represent a promising drug carrier concept for drug delivery systems. For drug loading, inkjet printing enables highly precise droplet positioning. However, droplet drying influences drug crystallization from printed drug solution. This study investigates how evaporation-driven phenomena affect the precision and homogeneity of inkjet-based deposition of a crystallizing drug into exemplary micro-reservoirs. The aim is to guide the selection of suitable solvents and inkjet process parameters. Methods: Laser-drilled micro-reservoirs were fabricated as blind holes with entrance diameters of 100 µm and 400 µm in the surface of specimens of EN 1.4404 (equivalent to AISI 316L) stainless steel, a commonly used biomaterial. The reservoirs were loaded with two different drug solutions using piezoelectric drop-on-demand inkjet printing. Acetylsalicylic acid (ASA) was applied as a model drug representing crystallizing small-molecule drugs. Solvents with markedly different evaporation rates, ethanol (EtOH) as a representative high-volatility solvent and dimethyl sulfoxide (DMSO) as a representative low-volatility solvent, were selected. The number of jetted droplets per dispensing step was varied. Precision and homogeneity of the drug deposition were investigated using light and laser scanning microscopy. Results: Over the course of droplet drying, two phenomena, the coffee-ring effect and creeping, can impair drug deposition quality. The coffee-ring effect leads to inhomogeneous, ring-shaped drug deposits. Creeping is the evaporation-driven spreading of crystalline structures and reduces the precision of drug deposition. The EtOH-based ASA solution (c = 10 g/L) was intensely affected by both phenomena. Inhomogeneities could be partially compensated via tailoring the droplet count per dispensing step. The DMSO-based solution (c = 100 g/L) exhibited a more compact crystallization of ASA (requiring ~20% less volume in an exemplary experiment), no coffee-ring effect, and only minor creeping. Conclusions: The DMSO-based ASA solution enabled a more precise and homogeneous drug deposition than the EtOH-based solution under the investigated printing and crystallization conditions. EtOH-related limitations could be counteracted by controlling the number of jetted droplets per dispensing step. Full article

Laser beam welding (LBW) offers low thermal distortion for thin austenitic stainless steel sheets but is sensitive to butt-joint fit-up and edge quality. This study compared machined and sheared joint edges under selected autogenous and ER308L filler-wire LBW conditions. Bead geometry, defects, microstructure, microhardness, tensile properties, and fracture behavior were characterized using conventional microscopy, EBSD-KAM, and three-dimensional digital image correlation (3D-DIC). The machined-edge autogenous condition (LBW-A-M) produced a stable bead with 0.04 mm top underfill and only a small number of internal discontinuities, while its tensile properties remained close to those of the base metal and fracture occurred in the base metal. In contrast, the sheared-edge autogenous condition (LBW-A-S) exhibited 0.24 mm top underfill, 0.18 mm misalignment, multiple pores, and localized strain near the weld, with tensile strength and elongation of 682.31 MPa and 44.04%, respectively. Under the selected filler-wire conditions, no measurable top underfill was observed, although pores remained. Because the autogenous and filler-wire modes used different process parameters and heat inputs, cross-mode differences are condition-specific rather than isolated filler-wire effects. Overall, joint-edge preparation and fit-up control remained important for thin-sheet LBW. Full article

Oxygen management during alcoholic fermentation can redirect phenolic reactions and yeast-derived aroma formation, but the use of mild hyperbaric conditions as a micro-oxygenation strategy remains poorly characterized. This study evaluated the effects of hyperbaric micro-oxygenation at 1.40 ATA in a stainless-steel chamber on the fermentation of Vitis vinifera L. cv. Monastrell must, comparing treated and non-micro-oxygenated samples at the initial, mid-fermentation, and final stages. Physicochemical parameters, CIELAB color coordinates, total phenolic content, volatile organic compounds, and descriptive sensory attributes were analyzed. Hyperbaric micro-oxygenation did not impair fermentation completion, as both treatments reached final residual sugar values of 2.2 g/L and alcohol contents of 15.2–15.4% v/v. The treatment promoted a darker final chromatic profile, with lower L*, the highest overall color difference, and a marked increase in total phenolic content, reaching 1900.9 mg gallic acid equivalents/L compared with 1593.2 mg gallic acid equivalents/L in control. Volatile changes were compound, and stage-dependent, indicating modulation rather than generalized enhancement of aroma formation. Ethyl esters, particularly ethyl octanoate and ethyl decanoate, increased markedly under micro-oxygenation, while acetate esters such as ethyl acetate and hexyl acetate decreased relative to the initial must, reflecting a shift in the balance of aroma-active compounds rather than a uniform increase across all volatile families. These findings support mild hyperbaric micro-oxygenation as a promising non-thermal strategy to modulate Monastrell fermentation quality. Full article

This study presents a methodology for predicting the geometric features of single tracks of 316L stainless steel produced by Powder-Bed Arc Additive Manufacturing (PBAAM) from four independent process parameters using a multi-modal Physics-Informed Neural Network (PINN). PBAAM shares the same powder-deposition and layering scheme as Laser Powder Bed Fusion (LPBF) but uses a low-current micro-TIG arc rather than a laser as the heat source. A multi-task PINN architecture was developed that simultaneously predicts five geometric features measured from two imaging modalities (top-view and side-view arc), namely the arc core diameter (D_q), the arc cone angle (α_c), the heat-affected zone width (w_HAZ), the track core width (d_core) and the areal equivalent track width (w_iz), from four input parameters (arc current, traverse speed, work angle and working distance). The model was assessed on a full-factorial training matrix of 36 experiments and on four pure speed extrapolation experiments above the training range. A composite quality score filter classified 23 of the training experiments as stable and 13 as unstable. On the pure validation set, the mean absolute percentage error (MAPE) was 4.25% (95% confidence interval 0.91–8.49) for the arc core diameter, 6.29% (5.07–7.59) for the arc cone angle, 8.06% (6.08–9.82) for the heat-affected zone width, and 17.02% (10.77–21.62) for the track core width. Classical regression baselines attain comparable aggregate errors on this narrowly distributed validation set; the distinguishing property of the proposed model is the joint, physically ordered prediction of all five outputs. The Ayrton voltage sub-module of the model converged to U(I) = 11.33 + 97.13/I without any direct voltage measurement, purely through the physics loss term; this function is consistent with the order of magnitude expected from the physics of low-current TIG arcs. The results indicate that physics-informed learning can be applied to the PBAAM process parameter space under small-sample conditions. This capability is demonstrated for 316L stainless steel, for the micro-TIG electrode configuration and the process window investigated here, for single tracks rather than multi-layer builds, and against a validation set of four experiments varying in a single direction. Full article

AISI 316L austenitic stainless steel is extensively used in petrochemical storage and processing equipment because of its excellent corrosion resistance. However, exposure to concentrated hydrochloric acid severely destabilizes its passive film, promoting active dissolution and localized corrosion. This work investigates the corrosion behavior of AISI 316L stainless steel in hydrochloric acid solutions of 7.2, 9.6, and 12 M at room temperature. Cyclic potentiodynamic polarization (CPP) tests were performed according to ASTM G61, and the corrosion morphology was characterized using optical microscopy (OM), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and metallographic cross-sections. The electrochemical results revealed an active dissolution regime characterized by the absence of a stable passive region and positive hysteresis loops in all HCl solutions, indicating irreversible surface damage and poor repassivation. The corrosion current density increased from the order of 10⁻¹ mA cm⁻² in 7.2 and 9.6 M HCl to the order of 10¹ mA cm⁻² in 12 M HCl, demonstrating a significant acceleration of the corrosion kinetics. SEM and cross-sectional analyses confirmed the development of localized pitting corrosion, with pit depths reaching approximately 0.87 mm. The results demonstrate that concentrated hydrochloric acid promotes the coexistence of generalized active dissolution and localized pitting corrosion, while increasing HCl concentration modifies the morphology and propagation mode of the pits. Full article

316L stainless-steel capillary tubes are important in medical devices, precision fluid transport and micro heat exchangers, but their slender geometry and dense passivation film make inner-surface finishing inefficient. This study proposes a stepwise chemical-assisted magnetorheological finishing (CMRF) process for 316L capillaries. The inner surface was first pretreated with hydrogen peroxide/oxalic acid to form a removable reaction layer, and then finished by magnetorheological abrasives. The effects of the two reagents on material removal and surface integrity were evaluated, and the optimal pretreatment was determined to be 2.25 wt.% oxalic acid and 1.5 wt.% H₂O₂. Compared with conventional magnetorheological finishing, CMRF increased the material removal rate by approximately 54% and reduced the final inner-surface roughness Sa to 0.116 μm. Characterization results show that hydrogen peroxide and oxalic acid generate a dynamic oxidation–complexation–dissolution–reoxidation cycle, converting the dense passive film into an oxygen-rich, porous, low-crystallinity reaction layer and reducing surface hardness by about 30%. This softened layer promotes preferential abrasive removal instead of direct cutting of the metallic substrate, thereby improving finishing efficiency and surface quality. Full article

In powder-based additive manufacturing (AM), thermal exposure during processing can modify powder surface chemistry and promote oxide growth, even under inert atmospheres from residual oxygen contamination. This study investigates the effect of thermal oxidation on the surface chemistry and triboelectric charging behavior of three AM metal alloy powders: AlSi10Mg, 316L stainless steel (SS 316L), and Ti6Al4V. The work examines the evolution of the oxide layer during baking at 100 and 300 °C using triboelectric charging corroborated by X-ray photoelectron spectroscopy (XPS), diffuse-reflectance spectroscopy, and work-function measurements. The results show that heating modifies the surface oxide state of all powders, with changes dependent on the alloy composition and baking temperature. For AlSi10Mg, heating modified the Al₂O₃-rich surface oxide, with changes consistent with increased oxide ordering and γ-Al₂O₃-like characteristics, with the work function increasing from 4.34 ± 0.01 eV in the as-received (AR) condition to 4.92 ± 0.03 eV after baking at 300 °C. The corresponding triboelectric $n$-exponent increased from 0.91 to 1.38. For SS 316L, transformation of Cr(OH)₃ to Cr₂O₃ reduced triboelectric charge accumulation, while the oxygen concentration increased from 49.92 to 54.87 at.% and the work function decreased from 5.74 ± 0.02 to 5.28 ± 0.04 eV after baking at 300 °C. This reflected a drop in the $n$-exponent from 0.82 for AR to 0.73 at 300 °C. For Ti6Al4V, charging variations were associated with titanium oxide evolution and surface modifications consistent with rutile-related titanium oxide characteristics, with the work function increasing from 5.33 ± 0.01 to 5.44 ± 0.03 eV after baking at 300 °C. The corresponding triboelectric $n$-exponent increased from 0.49 to 0.52. Overall, triboelectric charging is a sensitive approach for detecting thermally driven surface oxide modifications in additive manufacturing powders. Full article

Background: Bacterial biofilms play a key role in causing periprosthetic joint infection (PJI). Current PJI management strategies commonly combine systemic antibiotic therapy with localized delivery such as antibiotic-loaded cement or beads to achieve effective tissue penetration and high antimicrobial concentrations at the implant site. We hypothesized that antibiotic-loaded calcium sulfate beads would effectively eradicate early Staphylococcus aureus biofilms but exhibit reduced efficacy against mature biofilms formed in synovial fluid (SF). This study evaluated the efficacy of vancomycin combined with gentamicin (V+G) or tobramycin (V+T) against GFP-expressing S. aureus biofilms grown in the presence of SF. Methods: Biofilms were established on clinically relevant orthopedic implant materials such as titanium (Ti), stainless steel (316L), and polyethylene (PE). Early (1-day) and mature (3-day) biofilms were treated with calcium sulfate beads loaded with V+G or V+T. Antimicrobial efficacy was quantified by colony-forming unit (CFU) enumeration. Minimum inhibitory concentration (MIC) testing was performed on surviving populations to assess potential development of antibiotic resistance. Results: Both antibiotic combinations resulted in no detectable viable bacteria in the 1-day biofilm across all tested materials following treatment, demonstrating strong reduction in early biofilm burden below the detection limit. Treatment of mature biofilms resulted in a 4–5 log reduction. MIC analysis of representative bacteria surviving post-treatment indicated no substantial increase in resistance. Conclusions: These findings show that while locally delivered antibiotic combinations eliminate early biofilms, mature biofilms demonstrate significant tolerance. MIC analysis showed little or no change in vancomycin, gentamicin, and tobramycin susceptibility after treatment, indicating no evident increase in planktonic antibiotic resistance among the surviving isolates. Together, these results highlight the importance of early intervention and the need for strategies that disrupt biofilm structure or improve antibiotic penetration to enhance PJI treatment outcomes. Full article

This study empirically and numerically investigates sintering-induced shrinkage of 316L stainless steel cylinders fabricated via Bound Metal Deposition (BMD). Sintering shrinkages were measured for three cylindrical specimens, one each in x-, y-, and z-print orientations, via a dilatometer. Each specimen was horizontally sintered to 1360 °C via a prescribed temperature profile to maintain identical sintering conditions between specimens. Numerically, a two-dimensional axisymmetric finite element model was implemented in Abaqus using a user-defined viscoplastic constitutive model incorporating porosity- and temperature-dependent viscosities, grain-growth kinetics, and capillary-driven sintering stress. Model parameters were calibrated using particle swarm optimization by minimizing a combined error metric for temperature-dependent shrinkage responses and final relative densities. Results indicate: (1) final shrinkages of 13.5%, 13.7%, and 14.3% for the x-, y-, and z-oriented specimens, respectively, and (2) the optimized numerical model utilizing literature-informed material property constraints results in shrinkages and final densities that are in good agreement with empirical observations. Importantly, this work (1) suggests sintering shrinkage may depend on print orientation, in addition to furnace orientation, for BMD-fabricated 316L stainless steel, and (2) adds an initial dilatometer data set for BMD 316L to the literature. More broadly, this work supports future design activities via an experimental and numerical characterization of sintering behavior. Full article