Search Results (436)

Magnesium alloys are considered to be the third generation of biomaterials used in biomedical applications to promote bone tissue regeneration. Due to their Young’s modulus being similar to that of human bone and their release of magnesium ions that are antimicrobial and osteoinductive, these biomaterials not only promote bone regeneration, minimize the effects of stress shielding and reduce the risk of infection, but also their exceptional biocompatibility and bioresorbability eliminate the need for a second surgery to remove the implant. However, because magnesium has poor corrosion resistance, without different coatings and surface treatments, the implant can be compromised before the bone is fully healed. With additive manufacturing (AM) as a revolutionary technology, the one-size-fits-all approach can be replaced by fully personalized medicine, in which complex shapes can be created, designed, and processed with unique parameters for each patient. However, 3D printing of Mg-based devices remains particularly challenging due to magnesium’s high chemical reactivity, combustion risk, and low vaporization temperature, challenges that are further compounded when alloying elements are introduced. This review addresses this gap by critically examining the properties, corrosion behavior, and bio-medical performance of Mg and its alloys, with a focused analysis of selective laser melting (SLM) and wire arc additive manufacturing (WAAM) as key fabrication methods. The influence of processing parameters, microstructural defects, and alloy composition on the final properties of AM-fabricated Mg components is systematically discussed, alongside current limitations and prospective strategies toward their clinical translation. Full article

Laser brazing is commonly used for joining visible automotive body panels where both mechanical integrity and surface quality are required. The present work addresses optimization of a robotic laser brazing workstation intended for prototype vehicle production. During initial commissioning, irregular braze formation was associated with unstable filler wire feeding. Therefore, the wire feeding system was modified and subsequently evaluated together with the influence of laser power and wire feed speed on joint quality under a constant robot travel speed. Experimental joints were produced from electrolytically galvanized DC06 steel using CuSi3Mn1 filler wire. Joint performance was assessed by tensile testing and metallographic examination. Tensile strengths between 293 and 314 MPa were obtained, while fracture occurred exclusively in the base material outside the brazed region. Metallographic observations revealed regular braze geometry for parameter sets A, B and D, whereas excessive thermal input resulted in blowhole formation, zinc coating degradation and enlargement of the heat-affected zone. Quantitative evaluation showed a nearly linear increase in the HAZ area with increasing delivered energy (R² = 0.982). The results indicate that stable brazing conditions can be achieved through an appropriate balance between laser power and wire feed speed under constant robot travel speed conditions. The proposed parameter limits may serve as a practical guideline for robotic laser brazing of thin galvanized automotive sheets under prototype production conditions. Full article

Graphene oxide (GO)-based nanostructured biomaterials have emerged as promising platforms for tissue engineering due to their novel biointeractive properties. In this study, we developed polyamide 6 (PA6) scaffolds by electrospinning using the Nanospider technique. Unlike conventional laboratory-scale electrospinning systems, Nanospider™ employs a wire-based electrode coated with a thin layer of polymer solution, from which nanofibers are continuously generated under a high-voltage electric field, enabling the large-scale fabrication of scaffolds. The scaffolds were then nanostructured with GO to investigate the effect of surface modification on their physicochemical properties, and biological responses. Surface characterization demonstrated that GO incorporation altered the microtexture of PA6 scaffolds, leading to changes in topographical parameters and surface morphology. In vitro studies performed using human stromal HS-5 cells confirmed high cytocompatibility of both GO nanofilms and PA6-GO composites, with preserved metabolic activity and enhanced cell adhesion. Scanning electron microscopy revealed improved spreading, elongated morphology, and increased filopodia formation on GO-modified scaffolds. Gene expression analyses indicated modulation of mechanotransduction- and adhesion-related pathways, including differential regulation of FN1, FAK, and integrin-associated genes, suggesting that GO nanostructuring influences early cell–material interactions through combined effects on surface architecture and chemistry. Ex vivo studies using embryonic tissues derived from chicken embryo Gallus gallus demonstrated effective colonization of connective, cartilage, and bone tissues on GO-modified scaffolds. Collectively, these findings demonstrate that GO nanostructuring of electrospun PA6 scaffolds improves biointerface formation, supports mechanobiological adaptation, and promotes tissue development, highlighting the potential for regenerative medicine. Full article

This study presents a comparative investigation of the microstructure, phase composition, microhardness, tribological behavior, and corrosion resistance of heterogeneous coatings deposited on St3 steel by twin-wire electric arc spraying (TWEAS). Three wire combinations were examined: ER309LSi + Steel 70, Sv-08G2S + Steel 70, and 30KhGSA + ER309LSi. The coatings were characterized using X-ray diffraction (XRD), scanning electron microscopy with energy-dispersive spectroscopy (SEM/EDS), Vickers microhardness testing, ball-on-disc tribological measurements, and potentiodynamic polarization in 3.5 wt.% NaCl solution. All coatings exhibited a characteristic lamellar structure with a thickness of 340–360 μm and hardness values significantly higher than those of the steel substrate. The 30KhGSA + ER309LSi coating demonstrated the highest cross-sectional microhardness (532 ± 13 HV) and the lowest specific wear rate (0.411 × 10⁻⁴ mm³/(N·m)), which was more than five times lower than that of the substrate. The enhanced wear resistance was associated with the formation of the Cr₇C₃ and Cr₂₃C₆ carbide phases, as identified by XRD. The Sv-08G2S + Steel 70 coating exhibited the lowest corrosion rate among the investigated coatings due to its more homogeneous ferritic structure and reduced electrochemical contrast between lamellae. The results demonstrate that the phase composition and distribution of alloying elements play a decisive role in determining the functional properties of heterogeneous TWEAS coatings. Full article

Waste wire harnesses composed of thin copper wires coated with polyvinyl chloride (PVC) are difficult to recycle due to hydrogen chloride (HCl) emission during conventional thermal treatment. In this study, copper recovery from waste wire harnesses was investigated using alkali hydroxide-assisted pyrolysis with sodium hydroxide (NaOH) or potassium hydroxide (KOH) under an inert atmosphere. The coexistent heating with alkali hydroxides enabled the decomposition and carbonization of PVC while effectively capturing chlorine species, thereby suppressing HCl gas release. As a result, thin copper wires were successfully separated and recovered. The addition of alkali hydroxides significantly improved PVC gasification efficiency and copper–PVC separation compared with pyrolysis without alkali hydroxides. No notable differences were observed between NaOH and KOH in terms of chlorine capture or gaseous byproduct formation. These findings demonstrate a simple and effective method for recovering copper from waste wire harnesses without HCl emission. Full article

Lightweight high-entropy alloy (HEA) coatings are highly desirable for advanced surface protection. This study presents a novel fabrication method for Al-Mg-Ti-Cu-Ni-Cr lightweight HEA coatings via laser cladding combined with in situ alloying, using a specially designed cable-type composite wire consisting of an Al-Mg core sheathed with Cu, Ti, Ni, and Cr-Ni wires. The fabricated coatings exhibit homogeneous composition, high microhardness, and excellent corrosion resistance. Notably, the Al_43.5Mg₂Ni₂₈Cu₁₅Ti_11.5 coating achieves a microhardness of 627 HV_0.1 and a corrosion current density of 5.5 × 10⁻⁶ A/cm², while the Al_43.6Mg_2.1Cr_2.5Ni_25.2Cu_15.2Ti_11.4 coating shows 523 HV_0.1 and a lower current density of 2.8 × 10⁻⁶ A/cm². Mechanical analysis reveals that the enhanced hardness stems from synergistic strengthening effects—severe lattice distortion, B2 phase coherent precipitation, and grain refinement. The superior corrosion resistance is primarily attributed to a compact Cr₂O₃ passive film. This work provides a new strategy for designing and additively manufacturing lightweight HEA coatings. Full article

Solar-driven NiTi alloy wire rotary engines are promising for lightweight actuation, but their performance is often restricted by insufficient light absorption of the alloy wire and unstable wheel–wire transmission. In this work, a collaborative surface-modification strategy was developed by combining a CNT/PDA-based photothermal coating on the NiTi alloy wire with a CNT/PDMS-based coating on the wheel surface. To establish a controllable wire-coating process, electrophoretic deposition parameters were first screened on titanium plates using an orthogonal design involving voltage, duty ratio, water content, treatment time, and electrode distance. Among the tested conditions, an electrode distance of 10 mm provided the most favorable balance between coating thickness and microstructural uniformity, while water content and electrode distance were identified as the main factors affecting coating variation. After transfer to the alloy wire, the coating greatly reduced reflectance in the 300–1400 nm range and significantly enhanced photothermal heating, increasing the maximum irradiation temperature by about 30 °C. On the wheel side, PDMS-based surface modification further improved rotational output, and the 1.5 wt% + 10 wt% formulation showed the best performance. In coupled rotation tests, the system with simultaneous wire and wheel modification exhibited the fastest startup and the highest angular velocity, reaching about five times that of the slowest rotating modified group. These results demonstrate that coordinated surface modification of the alloy wire and wheel is an effective route to improving the photothermal response and rotational performance of NiTi alloy wire rotary engines. Full article

Cable wires provide a viable technical pathway for the laser additive manufacturing of high-entropy alloys (HEAs). However, the complex interplay of structural and material parameters of cable wires leads to significant variations in molten pool dynamics, which poses challenges to the fabrication of high-quality HEA coatings. To clarify the effects of these key factors on molten pool behavior, a multi-physics numerical model for the laser cladding of Al₅₀Si₆Ti₈Cr₁₂Cu₁₂Ni₁₂ cable wires was established in this study. A dedicated physical model for cable wires was developed, and the Level Set Method was employed to track fluid interfaces throughout the cladding process. Based on the proposed model, the temperature distribution, stress fields, and elemental homogeneity within the molten pool were systematically investigated. The results reveal that chromium (Cr) addition induces a viscosity reduction, and a torsional pitch of ≤4 mm is critical for achieving defect-free, compositionally uniform HEA coatings, which provides novel insights for process optimization and alloy design of cable-wire laser cladding. Full article

Insulation failure in aviation generator windings is one of the most common faults. Modern aircraft winding materials often employ polyimide enameled wire, making research on its reliability and health monitoring particularly important. Based on the relationship between temperature and aging rate described by the Arrhenius law, this study designed accelerated thermal aging experiments, testing twisted-pair, coil, and winding samples made of copper-core polyimide enameled wire. The variation in multiple parameters was visualized using B-spline fitting, ultimately identifying parallel equivalent capacitance as the most suitable parameter for monitoring generator winding insulation. It was also indicated that aging of the winding insulation coating has almost no effect on the performance of the electrical system. Finally, experimental data were processed using Bayesian nonlinear regression, where prior data were updated with new data to obtain posterior aging curves. When the IC ($C_p$) value reaches 1.2009 and 1.4089 times its initial value, the sample is considered to have reached 50% and 100% of its lifespan, respectively. This provides a reference approach and quantitative indicators for predicting the lifespan of polyimide enameled wire windings. Full article

Wire electrical discharge machining (WEDM) is widely used for the precision cutting of difficult-to-machine materials, including nickel-based superalloys. Wire electrode wear, however, remains a practical limitation, because it affects process stability, wire consumption, and machining cost. This work examines the wear behaviour of a gamma-phase Cu₅Zn₈-coated copper-core wire electrode (Elecut X, ø 0.25 mm) during the WEDM of Inconel 718 using direct gravimetric measurement. A 3³ full factorial experiment was carried out with three electrical parameters: pulse-on time (A), pulse-off time (B), and servo reference voltage (Aj). The discharge process was monitored with an oscilloscope so that measurements only started after the programmed pulse-off time had been reached. Electrode wear was evaluated as the mass loss Δm of 4 m wire segments after 5 min cutting intervals on a Charmilles Robofil 310 machine, and factor significance was assessed by analysis of variance (ANOVA). Pulse-on time was the dominant factor, accounting for 88.45% of the total variation in Δm, followed by servo reference voltage and pulse-off time. SEM/EDS examination showed material transfer from the Inconel 718 workpiece to the worn electrode surface, with local nickel content reaching 16.84 wt.% on the frontal face of the most worn sample. The results provide a quantitative basis for reducing wire consumption during the WEDM of Inconel 718 while recognising the trade-off with cutting productivity. Full article

This study utilized a twisted wire rotating arc cladding method to in situ fabricate a Fe-containing multi-principal element alloy (HPEA) coating derived from NiCrCoTiMo stranded wire on 45 steel (equivalent to AISI 1045 steel). The macroscopic morphology, microstructure, mechanical properties, and electrochemical corrosion behavior of the prepared coatings were examined. The coating exhibited no visible cracks or pores and displayed a dual-phase face-centered cubic (FCC) + body-centered cubic (BCC) structure, with an average grain size of 78 μm for the FCC phase and 1 μm for the BCC phase. The microhardness of the coating is approximately 381.3 HV_0.1. Compared to 45 steel, the coating’s coefficient of friction (COF) decreased from 0.6265 to 0.5125, representing an 18.2% reduction. The calculated wear rate of the coating was 1.47 × 10⁻⁵ mm³/N·m, approximately six times lower than that of 45 steel (8.93 × 10⁻⁵ mm³/N·m). Electrochemical testing revealed that the coating’s open-circuit potential (OCP) was −0.405 V vs. the saturated calomel electrode (SCE), with a corrosion potential (E_corr) of −0.556 V vs. SCE and a corrosion current density (I_corr) of 4.458 × 10⁻⁶ A/cm². In comparison, 45 steel exhibited an OCP of −0.582 V vs. SCE, with corrosion parameters of E_corr = −0.840 V vs. SCE and I_corr = 1.302 × 10⁻⁵ A/cm². These results demonstrate the superior corrosion resistance and wear performance of the coating, underscoring its potential for applications in challenging environments that demand enhanced material durability. Full article

Thermal spray technologies are widely used in aerospace, gas turbine, and automotive industries, where nickel-based superalloys are valued for their mechanical strength and resistance to oxidation and corrosion at elevated temperatures. This study investigates the microstructure and tribological performance of Ni–5Al/Inconel 625 composite coatings deposited on AISI 1025 steel using wire arc spraying, aiming to provide a cost-effective alternative to bulk superalloys and more advanced thermal spray techniques. Microstructural characterization was performed using optical microscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy, while surface roughness, microhardness, and dry sliding wear behavior were evaluated using ball-on-disk tests against Al₂O₃ counter-bodies. Confocal microscopy and three-dimensional triboscopic imaging were employed to analyze wear-track morphology and friction behavior. X-ray diffraction (XRD) analysis confirmed the presence of a predominantly intermetallic Ni₃Al (γ′) phase with secondary NiAl in the bond coat, indicating significant interdiffusion between the NiAl bond coat and the Inconel 625 top coat. The top coat exhibited a face-centered cubic (FCC) γ Ni-based solid solution. The coatings exhibited a typical lamellar structure with low porosity (2%–3%) and oxide content of 12%–15%, primarily chromium and niobium oxides located at splat boundaries. Abrasion, combined with interlamellar decohesion, was identified as the dominant wear mechanism. Post-deposition polishing reduced surface roughness from 11.9 µm to 2.12 µm, leading to a 2.5-fold reduction in wear volume and a significant decrease in debris pile-up. The corresponding specific wear rates were approximately 9.3 × 10⁻⁵ mm³/Nm and 3 × 10⁻⁵ mm³/Nm for the as-prepared and polished conditions, respectively, which are within the range reported in the literature for similar coatings. These findings demonstrate that wire arc-sprayed Ni–5Al/Inconel 625 coatings, particularly after polishing, offer improved wear resistance while maintaining cost-effectiveness, making them a promising alternative for tribological applications. Full article

The high-rate recycling of scrap steel introduces persistent residual copper (Cu), which accumulates at prior austenite grain boundaries at the surface, during high-temperature reheating, leading to Cu-induced sensitization and deleterious “hot shortness”. To address this, a predictive analytical framework was derived using Fick’s Second Law and the Sekerka, Jeanfils, and Heckel (SJH) approach to model the dissolution of Cu-rich films as a 1D planar moving boundary problem. The validity of this analytical framework was first established through experimentation on controlled Cu-coated steel wire rods, where theoretical concentration profiles showed strong agreement with empirical depth profiles. When applied to a 0.21 wt.% Cu steel at 1000 °C, the model predicted a critical extinction time (t*) of approximately 8.57 min for the complete dissolution of a 20 nm sensitized film. Experimental trials on sensitized wire rods confirmed this prediction, demonstrating an 89% reduction in the frequency of detectable sensitized zones and a significant decrease in zone width following a 10 min thermal dwell. The approach provides a standardized, scalable, and composition-adaptable methodology, grounded in a 1D planar approximation, for optimizing desensitization heat treatments across a range of Cu contents, offering a practical strategy to increase scrap steel utilization while mitigating hot shortness. Full article

Wire laser cladding (WLC) of bronze on stainless steel offers a promising approach for combining the structural strength of steel with the superior tribological and corrosion properties of copper alloys. In this study, the influence of key process parameters, including wire preheating current, deposition speed, laser power, and wire feed speed on melt pool temperature and clad geometry was investigated using response surface methodology (RSM). Experiments were performed using a robot-assisted coaxial wire feeding laser cladding system, and real-time thermal monitoring was conducted using an infrared camera. The results showed that defect-free bronze clads with good metallurgical bonding and limited dilution were achieved across the investigated parameter range. Statistical analysis revealed that melt pool temperature is primarily governed by laser power and deposition speed, with a significant interaction between these parameters. Clad height was mainly influenced by wire feed speed and deposition speed, whereas clad width was controlled by laser power and deposition speed. The side angle was affected by deposition speed, laser power, and wire feed speed, reflecting the balance between vertical buildup and lateral spreading. Overall, the study demonstrates that stable and high-quality clads can be achieved by properly balancing energy input and material supply. The developed models provide valuable insight for optimizing process parameters in wire laser cladding of bronze on stainless steel. Full article

Metal mesh reflective surfaces are widely used in deployable antennas mounted on satellites where lightweight and stowability are required; however, quantitative characterization of reflective performance is difficult due to complex woven/knitted structures. This paper presents a modeling method that characterizes the reflection coefficient of complex mesh fabrics by combining a per-band effective wire radius r_eff estimation procedure with the Casey surface impedance model. The lattice spacing is fixed from the specimen geometry, the electrical conductivity is set to the material property of gold ($\sigma$ = 45.2 MS/m), and r_eff is determined as a single parameter that minimizes the error against the measured reflection coefficient in each frequency band. For validation, waveguide-contact measurements were performed on three Atlas-series mesh specimens fabricated with gold-coated molybdenum wire (diameter: 30 μm), measuring each specimen across all three waveguide standards (WR-340, WR-90, WR-28) with nine repeated trials per configuration, totaling 162 measurement runs. The estimated r_eff ranged from 10.1 to 44.5 μm depending on band and polarization, with RMSE below 0.021 dB in all native-band fits. Even for the same specimen, directional r_eff values differed by up to 1.78× due to the anisotropy of the weave structure, confirming that polarization dependence must be considered in mesh reflector antenna design. Full article