Search Results (222)

Al_0.2CoCrFeNi-5%WC high-entropy alloy (HEA) composites were fabricated via spark plasma sintering at temperatures ranging from 900 °C to 1050 °C, and the effects of sintering temperature on phase constitution, microstructure, and mechanical properties were systematically investigated. The results show that all composites consist predominantly of an FCC matrix, WC, M₂₃C₆ and M₆C carbides. With increasing sintering temperature, interfacial reactions are promoted, leading to the progressive consumption of WC and an increase in carbide content. The composite sintered at 1000 °C achieves the optimal combination of properties, with a relative density of 96.8%, a yield strength of 468 MPa, an ultimate compressive strength of 1871 MPa, and a fracture strain of 43.6%. The outstanding strength–ductility synergy originates from near-full densification, robust interfacial bonding, and multiple carbide strengthening mechanisms. Excessively high sintering temperature (1050 °C) results in reinforcement coarsening and degradation of mechanical properties. Full article

High Velocity Oxy-Fuel (HVOF) thermal spraying enables the deposition of dense coatings with low porosity, high hardness, and good fracture resistance. Tungsten carbide–cobalt (WC-Co) coatings are widely used in industrial and aerospace applications due to their excellent wear resistance; however, improving crack resistance and coating–substrate adhesion remains a key challenge. In this study, WC-Co+Ni composite coatings were deposited on ductile cast iron, with emphasis on the role of Ni addition in controlling microstructure development under HVOF conditions. Microstructural characterization was performed using optical, scanning, and transmission electron microscopy (OM, SEM, TEM), while phase composition and chemical analysis were determined by X-ray diffraction (XRD) and energy-dispersive spectroscopy (EDS). The coatings exhibited a dense, low-porosity microstructure composed of fine WC and W₂C carbides embedded in a Co–Ni binder, with locally nanocrystalline regions. XRD analysis confirmed WC and W₂C as the dominant phases, with weak reflections corresponding to the η-phase (Co₆W₆C), indicating local decarburization. The addition of Ni increases the fraction of the transient liquid phase during particle flight, enhancing carbide dissolution and mass transport in the binder, which accelerates decarburization kinetics and promotes η-phase formation. Simultaneously, Ni modifies the binder into a more ductile Co–Ni matrix, reducing the detrimental effect of brittle η-phase on coating integrity. Mechanical and tribological testing (instrumented indentation and scratch testing) demonstrated improved crack resistance, wear resistance, and adhesion. The results show that Ni addition enables process-driven microstructural tailoring of HVOF-sprayed WC-Co coatings, leading to enhanced performance despite the presence of η-phase. Full article

With the continuous increase in the manufacturing cost of conventional WC-Co cemented carbides, the development of low-cost, high-performance cobalt-free or low-cobalt cemented carbides has become a research hotspot in the industry. In this study, cobalt-free WC-Ni-Fe-Mo cemented carbides were successfully prepared by low-pressure sintering using fine WC powder as the raw material and Ni-Fe-Mo as the composite binder phase. The effect of Mo content variation on the microstructure, mechanical properties, and friction and wear properties of the alloys was systematically investigated. The results show that the as-prepared alloys consist of a two-phase structure composed of WC phase and γ-(Fe, Ni) phase. The addition of Mo further leads to the formation of Mo₂C and Ni₃W₃C phases. With increasing Mo content, the average WC grain size gradually decreases from 0.45 μm to 0.31 μm, and the grain size distribution becomes more uniform. Meanwhile, the alloy density gradually decreases, hardness gradually increases, fracture toughness decreases, and transverse rupture strength first increases and then decreases. Affected by the brittle Ni₃W₃C phase, the wear resistance of the alloys gradually deteriorates. When the Mo content is 0.25 wt%, the alloy exhibits the best comprehensive performance, with a transverse rupture strength of 4078 MPa, a hardness of 90.5 HRA, a fracture toughness of 12.11 MPa·m^1/2, and a friction coefficient of 0.42. This indicates that an appropriate addition of molybdenum has a significant strengthening effect on the mechanical properties of the material, thereby laying an experimental foundation and providing process guidance for the development of novel low-cost, high-performance cobalt-free cemented carbides. Full article

WC–Co composites are widely applied in various industries due to their high hardness and wear resistance. The addition of zirconia further enhanced the composite, improving grain refinement and reducing the friction coefficient. Zirconia submicron particulate reinforcement strengthened the cobalt binder phase, significantly improving the wear resistance. Tribological tests were performed in ball-on-flat dry sliding mode, against an Al₂O₃ counter body. The specimen WC–6Co–10ZrO₂ exhibited a decrease in volumetric loss ΔV by 66% compared to 94WC–6Co composite, and the wear rates W_s showed a 50% decrease for 4 wt.% zirconia addition and up to 80% when 10 wt.% ZrO₂ was added. In tribological tests, a five times larger load, 100 N instead of 20 N, caused an increase in the wear rate 1.1, 1.3, and 1.9 times for WC–Co, WC–6Co–4ZrO₂, and WC–6Co–10ZrO₂ compositions, respectively. Abrasive and adhesive wear mechanisms were identified. Full article

Carbon-fiber-reinforced polymer (CFRP) components commonly require milling to achieve final dimensional accuracy and surface integrity, yet tool selection remains a trade-off between surface quality, process load, and cost. This study compared two industrial tool concepts for CFRP side milling under matched cutting conditions: a WC-Co compression-type end mill and a PCD end mill. A two-factor central composite design with 13 parameter sets was used, and tool effects were evaluated through paired differences in Ra_mean, Rz_mean, and F_xy,RMS. The PCD tool significantly improved surface quality, with mean paired differences of −2.00 µm for Ra_mean and −6.67 µm for Rz_mean, while increasing F_xy,RMS by 14.86 N relative to WC-Co. Response-surface analysis showed that the roughness advantage of PCD was broadly stable across the investigated process window, whereas the force penalty was nonlinear and was best described by a second-order CCD model (R² = 0.820, model p = 0.015), with a significant quadratic cutting-speed term. Scenario-based decision analysis further showed that PCD was preferred in 12 of 13 DOE points under quality-driven weighting, whereas WC-Co was preferred in all 13 points under cost-driven weighting. The results indicate that PCD is the preferred quality-oriented solution for CFRP side milling, while WC-Co remains advantageous when lower load or lower cost is prioritized. Full article

This study centred on the parametric optimisation and performance prediction of NiCr/WC-Co coatings produced by high-velocity oxygen fuel (HVOF) spraying. An L18 orthogonal experimental design based on the Taguchi method and the response surface method (RSM) was adopted to examine how key process parameters affect the microstructure, phase composition and hardness of the coatings. The results revealed that analysis of variance (ANOVA) indicated that travel speed, methane flow rate, powder feed rate, and stand-off distance were the primary parameters affecting coating hardness, collectively accounting for 76.25% of the total variance. Also, the RSM model established in this study demonstrates remarkably high predictive accuracy, with a coefficient of determination (R²) of 0.985 and an average prediction error of just 1.16%. Verification experiments were also conducted under optimal conditions. The measured hardness was 1352.7 ± 75 HV, in close agreement with the predicted value of 1365 HV. The coating, which was applied using HVOF spraying, had a dense layered structure and low porosity, and the decarburisation of the tungsten carbide was extremely minimal. In addition, interfacial bonding is improved and structural defects are reduced by the addition of a NiCr intermediate layer. It is demonstrated by the results that the Taguchi-RSM method is reliable for the optimization of HVOF spraying parameters and the prediction of coating hardness. Full article

Tungsten carbide and cobalt cutting tools require low surface roughness to improve cutting performance by reducing the wear from machining friction. While this is achieved by conventional manufacturing processes (pressing and sintering, grinding), with additive manufacturing processes it is more difficult (layer height, printing strategy). Since less costly and more sustainable solutions (without lubricants) are being studied as alternatives to conventional processes, a complementary technology (laser ablation) is suggested for the additive manufacturing of green WC-10Co. In this study, material extrusion (MEX) was used to produce green WC-10Co 3D objects, followed by laser ablation (50 W ytterbium fiber laser, 800–1100 nm wavelength) on their surface. Different laser strategies and parameters (power, speed, frequency, distance between lines, number of passages) were tested to find the most suitable. Most combinations were excluded by initial visual inspection, while the best ones were measured with a contact and non-contact profilometer. Further analysis was made on the composition and microstructure (with techniques such as Raman spectroscopy, scanning electron microscope, x-ray diffraction, and hardness indentation) to study what the interaction with the laser changed on the surface. Results show that with a combination of 50 W laser power, 1000 mm/s laser speed, 2000 kHz laser frequency, 0.1 mm distance between lines and three laser passages, it was possible to achieve a surface roughness of 0.6 µm (Sa) for the sintered WC-10Co, produced by MEX. No η-phase and graphite were detected, as well as microporosity and fissures. Full article

CoNiV medium-entropy alloy (MEA) composite coatings reinforced with 40 wt.% tungsten carbide (WC/W₂C) particles were fabricated on carbon steel via laser cladding under nominal heat inputs ranging from 75 to 150 J/mm. The phase constituents and microstructural evolution were investigated, revealing that the coatings were primarily composed of an FCC matrix, retained WC/W₂C particles, and in situ formed V-rich and VWC₂ carbides. While the phase compositions remained generally consistent, the features of the reinforcement architecture varied with the extent of WC/W₂C dissolution governed by laser heat inputs. At low heat inputs, limited particle dissolution yielded sparsely distributed in situ carbides, whereas excessive dissolution at high heat inputs promoted the agglomeration of dense and coarse carbides, driving the microhardness to peak at 570.5 HV_0.5. However, the coating deposited at 150 J/mm exhibited compromised wear resistance due to the fragmentation and detachment of these coarse carbides, which intensified abrasive wear. In contrast, moderate dissolution at intermediate heat input (100 J/mm) facilitated the formation of fine in situ carbides in interparticle regions. This resulted in a homogeneous multiscale synergistic reinforcement microstructure that endowed the coating with optimal wear performance. By precisely controlling heat input to regulate in-situ precipitation, this study established a solid foundation for tailoring wear resistance and expanding the application of composite coatings. Full article

The demanding operational requirements of ultra-deep oil and gas exploration present formidable challenges for material performance, necessitating the development of novel cemented carbides that combine high strength-toughness with exceptional corrosion resistance. In this study, Cr₂(C,N) was employed as a grain inhibitor to introduce N into the dual-scale structured WC-Co cemented carbide system for the fabrication of novel cemented carbides. The effects of Cr₂(C,N) addition on the microstructural organization, mechanical properties and corrosion resistance behavior were systematically investigated. The experimental results show that the addition of Cr₂(C,N) effectively prevents the direct contact of these coarse WC grains and allows more fine WC grains to be retained to fill the regions between these coarse WC grains and the Co binder phase, thereby suppressing Co pool formation and resulting in a continuous and uniform Co binder network. When the addition amount of Cr₂(C,N) reaches 0.6 wt.%, the dual-scale structured cemented carbide achieves the optimal comprehensive mechanical properties, with a transverse rupture strength of 3182.3 MPa, a fracture toughness of 18.68 MPa·m^1/2, and a hardness of 1140.4 HV₃₀. Meanwhile, the optimization of microstructure, the formation of a passive film, and the stabilization of the fcc-Co phase jointly contribute to the superior corrosion resistance of this composition. Full article

Efficient joining of hard metals to steels is crucial for supporting sustainable manufacturing under emissions strategies to minimize CO₂. CoNiCrFeCu high-entropy alloy containing scandium (Sc) was designed as a filler for laser braze-welding of WC-Co and steel. The designed compositions with different Sc levels were melted and cast in a high-vacuum non-consumable arc furnace. The results showed that the as-cast microstructure was a complex mixture of a networked Ni₂Si, elongated Cr-Fe-Co solid-solution phase, and Fe-Ni-Co-Cu solid-solution phase. Scandium was shown to have formed compounds with nickel/cobalt and copper. The TG-DSC analysis confirmed that the melting points of the designed compositions were between 973.7 °C and 981.5 °C. The maximum spreading area of the CoNiCrFeCu-0.9Sc composition on AISI 1045 steel was 64.83 mm², and on the WC-Co cermet it was 78.63 mm². The interface between the fusion zone and AISI 1045 steel exhibited an epitaxial growth of dendrites from the steel base metal. The interface between WC-Co and the fusion zone exhibited a partial penetration of brazing filler into the Co matrix, forming a metallurgical bonding between the dissimilar materials. Sc, as an alloying element in the filler metal, enhanced the bond formation because it decreased the solidus temperature and increased wetting. Full article

Background/Objectives: Down syndrome (DS), the most common chromosomal disorder, is associated with obesity and related metabolic complications. Although physical activity (PA) improves health outcomes in individuals with DS, global research trends in this field have not been systematically synthesized, and evidence regarding the effects of aerobic training (AT) on obesity-related parameters in individuals with DS remains inconsistent. This study incorporated a dual bibliometric and meta-analytical approach. Methods: First, the bibliometric analysis included 321 original research articles published between 2001 and 2024, retrieved from Scopus, Web of Science, and PubMed. Second, a meta-analysis of 15 randomized controlled trials (n = 477) was conducted to examine the effects of AT on obesity-related parameters, including body weight (BW), body mass index (BMI), fat mass (FM), waist circumference (WC), and waist-to-hip ratio (WHR) in individuals with DS. Results: Keyword co-occurrence and collaboration network analyses revealed a notable increase in research output since 2018, with “adolescent,” “obesity,” and “intellectual disability” the most co-occurring keywords associated with DS and PA. “Obesity” emerged as the most prominently growing keyword associated with DS and PA. A meta-analysis concluded that AT reduced FM (standardized mean differences [SMD] = −0.44; p < 0.001) and WC (SMD = −0.39; p < 0.01), while subtle changes in BW, BMI, and WHR were found. These findings suggest that AT improves body composition, particularly reducing central adiposity, even without changes in traditional weight-based metrics. Conclusions: Our findings demonstrate that AT can be an effective non-pharmacological strategy for improving body composition in individuals with DS and obesity and highlight the urgent need to shift clinical and research paradigms toward multidimensional, individualized health strategies that support PA and healthy body composition throughout the lifespan. Full article

Atmospheric plasma spraying (APS) represents a critical solution for enhancing the durability of agricultural components, such as harrow discs, which are subjected to synergistic wear and corrosion during soil cultivation. This study presents experimental results evaluating the electrochemical corrosion behavior and thermal shock resistance of discs coated via atmospheric plasma thermal spraying. Both metallic and ceramic materials, in powder form, from established manufacturers were used to produce the coatings, and the three types of coatings (two metallic and one ceramic) have the following chemical compositions and trade names: W₂C/WC12Co (Metco71NS), Cr₂O₃-4SiO₂-3TiO (Metco136F) and Co25.5Cr10.5Ni7.5W0.5C (Metco45C-NS). The coatings were analyzed using electron microscopy to evaluate the surfaces following corrosion testing. The ceramic coating based on the Cr₂O₃-4SiO₂-3TiO demonstrated the highest protective efficiency by increasing the charge transfer resistance from 307 Ω/cm² to 2213 Ω/cm² for the ceramic coating. It provided a superior physical barrier, reducing the corrosion current density from 0.140 mA/cm² for unprotected substrate to 0.004 mA/cm², representing an improvement of nearly two orders of magnitude. These findings demonstrate that implementing Cr₂O₃-4SiO₂-3TiO ceramic systems can significantly extend the operational lifespan of soil-engaging components, providing a cost-effective strategy for reducing maintenance intervals and material loss in aggressive agricultural environments. Full article

The design and main parameters of a plasma–chemical reactor containing two compartments are presented. One compartment houses a vacuum-arc evaporator, while the other houses a planar magnetron. The compartments are separated by a diaphragm with a dosing slot for injecting copper vapor into the TiN synthesis compartment. The conditions for the synthesis of superhard TiN-Cu composite coatings are experimentally determined. Based on established process parameters for TiN synthesis in a nitrogen-containing plasma by Ti evaporation using a vacuum-arc discharge, it is proposed to apply TiN-Cu coatings by injecting Cu vapor into the TiN synthesis area and sputtering Cu using a magnetron discharge. XRD analyses of both TiN and TiN-Cu coatings show the presence of WC, Ti₂C, and TiN. EDS analysis confirms 5.57 at. % copper on the surface of the TiN-Cu coating. Real-life operating tests of TiN-Cu coatings on replaceable WC-TiC-Co (79/15/6 wt.%) alloy hexagonal inserts used for cutting 40Kh steel revealed that applying the TiN-Cu coating extends the tool life of WC-TiC-Co inserts by about 2.5 times compared with uncoated tools. Cutting force measurements on TiN-Cu-coated inserts showed no vibration or noise during cutting, driven by a reduced friction coefficient and improved heat dissipation at the contact zone between the cutting edge and the workpiece, thereby lowering the temperature in that area. Full article

This review provides a comprehensive overview of high-wear-resistant metal–ceramic surface engineering technologies based on Directed Energy Deposition (DED) for high-temperature industrial applications. In high-temperature processes such as continuous hot-dip coating, critical components (e.g., rollers and sleeves) are exposed to severe wear and chemical reactions, leading to rapid degradation and frequent replacement, which results in significant economic losses. This review focuses on the fundamental characteristics of DED processes and their advantages over conventional surface modification techniques such as HVOF, PVD/CVD, and arc-based methods. Particular attention is given to the process–structure–property relationships governing coating performance, including coating thickness, bonding characteristics, and high-temperature stability. Representative material systems, particularly WC-based metal–ceramic composites (e.g., Co–WC), are systematically discussed in terms of their wear resistance and applicability under severe operating conditions. Quantitative tribological performance metrics, including wear rate and friction coefficient, are also reviewed to provide a more rigorous understanding of coating performance. The analysis highlights that DED offers unique advantages in achieving thick coatings with strong metallurgical bonding and high applicability to repair and remanufacturing of large-scale components. In addition, recent advances in DED technologies, such as closed-loop control, self-regulating effects, and data-driven process optimization, are examined to highlight emerging trends in the field. The review also identifies current technical limitations and outlines future research directions, emphasizing the need for improved process control, defect mitigation, and integration of advanced monitoring techniques. Full article

The research conducted in this paper is a practical example of the Design of Experiments methodology. In accordance with the assumptions of the experimental design, the authors drew attention to the problem: how should the spark plasma sintering process be planned to obtain the maximum amount of information needed to optimise the consolidation of the WC-6Co composite at the lowest possible cost? The DOE methodology—a powerful technique for investigating new processes and gaining knowledge about existing ones in order to optimise them for high performance—was employed in the study. The aim of the research was to optimise the consolidation of the spark-plasma sintering process of the WC-6Co composite using the DoE (Design of Experiments) methodology. Four sintering factors were selected for the study: sintering temperature (factor A, 1300–1400 °C); heating rate (factor B, 100–300 °C/min); sintering time (factor C, 150–600 s); and pressure (factor D, 40–50 MPa). Each consolidation factor was designed to cover three levels. The L9 orthogonal array was used. It was found that sintering temperature and heating rate had the greatest impact on apparent density. To validate the statistical model, sintering tests were performed at a temperature of 1380 °C, a heating rate of 100 °C/min, a sintering time of 150 s and a pressing pressure of 45 MPa. Validation analysis of the statistical model demonstrated consistency with the experimental results. The WC-6Co composite achieved an apparent density of 14.85 g/cm³, corresponding to 97.42% of the theoretical density, with a hardness of 1809 HV30 and total porosity of 2.583%. X-ray diffraction studies revealed the presence of tungsten carbide and cobalt in the structure. Full article