Search Results (517)

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

This paper presents a practical implementation of relative primary radiation thermometry (RPRT) together with MultiFixRadSoft, an open-source software package developed in accordance with the Mise-en-Pratique for the kelvin (MeP-K) for realization of the thermodynamic temperature scale and uncertainty evaluation under the new definition of the kelvin. The software enables realization of temperature scales using ITS-90 metal fixed points as well as metal–carbon and metal–carbide–carbon eutectic high-temperature fixed points (HTFPs) for both radiation thermometers and radiometers. It incorporates automated routines for melting plateau analysis, including determination of the point of inflection, liquidus point, and melting range, together with correction modules for size-of-source effect, detector nonlinearity, emissivity, and temperature drop. Validation is demonstrated through experimental realization using six fixed points (Cu, Fe–C, Co–C, Pd–C, Ru–C, and WC–C) and a linear radiation thermometer. The software also supports ITS-90 extrapolation procedures and flexible calibration schemes (n = 1 to n ≥ 3), with automated Sakuma–Hattori fitting and full uncertainty propagation compliant with MeP-K requirements. The results show excellent agreement with manual analyses and published data, confirming the correctness of the implemented algorithms. By integrating data processing, scale realization, and uncertainty analysis within a unified and transparent framework, MultiFixRadSoft provides a robust and accessible tool for traceable radiometric thermometry, supporting emerging NMIs and industrial laboratories while promoting the wider adoption of primary thermodynamic temperature realization methods. 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

This work explores the effect of nitrogen ion implantation on the wettability of the cemented tungsten carbide–cobalt (WC–Co) tool surface used for wood-based panel machining. Nitrogen ions with an energy of 50 keV and a fluence of 1 × 10¹⁷ and 5 × 10¹⁷ cm⁻² were implanted into the surface layer of commercially available WC–Co indexable knives using the implanter without a mass-separated ion beam. The wettability was characterized by a contact angle instrument. The implantation of nitrogen ions into WC–Co tools caused a statistically significant and practically useful decrease in the contact angle. This obtained effect was dependent on the fluence of the implanted ions, and it changed over time. This effect may also explain the transfer from the workpiece and the surface capture of carbon atoms in the secondary structure formed during the machining of wood materials on tools with ion implantation. On the other hand, the layer of carbon on the surface of the tool formed during machining explains the reduction in friction coefficient observed in experiments and the increase in tool life during cutting. Full article

This study investigated the properties of a composite NiCrFeSiB coating with fine-dispersed WC additives, deposited by the HVOF method. The NiCrFeSiB powder alloy with WC additives was applied to a steel substrate. The WC content in the coating was 10, 15, and 20% by weight. The particle size distribution of the mixture ranged from 3 to 10 µm. The WC used was the WC8 alloy (92% WC, 8% Co). The levels of stress, phase composition, hardness, wear resistance, and coating structure were investigated. The studies revealed that the structure was primarily composed of the γ-Ni-Fe solid solution phase, with secondary phases including Ni₃B, Fe₃B, (Cr,)₂B, and carbides of the W₂C, WC, M₇C₃ type. A small amount of the initial WC particles was also present. The use of a fine-dispersed NiCrFeSiB powder mixture with WC particles resulted in a nearly twofold increase in hardness and wear resistance compared to the same parameters of the coating without WC. The coating with 20% WC exhibited the highest hardness. However, its wear resistance was lower than that of the coating with 15% WC. This fact could be explained by a slight difference in the phase composition and an increase in the proportion of the unsolidified WC phase in the structure. This led to the spalling of fine particles and a reduction in wear resistance. The study demonstrated the feasibility of using a fine-dispersed NiCrFeSiB coating with WC additives without additional remelting. Similar hardness and wear resistance results were achieved immediately after HVOF spraying when using a fine-dispersed NiCrFeSiB + 15% WC/Co mixture with a 92/8 composition. This simplification of the technology reduced the coating application process time. It also lowered production costs by eliminating the remelting stage. Full article

To facilitate the next generation of renewable energy devices, it is important to engineer oxygen reduction reaction (ORR) catalysts that balance efficiency and production costs. This work examines oxygen adsorption on the WC (0001) surface as a function of electrode potential, utilizing DFT simulations with an implicit solvent environment. The results demonstrate that electrode potential significantly influences oxygen adsorption energy and electronic structure. Among the adsorption sites examined, the top site exhibits the highest stability across the entire potential range. The observed reduction in adsorption energy at lower potentials is attributed to the d-band center moving further from the Fermi energy, which weakens C–O orbital interactions, as revealed by DOS and COHP analyses. Our results demonstrate the crucial role of electrochemical conditions in modulating catalytic behavior and provide valuable insights for optimizing tungsten carbide (WC)-based electrocatalysts for ORR applications. Full article

Cemented carbides are essential in applications requiring exceptional hardness and wear resistance. However, the reliance on cobalt as a binder raises concerns related to cost, supply security, and health. High-entropy alloys (HEAs) are promising cobalt-free binders offering favorable mechanical properties and potential grain-growth control. This work presents a new approach for the development of Co-free WC-based cemented carbide employing an HEA binder designed through CALPHAD-guided simulations. An optimized composition corresponding to Al5Cr5Cu10Fe35Mn10Ni35 (at%) alloy is predicted to be FCC-dominant with minimal σ-phase formation and good compatibility with WC. A preliminary batch of powder of the proposed binder was produced by blending elemental powders, arc remelting, and ultrasonic atomization, yielding predominantly spherical particles with a dendritic microstructure. WC–HEA composites (WC–12 wt% HEA) were then prepared by ball milling, pressing, vacuum sintering, and sinter-HIP for a first evaluation of the microstructure and achievable hardness. The microstructure exhibited residual porosity without significant WC grain coarsening. XRD analyses showed the dominant presence of WC, along with FCC and M₃W₃C phases (M mainly Fe and Mn), indicating thermal interaction between the binder and WC. Despite these effects, the composite achieved a hardness of 1913 HV and retained a fine WC grain size (0.86 μm). The proposed design approach allowed the definition of a promising Co-free binder composition based on HEA with the expected microstructure, which will need further evaluation, especially aimed at investigating toughness properties as a function of the WC content. Full article

To produce strong and wear-resistant tools for the rock drilling industry, the most commonly used metal matrix composites contain the reinforcing phase of cemented carbide. There are numerous research reports on attempts to improve the performance of WC-Co composites. The paper is a continuation of previously reported research on the SPS-processed WC–6 wt.%Co metal matrix composites with yttria-stabilized zirconia (YSZ) addition in amounts of 4 wt.% and 10 wt.%. The sintered specimens were polished and underwent the microindentation tests with a Vickers shape diamond tip. The following parameters were measured: stiffness S, the Poisson number ν, indentation creep C_IT, relaxation R_IT, indentation hardness H_IT, indentation Vickers hardness HV_IT, Martens hardness HM, reduced modulus E*, and indentation elastic modulus E_IT. The tests revealed hardness values of 16.2–17.0 GPa and indentation elastic moduli in the range of 607–670 GPa. Moreover, respective plastic and elastic parts of the indentation work W_plast and W_elast were determined. It was found that YSZ addition slightly reduced hardness and modulus, but all the three wear parameters, H/E, H³/E², and 1/(E²H), increased after addition of zirconia. Specifically, for 10 wt.% ZrO₂ H/E increased by 5%, H³/E² by 7%, while 1/(E²H) by 27% compared to 94WC–6Co composition. Full article

Three types of gradient plasma-assisted chemical vapour deposition (PACVD) coatings were produced on WC-Co hardmetal substrates: a TiN coating, a gradient TiCN coating with alternating TiN/TiCN layers and a multilayer TiBN system of TiN/TiB₂ layers. Their corrosion behaviour in a chloride environment was compared using direct current and alternating current electrochemical techniques. Potentiodynamic polarization, linear polarization and electrochemical impedance spectroscopy were carried out in 3.5 wt.% NaCl at temperature 20 ± 2 °C in a three-electrode cell with a saturated calomel electrode (SCE) reference. After 1000 s open circuit stabilization, TiN coating showed superior corrosion resistance with E_corr = 15 mV vs. SCE, versus TiCN (E_corr = −281 mV) and TiBN (E_corr = −304 mV). Linear polarization resistance/Tafel analysis showed significantly higher polarization resistance of TiN (R_p = 1559 kΩ∙cm²) than TiCN (195.4 kΩ∙cm²) and TiBN (243.6 kΩ∙cm²), with the lowest corrosion current density, j_corr = 10.97 nA∙cm⁻² and corrosion rate v_corr = 117.2 × 10⁻⁶ mm∙y⁻¹. TiCN showed the highest j_corr (360.8 nA∙cm⁻²) and v_corr (3.32 × 10⁻³ mm∙y⁻¹). Electrochemical impedance spectroscopy fitting with a R(QR) circuit confirmed this, with the highest charge transfer resistance at the substrate–electrolyte interface (R_ct) for TiN (8.198 × 10⁴ Ω∙cm²), lower for TiBN (7.929 × 10⁴ Ω∙cm²) and lowest for TiCN (1.435 × 10⁴ Ω∙cm²), indicating TiN as the best barrier and TiCN as the most permeable. Full article

Water scarcity is increasingly challenging greenhouse tomato production, particularly in Mediterranean and semi-arid regions where irrigation water availability is becoming progressively limited. This study evaluated whether a superabsorbent polymer (SAP) can support water-saving irrigation in tomato grown in coconut fibre. Plants were cultivated in pots under four irrigation amounts (100, 75, 50, and 25% of crop water requirement—WC) combined with two SAP levels (0 and 2 g L⁻¹). Irrigation was managed by a lysimetric control system. Reducing irrigation decreased total fruit yield (averaged across SAP treatments) from 100% WC (1212 g plant⁻¹) to 50–25% WC (914 and 624 g plant⁻¹, respectively), while non-marketable fruit number was unchanged (15.4 fruit plant⁻¹, on average). SAP increased total yield, averaged across irrigation treatments (from 925 to 1022 g plant⁻¹), and marketable fruit number (from 26.3 to 32.3 fruit plant⁻¹), without affecting unitary fruit weight (20.4 g fruit⁻¹, on average). SAP also increased net photosynthesis (from 16.0 to 17.4 µmol CO₂ m⁻² s⁻¹), while stomatal conductance (0.14–0.15 mol H₂O m⁻² s⁻¹) and WUE (4.0 µmol CO₂ mmol⁻¹ H₂O) were not affected by SAP. Total soluble solids increased under severe deficit (7.8 °Brix at 25% WC) and were enhanced by SAP (from 6.9 to 7.6 °Brix), while colour parameters were mainly driven by irrigation. Overall, the irrigation amount was the primary driver of performance. Moderate deficit irrigation (75% WC) maintained a marketable fruit number and total fruit weight comparable to full irrigation (100% WC). SAP amendment acted as a complementary tool to improve marketable production and net photosynthesis across irrigation levels, providing an additive benefit to crop productivity. Full article