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Wear rate of WC/Co-based cermet materials under severe tribological conditions is a critical thermomechanical property that can limit the practical application of various tools and industrial machinery. In this paper, three machine learning (ML) algorithms including Random Forest, Gradient Boosting Regressor, and XGBoost are employed to predict the wear rate of WC/Co-based cermets elaborated through powder metallurgy, utilizing dry friction under severe pin-on-disk conditions at elevated temperatures. The study analyzes 116 experimental tribological data points to assess the impact of sliding speed, additive content, hardness, friction coefficient, density, and temperature on estimating the wear of various cermet samples, all tested under a constant normal load of 20 N. The performance assessment shows that ML-based models could effectively predict the wear rate, with the Random Forest algorithm outperforming the others, achieving a coefficient of determination (R2) of 0.8438. Additionally, a comparative analysis is conducted to assess the performance of the ML-based models relative to one another. The models successfully predicted the wear rate of WC/Co-based cermets across various grades, tribological parameters, and physical and mechanical properties, achieving satisfactory accuracy. [ABSTRACT FROM AUTHOR]

Mo2NiB2-Ni cermets, a type of boride-based cermet, exhibit attractive mechanical properties such as high hardness and good wear resistance. However, the mechanical properties of these cermets have predominantly been evaluated at room temperature. In this study, three-point bending tests were conducted at high temperatures to investigate the mechanical properties and fractography of Mo2NiB2-Ni cermets. A ternary Mo2NiB2-Ni cermet was prepared using a calcination process to synthesize Mo2NiB2 before sintering. The calcination process resulted in finer and more uniform Mo2NiB2 particles, enhancing the microstructure. Consequently, hardness and transverse rupture strength (TRS) were improved. Three-point bending strengths were measured for samples measuring 4.0 × 3.0 × 24 mm at temperatures up to 800°C in an argon environment, using silicon carbide jigs with a 16 mm span. The results indicated that TRS remained approximately constant at about 1.6 GPa up to 500°C but decreased sharply above 600°C, reaching about 0.12 GPa at 800°C. This decrease was attributed to the softening of the nickel binder phase, which adversely affected the TRS. [ABSTRACT FROM AUTHOR]

Ti(C, N)‐based cermets have been considered to be the most potential candidates for WC‐Co cemented carbides as tool material due to their various advantages. However, the trade‐off between hardness/strength and toughness limits their further application. Herein, we present new (Ti, W, Mo, Cr)(C, N)‐based cermets showing superior mechanical properties with hardness of 1525 MPa, transverse rupture strength of 2428 MPa, and fracture toughness of 11.44 MPa·m1/2 by compositional and interfacial modification. The strengthening and toughening mechanisms were revealed by experimental observation and theory calculation. It could be clarified that the high elastic modulus caused by a polar covalent bond in the hard phase and solid solution strengthening of the binder phase attributed to the hardness. The strong interface bonding between the core/rim, inner/outer rim, and rim/binder phases stemming from the composition optimization contributed to super crack resistance. Intergranular fracture in submicron‐scaled hard phases led to the crack deflection, transgranular fracture in the micron‐scaled hard phases consumed more energy due to their high intrinsic hardness and excellent interface coordination. The synergy of multi‐scaled hard particles brought about excellent comprehensive mechanical properties. [ABSTRACT FROM AUTHOR]

The combustion modes of powder and granular mixtures (100 – X)(Ti + C) + XNiCr (X = 0–30%) containing Ti powders of different dispersion with different amounts of impurity gases in them are studied. The experimental setup provided the filtration of impurity gases released during combustion in the cocurrent direction or through the side surface of the sample. The difference between the experimental burning velocities of powder mixtures with titanium of a different fineness is explained using a convective-conductive combustion model. For granular mixtures based on Ti powder with a characteristic size of 120 μm, it is shown that combustion occurs in the conductive mode. Comparison of the combustion velocities of granular mixtures containing Ti powder with particles of a characteristic size of 60 μm in the absence and presence of gas filtration through the sample indicates the transition of combustion to the convective regime. The necessary and sufficient conditions for the transition from conductive to convective combustion are formulated, which makes it possible to determine the composition of the mixture whose combustion occurs in the boundary region. In mixtures based on Ti with a particle size of 60 μm, the conductive combustion regime is observed during the combustion of granules 0.6 mm in size and a mixture with X = 30% of granules 1.7 mm in size. For mixtures with X = 0–20% with granules 1.7 mm in size, burning in the convective regime, the interfacial heat transfer coefficients are evaluated using the experimental data. Their values are more than an order of magnitude higher than the theoretical ones. The XRD results of the combustion products showed that in order to obtain synthesis products without side phases of intermetallic compounds, it is necessary to use finely dispersed titanium powder. [ABSTRACT FROM AUTHOR]

Due to elevated potential associated with the extremely vast compositional space of high-entropy alloys (HEAs), there is a significant drive to explore these alloys in high-performance contexts such as intensive wear and oxidative environments. In this regard, this review article comprehensively explores the utilization of HEAs in cemented carbides, focusing on their role as binders in cermets. The wear resistance and oxidation behavior of HEA-containing cermets depends on the ceramic-binder thermodynamic compatibility, phase transformations during sintering, microstructure, and mechanical properties. Hence, much high quality research has been focused into exploring the combination of several HEAs with tungsten carbide, titanium carbides, nitrides, carbonitrides and diborides along with other ceramic compounds. As there are many HEA-ceramic combinations, this review aims to provide a landscape of the developments in this field, providing detailed information about the chemical compositions, sintering techniques, mechanical properties and wear and oxidation resistance obtained. Finally, the need for further research to fully understand the complex interactions between composition, microstructure, and wear and oxidation resistance is highlighted, aiming to tailor HEA compositions for optimized performance. The findings presented in this review contribute valuable insights into the promising applications of HEAs in cemented carbides.

Foundry production is a versatile industry that allows the production of products of almost any configuration and geometric dimensions. These products can be made from materials based on various metals and alloys, bimetallics, and composite materials. The obtained products can have uniform or gradient properties. However, to obtain a product with significantly different properties on the surface and in the volume from the casting, it is expedient to apply coatings with desired properties on the castings that complement the properties, allowing the improvement of coating performance. The paper focuses on the production of cast composite materials with improved surface properties. Various types of coatings based on high‑entropy alloys, cermets, polymers, carbon nanotubes, capable of enhancing the properties of cast composite materials, are considered. The classification and peculiarities of applying these coatings on the surface of composite materials are presented. The prospects of using these coatings to improve the properties of cast composite materials are shown.

The cold spray (CS) process is an advanced material deposition method that has emerged as a versatile method to create high-performance coatings and functional components. This process offers unique advantages in achieving exceptional material adhesion and properties without needing high-temperature melting or heating. The CS process enables the deposition of cermets, allowing it to combine the favorable properties of their constituent phases. This review article explores the bonding mechanism specific to the CS deposition of cermets, highlighting its contrast with that of pure metals. It subsequently investigates the pivotal role played by ceramic particles in the overall efficiency of the CS deposition process, emphasizing the need for a comprehensive understanding of particle properties to achieve quality coatings for specific applications. The paper explores the challenges and limitations imposed by the CS process of cermets in optimizing the crucial parameters. It dissects the influence of interfacial bond strength and porosities on the tribological and corrosion properties of CS-deposited coatings. The discussion extends to the significant role played by substrate in shaping the coating's characteristics. The potential for enhancing coating properties through post-processing treatments is also thoroughly examined. The review article also discusses current advancements in the field and contemplates potential future directions, offering a comprehensive exploration of CS deposition of cermets and its multifaceted considerations. [ABSTRACT FROM AUTHOR]

The thermal plasma spraying technique was employed to coat pre-prepared surfaces of turbine blades. The base material utilized in this process was chromium oxide (Cr2O3), with a consistent 5% alumina content (Al2O3). The base material was strengthened by incorporating a nickel (Ni) alloy with varying percentages (10, 20, 30, 40, 50%). The ceramic powders underwent an hour-long mixing process prior to the preparation of the coating bases. The bases used in this study were made of steel type 316L and their surface was roughened through sandblasting in order to improve the adhesion strength between the coated materials and the base. The bonding material, referred to as (Ni-22%Cr-10%Al-1%Y), was applied by means of spraying with a thickness of 150µm. Following this, both the base material and the reinforced material were also sprayed, resulting in a thickness range of 350-400 µm. This process yielded prepared samples with a final thickness ranging from 550-500 µm. The samples underwent a sintering process at a temperature of 900°C for a duration of two hours. Subsequently, a hardness test was performed on the samples. The results showed that the samples sintered with a 50% reinforcement ratio exhibited the highest hardness of 630Hv. Additionally, the lowest value for porosity was found to be 4.5% at the highest percentage. The adhesion strength after sintering at 50% was measured to be 33 MPa. However, thermal analyses revealed that the thermal expansion coefficient values differed between samples with cermet coating without steel bases (11-16x10-6K-1) and those containing steel bases (7-12x10-6K-1). The Scanning Electron Microscope (SEM) analysis revealed the presence of weaknesses and pores in the coating layers when a low percentage of reinforcement was used. However, as the percentage of reinforcement increased, the mechanical and physical properties significantly improved, reaching their optimum values at 50%. [ABSTRACT FROM AUTHOR]

Experimental studies of the combustion of granular mixtures (100 – X)(Ti + C) + X(Ti + 2B), 0 ≤ X ≤ 100 wt %, were carried out. Granules 0.6 and 1.7 mm in size were made using an alcoholic solution of polyvinyl butyral. The combustion velocity dependence on X showed two characteristic areas with a boundary between them near X = 60 wt %. At X > 60 wt %, the combustion velocity increased significantly which allowed us to assume a convective mechanism of combustion due to the release of impurity gas. This assumption was verified by experiments in which the impurity gases were filtered through the side surface of samples to exclude the effect of a convective heat transfer. The necessary conditions for the transition to the convective combustion mode were formulated. Calculations showed that the critical conditions were met for mixture 40%(Ti + C) + 60%(Ti + 2B) with granule size of 1.7 mm. The content of impurity gas (presumably hydrogen) for mixtures burning in convective mode was estimated. [ABSTRACT FROM AUTHOR]

High-entropy ceramic-based cermets represent a new and promising direction in improving the mechanical properties of conventional hardmetals through the formation of complex microstructures during synthesis. This has been systematically studied in two Co-free, high-entropy (Ti,Zr,Hf,Nb,Ta)C ceramic-based cermets using 10 wt% Ni and 10 wt% FeCrAl metallic binders during hot-press and spark plasma sintering. Fully densified microstructures were achieved in the temperature range of 1400–1500 °C, which is below the melting points of the pure Ni and FeCrAl alloy, owing to the liquid-phase assisted sintering. The optimal densification routes resulted in Vickers hardness (HV30) of 16.77 ± 0.72 and 18.32 ± 0.99 GPa, and fracture toughness (KIc_SENB) of 5.31 ± 0.41 and 4.83 ± 0.50 MPa m0.5, respectively for the Ni and FeCrAl bonded cermets. The improved damage tolerance of these cermets compared to the base (Ti,Zr,Hf,Nb,Ta)C high-entropy carbide is related to the reduced grain size and microstructural toughening mechanisms (e.g. crack deflection and bridging).

The combustion modes of granular mixtures (100 – X)(Ti + C) + XNiCr, X = 0–30%, were studied. The experimental setup provided filtration of impurity gases released during combustion, either in the direction of propagation of the combustion front, or through the side surface of the sample. The comparison of burning velocities in different gas filtration schemes indicates the influence of convective heat transfer on the combustion patterns of mixtures with X < 30%. A method was proposed for determining the composition of the mixture in which the transition to the convective combustion mode occurs. The content of impurity gases in mixtures of different compositions was estimated quantitively. The comparison of experimental data with calculations based on the theory of filtration combustion showed that there is a conductive combustion mode for all mixtures of 0.6-mm granules and a mixture of 1.7-mm granules with X = 30%. XRD analysis of the synthesis products revealed no intermetallic phases, regardless of the size of the granules. [ABSTRACT FROM AUTHOR]

The combustion patterns of powder mixtures (100 – X)(Ti + C) + XNiCr, X = 0–20%, and phase composition of synthesis products were studied. The different nature of the dependence of the burning velocity on the nichrome content for blends containing titanium powders with particles of characteristic sizes of 60 and 120 μm was explained within the framework of the convective–conductive model by the retarding influence of impurity gases released ahead of the combustion front. The conditions for warming up Ti particles before the front were not met for mixtures of fine and coarse titanium powders. XRD spectra of combustion products showed the necessity of using fine titanium powder to obtain cermets without side phases of intermetallic compounds. [ABSTRACT FROM AUTHOR]

TiC-based composites with various initial compositions can be successfully synthesized by self-propagating high-temperature synthesis (SHS) from either mixtures containing thermite reactions or from pure elements. The effect of various experimental parameters on the combustion reaction kinetics and the relationship between structure, microstructure and mechanical behavior of products was identified. It was found that the matrix's strengthening is one of the most important variables in boosting the composite's strength, and adding alloy elements reduces the rate and size of cracks and pores in the cermet microstructure. The presence of TiC particles inhibits dislocation motion and has a significant effect on the composite's mechanical behavior. [ABSTRACT FROM AUTHOR]

Due to the classification of Co as a CMR (carcinogenic, mutagenic, toxic to reproduction) as well as the classification of both Co and WC as CRM (critical raw materials) more and more research is being carried out to investigate possible substitutes for WC-Co hardmetals. To directly compare their microstructure as well as mechanical and thermophysical properties, five very different hardmetals were investigated. For this purpose, the compositions WC-Co, WC-FeNiMn, WC-HEA, NbC-Co and HEC-Co were selected in order to investigate alternative binders for cobalt as well as different alternative hard phases for WC. The results of the hardness measurements showed that for the hardmetals with alternative binders (WC-FeNiMn and WC-HEA) hardness values of 1327 HV10 and 1299 HV10 comparable to WC-Co with 1323 HV10 can be achieved. When WC is replaced by HEC as the hard phase, a significantly higher hardness of 1543 HV10 can be obtained, demonstrating the great potential of high-entropy carbides. Furthermore, the hot hardness measurements between RT and 900 °C showed significantly higher values (up to approx. 290 HV10) for the WC-HEA and HEC-Co hardmetals compared to those of WC-Co. However, the fracture toughness of the alternative hardmetals was lower compared to that of conventional WC-Co hardmetals. In terms of thermophysical properties, the results of the hardmetals with alternative binders were close to those of WC-Co. Thus, it can be shown that it is possible to produce alternative hardmetals with comparable properties to WC-Co and that with further optimization they show great potential to replace WC-Co in the near future. [ABSTRACT FROM AUTHOR]

We investigated the wear and corrosion properties of high-velocity oxygen fuel (HVOF)-sprayed microstructured and near-nanostructured WC-17 wt. % Co coatings fabricated on steel substrates. The near-nanostructured variant exhibited a high hardness value of ~991 Hv, a low corrosion rate of ~0.10624 MPY, a low wear rate of ~0.0012 mm3/m, and a low cumulative wear volume loss of ~0.1304 mm3. Corrosion effects resulted in a reduction of hardness by 23.02% and 30.07% for the near-nanostructured and microstructured samples, respectively; moreover, the wear volume loss of the microstructured coating was 30.02% higher compared to the near-nanostructured coating. We attribute the enhanced corrosion and wear resistance of the near-nanostructured HVOF coating to its dense and uniform surface morphology, low porosity, minimal decarburization, and high hardness. Triboscopic imaging studies further confirmed a low degradation rate, high wear resistance, and minimal wear volume loss. [ABSTRACT FROM AUTHOR]

We study the mechanism of formation of the multilayer structure of the subsurface regions of WC/Mn13 steel cermets after sliding on a steel disk at speeds from 10 to 37 m/s and contact pressure of 5 MPa in order to elucidate the fundamental role of the processes of tribooxidation on a worn surface in the formation of the tribomechanical properties of a large family of similar W/Fe-containing materials. It was shown that the maximum antifriction effect of WC/Mn13 steel cermets under conditions of high-speed sliding was due to in-situ generated FeWO4 that provided friction coefficient drop from ~0.17 to ~0.07 when sliding at 10 and 37 m/s, respectively. The sliding speed had its effect on the subsurface structure and tribolayer thickness, so micron-sized, mechanically mixed 3–4 μm-thick layers (MML) were generated in sliding at 10 and 20 m/s, whose wear occurred mainly by subsurface fracture and delamination of tile-shaped wear particles. Continuous tribolayers with 10–15 μm thickness were generated at 30–37 m/s with underlying zones containing fragmented and deformed WC grains. Such a structure provided plasticizing effect during sliding so that wear was mainly by flow of so plasticized subsurface layers. [ABSTRACT FROM AUTHOR]

Ceramic-metallics (cermets) have emerged as an important class of composite material combining favorable properties of their constitutive phases. In this work, nanostructured cermet Ni(Zn)–Al 2 O 3 composition was synthesized using the high-energy mechanical alloying (HE-MA) method to be deployed as a cold spray deposition powder feedstock. Pre-milled Ni(Zn) alloy particles were mechanically mixed followed by milling in a SPEX™ 8000 M High Energy Ball Mill at a fixed 1050 rpm. The material design-of-experiment (DoE) involved two design compositions (30 wt% and 50 wt% α-alumina) with two substitutional alloy compositions, Ni(5 wt%Zn) and Ni(10 wt%Zn), along with milling time as a process variable. Microstructural characterization confirmed the embedment of nanoscale Al 2 O 3 grain in micron-scale Ni(Zn) alloy particles. Additionally, EBSD analysis of Ni(Zn) alloy particles revealed that Ni(5 wt%Zn) experienced more uniform plastic deformation, work hardening and subsequent fracturing when compared to Ni(10 wt% Zn) alloy particles. The particle size measurement was carried out by laser diffraction showed that the cermet particles milled for 4 h had the desired size range for the objective of cold spraying. Also, the embedment of alumina into the Ni(Zn) alloy matrix and thereby, homogenization of cermet particles enhanced with the increase in milling time. [ABSTRACT FROM AUTHOR]

Cermets are composites of a TiCN hard phase and a metal binder, typically a mixture of Co and Ni. They offer excellent combinations of hardness and fracture toughness as well as bending strength. Due to the current classification of both Co and Ni as CRM as well as CMR there is interest that their use shall be limited and their amount within cermets reduced. Within this study, a novel high entropy alloy-based metal binder system, comprising only elements that are not strong oxide or carbide formers is investigated with regard to their mechanical and microstructural properties they offer in TiCN-based cermets. Within the investigated equimolar MnFeCoNiCu composition, small Cu precipitations are found after sintering. Due to this, the Cu content was systematically reduced, and the maximal solubility estimated at which still a full solid solution occurs. With an optimized Cu content, dense cermets with a single FCC binder phase and with hardness values of up to 1213 HV30 and fracture toughness values of 14.8 MPa·m1/2 could be achieved. [ABSTRACT FROM AUTHOR]

Alumina/molybdenum nanocomposites were prepared by colloidal synthesis from alumina powder and molybdenum (V) chloride using ethanol as dispersion medium. Modified alumina was calcined at 450 °C in air atmosphere to remove chlorides, and then treated in a tubular furnace at 850 °C under Ar/H 2 to reduce the MoO 3 formed in the previous stage and obtain Al 2 O 3 with molybdenum nanoparticles on the surface. Three different molybdenum contents were proposed (1, 5 and 10 wt % Mo), and pure alumina was used as reference, that were sintered by spark plasma sintering (SPS) under vacuum atmosphere at 1400 °C for 3 min with an applied pressure of 80 MPa. Composites were characterized by microstructure, hardness, toughness, and three-point bending test. The presence of molybdenum nanoparticles resulted in a fine-grained structure promoted by the presence of molybdenum at grain boundaries and triple points, as well as by the utilization of the SPS equipment. Hardness is at least a 20% greater and fracture toughness 30% larger in the composites than in the monolithic alumina. [ABSTRACT FROM AUTHOR]

The thermal properties of MoW‐HfN, a surrogate cermet for MoW‐UN nuclear thermal propulsion fuel, were characterized over a wide range of elevated temperatures. Thermal diffusivity, coefficient of thermal expansion (CTE), and heat capacity were measured. Optical and scanning electron microscopy were performed to characterize the microstructure and draw structure–property correlations. The thermal diffusivity was obtained using the laser flash method. Diffusivity values ranged from about 0.18 cm2/s at 200°C to 0.15 cm2/s at 1800°C. The CTE was measured using push‐rod dilatometry up to 1600°C, giving values between 6.0 and 9.0 μm/m. A scientific rationalization of the effective material properties is made using the rule‐of‐mixtures and other effective properties models. [ABSTRACT FROM AUTHOR]

Cermet materials exhibit advanced mechanical and tribological properties, and are widely used for tribology, elevated temperature, and machining applications due to their unique amalgamation of hardness, strength, and toughness. This paper presents a comprehensive overview of various cermet systems and recent advances in high-temperature tribology and cutting performance of cermet and ceramic tool materials. It outlines microstructural properties, such as lessening grain sizes, obtaining extended grains, lowering grain boundary phase content, amorphous grain boundary phases crystallizing, inter-granular phase strengthening, and managing crack propagation path. Additionally, surface processing or surface modifications, such as surface texturing, appropriate roughness, or coating technique, can optimize the ceramic and cermet tribological performances. The purpose of this study is to present some guidelines for the design of ceramics and cermets with reduced friction and wear and increased cutting performance. The current research progress concerning tribological properties and surface texturing of cutting tool inserts is critically identified. Lubrication techniques are required in commercial applications to increase the lifetime of cutting tools used in harsh conditions. Liquid lubricants are still commonly utilized in relative motion; however, they have the limitations of not working in extreme settings, such as high-temperature environments. As a result, global research is presently underway to produce new solid lubricants for use in a variety of such conditions. This review also provides a quick outline of current research on this topic. [ABSTRACT FROM AUTHOR]

Bu çalışma kapsamında, Elektrik Akımı Destekli Sinterleme (ECAS) yöntemi kullanılarak 600-4500A akım aralığında yaklaşık 6 dakika gibi bir sürede WC-Co ve ağırlıkça %5, %7,5 ve %10 oranlarında TiC katkılı WC-Co malzemelerinin üretimleri gerçekleştirilmiş ve katkı miktarına bağlı olarak TiC’ ün özellikler üzerine etkisi incelenmiştir. SEM incelemelerinden katkısız WC-Co numunesinin uniform bir yapıya sahip olduğu, ilave edilen TiC partiküllerinin matris ile uyumlu bir birleşme gösterip, yapı içerisinde üniform dağıldığı görülmüştür. XRD paternlerinden katkısız numunede WC, Co pikleri ve TiC ilave edilen numunelerde ise WC, Co piklerinin yanı sıra TiC piki de tespit edilmiştir. Katkısız WC-Co ve ağ. %5, %7.5, % 10 TiC katkılı numunelerin nispi yoğunlukları sırasıyla %98.77, %96.42, %95.91 ve %95.33 olarak hesaplanırken, mikrosertlik değerleri 1299 HV0.5, 1402 HV0.5, 1581 HV0.5 ve 1768 HV0.5 olarak belirlenmiştir. Elektrokimyasal korozyon çalışmaları Ağ.%3.5 NaCl çözeltisi içerisinde gerçekleştirilmiş olup numunelerinin korozyon hızları sırasıyla 96.25 mpy, 89.13 mpy, 87.64 mpy ve 72.41 mpy olarak tespit edilmiştir. Yapılan çalışmalar sonucunda TiC miktarının artmasıyla nispi yoğunluklarda azalma gözlenirken sertlik değerlerinin arttığı ve korozyon özelliklerinin iyileştiği belirlenmiştir.

The class of NbC-Ni cermets has emerged as a promising environmentally friendly alternative to WC-Co cemented carbide tools, although some inherent properties i.e. room temperature hardness and flexural strength, of NbC-Ni cermets may require further enhancements. To enhance the properties of NbC-Ni cermets, diverse methodologies were applied, including grain inhibition and the strengthening of the cermet through the use of reinforcements. This study systematically examined the impact of TiC additions, specifically at 10% and 20%, on both the microstructure and mechanical properties of NbC-12Ni-4VC-4Mo _2 C cermets. NbC-12Ni cermets were fabricated via vacuum liquid phase sintering (LPS) at 1400 °C and 1450 °C. Enhancements by incorporating 4% VC and 4% Mo _2 C, followed by TiC at 10% and 20% concentrations to the NbC-Ni-4VC4Mo _2 C cermet were made. XRD and SEM results confirm the formation of (Nb, X, Y) C solid solution cubic FCC carbides. Significant grain refinement was evident in the cermet samples, subjected to grain inhibition. The observed grain sizes ranged from a maximum of 6.84 μm (in NbC12Ni) to a minimum of 2.154 μm (in the sample containing 20% TiC) at 1450 °C. The incorporation of 20TiC at 1450 °C led to a remarkable 26.5% enhancement in average hardness compared to NbC-Ni cermet, and a 4.2% improvement over the 4VC4Mo _2 C cermet. At 1450 °C, 20TiC reinforcement led to an average fracture toughness of 9.331 MPa√m, representing a 4.56% improvement over the 4VC4Mo _2 C cermet. However, there was a marginal reduction in toughness compared to the NbC-Ni cermet. Moreover, the addition of TiC led to a decrease in the flexural strength of the cermets, with a maximum flexural strength of 939 N mm ^−2 recorded for NbC-Ni-4VC4Mo _2 C, representing an 11.6% increase compared to the NbC-Ni cermet.

Abstract This study presents the development of niobium carbide cermets bound to nickel and Ni-12Al (wt%). The use of Ni-12Al (wt%) and Ni aims to replace strategic elements such as cobalt (Co) utilized in tungsten carbide-based cermets. Cermets of different compositions were processed by conventional powder metallurgy. Microstructural analysis with semi-quantitative chemical analysis by EDX, Vickers microhardness and density measurement were performed to evaluate the influence of high energy milling application and sintering temperature on the properties of these cermets. A milling time of 20 min in a planetary mill and sintering temperatures of 1420 ºC or 1450 ºC resulted in homogeneous microstructures, densities close to 90% and hardness of around 1000 HV1, showing a potential for use of this material in cutting tools.

In this study, brazing joints between cermets and 45 steel were obtained by vacuum brazing, using the self-prepared Cu-Zn-Ni-Mn-Si-Mo filler metal with appropriate melting point and good wettability on cermets. The influences of brazing temperature and holding time on the shear strength of Mo2FeB2-based cermets and Ti(C,N)-based cermets/filler metal/45 steel joints were evaluated. Results revealed that as the brazing temperature increased or the holding time prolonged, the shear strength of both joints first increased and then decreased. The maximum shear strength of 270.4 MPa was achieved for the joint between Ti(C,N)-based cermets and 45 steel brazed at 1080 °C for 15 min, while the maximum shear strength of 275.7 MPa was recorded between Mo2FeB2-based cermets and 45 steel brazed at 1040 °C for 15 min. Moreover, the interface structure of brazing joints was observed and characterized under optimal technological parameters by SEM and EDS. The diffusion layer with a certain thickness was formed at the interface, and thus the joints were composed of five areas: 45 steel, transition layer, metal filler, transition layer, and cermets. Elements diffused from the filler metal to the base metal on both sides, resulting in the improvement of the shear strength of the joints. [ABSTRACT FROM AUTHOR]

High-entropy carbides (HEC) are a class of promising new hard phases for a sustainable improvement of hardmetal properties. In this work, hardmetals of the HEC (Ta,Nb,Ti,V,W)C were studied with two typical binder volume fractions of 16 and 24 vol-% consisting of Co, Ni and FeNi. The sintering behaviour, microstructure, phase composition, magnetic and mechanical properties are discussed and are compared to a conventional WC-Co hardmetal. It was shown that the HEC has a high-phase stability and that dense hardmetals with promising mechanical properties were obtained. [ABSTRACT FROM AUTHOR]

In situ composite manufacture is an approach to improve interfacial adhesion between matrix and reinforcements, in which reinforcements are synthesized along composite processing itself. In situ powder metallurgy route, in particular, offers alternatives to some shortcomings found in other techniques. This work aims not only to review the state of the art on metal matrix composites (MMCs)—including cermets—obtained in situ by powder metallurgy, but also to dissect key aspects related to the development of such materials in order to establish theoretical criteria for decision making before and along experiments. Aspects regarding the design, raw material selection, and processing of such composites were observed and divided between concept, intrinsic, and extrinsic parameters. That way, by means of material databases and computational thermodynamics applied to examples of the reviewed literature, we aim at providing tools in both conducting leaner experiments and richer discussion in this field. [ABSTRACT FROM AUTHOR]

Due to the classification of Co as a CMR (carcinogenic, mutagenic, toxic to reproduction) as well as the classification of both Co and WC as CRM (critical raw materials) more and more research is being carried out to investigate possible substitutes for WC-Co hardmetals. To directly compare their microstructure as well as mechanical and thermophysical properties, five very different hardmetals were investigated. For this purpose, the compositions WC-Co, WC-FeNiMn, WC-HEA, NbC-Co and HEC-Co were selected in order to investigate alternative binders for cobalt as well as different alternative hard phases for WC. The results of the hardness measurements showed that for the hardmetals with alternative binders (WC-FeNiMn and WC-HEA) hardness values of 1327 HV10 and 1299 HV10 comparable to WC-Co with 1323 HV10 can be achieved. When WC is replaced by HEC as the hard phase, a significantly higher hardness of 1543 HV10 can be obtained, demonstrating the great potential of high-entropy carbides. Furthermore, the hot hardness measurements between RT and 900 °C showed significantly higher values (up to approx. 290 HV10) for the WC-HEA and HEC-Co hardmetals compared to those of WC-Co. However, the fracture toughness of the alternative hardmetals was lower compared to that of conventional WC-Co hardmetals. In terms of thermophysical properties, the results of the hardmetals with alternative binders were close to those of WC-Co. Thus, it can be shown that it is possible to produce alternative hardmetals with comparable properties to WC-Co and that with further optimization they show great potential to replace WC-Co in the near future.

We study the mechanism of formation of the multilayer structure of the subsurface regions of WC/Mn13 steel cermets after sliding on a steel disk at speeds from 10 to 37 m/s and contact pressure of 5 MPa in order to elucidate the fundamental role of the processes of tribooxidation on a worn surface in the formation of the tribomechanical properties of a large family of similar W/Fe-containing materials. It was shown that the maximum antifriction effect of WC/Mn13 steel cermets under conditions of high-speed sliding was due to in-situ generated FeWO4 that provided friction coefficient drop from ~0.17 to ~0.07 when sliding at 10 and 37 m/s, respectively. The sliding speed had its effect on the subsurface structure and tribolayer thickness, so micron-sized, mechanically mixed 3–4 μm-thick layers (MML) were generated in sliding at 10 and 20 m/s, whose wear occurred mainly by subsurface fracture and delamination of tile-shaped wear particles. Continuous tribolayers with 10–15 μm thickness were generated at 30–37 m/s with underlying zones containing fragmented and deformed WC grains. Such a structure provided plasticizing effect during sliding so that wear was mainly by flow of so plasticized subsurface layers.

The paper proposes and numerically investigates the model of combustion synthesis of composite material from the multicomponent powder mixture Ti–Al–C–Fe2O3, and presents a complete schematic of the synthesis process with regard to the dependence of the powder mixture properties on its structure and composition. It is found that the major phases are TiC, Al2O3, FeAl, FeAl3 as well as TiFe intermetallic and Fe. The reaction rate depends on the weight fraction Y of the two stoichiometric mixture components (1–Y)(Ti + C) + Y∙(Fe2O3 + 2Al)), the minimum of which is 0.43±0.2. The results obtained at Y → 0 and Y → 1 confirm the model correctness for thermodynamic system. [ABSTRACT FROM AUTHOR]

Cermets are composites of a TiCN hard phase and a metal binder, typically a mixture of Co and Ni. They offer excellent combinations of hardness and fracture toughness as well as bending strength. Due to the current classification of both Co and Ni as CRM as well as CMR there is interest that their use shall be limited and their amount within cermets reduced. Within this study, a novel high entropy alloy-based metal binder system, comprising only elements that are not strong oxide or carbide formers is investigated with regard to their mechanical and microstructural properties they offer in TiCN-based cermets. Within the investigated equimolar MnFeCoNiCu composition, small Cu precipitations are found after sintering. Due to this, the Cu content was systematically reduced, and the maximal solubility estimated at which still a full solid solution occurs. With an optimized Cu content, dense cermets with a single FCC binder phase and with hardness values of up to 1213 HV30 and fracture toughness values of 14.8 MPa·m1/2 could be achieved.

For the fabrication of brittle materials like cermets through Selective Laser Melting (SLM), the pulse shaping technique has proven to be an effective and optimal way to produce cermet with no cracks. The purpose of this work is to investigate the effect of laser peak in pulse shaping as a preheating and cooling approach for the melt pool of TiC − Fe based cermet using the pulse shaping technique. Several samples were fabricated with variations in laser power and exposure time refereed as pre-pulse and post-pulse before and after the laser peak power (LPP). Microstructural and phase analyses were performed on the fabricated SLM sample using SEM and XRD to study the effect of pulse shaping with variation in exposure time and therefore energy density. Mechanical properties like microhardness were calculated and hence the effect of hardness and energy density were studied. Results indicated that preheating and cooling through laser pulse during pulse shaping has a beneficial effect on the fabrication of the crack-free brittle cermet. [ABSTRACT FROM AUTHOR]

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Several innovative mixed powders of Ti6Al4V and NiCr-Cr3C2 with different CeO2 contents (0, 1, 2, 3, and 4 wt.%) were designed, and Ti2C-reinforced CrTi4-based composite coatings were prepared on the Ti6Al4V surface via laser cladding technology. The effects of CeO2 amount on the forming quality, microstructure, hardness, and wear resistance of the composite coatings were studied. The results showed that the CeO2 amount had a significant influence on the forming quality of the composite coatings. The cracks were eliminated completely when the CeO2 content was 2 wt.%; furthermore, the lowest porosity was obtained with the addition of 3 wt.% CeO2. The primary phase constituents of the coatings were non-stoichiometric Ti2C and a β-type solid solution (CrTi4) as the reinforcement and matrix, respectively. CeO2 and a low quantity of Ce2O3 were re-precipitated at the Ti2C/CrTi4 interface and CrTi4 grain boundary in the coatings with CeO2 addition. In addition, the average hardness of the composite coatings was 1.28–1.34 times higher than that of the Ti6Al4V substrate. The wear resistance of the composite coatings was significantly higher than that of the substrate. However, both the composite coatings and the Ti6Al4V substrate exhibited a mixed-wear mode, i.e., abrasive and adhesive wear. [ABSTRACT FROM AUTHOR]

To overcome the difficulty in the uniform phase distribution, wetting interface, and sintering densification of the cermets, the reinforced phases were uniformly wrapped and distributed on the surface of the base materials by ball-milling technology to improve the comprehensive performance of the cermets. The ball milling parameters and sintering properties of the coated SiO2/Al composite powders were investigated in this paper. The results show that, the specific surface area of the SiO2/Al composite powders increases first and then decreases with the extension of the milling time, and the specific surface area of the SiO2/Al composite powders shows the largest and reaches 8.1 m2·g−1 by ball milling for 6 h. The specific surface area of the SiO2/Al composite powders increases first and then decreases with the increase of the ball-to-material ratio, indicating that the SiO2 content coated on the surface of Al powders increases first and then decreases. With the increase of milling speed, the specific surface area of the SiO2/Al composite powders increases first and then decreases. With the increase of sintering temperature, the surface hardness of the SiO2/Al cermets increases first and then decreases. When the sintering temperature is 900 ℃, the surface hardness of the SiO2/Al cermets reaches the highest. The better properties of the SiO2/Al cermets are obtained when the ball milling time is 6 h, the ball-to-materials ratio is 2:1, the ball milling speed is 360 r·min−1, and the sintering temperature is 900 ℃.

Incorporation of additional carbides into the widely-used Ti(C, N)-based cermets constitutes an important aspect of materials optimization strategy to impart better service properties for mining and machining applications. In this work, Ti(C, N)-WC-Mo 2 C–TaC-(Ni, Co) cermets with the WC content varying from 5.77 wt% to 19.68 wt% were specifically designed based on thermodynamic calculations, and their mechanical and tribological properties were subsequently examined. The results show that the increase of WC content brought about a higher fraction of the white core phase, which also induced a rise in hardness (by ∼10%) but a decline in toughness (by ∼20%). In addition, decreased wear rates (by ∼80%) at both 25 °C and elevated temperatures (400 and 750 °C) were also noted on the cermets containing the highest WC concentration. The wear behavior was found to be controlled by the surface hardness at 25 °C whereas the extent of oxide tribolayer formation at high temperatures. Micro-Raman spectroscopic and transmission electron microscopic observations suggested that the favorable generation of oxide tribolayers consisting of TiO 2 and WO 3 nano-crystals contributed to the improved high-temperature tribological properties. [ABSTRACT FROM AUTHOR]

The diffusion behavior of the secondary carbides Mo2C and WC in TiC-based and Ti(C,N)-based cermets was investigated by means of diffusion couples (MeC-Ni/TiC-Ni and MeC-Ni/Ti(C,N)-Ni, Me = Mo or W) annealed from 1150 to 1350 ºC. The diffusion coefficients were calculated based on the measured concentration profiles. The results indicate that the diffusion rate of W in Ni binder is slower than that of Mo, and N would retard the diffusion of Mo. Typical core-rim structure can be observed at 1350 ºC. The calculated vertical sections of MeC-Ni/TiC-Ni and MeC-Ni/Ti(C,N)-Ni (Me = Mo or W) are used to describe the formation of carbides near the interface. The precipitation of secondary carbides affects the formation of the rim, and this effect will become larger as the sintering temperature increases, especially when Ni is completely melted. Thus, the concentrations of Mo and W should be carefully controlled to avoid the formation of carbides for the sake of obtaining a complete core-rim structure. In addition, in the region with higher W concentration, the rim thickness is larger with a smaller average grain size. However, when the rim thickness increases to 1.2 μm, the average grain size increases compared to the region where it is 0.8 μm. [ABSTRACT FROM AUTHOR]