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WC-Ni hardmetals, especially with the addition of Cr, are the first choice for wear parts in a corrosive environment. Despite Ni being studied as a metallic binder matrix in hardmetals for as long as Co, the mechanical properties achieved have consistently fallen behind those of their cobalt-containing counterparts. Due to the rapidly increasing demand for Co, its substitution is of increasing importance. In this study, various alloying elements that do not form strong carbides were systematically investigated as part of a binary Ni-based binder system for hardmetals. Solid and liquid phase sintering were compared by using field assisted sintering and a conventional SinterHIP furnace. The obtained hardmetals were analysed in terms of their microstructure, phases, sintering behaviour, and mechanical properties. The metals manganese, iron, and copper, as well as the metalloids silicon and germanium, were evaluated as additional binder constituents. Hardmetals with a binary Ni-based binder alloy were successfully prepared. The combination with Mn or Si showed the potential to significantly lower the necessary sintering temperature. In particular, Mn proved to be the most effective grain growth inhibitor among the investigated alloying elements. [ABSTRACT FROM AUTHOR]

In order to investigate the cause of the liquid phase migration (LPM) and the shape distortion when WC-Co cemented carbides (alloys) undergo a temperature gradient during cooling, round bars of WC-10 mass%Co alloys are inserted halfway under the coil of the induction heating furnace and partially heated at 1673 K. The results showed that Co migrated from the higher temperature side to the lower one and increase of Co content and bar diameter occurred in a zone at the outside of the coil. The alloy containing free carbon had a significantly narrow Co-increased zone and the zone located at a lower temperature. The volume transfer (V) of Co during heating changed in proportional to the square root of the heating time (t). It was considered that the phenomenon was the same as the LPM between a couple of alloys having different Co content in our previous report. We have concluded that the Co-increased zone in this study corresponds to the Co solid-liquid coexistence zone during partial heating and the Co increase is caused by the migration pressure occurred in the zone, which we named ΠSL. ΠSL should be generated because FWC/Co(S) derived from γWC/Co(S) and γCo(L)/Co(S) is higher than FWC/Co(L) derived from γWC/Co(L). [ABSTRACT FROM AUTHOR]

Ground round bars made of WC-20 mass%Co cemented carbides were used to accurately determine the changes in shape. The bars were heated at 1673 K and cooled under different conditions to investigate the changes in Co content and diameter (d) in the longitudinal direction. When the bars were heated in a conventional sintering furnace, rapid cooling increased the Co content and d at both ends, while slow cooling increased those at the center. In the latter case, the amount of change was smaller. When the bar was heated using a tubular furnace and then cooled under 30 K of temperature gradient in the longitudinal direction, the Co content and d on the higher temperature side decreased and those on lower temperature side increased. The relationship between the change in Co content and the change in d could be explained quantitatively by considering the migration of the liquid phase in the temperature range of solid-liquid Co coexistence region. This study revealed that when WC-Co cemented carbides were fabricated using the conventional sintering furnace, an inevitable temperature gradient in the specimen during cooing caused the liquid phase migration and the shape distortion, regardless of the cooling rate. [ABSTRACT FROM AUTHOR]

It is currently known that in certain circumstances pre-rounding of cutting blades can significantly increase tool life. Despite many data on the beneficial effect of drag-finishing on the durability of metalworking tools, it is not entirely clear whether similar benefits appear when machining wood-based panels. The results of some pilot study are quite promising but the real impact of cutting blades pre-rounding (it is about blades made of various standard cemented carbides), on tool life in particleboard milling are very rarely studied. The study aims to fill this gap in the knowledge system. The experimental research was carried out using a CNC milling machine equipped with a single-blade milling head with replaceable blades. It turned out that the positive effect of the drag-finishing of cutting blades on tool life in particleboard machining depends on the structure and hardness of carbide. A significant extension of the tool life (about 50%) was observed only in the case of particularly hard carbide (2240 HV10). There was no significant advantage for the softer type of carbide (1800 HV10). [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.

Inhomogeneous structure WC−6Co cemented carbides with the different Y2O3 additions (mass fraction) were prepared by low pressure sintering. The microstructure and properties of the cemented carbides were investigated by scanning electron microscope (SEM), X-ray diffraction analyzer (XRD), energy dispersive spectrometer (EDS), metallographic microscope, electronic universal mechanical test machine, hardness meter, and coercivity magnetometer. The results show that, the relative density and phase composition of the cemented carbides are not affected by Y2O3 addition. Y2O3 forms a stable solid solution with the impurity elements such as sulfur and oxygen, which disperses in the WC grain boundary, hinders the fusion and growth of WC grains, reduces the size of WC grains, and inhibits the homogenization of WC grains in inhomogeneous structure. With the increase of Y2O3 mass fraction, the hardness of the cemented carbides increases gradually, and the bending strength shows a trend of rapid rise and then decline. The optimum properties of the cemented carbides are obtained when the Y2O3 mass fraction is 0.048%, the hardness and bending strength are 1530 kgf·mm−2 and 2902 MPa, respectively.

Cemented carbide alloys are well known powder metallurgically processed materials used for a wide range of tooling and components that require a good balance of hardness and fracture toughness, together with wear resistance. After 100 years of the first patent, research and development within this area continues to fulfil more demanding applications and adapt to new requirements. The last decade especially has witnessed important advances. In that sense, Co-free compositions are being studied due to the health issues that its use implies and its criticality in the supply chain. Secondly, the steps towards near-net-shape components by means of additive manufacturing technologies to avoid waste of powder and the technological advance of fast sintering processes are promising. Finally, new microstructural and mechanical characterization methods at micro and nanoscale provide helpful insights for a better understanding of these materials under performance.

The suppression technology assisted by longitudinal ultrasonic vibration was proposed to solve the problems of poor powder fluidity, uneven particle size distribution, and poor mechanical properties for the coarse-grained WC−10Co cemented carbides. The effects of compression force, height-diameter ratio, ultrasonic time of preloading, and ultrasonic amplitude on the compact density, compact surface quality, and mechanical properties of the alloys were discussed. The results show that, compared with the conventional pressing, the powder particles have the violent collision under the effect of ultrasonic vibration, enhancing the fluidity between particles. The density increases with the pressing force increase from 80 to 100 MPa. The compact density increases significantly, when the height-diameter ratio reduces, the ultrasonic time of preloading increases, and the ultrasonic amplitude increases. At the same time, the surface quality of the compacts is improved, and the elastic aftereffect is decreased by 0.16%. The pores of the alloys are reduced, the grain size is evenly distributed, and the coarse grain is reduced after sintering. With the little change in hardness and density, the fracture toughness increases by 5.83%~16.10%, while the bending strength decreases obviously.

WC-Ni hardmetals, especially with the addition of Cr, are the first choice for wear parts in a corrosive environment. Despite Ni being studied as a metallic binder matrix in hardmetals for as long as Co, the mechanical properties achieved have consistently fallen behind those of their cobalt-containing counterparts. Due to the rapidly increasing demand for Co, its substitution is of increasing importance. In this study, various alloying elements that do not form strong carbides were systematically investigated as part of a binary Ni-based binder system for hardmetals. Solid and liquid phase sintering were compared by using field assisted sintering and a conventional SinterHIP furnace. The obtained hardmetals were analysed in terms of their microstructure, phases, sintering behaviour, and mechanical properties. The metals manganese, iron, and copper, as well as the metalloids silicon and germanium, were evaluated as additional binder constituents. Hardmetals with a binary Ni-based binder alloy were successfully prepared. The combination with Mn or Si showed the potential to significantly lower the necessary sintering temperature. In particular, Mn proved to be the most effective grain growth inhibitor among the investigated alloying elements.

The research aims to develop a novel and safer milling route to produce Hard Metals. Considering the risks associated with milling fine particles under organic solvents, especially the increased fire and explosion risks, we propose milling under aqueous milling media to diminish the risks associated with fire hazards, while maintaining the oxidation level at a minimum. The samples were sintered in an industrial sintering oven under vacuum at 1380°C subsequent to milling and drying. The characterisation of the materials has been done by X-ray diffraction, scanning electron microscopy, particle size analysis, optical microscopy, and a magnetometer. The obtained results indicate that appropriate properties of the powders after milling and drying as well as the desired biphasic (Co-WC) phases were obtained after sintering, thus proving the feasibility of such a route and diminishing specific fire hazards.

Obtaining cemented carbides with smaller WC grain size and better properties is key to their wider application. Ultrafine cemented carbides were prepared by using spark plasma sintering (SPS) with nano VC-Cr3C2 as nanocomposite grain growth inhibitors (NGGIs) and multi-walled carbon nanotubes (MWCNTs) as reinforcing materials. The effects of NGGIs and MWCNTs on the microstructure and mechanical properties of alloys were evaluated. The results indicated that the specimens (0.5 wt % NGGIs and 0.4 wt % MWCNTs) prepared at 1350 °C for 8 min under a pressure of 50 MPa have enhanced mechanical properties (HV 2520.85 kgf/mm2, KIC 13.26 MPa m1/2) and a homogeneous microstructure. The grain size of WC is suppressed (the average grain size is 200–400 nm). NGGIs can prevent the dissolution of W and C in liquid Co, thereby inhibiting the growth of WC grains. The uniform dispersion of MWCNTs in WC matrix mobilizes their fiber-reinforcement effect. The combination of NGGIs, MWCNTs, and SPS can improve the mechanical properties and optimize the microstructure of the alloy.

In this study, radio-frequency plasma spheroidization was used to obtain spherical WC-Co powder from granulated WC-Co powder using different parameters. The results show that the spheroidization ratio of the powder first increased and then decreased with an increase in plasma power, whereas the trend of the average particle size is the opposite. The spheroidization ratio of the powder decreased with an increase in the powder feeding rate, whereas the average particle size increased. This also indicates that cobalt loss and WC decomposition occurred during plasma spheroidization. The loss of cobalt increased continuously with increasing plasma power and decreasing powder feeding rate. Black and white particles with significantly different carbon distributions were observed in the spheroidized powder, which were mainly caused by the different degrees of WC decomposition. The flowability and apparent density of the spheroidized WC-Co powder were positively correlated with the ratio of black to white particles. [ABSTRACT FROM AUTHOR]

This study focuses on preparing two types of cemented carbides: one with Ti elements and the other without, using a stepwise sintering process, primarily evaluating their mechanical properties. The research includes a thorough analysis of microstructure changes and post-wear surface alterations, coupled with assessments of phase composition, element content, relative density, surface hardness, fracture toughness, and wear properties. Results reveal that cemented carbides treated with in-situ surface modification under high-temperature nitrogen atmospheres exhibit exceptional densification. An in-situ hard-phases layer, predominantly TiN or Ti(C, N), is gradually grown on the surface of the WC-Co-Mo-TiNC cemented carbides, enhancing surface hardness and fracture toughness. This technology fortifies the material against indentation, crack expansion, and fracture, significantly improving wear resistance and extending service life. In essence, the in-situ surface modification technology, especially under high-temperature nitrogen atmospheres, emerges as a transformative approach, enhancing mechanical properties and substantially improving wear resistance for prolonged practical applications. [ABSTRACT FROM AUTHOR]

The WC-Co composite material is one of the most difficult materials to manufacture using a one-step additive manufacturing process such as Laser Powder Bed Fusion process (L-PBF). Recently, the addition of hexagonal boron nitride (hBN) has conferred good mechanical properties (hardness and wear) to WC-Co. However, comprehensive studies on the feasibility of adopting L-PBF for the composite are lacking. Thus, this study seeks to use L-PBF to prepare WC-Co-hBN (hBN: 3 vol.%) cemented carbide specimens by varying the processing parameters (laser power, scan speed and scan spacing). The effects of processing parameters on microstructural and mechanical properties on specimens are investigated using microstructural and chemical composition analysis, surface porosity analysis, microhardness and fracture toughness testing. The innovation of the study is that the hBN addition coupled with the varying printing parameters can regulate the resultant microstructure of the material and dictate very different mechanical properties. In detail, the findings of the experiments indicate that scan spacing was a significant factor in obtaining high densification. A highly dense specimen at 98% relative density (12.73 g/cm3) can be achieved at 0.04 mm scan spacing. We also recognized a reduction in the density generally linked to the low sinterability of BN, which resulted in a local volume increase of the specimen. Thus, hBN could be a good candidate for lightweight properties when added to materials, lowering the composite's effective density. The L-PBF procedure resulted in inhomogeneous and fast grain growth of WC, which was linked to the non-uniform temperature distribution and varying cooling rates of melt pools during processing. Processed specimens were largely composed of polyangular WC carbides and WC platelets. The volume fraction of these two structures were influenced solely by the scan speed and laser power. The WC structure type has a significant effect on the strength of the composite. As a result, the study shows possibility of fabricating cemented carbides for functionally graded applications by adjusting the process parameters affecting WC carbides' morphology. [ABSTRACT FROM AUTHOR]

This study investigates the influence of different sinter-HIP temperatures and binder saturation levels on the microstructure and properties of WC–12Co cemented carbide, produced using binder jetting. The sinter-HIP process was performed at 1400 °C, 1460 °C, and 1500 °C and binder saturation levels of 60% and 75% were selected during printing. The binder saturation proved to affect the repeatability of the manufacturing process and the sturdiness of the green models. The increase of the sintering temperature from 1400 °C to 1460 °C is correlated with an increase in the density. Nonetheless, a further raise in temperature to 1500 °C leads to significant grain coarsening without clear advantages in terms of porosity reduction. Both the transverse rupture strength and Vickers hardness increase when the sinter-HIP temperature rises from 1400 °C to 1460 °C, where the typical results for traditionally manufactured WC–12Co are met, with a comparable grain size. The transverse rupture strength and Vickers hardness then decrease for samples treated at 1500 °C. Finally, potential issues in the manufacturing process are identified and correlated with the defects in the final components. [ABSTRACT FROM AUTHOR]

Cemented carbides WC-Co are one of the basic tool materials. They constitute over half of the currently used tools intended for machining. The main advantages of WC-Co cemented carbides are high hardness and abrasion resistance. The properties of WC-Co sinters depend mainly on the content of the binding phase, the sintering method and the grain size of the powder from which the sinters were made. The aim of this study was to produce fine-grained WC-Co composites using SPS (spark plasma sintering) technology, as well as examine the effect of the applied technology on the basic properties of WC-Co sinters: microstructure, hardness, phase composition, compaction degree and tribological properties. In the processes carried out, no additives affecting the reduction in grain growth were used. Sintering was conducted at a temperature of 1200 °C with a holding time of 10 min. The process occurred under a load of 100 MPa. Finally, the samples were cooled in a vacuum of 10−6 mbar. We measured the hardness using a Vickers hardness tester. We took hardness measurements along the diameter of the sintered samples. In order to ascertain the fracture toughness (KIC), we measured the radial crack length around the Vickers indentation and applied Shetty's formula. The tribological tests were carried out with a tribotester using the T-01 ball-on-disc method. The obtained data enabled the characterization of the wear process of the tested materials. [ABSTRACT FROM AUTHOR]

We investigated the effect of barothermal treatment at a pressure of 8 GPa and temperatures of 1450–1700°C on the structure and properties of cemented carbides with varying cobalt concentrations. The application of barothermal treatment led to a 30% increase in the grain size of the carbide phase and a decrease in overall porosity. For WC–6Co alloys treated under conditions of solid-phase sintering, an increase in hardness and the stress intensity factor are observed. The barothermal treatment of WC–15Co alloys at temperatures corresponding to the existence of a liquid phase leads to the formation of Co3W3C intermetallic phases. [ABSTRACT FROM AUTHOR]

Despite extensive research on grinding of cemented carbide, few studies have examined abrasive machining of this material using smalldiameter super abrasive tools (also known as grinding pins/points), especially with respect to varying cooling-lubrication methods. This study therefore focuses on a comparative experimental investigation of three such methods-dry, emulsion, and lubricated liquid carbon dioxide (LCO2-MQL). The performance of these methods and the resulting grindability are examined in terms of grinding forces, force ratios, specific energy, and through the analysis of wheel loading. The results show that LCO2-MQL grinding has lower grinding forces (normal forces-8 % to 145 % lower than dry grinding, and 18 % to 33 % lower than emulsion grinding and tangential forces-4 % to 66 % lower than dry grinding and 28 % to 78 % lower than emulsion grinding) and specific energy 24 % to 51 % lower compared to dry grinding and 64 % to 69 % lower than emulsion grinding, indicating its potential for efficient material removal. However, a challenge with high wheel loading was observed with LCO2-MQL, likely due to the lack of oxygen in the CO2 grinding atmosphere. Despite this issue, the LCO2-MQL method shows potential for efficient operations, especially at higher aggressiveness values where the lowest specific energies were achieved. These results provide new insights into various aspects of cooling-lubrication methods in the pin grinding of cemented carbides. [ABSTRACT FROM AUTHOR]

Based on AgCuNiMn alloy, Ni/Cu/AgCuNiMn high-Ni solder was designed by in-situ synthesis. The WC-6Co/In718 joint was prepared by vacuum brazing at 950 °C for 10 min. The effect of metal foil on the filler metal filling ability, microstructure and mechanical properties of the joint was studied. The microstructure evolution and strengthening mechanism of the joint brazed with Ni/Cu/AgCuNiMn solder were analysed. The results showed that Ni element mainly plays a solution-strengthening role on the joint, and improve the interface bonding strength and the strength of Ag (s, s) distributed in the centre of the brazed joint, which increased the average tensile strength by 32.4% (from 426.5 to 564.7 MPa). [ABSTRACT FROM AUTHOR]

WC-based cemented carbides were prepared by spark plasma sintering (SPS) of WC-Co-Cr3C2-VC alloy powder by adding different contents of graphene. The phase composition, microstructure, mechanical properties, and magnetic properties of cemented carbide were investigated by means of XRD, SEM, Vickers hardness and fracture toughness tests, and magnetic properties tests. The results showed that the mechanical properties of the specimens show a trend of first increasing and then decreasing with the increase in graphene content. After adding 0.6 wt.% graphene, graphene is uniformly distributed on the substrate in the form of flakes, WC grain size decreases, the hardness of the specimen increases to 2009 HV, the relative density increases to 94.3%, the fracture toughness is 11.72 MPa·m1/2, and the coercivity of the sample is 437.55 Oe. Therefore, cemented carbide with a graphene content of 0.6 wt.% has excellent comprehensive performance (Vickers hardness and fracture toughness). [ABSTRACT FROM AUTHOR]

Commonly used tool materials for machining wood-based materials are WC-Co carbides. Although they have been known for a long time, there is still much development in the field of sintered tool materials, especially WC-Co carbides and superhard materials. The use of new manufacturing methods (such as FAST—field-assisted sintering technology), which use pulses of electric current for heating, can improve the properties of the materials used for cutting tools, thereby increasing the cost-effectiveness of machining. The ability to increase tool life without the downtime associated with tool wear allows significant cost savings, particularly in mass production. This paper presents the results of a study of the effect of grain size and cobalt content of carbide tool sinters on the tribological properties of the materials studied. The powders used for consolidation were characterised by irregular shape and formed agglomerates of different sizes. Tribological tests were carried out using the T-01 (ball-on-disc) method. In order to determine the wear kinetics, the entire friction path was divided into 15 cycles of 200 m and the weight loss was measured after each stage. In order to determine the mechanism and intensity of wear of the tested materials under technically dry friction conditions, the surface of the tested sinters was observed before the test and after 5, 10, and 15 cycles. The conclusions of the study indicate that the predominant effect of surface cooperation at the friction node is abrasion due to the material chipping that occurs during the process. The results confirm the influence of sintered grain size and cobalt content on durability. In the context of the application of the materials in question for cutting tools, it can be pointed out that sintered WC(0.4)_4 has the highest potential for use in the manufacture of cutting tools. [ABSTRACT FROM AUTHOR]

A series of WC‐based cemented carbides with Nb/TiC/TaC/VC and Co was prepared through spark plasma sintering (SPS) at a low sintering temperature of 1300°C, and their microstructures and mechanical properties were investigated. The nonstoichiometric multicomponent carbide Nb/TiC/TaC/VC with a rock‐salt structure (Fm3¯m$Fm\bar{3}m$) has a high atomic solution capacity. In the sintering process, partial WC and Co may dissolve in Nb/TiC/TaC/VC. With a high concentration of carbon vacancies, Nb/TiC/TaC/VC plays a beneficial role as a mass transfer intermediary. Good mass transfer facilitates the formation of a more accommodating and stable bonding between WC, Nb/TiC/TaC/VC, and Co, thereby preserving the hardness of the sintered bulks and preventing the initiation and propagation of cracks. When 6 wt.% Nb/TiC/TaC/VC and 4 wt.% Co are added to WC, the sintered bulk with fine grains exhibits superior hardness (23.27 ±.63 GPa) and toughness (10.45 ±.56 MPa·m1/2). [ABSTRACT FROM AUTHOR]

The WC‒20Fe, WC‒20Ni, and WC‒20Co cemented carbides were prepared by gas pressure sintering at 1450 ℃ using the WC powders with the theoretical carbon content (mass fraction). The effects of metal binders on the microstructure and mechanical properties of the cemented carbides were investigated by X-ray diffractometer (XRD), scanning electron microscope (SEM), electron probe microanalysis (EPMA), and mechanical properties tester. The results show that, the brittle η-phase (Fe3W3C) appears in the WC‒20Fe alloys, and finer grains are observed due to the lower solubility of W (1.915% by mass) in Fe binder. However, the graphite phase (C) is detected in the WC‒20Co alloys, the solubility of W in Ni binder can reach to 10.753% by mass, resulting in the largest grain size and the lowest hardness. The WC‒20Co alloys show the two-phase region (WC+γ), which exhibit the highest bending strength and hardness of 2720 MPa and 934.41 kg∙mm‒2, respectively. The fracture mode of all the alloys can be described as the brittle fracture and intergranular fracture. Moreover, the fracture surface of the WC‒20Co alloys shows the obvious binder tearing character.

Hardmetals are materials employed to produce cutting and forming tools as well as wear resistant parts. Standard powder metallurgy suffers limitations in the manufacturing of shapes required by application-oriented design. Therefore, there is interest for the implementation of additive manufacturing, in particular low temperature techniques as binder jetting because they allow to preserve microstructures and peculiar properties. In our work, the powder was tungsten carbide with 12 wt.% cobalt (WC-Co). Shaping by binder jetting was followed by curing treatment to promote the binder polymerization, vacuum sintering and sinter-HIP to achieve near-full density. The powder was analysed in terms of size and shape, to determine its suitability for the procedure. Then, the effects of different combinations of printing parameters, layer thickness (50–100 μm) and binder saturation (60/75/90%), on the density of the green bodies were analysed. Finally, the relative density of the sintered components was measured and the pores shape and size were studied by SEM imaging, to assess possible consequences of the deposition procedure. Vickers hardness along the samples cross-section was measured and correlated to the printing conditions employed.

WC–Co cemented carbides build one of the important classes of metal matrix composites. We show in this paper that the use of machine vision methods makes it possible to obtain sufficiently informative statistical data on the topology of the interfaces between tungsten carbide grains (WC) and a cobalt matrix (Co). For the first time, the outlines of the regions of the cobalt binder were chosen as a tool for describing the structure of cemented carbides. Numerical processing of micrographs of cross sections of three WC–Co alloys, which differ in the average grain size, was carried out. The distribution density of the angles in the contours of cobalt "lakes" is bimodal. The peaks close to 110° (so-called outcoming angles) correspond to the contacts between the cobalt binder and the WC/WC grain boundaries. The peaks close to 240° (or incoming angles) correspond to the WC "capes" contacting the cobalt "lakes" and are determined by the angles between facets of WC crystallites. The distribution density of the linear dimensions of the regions of the cobalt binder, approximated with ellipses, were also obtained. The distribution density exponentially decreases with the lengths of the semi-axes of the ellipsoid, approximating the area of the cobalt binder. The possible connection between the obtained data on the shape of cobalt areas and the crack trajectories in cemented carbides is discussed. [ABSTRACT FROM AUTHOR]

In this work, ruthenium (Ru) was used as an additive for improving the microstructure, mechanical, corrosion and oxidation behaviors of WC-15Co alloy. By analysis, Ru could facilitate the formation of cubic carbides free layer (CCFL), refine the WC crystallite size and enhance the anti-corrosion and anti-oxidation abilities of alloy. The highest hardness, fracture toughness as well as transverse rupture strength (TRS) values of alloys could be obtained by adding 3.0 wt% Ru at the same time. However, all of these properties decreased simultaneously when the Ru content exceeded 3.0 wt%. For corrosion and oxidation behaviors, when the Ru content was 5.0 wt% , the anti-corrosion and anti-oxidation abilities of alloy were the strongest. Thus, an appropriate amount of Ru was regarded as an excellent additive for enhancing the properties of cemented carbides. The strengthening mechanism of Ru was attributed to grain refinement, solution strengthening and the formation of dense oxides (Co 3 O 4 and CoWO 4). [ABSTRACT FROM AUTHOR]

WC–Co cemented carbides were prepared via an in situ synthesis method, including the carbothermal prereduction of WO3 and Co2O3 to remove all oxygen and a subsequent carbonization‐vacuum sintering process. The experimental results revealed that as the prereduction temperature increased from 1000 to 1200°C, the grain sizes of WC in WC–6Co and WC–12Co cemented carbides increased from.91 to 1.09 and.97 to 1.19 μm, respectively. Further, the fracture toughness of the sintered WC–6Co and WC–12Co cemented carbides increased from 9.97 to 10.83 and 11.11 to 18.30 MPa m1/2, respectively. In contrast, the hardness of the WC–6Co and WC–12Co cemented carbides decreased from 1477 to 1368 and 1351 to 1184 HV30, respectively. For a given prereduction temperature, an increase in Co content can improve the fracture toughness while lowering the hardness. In addition, an increase in the prereduction temperature or Co content led to an increase in the grain size of WC, which resulted in a transgranular fracture as the dominant mode. [ABSTRACT FROM AUTHOR]

The research aims to develop a novel and safer milling route to produce Hard Metals. Considering the risks associated with milling fine particles under organic solvents, especially the increased fire and explosion risks, we propose milling under aqueous milling media to diminish the risks associated with fire hazards, while maintaining the oxidation level at a minimum. The samples were sintered in an industrial sintering oven under vacuum at 1380°C subsequent to milling and drying. The characterisation of the materials has been done by X-ray diffraction, scanning electron microscopy, particle size analysis, optical microscopy, and a magnetometer. The obtained results indicate that appropriate properties of the powders after milling and drying as well as the desired biphasic (Co-WC) phases were obtained after sintering, thus proving the feasibility of such a route and diminishing specific fire hazards. [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]

Microcrystalline wax was mixed with the WC–10Co (YG10) powders to obtain the injection molding feedstocks as the main component of the binders. The non-Newtonian index, viscous flow activation energy, and synthetic rheological factor of the feedstocks were calculated by linear fitting, and the rheological properties of the feedstocks at the different temperatures and shear rates were investigated. The kinetic behavior of the solvent debinding for green bodies was investigated by analyzing the weight loss of the green bodies in the different debinding solvents at the different temperatures. The results show that, the microcrystalline wax based feedstocks exhibit the shear thinning characteristics of pseudoplastic fluid. The feedstocks have the stable sensitivity to the shear rate and temperature fluctuation, and show the good comprehensive rheological properties. The removal of soluble binder components mainly occurs in the pre-solvent debinding stage, which is controlled by diffusion, and the diffusion coefficient increases with the decrease of the thickness and volume of the green body and the increase of the debinding temperature.

The friction process of the WC–Co cemented carbides in the different conditions was investigated by molecular dynamics simulation in this work. The effects of grain size, friction load, and sliding velocity on the friction and wear behavior of the cemented carbides were analyzed. The friction and wear microscopic mechanism of the cemented carbides in the atomic scale was revealed. The results show that, with the increase of grain size, the dislocation slip in the Co and WC phases gradually plays more important role in the friction-induced plastic deformation mechanism rather than the grain rotation. The increase of friction load may lead to the deformable Co bonding phase being extruded from the surface and removed first. Nonetheless, the extrusion-wear mechanism of the Co phase can be suppressed by reducing the WC grain size, and the sliding wear resistance of the cemented carbides can be improved. Besides, the increase of sliding rate may reduce the wear rate. The main reason is that, in the process of high-speed sliding, the nucleation and expansion of dislocation in each phase of the subsurface layer lacks the continuous driving stress, and the dislocation density is low. Therefore, WC is difficult to fracture, and the wear degree caused by Co phase being extruded from the surface is significantly reduced.

Hardmetals (or cemented carbides) were invented a hundred years ago and became one of the most important materials in engineering. The unique conjunction of fracture toughness, abrasion resistance and hardness makes WC-Co cemented carbides irreplaceable for numerous applications. As a rule, the WC crystallites in the sintered WC-Co hardmetals are perfectly faceted and possess a truncated trigonal prism shape. However, the so-called faceting–roughening phase transition can force the flat (faceted) surfaces or interfaces to become curved. In this review, we analyze how different factors can influence the (faceted) shape of WC crystallites in the cemented carbides. Among these factors are the modification of fabrication parameters of usual WC-Co cemented carbides; alloying of conventional cobalt binder using various metals; alloying of cobalt binder using nitrides, borides, carbides, silicides, oxides; and substitution of cobalt with other binders, including high entropy alloys (HEAs). The faceting–roughening phase transition of WC/binder interfaces and its influence on the properties of cemented carbides is also discussed. In particular, the increase in the hardness and fracture toughness of cemented carbides correlates with transition of WC crystallites from a faceted to a rounded shape. [ABSTRACT FROM AUTHOR]

WC–Fe–Ni‐cemented carbides are prepared by hot oscillating pressing (HOP) and hot pressing (HP). Compared with the sample prepared by applying HP, the sample prepared by HOP shows higher density, lower carbide contiguity, more uniform distribution of binder phase, and finer WC grains. The average grain size of the HOP sample is 0.54 μm, where that of the HP sample is 0.67 μm. Moreover, the content of W in the binder phase is higher in the HOP sample than in the HP sample. The HOP sample exhibits a hardness of 2080 MPa and a fracture toughness of 15.95 MPa.m1/2, which are not only higher than those of the HP sample, but also higher than those of the WC–10Co alloys reported previously. The improvement in the mechanical properties is likely due to that the oscillatory pressure enhanced the flow of the liquid binder phase as well as influenced dissolution and re‐precipitation during densification process. Herein, it is indicated that HOP is an effective technique for the preparation of cemented carbides having high hardness and high toughness. [ABSTRACT FROM AUTHOR]

Wear-yet impact-resistant demand is a big challenge for coated components under heavy-load service condition. To solve this high-performance manufacturing problem, a new strategy of design for manufacturing (DFM) with integrated design and processing is developed to incorporate processing effect on final performance via the pivot role of surface integrity. An impact performance model and the impact tester are constructed for a component with coated flat block/bulk cylinder mates for potential application in hydraulic machinery. A WC-12Ni/Ni60A two-layer coating on 17-4PH martensitic steel substrate is designed with thermal spray process. Impact crater depth, surface hardening, and residual stresses are identified as major surface integrity parameters determining wear/impact performance by the modeling with testing. The design parameters of geometry, material, and structure are quantitatively linked to the final performance by a process signature (PS) correlative analysis on the identified surface integrity to internal material loading of plastic/elastic strain energies. The PS correlation posts coating thickness as a high-sensitivity parameter for design, facilitating a buffering effect of reduced peak stresses among the coating-substrate system. The DFM optimization is understood by irreversible thermodynamics as reducing energy dissipation of the internal material loading from the external impact loads. The manufacturing inverse problem is thus solved by material-oriented regularization (MOR) on the homologous PS correlations integrating the design and processing phases. The manufactured component, with optimal Ni60A interlayer thickness of 75-100 µm at a top WC-12Ni coating of 200 µm, achieves a desired performance of up to 6000 impacts under a nominal load of 15 kN. [ABSTRACT FROM AUTHOR]

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Excellent thermal conductivity is beneficial for the fast heat release during service of cemented carbides. Thus, thermal conductivity is a significant property of cemented carbides, considerably affecting their service life. Still, there is a lack of systematic investigation into the thermal conductivity of two-phase WC-Co-Ni cemented carbides. To remedy this situation, we integrated experiments and models to study its thermal conductivity varying the phase composition, temperature and WC grain size. To conduct the experiments, WC-Co-Ni samples with two-phase structure were designed via the CALPHAD (Calculation of Phase Diagrams) approach and then prepared via the liquid-phase sintering process. Key thermal conductivity measurements of these prepared samples were then taken via LFA (Laser Flash Analysis). As for modeling, the thermal conductivities of (Co, Ni) binder phase and WC hard phase were firstly evaluated through our previously developed models for single-phase solid solutions. Integrating the present key measurements and models, the values of ITR (Interface Thermal Resistance) between WC hard phase and (Co, Ni) binder phase were evaluated and thus the model to calculate thermal conductivity of two-phase WC-Co-Ni was established. Meanwhile, this model was verified to be reliable through comparing the model-evaluated thermal conductivities with the experimental data. Furthermore, using this developed model, the thermal conductivity of two-phase WC-Co-Ni varying with phase-fraction, temperature and grain size of WC was predicted, which can contribute to its design for obtaining desired thermal conductivities. [ABSTRACT FROM AUTHOR]

One of the possible ways to improve performance properties of WC-Co cemented carbides for different applications is known to be adding insignificant amounts of tantalum carbide. Performance of mining tools is noticeably improved as a result of small additions of TaC, so that some companies produce WC-TaC-Co grades for mining applications. Despite clear experimental evidence of the positive influence of small TaC additions on the properties and performance of WC-Co cemented carbides, the mechanism of this influence is presently not understood. In the present work a new viewpoint of the influence mechanism of small TaC additions of performance of WC-Co cemented carbides was elaborated. It was established that small amounts of TaC added to WC-Co cemented carbides form an oversaturated solid solution of tantalum in cobalt when solidifying the liquid binder during cooling from sintering temperatures. This solid solution decomposes when further cooling in the solid state resulting in the formation of (Ta,W)C nanoplatelets and rounded nanoparticles embedded in the binder matrix. The effectiveness of cemented carbide with such a nanograin reinforced binder is assumed to be similar to that of the well-known cemented carbides with the binder reinforced by hard metastable W-Co-C nanoparticles implemented in industry about 20 years ago. The production of the cemented carbides with the (Ta,W)C nanograin reinforce binder is more economical and consistent, which ensures the more sustainable manufacture, and the nanoprecipitates are stable at elevated temperatures. [Display omitted] • WC-Co cemented carbides with small additions of TaC were produced and examined. • The binder of WC-TaC-Co cemented carbides contain (Ta,W)C nanoprecipitates. • The nanoprecipitates are in form rounded nanograins and nanoplatelets. • The nanoprecipitates form in the solid-state during cooling from sintering temperatures. • Presence of nanoprecipitates in the binder leads to better performance of WC-TaC-Co materials. [ABSTRACT FROM AUTHOR]

For cemented carbides, also known as hardmetals, fracture toughness has always been viewed as one of the key properties, which resulted in large amount of research in the subject. This study presents fracture toughness results for 30 cemented carbide grades, covering wide range of microstructures and associated properties. Toughness data was generated at room temperature by three-point bend testing of chevron notched samples. In addition to relatively well studied influences of cobalt content and carbides grain size on fracture toughness, current research also examines impacts of cubic carbides content and alloying elements on material toughness. In this work, traditional "hardness - toughness" diagram is complemented by "coercivity - toughness", which is shown to be more appropriate for illustration of the detrimental effect that cubic carbides have on fracture toughness. The results presented here also indicate that alloying of binder with Cr or Ru does not have any noticeable effect on room temperature toughness and presence of eta-phase in the microstructure is not necessarily harmful for toughness. In addition, this research illustrates a correlation between fracture toughness and thermal conductivity of cemented carbides. Most importantly, by utilising broad experimental data and regression analysis, an attempt is made to formulate a set of empirical equations that would allow fracture toughness estimate from readily available or easily measurable material parameters. It is shown that fracture toughness of cemented carbides can be predicted with good accuracy from coercivity and cubic carbides content. In addition, regression equations for estimate of hardness and the average carbides grain size are proposed. • Fracture toughness of cemented carbides with wide range of microstructures. • Correlations of toughness with hardness, coercivity and thermal conductivity. • Influence of WC grain size, binder content and cubic carbides fraction on toughness. • Effect of Cr, Ru and eta-phase in the binder on fracture toughness of hardmetals. • Simple prediction of K 1C and HV with empirical equations using magnetic properties. [ABSTRACT FROM AUTHOR]

The WC-10Co cemented carbides containing (ZrHfNbTaTiMo)C high-entropy carbide with satisfactory comprehensive mechanical properties were successfully manufactured by conventional vacuum sintering. The influences of (ZrHfNbTaTiMo)C contents (0, 0.5, 1, 5, 10 wt.%) on the densification degree, microstructure, grain size and mechanical properties were investigated. The results showed that the addition of (ZrHfNbTaTiMo)C deteriorated the wettability between Co and WC, leading to a decline in relative density. (ZrHfNbTaTiMo)C inhibited the growth of WC grains, and the average grain size of WC continued to decrease with the increase of (ZrHfNbTaTiMo)C content. After adding (ZrHfNbTaTiMo)C, the hardness and toughness rose first and then descended. When the content of (ZrHfNbTaTiMo)C was 1 wt.%, the hardness and toughness reached the maximum value of 16.77 GPa and 10.45 MPa·m1/2, respectively. Moreover, the structure was a dual-grain structure, with many high-aspect-ratio rectangular grains in the sintered samples added by 0.5 wt.% and 1 wt.% (ZrHfNbTaTiMo)C. This special structure not only enhanced the hardness, but also compensated the loss of toughness. After doping 0.5 wt.% CeO2, the hardness decreased slightly, while the toughness increased to 12.42%. [ABSTRACT FROM AUTHOR]

[Display omitted] • Grain growth rate in NbC-Ni cemented carbides is decreased by the addition of Mo secondary carbides. • Interface migration is controlled by grain boundaries and grain growth rate decreases with with the carbide contiguity. • Grain boundary segregation also contribute to reduce grain growth rate. Cemented carbides are widely used for cutting and drilling tools. They usually combine a WC hard carbide phase and a Co-based ductile binder. NbC-Ni materials are considered as a possible alternative, especially for wear applications. The advantageous economic situation for raw materials sourcing, their interesting mechanical properties and low density have raised a new interest for these materials. However, mechanical properties can be limited by the rapid grain growth during liquid phase sintering, as compared to WC-Co. Grain growth can be controlled by the addition of secondary carbides. In this paper, a quantitative EBSD analysis of grain growth is performed for NbC-12 vol%Ni materials sintered at 1450 °C with controlled addition of Mo 2 C and WC. The average grain size decreases continuously with Mo 2 C addition. The results are discussed based on a more detailed interface characterization and on a previous model for the cooperative migration of phase boundaries and grain boundaries. [ABSTRACT FROM AUTHOR]

This study investigates the influence of different sinter-HIP temperatures and binder saturation levels on the microstructure and properties of WC–12Co cemented carbide, produced using binder jetting. The sinter-HIP process was performed at 1400 °C, 1460 °C, and 1500 °C and binder saturation levels of 60% and 75% were selected during printing. The binder saturation proved to affect the repeatability of the manufacturing process and the sturdiness of the green models. The increase of the sintering temperature from 1400 °C to 1460 °C is correlated with an increase in the density. Nonetheless, a further raise in temperature to 1500 °C leads to significant grain coarsening without clear advantages in terms of porosity reduction. Both the transverse rupture strength and Vickers hardness increase when the sinter-HIP temperature rises from 1400 °C to 1460 °C, where the typical results for traditionally manufactured WC–12Co are met, with a comparable grain size. The transverse rupture strength and Vickers hardness then decrease for samples treated at 1500 °C. Finally, potential issues in the manufacturing process are identified and correlated with the defects in the final components.

Integrated Computational Materials Engineering (ICME) has proved to be an efficient tool for understanding the process-structure–property relationships and helping us to design materials. For instance, in cemented carbides manufacturing, one of the most critical parameters is the C-window. It is defined as the C content range for which phases detrimental to the mechanical properties are avoided. This processing window has been traditionally defined using applied thermodynamics methods. However, the deviation between equilibrium calculations and real manufacturing conditions requires big additional empirical efforts to precisely define the C-window. In this work, an ICME-based approach is proposed to redefine the processability limits of cemented carbides taking the cooling rate and the material’s initial powder size into consideration. The method relies on the interactive coupling of several adapted models and tools, to not only set the processability boundaries, but also to study the complex mechanisms interplay happening along microstructural evolution. A better understanding of these underlaying mechanisms leads to new inputs that can be used in the design of cemented carbides. In this regard, it is observed that faster cooling rates or coarser WC grades could be effectively used to prevent nucleation of the detrimental phases enlarging the C-window towards lower C contents.