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Cemented tungsten carbide yields plastically at room temperature in the presence of a large hydrostatic pressure component. By approximate analysis of the state of stress in supported opposed anvils and by measurement of the pressure at which the anvil tips exhibit a permanent deviation from planarity, we have obtained the yield stress of such materials. Our value for the yield stress of a 3% cobalt cemented tungsten carbide is 86 kbar.
In this study, shock wave experiments are conducted on General Carbide cemented tungsten carbide with 3.7wt.% cobalt binder to determine its shock-induced compression behavior up to 100 GPa. The measured wave profiles indicate the cemented tungsten carbide to undergo elastic-plastic deformation during shock compression. A three-stage particle velocity profile is observed in the experiments -- an initial elastic-rise to the Hugoniot Elastic Limit (HEL), an elastic-plastic ramp indicating substantial post-yield hardening, and finally a rise to the peak shocked Hugoniot state. The results of the experiments are used to determine the HEL, the shock velocity (U s ) vs. particle velocity (u p ) Hugoniot relation, and the longitudinal stress (σ x ) vs. specific volume (V) curve for the samples. The HEL of the material was determined to lie between 4.41 GPa and 4.58 GPa. The U s - u p relation was determined to be U s = 4.97 + 1. 457u p for particle velocities greater than 0.75 km/s. The measured plastic shock velocities for particle velocities less than 0.7 km/s were found to be larger than those predicted using the linear U s - u p Hugoniot relationship, indicating the cemented WC samples to preserve substantial shear strength in the post-yield deformation region. No phase transformation was observed up to 100 GPa.
In the present study, shock wave experiments are conducted on General Carbide cemented tungsten carbides with 3.7 wt.% and 6.0 wt.% cobalt binder to determine their shock compression response up to 100 GPa. A three-stage particle velocity profile is observed in the experiments -- an initial elastic-rise to the Hugoniot elastic limit (HEL), an elastic-plastic ramp indicating post-yield hardening, and finally a rise to the peak shocked Hugoniot state. The results of the experiments are used to determine the HEL, shock velocity (U s ) vs. particle velocity (u p ) Hugoniot relationship, and the longitudinal stress vs. specific volume Hugoniot relationship for the two samples. Here, the HEL for the WC 3.7wt% Co and WC 6.0wt% Co samples was determined to be ~4.45 GPa and 3.72 GPa, respectively. The U s – u p relation was determined to be U s = 4.97(0.006)+1. 446 (0.018) u p for WC 3.7 wt.% Co and U s = 4.93(0.006)+1. 454(0.017)u p for the WC 6.0 wt.% Co sample at peak particle velocities>0.75 km/s. For both WC grades, in the particle velocity regime less than ~0.75 km/s, the measured shock wave velocities were found to be larger than those predicted by the linear U s –u p Hugoniot relationship, indicating the two WC samples to preserve substantial strength in the post-yield deformation regime. Both WC grades show a catastrophic drop in shear stress carrying capacity when shocked to longitudinal stresses greater than ~70 GPa.
The polymorphism of tungsten carbide (W x C) and the challenge of selectively synthesizing pure phases have impeded a precise understanding of catalytic structure−property relationships. This study establishes a framework for phase-selective synthesis of W x C through controlling carburization kinetics. By maintaining particle sizes below 10 nm, β-W 2 C is selectively synthesized using gaseous carbon precursors (CH 4 /H 2 ) via temperature-programmed carburization (TPC). Our findings reveal that W 2 C stabilization is predominantly dictated by particle size and carburization kinetics rather than support interactions, providing a tunable approach to synthesize tungsten carbide catalysts. We elucidate the mechanistic pathway of WO x carburization, demonstrating that CH 4 activation occurs at mild temperatures via lattice oxygen. Our reactor studies establish ex situ synthesized β- W 2 C as an active and stable catalyst for the reverse water-gas shift (RWGS) reaction. However, the need for passivation and reduction pretreatment leads to a complex surface structure with diminished intrinsic activity. In contrast, our in situ synthesis protocol for β-W 2 C eliminates the need for passivation and exhibits increased CO STY during RWGS, illustrating the intrinsically higher activity compared to metallic W, WC 1−x (0.5 < x < 1), and stoichiometric WC.
Tungsten carbide (WC) has the characteristics of high hardness, high strength, corrosion resistance, wear resistance and excellent fracture toughness. Accordingly, it has been commonly used as the material for cutting tools and molds in glass-forming techniques. To obtain ultra-smooth surfaces, fine polishing of WC is indispensable. However, the efficiency of WC polishing is low using the existing polishing methods, and the mechanism behind the polishing process requires further investigation. Specifically, the effect of the binder in WC polishing is not clear since there are different kinds of WC with various weight percentages of the binder. In this paper, we present the findings of a study on the polishing performance of two kinds of WC material, with and without the binder, using a semi-rigid (SR) bonnet polishing tool. A series of experiments were performed on a 6-DOF robotic polishing instrument to investigate the material-removal characteristics, surface integrity and sub-surface damage after polishing. The results demonstrate that the SR bonnet polishing tool successfully reduced the surface roughness of WC with and without the binder to the nanometric level, though the lowest surface roughness was obtained on binder-less WC. No obvious sub-surface damage was observed under SEM inspection, while the processing efficiency was greatly improved owing to the high material removal rate of the tool. Based on our analysis of key polishing parameters and corresponding surface integrities, the effect of the binder on the polishing performance is explained, which offers excellent guidance for WC polishing.
The feasibility of using ultrasonic attenuation measurements to rank tungsten carbide alloys according to their fracture toughness was demonstrated. Six samples of cobalt-cemented tungsten carbide (WC-Co) were examined. These varied in cobalt content from approximately 2 to 16 weight percent. The toughness generally increased with increasing cobalt content. Toughness was first determined by the Palmqvist and short rod fracture toughness tests. Subsequently, ultrasonic attenuation measurements were correlated with both these mechanical test methods. It is shown that there is a strong increase in ultrasonic attenuation corresponding to increased toughness of the WC-Co alloys. A correlation between attenuation and toughness exists for a wide range of ultrasonic frequencies. However, the best correlation for the WC-Co alloys occurs when the attenuation coefficient measured in the vicinity of 100 megahertz is compared with toughness as determined by the Palmqvist technique.
In the present study a thermodynamically-consistent finite-strain rate-and-pressure-dependent constitutive framework is implemented to analyze the shock-compression behavior of cemented tungsten carbides to 100 GPa. Central to this framework is the use of logarithmic strain with a set of invariant basis that allow the Cauchy stress tensor to be expressed as a sum of three response terms that are mutually orthogonal, thus permitting a complete separation of the deviatoric and volumetric (pressure) response. An overstress viscoplasticity model that includes strain and strain rate hardening along with thermal softening is used to represent the deviatoric response, while a complete Mie-Grüneisen equation of state (EoS) is used to obtain the pressure response. Using this formulation, the shock-induced compression behavior of cemented tungsten carbide - obtained from planar plate impact experiments using a 30 mm powder gun to peak stresses of up to ~100 GPa - is analyzed to better understand the structure of the measured shock wave profiles and the associated in-material shock quantities. Of particular interest is the evolution of material inelasticity and strength, and temperature in the tungsten carbide samples during the shock compression process.
Fabricating durable and high-performance electrocatalysts operating at high current densities for industrial acidic hydrogen evolution remains a daunting challenge. Tailoring the phase composition of electrocatalysts is a promising strategy to harness synergistic effects and improve charge transfer, thereby optimizing their performance. Here, this work presents a fast, green method based on flash joule heating (FJH) to synthesize phase-engineered tungsten carbide electrocatalysts for the acidic hydrogen evolution reaction (HER) at high current densities. Tungsten carbide electrodes with varying FJH treatment durations (3, 10, 30, and 60 s) are fabricated to fine-tune the mixture of tungsten monocarbide (WC) and tungsten semicarbide (W 2 C) phases. Results show that samples with a 30-s treatment (TC-3) exhibit an optimal balance between these phases, leading to a low overpotential of 180.97 and 387 mV at current densities of 10 mA/cm 2 and 4 A/cm 2 , respectively. TC-3 exhibits significantly lower charge transfer resistance compared to the other electrocatalysts, which can be attributed to its optimal phase ratio. Notably, the TC-3 electrocatalyst remains stable for over 9 days at 4 A/cm 2 due to their controlled phases and excellent corrosion-resistant properties. This work highlights a new method to fabricate cost-effective, high-performance tungsten carbide electrocatalysts with well-controlled phase compositions.
Dynamic friction and wear experiments were conducted in a scanning electron microscope. The wear behavior of pure tungsten carbide and composite with 6 and 15 weight percent cobalt binder was examined, and etching of the binder was done to selectively determine the role of the binder in the wear process. Dynamic experiments were conducted as the tungsten carbide (WC) and bonded WC cermet surfaces were transversed by a 50 micron radiused diamond stylus. These studies show that the predominant wear process in WC is fracture initiated by plastic deformation, and the wear of the etched cermets is similar to pure WC. The presence of the cobalt binder reduces both friction and wear. The cementing action of the cobalt reduces granular separation, and promotes a dense polished layer because of its low shear strength film-forming properties. The wear debris generated from unetched surface is approximately the same composition as the bulk.
To gain insights into thermodynamic states attained during shock compression of cemented tungsten carbide with 3.7 wt.% cobalt binder, we present results of longitudinal sound (release wave) speed measurements and their analysis at peak stresses up to 100 GPa (volumetric compression ratio ~ 15%). The sound speeds are determined using front-surface impact and release-wave overtake plate impact experimental configurations using laser interferometry. The measured sound speed data along with estimates for bulk sound speeds obtained using the fourth-order Birch-Murnaghan EoS and thermodynamics are used to determine the longitudinal moduli and shear moduli of shocked tungsten carbide at the various peak compression states attained in the experiments. Here, the longitudinal sound speeds were found to increase linearly with volume compression ratio from 6.97 ± 0.010 km/s at ambient conditions to 8.26 ± 0.156 km/s at a volume compression ratio of ~ 15%. The corresponding longitudinal elastic moduli also increase nearly linearly with the volume compression ratio but remain consistently lower than their theoretical predictions based on continuum models with no damage. Also, the sensitivity of shear moduli to pressure, as predicted by the Steinberg-Guinan model, is reduced substantially and the shear moduli of cemented WC with 3.7 wt.% Co remains nearly constant at ~ 310 GPa at the various peak compression stress states investigated in the present study.
Plate impact experiments are conducted on cemented tungsten carbides (WC) with a 3.7 and 6.0 wt. % cobalt binder to better understand their dynamic, high-pressure response to 100 GPa. The measured wave profiles show propagation of steady structured waves. Standard impedance matching procedures are used to determine the Hugoniot relations in the shock velocity–particle velocity (U s –v p ) and Hugoniot stress–specific volume (P–V/V o ) planes. The Hugoniot elastic limit of the samples is controlled by ductility of the Co binder and is determined to be 4.45 ± 0.29 GPa for cemented WC with 3.7 wt. % cobalt and 3.72 ± 0.24 GPa for a 6.0 wt. % cobalt binder. Both grades show a non-linear U s –v p relationship depending on whether the particle velocity is in the strength dominated or hydrodynamic regime. In the strength dominated regime, a non-linear decrease in U s is observed as v p increases from ambient to the material’s hydrodynamic limit. In the hydrodynamic regime, the U s –v p Hugoniot is linear and is determined to be U s = 4.97(±0.006)+1.446(±0.018)v p km/s for WC with 3.7 wt. % Co and U s = 4.93(±0.006)+1.463(±0.017)v p km/s for 6 wt. % Co. Both WC grades indicate shear-stress hardening with mean stress immediately after yield, followed by pressure softening, and then a sharp fall in stress carrying capacity as the mean stress is increased to ≈70 GPa (hydrodynamic limit) and beyond. This behavior is in contrast to pure WC ceramics, which show continued shear-stress hardening with mean stress to ≈80 GPa.
Dynamic friction and wear experiments were conducted in a scanning electron microscope. The wear behavior of pure tungsten carbide and composite with 6 and 15 weight percent cobalt binder was examined. Etching of the binder was done to selectively determine the role of the binder in the wear process. Dynamic experiments were conducted as the WC and bonded WC cermet surfaces were transversed by a 50 micron radiused diamond stylus. These studies show that the predominant wear process in WC is fracture initiated by plastic deformation. The wear of the etched cermets is similar to pure WC. The presence of the cobalt binder reduces both friction and wear. The cementing action of the cobalt reduces granular separation and promotes a dense polished layer because of its low shear strength film-forming properties. The wear debris generated from unetched surface is approximately the same composition as the bulk.
Neutron transport calculations have been performed on advanced shielding materials. Metal hydrides and borohydrides were evaluated to find an alternative to tungsten carbide (WC), which is used in the in-vessel components. The study was conducted using a 22.5° sector and a detailed 360° geometry of the Fusion Energy System Studies-Fusion Nuclear Science Facility (FESS-FNSF) using OpenMC and FENDL-3.2b nuclear data library. Here, the neutronics analysis in this article was concentrated on calculating total nuclear (neutron and photon) heating at the magnet and the radiation damage of the inboard vacuum vessel (IBVV). For example, yttrium hydride (YH 2 ) and vanadium hydride (VH 2 ) showed lower radiation damage values compared to WC and other metals. Whereas alternative shielding materials did not show a significant change in the magnet nuclear heating.
The motivation of the present study is to gain insights into the evolution of elastic properties of cemented tungsten carbides (WC) shock compressed to 100 GPa. Seven plate impact experiments—two front surface impact and five release wave overtake—are conducted to make simultaneous measurements of Hugoniot states and longitudinal sound speeds in shocked WC with 3.7wt.% cobalt binder. The sound speeds along with estimates for bulk sound speeds, obtained using the Birch–Murnaghan EoS, are analyzed to determine the elastic moduli—longitudinal, bulk, and shear—as a function of Hugoniot stress. The longitudinal and bulk sound speeds at Hugoniot states of interest are found to increase linearly with longitudinal stress. Consistent with the increase in sound speeds, the longitudinal and bulk moduli also increase with Hugoniot stress; however, the increase in longitudinal modulus is modest when compared to predictions of theoretical models that account for pressure and temperature dependence of elastic moduli, but with no damage. The shear moduli remain nearly constant at ~318 GPa over the range of Hugoniot states investigated. These values are, however, much lower than those predicted by the Steinberg–Guinan model with no damage. Poisson’s ratio decreases initially from its ambient value of 0.208 to ~0.199 for Hugoniot stress ≤10 GPa indicating consolidation of the WC microstructure with low initial stress; however, with an increase in Hugoniot stress to ~100 GPa, Poisson’s ratio increases to ~0.317, indicating degradation of shear moduli with increasing stress. The product of density and Grüneisen parameter (ρΓ), after an initial spike, remains nearly constant for volumetric strains ≥0.07. The maximum average temperature rise is estimated to be ~286°C at the highest Hugoniot stress employed in the study.
Hydrocracking is a promising route for the chemical recycling of polyolefins (PO), converting them into short hydrocarbons over bifunctional catalysts with metal sites for hydrogenation and dehydrogenation, and Brønsted acid sites (BAS) for isomerization and C–C bond cleavage. However, PO feedstocks containing polyvinyl chloride (PVC) can release chlorine (Cl) under reaction conditions, deactivating conventional noble metal/zeolite catalysts. Moreover, the lack of site intimacy and the presence of micropores within conventional catalysts create challenges around the transport of high-molecular-weight, sterically encumbered polymer intermediates. Here, in this study, we report tungsten carbides (W x C) as a novel type of bifunctional catalysts that address these challenges. W/W 2 C phases on W x C offer “metal” sites, and −OH on WO x species introduces BAS in close proximity. The “metal”:BAS ratio can be tuned through carburization temperature, leading to a volcano-shaped activity trend reflecting the requirement for metal–BAS balance. Kinetic data demonstrate that each PO chain undergoes sequential cleavage, while trends in cracking ideality and selectivity follow those in short-alkane hydrocracking. On the per-BAS basis, W x C is more efficient than conventional bifunctional catalysts by more than an order of magnitude, due to enhanced polymer transport. They maintain or show increased activity with 10 wt % PVC in the substrate. This work establishes transition-metal carbides as earth-abundant bifunctional catalysts with unique site proximity and heteroatom compatibility. These features, along with the broad structure space for rational tuning, make them promising options to tackle specific challenges that polymer feedstocks present in hydrocracking.
Here, strength, texture, and equation of state of hexagonal tungsten monocarbide (WC) have been determined under quasi-hydrostatic and non-hydrostatic compression to 66 GPa using angle-dispersive X-ray diffraction in the diamond anvil cell. Quasi-hydrostatic compression in a Ne pressure medium demonstrates that nanocrystalline WC is slightly less incompressible than bulk-scale WC, with respective bulk moduli of K 0 = 377 ± 7 and 397 ± 7 GPa and pressure derivatives K 0 ’ = 3.8 ± 0.3 and 3.7 ±0.3. This decrease in incompressibility with grain size is similar to behavior observed in other ceramics. Under nonhydrostatic compression, WC supports a mean differential stress of ~12-15 GPa at plastic yielding, which occurs at ~30 GPa. Strength in WC is anisotropic, with the (001) plane supporting 29-42% higher stress than stresses calculated from mean strain. Simulations using an Elasto-ViscoPlastic Self-Consistent model indicate that strength inferred from lattice strain theory may be overestimated due to effects of plastic deformation. Plastic deformation generates a texture maximum near $\langle\bar{2}110\rangle$ in the compression orientation, initially through prismatic slip on the {$10\bar{1}0$}$\langle\bar{1}2\bar{1}0\rangle$ and {$10\bar{1}0$}$\langle0001\rangle$ slip systems, followed by activation of pyramidal slip on {$10\bar{1}1$}$\langle\bar{2}113\rangle$ at ~40-50 GPa.
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Ultra High Temperature Metal Matrix Composites (UHT-MMCs) are of interest to the due to their potential defense and aerospace applications. These materials consist of a metal matrix reinforced with a stiff ceramic or cermet. Based on a preliminary literature survey, this project will focused on a pure titanium (Ti) matrix reinforced with tungsten carbide-cobalt (WC-Co). UHT-MMC technology is still at a nascent stage of development and requires extensive experimental work to optimize the structure and resulting material properties of a particular UHT-MMC material system. An accurate and complete high-performance computing (HPC) model of the Ti/WC-Co material system could greatly accelerate the development and deployment Ti/WC-Co materials by connecting processing parameters to material properties. This type of model could then be used in an integrated computational materials engineering approach to optimize the material structure to achieve a targeted level of performance.