Properties Of Tungsten Carbide Research Articles

Influence of cryo-processing on properties of tungsten carbide with low, medium and high cobalt content

This research was designed to evaluate the influence of cryo-processing on properties of tungsten carbide with varied cobalt content. Samples of uncoated tungsten carbide with 6% (WC-6 wt%Co), 9% (WC-9 wt%Co) and 25% cobalt (WC-25 wt%Co) content were fabricated for the research. Magnetic properties, porosity analysis, eta phase analysis by microscopic observation, EDS, XRD and Vickers hardness were evaluated. Investigation shows that 25% cobalt content samples after cryo-processing exhibit a significant improvement of around 2.2% in Vickers hardness and 8.7% in coercivity followed by samples with 9% cobalt grade (1.2% increase in Vickers hardness and 2.1% in coercivity), whereas 6% cobalt samples showed negligible changes. There is no change in the other properties in any of the selected grades. The change in Vickers hardness and coercivity are attributed to the cobalt’s phase transformation from FCC to HCP structure in cryo-processed samples. This study reveals that the amount of cobalt used in the fabrication of tungsten carbide tools is the determinant factor for the changes in properties.

Enhancement of mechanical and wear properties of tungsten carbide coated AA 6063 alloy using detonation gun technique

ABSTRACTAluminium 6063 alloy as substrate was coated with WC-12% Co using the detonation spray gun technique. The coated specimen showed 5.6x increase in hardness over the uncoated substrate. Wear analysis was conducted on the coated specimen based on Taguchi’s L27 orthogonal by taking load (10, 20, 30 N), sliding velocity (1, 2, 3 m s−1) and sliding distance (750, 1250, 1750 m) as parameters. Wear rate was observed to increase with an increase in load and sliding velocity, whereas initial increase and a subsequent decrease in wear rate was observed with an increase in sliding distance. Analysis of variance predicted that load has a higher influence on the loss of material. Load and sliding distance interaction showed a high influence over loss of material than any other individual parameter’s influence. SEM and XRD analysis was conducted over worn surfaces to help elucidate the wear mechanism. The results from the present work may find application in piston rings and cylinder liners.

Effects of Mechanical Alloying on Sintering Behavior of Tungsten Carbide-Cobalt Hard Metal System

During the last few years, efforts have been made to improve the properties of tungsten carbides (WCs) by preparing composite materials. In this study, we prepared WC particles by mechanical alloying and investigated the effects of mechanical alloying conditions, such as mechanical alloying time and mechanically alloyed powder ratio, on the properties of 94WC-6Co. According to experimental studies, increasing the mechanical alloying time causes an increase in the density of tungsten carbide samples and a decrease of crystal sizes and inner strength of the prepared materials. With the increase of mechanical alloying time, fine particle concentrations of tungsten carbide samples have increased. It is observed that increasing the mechanical alloying time caused a decrease of the particle surface area of tungsten carbide samples. Besides, the amount of specific phases such as Co3W3C and Co6W6C increases with increasing mechanical alloying time. As another subject of this study, increasing the concentration of mechanically alloyed tungsten carbides caused an increase in the densities of final tungsten carbide materials. With the concentrations of mechanically alloyed materials, the occurrence of Co6W6C and Co3W3C phases and the increase of crystallization are observed.

Effect of heat treatment on the structural properties of tungsten carbide coatings deposited by RF magnetron sputtering

A systematic study on the effect of heat treatment on the structural properties of tungsten carbides coatings deposited by RF magnetron sputtering on steel substrate (XC70) was carried out. These coatings were subjected to heat treatment in vacuum at various temperatures ranging from 500 to 1000 °C for 25 min. Structural analysis of the as-deposited and heat-treated coatings was performed by means of X-ray diffraction (XRD) and optical microscopy. The XRD analyses indicated the presence of nanocrystalline grains with (222) preferential orientation. The grain size varied from 8 to 15 nm. The presence of two different phases WC and W2C was observed in the coatings heat treated at 1000 °C. The effect of the annealing temperature on the surface morphology of the coatings was studied using optical microscopy.

Role of Tungsten Carbide Reinforcement on Alumina Matrix Composites Fabricated by Powder Injection Moulding

In this work, properties of tungsten carbide (WC) particulate reinforced alumina matrix composites fabricated by powder injection moulding (PIM) technology were reported. The 90 wt% of Al2O3 and 10 wt% of WC powders were mixed with a composite binder, composed of 85 wt% polyethylene glycol (PEG) and 15 wt% polyvinyl butyral (PVB). Feedstocks of alumina and alumina-tungsten carbide composites having powder loading from 44 to 52 vol% were prepared and injected into a mould of rectangular shape. The binders in the mouldings were leached by water and then thermally debinded prior to sintering at 1600 °C for 2 hours in argon atmosphere. Strength, Density, hardness and density of the alumina and alumina composites’ bodies were compared and reported. It was found that the properties of sintered specimens, both Al2O3 and Al2O3/WC composites, increased with increasing powder loadings. The properties enhancement was also presented in the WC reinforced alumina composites. The composite of 52 vol% powder loading had flexural strength and hardness of 253.8 MPa and 12.5 GPa, respectively.

Electronic properties of WC nano-compound: Compton spectroscopy and band structure calculations

We present the electronic properties of tungsten carbide (WC) nano-compound using the Compton scattering technique. We have measured the Compton profile (CP) of nano-powder using our 137Cs Compton spectrometer. To determine the theoretical CPs of WC nano-compound, we have employed linear combination of atomic orbitals (LCAO) with Hartree-Fock and density functional theory. Although all the LCAO-based calculations show similar agreement with the experiment, the second-order generalised gradient approximation gives a marginally better agreement with the measured CP data. Layered structures and slight over-lapping in energy bands show a small role of exchange and correlation potentials in case of WC nano-compound, which is in contrast to bulk WC.

Strain Rate Dependency of Bronze Metal Matrix Composite Mechanical Properties as a Function of Casting Technique

Strain rate dependency of mechanical properties of tungsten carbide (WC)-filled bronze castings fabricated by centrifugal and sedimentation-casting techniques are examined, in this study. Both casting techniques are an attempt to produce a functionally graded material with high wear resistance at a chosen surface. Potential applications of such materials include shaft bushings, electrical contact surfaces, and brake rotors. Knowledge of strain rate-dependent mechanical properties is recommended for predicting component response due to dynamic loading or impact events. A brief overview of the casting techniques for the materials considered in this study is followed by an explanation of the test matrix and testing techniques. Hardness testing, density measurement, and determination of the volume fraction of WC particles are performed throughout the castings using both image analysis and optical microscopy. The effects of particle filling on mechanical properties are first evaluated through a microhardness survey of the castings. The volume fraction of WC particles is validated using a thorough density survey and a rule-of-mixtures model. Split Hopkinson Pressure Bar (SHPB) testing of various volume fraction specimens is conducted to determine strain dependence of mechanical properties and to compare the process-property relationships between the two casting techniques. The baseline performances of C95400 bronze are provided for comparison. The results show that the addition of WC particles improves microhardness significantly for the centrifugally cast specimens, and, to a lesser extent, in the sedimentation-cast specimens, largely because the WC particles are more concentrated as a result of the centrifugal-casting process. Both metal matrix composites (MMCs) demonstrate strain rate dependency, with sedimentation casting having a greater, but variable, effects on material response. This difference is attributed to legacy effects from the casting process, namely, porosity and localized WC particle grouping.

Tungsten carbide (WC) synthesis from novel precursors

This paper deals with the production and properties of tungsten carbide (WC) powders from novel carbon coated precursors. The process has two steps in which the oxide powders were first coated with carbon by cracking of a hydrocarbon gas, propylene (C3H6), secondly mixed with a substantial amount of carbon black, and finally treated at temperatures in the range of 600-1400°C for 2 h in flowing Ar or 10% H2-Ar atmosphere to synthesize WC. The produced powders were characterized using TEM, BET surface area analyzer, X-ray diffraction and chemical analysis (oxygen and carbon). The results obtained for various types of precursors treated in different atmospheres indicated that the coated precursors produced high quality powders. Single phase, submicron WC powders were synthesized at temperatures as low as 1100°C. WC powders produced at 1400°C for 2 h in flowing 10%H2-Ar gas mixture were submicron (3–5 m2/g), single phase, and had low oxygen content (0.2–0.5 wt%). The sintering tests demonstrated that these powders can be densified to near theoretical density using 20 wt% Co binder at 1500°C for 2 h in flowing 10%H2-Ar atmosphere.

Structure and properties of tungsten carbide obtained by electric-discharge sintering of a disperse powder

Samples of highly dispersed tungsten carbide powders of various origins were obtained by electrical-discharge sintering. The specimens were 8 mm in diameter, 5 mm in height and had a grain size of 1 µm, density 15.5–15.8 g/cm3, hardness 92–93 HRA, and cracking resistance 6–8 MPa·m1/2. The structure and phase composition of the sintered samples was not observed to change appreciably from those of the initial powder. The salient features of electrical-discharge sintering of tungsten carbide power are described.

Catalytic activity and XPS surface determination of tungsten carbide for hydrocarbon reforming. Influence of the oxygen

The influence of oxygen on the catalytic properties of tungsten carbide has been studied for the reforming reaction of 2-methylpentane in a great excess of hydrogen\(\left( {P_{H_2 } /P_{HC} = 150} \right)\). The oxygen surface concentration has been measured by the ratio of the signal area of the O1s and the W4f levels as determined by X-ray photoelectron spectroscopy. Two kinds of processes are observed: cracking and isomerization reactions. The introduction of oxygen at T=350°C leads to a deep decrease of the cracking reaction kinetics; about two orders of magnitude. The tungsten carbide, strongly selective for cracking reactions in absence of oxygen, becomes very selective for isomer production in the presence of oxygen.