Papers by Keyword: Tungsten Carbide

Abstract: Studies of a powder used as a modifier obtained from solid-alloy waste, such as tungsten carbide (drill balls), are presented. Dispersion, particle morphology and phase analysis of the powder were studied. The powder obtained from solid-alloy waste is a phase – it is tungsten carbide WC, it consists of nanoobjects of various shapes (nanoparticles, nanoplastics) up to 100 nm in size, with a slight presence of agglomerates up to 250 nm in size. The influence of tungsten carbide nanopowder as a modifier on the mechanical properties (strength and hardness) of PK70D3 iron-based powder structural steel has been studied. For the study, two different modes of preparation of powder alloy have been used with the use of one-stage and two-stage sintering. The influence of additive nanopowder of tungsten carbide on the mechanical properties of structural alloy powder based on iron PK70D3 has been defined: strength increases by more than 23% (in single-stage sintering), by more than 28% (in double-sintering), hardness decreases by more than 6% in single-stage sintering and increases by more than 26% with two stages of sintering, compared to the initial alloy. It has been shown that samples, obtained using double sintering with a tungsten nanopowder modifier (2.5%), have higher values of strength (more than 80%) and hardness (more than 13%), compared to modified samples, obtained by single-stage sintering technology. Thus, the modification of a 2.5 % nanoprobe of tungsten carbide, a widely used structural powder alloy based on iron PC70D3 allows for a significant change in mechanical properties. The use of powder alloys in double sintering technology provides the material hardness and the strength increase.

Abstract: The WC composite powder was synthesized by a new specific chemical activation technique. A large number of lattice defects such as surface humps, dislocations and stacking fault exist in the surface of the WC powder after chemical activation technique. By using such activated WC powder, the binderless WC cemented carbide with high density (15.54 g/cm³), super hardness (average 26.29 GPa) and excellent fracture toughness (8.9 MPa.m^1/2) can be fabricated by SPS at 1700 °C and 50 MPa pressure. The improvement in density, hardness and fracture toughness are respectively 4.5%, 15.3% and 17.1% compared to when using the original WC powder. This improvement is because microscopic defects on the surface of the WC powder can greatly improve surface free energy of the powder, which improves the sintering activity and reduces the sintering temperature of the WC powder.

Abstract: Tungsten Carbide (WC) hard coating is widely used to coat the surface of the steel tools which provide tribological properties. In this paper, 0.25 wt% & 0.35 wt% of Carbon Nanotubes (CNT) were mixed with tungsten carbide (WC) powders as the feedstock powders. Method of solution dispersion in ethanol media using an ultrasonic device was used for coating the surface of WC powders with CNT powder. The mixed powders were then used as the feedstock powder to coat onto the surface of tool steel using the flame spraying process. The coated surface microstructures were observed under a scanning electron microscope (SEM), x-ray diffraction (XRD), and the energy dispersive spectroscopy (EDS) was used for the phase characterization and identification. The wear rate of coated steels was determined using the Ogoshi machine, and the Vickers hardness method used to measure their microhardness. The effects of CNT on the microstructure of the coated material and the surface mechanical properties were investigated. The results showed that the mixture powder preparation using an ultrasonic method in SDS solution and the ball-milling process was suitable to disperse the CNT on the surface of WC feed powders due to produce an adequate relationship between CNT' and WC powders increasing the surface mechanical properties of coatings. The wear resistance of the coated material produce using the mixture of WC powder with 0.35 wt% CNT increased around 50% higher than the WC coated steel without CNT addition. Also, the hardness of coating reinforced CNT increased significantly compared with the hardness of WC coated and the steel substrates. Microhardness value from the base metal to the WC-CNT coated steel increased from 550 HV to 1717 HV and also the wear rate from the base metal to the WC-CNT coated steel decreased from 0.86 mm³/min to 0.017 mm³/min. These results indicate that CNT is an excellent alternative to improve the surface mechanical properties of WC coatings.

Abstract: s The paper considers the development of an alternative method for obtaining functional materials based on tungsten carbide and its compounds using simple and sufficiently productive equipment. This method will allow using mineral dumps as a raw material base, in addition, it gives an opportunity to obtain new compounds based on tungsten. Obtained during plasma-chemical synthesis, the W_xCW alloy from a mixture based on a tungsten-containing concentrate has a two-phase composition consisting of carbides of the W_xCW group and metallic tungsten. According to preliminary calculations, the content of the carbide phase in the alloy is 88% and depends on the plasma synthesis processes, on the concentrate composition, and on the introduced carburetor volume. The synthesis was carried out using tungsten-containing concentrates by treatment of high-density energies (g> 10⁴ - 10⁵ W/cm²) in an inert gas medium. The stage of plasma-chemical synthesis of the W_xCW semi-finished product made it possible to obtain nanosized tungsten carbide crystals. This makes a possibility to synthesize a high-quality alloy with an ordered structure of the carbide phase during refinement and pressing. The carbide phase ordered structure contributed to an increase in the strength characteristics of the new refractory material.

Abstract: This study addresses characterization of ED (electrode drying) effect on WC hardfacing welding microstructure. Medium carbon steel blade which used as CD (continuous digester) blade to mix up sulphuric acid together with ilmenite ore in a digester tank as a major part of production. Microstructure of WC hardfacing, elemental composition alongside hardness analyses are executed to investigate the effect of ED (electrode drying). The ED (electrode drying) effect on microstructure and hardness values of WC hardafcing coating are characterized by SEM (scanning electron microscope) analysis and micro-Vickers hardness tester correspondingly. Results revealed that ED (electrode drying) effect less significant in the larger carbides at overall coating zone. However, the absence of ED (electrode drying) led to distribution of uniform smaller carbide in non-carbide zone. The uniform carbide distribution increases the hardness of the WC hardfacing coating.

Abstract: Creating a gradient of properties in a single material is challenging for scientists and engineers. For this purpose, such methods are used as: welding of steels of different chemical compositions, joint rolling of steel sheets, sealing and surfacing of various kinds. All of these methods have a big disadvantage: under load, the material is destroyed in the weakest place - the place where the layers join. In this article, the authors proposed to obtain a gradient of properties in steel castings due to the introduction of dispersed particles of tungsten carbide into the crystallizing melt during centrifugal casting. The particles introduced serve as crystallization centers, accelerate the crystallization process and increase certain types of mechanical properties (hardness, microhardness, tensile strength). In addition, the particles of tungsten carbide have high hardness; therefore, in the structure of the workpieces they serve as reinforcing elements that strengthen the structure. The uneven distribution of particles in the preform being formed is possible for two reasons: tungsten carbide has a density greater than the melt, and besides, centrifugal force acts on them. The article describes the experiment and its results on the production of metal preforms with a gradient of properties. The introduced particles significantly influenced the macro-structure of the prepared castings. The article also presents the results of a study of the effect of particles on the hardness and micro-hardness of the resulting blanks.

Abstract: The article presents the results of research on obtaining powder of hard alloy using various methods. The analysis of studies described in the literature. Currently, there are many ways to obtain powders from waste, but most of them are poorly applicable in practice in a particular plant. On the basis of the data obtained from the literature, a method of obtaining powder was selected, which can be used in an enterprise with the equipment available. Technological regimes were also selected, which included such operations as softening the workpieces, mechanical grinding, grinding the powder in a ball mill, making press powder, molding, sintering, and tool making processes. The resulting blanks were further compared with a standard tool for cutting edge resistance and the presence of external and internal defects. The work carried out has shown the possibility of using technological regimes for the production of powders on existing equipment for the subsequent manufacture of cutting tools. This technology allows to reduce costs and product cost without significant loss in product quality, which makes it possible to compete with other manufacturers of carbide tools. In the future, it is planned to develop and optimize the existing technology to improve product quality. The paper presents the results of research of obtaining a hard alloy powder with a different methods. Comparison of products from different powders and the subsequent pressing rods, their sintering and examination of defects

Abstract: In this paper, we report on obtaining dense samples of composites in the WC/ZrO₂(Y₂O₃) system with a nanoscale microstructure by the SPS method. A complete assessment of their properties, including cutting properties, was carried out. Microstructural characterization of the final samples was conducted using SEM.

Abstract: Wire electrical discharge machine (WEDM) is non-conventional machining process. It can be used for hard cutting material. The study has been presented the combining WEDM with an ultrasonic machine (USM) with brass and tungsten were used as a wire electrode and workpiece respectively. The experiment was carried out with an ultrasonic transducer at 40, 80 kHz. The results were observed with the material removal rate (MRR) and surface roughness (Ra). This research introduced the method of USM setup and described the effected of vibration with the wire electrode on the displacement of amplitude. The result shows that the WEDM process with USM at 40 kHz can be more improved with the material removal rate and surface roughness than that of USM at 80 kHz. This can be explained that higher frequency affected to vibration displacement which makes lower amplitude.

Abstract: The effect of composite materials reinforcement by hardmetal with various size of particles (WC 710-1000 μm, recycled WC-Co 710-800 μm and pure WC 10 μm) with Fe-based matrix thermally affected by spark plasma sintering (SPS) method at temperatures 1100°C, 1200°C and 1280°C was studied. The analysis of samples cross-section was performed with SEM and EDS to illustrate distribution of elements after thermal influence. The aim of this research was an investigation of diffusion process behaviour between Fe-based matrix and WC and WC based hardmetal particles at various temperatures. Results help to identify and understand melting and solidification of grains affected at high temperature. Similar temperatures are used for surfacing and repair of worn parts and recycled tungsten carbide particles (as reinforcement) could be used during manual or plasma transferred arc welding.