Tungsten Carbide Spheres Research Articles

Development and research of methods for strengthening the blades of a straw spreader

Abstract In this article, a comprehensive analysis of existing materials, hardening methods, design and features of the work of parts in the composition of aggregates is carried out. Based on this analysis, the choice of material for the base and reinforcing coating was carried out, and the most effective ways of strengthening the blades of the straw spreader were determined, which are installed on combines instead of similar imported parts. In the course of the study, the spread of blanks and hardened parts by weight, the degree of wear of knives in real operation, as well as the chemical and phase composition, structure and properties of reinforcing coatings were studied. 65G steel is proposed as a modern import-substituting material, and 6HV2C steel is proposed as a promising one. To increase the hardness and wear resistance of the knife blade, the technology of induction surfacing of modified hard alloys (composites) using high-frequency transistor converters (inverters) with a programmable mode is proposed. This technique makes it possible to achieve a more uniform heat distribution and ensure high accuracy of temperature control during the surfacing process, which improves the mechanical properties of the coating. The use of boron carbide and spherical tungsten carbide as a wear resistance modifier makes it possible to increase the hardness of the coating to 62-67 HRC, suppress the growth of dendritic structures, increase the adhesion of the functional filler to the composite matrix, reduce dispersion and increase the microhardness of the carbide phase, which together increases the potential wear resistance of the coating. The use of induction surfacing of modified hard alloys on knife blades contributes to a significant increase in their service life by increasing resistance to mechanical damage and wear.

Synergistic improvement of pitting and wear resistance of laser powder bed fusion 420 stainless steel reinforced by size-controlled spherical cast tungsten carbides

The spherical cast WC/W2C is selected to produce a martensitic stainless steel-based composite using the laser powder bed fusion technique. W and C reacted with Fe and Cr, creating a strong bond between the particles and the matrix, reducing the wear rate by over 98 %. W and C diffuse to the matrix, increasing the hardness over 100 HV0.5. The interface between cast WC/W2C and matrix is sensitive to pitting corrosion through galvanic effects. However, the formation of austenite and WO3 from spherical cast WC/W2C decomposition improves the critical pitting potential and passive film stability.

Ultra-high strength metal matrix composites (MMCs) with extended ductility manufactured by size-controlled powder and spherical cast tungsten carbide

The main challenge of particle reinforced metal matrix composites (MMCs) is balancing strength and ductility. This research uses type 420 stainless steel and spherical cast tungsten carbide (WC/W2C) with a similar powder size and range as raw powders to manufacture laser powder bed fusion (LPBF) 420 + 5 wt% WC/W2C MMCs. LPBF 420 + 5 wt% WC/W2C MMCs contain austenite, martensite, and W-rich carbides (WC/W2C, FeW3C, M6C, and M7C3) from nanometre to micrometre scale. The well-balanced composition creates a crack-free reaction layer between the reinforced particles and matrix. This reaction layer consists of two distinct layers, depending on the element concentration. The LPBF 420 + 5 wt% WC/W2C MMCs achieved an excellent compressive strength of ∼5.5 GPa and a considerable fracture strain exceeding 50 %. The underlying mechanisms for the improved mechanical properties are discussed, providing further insight to advance the application of MMCs via additive manufacturing.

Optical Characterization of Materials for Precision Reference Spheres for Use with Structured Light Sensors.

Traditionally, 3D digitizing sensors have been based on contact measurement. Given the disadvantages of this type of measurement, non-contact sensors such as structured light sensors have gained the attention of many sectors in recent years. The fact that their metrological performance is affected by the optical properties of the digitized material, together with the lack of standards, makes it necessary to develop characterization work to validate materials and calibration artifacts for the qualification and calibration of these sensors. This work compares and optically characterizes different materials and surface finishes of reference spheres used in the calibration of two structured light sensors with different fields of application, with the aim to determine the most suitable sphere material-sensor combination in each case. The contact measurement system of a CMM is used as a reference and, for the processing of the information from the sensors, the application of two different filters is analyzed. The results achieved point to sandblasted stainless steel spheres as the best choice for calibrating or qualifying these sensors, as well as for use as registration targets in digitizing. Tungsten carbide spheres and zirconium are unsuitable for this purpose.

Photographic studies of the normal impact of hard spheres on fused silica generating hertzian cones

Colour high-speed photographic framing sequences of the normal impact of 2 mm diameter tungsten carbide spheres on a block of fused silica at 150 m s−1 were taken at 1 × 106 frames per second. The initiation and growth of the resulting two coaxial cone cracks, which formed within 0.1 µs of the initial projectile contact, were followed. The innermost cone crack of a semi included angle of 32° travelled at a velocity of (2270± 100) m s−1 which is close to the theoretical maximum crack velocity of 2180 m s−1 in fused silica. Importantly, the semi included angle of the cone crack was about a half of the angle of the cone crack produced by quasi-static loading. A suggested explanation, based on the localized decrease of the target's Poisson's ratio due to the high impact loading rate, has been proposed and examples are given which support this suggestion.

Enhanced piezoelectric energy harvesting based on sandwiched phononic crystal with embedded spheres

In recent years, metamaterial/ phononic crystal (PnC) based energy harvesters are gaining interest due to their excellent elastic wave manipulation and energy trapping capabilities. Here, we propose a novel PnC comprising of Tungsten Carbide (WC) spheres embedded in epoxy resin matrix. The sphere-epoxy composite is encapsulated by Aluminum (Al) holey structure and the device is sandwiched between two Al plates. Numerical analysis of band structure reveals a wide phononic band gap (BG) from 50.65 kHz to 71.12 kHz. These BGs can be engineered by varying geometric parameters of the unit cell viz., the radius of the sphere and thickness of Al plates. A point defect is introduced by removing the central sphere of the 5 × 5 PnC to facilitate the robust localization of evanescent wave defect modes within the bandgap. Moreover, it is observed that, by altering the radius of the defect sphere, the number of defect modes and their shift can be reconfigured. A PnC based energy harvester is implemented by attaching a piezoelectric disk (PZT-5H) onto the defect PnC just above the defect site. This arrangement of PZT disk converts the highly resonant mechanical defect mode into electrical energy, thereby allowing vibration energy harvesting. Finally, we show that the power enhancement can be achieved by ∼12 times with the proposed PnC compared to the bare Al block.

Self-healing of indentation damage in Ti2AlC MAX phase ceramics

Although the crack-healing capacity of Ti2AlC ceramics has been sufficiently studied, the ability of Ti2AlC to self-heal large-scale damage, such as foreign object damage (FOD), remains unknown. This paper investigates the self-healing ability of Ti2AlC ceramics with large-scale damage (∼1000 μm in diameter). Extensive healing was observed even in the plastic damage and radial cracks. The damage and cracks caused by indentations made using a tungsten carbide sphere were filled and covered with newly formed oxides, such as titanium oxide and alumina, by the oxidation of Ti2AlC after heat treatment in air at 1000 °C. The strength, hardness, toughness, and elastic modulus of the Ti2AlC samples were measured before and after healing. The results show that the mechanical properties of Ti2AlC were similar or even slightly higher after the damage had been healed. Thus, Ti2AlC ceramics are attractive healing agents for foreign object damage in high-temperature applications.

Longitudinal and transverse coherent waves in media containing randomly distributed spheres

Multiple scattering effects due to a random distribution of identical spheres are investigated in the general case of elastic or poroelastic host media, where both longitudinal and transverse waves may co-exist. Propagation of plane coherent waves is assumed, and their dispersion equation looked for, as well as analytic approximations of those particular solutions that are close to the wavenumbers in the free host, when the product of the concentration with the scattering cross section of the spheres is low. Under this last condition, pair-correlation effects are seen to be of second order. Numerical studies are performed under the hole correction assumption, and compared to experimental data for tungsten carbide spheres in an epoxy matrix, which is a rather illustrative situation of how longitudinal and transverse waves participate to coherent propagation.

STRUCTURES OF GRADIENT LAYERS OBTAINED USING THE LASER METAL DEPOSITION (LMD) METHOD

The paper presents the results of structural investigations of a laser-welded layer in the Inconel 625 and Stellite 6 alloy matrix with the addition of WC. The tests involved the use of on plates made of low-alloy steel S355J2C+N. The filler materials used in the tests were nickel-based (Inconel 625) or co-balt-based powders (Stellite 6) having various contents (0-25%) of spherical tung-sten carbide (WC) used as the reinforcing phase. The granularity of the powders was re-stricted within the range of 45 µm to 90 µm. The cladding tests involved making multi-layer overlay welds. Next, non-destructive (VT and PT) and destructive (macro, hardness) tests were carried out. The macroscopic metallographic tests revealed that the three-layer Inconel 625-based overlay welds (with a WC content of up to 15%) had the correct shape and were characterized by full fusion into the base material, ensuring the continuity of the overlay weld.In the case of the Stellite 6-based overlay welds containing 10% of WC, it was possible to observe a through-crack of the overlay welds. The crack was formed in the first layer (as a result of stresses during the solidification of the liquid metal) and developed during the deposition of subsequent layers. The macrostructural tests were supplemented with microstructural observations and microanalysis of the chemical composition (EDS). The above-named tests revealed the good stirring of alloying elements in the overlay weld, indicating the high homogeneity of the overlay weld.The hardness obtained on the surface of the padding weld was 600 HV1.

Low plasticity burnishing surface treatment: impact on surface integrity parameters of turned cylindrical Ti- 6Al-4V specimen

ABSTRACT Surface integrity parameters are the major aspect in the extension of the fatigue life of aero- engine components. In this study, a modified burnishing surface treatment (low plasticity burnishing) with reduced cold work was proposed to improve surface integrity characteristics such as surface finish and hardness, and to induce stable, advantageous compressive residual stress in a cylindrical Ti-6Al-4 V specimen (as-received). In this process, a rolling rigid spherical tungsten carbide ball is pressed across a Ti-6Al-4 V specimen at an appropriate fluid pressure generated by the hydraulic unit. The low plasticity ball burnishing tooling system supported by a hydraulic unit of capacity 30 MPa is designed and developed in this study. By using a suitable specimen holding fixture, the ball burnishing with a small amount of plastic strain was carried out on the Ti-6Al-4 V cylindrical specimen. This research examined the effect of burnishing process variables namely tool pass and burnishing fluid pressure on compressive residual stresses, surface roughness, and hardness in Ti-6Al-4 V. The explicit dynamic analysis was carried out by using FE-Analysis software ABAQUS 6.17 as a part of numerical simulation. Hydraulic burnishing pressure and burnishing passes are the most influential parameters in generating favourable compressive residual stress, qualitative surface finish with less cold work in Ti-6Al-4 V turned specimen.

Effect of Spherical Tungsten Carbide Load to the Corrosion Behaviour of Plasma Transfer Arc Hard Facing in Acidic and Alkaline Environment

Plasma transfer arc welding (PTAW) has been one of the popular methods for depositing thick hard facing. In this study, this method was used to lay the nickel hard-facing without tungsten carbide and with different compositions which are 35 wt%, 50 wt% and 60 wt% carbides. The hard facing was characterised using a scanning electron microscope with EDS and x-ray diffractometer (XRD). The corrosion behaviour was evaluated using three electrodes electrochemical test with saturated calmonel electrode (SCE) and platinum plate as the reference electrode and counter electrode respectively. The corrosion test shows that the hard facing had higher corrosion resistance in an alkaline environment compared to an acidic environment. The corrosion mechanism was by the dissolution of the nickel matrix, Ni3B dissolution is seen in an acidic environment while in alkaline electrolyte, the dendritic nickel dissolves preferentially.

Effect of Tungsten Carbide Morphology, Quantity, and Microstructure on Wear of a Hardfacing Layer Manufactured by Plasma Transferred Arc Welding

Hardfacing layers on mild steel substrates were successfully manufactured using a plasma transferred arc welding (PTAW) process to combine tungsten carbide powder and binder metal. Three morphological types of tungsten carbide powder were employed: spherical, fused angular, and mixed powder. The effects of both the morphology and the quantity of tungsten carbide powder on the wear property of the products were determined using a dry sand wheel abrasion test. The results revealed that two conditions effectively increased the wear resistance of the hardfacing layers: the use of spherical tungsten carbide and the use of an increased quantity of tungsten carbide. Moreover, the formation of an interfacial layer of intermetallic compounds (IMCs) between the tungsten carbide and binder metal, and the relationship between the microstructure of the IMC layer and its wear property were also investigated. It was confirmed that, in general, preferential wear occurs in the binder metal region. It was also unveiled that the wear property improves when interfacial IMC bands are formed and grown to appropriate width. To obtain a sound layer more resistant to wear, the PTAW conditions should be adequately controlled. In particular, these include the process peak temperature and the cooling rate, which affect the formation of the microstructure.

Research on suppressing brittle fracture and implementing ductile mode cutting for improving surface quality at silicon wafers manufacturing

Single crystal silicon is an important basic material used to manufacture electronic and photovoltaic devices. Ductile mode of diamond wire sawing is a promising method for silicon wafering in order to produce wafers with minimal surface damage. To achieve ductile mode, the correct applying of cutting parameters and careful wire design is necessary. This study investigates the scratching of monocrystalline silicon by the abrasive particles of different geometry, which simulates the material removal process in diamond wire sawing. Diamonds, crushed and spherical tungsten carbide (WC) particles served as abrasives. Experiments show that spherical abrasives enhance ductile mode cutting significantly decreasing brittle damage when compared to irregular shape particles. Spherical WC particles permit to increase the critical load and critical cut depth of ductile-to-brittle transition from 5 to 10 times. The depth of the damaged subsurface layer decreased from 5 µm to 0.2 µm due to the absence of brittle cracks. A uniform regular distribution and appropriate suitable density of abrasive particles is obligatory for cracking reduction. For that, the method of diamond particles uniform deposition with the controlled density by a polymer binder combining high modulus and adhesive capacity with good flexibility was elaborated. The method includes preliminary diamond particles fixation on a thin resin layer providing high uniformity and subsequent strong fixation by a thicker resin layer. The research on ovalization of diamond particles was performed for smoothening cutting edges. The method is based on the activation of the graphitization process at sharp edges of particles under the action of metal salts at increased temperatures.

Microstructure and mechanical properties of WC reinforced 18Ni300 composites produced by selective laser melting

Spherical Tungsten Carbide (WC) powders were chosen as reinforcements to produce 18Ni300 steel matrix composites by selective laser melting (SLM). The microstructures and tensile properties of the composites were observed and analyzed. The results manifest that the addition of spherical WC powders significantly affects the microstructure and properties of 18Ni300. With the addition of WC, the austenite (γ-Fe) phase and WC1-X appear, and the grain morphology and orientation change. Moreover, an obvious interface layer (about 1 μm in thickness) is formed due to partial dissolution of WC particles and diffusion of W and C. With increasing WC fraction, the α-Fe in the matrix decreases, and γ-Fe, W2C and WC1-X increase. The spherical WC powders are broken into many small irregular powders distributed in the matrix. The macro-cracks generate when WC content is more than 25%. The hardness, Young's modulus and tensile strength of the composites first decrease and then increase with an increase of WC contents ranging from 0% to 20%, while the relative density exhibits the opposite change rules. The elongation at break first increases and then gradually decreases with increasing WC contents. The composite specimens generally exhibit brittle fracture characterization, different from the plastic fracture characterization of the 18Ni300 matrix. Many cracks generate around the WC and in the matrix. The cracks, tearing ridges and cleavage steps, pits and small irregular WC powders gradually increase with increasing WC contents.

Evolution of sub-surface microstructure under linear reciprocating wear of nanostructured bainitic steel

Nanostructured bainitic steels have high strength as well as a combination of significant ductility, fracture toughness and sub-critical fatigue crack growth life. Hence, they can be potentially useful in structures suffering rolling and/or sliding fatigue e.g. rails, mining components, bearings and shafts. However, such applications require high wear resistance which is not solely dependent on the initial strength since repetitive sliding often leads to sub-surface microstructural evolution that alters the tribological response with time. In the current study, three nanostructured bainitic blocks with lath thickness of 45, 54 and 77 nm have been made from steel of composition: Fe-0.86C-1.45Si-1.8Mn-0.47Al-1.88Co-0.23Mo (wt%) by austempering at 250, 300 and 350 °C respectively. We have investigated the friction and microstructural evolution under reciprocating sliding motion of a 10 mm spherical tungsten carbide indenter at 10 kN load and correlated the findings with the initial morphology of bainite. All specimens exhibited hardening after multiple cycles of deformation. However, the steel austempered at the lowest temperature showed the highest sub-surface hardness and lowest friction coefficient and was the most resistant to wear when tested under sliding fatigue for up to 500 cycles. Repeated sliding resulted in formation of two kinds of layers: white etching layer (WEL) and severely deformed layer (SDL). WEL exhibited very fine microstructure whereas the SDL showed alignment of retained austenite and bainitic laths along the direction of highest shear stress. There was a predominant presence of WEL in the specimens austempered at the lowest temperature and SDL in the specimens transformed at the highest temperature. Atomic probe tomography (APT) was used to investigate the distribution of carbon in the deformed layers just below the wear track after 500 sliding cycles for 250 and 350 °C austempered condition. No significant change in carbon has been detected in any of the austempered specimens after wear.

Microstructure and wear of Ni-WC hardfacing used for steel-body PDC bits

Superior hardfacing materials, such as Ni-WC blends, are commonly applied to rock-engaging regions of oil & gas drill bits and other downhole tools to provide sufficient wear protection. In this work, it was found that drill bits were subjected to severe high-stress abrasive wear while rubbing against rock formations. The wear behavior of drill bits could be appropriately evaluated by the wear test in accordance with ASTM standard B611 rather than ASTM standard G65. This work also found that the toughness of tungsten carbides was a predominant factor determining high-stress abrasion resistance of Ni-WC hardfacing. Any choices from various types, sizes, and shapes of tungsten carbides would contribute to the improvements of wear resistance as long as this choice delivered better toughness, such as cemented tungsten carbide and spherical tungsten carbide. Large particle size was also beneficial for reinforcing wear resistance, but played a secondary role as compared to carbide toughness. Therefore, large-sized cemented tungsten carbide pellets provided the best high-stress abrasion resistance for drill bits, with large-sized spherical tungsten carbide being a close second. In addition, the comprehensive hardness of Ni-WC composite could be well represented using a linearly additive approach. The calculated hardness established a strong positive correlation with the wear behavior of Ni-WC hardfacing.

Revealing tribo–oxidation mechanisms of the copper–WC system under high tribological loading

The near-surface structural and chemical changes were investigated for pure copper against a tungsten carbide (WC) sphere during high tribological loading. Fundamental stages are identified in the Cu-WC tribo-system: (i) high tribological stress promotes grain refinement to the ultra-fine grains regime in the very beginning; (ii) nucleation of extremely fine (~3 nm) oxygen–enriched Cu nano particles in the near-surface layer and subsequent growth of the Cu2O oxide; (iii) formation of continuous nanostructured mixing layer with heterogeneous Cu and O distribution in the late stage. Near-surface mechanical mixing is presumably the main contribution to chemical modifications under high tribological loading. Our findings shed atomic-insights into intricate tribochemical modifications, one of the most intriguing phenomena in material-oriented tribology.

Effects of spherical WC powders on the erosion behavior of WC-Ni hardfacing used for steel body drill bit

Improving the erosion resistance of polycrystalline diamond compact (PDC) bit can prolong its service life. The influence of spherical WC powders on the erosion behavior of WC-Ni hardfacing used for steel body drill bit has not been reported. In this work, Ni-based hardfacing coatings reinforced with various content of spherical cast tungsten carbide (CTCS) and angular cast tungsten carbide (CTC-A) particles are fabricated by oxy-acetylene welding process. The erosion behavior of WC-Ni hardfacing used for steel body PDC drill bit is experimentally studied. Results show that, the coating's microstructure, microhardness, fracture toughness and corrosion resistance varies under different CTC-S content, which leads to the differences in erosion mechanisms. The erosion resistance of hardfacing coatings decreases first and then increases with the decrease in CTC-S content. Sample 1 with 60% CTC-S and 0% CTC-A has the best erosion resistance, while sample 3 with 30% CTC-S and 30% CTC-A has the worst erosion resistance. As CTC-S content decreases, the erosion wear mechanism of hardfacing coating transforms from brittle mechanism to ductile mechanism. At a high CTC-S content, hardfacing coatings present brittle erosion wear mechanisms, such as micro-fracture and precipitate removal. At a low CTC-S content, hardfacing coatings show ductile erosion wear mechanisms, such as plastic deformation and crater formation.

Modification of wear-resistant coatings of the Fe-Cr-C system with spherical tungsten carbide WC-W2C

The article describes the production procedure, studies the structure, and determines the properties of new wear-resistant coatings of the Fe-Cr-C system intended for hardening the working bodies of agricultural machines. To increase the wear resistance and give new consumer qualities to such coatings, they were modified with spherical tungsten carbide WC-W2C -spherorelite.It is shown that the introduction of the complex (WC-W2C+B4C) into the basic charge allows increasing the hardness of the deposited to 1000 … 1200 HV100, and wear resistance by 3.1 times in relation to the base material, and by 1.3 … 1.8 times in relation to the base (not hardened) material.

The formation features of the surface composite layer by laser-powder injection of tungsten monocarbide particles into a matrix from carbon steel

ABSTRACT The possibility of application of laser carbon steel for railway transport wheels manufacturing surface alloying with spherical tungsten carbides WC was considered. Experiments showed that volume part of reinforcing particles could reach 58% when laser powder alloying is applied. In the same time, if volume par of WC exceeds 16%, cracks on the surface are observed.