WC Powder Research Articles

Nano tungsten carbide interactions and mechanical behaviour during sintering: A molecular dynamics study

In the present research paper, atomistic simulation at microscopic level has been performed for sintering of nanocrsytalline tungsten carbide particles. The sintering parameters like dihedral angle, neck width, and shrinkage ratio have been evaluated during sintering. The Radial Distribution Function (RDF) and Mean Square Displacement (MSD) for atoms have been simulated in order to understand the crystal structure properties and diffusion behaviour of the atoms. The solid state sintering (heating in range of0.6-0.8Tm) has been performed at two different heating rates i.e. 2.5 K/ps and 4.63 K/ps for various size of particles i.e. (2 – 8 nm). The sintering behaviour for 4 nm size particle has been analysed. It has been found that neck width in case of slower heating rate is 33 Å, which is more than the higher heating rate. Besides this, the maximum dihedral angle of 1120 has been found during sintering which lies in the range of solid state sintering of the nano scale powders. The diffusivity coefficient calculated during various sintering rate has been found to be 5.25×10-14m2/s and 1.05×10-13m2/s. In order to check the tensile properties of sintered particle, uniaxial tensile test simulations have been performed at strain rate of 1010 s−1. The maximum strength of 4235 MPa and 3690 MPa has been achieved by slow and fast heating rate sintered particles respectively. The tensile strength variation with respect to temperature has also been studied during the sintering process. This Molecular Dynamic (MD) study in turn has laid the platform for setting of the optimum parameters during sintering of WC powders at nano scale level.

Toward Greener Synthesis of WC Powders for Cemented Tungsten Carbides Manufacturing

Tungsten carbide (WC) is the most important tungsten compound, and the main component of WC-Co cermet composites. WC-Co are widely used engineering materials due to the combination of high hardness and strength of tungsten carbide with the toughness and plasticity of the metallic binder. The direct synthesis of WC from tungsten concentrate containing ∼70% WO3 has been achieved by carbothermic reduction. Mineral/carbon black mixtures were prepared by planetary ball milling and subjected to annealing at 1150 °C in flowing Ar. Specific leaching treatments have been developed to remove foreign phases and obtain pure WC powders. This new process allows about 50% energy saving, −34% CO2 emissions, and significantly lower amounts of industrial waste, with respect to the classical hydrometallurgical tungsten extraction and subsequent pyrometallurgical WC synthesis, widely used in tungsten industry. WC powders obtained by carbothermic reduction of the mineral were employed to prepare sintered WC-8 wt %Co samples that showed high density (>99%), hardness (1490 HV), and toughness (14.6 MPa·m1/2). These findings demonstrate, for the first time, that the carbothermic reduction of tungsten concentrates does represent a viable process for energy efficient and sustainable synthesis of WC powders to be used in the production of cemented carbides.

Effect of WC content on microstructure, hardness, and wear properties of plasma cladded Fe–Cr–C–WC coating

The Q235 sample was coated with ball-milled Fe–Cr–C–WC powder using plasma cladding technology, and the influence of tungsten carbide (WC) content on the surface microstructure, hardness, and wear properties of the coated steel was evaluated. The single factor test of optimal WC content was carried out on DML-02BD plasma cladding machine, and the material after cladding was analyzed. The microstructure distribution, elemental composition and phase composition of the coating were observed by MIRA3-XMH scanning electron microscopy. The microhardness of cladding layer can indirectly reflect the properties of cladding layer to a certain extent, which is measured by the Vickers microhardness tester. The wear quality, friction coefficient and wear mark morphology can directly reflect the wear resistance of the test blocks. These are observed by the ring block friction and wear tester and the ultra depth of field microscope, respectively. With an increasing WC content, the microhardness of the cladding layer shows an upward trend. The main hard phases of the cladding layer after adding WC are (Cr, Fe)7C3, (Fe, Ni)23C7, and the other phases are γ-Fe, Fe3W3C, WCandFe2W. After 6 h friction and wear test, the cladding layer with 30%WC showed the best wear resistance. The total wear amount, wear volume, wear rate and friction coefficient were 0.01 g, 4.22 mm3, 2.344 × 10–4 mm3/(N·m), and 0.35, which were 1/10, 1/5, 1/5, and 7/10 of those without WC cladding layer, respectively. It can be concluded that different WC contents affect the surface microstructure and properties of Fe–Cr–C alloy coating treated by plasma cladding technology. At a WC content of 30%, the microstructure and properties of the cladding layer reach the best.

Experimental investigation and parametric optimization for minimization of dilution during direct laser metal deposition of tungsten carbide and cobalt powder mixture on SS304 substrate

Optimization of process parameters for direct laser metal deposition of WC (88 wt%) and Co (12 wt%) mixed powder on SS304 substrate was carried out to obtain minimum dilution. The effect of process parameters on clad geometric elements was expressed through polynomial relations. A mathematical expression for dilution was developed in terms of clad geometric elements and then verified with experimentally obtained dilution. The regression analysis for each geometric element and dilution was also studied. To obtain an optimized set of process parameters four recently developed optimization algorithms were used, which was then followed by a confirmation test. Bonobo Optimizer algorithm was fast during the search for the globally optimum solution. A detailed macroscopic, microstructural, thermo-cycle and XRD analysis for the confirmed optimized run was carried out along with the comparison study. The hardness behaviour of clad tracks was also studied by comparing it with that of the substrate.

Microstructure and properties of Ta-reinforced NiCuBSi + WC composite coating deposited on 5Cr5MoSiV1 steel substrate by laser cladding

Mixtures of Ni-based self-fluxing alloy + WC powders are widely used to prepare wear-resistant coatings on workpiece surfaces, and the particle size and distribution of the WC reinforcing phase affect the wear resistance and uniformity of the coatings. Here, to improve the wear resistance of the shield machine cutter ring, Ta was used as the reinforcing phase for the NiCuBSi + WC composite powders for the first time, and the wear-resistant coatings were prepared on the surface of 5Cr5MoSiV1 steel by laser cladding. The effect of Ta addition on the structure and properties of the coating was investigated, and the mechanism of Ta modification was analyzed. The results show that a good metallurgical bonding is formed between the steel substrate and the coating. Without the addition of Ta, the main reinforcing phases in the coating are large spherical WC particles and small flocculated WC and W2C particles, and the binding phase is Ni-Cu. The distribution of spherical WC large particles in the coating is not uniform, and there are Ni-based columnar crystal regions without the reinforcing phase. The addition of Ta consumed some of the spherical WC particles in the coating and took away some of the C of the WC particles to synthesize TaC in-situ, generating long rod-shaped W2C particles and embedding them in the coating, improving the uniformity of the hardness distribution of the coating. The wear resistance of the coating is 2.3 times higher than that without the addition of Ta, which is expected to improve the wear resistance of the cutter ring of the shielding tunneling machine.

Erosion behavior of laser cladded Colmonoy-6 + 50%WC on SS410 steel under accelerated slurry erosion testing

Erosion due to slurry has an indispensable effect on the lifespan and operating efficiency of hydro machine components. To mitigate this effect, laser cladding may prove as a cost-effective choice to improve the surface properties of various hydro machine components. In this research work, a laser cladding of Colmonoy-6 + 50%WC powder on the surface of SS410 steel was deposited using high-power diode laser at optimized levels of operating parameters. The deposited coating was characterized with regard to different mechanical and metallurgical properties. The effect of various factors such as slurry concentration, erodent particle size, impact velocity, and impact angle on slurry erosion behavior of uncoated and laser cladded substrate was analyzed. The Colmonoy-6 + 50%WC cladded specimens exhibited significantly better slurry erosion resistance in comparison with uncoated SS410 steel specimens under all slurry erosion conditions. Impact velocity was observed to be a maximum contributor to slurry erosion, followed by impact angle, average particle size and slurry concentration. The SEM micrographs of eroded cladded surfaces showed signatures of lip formation & fracture sites, micro-cutting, ploughing, and wear marks at a shallow impact angle in Colmonoy-6 pool, however, for normal impact, the existence of cracks in WC particles were observed.

A novel processing method based on the 3-spot diode laser source for the laser cladding of stainless-steel ball valves

In this paper, aiming to solve the problem of cracks in the laser cladding for stainless-steel ball valves, a novel method for defect-free processing is introduced. To realize this method, a 3-spot high-power diode laser source is developed. These three spots are respectively used for dynamic local preheating, laser cladding processing and dynamic local tempering. Using this high-power diode laser, a cladding processing of the stainless-steel ball valve with Ni60 + WC powder is successfully completed. Compared with the traditional processing approach, the cladded sample is free from any defects such as cracks and pores, which demonstrates the processing effect of this approach. This work provides a new method for the laser cladding of stainless-steel ball valves.

Progress of Spark Plasma Sintering (SPS) Method, Systems, Ceramics Applications and Industrialization

The spark plasma sintering (SPS) method is of great interest to the powder and powder metallurgy industry and material researchers of academia for both product manufacturing and advanced material research and development. Today in Japan, a number of SPS products for different industries have already been realized. Today’s fifth-generation SPS systems are capable of producing parts of increasing size, offering improved functionality, reproducibility, productivity, and cost. For instance, pure nano-Tungsten Carbide WC powder (no additives) is fully densified with a nano-grain-sized structure for glass lens application in the optics industry. The SPS is now moving from scientific academia and/or R&D proto-type materials level usage to practical industry use product stage utilizing in the field of electronics, automotive, mold and die, cutting tools, fine ceramics, clean energy, biomaterials industries, and others. This paper reviews and introduces the peculiar phenomenon of SPS and the progress of SPS technology, method, development of SPS systems, and its industrial product applications.

A comparative study of tungsten carbide and carbon nanotubes reinforced Inconel 625 composite coatings fabricated by laser cladding

Laser cladding with wire presents clear advantages in economic efficiency and cleanliness over the powder-based system. To find the best coating performance, the Inconel 625 composite coating, and two typical metal matrix composite (MMC) coatings reinforced respectively by tungsten carbide (WC) and carbon nanotubes (CNTs) were fabricated by an off-axis wire cladding system. The differences of morphology, microstructure and mechanical properties among the three samples were investigated. The results showed that the morphology of clad coatings with reinforcement powder generally presented desirable geometric characteristics. The clad coating with WC powder, in particular, presented better wettability compared with the other samples. The main secondary compound of WC dissolution was W2C, which was mainly distributed at grain boundaries. The mechanical properties of powder reinforced MMC coatings were significantly improved. Compared with the Inconel 625 specimen in coating area, the yield strength of the two MMC coatings was improved by 36.3% and 23.4% respectively. In addition, the average microhardness of WC/Inconel 625 coating showed an obvious increase to 589 HV.

The enhancement of the microstructure and mechanical performances of ultrafine WC-Co cemented carbides by optimizing Cr2(C,N) addition and WC particle sizes

Ultrafine WC-10Co cemented carbides with different Cr2(C,N) inhibitor contents and different-scaled WC powders were prepared by low-pressure sintering. Their influence on the microstructure and mechanical performances were investigated and expounded in this work. The result shows that the Cr2(C,N) addition homogenized the microstructure of the cemented carbides and refined WC grains. With the Cr2(C,N) addition increasing, hardness increased to 1870 kg/mm2, transverse rupture strength (TRS) first increased to 4435 MPa and then sharply decreased to 3230 MPa due to the existence of more pores with excessive Cr2(C,N). With the reduction of WC particle size, the mean WC grain size and mean free path of Co phase decreased, while the contiguity of the WC grains increased. The hardness and TRS of the specimens reduced, while fracture toughness increased. The comprehensive mechanical properties namely the TRS, hardness, and fracture toughness in the cemented carbides with 0.5 wt% Cr2(C,N) and 0.4 μm WC powder, were 4748 MPa, 1786 kg/mm2, 10.1 MPa· m1/2, respectively. A good combination of high TRS and hardness could be obtained in the cemented carbides by adopting appropriate amount of Cr2(C,N) and reducing the WC particle size.

Effect of Fe prealloyed powder and the sintering process on the matrix properties of impregnated diamond bits

Prealloyed Cr–Fe and prealloyed Fe powders were used as a replacement for widely used tungsten carbide powder to fabricate impregnated diamond bits. The effects of the prealloyed Fe content and sintering process on the matrix properties of the impregnated diamond bits wereinvestigated. The relative density, bending strength, and hardness were tested, and the fracture was analyzed by scanning electron microscopy. The results showedthat as the mass fraction of prealloyed Fe powder increased, the density and bending strength of the matrix decreased, and the hardness increased. The mechanical properties of the matrix increased with increasing sintering temperature; when the temperature was higher than 940 °C, the mechanical propertiestended to stabilize or decrease slightly. When the holding time was 5 min, the relative density, bending strength, and hardness of the matrix material were high. The experimental data showedthat a proper amount of prealloyed Fe can yieldgood mechanical properties, and that prealloyed Cr–Fe and prealloyed Fe can completely replace WC (tungsten carbide) as the framework material of thematrix. In conclusion, it is feasible and reasonable to replace WC powder with prealloyed Fe powder to prepare impregnated diamond bits. This process has significant economic benefits and market prospects.

Study on influencing factors and mechanism of high-quality tungsten carbide nanopowders synthesized via carbothermal reduction

In this study, high-quality WC powders with 100 nm were synthesized using a simple and efficient carbothermal reduction method. The effects of carbon source and temperature on the synthesis process, nucleation and growth mechanism of WC nanopowders were investigated in detailed. The results show that acetylene black with small particle size and good dispersion is the optimal carbon source to prepare WC nanopowders. The uniform precursor synthesized by acetylene black can significantly increase the contact probability of WO3 and C particles, greatly reduce the activation energy, and effectively improve the reaction efficiency during subsequent carbothermal reduction process. Moreover, the formation temperatures of WC are reduced to 1000 °C compared with other three carbon source. Further increasing carbothermal reduction temperature can provide the driving force of diffusing atoms, which promotes the carbothermal reduction reaction, but also significantly increases the diffusion rate of grain boundary resulting in rapid grain growth.

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.

Effects of Powder Microscopic Defects on Densification and Mechanical Properties of WC via Spark Plasma Sintering

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.m1/2) 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.

Preparation and characterization of Cr-doped tungsten oxide by liquid-liquid doping precursor

The tungsten oxides with uniformly grain growth inhibitor elements can significantly improve the distribution of inhibitors in the subsequent WC powders, and finally enhanced the properties of ultra-fine grained cemented carbides. Thus, a new liquid-liquid doping method was used to prepare the tungsten oxide composite powders with grain growth inhibitor elements by spray drying-calcining process. The microstructure and phase transition of Cr-doped and undoped tungsten oxide composite powders were studied by TG/DSC, XRD, SEM, and XPS. The results showed that Cr doping has little effect on the morphology of the precursor powders after spray drying. However, the existence of ammonium chromate had a significant effect on the properties of the calcined tungsten oxide. The volume expansion of ammonium chromate could reduce the decomposition temperature of ammonium tungstate precursor powders. Additionally, the formation of thermodynamic instability Cr-O-W compound could be the reason for the exothermic peak appeared at 486.3 °C. Moreover, the ‘liquid-liquid’ doping method guaranteed the uniform distribution of Cr2O3, which was favourable for the stable existence of hexagonal metastable h-WO3. The tungsten oxide powders calcined at 600 °C have a flaky morphology due to the uniform distribution of Cr2O3, and the uniform distribution of Cr2O3 in the powder can also prevent the grain growth of WO3.

Multi-objective optimization of coating properties and cladding efficiency in 316L/WC composite laser cladding based on grey relational analysis

This study aims at improving the coating properties and cladding efficiency in composite material laser cladding. Using Taguchi orthogonal experimental design, the correlation between processing parameters and index of cladding quality had been investigated. By altering the input of laser power, scanning speed, gas flow, and tungsten carbide powder ratio in laser cladding setup, their influence on the micro-hardness and wear resistance of the clad as well as the cladding efficiency had been studied. This study achieved processing parameter optimization with grey relational analysis by combining multiple objectives. Results showed that the micro-hardness and wear resistance of the clad were significantly affected by the WC powder ratio in the composite. Also, the laser power denoted a significant impact on the cladding efficiency. To obtain the clad with maximum micro-hardness and minimum wear volume while also attaining the maximum cladding efficiency, grey relational analysis was utilized to combine these multiple objectives in optimization. The processing parameter set obtained from optimization met the targets and showed a small-scale error rate of 4.92% in the grey relational grade prediction. This study verified the applicability and provided the theoretical basis for multiple-objective optimization of the coating properties and cladding efficiency in composite laser cladding.

Электроискровое нанесение порошка карбида вольфрама на титановый сплав Ti6Al4V

Titanium alloys are attracting the attention of researchers and engineers because of their unique combination of high specific strength, corrosion resistance and biocompatibility, but they are characterized by high wear. Therefore, the study of new methods for making protective coatings on titanium alloys is relevant. A mixture of titanium granules with tungsten carbide powder was used to prepare coatings on the titanium alloy Ti6Al4V by the method of electrospark granules deposition. Three mixtures of granules with a tungsten carbide content of 2.1, 4.1 and 6.0 vol.% were prepared. According to the data of X-ray analysis, it was found that the following phases were observed in the composition of the coatings: WC, W2C, W, αTi and β-(W, Ti)C1−x. Carbides W2C, (W, Ti)C1−x and metallic tungsten were formed as a result of the decarburization of WC upon its interaction with molten titanium under the conditions of an electric discharge. Large inclusions of tungsten carbide surrounded by a metallic Ti-W-C binder were observed in the microstructure of the coatings. According to the data of energy dispersive analysis, the concentrations of tungsten and carbon decreased when scanning from the surface layers of the coating to the substrate. The average values of the microhardness of the coatings increased from 7.9 to 9.2 GPa with an increase in the concentration of WC powder in the mixture of granules. The average values of the friction coefficients of the coatings were in the range of 0.33 – 0.48, which is 35 ± 3 % lower than that of the Ti6Al4V alloy. Tests for wear in the dry friction mode at loads of 25 and 70 N showed that the wear rate of the coatings ranged from 0.38 ×10−5 to 1.68 ×10−5 mm3 / Nm. The best wear resistance under both loads was demonstrated by the coatings deposited with the addition of 4.1 vol.% WC, which make it possible to increase the wear resistance of the Ti6Al4V alloy up to 18 times. Thus, the prospect of electrospark deposition of cermet coatings with enhanced mechanical properties on a titanium alloy using tungsten carbide powder mixed with titanium granules is shown.

WC modified with ionic liquids for the hydrogen evolution reaction in alkaline solution

A source of high-purity hydrogen is essential to overcome the problem of using fossil fuel consumption to obtain primary energy. Electrolysis of water arises as an important alternative to fulfil this necessity since it can be coupled to renewable sources and generates pure hydrogen. For this technology, low-temperature devices need new non-noble electrocatalyst materials that reduce its cost and perform with an acceptable activity and durability. In this sense, we present here the preparation and performance towards the hydrogen evolution reaction (HER) of several composite materials generated from hexagonal WC powder and different pyridinium-based ionic liquids. Differential electrochemical mass spectrometry (DEMS) is used to obtain not only an accurate measurement of the activity but also reliable information about kinetics and mechanism of HER on the surface of the studied materials in basic medium. Finally, it is proved that the presence of ionic liquids play an important role in the particle size distribution of the generated composite material and, therefore, in their capacitance, durability and catalytic activity.

Strengthening mechanism and high-temperature properties of H13 + WC/Y2O3 laser-cladding coatings

In order to meet the surface modification and repair requirements of 8407 hot extrusion die, Y2O3 powder and WC powder were added as strengthening phases into an H13 powder. The coatings were strengthened through laser-cladding and then applied on the surface of 8407 steel. XRD, SEM, EDS, and Vickers high-temperature hardness tests were used to analyze the properties of the laser-cladding coating, such as its phase composition, microstructure, high-temperature hardness, and high-temperature stability. The M7C3 composite strengthening phase was evenly distributed throughout the entire coating in a three-dimensional reticular shape, resulting in a uniform hardness distribution. The addition of Y2O3 accelerated the decomposition of WC particles, which increased the uniformity of the laser-cladding coating. The hardness of the laser-cladding coating at room temperature was 818.7 HV, which was 48.4% higher than that of the substrate, and its hardness at 500 °C was 555.6 HV, which was 32.3% higher than that of the substrate. The hardness values of the laser-cladding coatings at different holding times were roughly the same as 8407 steel. After holding for a certain time at different high temperatures, the hardness of the laser-cladding coatings was double that of 8407 steel.

Effects of carbide substrate properties and diamond coating morphology on drilling performance of CFRP composite

Abstract The properties of a cemented carbide tool substrate and diamond coating were studied for the precision drilling of carbon fiber-reinforced plastic (CFRP). The microstructures and mechanical properties of WC–6 wt.% Co substrates using different WC particle sizes were examined to determine correlations between the mechanical properties and the drilling performance. The results demonstrated that WC powders with an average particle size of 2.3 μm were suitable drill substrates. Coatings of either microcrystalline diamond (MCD) or gradient nanocrystalline diamond (NCD) were deposited using hot-filament chemical vapor deposition. A drilling test using T700-grade CFRP was conducted to evaluate the drilling performance, tool wear resistance, and CFRP hole quality achieved based on the diamond coating morphology. In the CFRP drilling tests, the diamond-coated drills showed superior tool lifetimes four times longer than that of the uncoated drill. The MCD-coated drill exhibited good wear resistance compared to the gradient NCD-coated drill; however, the gradient NCD-coated drill demonstrated better machining quality in terms of the delamination factor, surface roughness inside the machined hole, and accuracy of the machining dimensions. In this study, we aimed to develop the optimal tool substrate for the drilling of general-purpose CFRP and proposed directions for the development of diamond coatings to maximize drilling performance.