WC Powder Research Articles

Efficient separation and recovery of cobalt from grinding waste of cemented carbide using a sulfuric acid-sodium persulfate mixed solution

The mechanical processing of cemented carbide often generates a considerable amount of grinding waste from cemented carbide (GWCC), which serves as an important secondary resource for recovering Co and W. However, efficient separation of tungsten carbide (WC) and Co from GWCC remains challenging. This study tested an efficient process for separating Co from GWCC using a mixed solution of H2SO4-Na2S2O8. Under optimum conditions of 20 g/L H2SO4, 30 g/L Na2S2O8, 60 °C, and 1 h, the leaching efficiency of Co reached 97.0 %, compared to only 58.6 % when using H2SO4 alone. The kinetics of Co leaching in H2SO4 and H2SO4-Na2S2O8 solutions were determined to be a combination of chemical reaction control and diffusion control, suggesting that Co leaching rate in H2SO4 solution is significantly enhanced by introducing Na2S2O8. Finally, complete recovery of Co was achieved, and pure Co powder with a flower-cluster morphology was prepared from the leaching solution through oxalic acid precipitation followed by vacuum pyrolysis. The regenerative WC and Co powder can be recycled for cemented carbide production.

Coarse-grained WC–6Co hardmetals with dual-scale and plate-like WC structures fabricated by convention powder metallurgy process

In this work, coarse-grained WC–6Co hardmetals featuring dual-scale and plate-like structures were successfully fabricated via conventional powder metallurgy process using W, ultrafine WC, Co and carbon black as raw materials. The investigation focuses on the effects of two critical factors, sintering temperature and ultrafine WC powder content, on the microstructures, densities, and mechanical properties. The results demonstrate that increasing the sintering temperature accelerates the growth of WC grains via 2D nucleation growth mechanism, thus enhancing the plate-like structure of WC grains. The addition of ultrafine WC powder reduces the mean WC grain size and eliminates the preferential orientation of WC grains because of its separating effect on coarse WC grains. Moreover, the dual-scale and plate-like structures can be achieved with sufficient ultrafine WC content (≥ 20 wt%) and adequate sintering temperature (≥ 1500 °C). Notably, the coarse-grained WC–6Co alloy sintered at 1550 °C with the addition of 20 wt% ultrafine WC powder exhibits good comprehensive mechanical properties: hardness of 1493 ± 7 HV30, transverse rupture strength of 2698 ± 58 MPa and fracture toughness of 16.93 ± 0.65 MPa·m1/2.

Insight into Grain Refinement Mechanisms of WC Cemented Carbide with Al0.5CoCrFeNiTi0.5 Binder.

High-entropy alloys (HEA) as a kind of new binder for cemented carbide have garnered significant attention. In this work, WC/(17~25 wt.%)Al0.5CoCrFeNiTi0.5 cemented carbides were prepared by hot pressing sintering (HPS), and the reactions between WC powder and Al0.5CoCrFeNiTi0.5 powder during hot pressing sintering were elucidated. It found that different from traditional Co binder, the Al0.5CoCrFeNiTi0.5 binder effectively inhibited WC grain growth. During HPS, the decomposed W and C atoms from WC diffused into the Al0.5CoCrFeNiTi0.5 binder, reacted with the elements in the binder, and then formed the M(Co, Fe, Ni)3W3C phase. The back-diffusion of W and C atoms to WC grains was restricted by the Al0.5CoCrFeNiTi0.5 alloy and inhibited them from re-precipitating onto the large undissolved WC grains. As a result, the average size of WC grains in the cemented carbides was less than 200 nm. This work bright new insight into the grain refinement mechanisms of WC cemented carbide with HEA binder and provide a guidance for designing performance-stable WC/HEA cemented carbide and promoting their application.

Microstructure and wear properties of carbide reinforced high-entropy alloy coatings on EA4T steel via vibration assisted TIG-cladding using WC core spiral AlCuNiCrTi-CWW

Aiming at the difficulty preparing high-entropy alloy (HEA) coating by adding carbide powder using TIG-cladding, the WC core spiral CWW prefabricated vibration assisted TIG-cladding method is proposed in this work. The HEA coating (S1-coating) was prepared on the EA4T steel using AlCuNiCrTi cable-type welding wire (CWW) via TIG-cladding, then the WC reinforced HEA coating (S2-coating) was produced using spiral AlCuNiCrTi-CWW with WC powder core by TIG-cladding. Finally, another WC reinforced HEA coating (S3-coating) via vibration assistance TIG-cladding using the same material as S2-coating. The S1-coating is composed of BCC and FCC solid solutions. Except for the same phases as S1-coating, TiC appeared in the S2-coating and the S3-coating. Due to the grain refinement effect caused by vibration, the S3-coating has the maximum microhardness (725HV), lowest friction coefficient (0.42) and the smallest volume wear rate (0.1397 × 10−4 mm3/N·m). The addition of vibration assistance effectively improves the microhardness and wear resistance of the coating without changing CWW composition.

Feasible production of highly homogeneous nano-scaled WC powders: An industrial practice via raw material pretreatment and direct reduction-carbonization

A method for industrial production of nano-scaled WC powders has been proposed. In this work, WO2.9 is subject to pre-reduction, followed by jet-milling treatment. The precursor is then mixed with carbon black by ball milling, and directly reduced-carbonized to nano-scaled WC powders. The WC powders prepared at different carbonization temperatures were made into alloys and micro drills, revealing the influence of powder properties on the microstructure and properties of the alloys through comparative analysis. The results indicate that when WO2.9 powder is reduced at 700 °C for 1h and then jet-milled at a rotational speed of the grading wheel of 3500 rpm, the aggregates in the powder can be effectively broken, and the precursor powders with fine particle size and near-single phase can be obtained. In this way, the equipment exhibits relatively high productivity. By comparing the microstructure and properties of the alloy prepared from raw materials at different carbonization temperatures, it can be seen that if the carbonization temperature is too high, the average particle size of the powder increases and agglomeration appears in the microstructure. An increase in the average particle size of the powder will lead to an increase in the average grain size of the prepared alloys, thereby reducing the hardness and the wear resistance during service. In addition, the agglomerated particles in the powders can easily lead to abnormal WC grain growth in the microstructure of the prepared alloys, which reduces the bending strength.

Effects of sintering method and Al2O3 content on microstructure and mechanical properties of WC-10Co cemented carbide

Ultra-high toughness and ultra-high hardness WC-10Co-xAl2O3 cemented carbides were successfully prepared by vacuum liquid phase sintering (VS) and spark plasma sintering (SPS) using ultrafine WC and commercial Co powders as raw materials, respectively. The effects of nano-Al2O3 content and sintering process on the relative density, average grain size, microstructure and mechanical properties of WC-10Co alloys were investigated. The results showed that the densification degree of the samples decreased with the increase of Al2O3 content. In addition, the relative densities of the samples prepared by SPS were lower than those of the samples prepared by VS. For the samples prepared by VS, the average grain size increased first and then decreased as the Al2O3 content increased from 3 wt% to 9 wt%, and the percentage of coarse grain showed the same trend. When the addition of Al2O3 was 6 wt%, the average grain size reached the maximum value of 1.39 ± 1.03 μm. Meanwhile, the sample with 6 wt% Al2O3 had a typical inhomogeneous dual-grain structure, and the percentages of fine grain (< 1 μm) and coarse grain (> 1 μm) were about 50%, which displayed the highest fracture toughness of 18.59 MPa·m1/2. The dual-grain structure not only improved the toughness, but also compensated the loss of hardness. However, for the samples prepared by SPS, with the increase of Al2O3 content, the average grain size of WC decreased, while both hardness and toughness were continuously improved. When the Al2O3 content increased to 9 wt%, the grain size reached the minimum value of 0.25 ± 0.08 μm, and meanwhile, the hardness and toughness reached the maximum value of 19.69 GPa and 12.29 MPa·m1/2, respectively. Moreover, as the Al2O3 content increased, the transverse rupture strength (TRS) of the samples prepared by VS increased first and then decreased, and the TRS of sample with 3 wt% Al2O3 reached the maximum value of 1410 MPa. However, the TRS of the sample prepared by SPS showed a decreasing trend.

Study of the Phase Composition and Microstructure of Complex Carbide (Ti, W)C Obtained by Spark Plasma Sintering of WC and TiC Powders

Study of the Phase Composition and Microstructure of Complex Carbide (Ti, W)C Obtained by Spark Plasma Sintering of WC and TiC Powders

Determination of selective laser melting process parameters of tungsten carbide powders coated with nickel via electroless plating for improved interface properties

Tungsten carbide powders are commonly used at various industrial applications due to their high hardness. However, these powders may exhibit low binding and processing challenges without a binder. Therefore, various binding methods such as electroless Ni coating are used to hold WC powders together, increase their processability and improve the mechanical properties of the final product. Electroless Ni plating plays an important role in the use of WC powders, especially in processes such as selective laser melting. The structural, tribological, and mechanical properties of parts manufactured by SLM method are significantly influenced by the parameters employed in the process. Hence, optimizing process variables is essential to unlock the full potential of this advanced manufacturing technique. The main objective of this study was to identify the optimum process parameters for the SLM method of WC-Ni composite powders, which were prepared by coating WC powder materials with electroless Ni. Experimental investigations focused on analyzing the laser power, scanning speed, and hatch spacing parameters. The effects of these parameters on the mechanical and tribological properties of WC-Ni composite material were investigated using microhardness tester, tribometer device, optical microscope, 3D optical profilometer and scanning electron microscope. Eventually, it was determined that the manufacturing parameters employed in the SLM method had a significant impact on relative density, microstructure, surface roughness, hardness, and tribological properties. Samples exhibited a relative density of nearly 99%, and the highest observed hardness value was 1962 HV. This article supports a specialized SLM manufacturing process developed specifically to enhance durability and performance across a broad spectrum of industrial applications through interface improvement and the optimization of manufacturing parameters.

Effect of Cold Isostatic Pressing and VC Grain Growth Inhibitor Addition on WC Grain Size and Mechanical Properties of WC-8Co Cemented Carbide

In this study, sub-micron WC-Co cemented carbides were fabricated by cold isostatic pressing using recycled WC powder, Co powder, and VC grain growth inhibitor as the initial composite powders. The raw WC-8Co and WC-8Co-0.3VC compositions were prepared according to conventional technology. After that, part of the green compacts was CIP-ed under pressure of 200 MPa. Sintering was carried out in an industrial vacuum sintering furnace at a temperature of 1420 ºC simultaneously for all samples. The microstructures and properties, including density, coercivity, transverse rupture strength, A-type Rockwell hardness and fracture toughness were investigated, characterized and compared systematically. The experimental results showed that the action of cold isostatic pressing in combination with grain growth inhibitor addition promoted ultrafine grains with the finest WC grain size of 0.68 μm and an increase in the fracture toughness up to 15.4 MPa·m1/2 ± 0.2 compared to rest cemented carbides, showing the techniquehas potential to fabricate cermets with both small average WC grain size and high fracture toughness, which is key in providing excellent performance.

Laser powder bed fusion of pure Nb and Nb + WC powder mixture

Additive Manufacturing (AM) of high temperature refractory metals, including Nb-based alloys, can overcome the challenges associated with their processing using the conventional methods. In this study, pure Nb and a blend of Nb with 2.5 wt% WC was processed with Laser Powder Bed Fusion (LPBF) starting with a full optimisation cycle that explored the impact of the laser power, scan speed, hatch spacing, and layer thickness on the build integrity. Results show that both materials have good processability, as confirmed by the lack of cracking and other defects once the parameters are optimised. Nevertheless, the process parameters affected the materials in different ways. Increasing both the scan speed and laser power resulted in hardness increase in pure Nb. However, this was not seen in the case of the Nb + 2.5 wt% WC powder mixture. In fact, the hardness was on average ∼ 15% lower in the Nb + WC builds compared with pure Nb builds. This observation was elucidated through studying the effect of the process on the oxygen pick-up in pure Nb and the dissociation of the carbide in the Nb + WC mixture. Although the hardening effect is expected due to the full solubility of W in Nb or due to the formation of carbides, results indicate that oxygen pick-up has a greater impact on hardness.

Effects of WC/TiC addition on the thermodynamic behavior of TiB2-based cermet during sintering process

The heat absorption, weight change and exhaust behavior of TiB2-based cermet powder mixtures with additions of WC, TiC and WC-TiC were analyzed by a simultaneous thermal analyzer coupled with a mass spectrometer (TG/DSC-QMS). Thermodilatometry was used to investigate the densification behavior due to sintering process of cermets. During the sintering process, the order of degassing is: water vapor, CO2 released by the reduction of adsorbed oxygen in the raw material powder, CO and CO2 released by the reduction of surface oxides of Co and Ni powder, WC powder, TiB2 and TiC powder. The addition of WC, TiC and WC-TiC accelerated the reduction of oxides on the surface of Co and Ni powders, and decreased the temperature point of liquid phase formation in TiB2-based cermet. WC and TiC dissolved in liquid CoNi binder and then precipitated on the undissolved TiB2 particles to form a typical core-rim structure during the sintering. This study is expected to lay a solid foundation for the development of high-performance TiB2-based cermets based on TiB2-CoNi, TiB2-WC-CoNi, TiB2-TiC-CoNi and TiB2-WC-TiC-CoNi cermets in the future.

Повышение износостойкости цилиндрических поверхностей трения комбинированной электромеханической обработкой

Processing technology and technological equipment for the formation of a wear-resistant surface layer by implanting materials based on tungsten carbide (WC), are viewed. The effect of implanted WC powder on the formation of gradient wear-resistant structures in the friction surface of carbon steel formed during the implementation of combined electromechanical processing (WRCEMP) technology, has been studied. Resulting from heat and pressure impact in the zone of plastic deformation, intensive austenization of steel occurs with dissolution of WC powder and subsequent formation of highly dispersed composite structures caused by the decomposition of undercooled tangstem-supersaturated austenite. Combined comparative friction and wear tests were carried out for structural steel 45 with a graded structure of a hardened surface and rather expensive and technologically- difficult to obtain modern wear-resistant coatings and materials. The issue of WRCEMP technology practical application used for the «axis of satellite – satellite» friction pair is viewed. An assessment of the durability increase of the «axis of satellite – satellite» interface during the implementation of the considered processing methods and innovative technology was taken. Recommendations for the use of combined electromechanical processing technology at machine-building enterprises as a highly effective way to ensure and improve the performance of machine parts at the stage of their manufacture are given.

Refining mechanisms of arsenic during preparation process of ultrafine WC powder by nitridation−carbonization method

To simplify the preparation process and prepare ultrafine WC powder, a certain amount of As element was added to the ammonium paratungstate precursor. The mechanism of As in the preparation process of ultrafine WC powder by nitridation−carbonization method was systematically discussed. The results show that when the carbonization temperature was 1400 °C, the nitridation temperature increased from 500 to 600 °C, and the As content increased from 0 to 0.3 wt.%, the average particle size of the prepared WC powder decreased from 2.23 to 0.22 μm, and the particle uniformity was significantly improved. The As element in the nitrided product was in the form of W2O3(AsO4)2, which was easily enriched or distributed between the two phases on the surface of the nitrided products (NH4)0.42WO3 and WN, hindering the growth of WC grains during the carbonization process. Consequently, ultrafine WC powder was prepared.

Effect of ingredients proportions on mechanical properties in laser-coated WC-blend welds

Abstract In this study, we investigated ceramic-matrix composite coatings created by laser cladding on 45 steel using tungsten carbide (WC) powder with varying weight percentages of Co or Ni additives. Our analysis focused on the influence of Co additives in WC powders on the key properties of the coatings, including the microstructural evolution, hardness, wear, and residual stress behaviors. High residual stresses led to significant cracking in coatings comprising 100% WC. The addition of Co at a concentration of 20% to WC reduces the cracking activity. The microhardness of the coating exceeded that of the substrate by a factor of more than five. The microstructural evolution revealed a typical intergranular fracture in the molten zone, with cracks propagating through the interior of the unmelted WC at 100% WC. In addition, by adding Ni alloys, the composite coatings were extended to three mixtures: WC-Co, WC-Ni, and WC-Co-Ni. The relationship between the three-component mixtures and wear volume of the laser cladding was established, and the ratios of the three-component mixtures were optimized. A reduced quadratic model for three-component mixtures, which provided a better mixture ratio pattern, showed an excellent fit. Based on the experimental results, the developed three-component mixture with better mixture ratios can enhance anti-wear behavior. A satisfactory agreement was obtained between the predicted and experimental values of the wear volume of the laser-coated welds. Overall, our study accomplishes the optimization of the mixture ratio of the three components, which ensured a reduction in the wear of the welds, thereby improving the performance of laser-coated welds.

Microstructure and Mechanical Properties of TiC/WC-Reinforced AlCoCrFeNi High-Entropy Alloys Prepared by Laser Cladding

By employing the technology of laser cladding, AlCoCrFeNi–TiC20−x/WCx high-entropy alloy coatings (where x = 0, 5, 10, 15, and 20 is the mass fraction) were fabricated on 316L stainless steel (316Lss). The effects of changes in different mass fractions on the morphology, phase composition, microstructure, microhardness, and corrosion resistance of the composite coatings were studied. This demonstrates that the addition of TiC and WC powder produces an FCC phase in the original BCC phase, the morphology and size of the coatings from top to bottom undergo some changes with x, and the grain size evolution follows a cooling rate law. The evolution of microhardness and corrosion resistance of the coatings exhibit a trend of increasing first and then decreasing with an increase in x. The coatings exhibited their best microhardness and corrosion resistance when x = 15, and their corrosion resistance and microhardness were much better than those of the substrate.

Microstructure and properties analysis of Ni60-based/WC composite coatings prepared by laser cladding

In this study, Ni60-WCx coatings (x = 0, 2, 4, 6 %) on 316L stainless steel (316Lss) were prepared via laser cladding technology. We examined all specimens s for microstructure, phase composition, microhardness and electrochemistry using several characterization techniques. It shows that the microstructure of the Ni-based coatings can be changed with WC powder. When the WC ratio is 2 %, crystalline crystals and cellular crystals can be found in the coating. As the WC ratio increases, more cellular crystals and fewer spiny crystals appear in the coating. When the WC ratio changes to 6 %, only cellular crystals can be found in the coating. The microhardness resultsshow that the Ni-based overcoat with added WC has a better microhardness compared to the pure Ni coating, and its average value of the coating area reaches a maximum value of 822.8 HV at a WC ratio of 2 %. That is due to the addition of WC which can cause regime transition. In addition, the Ni-based coating has better corrosion properties due to its different microstructure. When the WC ratio is 2 %, the specimen possesses the maximum Ecorr and smaller icorr with the best corrosion resistance.

Analysis of the sequentially coupled thermal–mechanical and cladding geometry of a Ni60A-25 %WC laser cladding composite coating

In this research, a three-dimensional (3D) transient finite element model based on a sequentially coupled thermal–mechanical analysis (SCTMA) is proposed to simulate the evolution of the temperature field and stress field as well as the cladding geometry of the Ni60A-25 % WC laser cladding composite coating. Based on the thermo-physical properties of Ni60A-25 % WC powder and the design of the double ellipsoidal heat source model, a 3D finite element model of double-layer laser cladding with two channels is established. The evolution of the temperature field and the residual stress field at different laser process parameters are investigated to evaluate the quality of the cladding layer. The impact of different laser cladding process parameters on the cladding dimensions is investigated. The dimensions of the simulated molten pool are analyzed by fitting a polynomial curve. The simulation results show that the laser power is proportional to the temperature, and the temperature growth rate of the coating is significantly higher than that of the substrate. The scanning speed is inversely proportional to the temperature. The maximum temperature of the cladding is 1.5 times the maximum temperature of the substrate. The temperature growth rate of the cladding layer is twice that of the substrate. Due to the asymmetry of the heat source in the multi-pass cladding process, the laser energy absorption rate is not the same on both sides of the melted layer. The double ellipsoidal heat source model has a larger diffusion range in the un-melted powder, resulting in asymmetry in the width direction of the cladding layer. The analysis of the residual stresses in the cladding layer shows that the residual compressive stresses in all paths increase with the increasing laser power. The normal x residual compressive stress in the coating and the maximum residual compressive stress occur at the end of the laser beam scan. The residual compressive stress in all paths decreases as the scanning speed increases. The results show that the dimensions of the molten pool are proportional to the laser power and inversely proportional to the scanning speed. The cladding geometry can be calculated with polynomial fitting equations at a selected laser power (500 W–2800 W) and scanning speed (1 mm/s–8 mm/s). The error analysis of the simulation and the experimental results can validate the proposed finite element simulation model. The error in the molten pool size is less than 20 % for the simulation and experimental results.

COATING OF ST37 STRUCTURAL STEEL SURFACE WITH WC-ST6-ST21 AND FERRO55 USING LASER CLADDING TECHNIQUE AND INVESTIGATION OF SURFACE HARDNESS

Improving material properties such as surface hardness and wear resistance play a vital role in modern industrial applications. Surface coating techniques offer a practical approach to achieve these improvements. This study focuses on laser cladding as a method to coat ST37 structural steel material with WC, ST6, ST21 and Ferro55 powders and investigates the resulting surface hardness. ST37 structural steel with a base hardness of 120 HV was used as the starting material. Laser cladding was used to apply WC, ST6, ST21 and Ferro55 powders to the steel surfaces using various process parameters. Hardness measurements of the laser cladded samples were carried out using HV0.3 load for evaluation. The study examines the surface hardness differences between ST37 steel samples coated with different powders, highlighting the highest and lowest hardness values.

Parametric investigation and optimization in laser based directed energy deposition of tungsten carbide-cobalt

Cemented carbide (WC-Co), the widely used tool-die material, is difficult to be machined by conventional and nonconventional techniques. This inspired exploring additive manufacturing (AM) of this material. However, porosity, brittleness due to cobalt depletion, etc. have been reported in the literature with rare success. For the AM of WC-Co, the current work focuses on directed energy deposition, which can be implemented with existing laser cutting-welding workstations, with modifications. To ensure the retention of cobalt even after inevitable vaporization of some of its initial content during deposition, 20 wt. % of Co was mixed with WC powder by low-energy ball milling. Laser power, scan speed, and powder flow rate were varied following a full-factorial design of experiments. The analysis of variance revealed that the experimental model and most of the parameters were significant. Only the laser power came out to be insignificant for the contact angle. The track height and width increased with the laser power and reduced with the scan speed. The contact angle increased with the scan speed and reduced with the powder flow rate. Cross sections of the deposited track showed no pores or cracks. Multiobjective optimization with gray relational analysis was conducted to get the parameter combination giving high values of the contact angle, track height, and width simultaneously. The optimum parameter combination, thus, obtained is 700 W laser power, 5 mm/s scan speed, and 5 g/min powder flow rate. This yielded 305 ± 40 μm track height, 2132 ± 33 μm width, and 152° ± 2° contact angle.

Analysis on carbonization evolution behavior of tungsten carbide powders and its application in cutting tools

In this article, the microstructural evolution of tungsten carbide (WC) powder with coarse particle size was studied. The WC powders were prepared by directly carbonizing tungsten powders of 8.5 μm in Fisher sub-sieve size (FSSS) under various conditions. The sequence of chemical reactions was analyzed by calculating the Gibbs free energies, and the phase transition mechanisms of tungsten particles was studied by using characterization techniques including SEM and XRD. The experimental results showed that the phase transition process is dominated by carbon diffusion reaction, and the diffusion rate was studied by analyzing carbonized tungsten particles prepared at specific temperatures. The grain growth process and mechanism were also studied by analyzing the morphology and grain size of WC powders prepared at 1800 °C in different carbonization times, and the results are consistent with the recrystallization grain growth theory. Finally, technique of Electron Backscattered Diffraction (EBSD) was utilized to identify and measure the grain size of WC powders prepared from tungsten powder of 0.6 μm in FSSS. The cemented tungsten carbide substrate prepared from WC powder with higher average grain size exhibited higher performances in metal cutting application of turning and drilling.