Preparation method of high solid phase WC-Co water-based slurry for direct writing shaping

Abstract

This invention belongs to the field of cemented carbide additive manufacturing technology and discloses a method for preparing a high-solids WC-Co water-based slurry for direct-write forming. The invention uses cobalt-coated tungsten carbide powder as the solid phase, which is dispersed in an aqueous solution of ammonium citrate and polyethylene glycol composite additives to obtain a WC-Co water-based slurry with a solid content of 90wt%~93wt%. The slurry of this invention exhibits good shear-thinning properties and extrusion shape retention, with a total dispersant dosage of only 1~1.2wt%. After direct-write 3D printing and debinding sintering, a density ≥99% and a Vickers hardness >1900HV can be obtained. 30 The complex structure of WC-Co cemented carbide components is suitable for the low-cost preparation of high-performance cemented carbide in industrial applications.

Description

Technical Field

[0001] This invention relates to the field of cemented carbide additive manufacturing, and more specifically to a method for preparing a high-solids WC-Co water-based slurry for direct writing. Background Technology

[0002] Due to their excellent mechanical and wear-resistant properties, cemented carbide is widely used in various fields such as machining, mining, and aerospace. Traditional cemented carbide forming processes are mature, but when manufacturing complex structural parts, there are problems such as high mold design and manufacturing costs, cumbersome and difficult subsequent precision machining processes, and serious material waste, making it difficult to meet the demand for efficient and low-cost manufacturing of complex components.

[0003] The rise of additive manufacturing technology has provided a new path for the preparation of complex cemented carbide components, enabling moldless direct forming and effectively solving the aforementioned drawbacks of traditional forming processes. Currently, additive manufacturing of WC-Co cemented carbide is mainly divided into two technical routes: one is powder melting technology based on hot forming. This technology is prone to introducing defects such as brittle phases, porosity, and cracks into the formed parts due to rapid heating and cooling during the forming process and large temperature gradients, affecting product quality. At the same time, this technology requires large equipment investment, high energy consumption, and low powder utilization, further increasing the preparation cost. The other is forming-debinding-sintering technology based on cold forming. However, this type of cold forming process has its own limitations: fused deposition modeling (FDM) usually requires heating the needle to melt the binder to drive the material extrusion; binder jetting (BJ) does not require heating, but still requires powder spreading, and the produced green compact has a low density; photopolymerization (SLA) technology does not require an additional heat source, but WC, as a black substance, has a high absorption rate of ultraviolet light, which is not conducive to curing and forming.

[0004] Among the aforementioned cold forming technologies, direct-write forming (DIW) has become an important development direction for WC-Co cemented carbide additive manufacturing due to its advantages such as no need for powder spreading, relatively simple equipment structure, no need for external heat sources, lower cost, and the ability to produce high-density cemented carbide products after subsequent debinding and sintering. The core challenge of this technology lies in preparing a slurry that meets the requirements of direct-write forming. This slurry must simultaneously possess high solid content, good stability, and suitable fluidity to ensure forming accuracy and subsequent sintering quality.

[0005] The slurry required for direct-write forming technology, in addition to possessing shear-thinning properties, must also meet the requirements of high solid content and low viscosity. Compared with slurry prepared by directly mixing tungsten carbide (WC) powder and cobalt powder, slurry prepared by cobalt-coated tungsten carbide powder has significant advantages: on the one hand, it can reduce the direct friction and mechanical interlocking effect between high-hardness, multi-faceted WC particles, making the particles more prone to relative slippage under shear force; on the other hand, the highly uniform surface properties of the coated powder particles give the slurry a more stable rheological response under shear force, effectively reducing the slurry viscosity and further increasing the solid content. Furthermore, directly mixed powders are prone to uneven distribution of the binder phase during ball milling and printing, leading to the formation of localized cobalt pools after sintering, which affects product performance.

[0006] Currently, the slurries used in forming-debinding-sintering technology are mostly organic solvent systems. These slurries are not only highly toxic, have a pungent odor, and are environmentally unfriendly, but the high cost of organic solvents also hinders large-scale production. To address these issues, research has shifted towards the development of water-based slurries. However, existing water-based slurries typically require the addition of more than 1.9 wt% dispersant to optimize rheological properties, resulting in persistently high slurry preparation costs. This makes it difficult to achieve low-cost, large-scale preparation of WC-Co cemented carbides, thus limiting the widespread application of direct-write forming technology. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of existing technologies in the preparation of WC-Co water-based slurry for direct-write forming and the preparation of WC-Co cemented carbide, and to provide a method for preparing a high-solid-phase WC-Co water-based slurry for direct-write forming. The aim is to obtain a WC-Co water-based slurry with both good rheological properties and high solid content, which is suitable for the direct-write forming process, thereby achieving efficient and low-cost preparation of WC-Co cemented carbide. This ensures that the WC-Co cemented carbide obtained after direct-write 3D printing and sintering has excellent density and hardness properties, meeting the practical application needs of the industrial field.

[0008] To achieve its objectives, the present invention employs the following technical solution:

[0009] This invention first provides a method for preparing a high-solids WC-Co water-based slurry for direct writing molding, comprising the following steps:

[0010] (1) Preparation of cobalt-coated tungsten carbide powder: Cobalt chloride hexahydrate was dissolved in an ethanol solution, tungsten carbide powder was added, and mechanical stirring and ultrasonic treatment were performed in sequence to obtain a mixture; the mixture was thoroughly dried to obtain a composite powder; the composite powder was placed in a tube furnace and reduced in a hydrogen atmosphere; the reduced powder was taken out and ground until there were no lumpy particles to obtain uniformly dispersed cobalt-coated tungsten carbide powder;

[0011] (2) Preparation of WC-Co water-based slurry: The cobalt-coated tungsten carbide powder obtained in step (1) is dispersed in an aqueous solution of additives to prepare a WC-Co water-based slurry with a solid content of 90wt%-93wt%.

[0012] As a preferred embodiment, in step (1), the mass percentage of tungsten carbide powder to cobalt chloride hexahydrate is 85.6%~49.8%:14.4%~50.2%.

[0013] As a preferred embodiment, in step (1), the mechanical stirring time is 6~12h and the stirring speed is 300~500rpm, and the ultrasonic frequency of the ultrasonic treatment is 30~50kHz and the ultrasonic time is 10~30min.

[0014] As a preferred option, in step (1), the drying temperature is 60~80℃.

[0015] As a preferred embodiment, in step (1), the reduction temperature is 500~700℃, the reduction time is 2~5h, and the hydrogen flow rate is controlled at 150~200mL / min.

[0016] As a preferred embodiment, in step (2), the aqueous solution of the additive is a mixed aqueous solution of ammonium citrate and polyethylene glycol, wherein the mass ratio of ammonium citrate to polyethylene glycol is 1~5:1, and the total mass percentage of ammonium citrate and polyethylene glycol in WC-Co water-based slurry is 1~1.2wt%.

[0017] As a preferred embodiment, in step (2), the cobalt-coated tungsten carbide powder is dispersed in an aqueous solution of additives at room temperature.

[0018] This invention further provides a WC-Co cemented carbide, which is prepared by 3D printing and debinding / sintering of the aforementioned WC-Co water-based slurry. The specific preparation process is as follows: The WC-Co water-based slurry is printed using a direct-write 3D printer at room temperature to obtain a WC-Co composite material green body; the WC-Co composite material green body is then subjected to debinding and sintering treatments to obtain the WC-Co cemented carbide.

[0019] As a preferred embodiment, the sintering temperature is 1450°C.

[0020] Compared with the prior art, the beneficial effects of the present invention are reflected in:

[0021] (1) In view of the need for direct writing high solid phase water-based slurry, the present invention designed a preparation process of cobalt-coated tungsten carbide powder. By precisely controlling the ratio of tungsten carbide powder to cobalt chloride hexahydrate and the process parameters of stirring, ultrasonication and hydrogen reduction, cobalt-coated tungsten carbide powder with uniform and continuous cobalt layer, uniform surface properties and no impurity residue is prepared. The powder has excellent compatibility with water-based additives and lays a structural foundation for the subsequent preparation of high solid phase water-based slurry.

[0022] (2) This invention uses cobalt-coated tungsten carbide powder as the solid phase basis and combines the rheological optimization effect of composite additives to successfully increase the solid phase content of WC-Co water-based slurry to 90wt% and above (90~93wt%). This effectively solves the technical problems of low solid phase content and poor rheological properties of existing water-based slurries, enabling them to accurately meet the high-precision forming requirements of direct writing forming process, and providing a guarantee for the forming accuracy and subsequent sintering quality of direct writing 3D printing.

[0023] (3) The WC-Co water-based slurry prepared in this invention adopts an environmentally friendly water-based system, combined with a low addition amount (1~1.2wt%) of ammonium citrate and polyethylene glycol composite additive, which form a synergistic effect: ammonium citrate can efficiently disperse cobalt-coated tungsten carbide powder and prevent particle agglomeration; polyethylene glycol can improve the lubricity and stability of the slurry, reduce printhead clogging and further reduce the viscosity of the slurry, which helps to achieve high solid content. Compared with existing organic solvent slurries, the slurry of this invention is more environmentally friendly and has a lower preparation cost; compared with existing water-based slurries, this invention significantly reduces the amount of dispersant used, significantly reduces the slurry preparation cost, and is more suitable for large-scale industrial production.

[0024] (4) The present invention uses self-made cobalt-coated tungsten carbide powder to prepare slurry, which effectively weakens the direct friction and mechanical interlocking effect between WC particles, improves the dispersion stability and rheological response stability of slurry, ensures the continuous and smooth direct writing printing process and reduces green defects; at the same time, it avoids the problem of uneven distribution of binder phase and formation of local "cobalt pool" after sintering that is easy to occur in traditional mixed powder slurry, laying a structural foundation for the high performance of subsequent cemented carbide.

[0025] (5) The WC-Co water-based slurry prepared by the technical solution of self-made cobalt-coated tungsten carbide powder, low-addition composite water-based additive, and 90~93wt% high solid content of the present invention has the characteristics of high solid content, excellent rheology, and strong stability. After direct writing 3D printing and subsequent debinding and sintering, the density of the WC-Co cemented carbide can reach more than 99%, and the Vickers hardness is higher than 1900HV. 30 It possesses excellent density and mechanical properties, which can fully meet the high-performance requirements of complex WC-Co cemented carbide components in the industrial field, and broaden the application scenarios of direct writing forming technology in the field of cemented carbide additive manufacturing. Attached Figure Description

[0026] Figure 1 TEM (transmission electron microscopy) image of the cobalt-coated tungsten carbide powder prepared in Example 1;

[0027] Figure 2 This is a TEM-EDS (energy dispersive spectroscopy) elemental surface scan overlay of the cobalt-coated tungsten carbide powder prepared in Example 1;

[0028] Figure 3 The viscosity variation trend of WC-Co water-based slurries prepared in Examples 1-4 at different rotation speeds is shown in the figure.

[0029] Figure 4 The graph shows the trend of zeta potential changes of the WC-Co water-based slurry prepared in Example 4 under different standing times;

[0030] Figure 5 The images shown are SEM (scanning electron microscope) images and corresponding EDS elemental surface scan images of the fracture surface of the WC-Co cemented carbide prepared in Example 4, where a is the SEM morphology image, b is the W element surface scan image, c is the C element surface scan image, and d is the Co element surface scan image.

[0031] Figure 6 The XRD (X-ray diffraction) pattern of the WC-Co cemented carbide prepared in Example 4;

[0032] Figure 7 Microhardness indentation metallographic image of the WC-Co cemented carbide prepared in Example 4;

[0033] Figure 8 The viscosity variation curves of cobalt-coated tungsten carbide powder, pure tungsten carbide powder, and tungsten carbide and cobalt mixed powder in Comparative Example 1 under different solid phase contents are shown.

[0034] Figure 9 The viscosity change curves of cobalt-coated tungsten carbide powder in Comparative Example 2 after adding different types and amounts of dispersants;

[0035] Figure 10 The density and hardness curves of the WC-Co cemented carbide obtained after sintering the printed green blank at different temperatures are shown in Comparative Example 3. Detailed Implementation

[0036] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] Example 1

[0038] This embodiment prepares a high-solids WC-Co water-based slurry for direct writing forming according to the following steps, and prepares WC-Co cemented carbide based on it:

[0039] (1) Preparation of cobalt-coated tungsten carbide powder: The mass percentage of tungsten carbide powder to cobalt chloride hexahydrate was 73.9%:26.1% (corresponding to a cobalt coating amount of 8%). Cobalt chloride hexahydrate was dissolved in an ethanol solution, and tungsten carbide powder was added. The mixture was mechanically stirred (400 rpm, 8 h) and ultrasonically treated (40 kHz, 20 min) to obtain a mixture. The mixture was placed in a 70 ℃ drying oven and dried completely to obtain a composite powder. The composite powder was placed in a tube furnace and reduced at 700 ℃ for 3 h in a hydrogen atmosphere, with the hydrogen flow rate controlled at 200 mL / min. The reduced powder was taken out and ground until there were no lumpy particles to obtain uniformly dispersed cobalt-coated tungsten carbide powder.

[0040] (2) Preparation of WC-Co water-based slurry: Ammonium citrate (AC) and polyethylene glycol (PEG) are dissolved in deionized water to prepare a mixed aqueous solution with a mass ratio of AC to PEG of 1:1, and left to stand at room temperature for later use; at room temperature, cobalt-coated tungsten carbide powder is dispersed in the above AC+PEG mixed aqueous solution to prepare a WC-Co water-based slurry with a solid content of 90wt%, wherein the total mass percentage of AC and PEG in the WC-Co water-based slurry is 1.2wt%.

[0041] (3) 3D printing: At room temperature, the WC-Co water-based slurry prepared in step (2) was printed using a direct-write 3D printer to obtain a WC-Co composite material green body of the desired shape; the printing parameters were: nozzle diameter 0.66 mm, layer thickness 0.28 mm, line width 1 mm, printing speed 0.3 mL / min, and air pressure 0.6 kg / cm. 2 .

[0042] (4) Debinding and sintering: The WC-Co composite material green blank obtained in step (3) is processed by the above-mentioned traditional debinding-sintering process to obtain WC-Co cemented carbide. The specific process conditions for debinding and sintering are as follows:

[0043] Degreasing: Under a nitrogen atmosphere, the temperature is increased to 80°C at a rate of 5°C / min and held for 30 minutes, then increased to 400°C at a rate of 5°C / min and held for 30 minutes. The nitrogen flow rate is controlled at 150 mL / min.

[0044] Sintering: Under a nitrogen atmosphere, the temperature is increased to 1000℃ at a heating rate of 5℃ / min, held for 10 minutes, and then increased to 1450℃ at a heating rate of 3℃ / min, held for 120 minutes. The nitrogen flow rate is controlled at 100mL / min.

[0045] Example 2

[0046] This embodiment prepares a high-solids WC-Co water-based slurry for direct writing forming according to the following steps, and prepares WC-Co cemented carbide based on it:

[0047] (1) Preparation of cobalt-coated tungsten carbide powder: The steps are exactly the same as in Example 1.

[0048] (2) Preparation of WC-Co water-based slurry: Ammonium citrate (AC) and polyethylene glycol (PEG) are dissolved in deionized water to prepare a mixed aqueous solution with a mass ratio of AC to PEG of 5:1, and left to stand at room temperature for later use; at room temperature, cobalt-coated tungsten carbide powder is dispersed in the above AC+PEG mixed aqueous solution to prepare a WC-Co water-based slurry with a solid content of 90wt%, wherein the total mass percentage of AC and PEG in the WC-Co water-based slurry is 1.2wt%.

[0049] (3) 3D printing: The steps are exactly the same as in Example 1.

[0050] (4) Degreasing and sintering: The steps are exactly the same as in Example 1.

[0051] Example 3

[0052] This embodiment prepares a high-solids WC-Co water-based slurry for direct writing forming according to the following steps, and prepares WC-Co cemented carbide based on it:

[0053] (1) Preparation of cobalt-coated tungsten carbide powder: The steps are exactly the same as in Example 1.

[0054] (2) Preparation of WC-Co water-based slurry: Ammonium citrate (AC) and polyethylene glycol (PEG) are dissolved in deionized water to prepare a mixed aqueous solution with a mass ratio of AC to PEG of 1:1, and left to stand at room temperature for later use; at room temperature, cobalt-coated tungsten carbide powder is dispersed in the above AC+PEG mixed aqueous solution to prepare a WC-Co water-based slurry with a solid content of 93wt%, wherein the total mass percentage of AC and PEG in the WC-Co water-based slurry is 1.2wt%.

[0055] (3) 3D printing: The steps are exactly the same as in Example 1.

[0056] (4) Degreasing and sintering: The steps are exactly the same as in Example 1.

[0057] Example 4

[0058] This embodiment prepares a high-solids WC-Co water-based slurry for direct writing forming according to the following steps, and prepares WC-Co cemented carbide based on it:

[0059] (1) Preparation of cobalt-coated tungsten carbide powder: The steps are exactly the same as in Example 1.

[0060] (2) Preparation of WC-Co water-based slurry: Ammonium citrate (AC) and polyethylene glycol (PEG) were dissolved in deionized water to prepare a mixed aqueous solution with an AC to PEG mass ratio of 5:1, and left to stand at room temperature for later use; at room temperature, cobalt-coated tungsten carbide powder was dispersed in the above AC+PEG mixed aqueous solution to prepare a WC-Co water-based slurry with a solid content of 93wt%, wherein the total mass percentage of AC and PEG in the WC-Co water-based slurry was 1.2wt%.

[0061] (3) 3D printing: The steps are exactly the same as in Example 1.

[0062] (4) Degreasing and sintering: The steps are exactly the same as in Example 1.

[0063] Figure 1 The TEM image of the cobalt-coated tungsten carbide powder prepared in Example 1 shows that the powder has a polygonal particle morphology with clear particle edges and a uniform light-colored coating layer on the surface. The particle size is about several hundred nanometers, which provides a morphological basis for the subsequent optimization of the rheological properties of the high solid phase slurry.

[0064] Figure 2 The image shows a TEM-EDS elemental surface scan overlay of the cobalt-coated tungsten carbide powder prepared in Example 1. Green represents tungsten (W), and red represents cobalt (Co). The spatial distribution of the elements reveals that W is highly concentrated in the core region of the particles, forming the core framework of the tungsten carbide. Co, on the other hand, is uniformly and continuously distributed around the W, forming a distinct red shell, indicating the successful preparation of cobalt-coated tungsten carbide powder.

[0065] Figure 3 The graphs show the viscosity trends of the WC-Co water-based slurries prepared in Examples 1-4 at different rotation speeds. As can be seen from the graphs, the slurries in each example exhibit significant shear-thinning characteristics: the viscosity decreases significantly with increasing rotation speed. This characteristic allows the slurry to maintain good flowability during extrusion and rapidly recover high viscosity after deposition to maintain shape accuracy during direct-write 3D printing, meeting the requirements of the direct-write forming process. Among them, Example 4 (93wt% solid content, AC:PEG=5:1) exhibits moderate viscosity at low rotation speeds and excellent flowability at high rotation speeds, demonstrating the best overall rheological properties.

[0066] All of the above embodiments successfully prepared high-solids WC-Co water-based slurries (solid content 90wt%~93wt%) suitable for direct writing forming process, and obtained high-performance WC-Co cemented carbide through subsequent direct writing 3D printing and debinding sintering; among them, Example 4 had the best overall performance.

[0067] Figure 4 The figure shows the zeta potential variation trend of the WC-Co water-based slurry prepared in Example 4 under different standing times. As can be seen from the figure, the absolute value of the zeta potential of the slurry remained above 30mV throughout the standing time of 0~72h, and the change with time was minimal. This indicates that the slurry has excellent dispersion stability, is not prone to particle agglomeration and sedimentation, and can be stored for a long time, meeting the process requirements of industrial continuous direct-write 3D printing.

[0068] Figure 5 The images show SEM and EDS elemental surface scans of the fracture surface of the WC-Co cemented carbide prepared in Example 4. In the images, red represents tungsten, green represents carbon, and yellow represents cobalt. The SEM images show tightly packed and relatively uniform grain size. The EDS elemental surface scans show a relatively uniform elemental distribution with no decarburization. This provides a theoretical basis for the excellent density and hardness of the prepared cemented carbide.

[0069] Figure 6 The XRD pattern of the WC-Co cemented carbide prepared in Example 4 is shown. The pattern shows that the diffraction peaks of the sample are highly consistent with the standard cards for WC (PDF#51-0939) and Co (PDF#15-0806), and the peaks are sharp, indicating good crystallinity of the alloy. Furthermore, no oxide or other impurity phase diffraction peaks were detected in the pattern, confirming that no significant oxidation or adverse side reactions occurred during the preparation and sintering process of this invention, and that the alloy phase is pure, thus ensuring the density and mechanical property stability of the cemented carbide.

[0070] Figure 7 The image shows a microhardness indentation metallographic image of the WC-Co cemented carbide prepared in Example 4. The indentation edges are clear and free of obvious cracks, indicating that the cemented carbide has a dense internal structure and uniform mechanical properties. Combined with performance test data, the cemented carbide has a density exceeding 99% and a Vickers hardness higher than 1900 HV. 30 It can meet the high-performance requirements of WC-Co cemented carbide components in the industrial field.

[0071] Comparative Example 1

[0072] To verify the rheological advantages of cobalt-coated tungsten carbide powder, three sets of control samples were set up: cobalt-coated tungsten carbide powder prepared in Example 1; pure tungsten carbide powder; and a mixed powder of 92 wt% tungsten carbide and 8 wt% cobalt. Each sample was dispersed in deionized water, and the viscosity of the resulting slurry was tested (rotation speed 60 r / min) at different solid phase contents. The results are as follows: Figure 8As shown, under the same solid content conditions, the viscosity of the slurry prepared from cobalt-coated tungsten carbide powder is significantly lower than that prepared from pure tungsten carbide powder and WC-Co mixed powder. This is because the uniform coating of the cobalt layer makes the chemical properties of the powder surface uniform, effectively weakening the mechanical interlocking and physical friction between WC particles, improving particle packing efficiency, and laying the foundation for achieving a direct-write slurry with high solid content and low viscosity.

[0073] Comparative Example 2

[0074] To screen for the optimal dispersant, cobalt-coated tungsten carbide powder prepared in Example 1 was used as the solid phase and dispersed in deionized water at a solid content of 90%. Ammonium citrate (AC), polyacrylic acid (PAA), and polyvinylpyrrolidone (PVP) were added at 0.2–1.2 wt%, respectively. The viscosity of the resulting slurry was tested (rotation speed 60 r / min), and the results are as follows: Figure 9 As shown, all three dispersants initially decrease and then increase the viscosity of the slurry. This is because the dispersants adsorb onto the particle surface, reducing interparticle friction through electrostatic repulsion or steric hindrance. Excessive dispersant can cause particle agglomeration, leading to a rebound in viscosity. Among them, 1.0 wt% ammonium citrate (AC) exhibits the best viscosity-reducing effect. Therefore, this invention selects AC as the core dispersant and combines it with polyethylene glycol (PEG) to form a composite additive.

[0075] Comparative Example 3

[0076] To determine the optimal sintering temperature, the green blanks printed in Example 4 were sintered at 1300℃, 1350℃, 1400℃, 1450℃, and 1500℃ for 2 hours, respectively. The density and Vickers hardness of the resulting WC-Co cemented carbide were then measured. The results are as follows: Figure 10 As shown, the alloy density and hardness first increase and then decrease with increasing sintering temperature, reaching a peak at 1450℃ (density ≥99%, hardness >1900HV). 30 At 1500℃, abnormal grain growth leads to a decrease in performance. Therefore, this invention determines 1450℃ as the optimal sintering temperature.

[0077] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a high-solids WC-Co water-based slurry for direct writing molding, characterized in that, Includes the following steps: (1) Preparation of cobalt-coated tungsten carbide powder: Cobalt chloride hexahydrate is dissolved in an ethanol solution, tungsten carbide powder is added, and mechanical stirring and ultrasonic treatment are performed in sequence to obtain a mixture; the mixture is thoroughly dried to obtain a composite powder; the composite powder is placed in a tube furnace and reduced in a hydrogen atmosphere; The reduced powder was taken out and ground to obtain uniformly dispersed cobalt-coated tungsten carbide powder; (2) Preparation of WC-Co water-based slurry: The cobalt-coated tungsten carbide powder obtained in step (1) is dispersed in an aqueous solution of additives to prepare a WC-Co water-based slurry with a solid content of 90wt%-93wt%; the aqueous solution of additives is a mixed aqueous solution of ammonium citrate and polyethylene glycol.

2. The method for preparing high-solids WC-Co water-based slurry for direct writing molding according to claim 1, characterized in that: In step (1), the mass percentage of tungsten carbide powder to cobalt chloride hexahydrate is 85.6%~49.8%:14.4%~50.2%.

3. The method for preparing high-solids WC-Co water-based slurry for direct writing molding according to claim 1, characterized in that: In step (1), the mechanical stirring time is 6~12h and the stirring speed is 300~500rpm, and the ultrasonic treatment frequency is 30~50kHz and the ultrasonic time is 10~30min.

4. The method for preparing high-solids WC-Co water-based slurry for direct writing molding according to claim 1, characterized in that: In step (1), the reduction temperature is 500~700℃, the reduction time is 2~5h, and the hydrogen flow rate is controlled at 150~200mL / min.

5. The method for preparing high-solids WC-Co water-based slurry for direct writing molding according to claim 1, characterized in that: In step (2), the mass ratio of ammonium citrate to polyethylene glycol in the additive aqueous solution is 1~5:1, and the total mass percentage of ammonium citrate and polyethylene glycol in WC-Co water-based slurry is 1~1.2wt%.

6. The method for preparing high-solids WC-Co water-based slurry for direct writing molding according to claim 1, characterized in that: In step (2), the cobalt-coated tungsten carbide powder is dispersed in an aqueous solution of additives at room temperature.

7. A high-solids WC-Co water-based slurry for direct writing molding, characterized in that: Prepared according to the preparation method described in any one of claims 1 to 6.

8. A WC-Co cemented carbide, characterized in that: The WC-Co water-based slurry as described in claim 7 is prepared by 3D printing and degreasing sintering.

9. A method for preparing the WC-Co cemented carbide according to claim 8, characterized in that: WC-Co water-based slurry was printed into shape using a direct-write 3D printer at room temperature to obtain a WC-Co composite material green body; the WC-Co composite material green body was then subjected to debinding and sintering treatments to obtain WC-Co cemented carbide.

10. The preparation method according to claim 9, characterized in that: The sintering temperature is 1450℃.

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