Spherical tungsten carbide compound, method for preparing the same, and use thereof

Abstract

The application belongs to the technical field of spherical tungsten carbide compound preparation, and particularly relates to a spherical tungsten carbide compound, a preparation method and application thereof, wherein the preparation method of the spherical tungsten carbide compound comprises the following steps: S1, obtaining raw materials, wherein the raw materials comprise 71wt%-76wt% tungsten carbide powder, 18wt%-23wt% tungsten powder and 5wt%-7wt% tungsten trioxide; S2, ball milling the raw materials to obtain a ball milling slurry; and S3, spray drying the ball milling slurry, and then high-temperature carbonizing at a temperature of 1600-1800 DEG C to obtain the spherical tungsten carbide compound. The spherical tungsten carbide compound is prepared by a powder metallurgy method, has high hardness, and has high loose bulk density after crushing and sieving, and a coating with high wear resistance can be prepared by laser cladding or plasma surfacing.

Description

Technical Field

[0001] This invention belongs to the field of spherical tungsten carbide preparation technology, specifically a spherical tungsten carbide, its preparation method, and its application. Background Technology

[0002] Laser cladding and plasma welding are important methods for surface strengthening technology. By cladding wear-resistant materials onto the surface of a substrate under the action of high-energy laser beams or plasma flames, the wear resistance and corrosion resistance of the workpiece are significantly improved. Tungsten carbide (WC) has become one of the preferred materials for reinforcing phases due to its excellent hardness (above HV2200) and high-temperature stability. Traditional tungsten carbide particles have irregular shapes, which easily leads to high porosity and uneven distribution of the cladding layer. Spherical tungsten carbide, with its good flowability, high bulk density (≥6.7g / cm³), and uniform distribution characteristics, has become a research hotspot and is widely used in energy drilling, aerospace, and machinery manufacturing. However, WC is prone to decomposition during high-temperature cladding (>1250℃ to form W2C), and spherical particles have poor wettability with the metal matrix. Therefore, process optimization or the addition of active elements (such as Co and Cr) is required to improve the bonding performance.

[0003] The preparation of spherical tungsten carbide mainly employs two methods: spray drying agglomeration granulation-sintering and sintering crushing high-temperature plasma spheroidization. The former involves spray granulation followed by high-temperature sintering (1400-1600℃) of the mixture to obtain spherical particles, but this method easily generates large internal pores. The latter utilizes plasma melting and sintering of irregular WC particles, forming spherical shapes based on surface tension, achieving a sphericity of up to 95%, but this method is costly and particle size control is difficult. Currently, this technology still faces challenges such as the contradiction between spheroidization rate and particle size (small particles are difficult to spheroidize, large particles are prone to hollowing, and particle size control is limited by the particle size of the front-end crushed powder), high-temperature oxidation (requiring inert gas protection), and high cost (30%-50% more expensive than irregular powders). Considering both production cost and efficiency, developing a spherical tungsten carbide-based material with small and few internal pores is particularly important. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a method for preparing spherical tungsten carbide compounds, comprising the following steps:

[0005] S1. Obtain raw materials, wherein the raw materials include 71wt%~76wt% tungsten carbide powder, 18wt%~23wt% tungsten powder and 5wt%~7wt% tungsten trioxide;

[0006] S2. The raw material is ball-milled to obtain a ball-milled slurry;

[0007] S3. Spray dry the ball mill slurry, and then perform high-temperature carbonization at 1600~1800℃ to obtain spherical tungsten carbide, wherein the high-temperature carbonization time is 70~110min.

[0008] In step S1, the tungsten carbide powder has a Fisher particle size of 2.0~2.5μm, a carbon content of 5.9wt%~6.3wt%, and a specific surface area of ​​3.0~4.0m². 2 / g.

[0009] In step S2, polyethylene glycol, defoamer, and water are added during ball milling. The amount of polyethylene glycol added is equivalent to 2 wt% of the raw material mass, the amount of defoamer added is equivalent to 0.1 wt% of the raw material mass, the mass ratio of the raw material to water is (4~5):1, and the ball milling time is 30~40 hours.

[0010] This also includes: S4, mechanically crushing and sieving the spherical tungsten carbide.

[0011] In step S4, the sieving process involves using an 80-mesh sieve to sieve the material and then collecting the material that passes through the sieve.

[0012] Furthermore, in step S3, a centrifugal spray drying device is used for spray drying, wherein the inlet air temperature of the drying tower is 150~180℃, the outlet air temperature is 110~120℃, the rotation speed of the atomizer is 2000~5000r / min, and the feed rate is 4.0~6.0kg / min.

[0013] To address the aforementioned technical problems, the present invention also provides a spherical tungsten carbide compound, which is prepared by the above-described method for preparing spherical tungsten carbide compounds.

[0014] The spherical tungsten carbide has a Vickers hardness of ≥2200HV0.1 and a total carbon content of 3.7wt%~4.2wt%.

[0015] The loose packing density of the spherical tungsten carbide is greater than or equal to 9.0 g / cm³. 3 .

[0016] To address the aforementioned technical problems, this invention also provides a method for applying spherical tungsten carbide, using the aforementioned spherical tungsten carbide and nickel-based self-fluxing alloy powder as raw materials, and performing laser cladding or plasma welding on a 45# carbon steel substrate to obtain a coating, wherein the mass fraction of the spherical tungsten carbide in the raw materials is 40wt%~60wt%;

[0017] Furthermore, the coating is prepared by mixing the spherical tungsten carbide of the present invention with a nickel-based self-fluxing alloy as a raw material. The mass fraction of the spherical tungsten carbide in the raw material is 40wt%~60wt%. If there is too much spherical tungsten carbide, it will result in too little nickel-based self-fluxing alloy as the binder phase, which will cause the coating to crack. If there is too little spherical tungsten carbide, it will result in poor wear resistance of the prepared coating.

[0018] This invention prepares spherical tungsten carbide using powder metallurgy, solving the problems of traditional processes involving high-temperature sintering, repeated mechanical crushing of block materials, repeated sieving, and then high-temperature spheroidization. The resulting material exhibits high hardness and high bulk density after crushing and sieving. Laser cladding or plasma welding can be used to prepare coatings with high wear resistance. During preparation, some WO3 is added to the raw materials to replace tungsten powder. Because WO3 is relatively brittle, its particle size is easily reduced after ball milling, allowing it to be uniformly dispersed in the powder. After high-temperature carbonization, it fills pores and effectively participates in the WC-W reaction to form W2C, which is beneficial for adjusting carbon content, reducing the amount of tungsten powder added, and lowering costs. Using WC as the main raw material facilitates the ball milling and dispersion of tungsten powder, the preparation of spherical powder, and increases the sintering density of the spherical powder. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0020] Figure 1 SEM image of the coating in Example 4 after abrasion resistance testing;

[0021] Figure 2 The image shows the SEM image of the coating in Comparative Example 8 after abrasion resistance testing.

[0022] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0023] The technical solutions described below in conjunction with the embodiments will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the 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.

[0024] This invention provides a method for preparing spherical tungsten carbide compounds, comprising the following steps:

[0025] S1. Obtain raw materials, wherein the raw materials include 71wt%~76wt% tungsten carbide powder, 18wt%~23wt% tungsten powder and 5wt%~7wt% tungsten trioxide;

[0026] This invention uses tungsten trioxide to replace part of the tungsten powder as a raw material. Due to the greater brittleness of tungsten trioxide, the particle size is finer and the dispersion is better during ball milling. After high-temperature carbonization, it can fill the pores and effectively participate in the WC-W reaction to form W2C, which is beneficial for adjusting the carbon content and reducing the amount of tungsten powder added, thus reducing costs. Secondly, the oxygen in tungsten trioxide can also absorb the carbon from the cracking of the forming agent, producing carbon monoxide volatilization, preventing the accumulation of free carbon from the cracking of organic matter on the material surface and the problem of uneven carbon content. The Fisher particle size of tungsten trioxide is usually less than 25 μm, and this invention does not limit the Fisher particle size of tungsten trioxide.

[0027] This invention uses tungsten carbide as the main raw material. Because tungsten powder has a certain degree of ductility, it is easy to flatten during the ball milling process, resulting in a plate-like structure with a large particle size. Hard tungsten carbide can achieve the effect of shearing and dispersing tungsten powder during ball milling, and it also has the effect of dispersing tungsten trioxide powder during ball milling. This is beneficial to making the particle size of each component finer and more uniform, thereby making the prepared powder more spherical and having fewer internal pores. Since each component is small and uniformly distributed, it can improve the reaction activity, reduce the internal resistance of the particles, and achieve the effect of increasing the sintering density of the spherical powder.

[0028] S2. The raw material is ball-milled to obtain a ball-milled slurry;

[0029] S3. Spray dry the ball mill slurry, and then perform high-temperature carbonization at 1600~1800℃ to obtain spherical tungsten carbide, wherein the high-temperature carbonization time is 70~110min.

[0030] This invention employs a centrifugal spray drying device to spray dry ball mill slurry. Centrifugal spray drying granulation is a drying technology that disperses liquid materials into tiny droplets through a high-speed rotating atomizer and rapidly evaporates moisture using hot air, thereby obtaining dry powder or granules. Its core process is as follows: the liquid material is fed into a high-speed rotating centrifugal atomizing disc, where it forms fine droplets under centrifugal force; after the droplets come into contact with hot air, due to the principle that the surface energy of the droplets is minimized after heating, the droplets will shrink into a spherical shape and rapidly evaporate moisture, obtaining dried powder. This technology has the characteristics of fast drying speed, uniform particle size, and good flowability.

[0031] The spherical tungsten carbide obtained in this invention is a compound similar to cast tungsten carbide in the prior art, and it is a eutectic compound formed by WC and W2C.

[0032] An embodiment of the present invention further includes step S4, mechanically crushing and sieving the spherical tungsten carbide, wherein different particle sizes can be sieved according to actual needs to meet the requirements of different working conditions.

[0033] In the embodiments of the present invention, centrifugal spray drying equipment is used for spray drying, wherein the outlet air temperature of the drying tower is 120°C, the inlet air temperature is 160°C, the atomizer speed is 3000 r / min, and the feed rate is 5.0 kg / min.

[0034] Example 1

[0035] Using tungsten carbide powder with a Fisher particle size of 2.0 μm, a carbon content of 6.0 wt%, and a specific surface area of ​​3.0 m², the method was employed. 2 The raw materials are tungsten powder of / g and tungsten trioxide with a Fisher particle size of 20μm, with a mass ratio of 71.6:22.8:5.6;

[0036] Add polyethylene glycol (PEG) at a mass equivalent of 2 wt% of the raw material, polydimethylsiloxane at a mass equivalent of 0.1 wt% of the raw material, and water. The mass ratio of raw material to water is 4:1. Ball mill for 40 hours to obtain ball mill slurry.

[0037] The spherical tungsten carbide was obtained by spray drying the spherical slurry and then carbonizing it at 1600℃ for 100 min.

[0038] Spherical tungsten carbide compounds were mechanically crushed and passed through an 80-mesh sieve. The undersize material was collected to obtain the final product, which had a bulk density of 9.0 g / cm³. 3 It has a Vickers hardness of 2200 HV0.1 and a total carbon content of 3.91 wt%.

[0039] Example 2

[0040] Using tungsten carbide powder with a Fisher particle size of 2.5 μm, a carbon content of 6.15 wt%, and a specific surface area of ​​4.0 m², the method was employed. 2 The raw materials are tungsten powder of / g and tungsten trioxide with a Fisher particle size of 25μm, with a mass ratio of 74.3:18.8:6.9;

[0041] Add polyethylene glycol (PEG) at a mass equivalent of 2 wt% of the raw material, polydimethylsiloxane at a mass equivalent of 0.1 wt% of the raw material, and water. The mass ratio of raw material to water is 5:1. Ball mill for 30 hours to obtain ball mill slurry.

[0042] The spherical tungsten carbide was obtained by spray drying the spherical slurry and then carbonizing it at 1800℃ for 70 min.

[0043] Spherical tungsten carbide compounds were mechanically crushed and passed through an 80-mesh sieve. The undersize material was collected to obtain the final product, which had a bulk density of 9.8 g / cm³. 3The Vickers hardness is 2306 HV0.1, and the total carbon content is 3.82 wt%.

[0044] Example 3

[0045] Using tungsten carbide powder with a Fisher particle size of 2.2 μm, a carbon content of 6.3 wt%, and a specific surface area of ​​4.0 m², the method was employed. 2 The raw materials are tungsten powder of / g and tungsten trioxide with a Fisher particle size of 23μm, with a mass ratio of 75.9:18.8:5.3;

[0046] Add polyethylene glycol (PEG) at a mass equivalent of 2 wt% of the raw material, polydimethylsiloxane at a mass equivalent of 0.1 wt% of the raw material, and water. The mass ratio of raw material to water is 5:1. Ball mill for 30 hours to obtain ball mill slurry.

[0047] The spherical tungsten carbide was obtained by spray drying the spherical slurry and then carbonizing it at 1700℃ for 85 min.

[0048] Spherical tungsten carbide compounds were mechanically crushed and passed through an 80-mesh sieve. The undersize material was collected to obtain the final product, which had a bulk density of 9.5 g / cm³. 3 It has a Vickers hardness of 2356 HV0.1 and a total carbon content of 3.95 wt%.

[0049] Example 4

[0050] The spherical tungsten carbide obtained in Example 3 was used to prepare the coating. 60 wt% of the spherical tungsten carbide and 40 wt% of the nickel-based self-fluxing alloy powder were mechanically mixed as raw materials and laser cladding was performed on a 45# carbon steel substrate to prepare the coating. The wear resistance of the coating was then tested.

[0051] Please see Figure 1 , Figure 1 The image shows a SEM image of the coating in Example 4 after wear resistance testing. It can be seen from the image that wear mainly occurs in the nickel-based self-fluxing alloy, and the spherical tungsten carbide particles play an important role in wear resistance.

[0052] Comparative Example 1

[0053] Unlike Example 3, tungsten powder with a Fisher particle size of 2.2 μm was used as the raw material;

[0054] The final product has a bulk density of 6.5 g / cm³. 3 It has a Vickers hardness of 1760 HV0.1 and a total carbon content of 3.93 wt%.

[0055] Comparative Example 2

[0056] Unlike Example 3, the spherical tungsten carbide was spray-dried and then carbonized at 1500°C for 85 min.

[0057] The final product has a bulk density of 6.1 g / cm³. 3 The Vickers hardness is 1677 HV0.1, and the total carbon content is 4.05 wt%.

[0058] Comparative Example 3

[0059] Unlike Example 3, tungsten carbide powder with a Fisher particle size of 2.2 μm and a carbon content of 3.95 wt% was used as raw material. The resulting tungsten carbide particles had open pores between them. Under the same carbonization conditions, shrinkage and densification could not be completed, resulting in a large number of pores and poor compactness.

[0060] The final product has a bulk density of 8.3 g / cm³. 3 The Vickers hardness is 1850 HV0.1, and the total carbon content is 4.00 wt%.

[0061] Comparative Example 4

[0062] Unlike Example 3, the tungsten carbide powder in the raw material has a Fisher particle size of 5.5 μm;

[0063] The final product has a bulk density of 8.7 g / cm³. 3 It has a Vickers hardness of 2100 HV0.1 and a total carbon content of 3.95 wt%.

[0064] Comparative Example 5

[0065] Unlike Example 3, the spherical tungsten carbide was spray-dried and then carbonized at 2000°C for 85 minutes to obtain spherical tungsten carbide. Due to the excessively high temperature, the spherical particles melted and agglomerated severely, making crushing more difficult. After violent crushing and sieving, a large number of non-spherical particles were found.

[0066] The final product has a bulk density of 8.5 g / cm³. 3 It has a Vickers hardness of 2600 HV0.1 and a total carbon content of 3.98 wt%.

[0067] Comparative Example 6

[0068] Unlike Example 3, tungsten carbide powder with a Fisher particle size of 2.2 μm, a carbon content of 6.3 wt%, and a specific surface area of ​​4.0 m² was used. 2 / g of tungsten powder and tungsten trioxide with a Fisher particle size of 23μm were used as raw materials, with a mass ratio of 80:14:6;

[0069] The final product has a bulk density of 9.8 g / cm³. 3 The Vickers hardness is 2000 HV0.1, and the total carbon content is 4.6 wt%.

[0070] Comparative Example 7

[0071] Unlike Example 3, tungsten carbide powder with a Fisher particle size of 2.2 μm, a carbon content of 6.3 wt%, and a specific surface area of ​​4.0 m² was used. 2 / g of tungsten powder and tungsten trioxide with a Fisher particle size of 23μm were used as raw materials, with a mass ratio of 70:20:10;

[0072] The final product has a bulk density of 8.5 g / cm³. 3 The Vickers hardness is 2450 HV0.1, and the total carbon content is 3.35 wt%.

[0073] Comparative Example 8

[0074] The difference from Example 4 is that cast tungsten carbide prepared by plasma spheroidization in the prior art is used as the raw material for laser cladding; and the wear resistance of the coating is tested.

[0075] Please see Figure 2 , Figure 2 The image shows a SEM image of the coating in Comparative Example 8 after wear resistance testing. It can be seen from the image that some spherical tungsten carbide was worn away, and the wear of the bonded nickel-based alloy phase was more severe.

[0076] Please refer to Table 1, which shows the results of coating hardness, cavitation rate, erosion rate and abrasive wear weight loss tests for Example 4 and Comparative Example 8.

[0077] Table 1

[0078]

[0079] Abrasion loss test parameters: 1.5kg of 40~70 mesh quartz sand and 1kg of water, 1500r, 100N;

[0080] The cavitation erosion test shall be conducted in accordance with the standard GB / T 6383-2024 "Cavitation Erosion Test Method";

[0081] Wear loss weight: ASTM G105-20 "Standard Test Method for Wear Testing of Wet Sand / Rubber Wheels";

[0082] The mortar erosion test parameters are as follows: the mortar medium used is 1.5 kg of silica sand (325 mesh) and 15 kg of water, the erosion distance is 25 mm, the erosion angle is 30° and 90°, and the erosion lasts for 6 hours. The mass of the sample before and after erosion is measured using an electronic balance with an accuracy of 0.0001 g. The total mass loss is divided by the total erosion time to obtain the erosion rate (g / h).

[0083] This invention prepares spherical tungsten carbide using powder metallurgy, replacing traditional sintering, crushing, and sieving processes. It exhibits high hardness and high bulk density after crushing and sieving. Laser cladding or plasma welding can be used to prepare coatings with high wear resistance. During preparation, some WO3 is added to the raw materials to replace tungsten powder. Because WO3 is relatively brittle, its particle size is easily reduced after ball milling, allowing it to be uniformly dispersed in the powder. After high-temperature carbonization, it fills pores and effectively participates in the WC-W reaction to form W2C. This facilitates carbon content adjustment, reduces the amount of tungsten powder added, and lowers costs. Using WC as the main raw material is beneficial for ball milling and dispersing tungsten powder, preparing spherical powders, and increasing the sintering density of the spherical powders.

[0084] The above description is only a preferred embodiment of the present invention and does not limit the patent scope of the present invention. All equivalent structural transformations made using the contents of the present invention under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A method for producing a spherical tungsten carbide compound, characterized by, The method comprises the following steps: S1, obtaining raw materials, the raw materials comprising 71wt%-76wt% tungsten carbide powder, 18wt%-23wt% tungsten powder and 5wt%-7wt% tungsten trioxide; S2, ball milling the raw materials to obtain a ball milling slurry; S3, spray drying the ball milling slurry, and then high-temperature carbonizing the spray-dried ball milling slurry at a temperature of 1600-1800℃ to obtain a spherical tungsten carbide compound, the high-temperature carbonizing being performed for 70-110min.

2. The method of claim 1, wherein the tungsten carbide compound is prepared by the steps of: In the step S1, the Fe's particle size of the tungsten carbide powder is 2.0-2.5 μm, the carbon content of the tungsten carbide powder is 5.9wt%-6.3wt%, and the specific surface area of the tungsten powder is 3.0-4.0 m 2 / g. ​ 3. The method for preparing a spherical tungsten carbide according to claim 1, characterized in that, In the step S2, polyethylene glycol, a defoaming agent and water are added during the ball milling, wherein the polyethylene glycol is added in an amount of 2wt% of the mass of the raw materials, the defoaming agent is added in an amount of 0.1wt% of the mass of the raw materials, the mass ratio of the raw materials to water is (4-5):1, and the ball milling is performed for 30-40h.

4. The method for preparing a spherical tungsten carbide according to claim 1, characterized in that, Further comprising: S4, mechanically crushing and sieving the spherical tungsten carbide compound.

5. The method for preparing a spherical tungsten carbide according to claim 4, characterized in that, In the step S4, the sieving is performed using a 80-mesh sieve and the undersize is taken.

6. A spherical tungsten carbide compound, characterized by, The spherical tungsten carbide compound is prepared by the method for preparing a spherical tungsten carbide compound according to any one of claims 1-5.

7. A spherical tungsten carbide compound according to claim 6, wherein The Vickers hardness of the spherical tungsten carbide compound is greater than or equal to 2200HV0.1, and the total carbon content of the spherical tungsten carbide compound is 3.7wt%-4.2wt%.

8. A spherical tungsten carbide compound according to claim 6, wherein The bulk density of the spherical tungsten carbide compound is greater than or equal to 9.0 g / cm 3 .

9. A method of using a spherical tungsten carbide compound, characterized by, The spherical tungsten carbide compound and a nickel-based self-fluxing alloy powder according to claim 6 are used as raw materials to perform laser cladding or plasma surfacing on a 45# carbon steel substrate to obtain a coating, wherein the mass fraction of the spherical tungsten carbide compound in the raw materials is 40wt%-60wt%.

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