Plate-shaped ultra-coarse tungsten carbide and preparation method thereof

Abstract

The present invention belongs to the technical field of powder metallurgy, and specifically relates to a plate-like ultra-coarse tungsten carbide and a preparation method thereof, comprising: S1, adding graphite particles into a container, adding carbon black on the graphite particles, adding plate-like WO3 on the carbon black, and adding carbon black on the plate-like WO3; S2, placing the container in a furnace for segmented sintering, and then cooling the furnace to obtain a sintered product; S3, pouring the sintered product into pure water, standing and stratifying to remove carbon black and graphite particles, and filtering to obtain a sample; S4, sintering the sample for a second time, and then cooling the furnace to obtain plate-like ultra-coarse tungsten carbide, wherein the plate-like ultra-coarse tungsten carbide has an aspect ratio of ≥5:1, an average Fisher particle size ≥35 μm, and a combined carbon content of ≥99.20wt%.

Description

Technical Field

[0001] The invention belongs to the technical field of powder metallurgy, and specifically relates to plate-shaped ultra-coarse tungsten carbide and a preparation method thereof. Background Art

[0002] Tungsten carbide (WC), the core hard phase of cemented carbide, has a crucial influence on its morphology and structure in terms of its properties. Currently, industrially produced tungsten carbide powders are primarily spherical or equiaxed. These particles easily form a uniform microstructure during sintering. However, in certain specialized applications, such as high-toughness, high-wear-resistance, or directionally strengthened cemented carbide products, the limitations of spherical tungsten carbide are becoming increasingly apparent.

[0003] Studies have shown that plate-like tungsten carbide can optimize alloy properties through unique morphological effects in cemented carbides. The plate-like crystals of plate-like tungsten carbide have a high aspect ratio and a specific crystal plane orientation, which can form a staggered structure or directional arrangement during the sintering process, thereby significantly improving the fracture toughness, impact resistance and wear resistance of the alloy. In addition, plate-like tungsten carbide can also inhibit crack propagation through mechanisms such as crack deflection and bridging, further optimizing the mechanical properties of the material. However, existing tungsten carbide preparation technologies (such as direct carburization, tungsten oxide reduction carburization, etc.) are usually difficult to controllably synthesize plate-like tungsten carbide with high combined carbon and high crystallinity, and the product morphology is uneven and the process conditions are harsh, which restricts its industrial application.

[0004] Currently, a few studies have attempted to prepare plate-like tungsten carbide using template methods, molten salt methods, or methods that add morphology control agents. However, these methods often have problems such as complex processes, high costs, or the introduction of impurities. For example, some scholars have used high-temperature molten salt methods to prepare plate-like tungsten carbide, but the product requires complex post-processing to remove salt residues. Other studies have promoted plate-like growth by adding metal catalysts such as cobalt or nickel, but residual metals may affect the final alloy properties. Therefore, developing a method that is simple in process, cost-controlled, and capable of mass-producing high-purity plate-like tungsten carbide is of great significance to promoting the development of high-performance cemented carbides.

[0005] In summary, the existing technology has not yet solved the problem of controllable preparation of plate-like tungsten carbide. It is urgent to invent a method for preparing plate-like tungsten carbide that is efficient, stable and suitable for industrial production to meet the demand for high performance of cemented carbide. Summary of the Invention

[0006] In order to solve the problems existing in the prior art, the main purpose of the present invention is to provide a plate-shaped ultra-coarse tungsten carbide and a preparation method thereof.

[0007] According to the first aspect of the present invention, the present invention provides the following technical solutions:

[0008] A method for preparing plate-shaped ultra-coarse tungsten carbide comprises the following steps:

[0009] S1. Add graphite particles into a container, add carbon black onto the graphite particles, add plate-like WO3 onto the carbon black, and add carbon black onto the plate-like WO3;

[0010] S2, placing the container in a furnace for staged sintering, and then cooling the furnace to obtain a sintered product;

[0011] S3. Pour the sintered product into pure water and allow to stand for stratification to remove carbon black and graphite particles, and filter to obtain a sample;

[0012] S4. The sample is subjected to secondary sintering and then cooled in the furnace to obtain plate-like ultra-coarse tungsten carbide.

[0013] According to the second aspect of the present invention, the present invention provides the following technical solutions:

[0014] A plate-shaped ultra-coarse tungsten carbide is prepared by the above-mentioned preparation method of plate-shaped ultra-coarse tungsten carbide, wherein the plate-shaped ultra-coarse tungsten carbide has an aspect ratio of ≥5:1, an average Fisher particle size of ≥35 μm, and a combined carbon content of ≥99.20wt%.

[0015] The beneficial effects of the present invention are as follows:

[0016] The present invention provides a plate-like ultra-coarse tungsten carbide and a preparation method thereof, comprising: S1, adding graphite particles into a container, adding carbon black on the graphite particles, adding plate-like WO3 on the carbon black, and adding carbon black on the plate-like WO3; S2, placing the container in a furnace for segmented sintering, and then cooling the furnace to obtain a sintered product; S3, pouring the sintered product into pure water, standing and stratifying to remove carbon black and graphite particles, and filtering to obtain a sample; S4, sintering the sample for a second time, and then cooling the furnace to obtain plate-like ultra-coarse tungsten carbide, wherein the plate-like ultra-coarse tungsten carbide has an aspect ratio of ≥5:1, an average Fisher particle size ≥35 μm, and a combined carbon content of ≥99.20 wt%. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0018] Figure 1 This is an SEM image of the plate-like WO3 used in Example 1 of the present invention;

[0019] Figure 2 This is a SEM image of the plate-like ultra-coarse tungsten carbide prepared in Example 1 of the present invention;

[0020] Figure 3 This is the XRD pattern of the plate-like ultra-coarse tungsten carbide prepared in Example 1 of the present invention;

[0021] Figure 4 This is a SEM image of WO3 used in Comparative Example 1 of the present invention;

[0022] Figure 5 This is a SEM image of tungsten carbide prepared in Comparative Example 1 of the present invention;

[0023] Figure 6 This is the XRD pattern of tungsten carbide prepared in Comparative Example 5 of the present invention.

[0024] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings and in conjunction with the embodiments. DETAILED DESCRIPTION

[0025] The following will be a clear and complete description of the technical solutions in the embodiments. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0026] According to the first aspect of the present invention, the present invention provides the following technical solutions:

[0027] A method for preparing plate-shaped ultra-coarse tungsten carbide comprises the following steps:

[0028] S1. Add graphite particles into a container, add carbon black onto the graphite particles, add plate-like WO3 onto the carbon black, and add carbon black onto the plate-like WO3;

[0029] S2, placing the container in a furnace for staged sintering, and then cooling the furnace to obtain a sintered product;

[0030] S3. Pour the sintered product into pure water and allow to stand for stratification to remove carbon black and graphite particles, and filter to obtain a sample;

[0031] S4. The sample is subjected to secondary sintering and then cooled in the furnace to obtain plate-like ultra-coarse tungsten carbide.

[0032] The present invention selects plate-like tungsten oxide raw materials to provide a raw material basis for plate-like tungsten carbide; the present invention prepares completely carbonized tungsten carbide through carbon enrichment and specific process sintering, and then coordinated secondary sintering; the present invention fully utilizes the characteristics of high density difference and cleverly separates the materials; the present invention can be produced in traditional tungsten carbide production equipment and is easy to industrialize.

[0033] Preferably, in step S1, the container is a graphite boat; graphite particles with a thickness of 3-5 mm are added to the graphite boat, carbon black with a thickness of 5-10 mm is added to the graphite particles, plate-shaped WO3 with a thickness of ≤5 mm is added to the carbon black, carbon black with a thickness of 10-15 mm is added to the plate-shaped WO3, and the container is sealed with a graphite lid with holes. Specifically, the thickness of the graphite particles added to the graphite boat can be, for example, any one of 3 mm, 3.5 mm, 4 mm, 4.5 mm, and 5 mm, or a range between any two of them; the thickness of the carbon black added to the graphite particles can be, for example, any one of 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, and 10 mm, or a range between any two of them; the thickness of the plate-like WO3 added to the carbon black can be, for example, any one of 1 mm, 2 mm, 3 mm, 4 mm, and 5 mm, or a range between any two of them; the thickness of the carbon black added to the plate-like WO3 is any one of 10 mm, 11 mm, 12 mm, 13 mm, 14 mm, and 15 mm, or a range between any two of them.

[0034] Preferably, in step S1, the present invention selects plate-shaped tungsten oxide raw material to provide a raw material basis for plate-shaped tungsten carbide; the aspect ratio of the plate-shaped WO3 is ≥5:1.

[0035] Preferably, in step S2, segmented sintering is performed in a medium frequency sintering furnace, and the segmented sintering process is: heating to 600-730°C at a heating rate of 50°C / min, keeping warm for 30 minutes, then heating to 1200-1320°C at a heating rate of 10°C / min, keeping warm for 120 minutes, then heating to 2300-2400°C at a heating rate of 50°C / min, and keeping warm for 200-320 minutes.

[0036] Preferably, in step S3, the present invention fully utilizes the characteristics of high density difference to skillfully separate the materials; and ultrasonic treatment is performed during the static stratification, and the static stratification time is 10-15 minutes. Specifically, the static stratification time can be, for example, any one of 10 minutes, 11 minutes, 12 minutes, 13 minutes, 14 minutes, and 15 minutes, or a range between any two thereof.

[0037] Preferably, in step S4, the sample is placed in a tube furnace using a graphite boat for secondary sintering, wherein the hydrogen flow rate is 120-180 L / h, the sintering temperature is 1300-1360° C., and the sintering time is 120-170 min. Specifically, the hydrogen flow rate can be, for example, any one of 120 L / h, 130 L / h, 140 L / h, 150 L / h, 160 L / h, 170 L / h, and 180 L / h, or a range between any two thereof; the sintering temperature can be, for example, any one of 1300° C., 1310° C., 1320° C., 1330° C., 1340° C., 1350° C., and 1360° C., or a range between any two thereof; and the sintering time can be, for example, any one of 120 min, 130 min, 140 min, 150 min, 160 min, and 170 min, or a range between any two thereof.

[0038] According to the second aspect of the present invention, the present invention provides the following technical solutions:

[0039] A plate-like ultra-coarse tungsten carbide is prepared using the above-mentioned method for preparing plate-like ultra-coarse tungsten carbide. The plate-like ultra-coarse tungsten carbide has an aspect ratio of ≥5:1, an average Fisher grain size of ≥35 μm, and a combined carbon content of ≥99.20wt%. Due to its coarse grains, ultra-coarse tungsten carbide is difficult to completely carburize, resulting in a tendency for the outer layer of the grain to be tungsten carbide and the inner layer to be incompletely carburized, resulting in ditungsten carbide. At the same total carbon content, a high free carbon content and incomplete grain carburization may exist. Combined carbon is used to characterize the degree of carburization. The total carbon and free carbon of the tungsten carbide powder are detected and then calculated from the total carbon and free carbon to obtain the combined carbon (total carbon - free carbon = combined carbon).

[0040] The technical solution of the present invention is further described below with reference to specific embodiments.

[0041] Example 1

[0042] A method for preparing plate-shaped ultra-coarse tungsten carbide comprises the following steps:

[0043] S1. Add 5mm thick graphite particles to a graphite boat, add 10mm thick carbon black on the graphite particles, add 5mm thick plate-shaped WO3 on the carbon black, add 15mm thick carbon black on the plate-shaped WO3, and cover it with a graphite lid with holes; the aspect ratio of the plate-shaped WO3 is greater than 5:1 (such as Figure 1 shown);

[0044] S2. Place the graphite boat in a medium frequency sintering furnace and perform segmented sintering in the medium frequency sintering furnace. The segmented sintering process is as follows: heat up to 730°C at a heating rate of 50°C / min, keep warm for 30 minutes, then heat up to 1200°C at a heating rate of 10°C / min, keep warm for 120 minutes, then heat up to 2400°C at a heating rate of 50°C / min, keep warm for 200 minutes;

[0045] S3. Pour the sintered product into pure water and allow to stand for stratification to remove carbon black and graphite particles. Perform ultrasonic treatment during the stratification. The stratification time is 15 minutes. Filter to obtain a sample.

[0046] S4. The sample was placed in a tubular furnace using a graphite boat for secondary sintering, with a hydrogen flow rate of 150 L / h, a sintering temperature of 1300°C, and a sintering time of 120 min; then the sample was cooled in the furnace to obtain plate-like ultra-coarse tungsten carbide.

[0047] The SEM and XRD patterns of the plate-like ultra-coarse tungsten carbide obtained in this embodiment are shown in Figures 1 and 2. Figure 2 and Figure 3 As shown, its aspect ratio is greater than 5:1, the average Fisher particle size is 37.9 μm, and the proportion of combined carbon is 99.35 wt%.

[0048] Example 2

[0049] A method for preparing plate-shaped ultra-coarse tungsten carbide comprises the following steps:

[0050] S1. Add 3 mm thick graphite particles into a graphite boat, add 5 mm thick carbon black on the graphite particles, add 3 mm thick plate-shaped WO3 on the carbon black, add 10 mm thick carbon black on the plate-shaped WO3, and cover the boat with a perforated graphite lid; the aspect ratio of the plate-shaped WO3 is greater than 5:1;

[0051] S2. Place the graphite boat in a medium frequency sintering furnace and perform segmented sintering in the medium frequency sintering furnace. The segmented sintering process is as follows: heat up to 600°C at a heating rate of 50°C / min, keep warm for 30 minutes, then heat up to 1200°C at a heating rate of 10°C / min, keep warm for 120 minutes, then heat up to 2300°C at a heating rate of 50°C / min, keep warm for 320 minutes;

[0052] S3. Pour the sintered product into pure water and allow to stand for stratification to remove carbon black and graphite particles. Perform ultrasonic treatment during the stratification. The stratification time is 15 minutes. Filter to obtain a sample.

[0053] S4. The sample was placed in a tube furnace using a graphite boat for secondary sintering, with a hydrogen flow rate of 180 L / h, a sintering temperature of 1360°C, and a sintering time of 170 min; then the sample was cooled in the furnace to obtain plate-like ultra-coarse tungsten carbide.

[0054] The plate-like ultra-coarse tungsten carbide obtained in this embodiment has an aspect ratio greater than 5:1, an average Fisher grain size of 39.3 μm, and a combined carbon content of 99.29 wt %.

[0055] Example 3

[0056] A method for preparing plate-shaped ultra-coarse tungsten carbide comprises the following steps:

[0057] S1. Add 4 mm thick graphite particles to a graphite boat, add 7 mm thick carbon black on the graphite particles, add 4 mm thick plate-shaped WO3 on the carbon black, add 13 mm thick carbon black on the plate-shaped WO3, and cover the boat with a perforated graphite lid; the aspect ratio of the plate-shaped WO3 is greater than 5:1;

[0058] S2. Place the graphite boat in a medium frequency sintering furnace and perform segmented sintering in the medium frequency sintering furnace. The segmented sintering process is as follows: heat up to 680°C at a heating rate of 50°C / min, keep warm for 30 minutes, then heat up to 1280°C at a heating rate of 10°C / min, keep warm for 120 minutes, then heat up to 2350°C at a heating rate of 50°C / min, keep warm for 260 minutes;

[0059] S3. Pour the sintered product into pure water and allow to stand for stratification to remove carbon black and graphite particles. Perform ultrasonic treatment during the stratification. The stratification time is 13 minutes. Filter to obtain a sample.

[0060] S4. The sample was placed in a graphite boat in a tubular furnace for secondary sintering, with a hydrogen flow rate of 160 L / h, a sintering temperature of 1340°C, and a sintering time of 150 min; then the sample was cooled in the furnace to obtain plate-like ultra-coarse tungsten carbide.

[0061] The plate-like ultra-coarse tungsten carbide obtained in this embodiment has an aspect ratio greater than 5:1, an average Fisher grain size of 37.26 μm, and a combined carbon content of 99.34 wt %.

[0062] Comparative Example 1

[0063] The difference from Example 1 is that in step S1, ordinary WO3 (such as Figure 4 shown) instead of plate-like WO3.

[0064] The SEM image of the tungsten carbide obtained in this comparative example is as follows Figure 5 As shown, it has no plate-like crystal structure.

[0065] Comparative Example 2

[0066] The difference from Example 1 is that the plate-like WO3 is subjected to high-temperature reduction to obtain tungsten powder, the reduction temperature is 1300°C, and the obtained tungsten powder is added with carbon black, and the carbon content is added in an amount of 6.18wt% for plow mixing to obtain a tungsten + carbon mixture, wherein the fly cutter speed is 1500r / min, the plow speed is 40r / min, and the mixing is 60min; the tungsten + carbon mixture is subjected to medium frequency carbonization, the carbonization temperature is 2400°C, and the heat preservation is carried out for 200min.

[0067] The tungsten carbide obtained in this comparative example does not have a plate-like crystal structure.

[0068] Comparative Example 3

[0069] The difference from Example 1 is that no graphite particles are used in step S1.

[0070] The tungsten carbide obtained in this comparative example has an aspect ratio greater than 5:1, an average Fisher grain size of 35.19 μm, and a combined carbon content of 92.27 wt %.

[0071] Comparative Example 4

[0072] The difference from Example 1 is that step S4 is not performed.

[0073] The tungsten carbide obtained in this comparative example has an aspect ratio greater than 5:1, an average Fisher grain size of 31.69 μm, and a combined carbon content of 95.74 wt %.

[0074] Comparative Example 5

[0075] The difference from Example 1 is that, in step S1, a graphite cover without holes is used for sealing.

[0076] The XRD pattern of tungsten carbide obtained in this comparative example is as follows: Figure 6 As shown, tungsten carbide contains ditungsten carbide and tungsten, and the combined carbon accounts for 74.92wt%.

[0077] 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 by using the contents of the present invention specification under the inventive concept of the present invention, or direct / indirect application in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A method for preparing plate-shaped ultra-coarse tungsten carbide, characterized in that: The steps include: S1. Add graphite particles to a container, add carbon black on the graphite particles, add plate-like WO3 on the carbon black, and add carbon black on the plate-like WO3; the container is a graphite boat; add graphite particles with a thickness of 3-5 mm to the graphite boat, add carbon black with a thickness of 5-10 mm on the graphite particles, add plate-like WO3 with a thickness of ≤5 mm on the carbon black, add carbon black with a thickness of 10-15 mm on the plate-like WO3, and seal the container with a graphite lid with holes; S2, placing the container in a furnace for staged sintering, and then cooling the furnace to obtain a sintered product; The staged sintering process is as follows: heating to 600-730°C at a heating rate of 50°C / min, holding for 30 minutes, then heating to 1200-1320°C at a heating rate of 10°C / min, holding for 120 minutes, then heating to 2300-2400°C at a heating rate of 50°C / min, holding for 200-320 minutes; S3. Pour the sintered product into pure water and allow to stand for stratification to remove carbon black and graphite particles, and filter to obtain a sample; S4. The sample is placed in a tubular furnace using a graphite boat for secondary sintering, wherein the hydrogen flow rate is 120-180 L / h, the sintering temperature is 1300-1360°C, and the sintering time is 120-170 min. After cooling in the furnace, plate-shaped ultra-coarse tungsten carbide is obtained.

2. The method for preparing plate-shaped ultra-coarse tungsten carbide according to claim 1, characterized in that: In the step S1, the aspect ratio of the plate-shaped WO3 is ≥5:

1.

3. The method for preparing plate-shaped ultra-coarse tungsten carbide according to claim 1, characterized in that: In step S3, ultrasonic treatment is performed during the standing and stratification, and the standing and stratification time is 10-15 minutes.

4. A plate-shaped ultra-coarse tungsten carbide, characterized in that: The plate-shaped ultra-coarse tungsten carbide is prepared by the preparation method of any one of claims 1 to 3.

5. The plate-shaped ultra-coarse tungsten carbide according to claim 4, characterized in that: The plate-shaped ultra-coarse tungsten carbide has an aspect ratio of ≥5:1, an average Fisher grain size of ≥35 μm, and a combined carbon content of ≥99.20 wt%.

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