A spherical WC grain high-strength super-coarse alloy and its preparation method

Abstract

This invention discloses a high-strength ultra-coarse alloy with near-spherical WC grains and its preparation method, relating to the field of cemented carbide technology. Specifically, the method uses tungsten carbide powder with a Fisher particle size of 20-40 μm, tungsten powder with a particle size of 0.5-0.6 μm, and spherical cobalt powder with a Co content ≥99.5% as raw materials. A forming agent and a dispersing medium are then added, and the mixture is ball-milled to obtain a mixed slurry. The mixed slurry is then sequentially dried, pressed, and sintered to obtain the final product. This invention reduces the total carbon content of the alloy by using ultra-fine tungsten powder during the ball-milling mixing stage. The tungsten powder dissolves in the cobalt phase, inhibiting the dissolution and growth of tungsten carbide powder during alloy sintering, maintaining the near-spherical shape of the grains after ball milling. This produces a near-spherical WC-Co ultra-coarse cemented carbide with low magnetic saturation and near-spherical WC grains. While maintaining ultra-coarse grains, the alloy also possesses high bending strength and good toughness due to the near-spherical grains.

Description

Technical Field

[0001] This invention relates to the field of cemented carbide technology, specifically to a high-strength ultra-coarse alloy with spherical WC grains and its preparation method. Background Technology

[0002] WC-Co cemented carbide is widely used due to its excellent properties of high hardness and high wear resistance. However, while lower cobalt content in the alloy increases hardness and wear resistance, it significantly reduces toughness, failing to achieve the dual high hardness and high toughness of a cemented carbide. Balancing hardness and toughness in cemented carbides has been a key research focus for researchers both domestically and internationally, depending on specific application conditions. Low-cobalt ultra-coarse-grained cemented carbides have been a research priority, but they have not effectively resolved the contradiction between toughness and hardness. WC-Co cemented carbide is produced through a liquid-phase sintering process. During liquid-phase sintering, the dissolution process leads to WC grain growth and the formation of low-energy prismatic interfaces with sharp edges. Under load, these sharp edges concentrate tensile stress, promoting crack initiation and propagation. A more "rounded" WC grain structure in the sintered alloy reduces crack sensitivity (especially cracks caused by thermal shock), thus obtaining a material with better toughness.

[0003] A search revealed that Chinese patent CN103602870A discloses a method for preparing a cemented carbide with near-spherical tungsten carbide grains containing a cubic phase. The method uses short-time ball milling to achieve a near-spherical hard phase. However, it was found that the excessively short ball milling time resulted in large fluctuations between different batches. The prepared non-uniform cemented carbide structure was prone to defects such as pores and cobalt pools, and had low sphericity. Summary of the Invention

[0004] The purpose of this invention is to at least solve one of the technical problems existing in the prior art, and to provide a high-strength ultra-coarse alloy with quasi-spherical WC grains and its preparation method.

[0005] The technical solution of the present invention is as follows:

[0006] This invention also discloses a method for preparing a high-strength ultra-coarse alloy with spherical WC grains. The method uses tungsten carbide powder with a Fisher particle size of 20-40 μm, tungsten powder with a Co content of 0.5-0.6 μm, and spherical cobalt powder with a Co content of ≥99.5% as raw materials. Then, a forming agent and a dispersing medium are added, and the mixture is ball-milled in a ball mill to obtain a mixed slurry. The mixed slurry is then dried, pressed, and sintered in sequence to obtain the final product.

[0007] As a preferred embodiment of the present invention, the amount of tungsten powder added accounts for 0.5-1.5 wt% of the raw materials.

[0008] As a preferred embodiment of the present invention, the molding agent is paraffin wax.

[0009] As a preferred embodiment of the present invention, the ball milling time is 18-24 hours.

[0010] As a preferred embodiment of the present invention, the dispersion medium is anhydrous ethanol.

[0011] As a preferred embodiment of the present invention, the sintering temperature is 1400-1500℃ and the sintering time is 50-70min.

[0012] As a preferred embodiment of the present invention, the ball-to-material ratio in the ball mill is 2-4:1.

[0013] The present invention also discloses a high-strength ultra-coarse alloy with quasi-spherical WC grains, which is prepared by the preparation method described above.

[0014] The beneficial effects of this invention are as follows: This invention uses ultra-coarse tungsten carbide powder to prepare ultra-coarse alloys. Because it uses a WC-Co composition and paraffin wax as the forming agent, which has non-hygroscopic properties, it is not sensitive to oxygen during alloy preparation, and the total carbon content of the alloy can remain relatively stable. This invention reduces the total carbon content of the alloy by using ultra-fine tungsten powder (0.5-0.6 μm) in the ball milling mixing stage. The tungsten powder dissolves in the cobalt phase, inhibiting the dissolution and growth of tungsten carbide powder during alloy sintering, maintaining the near-spherical shape of the grains after ball milling, and preparing a low-magnetic-saturation, near-spherical WC-Co ultra-coarse cemented carbide with WC grains. While maintaining ultra-coarse grains, the near-spherical grains also provide high bending strength and good toughness. This invention is simple to operate, low in cost, highly controllable, and produces alloys with excellent properties.

[0015] This invention is simple to operate, low in cost, highly controllable, and produces alloys with excellent properties. Attached Figure Description

[0016] Figure 1 The metallographic image is a 1000x magnification of the sample from Comparative Example 2.

[0017] Figure 2 The metallographic image is a 1000x magnification of the sample from Example 3.

[0018] Figure 3 This is a metallographic image of the sample from Example 4 magnified 1000 times. Detailed Implementation

[0019] The embodiments of the present invention are described in detail below. These embodiments are exemplary and are only used to explain the present invention, and should not be construed as limiting the invention. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the art or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all commercially available conventional products.

[0020] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0021] Example 1

[0022] A method for preparing a high-strength ultra-coarse alloy with spherical WC grains involves using tungsten carbide powder with a Fisher particle size of 30 μm, tungsten powder with a particle size of 0.5-0.6 μm, and spherical cobalt powder with a Co content ≥99.5% as raw materials. A forming agent and a dispersing medium are then added, and the mixture is ball-milled in a horizontal ball mill to obtain a mixed slurry. The mixed slurry is then sequentially dried, pressed, and sintered to obtain the final product. The amount of Co powder added is 6% of the mass of the tungsten carbide powder.

[0023] The amount of tungsten powder added accounts for 0.6 wt% of the raw materials;

[0024] The dispersion medium is anhydrous ethanol; the molding agent is paraffin wax accounting for 2 wt% of the raw material; and the ball milling time is 20 h.

[0025] The sintering temperature is 1450℃ and the sintering time is 60min.

[0026] The ball-to-material ratio in the ball mill is 2:1.

[0027] Example 2

[0028] A method for preparing a high-strength ultra-coarse alloy with spherical WC grains involves using tungsten carbide powder with a Fisher particle size of 30 μm, tungsten powder with a particle size of 0.5-0.6 μm, and spherical cobalt powder with a Co content ≥99.5% as raw materials. A forming agent and a dispersion medium are then added, and the mixture is ball-milled in a ball mill to obtain a mixed slurry. The mixed slurry is then sequentially dried, pressed, and sintered to obtain the final product. The amount of Co powder added is 6% of the mass of the tungsten carbide powder, and the amount of tungsten powder added is 1.2 wt% of the raw materials.

[0029] The dispersion medium is anhydrous ethanol; the molding agent is paraffin wax accounting for 2 wt% of the raw material; and the ball milling time is 20 h.

[0030] The sintering temperature is 1450℃ and the sintering time is 60min.

[0031] The ball-to-material ratio in the ball mill is 2:1.

[0032] Example 3

[0033] A method for preparing a high-strength ultra-coarse alloy with spherical WC grains involves using tungsten carbide powder with a Fisher particle size of 30 μm, tungsten powder with a particle size of 0.5-0.6 μm, and spherical cobalt powder with a Co content ≥99.5% as raw materials. A forming agent and a dispersion medium are then added, and the mixture is ball-milled in a ball mill to obtain a mixed slurry. The mixed slurry is then sequentially dried, pressed, and sintered to obtain the final product. The amount of Co powder added is 10% of the mass of the tungsten carbide powder, and the amount of tungsten powder added is 0.6 wt% of the raw materials.

[0034] The dispersion medium is anhydrous ethanol; the molding agent is paraffin wax accounting for 2 wt% of the raw material; and the ball milling time is 20 h.

[0035] The sintering temperature is 1450℃ and the sintering time is 60min.

[0036] The ball-to-material ratio in the ball mill is 2:1.

[0037] Example 4

[0038] A method for preparing a high-strength ultra-coarse alloy with spherical WC grains involves using tungsten carbide powder with a Fisher particle size of 30 μm, tungsten powder with a particle size of 0.5-0.6 μm, and spherical cobalt powder with a Co content ≥99.5% as raw materials. A forming agent and a dispersion medium are then added, and the mixture is ball-milled in a ball mill to obtain a mixed slurry. The mixed slurry is then sequentially dried, pressed, and sintered to obtain the final product. The amount of Co powder added is 10% of the mass of the tungsten carbide powder, and the amount of tungsten powder added is 1.2 wt% of the raw materials.

[0039] The dispersion medium is anhydrous ethanol; the molding agent is paraffin wax accounting for 2 wt% of the raw material; and the ball milling time is 20 h.

[0040] The sintering temperature is 1450℃ and the sintering time is 60min.

[0041] The ball-to-material ratio in the ball mill is 2:1.

[0042] Comparative Example 1

[0043] A method for preparing a high-strength ultra-coarse alloy with spherical WC grains involves using tungsten carbide powder with a Fisher particle size of 30 μm and spherical cobalt powder with a Co content ≥99.5% as raw materials. A forming agent and a dispersing medium are then added, and the mixture is ball-milled in a ball mill to obtain a mixed slurry. The mixed slurry is then sequentially dried, pressed, and sintered to obtain the final product. The amount of Co powder added is 6% of the mass of the tungsten carbide powder.

[0044] The dispersion medium is anhydrous ethanol; the molding agent is paraffin wax accounting for 2 wt% of the raw material; and the ball milling time is 20 h.

[0045] The sintering temperature is 1450℃ and the sintering time is 60min.

[0046] The ball-to-material ratio in the ball mill is 2:1.

[0047] Comparative Example 2

[0048] A method for preparing a high-strength ultra-coarse alloy with spherical WC grains involves using tungsten carbide powder with a Fisher particle size of 30 μm and spherical cobalt powder with a Co content ≥99.5% as raw materials. A forming agent and a dispersion medium are then added, and the mixture is ball-milled in a ball mill to obtain a mixed slurry. The mixed slurry is then sequentially dried, pressed, and sintered to obtain the final product. The amount of Co powder added is 10% of the mass of the tungsten carbide powder.

[0049] The dispersion medium is anhydrous ethanol; the molding agent is paraffin wax accounting for 2 wt% of the raw material; and the ball milling time is 20 h.

[0050] The sintering temperature is 1450℃ and the sintering time is 60min.

[0051] The ball-to-material ratio in the ball mill is 2:1.

[0052] The WC carbon content values ​​of Comparative Examples 1 and 2, and Comparative Example 1 are shown in Table 1.

[0053] Table 1. WC equivalent total carbon (ETC) values ​​for Examples 1-3

[0054] Serial Number Sintering temperature / °C WC carbon content / % Co / % WC / % Tungsten powder content / % Comparative Example 1 1450 6.14 5.66 94.34 0 Example 1 1450 6.08 5.63 93.77 0.6 Example 2 1450 6.05 5.59 93.21 1.2

[0055] As can be seen from Table 1, the ETC value of WC in Example 1 is about 6.14 wt%, with a medium-high carbon content. Corresponding to the WC-Co phase diagram, it is located in the two-phase region near the boundary where free carbon is present. The ETC value of WC in Example 2 is close to 6.08 wt%, and according to the WC-Co phase diagram, it is located in the two-phase region. The ETC value of WC in Example 3 is close to 6.05 wt%, and according to the WC-Co phase diagram (from "Phase Diagram Theory and Its Applications" published by Higher Education Press in 2008, author Wang Chonglin), it is located in the two-phase region near the boundary where the η phase is formed.

[0056] Simultaneously, the performance of Examples 1-4 and Comparative Examples 1 and 2 was tested, and the test results are shown in […]. Figure 1-3 See Tables 2 and 3. It should be noted that in the tables below, TRS represents Transverse Rupture Strength, K... IC dn represents fracture toughness, dn represents average grain size, and HV3 represents Vickers hardness.

[0057] Table 2. Mechanical property test results of Examples 1 and 2 and Comparative Example 1 WC-6%Co

[0058]

[0059] Table 3. Mechanical property test results of Examples 3 and 4 and Comparative Example 2 WC-10%Co

[0060]

[0061] from Figure 1-3 As can be seen from Tables 2 and 3, by using ultrafine tungsten powder (0.5-0.6 μm) in the ball milling mixing stage to reduce the total carbon of the alloy, the tungsten powder dissolves in the cobalt phase, inhibiting the dissolution and growth of tungsten carbide powder during alloy sintering, maintaining the near-spherical shape of the grains after ball milling, and preparing a near-spherical WC-Co ultracoarse cemented carbide with low magnetic saturation. While maintaining ultracoarse grains, the alloy also has comprehensive properties such as high bending strength and good toughness due to the near-spherical grains.

[0062] Without causing conflict, those skilled in the art can freely combine and use the above-mentioned additional technical features.

[0063] The embodiments described above are merely preferred embodiments of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various other corresponding changes and modifications based on the technical solutions and concepts described above, and all such changes and modifications should fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing a high-strength, ultra-coarse alloy with quasi-spherical WC grains, characterized in that, Using tungsten carbide powder with a Fisher particle size of 20-40 μm, tungsten powder with a particle size of 0.6 μm, and spherical cobalt powder with a Co content ≥99.5 wt% as raw materials, a forming agent and a dispersing medium are added, and the mixture is ball-milled in a ball mill to obtain a mixed slurry. The mixed slurry is then sequentially dried, pressed, and sintered to obtain the final product. The amount of tungsten powder added accounts for 0.5-1.5 wt% of the raw materials. The ball milling time is 18-24 hours; The sintering temperature is 1400-1500℃, and the sintering time is 50-70min; The ball-to-material ratio in the ball mill is 2-4:

1.

2. The method for preparing a high-strength, ultra-coarse alloy with quasi-spherical WC grains according to claim 1, characterized in that, The molding agent is paraffin wax.

3. The method for preparing a high-strength, ultra-coarse alloy with quasi-spherical WC grains according to claim 1, characterized in that, The dispersion medium is anhydrous ethanol.

4. A high-strength, ultra-coarse alloy with quasi-spherical WC grains, characterized in that, It is prepared by any one of the preparation methods described in claims 1-3.

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