A high-strength and high-toughness cemented carbide and preparation method thereof

Abstract

The present invention relates to the technical field of alloy materials, and discloses a high-strength and high-toughness cemented carbide and a preparation method thereof; the raw material components include 3-15% Co, 5-15% additives, and the balance is WC by weight percentage; wherein the additive is a composite obtained by taking polyacid-MOF as a matrix and Cr and V as load elements. The present invention adds VC and Cr3C2 in a synergistic manner, which can overcome the problem of low performance improvement caused by the addition of a single inhibitor; rare earth elements are loaded by MOF materials, and the porous structure of MOF materials is used for loading, so that the cemented carbide has the characteristics of both strength and toughness.

Description

Technical Field

[0001] The invention relates to the technical field of alloy materials, in particular to high-strength and high-toughness cemented carbide and a preparation method thereof. Background Art

[0002] Cemented carbide is used to make knives, cutting tools, and wear-resistant parts because of its excellent wear resistance, oxidation resistance, and thermal stability. It is widely used in metal cutting, rock drilling shields, and military industries, and is known as the "teeth of industry." Cemented carbide is composed of high-hardness, insoluble carbides and adhesives, and is a powder metallurgy product sintered in a vacuum furnace or a hydrogen reduction furnace.

[0003] Although cemented carbide has excellent mechanical properties, ordinary cemented carbide cannot meet the requirements of high strength and high toughness at the same time. This is because as the amount of binder decreases and the grain size decreases, the hardness of the alloy increases; as the amount of binder increases and the grain size increases, the fracture toughness of the alloy increases. Therefore, how to prepare cemented carbide with both strength and toughness is one of the technical problems that need to be solved urgently.

[0004] The research results show that when the WC grain size in the alloy is submicron, with the refinement of WC grains, the hardness, strength, toughness and wear resistance of the alloy will be improved, and the temperature required to achieve full densification will be lower; as an ultrafine-grained cemented carbide with a WC grain size of only 0.2-0.5μm, it can significantly improve the strength of the alloy while improving the hardness to obtain "double high" characteristics. Based on this, currently, inhibitors such as VC and Cr3C2 are mostly introduced to achieve the above-mentioned purpose. However, although VC can greatly improve the fracture toughness of the alloy, its strength is significantly inferior to Cr3C2. At the same time, Cr3C2 has poor grain inhibition effect and its crystal strengthening effect is poor. Summary of the invention

[0005] Technical problems solved by the present invention:

[0006] It is used to solve the problem that current cemented carbide cannot have both strength and toughness.

[0007] The technical solution adopted by the present invention is:

[0008] In view of the above technical problems, the purpose of the present invention is to provide a high-strength and high-toughness cemented carbide and a preparation method thereof. The specific contents are as follows:

[0009] A high-strength and high-toughness hard alloy, wherein the components, by weight percentage, include 3-15% Co, 5-15% additives, and the balance is WC; wherein the additive is a composite body with polyacid-MOF as a matrix and Cr and V as load elements.

[0010] Specifically, the preparation method of the additive comprises the following steps:

[0011] Ammonium metavanadate, oxalic acid and chromium chloride are dissolved in hot water, ultrasonically mixed, and treated at 120-150° C. for 12-36 hours. After heating, the precursor is separated, washed and dried. The molar ratio of ammonium metavanadate, oxalic acid and chromium chloride is 1-3:1:0.1-0.8.

[0012] Yttrium chloride and 2,5-dihydroxyterephthalic acid are dissolved in a solvent, and then o-fluorobenzoic acid is added to obtain a mixed liquid, which is heat-treated in a reactor, cooled, separated, and washed to obtain MOF-Y. The molar ratio of yttrium chloride, 2,5-dihydroxyterephthalic acid, and o-fluorobenzoic acid is 1:1:8. The solvent is a mixed solution of N,N-dimethylformamide, water, and nitric acid, and the volume ratio is 35-38:1-4:1. The heat treatment is 110-130°C for 48-72 hours.

[0013] The precursor and MOF-Y prepared above are dispersed to obtain dispersion 1 and dispersion 2, dispersion 1 and dispersion 2 are mixed, subjected to hydrothermal treatment, and then separated and washed to obtain the additive. The solvent of dispersion 1 and dispersion 2 is methanol, and the mass ratio of the precursor to MOF-Y is 5 to 9:1. Ultrasonic mixing is used for mixing. Heat treatment process: 130 to 200°C, 6 to 15h.

[0014] In the present invention, the above-mentioned method for preparing a high-strength and high-toughness cemented carbide comprises the following steps:

[0015] The raw materials mentioned above are mixed in proportion, and then ball-milled, formed and sintered to obtain cemented carbide.

[0016] To expand on this, it means:

[0017] Weigh each raw material component according to the rated addition amount, and after weighing, transfer it to a ball mill for ball milling. Use anhydrous ethanol as the ball milling medium, the speed is 200-400r / min, the time is 3-8h, and the ball-to-material ratio is 3-5:1.

[0018] After grinding, the material is screened and dried, and the screening and drying processes can be conventional operations in the art. The drying method can be spray drying or vacuum drying.

[0019] After forming, it is sintered at 1250-1500℃, kept warm for 2-5h, and the pressure in the furnace is controlled at 4-5MPa. After sintering, it slowly cools down to room temperature.

[0020] The technical mechanism and beneficial effects adopted by the present invention are as follows:

[0021] The present invention can suppress the problem of uneven distribution caused by adding the inhibitor to the mixture to the greatest extent by adding the carbide precursor in the form of polyacid. Adding in a coordinated manner of VC and Cr3C2 can overcome the problem of low performance improvement caused by adding a single inhibitor; in addition, by adding in the form of a precursor, it is more conducive to the dispersion in the mixture, and the doped elements are introduced into the molecular structure of the polyacid, which can make the doped atoms close to the active center of the carbide, thereby playing a synergistic effect of grain refinement. Rare earth elements are loaded by MOF materials, because rare earth elements are usually dispersed in the form of spherical particles, and the porous structure of MOF materials is used for loading, thereby improving the problem of avoiding processing losses, and then the rare earth elements are dissolved in the WC crystal in the form of second-phase nanocrystals, so that the cemented carbide has the characteristics of both strength and toughness. Then the polyacid-MOF material is added to the mixture for sintering, which can ensure that the metal atoms and carbon atoms are in contact at the atomic / molecular level, thereby achieving the uniform state of the carbide obtained in the end; and both the polyacid and MOF have carbon sources, and no additional introduction is required. Finally, the present invention makes full use of the characteristics of each raw material and can optimize the performance of the obtained cemented carbide. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0023] <Example>

[0024] Example 1

[0025] This embodiment provides a high-strength and high-toughness cemented carbide, comprising the following steps:

[0026] Weigh 5 parts of Co powder, 10 parts of dopant @MOF-Y, and 85 parts of WC powder; mix them evenly to obtain a mixture.

[0027] The preparation method of the aforementioned dopant @MOF-Y is as follows: (1) ammonium metavanadate, oxalic acid and chromium chloride are dissolved in hot water, and the molar ratio of ammonium metavanadate, oxalic acid and chromium chloride is 2:1:0.5. After ultrasonic mixing, the mixture is treated at 140°C for 24 hours. After heating, the dopant is obtained by separation, washing and drying. (2) yttrium chloride and 2,5-dihydroxyterephthalic acid are dissolved in a solvent, and then o-fluorobenzoic acid is added to obtain a mixed liquid. The molar ratio of yttrium chloride, 2,5-dihydroxyterephthalic acid and o-fluorobenzoic acid in the mixed liquid is 1:1:8; the solvent is a mixed liquid of N,N-dimethylformamide, water and nitric acid, and the volume ratio is 36:3:1. The mixed liquid is then transferred to a reactor for heat treatment at 120°C. After treatment for 48 hours, MOF-Y is obtained by cooling, separation and washing. (3) The dopant and MOF-Y prepared above are dispersed to obtain dispersion 1 and dispersion 2, and dispersion 1 and dispersion 2 are ultrasonically mixed and then hydrothermally treated at 150°C for 10 h. After the treatment, they are separated and washed to obtain dopant@MOF-Y. The solvent of dispersion 1 and dispersion 2 is methanol, and the mass ratio of dopant to MOF-Y is 5:1.

[0028] Weigh the obtained mixture and transfer it to a ball mill for ball milling. The ball milling medium is anhydrous ethanol, the speed is 300r / min, the time is 5h, and the ball-to-material ratio is 5:1. After grinding, it is screened, dried, formed, and then sintered: 1400℃, heat preservation for 3h, control the pressure in the furnace to 4-5MPa, and slowly cool to room temperature after sintering to obtain the finished product.

[0029] Example 2

[0030] The difference between this embodiment and embodiment 1 is that the molar ratio of ammonium metavanadate, oxalic acid and chromium chloride is 1:1:0.5.

[0031] Example 3

[0032] The difference between this embodiment and embodiment 1 is that the sintering temperature is 1500° C. and the heat preservation time is 3 hours.

[0033] Example 4

[0034] The difference between this embodiment and embodiment 1 is that Co powder is 10 parts, dopant @MOF-Y is 10 parts, and WC powder is 80 parts.

[0035] <Comparative Example>

[0036] Comparative Example 1

[0037] The difference between this comparative example and Example 1 is that the additive is replaced by a blend of VC and Cr2C3, and the ratio of the two is 2:0.5.

[0038] Comparative Example 2

[0039] The difference between this comparative example and Example 1 is that the dopant @MOF-Y is replaced by the dopant.

[0040] Comparative Example 3

[0041] The difference between this comparative example and Example 1 is that the dopant @MOF-Y is replaced by the dopant @MOF.

[0042] <Test example>

[0043] The properties of the finished products prepared in Examples 1-4 and Comparative Examples 1-3 were measured. The results are shown in Table 1.

[0044] Table 1 Measurement results

[0045]

[0046] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A high-strength and high-toughness cemented carbide, characterized in that: The raw material components include 3-15% Co, 5-15% additives, and the balance WC by weight percentage; wherein the additive is a composite obtained by using polyacid-MOF as a matrix and Cr and V as loading elements; The preparation method of the additive is: a precursor containing a Cr source and a V source and MOF are subjected to hydrothermal treatment to obtain the additive; the precursor containing a Cr source and a V source is obtained by doping a Cr source with polyvanadic acid; the method of doping a Cr source with polyvanadic acid is: ammonium metavanadate, oxalic acid, and chromium chloride are dissolved in hot water, mixed, subjected to hydrothermal treatment, and after completion, separated, washed, and dried to obtain the additive; MOF is loaded with Y; the loading method is that yttrium chloride and 2,5-dihydroxyterephthalic acid are dissolved in a solvent, and then o-fluorobenzoic acid is added to obtain a mixed liquid, which is heat-treated in a reactor, and then cooled, separated, and washed to obtain MOF loaded with Y.

2. The high-strength and high-toughness cemented carbide according to claim 1, characterized in that: The molar ratio of ammonium metavanadate, oxalic acid and chromium chloride is 1-3:1:0.1-0.8; and / or, hydrothermal treatment: 120-150° C., treatment 12-36 hours.

3. The high-strength and high-toughness cemented carbide according to claim 2, characterized in that: The loading method includes: the molar ratio of yttrium chloride, 2,5-dihydroxyterephthalic acid, and o-fluorobenzoic acid is 1:1:8; and / or the solvent is a mixture of N,N-dimethylformamide, water, and nitric acid, and the volume ratio is 35~38:1~4:1; and / or the heat treatment is 110~130°C for 48~72h.

4. The high-strength and high-toughness cemented carbide according to claim 1, characterized in that: The mass ratio of the precursor to the MOF is 5-9:1; and / or, heat treatment: 130-200° C., 6-15 h.

5. A method for preparing a high-strength and high-toughness cemented carbide according to any one of claims 1 to 4, characterized in that: The raw material components are weighed, and hard alloy is obtained through blending, ball milling, molding and sintering.

6. The method for preparing high-strength and high-toughness cemented carbide according to claim 5, characterized in that: The ball milling medium is anhydrous ethanol, the rotation speed is 200~400r / min, the time is 3~8h, and the ball-to-material ratio is 3~5:1; sintering treatment: 1250~1500℃, insulation for 2~5h, and the pressure in the furnace is controlled at 4~5MPa.

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