A kind of hard tungsten carbide alloy and preparation method thereof

Abstract

The present invention discloses a hard tungsten carbide alloy and a preparation method thereof, and belongs to the technical field of hard alloy preparation. The hard tungsten carbide alloy comprises a matrix, wherein first hard particles and second hard particles are distributed inside the matrix, the second hard particles are filled between the first hard particles, the first hard particles are plate-like structures, and the second hard particles are spherical structures, and the matrix comprises tungsten carbide, a binder and an additive. The present invention also discloses a preparation method thereof for the hard tungsten carbide alloy. The hard tungsten carbide alloy and the preparation method thereof described in the present invention can improve the hardness and toughness of the tungsten carbide alloy.

Description

Technical Field

[0001] The invention relates to the technical field of hard alloy preparation, in particular to a hard tungsten carbide alloy and a preparation method thereof. Background Art

[0002] Hard tungsten carbide alloy usually refers to a high-performance material made of tungsten carbide (WC) as the main hard phase combined with a metal binder phase. This type of alloy is known for its excellent hardness, wear resistance and heat resistance, and is widely used in cutting tools, drilling, wear parts and many high-performance industrial processing fields. The hard phase WC in tungsten carbide alloy provides wear resistance and hardness for the material, and the binder phase Co provides the fracture toughness of the material. The hardness and toughness of the material in tungsten carbide alloy are a pair of contradictory properties in tungsten carbide alloy. How to improve the hardness while ensuring the toughness of tungsten carbide alloy, or to improve the toughness while ensuring the hardness is the main research direction of tungsten carbide alloy.

[0003] At present, the modification of tungsten carbide alloy is generally carried out by improving the structure of tungsten carbide alloy to improve the performance of tungsten carbide alloy. The existing patent CN202111637547.9 discloses a preparation method of rare earth added cemented carbide, which includes the following preparation steps: (1) calcining waste high-cobalt coarse-grained cemented carbide to obtain waste cemented carbide containing η phase; (2) crushing and sieving the waste cemented carbide containing η phase to obtain waste cemented carbide powder; (3) ball milling, granulating, pressing and sintering the waste cemented carbide powder with a salt solution of rare earth elements, C powder and WC powder to obtain rare earth added cemented carbide; the waste cemented carbide containing η phase contains 50-80% by weight of η phase. The above patent calcines waste high-cobalt coarse-grained cemented carbide and sinters it together with rare earth elements and WC powder to obtain WC grains with a plate-like structure, while improving the hardness and toughness of the cemented carbide. However, the above patent only improves the hardness and toughness of cemented carbide by improving the organization of carbide alloy, and this method cannot obtain high hardness and toughness of tungsten carbide alloy. Summary of the invention

[0004] The purpose of the present invention is to provide a hard tungsten carbide alloy and a preparation method thereof, so as to improve the hardness and toughness of the tungsten carbide alloy.

[0005] To achieve the above-mentioned object, the present invention provides a hard tungsten carbide alloy, comprising a matrix, wherein first hard particles and second hard particles are distributed inside the matrix, the second hard particles are filled between the first hard particles, the first hard particles are a plate-like structure, and the second hard particles are a spherical structure, and the matrix comprises tungsten carbide, a binder and an additive.

[0006] Preferably, the mass percentage of the first hard particles added is 10Wt.%-20Wt.%, the length of the first hard particles is 50μm-60μm, and the length:width of the first hard particles is 1:(0.6-0.8); the first hard particles include 80Wt.%-90Wt.% tungsten carbide and 10Wt.%-20Wt.% cobalt.

[0007] Preferably, the mass percentage of the second hard particles added is 50Wt.%-60Wt.%, and the particle size of the second hard particles is 10μm-20μm; the second hard particles include 90Wt.%-95Wt.% tungsten carbide, 5Wt.%-10Wt.% cobalt and 1Wt.%-2Wt.% titanium carbide.

[0008] Preferably, the matrix comprises 70wt.%-80wt.% of tungsten carbide, 15wt.%-25wt.% of a binder and 3wt.%-5wt.% of an additive; the particle size of tungsten carbide in the matrix is ​​5μm-10μm, and the binder comprises four elements of Fe, Co, Ni and Cr in a molar ratio of 1:1:1:1.

[0009] Preferably, the additive includes 2wt.%-4.5wt.% of strengthening elements and 0.5wt.%-1wt.% of rare earth elements, the strengthening elements are one or a mixture of several of titanium, tantalum and niobium, and the rare earth elements are one or a mixture of two of La and Ce.

[0010] The preparation method of the above-mentioned hard tungsten carbide alloy comprises the following steps:

[0011] S1, preparing first hard particles;

[0012] S2, preparing second hard particles;

[0013] S3, preparing a matrix raw material, adding the first hard particles and the second hard particles into the matrix raw material, mixing them evenly, pressing and then sintering to obtain a hard tungsten carbide alloy blank;

[0014] S4. Heat-treating the cemented tungsten carbide alloy blank to obtain cemented tungsten carbide alloy.

[0015] Preferably, the S1 comprises the following steps:

[0016] S11, weighing raw material tungsten carbide powder and cobalt powder according to the composition ratio;

[0017] S12, mixing tungsten carbide powder and cobalt powder by ball milling to obtain a first mixed powder;

[0018] S13, pressing the first mixed powder into a shape and then sintering the mixture at a temperature of 1400° C. to 1500° C. under the protection of an inert gas to obtain a first sintered product;

[0019] S14, crushing the first sintered product, ball milling, sieving, and flattening the product to obtain first hard particles.

[0020] Preferably, S2 comprises the following steps:

[0021] S21, weighing flat raw material tungsten powder, cobalt powder and titanium carbide powder according to the composition ratio;

[0022] S22, mixing tungsten powder and graphite powder evenly, wherein the weight of graphite powder is 5wt.%-6wt.% of the mass of tungsten powder; and pre-sintering under inert gas protection at a temperature of 1000°C-1100°C to obtain prefabricated plate-shaped tungsten carbide;

[0023] S23, ball-milling and mixing the prefabricated plate-shaped tungsten carbide, activated carbon powder, titanium carbide powder and cobalt powder to obtain a second mixed powder, pressing the second mixed powder into a mold and sintering it at a temperature of 1400° C. to 1500° C. to obtain a second sintered product;

[0024] S24, crushing the second sintered product, ball milling it, and sieving it to obtain second hard particles.

[0025] Preferably, S3 comprises the following steps:

[0026] S31, weighing Fe, Co, Ni, and Cr powders according to the component ratio, and mixing them uniformly by ball milling to obtain a binder powder;

[0027] S32, mixing and ball-milling the binder powder with tungsten carbide powder, titanium, tantalum, niobium powder and rare earth nitrate solution to obtain a matrix raw material;

[0028] S33, adding the first hard particles and the second hard particles into the matrix raw material, ball milling and mixing them evenly, pressing and forming, sintering in a spark plasma sintering furnace, and obtaining a hard tungsten carbide alloy blank after cooling.

[0029] Preferably, in S4, the heat treatment temperature is 1200° C.-1300° C., and the heat treatment time is 4 hours-6 hours.

[0030] The advantages and positive effects of the hard tungsten carbide alloy and the preparation method thereof described in the present invention are:

[0031] 1. The present invention adds a first hard particle and a second hard particle to the tungsten carbide alloy, wherein the first hard particle is a plate-like structure, and the second hard particle is a spherical structure. The size of the first hard particle is larger than that of the second hard particle, so that the second hard particle is filled between the first hard particles. The plate-like hard particles and the spherical hard particles synergistically enhance the tungsten carbide alloy, thereby effectively improving the hardness, toughness and fracture resistance of the tungsten carbide alloy.

[0032] 2. The tungsten carbide in the second hard particles is a plate-like tungsten carbide grain, which is beneficial to improving the hardness and toughness of the second hard particles.

[0033] 3. The use of Fe, Co, Ni, and Cr multi-component binders in the matrix alloy is beneficial to improving the toughness, wear resistance, and corrosion resistance of tungsten carbide, and effectively reducing the cost of the binder.

[0034] 4. The strengthening elements of titanium, tantalum and niobium in the matrix can form carbides. Under heat treatment conditions, titanium, tantalum and niobium carbides precipitate and disperse at the grain boundaries to achieve grain boundary strengthening, thereby significantly improving the high temperature performance and wear resistance of the carbide alloy.

[0035] 5. The sintering of tungsten carbide alloy by spark plasma sintering furnace can be carried out at a lower temperature and in a shorter time to obtain a dense tungsten carbide alloy, effectively inhibit the growth of tungsten carbide alloy grains, obtain fine and uniform tungsten carbide grains, and improve the comprehensive performance of tungsten carbide alloy.

[0036] 6. The method described in the present invention can be used to obtain a densely organized tungsten carbide alloy, thereby improving the bending strength, toughness and hardness of the tungsten carbide alloy. DETAILED DESCRIPTION

[0037] The technical solution of the present invention is further illustrated by the following examples.

[0038] A hard tungsten carbide alloy comprises a matrix, wherein first hard particles and second hard particles are distributed inside the matrix, and the second hard particles are filled between the first hard particles. The first hard particles are plate-shaped and the second hard particles are spherical. The size of the first hard particles is larger than that of the second hard particles, so that the second hard particles are filled between the first hard particles, and the plate-shaped hard particles and the spherical hard particles synergistically enhance the tungsten carbide alloy, thereby effectively improving the hardness, toughness and fracture resistance of the tungsten carbide alloy.

[0039] The mass percentage of the first hard particle addition is 10wt.%-20wt.%, the length of the first hard particle is 50μm-60μm, and the length: width of the first hard particle is 1:(0.6-0.8). The first hard particle includes 80wt.%-90wt.% tungsten carbide and 10wt.%-20wt.% cobalt.

[0040] The mass percentage of the second hard particles added is 50Wt.%-60Wt.%, and the particle size of the second hard particles is 10μm-20μm; the second hard particles include 90Wt.%-95Wt.% tungsten carbide, 5Wt.%-10Wt.% cobalt and 1Wt.%-2Wt.% titanium carbide.

[0041] The first hard particles and the second hard particles have a relatively high content of tungsten carbide, which has a higher hardness than the matrix, so that the first hard particles and the second hard particles form a hard reinforcement phase in the matrix, thereby improving the hardness and wear resistance of the tungsten carbide alloy. Titanium carbide is added to the second hard particles, and the microscopic morphology of the second hard particles is plate-like tungsten carbide, which has a higher hardness than the first hard particles.

[0042] Plate-like hard particles can provide higher shear strength and wear resistance in tungsten carbide alloys, and can effectively block the crack propagation path during cutting and wear. Spherical hard particles are beneficial to improving the compressive strength of tungsten carbide alloys and reducing stress concentration. The combination of the two can effectively inhibit the propagation of cracks, improve the fracture resistance of tungsten carbide alloys, and improve the hardness and toughness of tungsten carbide alloys. In addition, spherical hard particles can be more evenly distributed in the matrix and provide support for plate-like hard particles, reducing the risk of bending or breaking of plate-like hard particles during force. Spherical hard particles are filled between plate-like hard particles, increasing the overall density and stability of tungsten carbide alloys. When subjected to external forces, plate-like hard particles tend to deflect cracks along their plane direction. The deformation of the matrix around the spherical hard particles can absorb energy, effectively delay crack propagation, and improve the fracture resistance of tungsten carbide alloys.

[0043] The matrix includes tungsten carbide, a binder and an additive. The matrix includes tungsten carbide with a mass percentage of 70wt.%-80wt.%, a binder with a mass percentage of 15wt.%-25wt.% and an additive with a mass percentage of 3wt.%-5wt.%. The particle size of tungsten carbide in the matrix is ​​5μm-10μm, and the binder includes four elements of Fe, Co, Ni and Cr with a molar ratio of 1:1:1:1. The additive includes a strengthening element with a mass percentage of 2wt.%-4.5wt.% and a rare earth element with a mass percentage of 0.5wt.%-1wt.%. The strengthening element is a mixture of one or more of titanium, tantalum and niobium. The rare earth element is a mixture of one or two of La and Ce.

[0044] The use of Fe, Co, Ni, and Cr multi-component binders is beneficial to improving the toughness, wear resistance, and corrosion resistance of tungsten carbide, and effectively reducing the cost of the binder. Adding Fe to the binder is beneficial to reducing the cost of the binder relative to pure Co. The Ni element can significantly enhance the wear resistance and corrosion resistance of the alloy, and helps to form a fine and stable bonding phase, thereby improving the overall toughness of the alloy. The Cr element can form a dense oxide layer, which effectively prevents the alloy from oxidative corrosion in high temperature or corrosive environments. Cr can strengthen the alloy matrix, improve the hardness and wear resistance of the matrix, especially the hardness and wear resistance under high temperature conditions. Therefore, the use of Fe, Co, Ni, and Cr multi-component binders is beneficial to improving the toughness, wear resistance, and high temperature performance of the tungsten carbide alloy matrix.

[0045] Titanium, tantalum and niobium strengthening elements are added to the matrix. Titanium, tantalum and niobium elements can form carbides. Under heat treatment conditions, titanium, tantalum and niobium carbides precipitate and disperse at the grain boundaries to achieve grain boundary strengthening, thereby significantly improving the high temperature performance and wear resistance of the carbide alloy.

[0046] Rare earth elements can refine tungsten carbide grains and reduce the stress between grains, thereby improving the toughness of the matrix, and also helping to improve the wear resistance and fatigue resistance of the tungsten carbide matrix. Rare earth can improve the wettability between tungsten carbide particles and binders, promote the good bonding between tungsten carbide particles and binders, and improve the interface bonding strength of tungsten carbide alloys. Lanthanum can form a protective film on the alloy surface, effectively resist high-temperature oxidation, improve the thermal stability of the alloy, and extend its service life.

[0047] The preparation method of the above-mentioned hard tungsten carbide alloy comprises the following steps:

[0048] S1. Prepare first hard particles.

[0049] S1 specifically includes the following steps:

[0050] S11. Weigh the raw materials tungsten carbide powder and cobalt powder according to the composition ratio.

[0051] S12, ball-milling the tungsten carbide powder and the cobalt powder to obtain a first mixed powder. The ball milling can be dry milling or wet milling as needed. The ball milling is carried out under the protection of an inert gas to avoid oxidation. The inert gas can be high-purity argon. The ball-to-material ratio of the ball milling is 5:1, and the ball milling time is 30h-40h.

[0052] S13, after pressing the first mixed powder into a shape, sintering the mixture at a temperature of 1400° C. to 1500° C. under the protection of an inert gas for 1 h to 2 h to obtain a first sintered product.

[0053] S14, crushing the first sintered product, ball milling, sieving, and flattening the product to obtain first hard particles. The first hard particles are plate-like structures composed of spherical tungsten carbide.

[0054] S2. preparing second hard particles.

[0055] S2 specifically includes the following steps:

[0056] S21. Weigh flat raw material tungsten powder, cobalt powder and titanium carbide powder according to the proportion of the components. The hard alloy ball flattens the tungsten powder for 40h-60h under the condition of a ball-to-material ratio of 5:1 to obtain a flat raw material tungsten powder, which is conducive to obtaining plate-shaped tungsten carbide.

[0057] S22, mix tungsten powder and graphite powder evenly, the weight of graphite powder is 5wt.%-6wt.% of the mass of tungsten powder, pre-sinter under inert gas protection at 1000℃-1100℃, the pre-sintering time is 1h-2h, and prefabricated plate-shaped tungsten carbide is obtained. Graphite powder uses flake graphite, which has low activity and is conducive to obtaining plate-shaped tungsten carbide. By controlling the content of graphite powder, the growth of tungsten carbide grains is avoided, the size of tungsten carbide grains is controlled, and the uniformity of tungsten carbide grains is improved.

[0058] S23, ball-milling the prefabricated plate-shaped tungsten carbide, activated carbon powder, titanium carbide powder and cobalt powder to obtain a second mixed powder. Use activated carbon powder to make up the remaining carbon. Zirconium balls are used for ball milling, the ball-to-material ratio is 6:1, and the ball milling time is 20h-30h. The second mixed powder is pressed into shape and sintered at a temperature of 1400℃-1500℃ for 1h-2h to obtain a second sintered product. Sintering is carried out under inert gas protection or under vacuum conditions.

[0059] Titanium carbide is a tungsten carbide grain-forming element, which can promote the transformation of tungsten carbide grains into plate-like grains, which is beneficial to obtaining plate-like tungsten carbide.

[0060] S24, crushing the second sintered product, ball milling and sieving to obtain second hard particles. The second hard particles are spherical structures composed of plate-like tungsten carbide. The content of the plate-like tungsten carbide in the second hard particles accounts for 85%-90% of the total amount of tungsten carbide grains.

[0061] S3, preparing a matrix raw material, adding the first hard particles and the second hard particles into the matrix raw material, ball milling them evenly, pressing and then sintering to obtain a hard tungsten carbide alloy blank.

[0062] S3 specifically includes the following steps:

[0063] S31. Fe, Co, Ni and Cr powders are weighed according to the component ratio and mixed evenly by ball milling to obtain binder powder. The ball-to-material ratio of the ball milling is 10:1 and the ball milling time is 40h-50h.

[0064] S32, the binder powder is mixed with tungsten carbide powder, titanium, tantalum, niobium powder and rare earth nitrate solution, and ball milled to obtain a matrix raw material. The ball-to-material ratio of the ball milling is 5:1, and the ball milling time is 30h-40h. After ball milling, the matrix raw material is dried under the drying condition of 60°C in a vacuum drying oven for 12h-24h.

[0065] S33, add the first hard particles and the second hard particles to the matrix raw material, mix them evenly with a mixer, press them into shape, sinter them in a spark plasma sintering furnace, and obtain a hard tungsten carbide alloy blank after cooling. The spark plasma sintering furnace has the advantages of fast heating speed, short sintering time and low sintering temperature. It can be sintered at a lower temperature and in a shorter time to obtain a dense tungsten carbide alloy, effectively inhibit the growth of tungsten carbide alloy grains, obtain fine and uniform tungsten carbide grains, and improve the comprehensive performance of tungsten carbide alloy. Sintering is carried out under the protection of inert gas, the sintering temperature is 1300℃-1400℃, the sintering time is 10min-20min, and the sintering pressure is 20MPa-40MPa.

[0066] S4. Heat-treating the cemented tungsten carbide alloy blank to obtain cemented tungsten carbide alloy.

[0067] The heat treatment temperature is 1200℃-1300℃, and the heat treatment time is 4 hours-6 hours. When the tungsten carbide alloy is heat treated, the binder in the tungsten carbide alloy is softened and remelted, the uniformity of the binder distribution is improved, cracks and pore defects are repaired, the density of the tungsten carbide alloy is improved, the toughness of the tungsten carbide alloy is enhanced, and the crack propagation resistance of the tungsten carbide alloy is improved. Heat treatment causes titanium carbide, niobium carbide and tantalum carbide to precipitate in the tungsten carbide alloy matrix, and improves the hardness, wear resistance and heat resistance of the tungsten carbide alloy matrix.

[0068] Example 1

[0069] A hard tungsten carbide alloy comprises a matrix, wherein first hard particles and second hard particles are distributed inside the matrix, the second hard particles are filled between the first hard particles, the first hard particles are plate-like structures, the second hard particles are spherical structures, and the matrix comprises tungsten carbide, a binder and an additive.

[0070] The mass percentage of the first hard particle addition is 12 wt.%, the length of the first hard particle is 50 μm-60 μm, and the length: width of the first hard particle is 1: (0.6-0.8); the first hard particle includes 85 wt.% tungsten carbide and 15 wt.% cobalt.

[0071] The mass percentage of the second hard particles added is 58 wt.%, the particle size of the second hard particles is 10 μm-20 μm, and the second hard particles include 92 wt.% of tungsten carbide, 7 wt.% of cobalt, and 1 wt.% of titanium carbide.

[0072] The mass percentage of the matrix is ​​30wt.%. The matrix includes 80wt.% of tungsten carbide, 16wt.% of a binder and 4wt.% of an additive. The particle size of tungsten carbide in the matrix is ​​5μm-10μm, and the binder includes four elements of Fe, Co, Ni and Cr in a molar ratio of 1:1:1:1.

[0073] The additives include 3.5wt.% of strengthening elements and 0.5wt.% of rare earth elements, wherein the strengthening element is titanium and the rare earth element is La.

[0074] The preparation method of hard tungsten carbide alloy comprises the following steps:

[0075] S1. Prepare first hard particles.

[0076] S1 includes the following steps:

[0077] S11. Weigh the raw materials tungsten carbide powder and cobalt powder according to the composition ratio.

[0078] S12, ball-milling the tungsten carbide powder and the cobalt powder to obtain a first mixed powder, wherein the ball-to-material ratio of the ball milling is 5:1, and the ball milling time is 30 hours.

[0079] S13, pressing the first mixed powder into a shape, and then sintering the mixture at 1450° C. under the protection of an inert gas to obtain a first sintered product.

[0080] S14, crushing the first sintered product, ball milling, sieving, and flattening the product to obtain first hard particles.

[0081] S2. preparing second hard particles.

[0082] S2 includes the following steps:

[0083] S21. Weigh flat raw materials of tungsten powder, cobalt powder and titanium carbide powder according to the proportion of the components. The tungsten powder is flattened for 50 hours under the condition that the ratio of the hard alloy ball to the material is 5:1.

[0084] S22, tungsten powder and graphite powder are mixed evenly, the weight of graphite powder is 6wt.% of the mass of tungsten powder, and pre-sintered under inert gas protection at 1000°C for 1 hour to obtain prefabricated plate-shaped tungsten carbide.

[0085] S23, ball-milling the prefabricated plate-shaped tungsten carbide, activated carbon powder, titanium carbide powder and cobalt powder to obtain a second mixed powder. The ball-to-material ratio is 6:1, and the ball milling time is 30 hours. The second mixed powder is pressed into a shape and sintered at a temperature of 1480° C. for 1 hour to obtain a second sintered product.

[0086] S24, crushing the second sintered product, ball milling it, and sieving it to obtain second hard particles.

[0087] S3, preparing a matrix raw material, adding the first hard particles and the second hard particles into the matrix raw material and mixing them evenly, pressing and forming, and then sintering to obtain a hard tungsten carbide alloy blank.

[0088] S3 includes the following steps:

[0089] S31. Fe, Co, Ni and Cr powders are weighed according to the component ratio and mixed evenly by ball milling to obtain binder powder. The ball-to-material ratio of the ball milling is 10:1 and the ball milling time is 40 hours.

[0090] S32, the binder powder is mixed with tungsten carbide powder, titanium, tantalum, niobium powder and rare earth nitrate solution, and ball milled to obtain a matrix raw material. The ball-to-material ratio of the ball milling is 5:1, and the ball milling time is 30 hours. After ball milling, the matrix raw material is dried under the drying condition of 60° C. in a vacuum drying oven for 20 hours.

[0091] S33, adding the first hard particles and the second hard particles to the matrix raw material, ball milling and mixing, pressing and forming, sintering in a spark plasma sintering furnace, and cooling to obtain a hard tungsten carbide alloy blank. The sintering temperature is 1350°C, the sintering time is 12 minutes, and the sintering pressure is 20MPa.

[0092] S4. Heat-treating the cemented tungsten carbide alloy blank to obtain cemented tungsten carbide alloy.

[0093] The heat treatment temperature is 1200°C and the heat treatment time is 5 hours.

[0094] Example 2

[0095] A hard tungsten carbide alloy comprises a matrix, wherein first hard particles and second hard particles are distributed inside the matrix, the second hard particles are filled between the first hard particles, the first hard particles are plate-like structures, the second hard particles are spherical structures, and the matrix comprises tungsten carbide, a binder and an additive.

[0096] The mass percentage of the first hard particle addition is 18 wt.%, the length of the first hard particle is 50 μm-60 μm, and the length: width of the first hard particle is 1: (0.6-0.8). The first hard particle includes 80 wt. wt. % tungsten carbide and 20 wt. % cobalt.

[0097] The mass percentage of the second hard particles added is 50 wt.%, the particle size of the second hard particles is 10 μm-20 μm, and the second hard particles include 90 wt.% of tungsten carbide, 8 wt.% of cobalt, and 2 wt.% of titanium carbide.

[0098] The matrix has a mass percentage of 32 wt.%. The matrix includes 70 wt.% tungsten carbide, 25 wt.% binder and 5 wt.% additive. The particle size of tungsten carbide in the matrix is ​​5 μm-10 μm, and the binder includes four elements of Fe, Co, Ni and Cr in a molar ratio of 1:1:1:1.

[0099] The additive comprises 4wt.% of strengthening elements and 1wt.% of rare earth elements, wherein the strengthening element is niobium and the rare earth element is Ce.

[0100] The preparation method of hard tungsten carbide alloy comprises the following steps:

[0101] S1. Prepare first hard particles.

[0102] S1 includes the following steps:

[0103] S11. Weigh the raw materials tungsten carbide powder and cobalt powder according to the composition ratio.

[0104] S12, ball-milling the tungsten carbide powder and the cobalt powder to obtain a first mixed powder, wherein the ball-to-material ratio of the ball milling is 5:1, and the ball milling time is 30 hours.

[0105] S13, pressing the first mixed powder into a shape, and then sintering the mixture at 1450° C. under the protection of an inert gas to obtain a first sintered product.

[0106] S14, crushing the first sintered product, ball milling, sieving, and flattening the product to obtain first hard particles.

[0107] S2. preparing second hard particles.

[0108] S2 includes the following steps:

[0109] S21. Weigh flat raw materials of tungsten powder, cobalt powder and titanium carbide powder according to the proportion of the components. The tungsten powder is flattened for 50 hours under the condition that the ratio of the hard alloy ball to the material is 5:1.

[0110] S22, tungsten powder and graphite powder are mixed evenly, the weight of graphite powder is 5wt.% of the mass of tungsten powder, and pre-sintered under inert gas protection at 1100°C for 1 hour to obtain prefabricated plate-shaped tungsten carbide.

[0111] S23, ball-milling the prefabricated plate-shaped tungsten carbide, activated carbon powder, titanium carbide powder and cobalt powder to obtain a second mixed powder. The ball-to-material ratio is 6:1, and the ball milling time is 30 hours. The second mixed powder is pressed into a shape and sintered at a temperature of 1450° C. for 1 hour to obtain a second sintered product.

[0112] S24, crushing the second sintered product, ball milling it, and sieving it to obtain second hard particles.

[0113] S3, preparing a matrix raw material, adding the first hard particles and the second hard particles into the matrix raw material and mixing them evenly, pressing and forming, and then sintering to obtain a hard tungsten carbide alloy blank.

[0114] S3 includes the following steps:

[0115] S31. Fe, Co, Ni and Cr powders are weighed according to the component ratio and mixed evenly by ball milling to obtain binder powder. The ball-to-material ratio of the ball milling is 10:1 and the ball milling time is 40 hours.

[0116] S32, the binder powder is mixed with tungsten carbide powder, titanium, tantalum, niobium powder and rare earth nitrate solution, and ball milled to obtain a matrix raw material. The ball-to-material ratio of the ball milling is 5:1, and the ball milling time is 30 hours. After ball milling, the matrix raw material is dried under the drying condition of 60° C. in a vacuum drying oven for 20 hours.

[0117] S33, adding the first hard particles and the second hard particles to the matrix raw material, ball milling and mixing, pressing and forming, sintering in a spark plasma sintering furnace, and cooling to obtain a hard tungsten carbide alloy blank. The sintering temperature is 1400°C, the sintering time is 10 minutes, and the sintering pressure is 30MPa.

[0118] S4. Heat-treating the cemented tungsten carbide alloy blank to obtain cemented tungsten carbide alloy.

[0119] The heat treatment temperature is 1200°C and the heat treatment time is 4 hours.

[0120] Example 3

[0121] A hard tungsten carbide alloy comprises a matrix, wherein first hard particles and second hard particles are distributed inside the matrix, the second hard particles are filled between the first hard particles, the first hard particles are plate-like structures, the second hard particles are spherical structures, and the matrix comprises tungsten carbide, a binder and an additive.

[0122] The mass percentage of the first hard particle addition is 15 wt.%, the length of the first hard particle is 50 μm-60 μm, and the length: width of the first hard particle is 1: (0.6-0.8). The first hard particle includes 90 wt.% tungsten carbide and 10 wt.% cobalt.

[0123] The mass percentage of the second hard particles added is 60wt.%, the particle size of the second hard particles is 10μm-20μm, and the second hard particles include 90wt.% of tungsten carbide, 8wt.% of cobalt and 2wt.% of titanium carbide.

[0124] The mass percentage of the matrix is ​​25wt.%. The matrix includes 75wt.% of tungsten carbide, 20wt.% of a binder and 5wt.% of an additive. The particle size of tungsten carbide in the matrix is ​​5μm-10μm, and the binder includes four elements of Fe, Co, Ni and Cr in a molar ratio of 1:1:1:1.

[0125] The additives include 4.5wt.% of strengthening elements and 0.5wt.% of rare earth elements, wherein the strengthening element is titanium and the rare earth element is La.

[0126] The preparation method of hard tungsten carbide alloy comprises the following steps:

[0127] S1. Prepare first hard particles.

[0128] S1 includes the following steps:

[0129] S11. Weigh the raw materials tungsten carbide powder and cobalt powder according to the composition ratio.

[0130] S12, ball-milling the tungsten carbide powder and the cobalt powder to obtain a first mixed powder, wherein the ball-to-material ratio of the ball milling is 5:1 and the ball milling time is 40 hours.

[0131] S13, pressing the first mixed powder into a shape, and then sintering the mixture at 1480° C. under the protection of an inert gas to obtain a first sintered product.

[0132] S14, crushing the first sintered product, ball milling, sieving, and flattening the product to obtain first hard particles.

[0133] S2. preparing second hard particles.

[0134] S2 includes the following steps:

[0135] S21. Weigh flat raw materials of tungsten powder, cobalt powder and titanium carbide powder according to the proportion of the components. The tungsten powder is flattened for 50 hours under the condition that the ratio of the hard alloy ball to the material is 5:1.

[0136] S22, tungsten powder and graphite powder are mixed evenly, wherein the weight of graphite powder is 6wt.% of the weight of tungsten powder, and pre-sintered under inert gas protection at 1050°C for 1 hour to obtain prefabricated plate-shaped tungsten carbide.

[0137] S23, ball-milling the prefabricated plate-shaped tungsten carbide, activated carbon powder, titanium carbide powder and cobalt powder to obtain a second mixed powder. The ball-to-material ratio is 6:1, and the ball milling time is 30 hours. The second mixed powder is pressed into a shape and sintered at a temperature of 1450° C. for 1 hour to obtain a second sintered product.

[0138] S24, crushing the second sintered product, ball milling it, and sieving it to obtain second hard particles.

[0139] S3, preparing a matrix raw material, adding the first hard particles and the second hard particles into the matrix raw material and mixing them evenly, pressing and forming, and then sintering to obtain a hard tungsten carbide alloy blank.

[0140] S3 includes the following steps:

[0141] S31. Fe, Co, Ni and Cr powders are weighed according to the component ratio and mixed evenly by ball milling to obtain binder powder. The ball-to-material ratio of the ball milling is 10:1 and the ball milling time is 40 hours.

[0142] S32, the binder powder is mixed with tungsten carbide powder, titanium, tantalum, niobium powder and rare earth nitrate solution, and ball milled to obtain a matrix raw material. The ball-to-material ratio of the ball milling is 5:1, and the ball milling time is 40 hours. After ball milling, the matrix raw material is dried under the drying condition of 60° C. in a vacuum drying oven for 24 hours.

[0143] S33, adding the first hard particles and the second hard particles to the matrix raw material, ball milling and mixing, pressing and forming, sintering in a spark plasma sintering furnace, and cooling to obtain a hard tungsten carbide alloy blank. The sintering temperature is 1350°C, the sintering time is 15 minutes, and the sintering pressure is 30MPa.

[0144] S4. Heat-treating the cemented tungsten carbide alloy blank to obtain cemented tungsten carbide alloy.

[0145] The heat treatment temperature is 1200°C and the heat treatment time is 5 hours.

[0146] Example 4

[0147] A hard tungsten carbide alloy comprises a matrix, wherein first hard particles and second hard particles are distributed inside the matrix, the second hard particles are filled between the first hard particles, the first hard particles are plate-like structures, the second hard particles are spherical structures, and the matrix comprises tungsten carbide, a binder and an additive.

[0148] The mass percentage of the first hard particle addition is 17 wt.%, the length of the first hard particle is 50 μm-60 μm, and the length: width of the first hard particle is 1: (0.6-0.8). The first hard particle includes 80 wt.% tungsten carbide and 20 wt.% cobalt.

[0149] The mass percentage of the second hard particles added is 53 wt.%, the particle size of the second hard particles is 10 μm-20 μm, and the second hard particles include 95 wt.% of tungsten carbide, 4 wt.% of cobalt, and 1 wt.% of titanium carbide.

[0150] The mass percentage of the matrix is ​​30wt.%. The matrix includes 72wt.% of tungsten carbide, 25wt.% of a binder and 3wt.% of an additive. The particle size of tungsten carbide in the matrix is ​​5μm-10μm, and the binder includes four elements of Fe, Co, Ni and Cr in a molar ratio of 1:1:1:1.

[0151] The additive includes 2.5wt.% of a strengthening element and 0.5wt.% of a rare earth element, wherein the strengthening element is titanium and the rare earth element is Ce.

[0152] The preparation method of hard tungsten carbide alloy comprises the following steps:

[0153] S1. Prepare first hard particles.

[0154] S1 includes the following steps:

[0155] S11. Weigh the raw materials tungsten carbide powder and cobalt powder according to the composition ratio.

[0156] S12, ball-milling the tungsten carbide powder and the cobalt powder to obtain a first mixed powder, wherein the ball-to-material ratio of the ball milling is 5:1 and the ball milling time is 35 hours.

[0157] S13, pressing the first mixed powder into a shape, and then sintering the mixture at 1420° C. under the protection of an inert gas to obtain a first sintered product.

[0158] S14, crushing the first sintered product, ball milling, sieving, and flattening the product to obtain first hard particles.

[0159] S2. preparing second hard particles.

[0160] S2 includes the following steps:

[0161] S21. Weigh flat raw materials of tungsten powder, cobalt powder and titanium carbide powder according to the proportion of the components. The tungsten powder is flattened for 40 hours under the condition that the ratio of the hard alloy ball to the material is 5:1.

[0162] S22, tungsten powder and graphite powder are mixed evenly, the weight of graphite powder is 5wt.% of the mass of tungsten powder, and pre-sintered under inert gas protection at 1100°C for 1 hour to obtain prefabricated plate-shaped tungsten carbide.

[0163] S23, ball-milling the prefabricated plate-shaped tungsten carbide, activated carbon powder, titanium carbide powder and cobalt powder to obtain a second mixed powder. The ball-to-material ratio is 6:1, and the ball milling time is 30 hours. The second mixed powder is pressed into a shape and sintered at a temperature of 1500° C. for 1 hour to obtain a second sintered product.

[0164] S24, crushing the second sintered product, ball milling it, and sieving it to obtain second hard particles.

[0165] S3, preparing a matrix raw material, adding the first hard particles and the second hard particles into the matrix raw material and mixing them evenly, pressing and forming, and then sintering to obtain a hard tungsten carbide alloy blank.

[0166] S3 includes the following steps:

[0167] S31. Fe, Co, Ni and Cr powders are weighed according to the component ratio and mixed evenly by ball milling to obtain binder powder. The ball-to-material ratio of the ball milling is 10:1 and the ball milling time is 40 hours.

[0168] S32, the binder powder is mixed with tungsten carbide powder, titanium, tantalum, niobium powder and rare earth nitrate solution, and ball milled to obtain a matrix raw material. The ball-to-material ratio of the ball milling is 5:1, and the ball milling time is 40 hours. After ball milling, the matrix raw material is dried, and the drying condition is drying in a vacuum drying oven at 60°C for 12 hours.

[0169] S33, adding the first hard particles and the second hard particles to the matrix raw material, ball milling and mixing, pressing and forming, sintering in a spark plasma sintering furnace, and cooling to obtain a hard tungsten carbide alloy blank. The sintering temperature is 1400°C, the sintering time is 20 minutes, and the sintering pressure is 40MPa.

[0170] S4. Heat-treating the cemented tungsten carbide alloy blank to obtain cemented tungsten carbide alloy.

[0171] The heat treatment temperature is 1300°C and the heat treatment time is 6 hours.

[0172] Example 5

[0173] A hard tungsten carbide alloy comprises a matrix, wherein first hard particles and second hard particles are distributed inside the matrix, the second hard particles are filled between the first hard particles, the first hard particles are plate-like structures, the second hard particles are spherical structures, and the matrix comprises tungsten carbide, a binder and an additive.

[0174] The mass percentage of the first hard particle addition is 14 wt.%, the length of the first hard particle is 50 μm-60 μm, and the length: width of the first hard particle is 1: (0.6-0.8). The first hard particle includes 87 wt.% tungsten carbide and 13 wt.% cobalt.

[0175] The mass percentage of the second hard particles added is 58 wt.%, the particle size of the second hard particles is 10 μm-20 μm, and the second hard particles include 93 wt.% of tungsten carbide, 6 wt.% of cobalt, and 1 wt.% of titanium carbide.

[0176] The mass percentage of the matrix is ​​28wt.%. The matrix includes 77wt.% of tungsten carbide, 20wt.% of a binder and 3wt.% of an additive. The particle size of tungsten carbide in the matrix is ​​5μm-10μm, and the binder includes four elements of Fe, Co, Ni and Cr in a molar ratio of 1:1:1:1.

[0177] The additives include 2wt.% of strengthening elements and 1wt.% of rare earth elements, wherein the strengthening element is tantalum and the rare earth element is La.

[0178] The preparation method of hard tungsten carbide alloy comprises the following steps:

[0179] S1. Prepare first hard particles.

[0180] S1 includes the following steps:

[0181] S11. Weigh the raw materials tungsten carbide powder and cobalt powder according to the composition ratio.

[0182] S12, ball-milling the tungsten carbide powder and the cobalt powder to obtain a first mixed powder, wherein the ball-to-material ratio of the ball milling is 5:1 and the ball milling time is 40 hours.

[0183] S13, pressing the first mixed powder into a shape, and then sintering the mixture at 1420° C. under the protection of an inert gas to obtain a first sintered product.

[0184] S14, crushing the first sintered product, ball milling, sieving, and flattening the product to obtain first hard particles.

[0185] S2. preparing second hard particles.

[0186] S2 includes the following steps:

[0187] S21. Weigh flat raw materials of tungsten powder, cobalt powder and titanium carbide powder according to the proportion of the components. The tungsten powder is flattened for 40 hours under the condition that the ratio of the hard alloy ball to the material is 5:1.

[0188] S22, tungsten powder and graphite powder are mixed evenly, the weight of graphite powder is 5wt.% of the mass of tungsten powder, and pre-sintered under inert gas protection at 1100°C for 1 hour to obtain prefabricated plate-shaped tungsten carbide.

[0189] S23, ball-milling the prefabricated plate-shaped tungsten carbide, activated carbon powder, titanium carbide powder and cobalt powder to obtain a second mixed powder. The ball-to-material ratio is 6:1, and the ball milling time is 30 hours. The second mixed powder is pressed into a shape and sintered at a temperature of 1400° C. for 1 hour to obtain a second sintered product.

[0190] S24, crushing the second sintered product, ball milling it, and sieving it to obtain second hard particles.

[0191] S3, preparing a matrix raw material, adding the first hard particles and the second hard particles into the matrix raw material and mixing them evenly, pressing and forming, and then sintering to obtain a hard tungsten carbide alloy blank.

[0192] S3 includes the following steps:

[0193] S31. Fe, Co, Ni and Cr powders are weighed according to the component ratio and mixed evenly by ball milling to obtain binder powder. The ball-to-material ratio of the ball milling is 10:1 and the ball milling time is 40 hours.

[0194] S32, the binder powder is mixed with tungsten carbide powder, titanium, tantalum, niobium powder and rare earth nitrate solution, and ball milled to obtain a matrix raw material. The ball-to-material ratio of the ball milling is 5:1, and the ball milling time is 4 hours. After ball milling, the matrix raw material is dried under the drying condition of 60° C. in a vacuum drying oven for 20 hours.

[0195] S33, adding the first hard particles and the second hard particles to the matrix raw material, ball milling and mixing, pressing and forming, sintering in a spark plasma sintering furnace, and cooling to obtain a hard tungsten carbide alloy blank. The sintering temperature is 1400°C, the sintering time is 20 minutes, and the sintering pressure is 40MPa.

[0196] S4. Heat-treating the cemented tungsten carbide alloy blank to obtain cemented tungsten carbide alloy.

[0197] The heat treatment temperature is 1200°C and the heat treatment time is 6 hours.

[0198] Comparative Example 1

[0199] The difference between this comparative example and Example 3 is that the tungsten carbide alloy in this example does not contain the second hard particles, and 75wt.% of the first hard particles are added to the tungsten carbide matrix.

[0200] Comparative Example 2

[0201] The difference between this comparative example and Example 3 is that the tungsten carbide alloy in this example does not contain the first hard particles, and 75wt.% of the second hard particles are added to the tungsten carbide matrix.

[0202] The Rockwell hardness, fracture toughness and flexural strength of Examples 1-3 and Comparative Examples 1-2 were tested. The fracture toughness was tested according to the cemented carbide fracture toughness standard ISO28079-2009, the hardness was tested according to GBT3849.1-2015 Cemented Carbide Rockwell Hardness (A Scale) Part 1: Experimental Method, and the flexural strength was tested using the GBT3851-2015 Cemented Carbide Transverse Fracture Strength Determination Method.

[0203] ;

[0204] Therefore, the hard tungsten carbide alloy and the preparation method thereof described in the present invention can improve the hardness and toughness of the tungsten carbide alloy.

[0205] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A hard tungsten carbide alloy, characterized in that: The invention comprises a matrix, wherein first hard particles and second hard particles are distributed inside the matrix, the second hard particles are filled between the first hard particles, the first hard particles are plate-like structures, and the second hard particles are spherical structures, and the matrix comprises tungsten carbide, a binder and an additive; The mass percentage of the first hard particles added is 10wt.%-20wt.%, the length of the first hard particles is 50μm-60μm, and the length:width of the first hard particles is 1:(0.6-0.8); the first hard particles include 80wt.%-90wt.% tungsten carbide and 10wt.%-20wt.% cobalt by mass percentage; The mass percentage of the second hard particles added is 50wt.%-60wt.%, and the particle size of the second hard particles is 10μm-20μm; the second hard particles include 90wt.%-95wt.% of tungsten carbide, 5wt.%-10wt.% of cobalt and 1wt.%-2wt.% of titanium carbide; The matrix comprises 70wt.%-80wt.% of tungsten carbide, 15wt.%-25wt.% of a binder and 3wt.%-5wt.% of an additive; the particle size of the tungsten carbide in the matrix is ​​5μm-10μm, and the binder comprises four elements of Fe, Co, Ni and Cr in a molar ratio of 1:1:1:1; The additive includes a strengthening element with a mass percentage of 2wt.%-4.5wt.% and a rare earth element with a mass percentage of 0.5wt.%-1wt.%, wherein the strengthening element is one or a mixture of several of titanium, tantalum and niobium, and the rare earth element is one or a mixture of two of La and Ce; The preparation method of the above-mentioned hard tungsten carbide alloy comprises the following steps: S1, preparing first hard particles; S2, preparing second hard particles; S3, preparing a matrix raw material, adding the first hard particles and the second hard particles into the matrix raw material, mixing them evenly, pressing and then sintering to obtain a hard tungsten carbide alloy blank; S4, heat treating the hard tungsten carbide alloy blank to obtain a hard tungsten carbide alloy; The S1 comprises the following steps: S11, weighing raw material tungsten carbide powder and cobalt powder according to the composition ratio; S12, mixing tungsten carbide powder and cobalt powder by ball milling to obtain a first mixed powder; S13, pressing the first mixed powder into a shape and then sintering the mixture at a temperature of 1400° C. to 1500° C. under the protection of an inert gas to obtain a first sintered product; S14, crushing the first sintered product, ball milling, sieving, and flattening the product to obtain first hard particles; The S2 comprises the following steps: S21, weighing flat raw material tungsten powder, cobalt powder and titanium carbide powder according to the composition ratio; S22, mixing tungsten powder and graphite powder evenly, wherein the weight of graphite powder is 5wt.%-6wt.% of the mass of tungsten powder; and pre-sintering under inert gas protection at a temperature of 1000°C-1100°C to obtain prefabricated plate-shaped tungsten carbide; S23, ball-milling and mixing the prefabricated plate-shaped tungsten carbide, activated carbon powder, titanium carbide powder and cobalt powder to obtain a second mixed powder, pressing the second mixed powder into a mold and sintering it at a temperature of 1400° C. to 1500° C. to obtain a second sintered product; S24, crushing the second sintered product, ball milling it, and sieving it to obtain second hard particles; In the step S4, the heat treatment temperature is 1200° C.-1300° C., and the heat treatment time is 4 hours-6 hours.

2. A cemented tungsten carbide alloy according to claim 1, characterized in that: The S3 comprises the following steps: S31, weighing Fe, Co, Ni and Cr powders according to the component ratio, and mixing them uniformly by ball milling to obtain a binder powder; S32, mixing and ball-milling the binder powder with tungsten carbide powder, a mixed powder of one or more of titanium, tantalum and niobium, and a rare earth nitrate solution to obtain a matrix raw material; S33, adding the first hard particles and the second hard particles into the matrix raw material, ball milling and mixing them evenly, pressing and forming, sintering in a spark plasma sintering furnace, and obtaining a hard tungsten carbide alloy blank after cooling.