A super coarse hard alloy material with excellent bending resistance and impact toughness, a preparation method and applications thereof

Abstract

The present application relates to the technical field of alloy material, in particular to a kind of super coarse hard alloy material with excellent bending resistance and impact toughness, preparation method and application thereof.The method sequentially constructs the sandwiched structure of high-phosphorus-cobalt (containing cerium)-low-phosphorus by cobalt / cerium co-deposition and wet-on-wet chemical plating containing catechol / phosphonic acid bifunctional molecules, to realize the super coarse hard alloy with dense structure and uniform grain.The structure realizes the graded release of interface energy and the dispersion distribution of bonding phase during sintering process, significantly improves the bending strength and impact toughness, maintains high hardness and magnetic stability, and has excellent structural integrity and fatigue resistance, so the prepared material is suitable for high-load impact and wear-resistant fields, and can be widely used in the manufacture of cutting tools, molds, mining equipment and military aerospace structural parts.

Description

Technical Field

[0001] This invention relates to the field of alloy materials technology, specifically to an ultra-coarse hard alloy material with excellent bending resistance and impact toughness, its preparation method, and its applications. Background Technology

[0002] Due to its high hardness, high wear resistance, and compressive strength, cemented carbide is widely used in cutting tools, molds, mining, and wear-resistant components. With the rapid development of manufacturing and the rising cost of tungsten carbide raw materials, recycling waste cutting tools and cemented carbide powder has become an important direction for raw material supply. However, recycled powder inevitably suffers from oxidation, decarburization, and cobalt phase migration during high-temperature welding, use, and wear. The surface has an uneven oxide layer and cobalt-poor and cobalt-rich regions. These structural defects lead to reduced wettability of the binder phase, poor interfacial bonding, and uneven microstructure during resintering, resulting in problems such as decreased strength, insufficient impact toughness, and fluctuating reliability of the material.

[0003] Existing technologies often employ methods such as acid pickling for deoxidation, single hydrogen reduction, or nickel plating pretreatment to improve the surface condition of recycled powder. However, acid pickling often leads to grain boundary corrosion and incomplete oxide film removal, while a single coating structure struggles to simultaneously control the interfacial composition gradient and stress distribution, typically resulting in localized deplating or cobalt phase re-agglomeration. Furthermore, traditional electroless plating or co-deposition processes, primarily using monolayers of metallic Ni or Co, lack selective coordination and chemical bridging capabilities with the WC surface. This results in a loose transition layer between the binder phase and carbide interface, which easily forms pores or brittle interfaces after high-temperature sintering, failing to meet the requirement of simultaneously improving toughness and strength for ultra-coarse-grained structures. Moreover, coarse-grained structures also easily lead to brittle fracture initiating at grain boundaries or discontinuous phase boundaries. Especially in recycled powder reuse systems, grain growth and interfacial weakening are superimposed, resulting in a significant decrease in toughness.

[0004] To address the aforementioned issues, a core technical problem urgently needing to be solved in this field is how to systematically establish a composite interface structure on the surface of recycled cemented carbide powder that combines reduction activity, wetting regulation, and stress gradient coordination, thereby eliminating oxidation differences and optimizing the diffusion path of the binder phase to achieve a synergistic improvement in strength and toughness. Summary of the Invention

[0005] In view of this, the purpose of this invention is to propose an ultra-coarse cemented carbide material with excellent bending resistance and impact toughness, its preparation method and its application, so as to solve the problems of interface weakening caused by surface oxidation and uneven distribution of cobalt phase in recycled cemented carbide and the difficulty in achieving both strength and toughness.

[0006] To achieve the above objectives, the present invention provides a method for preparing an ultra-coarse cemented carbide material with excellent bending resistance and impact toughness, comprising the following steps: S1 Preparation of pre-reduced mixed powder: The recovered cemented carbide powder from the cutting block is mixed with tungsten carbide powder, dispersed and dried with anhydrous ethanol and oleic acid, and then reduced at 400-450℃ for 60-90 min in a hydrogen atmosphere. After cooling, the pre-reduced mixed powder is obtained. S2 Seed Layer Powder Preparation: The pre-reduced mixed powder was dispersed in a deionized aqueous solution containing cobalt chloride hexahydrate and cerium chloride heptahydrate, the pH was adjusted to 9, and the mixture was reacted at 25-30℃ for 30-40 min. After filtration, washing and drying, the powder was reduced at 400-450℃ for 60-90 min under a hydrogen atmosphere to obtain the seed layer powder. S3 First chemical plating treatment: In plating solution A containing nickel sulfate hexahydrate, sodium hypophosphite monohydrate, lactic acid and thiourea, the seed layer powder is chemically plating at 80-84℃ for 25-30 minutes, and a catechol / phosphonic acid bifunctionalized product is added at the 5th minute of the reaction. S4 Cobalt-Cerium Co-deposition and Second Chemical Plating: The powder that has undergone the first chemical plating is placed in a co-deposition solution containing cobalt chloride hexahydrate and cerium chloride heptahydrate, reacted at 25-30℃ for 30-40 min, reduced in a hydrogen atmosphere at 400-450℃ for 60-90 min, and then transferred to plating solution B containing nickel sulfate hexahydrate, sodium hypophosphite monohydrate, lactic acid and thiourea, and then chemically plated at 80-84℃ for 15-20 min to obtain a seed layer powder with a sandwich structure on the surface; Preparation and sintering of S5 modified raw material powder: The sandwich structure powder was co-deposited again in the co-deposition solution and chemically plated in plating solution B for 10 min. Then, electrolytic cobalt powder and organic additives were added and wet-milled. After spray granulation, dewaxing at 350-550℃ for 120 min, and sintering and cooling were carried out at 1400-1500℃ with a pressure of 5MPa for 45 min to obtain ultra-coarse cemented carbide material. The catechol / phosphonic acid bifunctionalized product mentioned in step S3 is obtained by hydrolyzing and condensing triaminopropylmethoxysilane to generate octaaminopropylsilsesquioxane, which is then reacted with levodopa to obtain a catechol grafting intermediate, followed by reaction with phosphorous acid and formaldehyde.

[0007] Preferably, the mass ratio of recycled cemented carbide powder to tungsten carbide powder in step S1 is 7:3.

[0008] Preferably, in step S1, the amounts of anhydrous ethanol and oleic acid used are 10000 mL and 9-11 g, respectively.

[0009] Preferably, the reducing gas in step S1 is hydrogen gas with a flow rate of 10 L / min.

[0010] Preferably, the particle size of the recycled cemented carbide powder in step S1 is D10 15-20μm, D50 22-30μm, and D90 40-55μm; the composition is Co: 12.0wt%±0.5wt%, free carbon: 0.10wt%-0.40wt%, Zn: 0.01wt%-0.05wt%, and Ca≤0.03wt%.

[0011] Preferably, the tungsten carbide powder in step S1 has a particle size of D10 of 20-25 μm, D50 of 32-34 μm, D90 of 45-50 μm, and a specific surface area BET of 0.2-0.5 m². 2 / g.

[0012] Preferably, in step S2, the amounts of cobalt chloride hexahydrate, cerium chloride heptahydrate, and deionized water are 110-134g, 13.5-16.5g, and 100L, respectively.

[0013] Preferably, the plating solution A in step S3 comprises: 1800-2200g of nickel sulfate hexahydrate, 3000-3400g of sodium hypophosphite monohydrate, 1800-2200g of lactic acid, and 0.2g of thiourea.

[0014] Preferably, the amount of the catechol / phosphonic acid bifunctionalized product used in step S3 is 9-11g.

[0015] Preferably, in step S4, the amounts of cobalt chloride hexahydrate, cerium chloride heptahydrate, and deionized water in the co-deposition solution are 110-134g, 13.5-16.5g, and 100L, respectively.

[0016] Preferably, the plating solution B in step S4 comprises: 1800-2200g of nickel sulfate hexahydrate, 800-1000g of sodium hypophosphite monohydrate, 1800-2200g of lactic acid, and 0.18-0.22g of thiourea.

[0017] Preferably, the particle size D50 of the electrolytic cobalt powder in step S5 is 2-4 μm.

[0018] Preferably, in step S5, the amounts of the sandwich-structured powder and the electrolytic cobalt powder are 10000g and 150g, respectively.

[0019] Preferably, the preparation steps of the catechol / phosphonic acid bifunctionalized product are as follows: Triaminopropylmethoxysilane, anhydrous acetonitrile, anhydrous propanol and tetrabutylammonium hydroxide are mixed, deionized water is added dropwise, and the mixture is stirred and refluxed at 80°C for 200-240 min. After solvent removal and vacuum drying, octaaminopropylsilsesquioxane is obtained. Subsequently, it is dissolved in a mixed solvent of deionized water and ethanol, the pH is adjusted to 9, levodopa is added, and the mixture is stirred at 25°C for 120 min to obtain a catechol grafting intermediate. The intermediate is dispersed in glacial acetic acid, phosphorous acid and formaldehyde are added, and the mixture is reacted at 85-95°C for 300-360 min. After rotary evaporation to remove acid, ethanol precipitation and drying, the catechol / phosphonic acid bifunctionalized product is obtained.

[0020] Preferably, in step S3, the amounts of octaaminopropylsilsesquioxane, levodopa, phosphorous acid, and formaldehyde solution are 45-55g, 54-66g, 72-88g, and 108-132mL, respectively.

[0021] Furthermore, the present invention also provides an ultra-coarse cemented carbide material with excellent bending resistance and impact toughness.

[0022] Furthermore, the present invention also provides an application of an ultra-coarse cemented carbide material with excellent bending resistance and impact toughness for the manufacture of cutting tools, molds, mining equipment, and military and aerospace structural components.

[0023] The beneficial effects of this invention are: This invention utilizes a cobalt / cerium seed layer and a self-catalytic reduction center formed by hydrogen reduction treatment. This effectively removes residual oxide film from the powder surface and suppresses the energy difference between the carbide and binder phase interfaces. This allows the metal phase to penetrate, diffuse, and solidify during sintering, resulting in a smoother energy release pathway at the interface. It also enhances the stability of the cobalt phase grain boundaries and improves the interfacial bonding strength and densification.

[0024] This invention utilizes a multi-layer sandwich structure to achieve both stress gradient matching and diffusion coordination during microstructure evolution: the high-phosphorus layer serves as a Ni-P-rich amorphous layer, the intermediate cobalt-cerium layer generates fine and dispersed eutectoid phases at high temperatures, and the low-phosphorus layer forms a more ductile Ni-Co solid solution after sintering. The gradient stress structure formed by the multi-layer coating can induce the gradual release of sintering stress. During crack propagation, the cracks are deflected and bridged due to the interlacing of phase interfaces and the presence of elasto-plastic deformation zones, thus achieving energy dispersion and absorption at the microscopic level and significantly reducing the tendency for brittle fracture.

[0025] This invention introduces bifunctional molecules through a wet-to-wet method. The strong coordination of phosphonic acid groups with metal ions selectively guides the nucleation sites of nickel and cobalt, while the catechol groups provide additional hydrogen bonding and interfacial stabilization, making the chemical connection between adjacent metal layers more compact. The deposition reaction during the electroless plating process can proceed continuously, avoiding the problem of interlayer debonding caused by interrupted drying.

[0026] The method of this invention not only improves the strength, toughness and microstructure stability of cemented carbide, but also has good process adaptability and scalability, providing reliable technical support for the high-performance remanufacturing of recycled cemented carbide powder. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0028] The properties or sources of the raw materials used in the embodiments and comparative examples of this invention are as follows: Recycled cemented carbide powder for cutting tools: Particle size D10 15-20μm, D50 22-30μm, D90 40-55μm; Composition: WC 87wt%-88wt%; Co 12.0wt%±0.5wt%, Free carbon 0.10wt%-0.40wt%, Zn 0.01wt%-0.05wt%, Ca≤0.03wt%; Tungsten carbide powder: Particle size D10 20-25μm, D50 32-34μm, D90 45-50μm, Specific surface area BET 0.2-0.5m². 2 / g; Electrolytic cobalt powder: particle size D50 is 2-4μm.

[0029] Example 1: An ultra-coarse cemented carbide material with excellent bending resistance and impact toughness, the specific preparation steps are as follows: (1) Take 140g of triaminopropylmethoxysilane, 600mL of anhydrous acetonitrile, 140mL of anhydrous propanol and 2.8g of tetrabutylammonium hydroxide and add them to a glass reaction vessel. Add 140mL of deionized water dropwise and stir and reflux at 80℃ for 200min. After the reaction is completed, remove the solvent under reduced pressure, recrystallize with ethanol, and dry under vacuum at 60℃ to obtain octaaminopropylsilsesquioxane. (2) Dissolve 45g of octaaminopropylsilsesquioxane in a mixed solvent of 1800mL deionized water and 1800mL ethanol, add ammonia to adjust the pH to 9, add 54g of levodopa, bubble with air and stir at 25℃ for 120min to obtain a catechol grafting intermediate; disperse the intermediate in 1800mL glacial acetic acid, add 72g of phosphorous acid and 108mL of formaldehyde solution (37%), react at 85℃ for 300min, remove acid by rotary evaporation, precipitate with ethanol, and dry under vacuum at 60℃ to obtain a catechol / phosphonic acid bifunctionalized product; (3) Take 7000g of the recovered cemented carbide powder and 3000g of tungsten carbide powder, mix them and put them into a polypropylene barrel, add 10000mL of anhydrous ethanol and 9g of oleic acid, stir with a paddle for 30min and then filter, vacuum dry at 60℃ for 120min, then transfer the obtained product to a tube furnace, reduce it at 400℃ for 60-90min with a hydrogen flow rate of 10L / min, a heating rate of 5℃ / min, and then cool it to <80℃ to obtain a pre-reduced mixed powder; (4) Add 100L of deionized water to the polypropylene tank, add 10000g of pre-reduced mixed powder, stir mechanically at 300rpm, add 110g of cobalt chloride hexahydrate and 13.5g of cerium chloride heptahydrate, stir and disperse evenly, add ammonia water to adjust the pH to 9, react at 25℃ for 30min, let stand, filter and wash with water, dry at 80℃ for 60min, and finally in a tube furnace, pass hydrogen at 10L / min and reduce at 400℃ for 60min to obtain seed layer powder; (5) Add 100L of deionized water to the polypropylene tank, dissolve 1800g of nickel sulfate hexahydrate and 3000g of sodium hypophosphite monohydrate in sequence, then add 1800g of lactic acid (85%), add ammonia water to adjust the pH to 9, add 0.2g of thiourea, keep the temperature at 80℃ to obtain plating solution A, add 10000g of seed layer powder to it, stir at 80℃ for 25min for chemical plating, and add 9g of catechol / phosphonic acid bifunctional product at the 5th minute. Then filter the obtained reaction solution and transfer it to the coprecipitation tank, add 100L of deionized water, 110g of cobalt chloride hexahydrate and 13.5g of cerium chloride heptahydrate, stir and disperse evenly to form a coprecipitation solution, add ammonia water to adjust the pH to 9, react at 25℃ for 30min, let stand, filter and wash with water, dry at 80℃ for 60min, and finally in a tube furnace, pass hydrogen at 10L / min and reduce at 400℃ for 60min. (6) Add 100L of deionized water to the polypropylene tank, dissolve 1800g of nickel sulfate hexahydrate and 800g of sodium hypophosphite monohydrate in sequence, then add 1800g of lactic acid (85%), add ammonia water to adjust the pH to 9, add 0.18g of thiourea, keep the temperature at 80℃ to obtain plating solution B, add 10000g of the product obtained in step (5) to it, stir at 80℃ for 15min to chemically plating, and obtain seed layer powder with sandwich sandwich structure on the surface; (7) 10,000 g of seed layer powder with a sandwich structure on the surface was placed again in 100 L of deionized water with pH 9 containing 110 g of cobalt chloride hexahydrate and 13.5 g of cerium chloride heptahydrate for co-deposition. The reaction was carried out at 25 °C for 30 min, dried at 80 °C for 60 min, and then reduced at 400 °C for 60 min by introducing hydrogen at 10 L / min in a tube furnace. After that, it was added to plating solution B and chemically plated at 80 °C for 10 min to obtain modified raw material powder. (8) Add 1620mL of anhydrous ethanol, 180g of paraffin wax and 9g of oleic acid to a horizontal ball mill and run it idle for 120min; add 10000g of modified raw material powder and 150g of electrolytic cobalt powder, wet mill for 720min to obtain a slurry, then transfer it to a spray granulator for granulation, and finally dewax it in hydrogen at 350℃ for 120min, raise it to 1400℃ and apply 5MPa for 45min; lower it to <900℃ to depressurize and cool it out of the furnace to obtain ultra-coarse hard alloy material, wherein the inlet temperature of the spray granulation is 200℃ and the outlet temperature is 90℃.

[0030] Example 2: An ultra-coarse cemented carbide material with excellent bending resistance and impact toughness, the specific preparation steps are as follows: (1) Take 160g of triaminopropylmethoxysilane, 640mL of anhydrous acetonitrile, 160mL of anhydrous propanol and 3.2g of tetrabutylammonium hydroxide and add them to a glass reaction vessel. Add 150mL of deionized water dropwise and stir and reflux at 80℃ for 220min. After the reaction is completed, remove the solvent under reduced pressure, recrystallize with ethanol, and dry under vacuum at 60℃ to obtain octaaminopropylsilsesquioxane. (2) Dissolve 50g of octaaminopropylsilsesquioxane in a mixed solvent of 2000mL deionized water and 2000mL ethanol, add ammonia to adjust the pH to 9, add 60g of levodopa, bubble with air and stir at 25℃ for 120min to obtain a catechol grafting intermediate; disperse the intermediate in 2000mL glacial acetic acid, add 80g of phosphorous acid and 120mL of formaldehyde solution (37%), react at 90℃ for 330min, remove acid by rotary evaporation, precipitate with ethanol, and dry under vacuum at 60℃ to obtain a catechol / phosphonic acid bifunctionalized product; (3) Take 7000g of recovered cemented carbide powder and mix it with 3000g of tungsten carbide powder. Then put it into a polypropylene barrel, add 10000mL of anhydrous ethanol and 10g of oleic acid, stir with a paddle for 50min and filter. Dry it under vacuum at 60℃ for 120min. Then transfer the obtained product to a tube furnace and reduce it at 430℃ for 80min with a hydrogen flow rate of 10L / min, a heating rate of 5℃ / min and a hydrogen flow rate of 5℃ / min. Cool it to <80℃ to obtain a pre-reduced mixed powder. (4) Add 100L of deionized water to the polypropylene tank, add 10000g of pre-reduced mixed powder, stir mechanically at 300rpm, add 121g of cobalt chloride hexahydrate and 15g of cerium chloride heptahydrate, stir and disperse evenly, add ammonia water to adjust the pH to 9, react at 30℃ for 35min, let stand, filter and wash with water, dry at 80℃ for 60min, and finally in a tube furnace, pass hydrogen at 10L / min and reduce at 430℃ for 80min to obtain seed layer powder; (5) Add 100L of deionized water to the polypropylene tank, dissolve 2000g of nickel sulfate hexahydrate and 3200g of sodium hypophosphite monohydrate in sequence, then add 2000g of lactic acid (85%), add ammonia water to adjust the pH to 9, add 0.2g of thiourea, keep the temperature at 82℃ to obtain plating solution A, add 10000g of seed layer powder to it, stir at 82℃ for 30min for chemical plating, and add 10g of catechol / phosphonic acid bifunctional product at the 5th minute. Then filter the obtained reaction solution and transfer it to the coprecipitation tank, add 100L of deionized water, 121g of cobalt chloride hexahydrate and 15g of cerium chloride heptahydrate, stir and disperse evenly to form a coprecipitation solution, add ammonia water to adjust the pH to 9, react at 30℃ for 35min, let stand, filter and wash with water, dry at 80℃ for 60min, and finally in the tube furnace, pass hydrogen at 10L / min and reduce at 430℃ for 80min. (6) Add 100L of deionized water to the polypropylene tank, dissolve 2000g of nickel sulfate hexahydrate and 900g of sodium hypophosphite monohydrate in sequence, then add 2000g of lactic acid (85%), add ammonia water to adjust the pH to 9, add 0.20 thiourea, keep the temperature at 82℃ to obtain plating solution B, add 10000g of the product obtained in step (5) to it, stir and chemically plating at 82℃ for 18min to obtain seed layer powder with sandwich sandwich structure on the surface; (7) 10,000 g of seed layer powder with a sandwich structure on the surface was placed again in 100 L of deionized water with pH 9 containing 121 g of cobalt chloride hexahydrate and 15 g of cerium chloride heptahydrate for co-deposition. The reaction was carried out at 30 °C for 30 min, dried at 80 °C for 60 min, and then reduced at 430 °C for 80 min by introducing hydrogen gas at 10 L / min in a tube furnace. After that, it was added to plating solution B and chemically plated at 82 °C for 10 min to obtain modified raw material powder. (8) Add 1800mL of anhydrous ethanol, 200g of paraffin wax and 10g of oleic acid to a horizontal ball mill and run it idle for 120min; add 10000g of modified raw material powder and 150g of electrolytic cobalt powder and wet grind for 720min to obtain a slurry, then transfer it to a spray granulator for granulation, and finally dewax it in hydrogen at 450℃ for 120min, raise it to 1450℃ and apply 5MPa for 45min; lower it to <900℃ to depressurize and cool it out of the furnace to obtain ultra-coarse hard alloy material, wherein the inlet temperature of spray granulation is 200℃ and the outlet temperature is 90℃.

[0031] Example 3: An ultra-coarse cemented carbide material with excellent bending resistance and impact toughness, the specific preparation steps are as follows: (1) Take 180g of triaminopropylmethoxysilane, 680mL of anhydrous acetonitrile, 180mL of anhydrous propanol and 3.6g of tetrabutylammonium hydroxide and add them to a glass reaction vessel. Add 150mL of deionized water dropwise and stir and reflux at 80℃ for 240min. After the reaction is completed, remove the solvent under reduced pressure, recrystallize with ethanol, and dry under vacuum at 60℃ to obtain octaaminopropylsilsesquioxane. (2) Dissolve 55g of octaaminopropylsilsesquioxane in a mixed solvent of 2200mL deionized water and 2200mL ethanol, add ammonia to adjust the pH to 9, add 66g of levodopa, bubble with air and stir at 25℃ for 120min to obtain a catechol grafting intermediate; disperse the intermediate in 2200mL glacial acetic acid, add 88g of phosphorous acid and 132mL of formaldehyde solution (37%), react at 95℃ for 360min, remove acid by rotary evaporation, precipitate with ethanol, and dry under vacuum at 60℃ to obtain a catechol / phosphonic acid bifunctionalized product; (3) Take 7000g of the recovered cemented carbide powder and 3000g of tungsten carbide powder, mix them and put them into a polypropylene barrel, add 10000mL of anhydrous ethanol and 11g of oleic acid, stir with a paddle for 60min and then filter, vacuum dry at 60℃ for 120min, then transfer the obtained product to a tube furnace, reduce it at 450℃ for 90min with a hydrogen flow rate of 10L / min, a heating rate of 5℃ / min, and cool it to <80℃ to obtain a pre-reduced mixed powder; (4) Add 100L of deionized water to the polypropylene tank, add 10000g of pre-reduced mixed powder, stir mechanically at 300rpm, add 134g of cobalt chloride hexahydrate and 16.5g of cerium chloride heptahydrate, stir and disperse evenly, add ammonia water to adjust the pH to 9, react at 30℃ for 40min, let stand, filter and wash with water, dry at 80℃ for 60min, and finally in a tube furnace, pass hydrogen at 10L / min and reduce at 450℃ for 90min to obtain seed layer powder; (5) Add 100L of deionized water to the polypropylene tank, dissolve 2200g of nickel sulfate hexahydrate and 3400g of sodium hypophosphite monohydrate in sequence, then add 2200g of lactic acid (85%), add ammonia water to adjust the pH to 9, add 0.2g of thiourea, keep the temperature at 84℃ to obtain plating solution A, add 10000g of seed layer powder to it, stir and chemically plating at 84℃ for 30min, and add 11g of catechol / phosphonic acid bifunctional product at the 5th minute. Then filter the obtained reaction solution and transfer it to the coprecipitation tank, add 100L of deionized water, 134g of cobalt chloride hexahydrate and 16.5g of cerium chloride heptahydrate, stir and disperse evenly to form a coprecipitation solution, add ammonia water to adjust the pH to 9, react at 30℃ for 40min, let stand, filter and wash with water, dry at 80℃ for 60min, and finally reduce at 450℃ for 90min in a tube furnace with hydrogen gas introduced at 10L / min. (6) Add 100L of deionized water to the polypropylene tank, dissolve 2200g of nickel sulfate hexahydrate and 1000g of sodium hypophosphite monohydrate in sequence, then add 2200g of lactic acid (85%), add ammonia water to adjust the pH to 9, add 0.22g of thiourea, keep the temperature at 84℃ to obtain plating solution B, add 10000g of the product obtained in step (5) to it, stir at 84℃ for 20min to chemically plating, and obtain seed layer powder with sandwich sandwich structure on the surface; (7) 10,000 g of seed layer powder with a sandwich structure on the surface was placed again in 100 L of deionized water with pH 9 containing 134 g of cobalt chloride hexahydrate and 16.5 g of cerium chloride heptahydrate for co-deposition. The reaction was carried out at 30 °C for 30 min, dried at 80 °C for 60 min, and then reduced at 450 °C for 90 min by introducing hydrogen at 10 L / min in a tube furnace. After that, it was added to plating solution B and chemically plated at 84 °C for 10 min with stirring to obtain modified raw material powder. (8) Add 1980 mL of anhydrous ethanol, 220 g of paraffin wax and 11 g of oleic acid to a horizontal ball mill and run it idle for 120 min; add 10000 g of modified raw material powder and 150 g of electrolytic cobalt powder, wet mill for 720 min to obtain a slurry, then transfer it to a spray granulator for granulation, and finally dewax it in hydrogen at 550 °C for 120 min, raise it to 1500 °C and apply 5 MPa for 45 min; lower it to <900 °C to depressurize and cool it out of the furnace to obtain ultra-coarse hard alloy material, wherein the inlet temperature of the spray granulation is 200 °C and the outlet temperature is 90 °C.

[0032] Comparative Example 1: The difference from Example 2 is that co-deposition is not performed in step (4), while the other steps are the same as in Example 2.

[0033] Comparative Example 2: The difference from Example 2 is that in step (8), the modified raw material powder is replaced with seed layer powder with a sandwich structure on the surface, and the rest of the steps are the same as in Example 2.

[0034] Comparative Example 3: The difference from Example 2 is that in step (5), only chemical plating is performed in plating solution A, and in step (7), the seed layer powder with a sandwich structure on the surface is replaced with powder chemically plated in plating solution A. The remaining steps are the same as in Example 2.

[0035] Comparative Example 4: The difference from Example 2 is that the catechol / phosphonic acid bifunctionalized product is not added in step (5), and the other steps are the same as in Example 2.

[0036] Performance testing Grain size: determined according to GB / T6394-2017 "Method for Determination of Average Grain Size of Metals"; Hardness: Tested according to GB / T3849-2015 "Rockwell Hardness Test Method for Hard Alloys", using HRA scale, load 60kg, five points were measured at different parts of each sample and the average value was taken. Bending strength: Tested according to GB / T3851-2015 "Test Method for Transverse Fracture Strength (Bending Strength) of Cemented Carbide", the fracture strength of cemented carbide under uniaxial bending load was measured by three-point bending method. Impact toughness: The test was conducted according to GB / T1817-2017 "Determination of impact toughness of cemented carbide at room temperature". The sample size was 10mm×10mm×55mm. The test was conducted using a standard Charpy impact testing machine with a pendulum impact energy of 50J and an impact velocity of 5.2m / s. Magnetic saturation determination: The test method for determining magnetic saturation (MS) of cemented carbide is carried out according to GB / T 23369-2009. The sample (mass m) is placed in the magnetic saturation determination device, and the applied magnetic field is gradually increased with a high magnetic field strength (2400-3200 A / m). When the measured magnetization no longer changes with the increase of the magnetic field, the maximum magnetization value M is recorded. Magnetic saturation intensity Ms (emu / g) = M / m; Determination of coercivity: According to GB / T3848-2017, the sample is fully magnetized to saturation in an external magnetic field, and a reverse magnetic field is gradually applied to gradually reduce the magnetization intensity. When the magnetic flux density drops to zero, the intensity of the reverse magnetic field at this time is recorded as the coercivity Hc (unit: kA / m). Each sample is tested three times and the average value is taken. The test results are shown in Table 1.

[0037]

[0038] Data Analysis: As can be seen from the performance data of Examples 1-3 in Table 1, the ultra-coarse-grained cemented carbide material prepared by the present invention maintains a stable ultra-coarse grain size while exhibiting high and coordinated hardness, bending strength, and impact toughness. This indicates that the material has a dense structure, strong interfacial bonding, uniform cobalt phase distribution, stable magnetic saturation value, and intact chemical state of the binder phase. Under ultra-coarse-grained structure conditions, the material can still possess high hardness, high bending strength, and excellent impact toughness, effectively solving the problem of interfacial weakening caused by oxidation of the recycled powder surface and uneven cobalt distribution.

[0039] From the performance data of Example 2 and Comparative Example 1 in Table 1, it can be inferred that the cobalt / cerium co-deposition and hydrogen reduction process formed uniformly distributed metal cores and partially cerium-rich phases on the powder surface. These "self-catalyzing" reduction centers inhibited the continued existence of the oxide film on the surface of the recycled powder, allowing the surface energy of tungsten carbide to be released evenly, promoting the subsequent sintering densification process. At the same time, the directional adhesion and interlayer diffusion of the binder phase were achieved during the sintering process, forming a dense and continuous metal network structure, thereby mitigating the localized weakening of bonding caused by the oxidation differences on the surface of the recycled powder. In addition, the stable magnetic saturation value and increased coercivity also reflect that the cobalt distribution of the binder phase changed from a coarse island-like state to a fine and dispersed state, and a stable metallic transition layer was formed in the interface region, improving magnetic uniformity and structural integrity.

[0040] From the performance data changes of Example 2 and Comparative Examples 2 and 3 in Table 1, it can be inferred that the "double-pass" structure of the "sandwich interlayer" plays a significant role in microstructure regulation. This structure achieves multi-scale interface regulation and stress matching by alternately introducing a high-phosphorus layer, a cobalt (cerium-containing) intermediate layer, and a low-phosphorus layer during the coating formation process: the higher content of amorphous Ni-P phase in the high-phosphorus layer may improve the wettability of metallic nickel on the surface of WC particles, which helps to increase the liquid phase penetration rate and interface density in the early stage of sintering; the cobalt (cerium-containing) intermediate layer forms fine cobalt-cerium composite precipitates during hydrogen reduction, which transforms the cobalt phase into a uniformly dispersed distribution, thereby inhibiting the excessive aggregation and flow of liquid cobalt; while the low-phosphorus layer transforms into a Ni-Co solid solution region with higher toughness after sintering, forming a "flexible boundary" that can release residual stress, reducing the tendency of interface brittleness. The high coercivity and stable magnetic saturation also indicate that the cobalt distribution of the binder phase is refined and the chemical composition is not damaged.

[0041] A comprehensive analysis of the performance data from Example 2 and Comparative Example 4 in Table 1 suggests that the simultaneous "wet-to-wet" introduction of the catechol / phosphonic acid bifunctional molecules results in a coordinated improvement in both the mechanical and magnetic properties of the material. During the electroless plating process, the phosphonic acid groups, through strong coordination with nickel and cobalt ions, generate a directional adsorption effect on the WC surface, inducing metal deposition at high-energy sites to form a continuously covering adhesive phase film. Simultaneously, the catechol groups achieve uninterrupted molecular layer connection in the co-deposition environment via a "wet-to-wet" reaction, avoiding interfacial cracking caused by conventional drying or secondary activation. This molecular-level structural reconstruction causes cracks to be repeatedly deflected and slowed down at the interface, and stress is dispersed and absorbed, thus achieving a simultaneous improvement in strength and toughness on a macroscopic scale.

[0042] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention is limited to these examples; within the framework of the invention, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity.

Claims

1. A method for preparing an ultra-coarse cemented carbide material with excellent bending resistance and impact toughness, characterized in that, Includes the following steps: S1 Preparation of pre-reduced mixed powder: The recovered cemented carbide powder from the cutting block is mixed with tungsten carbide powder, wet-treated with anhydrous ethanol and oleic acid, dried and pre-reduced in a hydrogen atmosphere to obtain pre-reduced mixed powder. S2 Seed Layer Powder Preparation: The pre-reduced mixed powder was dispersed in a deionized aqueous solution containing cobalt chloride hexahydrate and cerium chloride heptahydrate for co-deposition, and the seed layer powder was obtained after reduction treatment; S3 First chemical plating treatment: The seed layer powder is chemically plating in plating solution A containing nickel sulfate hexahydrate, sodium hypophosphite monohydrate, lactic acid and thiourea for 25-30 minutes, and a catechol / phosphonic acid bifunctional product is added at the 5th minute of the reaction. S4 Cobalt-Cerium Co-deposition and Second Chemical Plating: The powder that has undergone the first chemical plating is placed in a co-deposition solution containing cobalt chloride hexahydrate and cerium chloride heptahydrate for co-deposition, and then transferred to plating solution B containing nickel sulfate hexahydrate, sodium hypophosphite monohydrate, lactic acid and thiourea for chemical plating for 15-20 minutes to obtain a seed layer powder with a sandwich structure on the surface. S5 modified raw material powder preparation and sintering: After the sandwich structure powder is co-deposited again by co-deposition liquid and chemically plated by plating solution B, electrolytic cobalt powder and organic additives are added and wet-milled, spray granulated, dewaxed, and sintered at 1400-1500℃ and 5MPa to obtain ultra-coarse hard alloy material. The catechol / phosphonic acid bifunctionalized product mentioned in step S3 is obtained by hydrolyzing and condensing triaminopropylmethoxysilane to generate octaaminopropylsilsesquioxane, which is then reacted with levodopa to obtain a catechol grafting intermediate, followed by reaction with phosphorous acid and formaldehyde.

2. The preparation method according to claim 1, characterized in that, In step S1, the mass ratio of recovered cemented carbide powder to tungsten carbide powder is 7:3; the amounts of anhydrous ethanol and oleic acid used are 10000 mL and 9-11 g, respectively.

3. The preparation method according to claim 1, characterized in that, In step S2, the amounts of cobalt chloride hexahydrate, cerium chloride heptahydrate, and deionized water are 110-134g, 13.5-16.5g, and 100L, respectively.

4. The preparation method according to claim 1, characterized in that, The plating solution A mentioned in step S3 includes: 1800-2200g of nickel sulfate hexahydrate, 3000-3500g of sodium hypophosphite monohydrate, 1800-2200g of lactic acid, and 0.2g of thiourea.

5. The preparation method according to claim 1, characterized in that, The amount of the catechol / phosphonic acid bifunctionalized product used in step S3 is 9-11g.

6. The preparation method according to claim 1, characterized in that, In step S4, the amounts of cobalt chloride hexahydrate, cerium chloride heptahydrate, and deionized water in the co-precipitation solution are 110-134g, 13.5-16.5g, and 100L, respectively.

7. The preparation method according to claim 1, characterized in that, The plating solution B mentioned in step S4 includes: 1800-2200g of nickel sulfate hexahydrate, 800-1000g of sodium hypophosphite monohydrate, 1800-2200g of lactic acid and 0.18-0.22g of thiourea.

8. The preparation method according to claim 1, characterized in that, The amounts of octaaminopropylsilsesquioxane, levodopa, phosphorous acid, and formaldehyde solution used are 45-55g, 54-66g, 72-88g, and 108-132mL, respectively.

9. A type of ultra-coarse hard alloy material with excellent bending resistance and impact toughness, characterized in that, It is prepared according to any one of claims 1-8.

10. An application of the ultra-coarse cemented carbide material with excellent bending resistance and impact toughness according to claim 9, characterized in that, Used in the manufacture of cutting tools, molds, mining equipment, and military and aerospace structural components.

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