Super-coarse hard alloy material with excellent bending resistance and impact toughness, preparation method and application thereof

Abstract

The invention relates to the technical field of alloy materials, in particular to an ultra-thick hard alloy material with excellent bending resistance and impact toughness and a preparation method and application thereof. According to the method, through cobalt / cerium co-deposition and wet-to-wet chemical plating containing catechol / phosphonic acid bifunctional molecules, a high-phosphorus-cobalt (cerium-containing)-low-phosphorus sandwich structure is sequentially constructed, and the ultra-coarse hard alloy compact in structure and uniform in crystal grain is achieved. According to the structure, graded release of interface energy and dispersed distribution of a binding phase are achieved in the sintering process, the bending strength and impact toughness are remarkably improved, high hardness and magnetic stability are kept, excellent structural integrity and fatigue resistance are achieved, and the prepared material is suitable for the field of high-load impact and wear resistance and has wide application prospects. The method can be widely used for manufacturing cutters, molds, mining equipment and military aerospace structural members.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of alloy materials, in particular to a super coarse cemented carbide material with excellent bending resistance and impact toughness, a preparation method and application thereof. BACKGROUND

[0002] Cemented carbide is widely used in cutting tools, dies, mining and wear-resistant components due to its high hardness, wear resistance and compressive strength. With the rapid development of manufacturing industry and the rising cost of tungsten carbide raw materials, recycling waste cutting tools and cemented carbide powders has become an important direction of raw material supply. However, the recycled powders inevitably suffer from oxidation, decarburization and cobalt phase migration during high-temperature welding, use and wear, resulting in uneven oxidation layer and cobalt-poor and cobalt-rich regions on the surface. These structural defects lead to poor wetting of the binder phase, poor interfacial bonding and uneven microstructure during resintering, thereby causing problems such as strength reduction, insufficient impact toughness and reliability fluctuations.

[0003] Existing technologies mainly use pickling to remove oxygen, single hydrogen reduction or nickel plating pretreatment to improve the surface state of recycled powders. However, pickling treatment often causes grain boundary corrosion and incomplete removal of the oxidation film, and single plating layer structure cannot simultaneously control the interfacial composition gradient and stress distribution, often resulting in local plating loss or cobalt phase re-deposition. In addition, traditional chemical plating or co-deposition processes mainly use single-layer metal Ni or Co, which lacks the ability to selectively coordinate and chemically bridge with the WC surface, resulting in a loose transition layer between the binder phase and the carbide interface, which is prone to form pores or brittle interfaces after high-temperature sintering, and cannot meet the demand for simultaneous improvement of toughness and strength in super coarse grain structure. Moreover, coarse grain structure also easily leads to brittle fracture starting from the grain boundary or phase boundary discontinuous region. Especially in the recycling system of recycled powders, grain growth and interface weakening superimpose each other, resulting in a significant decrease in toughness.

[0004] To solve the above problems, it is necessary to systematically establish a composite interface structure on the surface of recycled cemented carbide powder, which has both reduction activity, wetting regulation and stress gradient coordination, can eliminate oxidation differences and optimize the diffusion path of the binder phase, and realize the simultaneous improvement of strength and toughness. SUMMARY

[0005] Therefore, the present application aims to provide a super coarse cemented carbide material with excellent bending resistance and impact toughness, a preparation method and application thereof, to solve the problem of interface weakening and difficulty in balancing strength and toughness caused by uneven oxidation and cobalt phase distribution on the surface of recycled cemented carbide.

[0006] To achieve the above purpose, the present application provides a preparation method of a super coarse cemented carbide material with excellent bending resistance and impact toughness, comprising the following steps: S1 preparation of pre-reduction mixed powder: mix the tool bit recycled cemented carbide powder with tungsten carbide powder, disperse in anhydrous ethanol and oleic acid, dry, and then reduce at 400-450℃ for 60-90min under hydrogen atmosphere to obtain the pre-reduction mixed powder; S2 seed layer powder preparation: disperse the pre-reduction mixed powder in a deionized water solution containing cobalt chloride hexahydrate and cerium chloride heptahydrate, adjust the pH to 9, react at 25-30℃ for 30-40min, then filter, wash, dry, and reduce at 400-450℃ for 60-90min under hydrogen atmosphere to obtain the seed layer powder; S3 first chemical plating treatment: chemical plate the seed layer powder in plating solution A containing nickel sulfate hexahydrate, sodium hypophosphite monohydrate, lactic acid, and thiourea at 80-84℃ for 25-30min, and add catechol / phosphonic acid bifunctional product at the 5th min of the reaction; S4 cobalt-cerium co-deposition and second chemical plating: place the powder after the first chemical plating in a co-deposition solution containing cobalt chloride hexahydrate and cerium chloride heptahydrate, react at 25-30℃ for 30-40min, then reduce at 400-450℃ for 60-90min under hydrogen atmosphere, and transfer to plating solution B containing nickel sulfate hexahydrate, sodium hypophosphite monohydrate, lactic acid, and thiourea for chemical plating at 80-84℃ for 15-20min to obtain the seed layer powder with sandwich structure on the surface; S5 preparation and sintering of modified raw material powder: after co-deposition in the co-deposition solution and chemical plating in plating solution B for 10min, add electrolytic cobalt powder and organic additives for wet grinding, spray granulation, dewaxing at 350-550℃ for 120min, and sintering at 1400-1500℃ under 5MPa pressure for 45min to obtain the ultra-fine cemented carbide material; The catechol / phosphonic acid bifunctional product in step S3 is octakisaminopropylsilsesquioxane obtained by hydrolysis and condensation of trisaminopropylmethoxysilane, then reacted with levodopa to obtain a catechol grafted intermediate, and then reacted with phosphorous acid and formaldehyde.

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

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

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

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

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

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

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

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

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

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

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

[0018] Preferably, the amounts of sandwiched layer structure powder and electrolytic cobalt powder used in step S5 are 10000 g and 150 g, respectively.

[0019] Preferably, the catechol / phosphonic acid bifunctional product is prepared by mixing triaminopropylmethoxysilane, anhydrous acetonitrile, anhydrous propanol and tetrabutylammonium hydroxide, then adding deionized water dropwise, stirring and refluxing at 80°C for 200-240 min, removing the solvent and vacuum drying to obtain octaaminopropylsilsesquioxane; then dissolving the octaaminopropylsilsesquioxane in a mixed solvent of deionized water and ethanol, adjusting the pH to 9, adding levodopa, and stirring at 25°C for 120 min to obtain a catechol grafting intermediate; dispersing the intermediate in glacial acetic acid, adding phosphorous acid and formaldehyde, and reacting at 85-95°C for 300-360 min, then removing the acid by rotary evaporation, precipitating with ethanol and drying to obtain the catechol / phosphonic acid bifunctional product.

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

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

[0022] Further, the present application also provides an application of the ultra-coarse cemented carbide material with excellent bending resistance and impact toughness, which is used in the manufacture of cutting tools, molds, mining equipment and military aerospace structural parts.

[0023] The beneficial effects of the present application are as follows: The self-catalytic reduction center formed by the cobalt / cerium seed layer and hydrogen reduction treatment can effectively remove the residual oxide film on the surface of the powder and inhibit the energy difference at the carbide and binder phase interface, so that the metal phase uniformly penetrates, diffuses and stably combines during sintering, thereby making the interface energy release path smoother, strengthening the cobalt phase grain boundary stability, and improving the interface bonding strength and densification degree.

[0024] The multi-layer sandwich structure plays a dual role in stress gradient matching and diffusion coordination in the evolution of the structure: the high-phosphorus layer is a rich Ni-P amorphous layer, the intermediate cobalt-cerium layer generates fine and dispersed eutectoid phases at high temperature, and the low-phosphorus layer forms a Ni-Co solid solution with higher toughness after sintering. The gradient stress structure formed by the multi-layer coating can induce the sintering stress to be released step by step, and the cracks are deflected and bridged when propagating due to the existence of interfacial interlacing and elastic-plastic deformation zones, thereby dispersing and absorbing energy at the micro level and significantly reducing the tendency of brittle fracture.

[0025] The application uses a wet-on-wet introduction method of a bifunctional molecule, the strong coordination of phosphonic acid groups to metal ions selectively guides the nucleation position of nickel and cobalt, and the catechol group provides additional hydrogen bonding and interface stabilization, so that the chemical connection between adjacent metal layers is more compact, and the deposition reaction in the electroless plating process can be continuously carried out, avoiding the problem of interlayer debonding caused by interruption and drying.

[0026] The method of the application not only improves the strength, toughness and microstructure stability of the hard alloy, but also has good process adaptability and scalability, and can provide reliable technical support for high-performance remanufacturing of recycled hard alloy powder. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical scheme and advantages of the application clearer, the application will be further described in detail below with specific examples.

[0028] The properties or sources of the raw materials used in the examples and comparative examples of the application are as follows: The reclaimed hard alloy powder of the tool block has a particle size D10 of 15-20 mu m, a D50 of 22-30 mu m, and a D90 of 40-55 mu m; a 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 has a particle size D10 of 20-25 mu m, a D50 of 32-34 mu m, and a D90 of 45-50 mu m, and a specific surface area BET of 0.2-0.5m 2 / g; electrolytic cobalt powder has a particle size D50 of 2-4 mu m.

[0029] Example 1: A super-hard hard alloy 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 into a glass reaction kettle, add 140mL of deionized water dropwise, stir and reflux at 80℃ for 200min, after the reaction is completed, remove the solvent under reduced pressure, recrystallize with ethanol, and vacuum dry at 60℃ to obtain octaaminopropylsilsesquioxane; (2) Take 45g of octaaminopropylsilsesquioxane and dissolve it in 1800mL of a mixed solvent of deionized water and 1800mL of ethanol, adjust the pH to 9 by adding ammonia water, add 54g of levodopa, bubble with air, and stir at 25℃ for 120min to obtain a catechol grafted intermediate; disperse the intermediate in 1800mL of glacial acetic acid, add 72g of phosphorous acid and 108mL of formaldehyde solution (37%), react at 85℃ for 300min, remove the acid by rotary evaporation, precipitate with ethanol, and vacuum dry at 60℃ to obtain a catechol / phosphonic acid bifunctional product; (3) Put 7000 g cemented carbide powder recovered from the tool blocks and 3000 g tungsten carbide powder into a polypropylene barrel, add 10000 mL anhydrous ethanol and 9 g oleic acid, stir with a paddle for 30 min, then perform suction filtration, and dry at 60°C under vacuum for 120 min. Then transfer the obtained product to a tube furnace, reduce at 400°C under a hydrogen flow of 10 L / min at a heating rate of 5°C / min for 60-90 min, cool to <80°C, and obtain a pre-reduced mixed powder; (4) Add 100 L deionized water to a polypropylene tank, add 10000 g of the pre-reduced mixed powder, mechanically stir at 300 rpm, add 110 g of cobalt chloride hexahydrate and 13.5 g of cerium chloride heptahydrate, stir and disperse uniformly, then add ammonia water dropwise to adjust the pH to 9, react at 25°C for 30 min, stand, suction filter, wash with water, dry at 80°C for 60 min, and finally reduce in a tube furnace at 400°C under a hydrogen flow of 10 L / min for 60 min to obtain a seed layer powder; (5) Add 100 L deionized water to a polypropylene tank, dissolve 1800 g of nickel sulfate hexahydrate and 3000 g of sodium hypophosphite monohydrate in sequence, then add 1800 g of lactic acid (85%), dropwise add ammonia water to adjust the pH to 9, add 0.2 g of thiourea, and keep the temperature at 80°C to obtain plating solution A. Add 10000 g of the seed layer powder to it, stir at 80°C for 25 min, and at the 5th min, add 9 g of catechol / phosphonic acid bifunctional product. Then filter the obtained reaction solution and transfer it to a co-precipitation tank, add 100 L deionized water, 110 g of cobalt chloride hexahydrate and 13.5 g of cerium chloride heptahydrate, stir and disperse uniformly to form a co-deposition solution, then add ammonia water dropwise to adjust the pH to 9, react at 25°C for 30 min, stand, suction filter, wash with water, dry at 80°C for 60 min, and finally reduce in a tube furnace at 400°C under a hydrogen flow of 10 L / min for 60 min; (6) Add 100 L deionized water to a polypropylene tank, dissolve 1800 g of nickel sulfate hexahydrate and 800 g of sodium hypophosphite monohydrate in sequence, then add 1800 g of lactic acid (85%), dropwise add ammonia water to adjust the pH to 9, add 0.18 g of thiourea, and keep the temperature at 80°C to obtain plating solution B. Add 10000 g of the product obtained in step (5) to it, stir at 80°C for 15 min, and obtain a seed layer powder with a sandwich structure on the surface; (7) The 10000 g seed layer powder with a sandwich structure on the surface was again placed in 100 L deionized water with a pH of 9, 110 g of cobalt chloride hexahydrate and 13.5 g of cerium chloride heptahydrate dissolved, and co-deposited at 25 °C for 30 min, dried at 80 °C for 60 min, reduced in a tube furnace at 400 °C for 60 min with the flow of hydrogen being 10 L / min, and then put into plating solution B, and chemical plated at 80 °C for 10 min to obtain modified raw material powder; (8) 1620 mL of anhydrous ethanol, 180 g of paraffin, and 9 g of oleic acid were added to a horizontal ball mill and idled for 120 min; 10000 g of modified raw material powder and 150 g of electrolytic cobalt powder were added and wet-milled for 720 min to obtain a slurry, which was then transferred to a spray granulator for granulation, and finally dewaxed in hydrogen at 350 °C for 120 min, increased to 1400 °C and applied with 5 MPa for 45 min; decreased to <900 °C, discharged after pressure relief and cooling, to obtain a super coarse cemented carbide material, wherein the inlet temperature of spray granulation was 200 °C and the outlet temperature was 90 °C.

[0030] Example 2: A super coarse cemented carbide material with excellent bending resistance and impact toughness, the specific preparation steps are as follows: (1) 160 g of triaminopropylmethoxysilane, 640 mL of anhydrous acetonitrile, 160 mL of anhydrous propanol, and 3.2 g of tetrabutylammonium hydroxide were added to a glass reaction kettle, 150 mL of deionized water was added dropwise, and stirred at 80 °C for 220 min. After the reaction was completed, the solvent was removed under reduced pressure, recrystallized with ethanol, and vacuum dried at 60 °C to obtain octaaminopropylsilsesquioxane; (2) 50 g of octaaminopropylsilsesquioxane was dissolved in 2000 mL of a mixture of deionized water and 2000 mL of ethanol, and the pH was adjusted to 9 by adding ammonia water. 60 g of levodopa was added, and after air bubbling, it was stirred at 25 °C for 120 min to obtain a catechol grafted intermediate; the intermediate was dispersed in 2000 mL of glacial acetic acid, 80 g of phosphorous acid and 120 mL of formaldehyde solution (37%) were added, and reacted at 90 °C for 330 min. The acid was removed by rotary evaporation, precipitated with ethanol, and vacuum dried at 60 °C to obtain catechol / phosphonic acid bifunctional product; (3) 7000 g of knife block recycled cemented carbide powder and 3000 g of tungsten carbide powder were mixed and then put into a polypropylene barrel, 10000 mL of anhydrous ethanol and 10 g of oleic acid were added, paddle stirring was carried out for 50 min, and then filtration was carried out, vacuum dried at 60 °C for 120 min, and then the obtained product was transferred to a tube furnace, reduced at 430 °C for 80 min with a hydrogen flow of 10 L / min and a heating rate of 5 °C / min, and cooled to <80 °C to obtain a pre-reduced mixed powder; (4) In polypropylene tank 100L deionized water, put in 10000g pre-reduction mixed powder, with 300 rpm mechanical stirring, add 121g cobalt chloride hexahydrate and 15g cerium chloride heptahydrate stirring dispersion uniform, dropwise add ammonia water to adjust pH to 9, 30°C reaction 35min, static, water washing, 80°C drying 60min, finally in the tube furnace, with 10L / min hydrogen, 430°C reduction 80min, get seed layer powder; (5) In polypropylene tank 100L deionized water, 2000g nickel sulfate hexahydrate, 3200g sodium hypophosphite monohydrate after adding 2000g lactic acid (85%), dropwise add ammonia water to adjust pH to 9, add 0.2g thiourea, keep 82°C constant temperature get plating solution A, into which 10000g seed layer powder, 82°C stirring chemical plating 30min, and in the 5min add 10g catechol / phosphonic acid bifunctional product, then the reaction liquid obtained after filtration into co-precipitation tank, add 100L deionized water, 121g cobalt chloride hexahydrate and 15g cerium chloride heptahydrate stirring dispersion uniform form co-deposition liquid, dropwise add ammonia water to adjust pH to 9, 30°C reaction 35min, static, water washing, 80°C drying 60min, finally in the tube furnace, with 10L / min hydrogen, 430°C reduction 80min; (6) In polypropylene tank 100L deionized water, 2000g nickel sulfate hexahydrate and 900g sodium hypophosphite monohydrate after adding 2000g lactic acid (85%), dropwise add ammonia water to adjust pH to 9, add 0.20 thiourea, keep 82°C constant temperature get plating solution B, into which 10000g product obtained in step (5), 82°C stirring chemical plating 18min, get seed layer powder with sandwich structure on the surface; (7) 10000g seed layer powder with sandwich structure on the surface again in the pH 9, 121g cobalt chloride hexahydrate and 15g cerium chloride heptahydrate dissolved in 100L deionized water for co-deposition, 30°C reaction 30min, 80°C drying 60min, in the tube furnace, with 10L / min hydrogen, 430°C reduction 80min after it is put into the plating solution B, 82°C stirring chemical plating 10min, get modified raw material powder; (8) add 1800 mL of anhydrous ethanol, 200 g of paraffin, and 10 g of oleic acid into a horizontal ball mill, and idle for 120 min; add 10000 g of modified raw material powder and 150 g of electrolytic cobalt powder, and wet mill for 720 min to obtain a slurry, then transfer the slurry to a spray granulator for granulation, finally, dewax at 450°C in hydrogen for 120 min, increase to 1450°C and apply 5 MPa for 45 min; decrease to <900°C, release pressure and cool to discharge, to obtain a super coarse cemented carbide material, wherein the inlet temperature of spray granulation is 200°C and the outlet temperature is 90°C.

[0031] Example 3: A super coarse cemented carbide material with excellent bending resistance and impact toughness, the specific preparation steps are as follows: (1) take 180 g of triaminopropylmethoxysilane, 680 mL of anhydrous acetonitrile, 180 mL of anhydrous propanol, and 3.6 g of tetrabutylammonium hydroxide into a glass reaction kettle, add 150 mL of deionized water dropwise, stir and reflux at 80°C for 240 min, after the reaction is completed, remove the solvent under reduced pressure, recrystallize with ethanol, and vacuum dry at 60°C to obtain octaaminopropylsilsesquioxane; (2) take 55 g of octaaminopropylsilsesquioxane and dissolve it in 2200 mL of a mixed solvent of deionized water and 2200 mL of ethanol, add ammonia water to adjust the pH to 9, add 66 g of levodopa, bubble with air, and stir at 25°C for 120 min to obtain a catechol grafted intermediate; disperse the intermediate in 2200 mL of glacial acetic acid, add 88 g of phosphorous acid and 132 mL of formaldehyde solution (37%), react at 95°C for 360 min, remove the acid by rotary evaporation, precipitate with ethanol, and vacuum dry at 60°C to obtain a catechol / phosphonic acid bifunctional product; (3) mix 7000 g of knife block recycled cemented carbide powder and 3000 g of tungsten carbide powder uniformly, then put them into a polypropylene barrel, add 10000 mL of anhydrous ethanol and 11 g of oleic acid, stir with a paddle for 60 min, then perform suction filtration, and vacuum dry at 60°C for 120 min, then transfer the obtained product to a tube furnace, reduce at 450°C under a hydrogen flow of 10 L / min at a heating rate of 5°C / min for 90 min, and cool to <80°C to obtain a pre-reduced mixed powder; (4) add 100 L of deionized water to a polypropylene tank, add 10000 g of pre-reduced mixed powder, mechanically stir at 300 rpm, add 134 g of cobalt chloride hexahydrate and 16.5 g of cerium chloride heptahydrate, stir and disperse uniformly, then add ammonia water dropwise to adjust the pH to 9, react at 30°C for 40 min, stand, wash with water by suction filtration, and dry at 80°C for 60 min, finally, reduce in a tube furnace by introducing hydrogen at a flow rate of 10 L / min at 450°C for 90 min to obtain a seed layer powder; (5) 100 L of deionized water was added into a polypropylene tank, 2200 g of nickel sulfate hexahydrate, 3400 g of sodium hypophosphite monohydrate were dissolved in the water in sequence, then 2200 g of lactic acid (85%) was added, ammonia water was added dropwise to adjust the pH to 9, 0.2 g of thiourea was added, and the temperature was kept at 84°C to obtain plating solution A, 10000 g of seed layer powder was added into the plating solution A, and chemical plating was carried out at 84°C for 30 min, 11 g of catechol / phosphonic acid bifunctional product was added at the 5th minute, then the obtained reaction solution was filtered and transferred into a co-precipitation tank, 100 L of deionized water, 134 g of cobalt chloride hexahydrate and 16.5 g of cerium chloride heptahydrate were added and stirred to form a co-precipitation solution, ammonia water was added dropwise to adjust the pH to 9, and the reaction was carried out at 30°C for 40 min, then the solution was left to stand, filtered, washed with water, dried at 80°C for 60 min, and finally reduced in a tube furnace by passing hydrogen at a flow rate of 10 L / min at 450°C for 90 min; (6) 100 L of deionized water was added into a polypropylene tank, 2200 g of nickel sulfate hexahydrate and 1000 g of sodium hypophosphite monohydrate were dissolved in the water in sequence, then 2200 g of lactic acid (85%) was added, ammonia water was added dropwise to adjust the pH to 9, 0.22 g of thiourea was added, and the temperature was kept at 84°C to obtain plating solution B, 10000 g of the product obtained in step (5) was added into the plating solution B, and chemical plating was carried out at 84°C for 20 min to obtain seed layer powder with sandwich structure on the surface; (7) 10000 g of seed layer powder with sandwich structure on the surface was again co-deposited in 100 L of deionized water with pH of 9, in which 134 g of cobalt chloride hexahydrate and 16.5 g of cerium chloride heptahydrate were dissolved, and the reaction was carried out at 30°C for 30 min, then the solution was dried at 80°C for 60 min, reduced in a tube furnace by passing hydrogen at a flow rate of 10 L / min at 450°C for 90 min, and then added into the plating solution B, and chemical plating was carried out at 84°C for 10 min to obtain modified raw material powder; (8) 1980 mL of anhydrous ethanol, 220 g of paraffin and 11 g of oleic acid were added into a horizontal ball mill, and the mill was run for 120 min, then 10000 g of modified raw material powder and 150 g of electrolytic cobalt powder were added and wet-milled for 720 min to obtain a slurry, which was then transferred into a spray granulator for granulation, and finally dewaxed in hydrogen at 550°C for 120 min, raised to 1500°C and applied with a pressure of 5 MPa for 45 min, then cooled and discharged after the pressure was released when the temperature was lowered to <900°C to obtain super-hard carbide alloy material, wherein the inlet temperature of the spray granulator was 200°C and the outlet temperature was 90°C.

[0032] Comparative Example 1: The difference from Example 2 is that co-deposition was not carried out in step (4), and the other steps were the same as those in Example 2.

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

[0034] Comparative Example 3: The difference from Example 2 is that in step (5), only electroless plating is performed in plating solution A, and in step (7), the seed layer powder having a sandwich structure is replaced by powder electrolessly plated in plating solution A, and the other steps are the same as in Example 2.

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

[0036] Performance test Grain size: determined according to GB / T6394-2017 "Metal Average Grain Size Determination Method"; Hardness: determined according to GB / T3849-2015 "Hard Alloy Rockwell Hardness Test Method", using HRA scale, load 60kg, five points were measured for each sample at different positions, and the average value was taken; Bending strength: GB / T3851-2015 "Hard Alloy Transverse Fracture Strength (Bending Strength) Test Method" was used to measure the fracture strength of the hard alloy under uniaxial bending load in a three-point bending mode; Impact toughness: determined according to GB / T1817-2017 "Hard Alloy Impact Toughness at Room Temperature", the sample size was 10mmx10mmx55mm, the standard Charpy impact test machine pendulum impact energy was 50J, and the impact speed was 5.2m / s for testing; Magnetic saturation determination: according to GB / T 23369-2009 Standard Test Method for Determination of Magnetic Saturation (MS) of Hard Alloy, the sample (mass m) was placed in a magnetic saturation determination device, and the applied magnetic field was gradually increased with high magnetic field strength (2400-3200A / m), when the measured magnetization did not change with the increase of the magnetic field, the maximum magnetization value M was recorded; Magnetic saturation strength Ms (emu / g) = M / m; Coercive force determination: according to GB / T3848-2017, the sample was fully magnetized to saturation in an external magnetic field, and a reverse magnetic field was gradually applied, so that the magnetization gradually decreased, when the magnetic flux density decreased to zero, the reverse magnetic field strength at this time was recorded as the coercive force Hc (unit: kA / m), each sample was tested three times and the average value was 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 super coarse grain cemented carbide material prepared by the present application has high and coordinated levels of hardness, bending strength and impact toughness while the grain size is kept in a stable super coarse range, indicating that the material has a dense structure, a firm interface bonding, a uniform cobalt phase distribution and a stable magnetic saturation value, the chemical state of the binder phase is kept intact, the material still has high hardness, high bending strength and excellent impact toughness under the condition of super coarse grain structure, effectively solving the problem of interface weakening caused by surface oxidation and uneven cobalt distribution of the recycled powder.

[0039] As can be inferred from the performance data of Example 2 and Comparative Example 1 in Table 1, the process of cobalt / cerium co-deposition and hydrogen reduction forms a uniform distribution of metal nuclei and part of cerium-rich phase on the surface of the powder, these “self-catalytic” reduction centers inhibit the continuous existence of the surface oxide film of the recycled powder, enabling the uniform release of the tungsten carbide surface energy, promoting the subsequent sintering densification process, and realizing the directional adhesion and interlayer diffusion of the binder phase during sintering, forming a dense and continuous metal network structure, thereby alleviating the local bonding weakening caused by the surface oxidation difference of the recycled powder. In addition, the stable magnetic saturation value and the increased coercive force also reflect that the cobalt distribution of the binder phase changes from coarse island to fine dispersed state, a stable metallic transition layer is formed in the interface area, improving the magnetic uniformity and structural integrity.

[0040] As can be inferred from the performance data changes of Example 2 and Comparative Examples 2 and 3 in Table 1, the “sandwiched double return” structure plays a significant role in microstructure regulation. This structure realizes multi-scale interface regulation and stress matching by alternately introducing high phosphorus layer, cobalt (containing cerium) intermediate layer and low phosphorus layer during plating layer formation: the higher amorphous Ni-P phase content in the high phosphorus layer may improve the wettability of metallic nickel on the surface of WC particles, helping to improve the liquid phase penetration speed and interface density at the early stage of sintering; the cobalt (containing cerium) layer in the middle forms fine cobalt-cerium complex precipitates during hydrogen reduction, which changes the cobalt phase to uniform and dispersed distribution, thereby inhibiting the excessive aggregation and flow of liquid cobalt; while the low phosphorus layer is converted into a high toughness Ni-Co solid solution region after sintering, forming a “flexible boundary” that can release residual stress and slow down the tendency of interface brittle fracture, the higher coercive force and stable magnetic saturation also indicate that the cobalt distribution of the binder phase is refined and the chemical composition is not damaged.

[0041] From the performance data of Example 2 and Comparative Example 4 in Table 1, it can be inferred that the "wet-on-wet" simultaneous introduction of catechol / phosphonic acid bifunctional molecules makes the mechanical and magnetic properties of the material show a more coordinated improvement trend. In the electroless plating reaction process, the phosphonic acid group produces a directional adsorption effect on the WC surface through strong coordination with nickel and cobalt ions, inducing metal deposition on high-energy sites to form a continuous and adherent phase film layer. At the same time, the catechol group realizes uninterrupted molecular layer connection in the co-deposition environment in a "wet-on-wet" reaction mode, avoiding interface rupture caused by conventional drying or secondary activation. This kind of molecular level structure reconstruction makes the crack repeatedly deflect and release at the interface, and the stress is dispersed and absorbed, so that the strength and toughness are simultaneously improved in the macroscopic aspect.

[0042] It should be understood by those of ordinary skill in the art that the above discussion of any of the embodiments is merely exemplary and is not intended to suggest that the scope of the application is limited to these examples; under the idea of the application, the technical features in the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other changes of different aspects of the application as described above. In order to be brief, they are not provided in details.

Claims

1. A method for producing an ultra coarse cemented carbide material having excellent bending resistance and impact toughness, characterized in that, The method comprises the following steps: S1: preparing a pre-reduction mixed powder: mixing a tool bit recycled cemented carbide powder with tungsten carbide powder, wet treating with ethanol and oleic acid, drying, and pre-reducing under a hydrogen atmosphere to obtain a pre-reduction mixed powder; S2: preparing a seed layer powder: dispersing the pre-reduction mixed powder in a deionized water solution containing cobalt chloride hexahydrate and cerium chloride heptahydrate for co-deposition, and reducing to obtain a seed layer powder; S3: first chemical plating treatment: performing chemical plating on the seed layer powder in plating solution A containing nickel sulfate hexahydrate, sodium hypophosphite monohydrate, lactic acid, and thiourea for 25-30 min, and adding catechol / phosphonic acid bifunctional product at the 5th minute of the reaction; S4: cobalt-cerium co-deposition and second chemical plating: co-depositing the powder after the first chemical plating in a co-deposition solution containing cobalt chloride hexahydrate and cerium chloride heptahydrate, and then transferring to plating solution B containing nickel sulfate hexahydrate, sodium hypophosphite monohydrate, lactic acid, and thiourea for chemical plating for 15-20 min to obtain a seed layer powder with a sandwich structure on the surface; S5: preparing and sintering a modified raw material powder: after co-deposition in the co-deposition solution and chemical plating in plating solution B, the powder with the sandwich structure is wet ground with electrolytic cobalt powder and an organic additive, spray granulated, dewaxed, and sintered at 1400-1500°C and 5 MPa to obtain an ultra-coarse cemented carbide material. The catechol / phosphonic acid bifunctional product in step S3 is octakisaminopropylsilsesquioxane obtained by hydrolysis and condensation of tris(aminopropyl)methoxysilane, reaction with levodopa to obtain a catechol grafted intermediate, and then reaction with phosphorous acid and formaldehyde.

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

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

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

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

6. The method of claim 1, wherein, The amounts of cobalt chloride hexahydrate, cerium chloride heptahydrate, and deionized water in the co-deposition solution in step S4 are 110-134 g, 13.5-16.5 g, and 100 L, respectively.

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

8. The method of claim 1, wherein, The amounts of octakisaminopropylsilsesquioxane, levodopa, phosphorous acid, and formaldehyde solution are 45-55 g, 54-66 g, 72-88 g, and 108-132 mL, respectively.

9. An ultra coarse cemented carbide material having excellent bending resistance and impact toughness, characterized in that, Prepared according to the preparation method of any one of claims 1-8.

10. Use of the ultra-micro hard carbide alloy material according to claim 9, characterized in that, Used for manufacturing of cutting tools, molds, mining equipment, and military aerospace structural components.

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