High toughness hard metal numerical control cutting tool and its preparation method

Abstract

This invention relates to the field of non-ferrous metal alloy manufacturing technology, including metal matrix composites, specifically to a high-strength and tough cemented carbide CNC cutting tool and its preparation method. The invention involves surface activation of tungsten carbide powder, introduction of yttrium and zirconium sources to form a discontinuous island shell of yttrium-zirconium-oxygen functional ceramics, segmented introduction of cerium sources, and finally introduction of vanadium sources. The resulting powder is then dried, pretreated at low temperature, mixed with cobalt powder, pressed, degreased, vacuum sintered, densified by low-pressure sintering, and post-treated at the cutting edge to obtain the cemented carbide CNC cutting tool. This invention helps reduce the risk of functional ceramic agglomeration and interfacial continuity barrier, improving the cutting edge stability of the tool in high-speed dry interrupted cutting.

Description

Technical Field

[0001] This invention relates to the field of non-ferrous metal alloy manufacturing technology, such as metal matrix composites, and specifically to a high-strength and tough cemented carbide CNC cutting tool and its preparation method. Background Technology

[0002] Cemented carbide is a typical metal matrix composite or cermet material formed by powder metallurgy pressing and liquid phase sintering, using refractory metal carbides as the hard phase and non-ferrous metals such as cobalt and nickel as the binder phase. It is an important branch of non-ferrous metal alloy manufacturing technology, including metal matrix composites. Among them, tungsten carbide-cobalt cemented carbide is widely used in metal cutting processes such as CNC turning, milling, boring, and drilling due to its combination of high hardness, wear resistance, red hardness, and a certain degree of toughness.

[0003] With the increasing proportion of tempered steel, die steel, powder metallurgy steel parts, and high-strength structural components being machined, cemented carbide CNC cutting tools need to repeatedly withstand mechanical impact loads, frictional heating, and thermal stress cycles during high-speed, dry, and intermittent cutting. For tungsten carbide-cobalt cemented carbide matrices, the stability of the cutting edge depends not only on the tool geometry but also on the grain size of the tungsten carbide hard phase, the continuity of the cobalt metal binder phase, the interface wetting state, and the distribution of trace modified phases in the composite alloy matrix.

[0004] Existing tungsten carbide-cobalt cemented carbides typically improve strength and toughness by increasing cobalt content, refining tungsten carbide powder, adding grain inhibitors such as vanadium carbide or chromium carbide, or directly introducing functional ceramic phases such as zirconium oxide, cerium oxide, and yttrium oxide. However, while increasing cobalt content can improve toughness, it reduces the load-bearing ratio of the tungsten carbide hard phase, affecting hardness and wear resistance. Simply refining the tungsten carbide powder helps improve hardness, but it easily leads to abnormal grain growth during liquid-phase sintering, making it difficult to stably balance hardness, toughness, and wear resistance.

[0005] Grain inhibitors such as vanadium carbide and chromium carbide can limit the growth of tungsten carbide grains. However, if they form a continuous enriched layer at the interface between tungsten carbide and cobalt metal binder phase, they can easily weaken the wetting effect of the cobalt liquid on the tungsten carbide particles and disrupt the continuous channels of the cobalt binder phase, causing cracks to propagate along the interface. Yttrium-stabilized zirconium oxide, cerium oxide, and other functional ceramics or rare earth oxides, if directly mixed into the tungsten carbide-cobalt system in powder form, are also prone to agglomeration during wet milling, drying, and sintering, forming randomly distributed hard and brittle inclusions, which are detrimental to stress transfer and crack deflection within the metal matrix composite.

[0006] Furthermore, the dispersants, complexing agents, and forming agents used in powder metallurgy are usually decomposed or eliminated during pretreatment, debinding, and sintering stages. Their dispersion and complexing effects before pyrolysis cannot be directly equated to the final composition and structure of the cemented carbide matrix. Therefore, the technical problem faced by the existing technology is: how to achieve the interfacial positioning and distribution of the functional ceramic phase and the grain-inhibiting phase without sacrificing the continuity of the cobalt binder phase, thereby reducing the risk of intermittent cutting chipping caused by oxide agglomeration and continuous barrier. Summary of the Invention

[0007] In view of this, the purpose of this invention is to propose a high-strength and high-toughness cemented carbide CNC cutting tool and its preparation method, so as to solve the problem that existing tungsten carbide-cobalt cemented carbide tools are prone to edge chipping in high-speed dry interrupted cutting due to uneven interface strengthening, grain coarsening and insufficient continuity of binder phase.

[0008] To achieve the above objectives, the present invention provides a high-strength and high-toughness cemented carbide CNC cutting tool, comprising a cemented carbide tool substrate and a cutting edge disposed on the cemented carbide tool substrate; the cemented carbide tool substrate is formed by mixing, pressing, degreasing and sintering raw materials comprising the following parts by weight: 935-945 parts of pretreated modified tungsten carbide powder, 58-62 parts of cobalt powder, 1-3 parts of carbon supplementing agent and 14-18 parts of forming agent;

[0009] The pretreated modified tungsten carbide powder is obtained by surface activation, yttrium-zirconium source co-hydrolysis deposition, cerium source segmented deposition, vanadium source deposition, drying, and low-temperature pretreatment of tungsten carbide powder.

[0010] Preferably, the purity of the tungsten carbide powder is not less than 99%, and the median particle size is 600-800 nm.

[0011] Preferably, the cobalt powder has a purity of not less than 99% and an average particle size of 1000-2000 nm.

[0012] Preferably, the carbon supplement is at least one of conductive carbon black, acetylene black, furnace black, flake graphite, colloidal graphite, nano-graphite, carbon nanotubes, and graphene; used to compensate for carbon potential fluctuations that may be caused by oxygen-containing modified components on the surface of tungsten carbide, thermal decomposition of residual organic matter, and cobalt liquid phase wetting process during sintering, thereby suppressing the formation of decarburized phases and stabilizing the carbon balance of the cemented carbide tool matrix.

[0013] Preferably, the forming agent is at least one of paraffin wax, polyethylene glycol, polyvinyl butyral, ethylene-vinyl acetate copolymer wax, microcrystalline wax, stearic acid, zinc stearate, and polymethyl methacrylate; used to improve the compressibility, blank edge integrity, and demolding stability of the cemented carbide mixture, and is gradually discharged during the degreasing process, and is not a major residual component of the cemented carbide tool matrix after sintering.

[0014] Preferably, the low-temperature pretreatment is carried out in an argon-hydrogen atmosphere, with an argon gas fraction of 95% and a hydrogen gas fraction of 5%. The treatment process includes heating to 230-270℃ at a rate of 1-3℃ / min and holding at that temperature for 50-70min, and then heating to 500-540℃ at a rate of 1-3℃ / min and holding at that temperature for 70-110min.

[0015] A method for preparing a high-strength and high-toughness cemented carbide CNC cutting tool includes the following steps:

[0016] (1) Surface activation treatment of tungsten carbide particles: Tungsten carbide powder is dispersed in a mixture of anhydrous ethanol and deionized water, the pH of the system is adjusted to 9-10, and after stirring and reaction, solid-liquid separation, washing and vacuum drying are performed to obtain surface activated tungsten carbide powder.

[0017] (2) Introducing yttrium and zirconium sources: Surface-activated tungsten carbide powder is dispersed in anhydrous ethanol to form a tungsten carbide suspension. Yttrium and zirconium sources, glacial acetic acid, anhydrous ethanol and deionized water are prepared to form a yttrium-zirconium precursor solution. The yttrium-zirconium precursor solution is added dropwise to the tungsten carbide suspension. Then, a hydrolysate composed of deionized water and anhydrous ethanol is added dropwise and aged to obtain a yttrium and zirconium co-doped tungsten carbide suspension slurry.

[0018] (3) Segmented introduction of cerium source: First, prepare the first cerium source solution by mixing cerium source, ammonium polyacrylate aqueous solution and deionized water and adjust the pH to 5-6. Then add it to the yttrium and zirconium co-doped tungsten carbide suspension slurry. Next, prepare the second cerium source solution by mixing cerium source, hexamethylenetetramine and deionized water and add it. Then heat up and keep warm to obtain the yttrium, zirconium and cerium co-doped tungsten carbide suspension slurry.

[0019] (4) Introducing vanadium source: Mix vanadium source, dihydrate oxalic acid and deionized water to form vanadium oxalic acid complex. Adjust the vanadium oxalic acid complex to weak acidity and then add it dropwise to yttrium, zirconium and cerium co-doped tungsten carbide suspension slurry to obtain co-doped tungsten carbide slurry.

[0020] (5) Drying and low temperature pretreatment: After vacuum concentration and vacuum drying, the co-doped tungsten carbide slurry is subjected to low temperature pretreatment in a mixed atmosphere of argon and hydrogen to obtain pretreated modified tungsten carbide powder.

[0021] (6) Mix with cobalt powder, carbon supplement and forming agent: Add pretreated modified tungsten carbide powder, cobalt powder, conductive carbon black, paraffin and anhydrous ethanol into a ball mill jar for wet milling, dry, sieve and granulate to obtain cemented carbide mixture;

[0022] (7) Pressing and forming: The cemented carbide mixture is loaded into the CNC cutting tool mold, and the cutting tool blank is obtained by unidirectional pressing and cold isostatic pressing.

[0023] (8) Degreasing, vacuum sintering and low-pressure sintering densification: The blade blank is placed in a sintering furnace for degreasing treatment, then heated to the sintering temperature under vacuum and held to allow cobalt to form a liquid phase and wet the tungsten carbide particles. Argon gas is then introduced for low-pressure sintering densification. After cooling, the cemented carbide tool substrate is obtained.

[0024] (9) Edge post-treatment: The cemented carbide tool substrate is subjected to surface grinding, peripheral grinding and edge passivation treatment to obtain a high-strength and tough cemented carbide CNC cutting tool.

[0025] Based on 950 parts by weight of surface-activated tungsten carbide powder, the amounts of yttrium source, zirconium source, cerium source, ammonium polyacrylate aqueous solution, hexamethylenetetramine, and vanadium source are 0.8-1.2 parts, 13-17 parts, 0.8-1.2 parts, 0.4-0.7 parts, 0.3-0.5 parts, and 4-6 parts, respectively; the ratio of cerium source in the first and second cerium source solutions is 3-5:5-7.

[0026] Preferably, the zirconium source is a zirconium propoxide solution with a mass fraction of 70%; the yttrium source is yttrium nitrate hexahydrate; the cerium source is cerium nitrate hexahydrate; and the vanadium source is ammonium metavanadate.

[0027] Preferably, the pH adjustment system described in step (1) is adjusted to 9-10 using ammonia water with a mass fraction of 25%-28%.

[0028] Preferably, the aging temperature in step (2) is 40-50℃ and the aging time is 45-90min.

[0029] Preferably, in step (3), after the first cerium source liquid is added to the tungsten carbide suspension slurry, it is stirred at 40-50°C for 40-60 minutes.

[0030] Preferably, in step (3), after the second cerium source solution is added to the tungsten carbide suspension slurry, it is kept at 65-75℃ for 30-50 minutes, while the pH of the system is controlled to be 6-7 at the end of the reaction.

[0031] Preferably, the solid content of the ammonium polyacrylate aqueous solution in step (3) is 37%-40%, and the weight-average molecular weight is 3000-6000 Da.

[0032] Preferably, step (4) involves adjusting the pH to a weakly acidic state by using ammonia solution with a mass fraction of 25% to 28% to adjust the pH to 4-5;

[0033] Preferably, the vanadium oxalic acid complex in step (4) is added to the system by dropping, with a dropping time of 45-75 min. During the dropping process, the system temperature is maintained at 35-45℃. After the dropping is completed, stirring is continued at 35-45℃ for 40-80 min.

[0034] Preferably, the tungsten carbide slurry described in step (5) is vacuum concentrated at 65-75°C until the solid content is not less than 85%;

[0035] Preferably, the vacuum drying temperature in step (5) is 65-75℃ and the drying time is 6-10h.

[0036] Preferably, the wet grinding in step (6) uses tungsten carbide-cobalt cemented carbide balls as the grinding medium, with a ball-to-material mass ratio of 3:1, and is performed by low-energy wet mixing at 80-120 r / min for 6-10 hours.

[0037] Preferably, the drying temperature in step (6) is 55-65℃ and the drying time is 5-7h.

[0038] Preferably, the sieving in step (6) is sieving through an 80-mesh sieve.

[0039] Preferably, the unidirectional pressing pressure in step (7) is 150-180 MPa.

[0040] Preferably, the cold isostatic pressing pressure in step (7) is 220-260 MPa, and the cold isostatic pressing time is 2-5 min.

[0041] Preferably, the sintering in step (8) includes: placing the blade blank in a sintering furnace, heating it to 280°C at 1°C / min under vacuum and holding it for 60 min, then heating it to 420°C at 1°C / min and holding it for 90 min to remove paraffin; then heating it to 1380-1420°C at 5°C / min under vacuum conditions not exceeding 5 Pa and holding it for 45-75 min to form a liquid phase of cobalt and wet the tungsten carbide particles; after holding it for 30-50 min, introducing argon gas to 4-6 MPa and continuing to hold it for 30-50 min for low-pressure sintering densification, and then cooling it to room temperature with the furnace.

[0042] The beneficial effects of this invention are:

[0043] This invention uses tungsten carbide as the main hard phase and cobalt as the non-ferrous metal binder phase. The cemented carbide tool matrix is ​​prepared by powder pretreatment, mixing and pressing, degreasing, vacuum sintering and low-pressure sintering densification. The technical essence of this invention focuses on the manufacturing process of carbide-based metal matrix composites and non-ferrous metal alloys, rather than simply improving the shape of the tool.

[0044] This invention introduces yttrium and zirconium sources onto the surface of tungsten carbide particles and forms a yttrium-zirconium-oxygen interface modification layer through co-hydrolysis deposition. This allows the functional ceramic modified phase to preferentially reside at active sites on the tungsten carbide surface and near the subsequent tungsten carbide / cobalt interface. Compared to directly mixing oxide powder into the tungsten carbide-cobalt powder system, this method can reduce the random agglomeration of the functional ceramic phase in the cemented carbide matrix and reduce the risk of continuous ceramic layers hindering cobalt liquid phase wetting, thereby improving the interfacial stability and sintering density of the tungsten carbide-cobalt metal matrix composite material.

[0045] This invention introduces cerium source in segments, and through ammonium polyacrylate chain segment anchoring and hexamethylenetetramine alkali release deposition, cerium element acts on the outer and edge positions of the yttrium-zirconium-oxygen interface modified layer, respectively. This treatment method can reduce the risk of local enrichment and coarse cerium oxide inclusions caused by one-time deposition of cerium source, and provide a more stable adsorption site for subsequent vanadium-containing precursors, which is beneficial to forming a more uniform composite interface control effect during cemented carbide sintering.

[0046] This invention introduces ammonium metavanadate after oxalic acid dihydrate complexation and cerium source modification, so that the vanadium-containing precursor is preferentially distributed at the edge of the interface modification layer and the exposed position of tungsten carbide, and forms discontinuous vanadium-containing carbide pinning points during sintering. This method can suppress abnormal growth of tungsten carbide grains and avoid the formation of continuous barrier layers of vanadium-containing carbides, thereby taking into account grain control, cobalt bonding phase connection and hard alloy matrix toughness.

[0047] In summary, compared with existing cemented carbide tools that directly incorporate oxide ceramic phases or grain inhibitors, the cemented carbide tool matrix obtained by this invention has better strength, toughness, density, and anti-chipping stability, making it suitable for high-speed dry interrupted milling of tempered steel, die steel, and powder metallurgy steel parts, which are prone to chipping. Detailed Implementation

[0048] 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.

[0049] The raw material sources and parameters used in this embodiment are as follows:

[0050] Tungsten carbide powder: The purity of tungsten carbide powder is not less than 99%, and the median particle size is 600-800 nm;

[0051] Cobalt powder: purity not less than 99%, average particle size 1000-2000 nm;

[0052] Zirconium n-propoxide solution: 70% by mass, n-propanol as solvent;

[0053] Ammonium polyacrylate aqueous solution: weight average molecular weight 3000-6000 Da, solid content 40%.

[0054] Example 1: A method for preparing a high-strength and high-toughness cemented carbide CNC cutting tool, the specific steps of which are as follows:

[0055] Step 1, Surface activation treatment of tungsten carbide particles:

[0056] 950g of tungsten carbide powder was added to a mixture of 1800g of anhydrous ethanol and 450g of deionized water. Ammonia water with a mass fraction of 28% was added while stirring at 300r / min to maintain the pH of the system at 9-10. The mixture was stirred at 40℃ for 2h. After the reaction was completed, solid-liquid separation was performed. The powder was washed once with 500g of anhydrous ethanol and then once with 500g of deionized water. The powder was then vacuum dried at 60℃ for 6h to obtain surface-activated tungsten carbide powder.

[0057] Step 2, introduce yttrium and zirconium sources:

[0058] All the surface-activated tungsten carbide powder obtained in step 1 was dispersed in 900g of anhydrous ethanol and stirred for 30min at 35℃ and 300r / min to obtain a tungsten carbide suspension. Separately, 15g of 70% zirconium propoxide solution, 1g of yttrium nitrate hexahydrate, 2g of glacial acetic acid and 300g of anhydrous ethanol were mixed and stirred at 35℃ for 30min. Before use, 5g of deionized water was added and stirring was continued for 5min to obtain a yttrium-zirconium precursor solution. The yttrium-zirconium precursor solution was added to the tungsten carbide suspension dropwise for 60min. After the dropwise addition was completed, 85g of deionized water and 100g of anhydrous ethanol were mixed to form a hydrolysate, and the hydrolysate was added dropwise to the above suspension for 90min. After the dropwise addition was completed, the suspension was aged at 45℃ for 60min to obtain a yttrium-zirconium co-doped tungsten carbide suspension slurry.

[0059] Step 3, introduce the cerium source in stages:

[0060] 0.4 g of cerium nitrate hexahydrate, 0.5 g of ammonium polyacrylate aqueous solution and 50 g of deionized water were mixed and stirred at 35 °C for 20 min. The pH of the system was adjusted to 5-6 with glacial acetic acid and then added to the tungsten carbide suspension slurry obtained in step 2. The mixture was stirred at 45 °C for 50 min. Subsequently, 0.6 g of cerium nitrate hexahydrate, 0.4 g of hexamethylenetetramine and 50 g of deionized water were mixed and added to the above slurry. The system was heated to 70 °C and held for 40 min. The pH of the system was controlled to be 6-7 at the end of the reaction to obtain a yttrium, zirconium and cerium co-doped tungsten carbide suspension slurry.

[0061] Step 4, introduce the vanadium source:

[0062] 5g of ammonium metavanadate, 8g of oxalic acid dihydrate, and 150g of deionized water were mixed and stirred at 65°C for 40min to form a soluble vanadium-containing oxalic acid complex. The vanadium-containing oxalic acid complex was then cooled to 40°C, and 25% ammonia was added to adjust the pH of the system to 4-5, resulting in a weakly acidic vanadium-containing precursor solution. The vanadium-containing precursor solution was added dropwise to the suspension slurry obtained in step 3 for 60min, while maintaining a temperature of 40°C and stirring at 300r / min during the dropwise addition. After the dropwise addition was completed, stirring was continued at 40°C for another 60min to obtain a co-doped tungsten carbide slurry.

[0063] Step 5, Drying and Low-Temperature Pretreatment:

[0064] The tungsten carbide slurry obtained in step 4 was vacuum concentrated at 70°C until it no longer flowed significantly, and then vacuum dried at 70°C for 8 hours to obtain dried modified tungsten carbide powder. The dried modified tungsten carbide powder was placed in a mixed atmosphere of argon and hydrogen, wherein the argon gas fraction was 95% and the hydrogen gas fraction was 5%. The temperature was increased to 250°C at 2°C / min and held for 60 min, then increased to 520°C at 2°C / min and held for 90 min. After that, it was cooled to room temperature to obtain pretreated modified tungsten carbide powder.

[0065] Step 6: Mix with cobalt powder, carbon supplement, and forming agent:

[0066] 940g of pretreated modified tungsten carbide powder, 60g of cobalt powder, 2g of conductive carbon black, 16g of paraffin wax and 500g of anhydrous ethanol were added to a ball mill jar. Tungsten carbide-cobalt cemented carbide balls were used as the grinding medium, with a ball-to-material mass ratio of 3:1. The mixture was wet-mixed at 100r / min for 8h. After mixing, the mixture was vacuum-dried at 60℃ for 6h, passed through an 80-mesh sieve and granulated to obtain a cemented carbide mixture.

[0067] Step 7, Pressing and shaping:

[0068] All the cemented carbide mixture obtained in step 6 is loaded into a CNC cutting tool mold. It is first pressed into a cutting tool blank at 160MPa, and then cold isostatically pressed at 240MPa for 3 minutes to obtain a cutting tool blank with uniform density.

[0069] Step 8: Degreasing, vacuum sintering, and low-pressure sintering densification:

[0070] The blade blank obtained in step 7 was placed in a sintering furnace and heated to 280°C at a rate of 1°C / min under vacuum and held for 60 min. Then, it was heated to 420°C at a rate of 1°C / min and held for 90 min to remove paraffin. Subsequently, it was heated to 1400°C at a rate of 5°C / min under vacuum conditions not exceeding 5 Pa and held for 60 min to allow cobalt to form a liquid phase and wet the tungsten carbide particles. After the holding period, argon gas was introduced to 5 MPa and the temperature was maintained for another 40 min for low-pressure sintering densification. The blank was then cooled to room temperature with the furnace to obtain the cemented carbide tool substrate.

[0071] Step 9, Post-processing of the cutting edge:

[0072] The carbide tool substrate obtained in step 8 is subjected to conventional surface grinding, peripheral grinding and edge passivation treatment to make the edge radius 20-35μm, thus obtaining a high-strength and tough carbide CNC cutting tool.

[0073] Example 2:

[0074] In step 1, 950g of tungsten carbide powder was added to a mixture of 1800g of anhydrous ethanol and 450g of deionized water. Ammonia water with a mass fraction of 25% was added while stirring at 300r / min to maintain the pH of the system at 9-10. The mixture was stirred at 40℃ for 120min. After the reaction was completed, solid-liquid separation was performed. The powder was washed once with 500g of anhydrous ethanol and then once with 500g of deionized water. Subsequently, it was vacuum dried at 60℃ for 6h to obtain surface-activated tungsten carbide powder.

[0075] In step 2, all the surface-activated tungsten carbide powder obtained in step 1 is dispersed in 950g of anhydrous ethanol and stirred for 30min at 35℃ and 300r / min to obtain a tungsten carbide suspension. Separately, 16g of 70% zirconium propoxide solution, 1.1g of yttrium nitrate hexahydrate, 2g of glacial acetic acid, and 320g of anhydrous ethanol are mixed and stirred at 35℃ for 30min. Before use, 5g of deionized water is added and stirring continues for 5min to obtain a yttrium-zirconium precursor solution. The yttrium-zirconium precursor solution is added dropwise to the tungsten carbide suspension for 65min. After the dropwise addition is complete, 90g of deionized water and 110g of anhydrous ethanol are mixed to form a hydrolysate, which is then added dropwise to the suspension for 100min. After the dropwise addition is complete, the suspension is aged at 45℃ for 75min to obtain a yttrium-zirconium co-doped tungsten carbide suspension slurry.

[0076] In step 3, 0.45g of cerium nitrate hexahydrate, 0.6g of ammonium polyacrylate aqueous solution, and 50g of deionized water were mixed and stirred at 35°C for 25min. The pH of the system was adjusted to 5-6 with glacial acetic acid and then added to the tungsten carbide suspension slurry obtained in step 2. The mixture was stirred at 45°C for 55min. Subsequently, 0.65g of cerium nitrate hexahydrate, 0.45g of hexamethylenetetramine, and 50g of deionized water were mixed and added to the above slurry. The system was heated to 70°C and held for 45min. The pH of the system was controlled to be 6-7 at the end of the reaction to obtain a yttrium, zirconium, and cerium co-doped tungsten carbide suspension slurry.

[0077] In step 4, 5g of ammonium metavanadate, 8g of oxalic acid dihydrate, and 160g of deionized water are mixed and stirred at 65°C for 45 minutes to form a soluble vanadium-containing oxalic acid complex. The vanadium-containing oxalic acid complex is then cooled to 40°C, and 25% ammonia is added to adjust the pH of the system to 4-5, resulting in a weakly acidic vanadium-containing precursor solution. The vanadium-containing precursor solution is added dropwise to the suspension slurry obtained in step 3 for 65 minutes, while maintaining a temperature of 40°C and stirring at 300 r / min during the dropwise addition. After the dropwise addition is completed, stirring is continued at 40°C for 70 minutes to obtain a co-doped tungsten carbide slurry.

[0078] In step 5, the tungsten carbide slurry obtained in step 4 is vacuum concentrated at 70°C until it no longer flows significantly, and then vacuum dried at 70°C for 8 hours to obtain dried modified tungsten carbide powder. The dried modified tungsten carbide powder is placed in a mixed atmosphere of argon and hydrogen, wherein the argon gas fraction is 95% and the hydrogen gas fraction is 5%. The temperature is increased to 250°C at 2°C / min and held for 60 minutes, then increased to 520°C at 2°C / min and held for 90 minutes. Finally, it is cooled to room temperature to obtain pretreated modified tungsten carbide powder.

[0079] In step 6, 940g of pretreated modified tungsten carbide powder, 60g of cobalt powder, 2g of conductive carbon black, 16g of paraffin wax, and 500g of anhydrous ethanol obtained in step 5 were weighed and added to a ball mill jar. Tungsten carbide-cobalt cemented carbide balls were used as the grinding medium, with a ball-to-material mass ratio of 3:1. The mixture was wet-mixed at 100r / min for 8h. After mixing, the mixture was vacuum-dried at 60℃ for 6h, passed through an 80-mesh sieve, and granulated to obtain a cemented carbide mixture.

[0080] In step 7, all the cemented carbide mixture obtained in step 6 is loaded into a CNC cutting tool mold, first pressed into a cutting tool blank at 160MPa, and then cold isostatically pressed at 240MPa for 3 minutes to obtain a cutting tool blank with uniform density.

[0081] In step 8, the blade blank obtained in step 7 is placed in a sintering furnace and heated to 280°C at a rate of 1°C / min under vacuum and held for 60 min. Then, it is heated to 420°C at a rate of 1°C / min and held for 90 min to remove paraffin. Subsequently, under a vacuum of no more than 5 Pa, the temperature is increased to 1410°C at a rate of 5°C / min and held for 65 min to allow cobalt to form a liquid phase and wet the tungsten carbide particles. After the holding period, argon gas is introduced to 5 MPa and the temperature is held for another 45 min for low-pressure sintering densification. Then, the blank is cooled to room temperature in the furnace to obtain the cemented carbide tool substrate.

[0082] In step 9, the carbide tool substrate obtained in step 8 is subjected to conventional surface grinding, peripheral grinding and edge passivation treatment to make the edge radius 20μm to 35μm, thus obtaining a high-strength and tough carbide CNC cutting tool.

[0083] Example 3:

[0084] In step 1, 950g of tungsten carbide powder was added to a mixture of 1600g of anhydrous ethanol and 400g of deionized water. 25% ammonia water was added while stirring at 250r / min to maintain the pH of the system at 9-10. The mixture was stirred at 35℃ for 90min. After the reaction was completed, solid-liquid separation was performed. The powder was washed once with 400g of anhydrous ethanol and then once with 400g of deionized water. The powder was then vacuum dried at 55℃ for 5h to obtain surface-activated tungsten carbide powder.

[0085] In step 2, all the surface-activated tungsten carbide powder obtained in step 1 is dispersed in 800g of anhydrous ethanol and stirred for 20min at 30℃ and 250r / min to obtain a tungsten carbide suspension. Separately, 13g of 70% zirconium propoxide solution, 0.8g of yttrium nitrate hexahydrate, 1g of glacial acetic acid, and 250g of anhydrous ethanol are mixed and stirred at 30℃ for 20min. Before use, 5g of deionized water is added and stirring is continued for 5min to obtain a yttrium-zirconium precursor solution. The yttrium-zirconium precursor solution is added to the tungsten carbide suspension dropwise over a period of 45min. After the dropwise addition is complete, 75g of deionized water and 80g of anhydrous ethanol are mixed to form a hydrolysate, which is then added dropwise to the suspension over a period of 60min. After the dropwise addition is complete, the suspension is aged at 40℃ for 45min to obtain a yttrium-zirconium co-doped tungsten carbide suspension slurry.

[0086] In step 3, 0.3g of cerium nitrate hexahydrate, 0.4g of ammonium polyacrylate aqueous solution and 40g of deionized water were mixed and stirred at 30°C for 15min. The pH of the system was adjusted to 5-6 with glacial acetic acid and then added to the tungsten carbide suspension slurry obtained in step 2. The mixture was stirred at 40°C for 40min. Subsequently, 0.5g of cerium nitrate hexahydrate, 0.3g of hexamethylenetetramine and 40g of deionized water were mixed and added to the above slurry. The system was heated to 65°C and held for 30min. The pH of the system was controlled to be 6-7 at the end of the reaction to obtain a yttrium, zirconium and cerium co-doped tungsten carbide suspension slurry.

[0087] In step 4, 4g of ammonium metavanadate, 6g of oxalic acid dihydrate, and 120g of deionized water are mixed and stirred at 60°C for 30min to form a soluble vanadium-containing oxalic acid complex. The vanadium-containing oxalic acid complex is then cooled to 35°C, and 25% ammonia is added to adjust the pH of the system to 4-5, resulting in a weakly acidic vanadium-containing precursor solution. The vanadium-containing precursor solution is added dropwise to the suspension slurry obtained in step 3 for 45min, while maintaining a temperature of 35°C and stirring at 250r / min during the dropwise addition. After the dropwise addition is completed, stirring is continued at 35°C for 40min to obtain a co-doped tungsten carbide slurry.

[0088] In step 5, the tungsten carbide slurry obtained in step 4 is vacuum concentrated at 65°C until it no longer flows significantly, and then vacuum dried at 65°C for 6 hours to obtain dried modified tungsten carbide powder. The dried modified tungsten carbide powder is placed in a mixed atmosphere of argon and hydrogen, wherein the argon gas fraction is 95% and the hydrogen gas fraction is 5%, and the temperature is increased to 230°C at 1°C / min and held for 50 minutes, then increased to 500°C at 1°C / min and held for 70 minutes, and then cooled to room temperature to obtain pretreated modified tungsten carbide powder.

[0089] In step 6, 935g of pretreated modified tungsten carbide powder, 58g of cobalt powder, 1g of conductive carbon black, 14g of paraffin wax and 400g of anhydrous ethanol obtained in step 5 were weighed and added to a ball mill jar. Tungsten carbide-cobalt cemented carbide balls were used as the grinding medium, with a ball-to-material mass ratio of 3:1. The mixture was wet-mixed at 80 r / min for 6 h. After mixing, the mixture was vacuum-dried at 55℃ for 5 h, passed through an 80-mesh sieve and granulated to obtain a cemented carbide mixture.

[0090] In step 7, all the cemented carbide mixture obtained in step 6 is loaded into a CNC cutting tool mold, first pressed into a cutting tool blank under 150MPa, and then cold isostatically pressed at 220MPa for 2 minutes to obtain a cutting tool blank with uniform density.

[0091] In step 8, the blade blank obtained in step 7 is placed in a sintering furnace and heated to 280°C at a rate of 1°C / min under vacuum and held for 60 min. Then, it is heated to 420°C at a rate of 1°C / min and held for 90 min to remove paraffin. Subsequently, under a vacuum of no more than 5 Pa, the temperature is increased to 1380°C at a rate of 5°C / min and held for 45 min to allow cobalt to form a liquid phase and wet the tungsten carbide particles. After the holding period, argon gas is introduced to 4 MPa and the temperature is held for another 30 min for low-pressure sintering densification. Then, the blank is cooled to room temperature in the furnace to obtain the cemented carbide tool substrate.

[0092] In step 9, the carbide tool substrate obtained in step 8 is subjected to conventional surface grinding, peripheral grinding and edge passivation treatment to make the edge radius 20-35μm, thus obtaining a high-strength and tough carbide CNC cutting tool.

[0093] Example 4:

[0094] In step 1, 950g of tungsten carbide powder was added to a mixture of 2000g of anhydrous ethanol and 500g of deionized water. Ammonia water with a mass fraction of 25% was added while stirring at 350r / min to maintain the pH of the system at 9-10. The mixture was stirred at 45℃ for 150min. After the reaction was completed, solid-liquid separation was performed. The powder was washed once with 600g of anhydrous ethanol and then once with 600g of deionized water. Subsequently, it was vacuum dried at 65℃ for 7h to obtain surface-activated tungsten carbide powder.

[0095] In step 2, all the surface-activated tungsten carbide powder obtained in step 1 is dispersed in 1000g of anhydrous ethanol and stirred at 40℃ and 350r / min for 40min to obtain a tungsten carbide suspension. Separately, 17g of 70% zirconium propoxide solution, 1.2g of yttrium nitrate hexahydrate, 3g of glacial acetic acid, and 350g of anhydrous ethanol are mixed and stirred at 40℃ for 40min. Before use, 5g of deionized water is added and stirring is continued for 5min to obtain a yttrium-zirconium precursor solution. The yttrium-zirconium precursor solution is added to the tungsten carbide suspension dropwise over a period of 75min. After the dropwise addition is complete, 95g of deionized water and 120g of anhydrous ethanol are mixed to form a hydrolysate, which is then added dropwise to the suspension over a period of 120min. After the dropwise addition is complete, the suspension is aged at 50℃ for 90min to obtain a yttrium-zirconium co-doped tungsten carbide suspension slurry.

[0096] In step 3, 0.5g of cerium nitrate hexahydrate, 0.7g of ammonium polyacrylate aqueous solution, and 60g of deionized water were mixed and stirred at 40°C for 30min. The pH of the system was adjusted to 5-6 with glacial acetic acid and then added to the tungsten carbide suspension slurry obtained in step 2. The mixture was stirred at 50°C for 60min. Subsequently, 0.7g of cerium nitrate hexahydrate, 0.5g of hexamethylenetetramine, and 60g of deionized water were mixed and added to the above slurry. The system was heated to 75°C and held for 50min. The pH of the system was controlled to be 6-7 at the end of the reaction to obtain a yttrium, zirconium, and cerium co-doped tungsten carbide suspension slurry.

[0097] In step 4, 6g of ammonium metavanadate, 10g of oxalic acid dihydrate, and 180g of deionized water are mixed and stirred at 70°C for 50min to form a soluble vanadium-containing oxalic acid complex. The vanadium-containing oxalic acid complex is then cooled to 45°C, and 25% ammonia is added to adjust the pH of the system to 4-5, resulting in a weakly acidic vanadium-containing precursor solution. The vanadium-containing precursor solution is added dropwise to the suspension slurry obtained in step 3 for 75min, while maintaining a temperature of 45°C and stirring at 350r / min during the dropwise addition. After the dropwise addition is completed, stirring is continued at 45°C for 80min to obtain a co-doped tungsten carbide slurry.

[0098] In step 5, the tungsten carbide slurry obtained in step 4 is vacuum concentrated at 75°C until it no longer flows significantly, and then vacuum dried at 75°C for 10 hours to obtain dried modified tungsten carbide powder. The dried modified tungsten carbide powder is placed in a mixed atmosphere of argon and hydrogen, wherein the argon gas fraction is 95% and the hydrogen gas fraction is 5%. The temperature is increased to 270°C at 3°C / min and held for 70 minutes, then increased to 540°C at 3°C / min and held for 110 minutes. Finally, it is cooled to room temperature to obtain pretreated modified tungsten carbide powder.

[0099] In step 6, 945g of pretreated modified tungsten carbide powder, 62g of cobalt powder, 3g of conductive carbon black, 18g of paraffin wax, and 600g of anhydrous ethanol obtained in step 5 were weighed and added to a ball mill jar. Tungsten carbide-cobalt cemented carbide balls were used as the grinding medium, with a ball-to-material mass ratio of 3:1. The mixture was wet-mixed at 120r / min for 10h. After mixing, the mixture was vacuum-dried at 65℃ for 7h, passed through an 80-mesh sieve, and granulated to obtain a cemented carbide mixture.

[0100] In step 7, all the cemented carbide mixture obtained in step 6 is loaded into a CNC cutting tool mold, first pressed into a cutting tool blank at 180MPa, and then cold isostatically pressed at 260MPa for 5 minutes to obtain a cutting tool blank with uniform density.

[0101] In step 8, the blade blank obtained in step 7 is placed in a sintering furnace and heated to 280°C at a rate of 1°C / min under vacuum and held for 60 min. Then, it is heated to 420°C at a rate of 1°C / min and held for 90 min to remove paraffin. Subsequently, under a vacuum of no more than 5 Pa, it is heated to 1420°C at a rate of 5°C / min and held for 75 min to allow cobalt to form a liquid phase and wet the tungsten carbide particles. After the holding period, argon gas is introduced to 6 MPa and the temperature is maintained for another 50 min for low-pressure sintering densification. Then, it is cooled to room temperature with the furnace to obtain the cemented carbide tool substrate.

[0102] In step 9, the carbide tool substrate obtained in step 8 is subjected to conventional surface grinding, peripheral grinding and edge passivation treatment to make the edge radius 20-35μm, thus obtaining a high-strength and tough carbide CNC cutting tool.

[0103] The difference between Comparative Example 1 and Example 1 is that, instead of adding the yttrium-zirconium precursor solution to the tungsten carbide suspension in step 2, all the surface-activated tungsten carbide powder obtained in step 1 is directly dispersed in 900g of anhydrous ethanol and stirred for 30min at 35°C and 300r / min before proceeding to step 3; at the same time, 15g of 70% zirconium propoxide solution and 1g of yttrium nitrate hexahydrate are transferred to step 6 and added together with 60g of cobalt powder, 2g of conductive carbon black, 16g of paraffin wax and 500g of anhydrous ethanol into a ball mill jar for low-energy wet mixing; the remaining conditions are the same as in Example 1.

[0104] The difference between Comparative Example 2 and Example 1 is that in step 2, instead of adding the yttrium-zirconium precursor solution first and the hydrolysate later, 15g of 70% zirconium propoxide solution, 1g of yttrium nitrate hexahydrate, 2g of glacial acetic acid, 300g of anhydrous ethanol, 5g of deionized water, 85g of deionized water and 100g of anhydrous ethanol were mixed at one time, stirred at 35°C for 60min and then added to the tungsten carbide suspension obtained in step 1, and aged at 45°C for 60min; the other conditions were the same as in Example 1.

[0105] The difference between Comparative Example 3 and Example 1 is that in step 3, cerium nitrate hexahydrate is not added in stages, but 1g of cerium nitrate hexahydrate, 0.5g of ammonium polyacrylate aqueous solution, 0.4g of hexamethylenetetramine and 100g of deionized water are mixed at one time, stirred at 35°C for 20min, and the pH of the system is adjusted to 5-6 before being added to the tungsten carbide suspension slurry obtained in step 2. The system is then heated to 70°C and kept at that temperature for 40min. The other conditions are the same as in Example 1.

[0106] The difference between Comparative Example 4 and Example 1 is that in step 3, 0.5g of ammonium polyacrylate aqueous solution was replaced with 0.5g of deionized water; the other conditions were the same as in Example 1.

[0107] The difference between Comparative Example 5 and Example 1 is that the weakly acidic vanadium-containing precursor solution obtained in step 4 is added in step 2 earlier. That is, the vanadium-containing precursor solution is added dropwise immediately after the yttrium-zirconium precursor solution is added in step 2, and the dropwise addition time is 60 minutes. Then, a hydrolysate consisting of 85 g of deionized water and 100 g of anhydrous ethanol is added dropwise, and aging is completed according to step 2 of Example 1. Step 3 still involves the segmented introduction of the cerium source according to Example 1. The remaining conditions are the same as in Example 1.

[0108] The difference between Comparative Example 6 and Example 1 is that ammonium metavanadate is not added in step 4. Instead, a blank oxalic acid solution prepared with 8 g of oxalic acid dihydrate and 150 g of deionized water and adjusted to pH 4-5 is used to replace the vanadium-containing oxalic acid complex solution. The dropping method, dropping time, temperature and subsequent stirring conditions are the same as in step 4 of Example 1; the other conditions are the same as in Example 1.

[0109] Performance testing

[0110] Carbide CNC cutting tools prepared in Examples 1 to 4 and Comparative Examples 1 to 6 were used as test samples. At least three independent sintering batches were prepared for each group of samples. Ten cutting tools were taken from each sintering batch, with three tools used for density, hardness, metallographic structure, and microstructure testing; three tools used for transverse fracture strength and fracture toughness testing; and four tools used for face milling life and edge chipping area testing. Samples used for mechanical testing were cut from the tool substrate of the same sintering batch or from a rectangular blank of the same composition sintered in the furnace. After grinding with a diamond wheel, the surface roughness Ra of the test surface was ensured to be no greater than 0.2 μm. Samples used for microstructure testing underwent inlay, rough grinding, fine grinding, and 1 μm diamond polishing. Cutting tools used for face milling life testing maintained the 20 μm to 35 μm edge radius obtained in step 9 of Example 1, without any additional coating treatment.

[0111] Tungsten carbide grain size testing: Based on GB / T 3488.2-2025 "Metallographic determination of cemented carbide microstructure - Part 2: Measurement of WC grain size". Three sintered tool substrates were taken from each sample group, polished, and observed using a metallographic microscope and scanning electron microscope. Ten fields of view were randomly selected from each sample for tungsten carbide grain size analysis.

[0112] Density and relative density testing: Density testing was conducted according to GB / T 3850-2015 "Method for Determination of Density of Dense Sintered Metallic Materials and Hard Alloys". Three sintered tool substrates were taken from each sample group. They were first ultrasonically cleaned with anhydrous ethanol for 10 min, then dried at 80℃ for 60 min. After cooling to room temperature, the density was determined using the Archimedes method. The weighing accuracy was 0.1 mg. Each sample was measured three times, and the average value was taken as the density of that sample. Relative density was calculated based on the measured density and theoretical density. The theoretical density was adjusted according to the mass ratio of tungsten carbide, cobalt, and introduced inorganic phases in each sample group.

[0113] Rockwell hardness testing: Rockwell hardness testing was conducted according to GB / T 3849.1-2015 "Hard Alloy Rockwell Hardness Test (A Scale) Part 1: Test Method". Three sintered tool substrates were taken from each sample group and subjected to HRA hardness testing on the polished rake face. The initial test force was 98.07 N, and the total test force was 588.4 N. A diamond conical indenter was used. Five points were tested on each sample, with a minimum distance of 1.5 mm between the centers of adjacent indentations and a minimum distance of 1.5 mm between the center of the indentation and the edge of the sample. The average HRA value and standard deviation for each sample group were recorded.

[0114] Transverse fracture strength test: The transverse fracture strength test was conducted according to GB / T 3851-2015 "Method for Determination of Transverse Fracture Strength of Cemented Carbide". Five rectangular specimens were prepared for each group of samples by furnace sintering of the same batch of mixture. The specimen dimensions were 20mm × 6.5mm × 5.25mm. The specimen surface was ground with a diamond wheel, and the chamfer of the edges was no greater than 0.1mm. A three-point bending fixture with a span of 14.5mm was used, and the loading rate was 1mm / min. The fracture load was recorded, and the transverse fracture strength was calculated.

[0115] Fracture toughness testing: Fracture toughness testing was conducted according to JB / T 12616-2016 "Test Method for Fracture Toughness of Carbide Tool Matrix Materials". Three sintered tool substrates were taken from each sample group. Indentation crack testing was performed on the polished cross-section using a Vickers indenter. The test force was 294.2 N, and the holding time was 15 s. Five effective indentations were prepared for each sample. After testing, the diagonal length of the indentation and the radial crack length were measured using an optical microscope or scanning electron microscope. Data with asymmetrical cracks or indentations located in obvious pores were discarded, and the average fracture toughness was calculated.

[0116] Face milling life and edge chipping area test: The face milling life test was conducted according to GB / T 16459-2016 "Face Milling Cutter Life Test". CNMG120408 or SNMG120408 inserts prepared in Examples 1 to 4 and Comparative Examples 1 to 6 were mounted on indexable face milling cutter heads with a diameter of 63 mm. Only one insert was mounted at a time, and the remaining cutter heads were left unloaded to avoid interference between different inserts. The workpiece material was 42CrMo tempered steel with a hardness of 30HRC to 35HRC, and the workpiece dimensions were 300 mm × 100 mm × 80 mm. Dry cutting was used with a cutting speed of 180 m / min, a feed per tooth of 0.12 mm / z, an axial depth of cut of 1 mm, and a radial width of cut of 40 mm. The machine was stopped every 5 minutes of cutting. The width of the wear band on the flank was measured using a tool microscope, and the cutting edge image was acquired using a scanning electron microscope. The cutting edge was considered considered successful when the average width of the wear band on the flank reached 0.30 mm, the continuous chipping length reached 0.50 mm, and the area of ​​a single chipped edge reached 0.20 mm. 2 When breakage occurs, the tool is deemed to have reached the end of its lifespan. The chipping area of ​​the cutting edge is statistically analyzed using a binarized image analysis method at the same magnification, and the total chipping area within a 5mm range of the center of the main cutting edge is counted for each insert.

[0117] Table 1 Performance Test Results

[0118] Average grain size of tungsten carbide / μm Relative density / % Rockwell hardness / HRA Transverse fracture strength / MPa <![CDATA[Fracture toughness / MPa·m 1 / 2 > Face milling life / min <![CDATA[Chip breaking area of cutting edge after 20 minutes of cutting / mm 2 > Main failure modes Example 1 0.54 99.4 92.8 2620 15.6 46.8 0.054 Uniform back face wear with slight chipping Example 2 0.62 98.7 92.3 2410 14.7 39.6 0.073 Uniform wear with minor chipping Example 3 0.48 99.1 93.0 2558 15.2 43.5 0.063 Wear on the flank face with slight thermal cracking Example 4 0.50 99.5 93.1 2695 15.9 48.2 0.049 Predominantly uniform wear Comparative Example 1 0.74 97.3 91.6 2105 12.8 27.4 0.139 Oxide agglomeration induces local chipping Comparative Example 2 0.68 97.9 91.9 2230 13.4 30.8 0.121 Continuous sedimentary layers with microcracks Comparative Example 3 0.65 98.5 92.1 2295 13.8 32.6 0.112 Localized chipping after random deposition of cerium source Comparative Example 4 0.70 98.2 91.8 2208 13.1 29.7 0.128 Cerium source agglomeration induces crack propagation Comparative Example 5 0.72 98.0 92.0 2180 13.0 28.2 0.135 Vanadium-containing species mismatch triggers blade breakage Comparative Example 6 0.89 99.0 91.5 2260 14.1 25.6 0.151 Grain growth leads to wear and chipping.

[0119] Data Analysis: As shown in Table 1, the high-strength and high-toughness cemented carbide CNC cutting tools prepared in Examples 1 to 4 all have high relative density, small average tungsten carbide grain size, high transverse fracture strength and fracture toughness, and exhibit good comprehensive effects in terms of face milling life and edge chipping area. The above results indicate that the tools prepared by the present invention can maintain the hardness and density of the cemented carbide matrix while taking into account the crack propagation resistance and edge stability, and are suitable for high-speed dry interrupted milling of 42CrMo quenched and tempered steel, mold steel and powder metallurgy steel parts and other easily chipped machining scenarios.

[0120] As shown in Table 1, in Comparative Example 1, without the pre-formation of a discontinuous island shell in the yttrium-zirconium-oxygen functional ceramic before the addition of cobalt powder, the transverse fracture strength and fracture toughness decreased to 2105 MPa and 12.8 MPa·m, respectively. 1 / 2The milling life was only 27.4 min, indicating that it is difficult to achieve interface positioning enhancement by mixing the functional ceramic phase as a whole. Although Yttrium source and zirconium source were still introduced in Comparative Example 2, the method of adding the precursor liquid first and then the hydrolysate was not adopted. Instead, the relative density and cutting life decreased, indicating that the over-continuous shell layer is not conducive to the continuous wetting of the cobalt binder phase. Comparative Example 3 and Comparative Example 4 respectively canceled the segmented introduction of cerium source or canceled the anchoring of polyacrylate chain segments, indicating that the cerium source needs to form effective sites through segmented deposition.

[0121] In summary, the carbide CNC cutting tools prepared by this invention exhibit more stable cutting edge performance under high-speed, dry, and interrupted cutting conditions. Their advantages are not limited to a single increase in strength or hardness, but rather reflect a comprehensive balance between density, grain size, fracture toughness, face milling life, and chipping control, making them suitable for continuous batch machining of tempered steel, die steel, and powder metallurgy steel parts.

[0122] 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 high toughness cemented carbide numerically controlled cutting tool, characterized in that, It includes a cemented carbide tool substrate and a cutting edge disposed on the cemented carbide tool substrate; the cemented carbide tool substrate is formed by mixing, pressing, degreasing and sintering raw materials comprising the following parts by mass: 935-945 parts of pretreated modified tungsten carbide powder, 58-62 parts of cobalt powder, 1-3 parts of carbon supplementing agent and 14-18 parts of forming agent; The pretreated modified tungsten carbide powder is obtained by surface activation, yttrium-zirconium source co-hydrolysis deposition, cerium source segmented deposition, vanadium source deposition, drying, and low-temperature pretreatment of tungsten carbide powder.

2. The high-strength and high-toughness cemented carbide CNC cutting tool according to claim 1, characterized in that, The purity of the tungsten carbide powder is not less than 99%, and the median particle size is 600-800 nm; the purity of the cobalt powder is not less than 99%, and the average particle size is 1000-2000 nm.

3. The high-strength and high-toughness cemented carbide CNC cutting tool according to claim 1, characterized in that, The carbon supplement is at least one of conductive carbon black, acetylene black, furnace black, flake graphite, colloidal graphite, nano-graphite, carbon nanotubes, and graphene; the forming agent is at least one of paraffin wax, polyethylene glycol, polyvinyl butyral, ethylene-vinyl acetate copolymer wax, microcrystalline wax, stearic acid, zinc stearate, and polymethyl methacrylate.

4. The high-strength and high-toughness cemented carbide CNC cutting tool according to claim 1, characterized in that, The low-temperature pretreatment is carried out in an argon-hydrogen atmosphere, with an argon gas integral of 95% and a hydrogen gas integral of 5%. The treatment process includes heating to 230-270℃ at a rate of 1-3℃ / min and holding at that temperature for 50-70min, and then heating to 500-540℃ at a rate of 1-3℃ / min and holding at that temperature for 70-110min.

5. A method for preparing a high-strength and high-toughness cemented carbide CNC cutting tool according to any one of claims 1-4, characterized in that, Includes the following steps: (1) Surface activation treatment of tungsten carbide particles: Tungsten carbide powder is dispersed in a mixture of anhydrous ethanol and deionized water, the pH of the system is adjusted to 9-10, and after stirring and reaction, solid-liquid separation, washing and vacuum drying are performed to obtain surface activated tungsten carbide powder. (2) Introducing yttrium and zirconium sources: Surface-activated tungsten carbide powder is dispersed in anhydrous ethanol to form a tungsten carbide suspension, yttrium and zirconium sources are added, and then a hydrolysate composed of deionized water and anhydrous ethanol is added dropwise and aged to obtain yttrium and zirconium co-doped tungsten carbide suspension slurry; (3) Segmented introduction of cerium source: First, prepare the first cerium source solution by mixing cerium source, ammonium polyacrylate aqueous solution and deionized water and adjust the pH to 5-6. Then add it to the yttrium and zirconium co-doped tungsten carbide suspension slurry. Next, prepare the second cerium source solution by mixing cerium source, hexamethylenetetramine and deionized water and add it. Then heat up and keep warm to obtain the yttrium, zirconium and cerium co-doped tungsten carbide suspension slurry. (4) Introducing vanadium source: Mix vanadium source, dihydrate oxalic acid and deionized water to form vanadium oxalic acid complex. Adjust the vanadium oxalic acid complex to weak acidity and then add it dropwise to yttrium, zirconium and cerium co-doped tungsten carbide suspension slurry to obtain co-doped tungsten carbide slurry. (5) Drying and low temperature pretreatment: After vacuum concentration and vacuum drying, the co-doped tungsten carbide slurry is subjected to low temperature pretreatment in a mixed atmosphere of argon and hydrogen to obtain pretreated modified tungsten carbide powder. (6) Mix with cobalt powder, carbon supplement and forming agent: Add pretreated modified tungsten carbide powder, cobalt powder, conductive carbon black, paraffin and anhydrous ethanol into a ball mill jar for wet milling, dry, sieve and granulate to obtain cemented carbide mixture; (7) Pressing and forming: The cemented carbide mixture is loaded into the CNC cutting tool mold, and the cutting tool blank is obtained by unidirectional pressing and cold isostatic pressing. (8) Degreasing, vacuum sintering and low-pressure sintering densification: The blade blank is placed in a sintering furnace for degreasing treatment, then heated to the sintering temperature under vacuum and held to allow cobalt to form a liquid phase and wet the tungsten carbide particles. Argon gas is then introduced for low-pressure sintering densification. After cooling, the cemented carbide tool substrate is obtained. (9) Edge post-treatment: The cemented carbide tool substrate is subjected to surface grinding, peripheral grinding and edge passivation treatment to obtain a high-strength and tough cemented carbide CNC cutting tool; Based on 950 parts by weight of surface-activated tungsten carbide powder, the amounts of yttrium source, zirconium source, cerium source, ammonium polyacrylate aqueous solution, hexamethylenetetramine, and vanadium source are 0.8-1.2 parts, 13-17 parts, 0.8-1.2 parts, 0.4-0.7 parts, 0.3-0.5 parts, and 4-6 parts, respectively; the ratio of cerium source in the first and second cerium source solutions is 3-5:5-7.

6. The preparation method according to claim 5, characterized in that, The aging temperature in step (2) is 40-50℃ and the aging time is 45-90min.

7. The preparation method according to claim 5, characterized in that, The solid content of the ammonium polyacrylate aqueous solution in step (3) is 37%-40%, and the weight average molecular weight is 3000-6000 Da.

8. The preparation method according to claim 5, characterized in that, The zirconium source is a zirconium n-propoxide solution with a mass fraction of 70%; the yttrium source is yttrium nitrate hexahydrate; the cerium source is cerium nitrate hexahydrate; and the vanadium source is ammonium metavanadate.

9. The preparation method according to claim 5, characterized in that, The unidirectional pressing pressure in step (7) is 150-180 MPa; the cold isostatic pressing pressure in step (7) is 220-260 MPa, and the cold isostatic pressing time is 2-5 min.

10. The preparation method according to claim 5, characterized in that, The sintering in step (8) includes: placing the blade blank in a sintering furnace, heating it to 280°C at 1°C / min under vacuum and holding it for 60 min, then heating it to 420°C at 1°C / min and holding it for 90 min; then heating it to 1380-1420°C at 5°C / min under vacuum conditions not exceeding 5 Pa and holding it for 45-75 min; after holding it for 30-50 min, argon gas is introduced to 4-6 MPa and the temperature is maintained for low-pressure sintering densification, and then the furnace is cooled to room temperature.