A hard alloy numerical control blade with excellent cutting performance and a preparation method thereof

Abstract

The present application relates to the technical field of alloy, in particular to a hard alloy numerical control blade with excellent cutting performance and a preparation method thereof.The numerical control blade is made of tungsten carbide-cobalt hard alloy material, and the raw materials include tungsten carbide powder, cobalt powder, two-stage vanadium carbide powder with different particle sizes, graphite and high molecular additives in specific proportions.The core lies in that: the first-stage nanoscale vanadium carbide powder is added into tungsten carbide slurry without cobalt in batches under the action of branched polyethyleneimine in advance, so as to be preferentially positioned on the surface of tungsten carbide particles and realize the inhibition of grain growth; then the linear polyethyleneimine and polyacrylic acid solution are used to fix the microstructure; and finally the second-stage submicron vanadium carbide powder is added together with cobalt powder in the later stage to regulate the sintering interface.The blade prepared by the method can synergistically improve the stability of the relief wear, the ability to resist crater wear and the anti-micro-chipping performance when machining iron-nickel-based high-temperature alloy.

Description

Technical Field

[0001] This invention relates to the field of alloy technology, and in particular to a cemented carbide CNC insert with excellent cutting performance and its preparation method. Background Technology

[0002] In the field of ultrafine and ultrafine-grained cemented carbide CNC cutting tools, suppressing the abnormal growth of tungsten carbide grains during sintering is a key technology for achieving high hardness and high wear resistance. Existing technologies generally employ the pre-addition of grain growth inhibitors, such as vanadium carbide, to the tungsten carbide slurry, and then use methods such as high-energy ball milling to strive for a highly uniform dispersion distribution within the tungsten carbide matrix.

[0003] However, when these cutting tools are used to machine high-temperature alloys such as iron-nickel based and nickel-based alloys, the cutting conditions are often more demanding. The tools must not only withstand severe frictional wear under high temperature and pressure, but also cope with dynamic impacts from intermittent cutting and vibration. Existing cemented carbide cutting tools, characterized by uniformly dispersed inhibitors, often exhibit performance imbalances when facing these complex conditions. On the one hand, although the uniformly distributed inhibitors effectively suppress grain growth and ensure high hardness, their resistance to crater wear is insufficient during prolonged cutting of high-temperature alloys, resulting in a rapid wear development rate and decreased stability of the flank wear. On the other hand, the uniform fine-grained structure designed for high strength and toughness sometimes fails to effectively alleviate stress concentration in the cutting edge region when facing intermittent impacts, leading to an increased tendency for micro-chipping and affecting the tool's reliability under dynamic loads.

[0004] Further research suggests that the root of the problem may lie in a simplistic strategy of uniformly dispersing inhibitors. This strategy fails to finely regulate the time- (temperature) and spatially dependent differentiated functions of inhibitors during sintering. For example, vanadium carbide, uniformly dispersed between tungsten carbide particles, has different mechanisms of action and desired effects in the early stages of sintering (early grain growth) and later stages (binder phase formation and stabilization), but current technology does not differentiate between these. Furthermore, existing technologies typically mix multiple materials (such as tungsten carbide, inhibitors, and cobalt binder phase) in a single batch during ball milling. While this strong mechanical force achieves physical uniformity, it may also damage or prevent the construction of precursor microstructures conducive to interfacial bonding and defect control, ultimately making it difficult to achieve an optimal balance between the two key properties of cemented carbide: "inhibiting grain growth" and "maintaining interfacial toughness / stability." Summary of the Invention

[0005] In view of this, the purpose of this invention is to propose a cemented carbide CNC insert with excellent cutting performance and its preparation method, so as to solve the problems of insufficient resistance to crater wear, poor flank wear stability, and poor resistance to micro-chipping performance that are difficult to balance with high hardness in the cutting of high-temperature alloys by existing cemented carbide CNC inserts.

[0006] To achieve the above objectives, the present invention provides a cemented carbide CNC insert with excellent cutting performance, comprising an insert matrix made of tungsten carbide-cobalt cemented carbide material; wherein the tungsten carbide-cobalt cemented carbide material is prepared from the following raw materials in parts by mass: 884.8-916.2 parts tungsten carbide powder, 80-105 parts cobalt powder, 2-6 parts first-stage vanadium carbide powder, 1-4 parts second-stage vanadium carbide powder, 0.8-1.2 parts graphite, 0.8-1.4 parts branched polyethyleneimine, 0.8-1.3 parts linear polyethyleneimine, and 0.8-1.2 parts polyacrylic acid solution.

[0007] Furthermore, the first vanadium carbide powder is added in portions to a cobalt-free tungsten carbide slurry in the presence of branched polyethyleneimine; after the first vanadium carbide powder is added, linear polyethyleneimine and polyacrylic acid solution are added sequentially; the second vanadium carbide powder is introduced when the cobalt powder is added.

[0008] Preferably, the average particle size of the first vanadium carbide powder is 50 nm, and the average particle size of the second vanadium carbide powder is 700 nm.

[0009] Preferably, the tungsten carbide powder has an average particle size of 0.15 μm, the cobalt powder has an average particle size of 2 μm, and the graphite has an average particle size of 15 μm.

[0010] Preferably, the first vanadium carbide powder is added in two batches, each batch consisting of 1.0-3.0 parts, with an interval of 10-20 minutes between the two additions; the second vanadium carbide powder is wet-mixed together with the cobalt powder and the graphite.

[0011] Preferably, the tungsten carbide-cobalt cemented carbide material is obtained by pressing and sintering, wherein the sintering includes: evacuating to 3-8 Pa, holding at 880-930℃ for 15-30 min, holding at 1165-1200℃ for 15-30 min, and holding at 1398-1420℃ for 45-60 min.

[0012] Preferably, the branched polyethyleneimine has a number-average molecular weight of 600; the linear polyethyleneimine has a number-average molecular weight of 10,000.

[0013] Preferably, the polyacrylic acid solution is a 35wt% aqueous solution with a weight-average molecular weight of 250,000.

[0014] Furthermore, the present invention also provides a method for preparing a cemented carbide CNC insert with excellent cutting performance, comprising the following steps:

[0015] (1) Add anhydrous ethanol, deionized water and branched polyethyleneimine to a ball mill jar, stir, add tungsten carbide powder for wet milling, then add the first stage of vanadium carbide powder in batches and continue wet milling to obtain the first slurry.

[0016] (2) After dissolving linear polyethyleneimine in deionized water, add it to the first slurry. Then dilute the polyacrylic acid solution and add it dropwise to the first slurry. After rolling and mixing, dry, grind and sieve to obtain the first composite powder.

[0017] (3) The first composite powder is wet-mixed with cobalt powder, vanadium carbide powder, graphite and anhydrous ethanol and then dried to obtain the second composite powder;

[0018] (4) Spray the paraffin solution into the second composite powder, mix, dry, granulate and press into CNC blade blanks;

[0019] (5) The CNC cutting blank is dewaxed, vacuum sintered and cooled to obtain a cemented carbide CNC cutting blank matrix, and then ground to obtain a cemented carbide CNC cutting blank with excellent cutting performance.

[0020] Preferably, in step (2), the rolling mixing is performed at 70-90 rpm for 25-40 minutes.

[0021] Preferably, in step (5), dewaxing is performed by heating to 190-220°C at 1°C / min under a hydrogen atmosphere and holding for 25-40 min, then heating to 460-500°C at 1°C / min and holding for 50-75 min.

[0022] The beneficial effects of this invention are:

[0023] Firstly, by pre-adding branched polyethyleneimine to the tungsten carbide slurry and introducing nano-sized vanadium carbide powder in stages under its action, the vanadium carbide can preferentially and stably adsorb onto the surface of tungsten carbide particles, laying the foundation for the subsequent formation of a favorable microstructure. This effectively strengthens the early suppression of abnormal growth of tungsten carbide grains and improves the uniformity of the structure, thereby improving the stability of back face wear while obtaining high hardness.

[0024] Secondly, the precursor slurry is treated under low mechanical disturbance conditions by utilizing the synergistic effect of linear polyethyleneimine and polyacrylic acid solution. This process effectively "locks in" the preliminarily established adjacent spatial relationship between tungsten carbide and the first vanadium carbide segment, preventing subsequent processes from damaging its microstructure. This helps to obtain a more stable tungsten carbide / cobalt interface state after sintering and reduces the rate of crater wear development caused by interface failure during machining.

[0025] Third, the second submicron-sized vanadium carbide segment is added later, along with cobalt powder. This second segment of vanadium carbide primarily serves to supplement vanadium supply and regulate the binder phase during the later stages of sintering, complementing the function of the first segment of vanadium carbide positioned earlier. This strategy significantly reduces the tendency for the cutting edge to chip under intermittent impact, enabling the cutting tool to maintain excellent wear resistance and chipping resistance even under conditions of strong wear and dynamic impact. Detailed Implementation

[0026] 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.

[0027] Raw materials and sources: Tungsten carbide powder, average particle size 0.15μm; vanadium carbide powder (first stage), average particle size 50nm; vanadium carbide powder (second stage), average particle size 700nm; 90g cobalt powder, average particle size 2μm; branched polyethyleneimine, Sigma-Aldrich, model 408719, number average molecular weight 600; linear polyethyleneimine, Sigma-Aldrich, model 765090, number average molecular weight 10000; polyacrylic acid solution, Sigma-Aldrich, model 416002, weight average molecular weight 250000, 35wt% aqueous solution; 1g graphite, Sigma-Aldrich, model 282863, average particle size 15μm; paraffin wax, Sigma-Aldrich, model 76233, low viscosity.

[0028] Example 1:

[0029] Step 1: Add 600g of anhydrous ethanol, 20g of deionized water and 1g of branched polyethyleneimine to a ball mill jar, stir for 10 minutes, then add 903g of tungsten carbide powder, and wet mill at 120 rpm for 120 minutes using cemented carbide balls at a material-to-ball ratio of 3:1; then add 4g of the first stage vanadium carbide powder in two batches of 2g each time, with a 15-minute interval between the two additions, and continue wet milling for 45 minutes after each addition. After all the powder has been added, wet mill for another 90 minutes, and finally let it stand for 30 minutes to obtain the first slurry.

[0030] Step 2: Add 1g of linear polyethyleneimine to 10g of deionized water, stir and dissolve at 50°C, then slowly add it along the wall of the container to the first slurry obtained in Step 1, maintaining stirring at 300rpm for 20min; then dilute 1g of polyacrylic acid solution with 5g of deionized water, and add it dropwise to the above slurry within 15min. After the dropwise addition is completed, simply roll and mix at 80rpm for 30min, without high-energy ball milling; then dry to constant weight under vacuum at 50°C, grind and pass through an 80-mesh sieve to obtain the first composite powder;

[0031] Step 3: Add the first composite powder obtained in Step 2, 90g of cobalt powder, 2g of second-stage vanadium carbide powder, 1g of graphite and 250g of anhydrous ethanol into a ball mill jar, and wet mix at 90 rpm for 240 min at a material-to-ball ratio of 2:1; after mixing, vacuum dry at 50℃ to constant weight to obtain the second composite powder.

[0032] Step 4: Add 15g of paraffin wax to 80g of anhydrous ethanol preheated to 60℃ to dissolve it completely. Then spray the paraffin wax solution into the second composite powder obtained in Step 3, mixing and kneading for 30min while spraying. Subsequently, vacuum dry at 45℃ for 4h, granulate through a 40-mesh sieve, and press the granulated material into CNC blade green body using a molding press at a pressure of 200MPa. After demolding, let it stand for 2h to obtain the green body.

[0033] Step 5: Place the green blank obtained in Step 4 in a vacuum sintering furnace, heat it to 200℃ at 1℃ / min under a hydrogen atmosphere and hold it for 30 min, then heat it to 480℃ at 1℃ / min and hold it for 60 min, then evacuate to 5 Pa, heat it to 900℃ at 3℃ / min and hold it for 20 min, then heat it to 1180℃ at 4℃ / min and hold it for 20 min, and finally heat it to 1410℃ at 3℃ / min and hold it for 50 min to complete sintering. After that, argon gas is introduced to cool it to below 800℃ and cool it with the furnace to obtain the cemented carbide CNC cutting tool substrate, which is then prepared into cemented carbide CNC cutting tools by grinding.

[0034] Example 2:

[0035] Step 1: Add 560g of anhydrous ethanol, 18g of deionized water and 0.8g of branched polyethyleneimine to a ball mill jar, stir for 8 minutes, then add 916.2g of tungsten carbide powder, and wet mill at 115 rpm for 100 minutes using cemented carbide balls at a material-to-ball ratio of 3:1; then add 2g of the first stage vanadium carbide powder in two batches of 1g each time, with a 20-minute interval between the two additions, and continue wet milling for 35 minutes after each addition. After all the powder has been added, wet mill for another 70 minutes, and finally let it stand for 25 minutes to obtain the first slurry.

[0036] Step 2: Add 0.8g of linear polyethyleneimine to 8g of deionized water, stir and dissolve at 45°C, then slowly add it along the wall of the container to the first slurry obtained in Step 1, maintaining stirring at 280rpm for 18min; then dilute 0.8g of polyacrylic acid solution with 4g of deionized water, and add it dropwise to the above slurry over 12min. After the dropwise addition is complete, simply roll and mix at 70rpm for 25min without high-energy ball milling; then dry to constant weight under vacuum at 50°C, grind and pass through an 80-mesh sieve to obtain the first composite powder;

[0037] Step 3: Add the first composite powder obtained in Step 2, 80g of cobalt powder, 1g of second-stage vanadium carbide powder, 0.8g of graphite and 230g of anhydrous ethanol into a ball mill jar, and wet mix at 85rpm for 210min at a material-to-ball ratio of 2:1; after mixing, vacuum dry at 50℃ to constant weight to obtain the second composite powder.

[0038] Step 4: Add 13g of paraffin wax to 75g of anhydrous ethanol preheated to 58℃ to dissolve it completely. Then spray the paraffin wax solution into the second composite powder obtained in Step 3, mixing and kneading for 25min while spraying. Subsequently, vacuum dry at 45℃ for 3.5h, granulate through a 40-mesh sieve, and press the granulated material into CNC blade green body using a molding press at a pressure of 180MPa. After demolding, let it stand for 2h to obtain the green body.

[0039] Step 5: Place the green blank obtained in Step 4 in a vacuum sintering furnace, heat it to 190℃ at 1℃ / min under a hydrogen atmosphere and hold it for 25 min, then heat it to 460℃ at 1℃ / min and hold it for 50 min, then evacuate to 8 Pa, heat it to 880℃ at 3℃ / min and hold it for 15 min, then heat it to 1165℃ at 4℃ / min and hold it for 15 min, and finally heat it to 1398℃ at 3℃ / min and hold it for 45 min to complete sintering. After that, argon gas is introduced to cool it to below 780℃ and it is cooled with the furnace to obtain the cemented carbide CNC cutting tool substrate, which is then prepared into cemented carbide CNC cutting tools by grinding.

[0040] Example 3:

[0041] Step 1: Add 630g of anhydrous ethanol, 22g of deionized water and 1.2g of branched polyethyleneimine to a ball mill jar, stir for 12 minutes, then add 884.8g of tungsten carbide powder, and wet mill at 125 rpm for 130 minutes using cemented carbide balls at a material-to-ball ratio of 3:1; then add 6g of the first stage vanadium carbide powder in two batches of 3g each time, with a 15-minute interval between the two additions, and continue wet milling for 50 minutes after each addition. After all the powder has been added, wet mill for another 100 minutes, and finally let it stand for 30 minutes to obtain the first slurry.

[0042] Step 2: Add 1.2g of linear polyethyleneimine to 12g of deionized water, stir and dissolve at 52℃, then slowly add it along the wall of the container to the first slurry obtained in Step 1, maintaining stirring at 320rpm for 22min; then dilute 1.2g of polyacrylic acid solution with 6g of deionized water, and add it dropwise to the above slurry over 18min. After the dropwise addition is complete, simply roll mix at 85rpm for 35min, without high-energy ball milling; then dry to constant weight under vacuum at 52℃, grind and pass through an 80-mesh sieve to obtain the first composite powder;

[0043] Step 3: Add the first composite powder obtained in Step 2, 105g of cobalt powder, 3g of second-stage vanadium carbide powder, 1.2g of graphite and 270g of anhydrous ethanol into a ball mill jar, and wet mix at 95rpm for 270min at a material-to-ball ratio of 2:1; after mixing, vacuum dry at 52℃ to constant weight to obtain the second composite powder.

[0044] Step 4: Add 17g of paraffin wax to 85g of anhydrous ethanol preheated to 60℃ to dissolve it completely. Then spray the paraffin wax solution into the second composite powder obtained in Step 3, mixing and kneading for 35min while spraying. Subsequently, vacuum dry at 45℃ for 4.5h, granulate through a 40-mesh sieve, and press the granulated material into CNC blade green body using a molding press at a pressure of 220MPa. After demolding, let it stand for 2h to obtain the green body.

[0045] Step 5: Place the green blank obtained in Step 4 in a vacuum sintering furnace, heat it to 200℃ at 1℃ / min under a hydrogen atmosphere and hold it for 30 min, then heat it to 490℃ at 1℃ / min and hold it for 65 min, then evacuate to 5 Pa, heat it to 910℃ at 3℃ / min and hold it for 25 min, then heat it to 1185℃ at 4℃ / min and hold it for 25 min, and finally heat it to 1415℃ at 3℃ / min and hold it for 55 min to complete sintering. After that, argon gas is introduced to cool it to below 800℃ and it is cooled with the furnace to obtain the cemented carbide CNC cutting tool substrate, which is then prepared into cemented carbide CNC cutting tools by grinding.

[0046] Example 4:

[0047] Step 1: Add 580g of anhydrous ethanol, 25g of deionized water and 1.0g of branched polyethyleneimine to a ball mill jar, stir for 10 minutes, then add 895g of tungsten carbide powder, and wet mill at 120rpm for 110 minutes using cemented carbide balls at a material-to-ball ratio of 3:1; then add 3g of the first stage vanadium carbide powder in two batches of 1.5g each time, with a 20-minute interval between the two additions, and continue wet milling for 40 minutes after each addition. After all the powder has been added, wet mill for another 80 minutes, and finally let it stand for 30 minutes to obtain the first slurry.

[0048] Step 2: Add 0.9g of linear polyethyleneimine to 9g of deionized water, stir and dissolve at 50°C, then slowly add it along the wall of the container to the first slurry obtained in Step 1, maintaining stirring at 300rpm for 20min; then dilute 1.0g of polyacrylic acid solution with 5g of deionized water, and add it dropwise to the above slurry over 15min. After the dropwise addition is complete, simply roll and mix at 80rpm for 30min without high-energy ball milling; then dry to constant weight under vacuum at 50°C, grind and pass through an 80-mesh sieve to obtain the first composite powder;

[0049] Step 3: Add the first composite powder obtained in Step 2, 98g of cobalt powder, 3g of second-stage vanadium carbide powder, 1.0g of graphite and 260g of anhydrous ethanol into a ball mill jar, and wet mix at 90rpm for 240min at a material-to-ball ratio of 2:1; after mixing, vacuum dry at 50℃ to constant weight to obtain the second composite powder.

[0050] Step 4: Add 16g of paraffin wax to 82g of anhydrous ethanol preheated to 60℃ to dissolve it completely. Then spray the paraffin wax solution into the second composite powder obtained in step 3, mixing and kneading for 30min while spraying. Subsequently, vacuum dry at 45℃ for 4h, granulate through a 40-mesh sieve, and press the granulated material into CNC blade green body using a molding press at a pressure of 210MPa. After demolding, let it stand for 2h to obtain the green body.

[0051] Step 5: Place the green blank obtained in Step 4 in a vacuum sintering furnace, heat it to 200℃ at 1℃ / min under a hydrogen atmosphere and hold it for 30 min, then heat it to 480℃ at 1℃ / min and hold it for 60 min, then evacuate to 5 Pa, heat it to 900℃ at 3℃ / min and hold it for 20 min, then heat it to 1180℃ at 4℃ / min and hold it for 20 min, and finally heat it to 1408℃ at 3℃ / min and hold it for 50 min to complete sintering. After that, argon gas is introduced to cool it to below 800℃ and cool it with the furnace to obtain the cemented carbide CNC cutting tool substrate, which is then prepared into cemented carbide CNC cutting tools by grinding.

[0052] Example 5:

[0053] Step 1: Add 650g of anhydrous ethanol, 24g of deionized water and 1.4g of branched polyethyleneimine to a ball mill jar, stir for 12 minutes, then add 891.9g of tungsten carbide powder, and wet mill at 130rpm for 150 minutes using cemented carbide balls at a material-to-ball ratio of 3:1; then add 5g of vanadium carbide powder (first stage) in two batches of 2.5g each time, with a 10-minute interval between the two additions, and continue wet milling for 60 minutes after each addition. After all the powder has been added, wet mill for another 120 minutes, and finally let it stand for 35 minutes to obtain the first slurry.

[0054] Step 2: Add 1.3g of linear polyethyleneimine to 12g of deionized water, stir and dissolve at 55℃, then slowly add it along the wall of the container to the first slurry obtained in Step 1, maintaining stirring at 350rpm for 25min; then dilute 1.1g of polyacrylic acid solution with 6g of deionized water, and add it dropwise to the above slurry over 20min. After the dropwise addition is complete, simply roll and mix at 90rpm for 40min, without further high-energy ball milling; then dry to constant weight under vacuum at 52℃, grind and pass through an 80-mesh sieve to obtain the first composite powder;

[0055] Step 3: Add the first composite powder obtained in Step 2, 98g of cobalt powder, 4g of second-stage vanadium carbide powder, 1.1g of graphite and 280g of anhydrous ethanol into a ball mill jar, and wet mix at 100rpm for 300min at a material-to-ball ratio of 2:1; after mixing, vacuum dry at 52℃ to constant weight to obtain the second composite powder.

[0056] Step 4: Add 18g of paraffin wax to 90g of anhydrous ethanol preheated to 62℃ to dissolve it completely. Then spray the paraffin wax solution into the second composite powder obtained in Step 3, mixing and kneading for 35min while spraying. Subsequently, vacuum dry at 46℃ for 5h, granulate through a 40-mesh sieve, and press the granulated material into CNC blade green bodies using a molding press at a pressure of 240MPa. After demolding, let stand for 2h to obtain the green body.

[0057] Step 5: Place the green blank obtained in Step 4 in a vacuum sintering furnace, heat it to 220°C at 1°C / min under a hydrogen atmosphere and hold for 40 min, then heat it to 500°C at 1°C / min and hold for 75 min, then evacuate to 3 Pa, heat it to 930°C at 4°C / min and hold for 30 min, then heat it to 1200°C at 5°C / min and hold for 30 min, and finally heat it to 1420°C at 4°C / min and hold for 60 min to complete sintering. After that, argon gas is introduced to cool it to below 850°C and then it is cooled with the furnace to obtain the cemented carbide CNC cutting tool substrate, which is then prepared into cemented carbide CNC cutting tools by grinding.

[0058] Comparative Example 1:

[0059] The difference from Example 1 is that 1g of branched polyethyleneimine is not added in step 1, and 1g of deionized water is used to make up the amount of liquid added in step 1. The other conditions are the same as in Example 1.

[0060] Comparative Example 2:

[0061] The difference from Example 1 is that: in step 1, 4g of the first stage vanadium carbide powder is not added, and 4g of tungsten carbide powder is used to make up the total amount of powder in step 1; in step 3, 2g of the second stage vanadium carbide powder is still added, and the other conditions are the same as in Example 1.

[0062] Comparative Example 3:

[0063] The difference from Example 1 is that: in step 1, 4g of the first vanadium carbide powder is not added, and 4g of tungsten carbide powder is used to make up the total amount of powder in step 1; in step 3, the amount of the second vanadium carbide powder added is adjusted from 2g to 6g, so that the two vanadium carbide powders are added at once in step 3, and the other conditions are the same as in Example 1.

[0064] Comparative Example 4:

[0065] The difference from Example 1 is that 1g of linear polyethyleneimine is not added in step 2, and 1g of deionized water is used to make up the amount of liquid added in step 2. The other conditions are the same as in Example 1.

[0066] Comparative Example 5:

[0067] The difference from Example 1 is that 1g of polyacrylic acid solution is not added in step 2, and 1g of deionized water is used to make up the amount of liquid added in step 2. The other conditions are the same as in Example 1.

[0068] Comparative Example 6:

[0069] The difference from Example 1 is that after the 1g polyacrylic acid solution is added in step 2, high-energy ball milling is continued for 90 minutes at the material-to-ball ratio of 3:1 and 120rpm as described in step 1, and the other conditions are the same as in Example 1.

[0070] Comparative Example 7:

[0071] The difference from Example 1 is that 2g of vanadium carbide powder in the second stage is not added in step 3, and 2g of tungsten carbide powder is used to make up the total amount of powder in step 3. The other conditions are the same as in Example 1.

[0072] Performance test sample preparation:

[0073] The sintered bodies obtained in Examples 1-5 and Comparative Examples 1-7 were processed into three types of samples: the first type was a 10mm×10mm×6mm block sample, used for density, hardness, and magnetic property testing; the second type was a type B strip sample, 20mm×6.5mm×5.25mm in size, used for transverse fracture strength testing; and the third type was an uncoated CNMG120408 CNC insert, used for cutting performance testing. All inserts were machined using the same grinding program, with a tip radius of 0.8mm, an insert thickness of 4.76mm, and an edge rounding radius controlled at 20±2μm. The cutting tests were uniformly performed using a PCLNR2525M12 tool holder, with a rake angle of -6°, a clearance angle of 6°, and a principal cutting edge angle of 95° after clamping. All test samples were ground stepwise with 320#, 600#, 1200# and 2000# sandpaper before testing, then polished with 1μm diamond suspension, and finally ultrasonically cleaned with anhydrous ethanol for 10 min and dried at 60℃ for 30 min before use.

[0074] Performance testing:

[0075] Density: Density was determined according to GB / T 3850-2015 using the Archimedes method.

[0076] Rockwell A hardness: Hardness was measured according to GB / T 3849.1-2015. The Rockwell A scale was used with a diamond cone indenter. The preload was 98.07 N, the total load was 588.4 N, and the main load was held for 5 seconds. Five block samples were taken from each group. Five points were measured on each sample at positions with a spacing greater than 3 mm between samples and a distance greater than 2 mm from the edge. The maximum and minimum values ​​were removed, and the average value was taken as the hardness value of that sample. The average of the five samples was then calculated.

[0077] Transverse fracture strength: Transverse fracture strength was tested according to GB / T 3851-2015. Type B strip specimens with dimensions of 20mm × 6.5mm × 5.25mm were used, and the surface roughness was controlled to Ra ≤ 0.4μm. A three-point bending fixture was used, with the span between the support points set to 14.5mm and the loading speed set to 0.5mm / min. Five specimens were tested in each group, and the fracture load was recorded and converted into transverse fracture strength. The average value of the five specimens was taken as the result.

[0078] Fracture toughness: Fracture toughness was determined according to JB / T 12616-2016. Polished block samples were selected as the test surface, with a thickness greater than 0.2 mm removed from the sample surface. The sample thickness was 6 mm, and the parallelism between the test surface and the support surface was controlled within 0.01 mm. A calibrated Vickers hardness tester was used to apply a load of 294.2 N at room temperature. Three non-interfering indentations were made on each sample. Subsequently, the diagonal of the indentation and the lengths of the four cracks were measured under an optical microscope with a magnification of not less than 500x. The fracture toughness was calculated according to the standard formula.

[0079] Magnetic saturation and coercivity: Magnetic saturation was tested according to GB / T 23369-2009, and coercivity was tested according to GB / T 3848-2017. Three block samples were taken from each group, and magnetic saturation and coercivity were measured respectively at 23±2℃ using a calibrated hard alloy magnetic property tester. Each sample was tested three times and the average value was taken.

[0080] Continuous turning life: Continuous turning life was determined according to GB / T 16461-2016. Using uncoated CNMG120408 inserts, solution-aged GH4169 round bars were continuously turned on the same CNC lathe. The workpiece diameter was 90 mm, and the measured hardness was 36±2 HRC. Dry cutting was used. Cutting parameters were uniformly set as vc=55 m / min, f=0.15 mm / r, and ap=0.5 mm. At least three new cutting edges were tested for each sample. The machine was stopped every 1 minute of cutting. The maximum wear on the flank face VBmax was measured using a 50× tool microscope, and the crater depth KT was measured using a white light interferometer. When VBmax ≥ 0.30 mm, KT ≥ 0.10 mm, or a chipping width ≥ 0.20 mm appeared, the cutting edge was considered to have failed. The average failure time of the three cutting edges was taken as the continuous turning life.

[0081] Interrupted turning chipping resistance life: The interrupted turning chipping resistance life was extended according to the life evaluation approach of GB / T 16461-2016. The workpiece was still a GH4169 round bar, with two equidistant axial grooves (8mm wide, 3mm deep) pre-drilled on the outer diameter to be machined, subjecting the insert to two interrupted impacts per revolution. Dry cutting was used, with cutting parameters uniformly set as vc=45m / min, f=0.12mm / r, and ap=1.0mm. The machine was stopped every 30 seconds, and the maximum chipping width and maximum flank wear (VBmax) were measured using a 50× tool microscope. Failure was defined as a maximum chipping width ≥ 0.20mm, a maximum flank wear (VBmax) ≥ 0.30mm, or catastrophic chipping. The chipping resistance was evaluated by combining the effective cutting time before failure and the total number of impacts through the grooves. The test results are shown in Table 1.

[0082] Table 1 Performance Test Results

[0083] sample <![CDATA[Density / g / cm 3 > hardness Transverse fracture strength / MPa <![CDATA[Fracture toughness / MPa·m 1 / 2 > Magnetic saturation / % Coercivity / kA / m Continuous turning life / min Intermittent turning life / min Number of failure impacts / times Example 1 14.47 93.0 4180 11.4 90.8 35.8 13.6 9.4 2992 Example 2 14.59 92.8 3920 10.7 89.6 34.6 11.2 7.6 2419 Example 3 14.31 93.2 4010 11.0 92.1 37.2 12.1 8.1 2578 Example 4 14.41 92.8 4260 11.7 91.3 34.9 12.9 9.8 3119 Example 5 14.35 93.1 3970 10.8 91.8 36.9 12.3 7.8 2483 Comparative Example 1 14.39 92.0 3460 10.0 88.4 29.8 8.4 6.2 1974 Comparative Example 2 14.50 91.5 3350 10.2 86.9 24.6 6.8 5.8 1846 Comparative Example 3 14.45 91.9 3120 9.5 88.1 28.1 7.1 4.6 1464 Comparative Example 4 14.42 92.4 3620 10.4 89.3 31.5 8.9 6.8 2165 Comparative Example 5 14.41 92.3 3540 10.3 89.0 30.9 8.6 6.6 2101 Comparative Example 6 14.38 92.2 3410 9.9 88.8 29.4 8.1 6 1910 Comparative Example 7 14.46 92.6 3850 10.9 89.8 33.2 10.4 7.9 2515

[0084] Data Analysis: Data from the examples in the table shows that the cemented carbide CNC inserts prepared by this invention achieve a good balance between hardness, transverse fracture strength, fracture toughness, and continuous and interrupted cutting life. This invention first introduces branched polyethyleneimine into a cobalt-free tungsten carbide slurry and positions the first stage of vanadium carbide. Then, linear polyethyleneimine and polyacrylic acid are used to maintain the adjacent structure under low-disturbance conditions. Finally, the second stage of vanadium carbide is added later, and segmented heat treatment sintering is performed. This continuously suppresses tungsten carbide grain growth while maintaining a stable interface between tungsten carbide and cobalt. The resulting microstructure not only helps to slow down the development of crater wear and flank wear but also reduces the tendency for micro-chipping due to stress concentration on the cutting edge under interrupted impact, thus demonstrating a synergistic effect that balances wear resistance and anti-chipping performance.

[0085] As can be seen from the data in Example 1 and Comparative Example 1 in the table, in the absence of branched polyethyleneimine, the first vanadium carbide segment is difficult to preferentially approach the tungsten carbide surface in the cobalt-free system, weakening its initial positioning effect. Consequently, although the subsequent linear polyethyleneimine and polyacrylic acid still participate in the mixing, it is difficult to establish a stable ortho-ortho relationship. As a result, the uniformity of grain growth inhibition decreases, and local microstructures are more prone to unevenness, ultimately manifesting as a simultaneous decrease in hardness, magnetic properties, and cutting life.

[0086] As can be seen from the data in Example 1 and Comparative Example 2, after removing the first vanadium carbide stage and retaining only the second vanadium carbide stage added later, although grain growth inhibition components still exist in the system, their effect is mainly concentrated in the later stages, making it difficult to timely constrain the growth and rearrangement within the original tungsten carbide neighborhood. Therefore, the hardness, coercivity, and continuous turning stability all decrease significantly.

[0087] As can be seen from the data in Example 1 and Comparative Example 3, when all vanadium carbide is introduced at once during the cobalt powder addition stage, the total amount added on the surface does not decrease, but the transverse fracture strength, fracture toughness, and interrupted turning life are further reduced. This is because vanadium carbide added later is more likely to accumulate locally, making it difficult to form effective adjacent inhibition near the tungsten carbide surface, and also causing poor continuity of the local structure after sintering.

[0088] As can be seen from the data in the table of Example 1 and Comparative Examples 4 and 5, retaining only branched polyethyleneimine and the first stage of vanadium carbide while lacking linear polyethyleneimine, or lacking polyacrylic acid, will result in insufficient maintenance of the established adjacent structure during subsequent mixing, drying, and redispersing processes. The former is more likely to cause insufficient maintenance of particle adjacency relationships in the middle and later stages, while the latter is more likely to cause the established spatial relationships to loosen during post-processing. Both will weaken the uniformity of the microstructure and the stability of the tungsten carbide and cobalt interface.

[0089] As can be seen from the data in Example 1 and Comparative Example 6, continuing high-energy ball milling after adding polyacrylic acid did not result in better overall performance; instead, it reduced transverse fracture strength, fracture toughness, and cutting life. The main reason for this is that the present invention aims to maintain the adjacent structure in the precursor powder after adding polyacrylic acid, rather than further enhancing mechanical dispersion. While high-energy ball milling can further break up agglomerates, it also disrupts the already formed local spatial relationships, weakening the synergistic effect of initial positioning and subsequent locking.

[0090] As can be seen from the data in Example 1 and Comparative Example 7, although relying solely on the first vanadium carbide stage can still achieve good hardness and a certain degree of microstructure stability, the continuous and intermittent turning lifespans are still lower than those in the examples. This indicates that the initial positioning mainly addresses early suppression and initial microstructure control, while the second vanadium carbide stage, after the addition of cobalt powder, still has a compensatory effect on sintering evolution and interface state. The time-sequential introduction of the two vanadium carbide stages helps to suppress abnormal growth and reduces crater wear and chipping tendency during cutting, demonstrating a clear division of labor and synergistic effect.

[0091] 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, 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 cemented carbide CNC insert with excellent cutting performance, characterized in that, The blade substrate comprises a tungsten carbide-cobalt cemented carbide material; the tungsten carbide-cobalt cemented carbide material is prepared from the following raw materials in parts by mass: 884.8-916.2 parts tungsten carbide powder, 80-105 parts cobalt powder, 2-6 parts first-stage vanadium carbide powder, 1-4 parts second-stage vanadium carbide powder, 0.8-1.2 parts graphite, 0.8-1.4 parts branched polyethyleneimine, 0.8-1.3 parts linear polyethyleneimine, and 0.8-1.2 parts polyacrylic acid solution; The first vanadium carbide powder was added in portions to a cobalt-free tungsten carbide slurry in the presence of branched polyethyleneimine. After the first vanadium carbide powder is added, linear polyethyleneimine and polyacrylic acid solution are added in sequence; the second vanadium carbide powder is introduced when the cobalt powder is added.

2. The cemented carbide CNC insert with excellent cutting performance according to claim 1, characterized in that, The average particle size of the first vanadium carbide powder is 50 nm, and the average particle size of the second vanadium carbide powder is 700 nm.

3. The cemented carbide CNC insert with excellent cutting performance according to claim 1, characterized in that, The tungsten carbide powder has an average particle size of 0.15 μm, the cobalt powder has an average particle size of 2 μm, and the graphite has an average particle size of 15 μm.

4. The carbide CNC insert with excellent cutting performance according to claim 1, characterized in that, The first vanadium carbide powder is added in two batches, each time 1.0-3.0 parts, with an interval of 10-20 minutes between the two additions; the second vanadium carbide powder is wet-mixed together with the cobalt powder and the graphite.

5. The cemented carbide CNC insert with excellent cutting performance according to claim 1, characterized in that, The tungsten carbide-cobalt cemented carbide material is obtained by pressing and sintering. The sintering includes: evacuating to 3-8 Pa, holding at 880-930℃ for 15-30 min, holding at 1165-1200℃ for 15-30 min, and holding at 1398-1420℃ for 45-60 min.

6. The cemented carbide CNC insert with excellent cutting performance according to claim 1, characterized in that, The branched polyethyleneimine has a number-average molecular weight of 600; the linear polyethyleneimine has a number-average molecular weight of 10,000.

7. The cemented carbide CNC insert with excellent cutting performance according to claim 1, characterized in that, The polyacrylic acid solution is a 35wt% aqueous solution with a weight-average molecular weight of 250,000.

8. A method for preparing a cemented carbide CNC insert with excellent cutting performance according to any one of claims 1-7, characterized in that, Includes the following steps: (1) Add anhydrous ethanol, deionized water and branched polyethyleneimine to a ball mill jar, stir, add tungsten carbide powder for wet milling, then add the first stage of vanadium carbide powder in batches and continue wet milling to obtain the first slurry. (2) After dissolving linear polyethyleneimine in deionized water, add it to the first slurry. Then dilute the polyacrylic acid solution and add it dropwise to the first slurry. After rolling and mixing, dry, grind and sieve to obtain the first composite powder. (3) The first composite powder is wet-mixed with cobalt powder, vanadium carbide powder, graphite and anhydrous ethanol and then dried to obtain the second composite powder; (4) Spray the paraffin solution into the second composite powder, mix, dry, granulate and press into CNC blade blanks; (5) The CNC cutting blank is dewaxed, vacuum sintered and cooled to obtain a cemented carbide CNC cutting blank matrix, and then ground to obtain a cemented carbide CNC cutting blank with excellent cutting performance.

9. The method for preparing a cemented carbide CNC insert with excellent cutting performance according to claim 8, characterized in that, In step (2), the rolling mixing is performed at 70-90 rpm for 25-40 minutes.

10. The method for preparing a cemented carbide CNC insert with excellent cutting performance according to claim 8, characterized in that, In step (5), dewaxing is performed by heating the temperature to 190-220℃ at 1℃ / min under a hydrogen atmosphere and holding it for 25-40min, then heating the temperature to 460-500℃ at 1℃ / min and holding it for 50-75min.