Hard alloy coating blade for continuous turning of steel part as well as preparation method and application of hard alloy coating blade

Abstract

The invention belongs to the technical field of hard alloy material preparation, and relates to a hard alloy coating blade for continuous turning of steel parts and a preparation method and application of the hard alloy coating blade. The hard alloy coating blade for continuous turning of the steel part comprises a hard alloy matrix and a multi-layer composite CVD coating deposited on the hard alloy matrix. The hard alloy matrix is prepared from the following raw materials in percentage by mass: 80.0 to 90.0 percent of WC with the Fisher particle size of 4.0 mu m, 5.0 to 8.0 percent of Co, 2.0 to 4.0 percent of (W, Ti) C, 0 to 6.0 percent of (Ta, Nb) C and 0 to 1.5 percent of Ti (C0.3 N0.7). A finer and more uniform WC grain structure can be obtained by using the (Ta, Nb) C solid solution, a stable solid solution phase is formed, and excellent high-temperature comprehensive performance, oxidation resistance and comprehensive mechanical performance are provided.

Description

Technical Field

[0001] This invention belongs to the field of cemented carbide material preparation technology, and relates to a cemented carbide coated cutting tool for continuous turning of steel parts, its preparation method and application. Background Technology

[0002] Steel is an iron-carbon alloy with a carbon content between 0.04% and 2.30%. It possesses high plasticity and toughness, making it a fundamental material in modern industry, widely used in automotive, aerospace, and machinery manufacturing. With continuous advancements in industrial technology, the processing demands for steel parts are increasingly shifting towards higher precision, efficiency, and quality. Due to the high hardness and strength of steel, traditional carbide tools and machining methods suffer from low efficiency, short tool life, poor surface quality, and high processing costs when continuously machining high-hardness steel parts, making it difficult to meet the needs of modern industry. Therefore, the development of high-precision, high-performance, general-purpose carbide tools is urgently needed, and the research field is quite extensive.

[0003] Currently, the cemented carbide materials with ordinary grain size researched in domestic continuous turning of steel parts are prepared by adding WC powder of a certain particle size, a certain amount of Co powder and grain inhibitors, and undergoing processes such as ball milling, spray drying, pressing, and sintering. However, the resulting cemented carbide products suffer from low hardness, poor wear resistance, and low bending strength. To meet the requirements of high-speed and high-efficiency turning of steel, cutting tools should possess higher toughness, high-temperature strength, and high-temperature hardness. Coating technology can maintain the toughness of the base material, improve the wear resistance of the cutting tool, and enhance its cutting performance. As a chemical and thermal barrier, the coating reduces diffusion and chemical reactions between the cutting tool and the workpiece, thereby reducing tool wear. This results in alloy cutting tools with high hardness, wear resistance, and heat resistance, and lowers the coefficient of friction between the cutting tool and the workpiece, significantly improving the machining efficiency, machining accuracy, and service life of the cutting tool.

[0004] Chemical vapor deposition (CVD) coatings offer numerous advantages, including high-temperature resistance, wear resistance, oxidation resistance, corrosion resistance, and excellent adhesion. By rationally designing coating process parameters and precisely controlling the composition and structure of the coating, diverse performance requirements can be met. A well-balanced combination of the cemented carbide substrate and coating process parameters can significantly improve the overall performance of cemented carbide-coated tools, enhance machining stability, and extend tool life. Chinese patent CN 109128136 B discloses a coated cutting tool for machining steel parts and its preparation method. The thickness of the β-layer on the cemented carbide substrate is 5-10 μm. Co, TaNb8, (W, Ti)CN, and WC are mixed evenly with a forming agent and then poured into a drum ball mill for ball milling. The ball-milled mixture is then pressed and sintered to form a cemented carbide substrate cutting tool. A coating is applied to the cemented carbide substrate cutting tool, and after sandblasting, a coated cutting tool for machining steel parts is obtained.

[0005] Chinese Patent CN 114231816 A discloses a cemented carbide coated insert substrate for turning steel parts and its preparation method. The insert substrate has a surface de-β layer with a thickness of 15-50 μm. The cemented carbide coated insert substrate comprises the following raw materials in percentage: (Ti,W)C: 0-3%, Ti(C0.5N0.5): 0-3%, TaC: 0-3%, NbC: 0-3%, Cr3C2: 0-3%, Co: 5-12%, with WC to make up 100%. The Ti content in the raw materials is 0.5-2.0%, and the average particle size of (Ti,W)C is 2.5 μm.

[0006] The aforementioned existing technologies employ a relatively thin β-layer, only 5-10 μm thick. This reduces the buffering effect between the substrate and the coating, making crack propagation more likely. Consequently, the coating adhesion decreases significantly, leading to premature peeling, reduced chipping resistance and toughness, and exacerbating flank wear and crater wear, thus drastically shortening the tool life. The high binder phase content in the cemented carbide matrix results in high strength and toughness, but reduces the hardness and edge strength of the insert, making the cutting edge prone to plastic deformation and reducing the flank wear resistance. Furthermore, the separate addition of TaC and NbC additives can cause solid solution reactions during sintering, resulting in alloy sintering deformation, making dimensional control difficult. Excessive gas release can also cause surface pits and increase the raw material costs used in production. Summary of the Invention

[0007] In view of the shortcomings of the prior art, the purpose of this invention is to provide a carbide-coated cutting tool for continuous turning of steel parts, its preparation method and application. This invention uses a (Ta, Nb)C solid solution to obtain a finer and more uniform WC grain structure. The (Ta, Nb)C solid solution, by forming a stable solid solution phase, combines the advantages of both, providing excellent high-temperature performance and oxidation resistance, exhibiting superior overall mechanical properties, and significantly improving the service life of the cutting tool.

[0008] To achieve the above objectives, the technical solution adopted is: One objective of this invention is to provide a carbide-coated insert for continuous turning of steel parts, comprising a carbide substrate and a multilayer composite CVD coating deposited thereon; the carbide substrate is composed of the following raw materials in weight percentages: WC with a Fisher particle size of 4.0 μm: 80.0-90.0%, Co: 5.0-8.0%, (W,Ti)C: 2.0-4.0%, (Ta,Nb)C: 0-6.0%, Ti(C 0.3 N 0.7): 0~1.5%; The multilayer composite CVD coating includes, from the inside out: a TiN substrate layer, an MT-TiCN layer, a transition layer composed of an HT-TiCN layer and a Ti(Al)CNO layer, an Al2O3 layer, and an outermost TiN layer.

[0009] Preferably, the flexural strength of the cemented carbide matrix is ​​2263–3314 MPa, and the Vickers hardness is 1496–1562 HV. 30 .

[0010] Preferably, the total thickness of the multilayer composite CVD coating is 18.0 μm.

[0011] The second objective of this invention is to provide a method for preparing the aforementioned cemented carbide coated cutting tool, comprising the following steps: (1) wet grinding: weighing the raw materials according to the mass percentage described in claim 1; adding the mixed powder to a ball mill, adding 2.0 wt% paraffin, with a ball-to-material ratio of 6:1, using alcohol as the wet grinding medium, and grinding for 25-40 hours, and granulating to obtain the mixed powder; (2) pressing and sintering: pressing the mixed powder into shape, and then sintering it to obtain the cutting tool substrate; (3) pretreatment of coating: subjecting the sintered cutting tool substrate to fine grinding, sandblasting, passivation and plasma cleaning; (4) deposition of CVD coating: sequentially depositing the multilayer composite CVD coating described in claim 1 on the pretreated cutting tool substrate.

[0012] Preferably, the sintering process in step (2) specifically involves placing the pressed blank in a pressure sintering furnace and performing the following steps sequentially: Dewaxing sintering: heating from room temperature to 500℃ at a rate of 1-2℃ / min, with a vacuum of 2600Pa and a holding time of 6h; Vacuum sintering: heating from 500℃ to 1200℃ at a rate of 4℃ / min, with a vacuum of 5-10Pa and a holding time of 4h. Partial pressure sintering: heating to 1350~1470℃, heating rate 4℃ / min, vacuum degree 100Pa, holding time 3h; High-temperature and high-pressure sintering: At a temperature of 1470℃, a pressure of 5MPa is applied and held for 40 minutes; then the furnace is cooled to room temperature.

[0013] Preferably, the process parameters for depositing the CVD coating in step (4) are as follows: The TiN substrate was deposited at a temperature of 900℃ for 75 min, a pressure of 200 mbar, and a ratio of TiCl4 to N2 of the reaction gases of 4:23. The MT-TiCN layer was deposited at a deposition temperature of 820℃, a deposition time of 6h, a deposition pressure of 90mbar, and a ratio of TiCl4 to CH3CN of the reaction gases of 5:1. Deposition of the HT-TiCN layer in the transition layer: deposition temperature 980℃, deposition time 40 min, deposition pressure 150 mbar; The Ti(Al)CNO layer in the transition layer was deposited at a deposition temperature of 1010℃, a deposition time of 0.3h, a deposition pressure of 120mbar, and the ratio of the reaction gases N2, CO, CO2, AlCl3, and TiCl4 was 4:1:1:3:3. The Al2O3 layer was deposited at a temperature of 1020℃ for 8 hours, a pressure of 70 mbar, and the ratio of the reaction gases AlCl3, CO2, H2S, and HCl was 10:7:1:4. The outermost TiN layer was deposited at a deposition temperature of 1000℃, a deposition time of 0.5h, a deposition pressure of 700mbar, and a ratio of TiCl4 to N2 of the reaction gases of 4:29.

[0014] The preparation method of the aforementioned cemented carbide coated cutting tool mainly includes batching and wet grinding, drying and granulation, pressing and molding, sintering treatment, and deposition of CVD coating. The specific process steps are as follows: (1) Weigh the corresponding raw materials according to the corresponding formula ratio: WC raw material with a Fisher particle size of 4.0 μm: 80.0~90.0%, Co: 5.0~8.0%, (W,Ti)C: 2.0~4.0%, (Ta,Nb)C: 0~6.0%, Ti(C 0.3 N 0.7 ): 0~1.5%. Add the mixed powder to a ball mill, add 2.0wt% paraffin, the ball-to-powder ratio is 6:1, use alcohol as the wet grinding medium, the liquid-to-solid ratio is 1:2, the ball milling time is 25~40h, and the mixed powder is obtained by granulation.

[0015] (2) The mixed powder was pressed into PS21B compact sample strips with dimensions of 6.50×5.25×20mm and WNMG080412-DX type blades. The pressing temperature was 20℃ and the pressing humidity was 45%. The sample strips and blades were placed in a pressure sintering furnace for sintering, and were subjected to dewaxing sintering, vacuum sintering, partial pressure sintering and high temperature and high pressure sintering in sequence. Dewaxing sintering: room temperature to 500℃, sintering time approximately 6 hours, heating rate 1-2℃ / min, vacuum degree of dewaxing sintering 2600Pa; Vacuum sintering: 500~1200℃, vacuum degree of vacuum sintering 5-10Pa, heating rate 4℃ / min, sintering time 4 hours; Partial pressure sintering: sintering temperature 1350~1470℃, partial pressure sintering vacuum degree 100Pa, heating rate 4℃ / min, sintering time 3 hours; High temperature and high pressure sintering: sintering temperature 1470℃, pressure 5MPa, holding time 40 minutes; After furnace cooling to room temperature, the sample strip and blade substrate are removed.

[0016] (3) The prepared PS21B test strips and WNMG080412-DX type blade substrate were subjected to performance tests. The test strips were used to test the bending strength, and the blade products were used to test the Vickers hardness and Hc value. The bending strength was 2263~3314MPa, and the Vickers hardness was 1496~1562HV. 30 The HC value is 13.44~14.69KA / m.

[0017] (4) The sintered blade substrate is subjected to pre-coating treatments such as fine grinding, sandblasting, and passivation, and then plasma cleaning for 20 minutes.

[0018] (5) Deposition of CVD coating: A. Preparation of TiN layer: N2 was used as nitrogen source, H2 as carrier gas and equilibrium gas, TiCl4 as Ti source, deposition temperature was 900℃, deposition time was 75min, deposition pressure was 200mbar, and reaction gas ratio TiCl4:N2=4:23. B. Preparation of MT-TiCN layer: CH3CN was used as carbon and nitrogen elements, TiCl4 as titanium source, and H2 as carrier gas and equilibrium gas. A TiCN (i.e. MT-TiCN) layer was deposited on the TiN layer using a medium-temperature chemical vapor deposition (MT-CVD) coating process: the deposition temperature was 820℃, the deposition time was 6 hours, the deposition pressure was 90 mbar, and the reaction gas ratio TiCl4:CH3CN=5:1. C. Preparation of the transition layer: TiCl4 was used as the titanium source, H2 as the carrier gas and equilibrium gas, N2 as the nitrogen source, and CH4 as the carbon source to deposit an HT-TiCN layer on top of the TiCN layer. The deposition temperature was 980℃, the deposition time was 40 min, and the deposition pressure was 150 mbar. Then, TiCl4 was used as the titanium source, H2 as the carrier gas, N2 as the nitrogen source, CO and CO2 as the oxygen source, and AlCl3 as the aluminum source to deposit a Ti(Al)CNO layer. The deposition temperature was 1010℃, the deposition time was 0.3 h, and the deposition pressure was 120 mbar. The reaction gas ratio was N2:CO:CO2:AlCl3:TiCl4 = 4:1:1:3:3. D. Preparation of Al2O3 layer: AlCl3 is used as aluminum source, H2 is used as carrier gas and equilibrium gas, and CO2 is used as oxygen source. An Al2O3 layer is deposited on the transition layer at a deposition temperature of 1020℃, a deposition time of 8 hours, a deposition pressure of 70mbar, and a reaction gas ratio of AlCl3:CO2:H2S:HCl=10:7:1:4. E. Preparation of TiN layer: N2 was used as nitrogen source, H2 as carrier gas and equilibrium gas, TiCl4 as Ti source, deposition temperature was 1000℃, deposition time was 0.5 hours, deposition pressure was 700 mbar, and reaction gas ratio TiCl4:N2=4:29.

[0019] The third objective of this invention is to provide an application of the aforementioned carbide-coated insert in turning 42CrMo steel parts.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: To overcome the shortcomings of the aforementioned technology, this invention, through extensive experimentation and practical experience, has developed a method for preparing carbide-coated inserts for continuous turning of steel parts. This invention features a simple process, high production efficiency, and produces products with improved cutting life, enabling mass production. On the one hand, by rationally proportioning the matrix composition and adding TiCN with a high N content, the migration ability of Ti, Ta, and Nb elements at high temperatures is greatly improved. This allows the thickness of the β-layer to be around 20 μm without reducing the bending strength, which not only improves the adhesion between the cutting tool coating and the matrix, preventing crack propagation and plastic deformation, but also gives the cutting tool excellent high-temperature red hardness, improving the tool's cutting life and stability. Simultaneously, it enhances the interatomic bonding force, causing lattice distortion, which greatly improves the material's resistance to plastic deformation, giving the cutting tool extremely excellent wear resistance and thermal stability. Through rationally proportioning the matrix composition, a matrix material with high strength and hardness is prepared. While ensuring the mechanical properties of cemented carbide, this not only significantly reduces production costs but also improves the wear resistance and fracture resistance of the cutting tool.

[0021] On the other hand, by properly combining the substrate and the coating, the overall performance of the cutting tool can be improved. The high hardness and high wear resistance of the substrate structure combined with the high hardness and high toughness of the CVD coating can significantly improve the wear resistance and impact resistance of the carbide coated tool, and improve the tool's machining life and thermal stability.

[0022] This invention, by adding additives such as (W,Ti)C, (Ta,Nb)C, and TiCN, and through a reasonable ratio of components, prepares a beta-removed layer of appropriate thickness. This layer can both hinder the propagation of cracks when the substrate and coating are bonded together, and ensure sufficient hardness support for the substrate, thereby improving the bonding force between the substrate and the coating. This results in a high-hardness, high-wear-resistant cemented carbide substrate, which improves the hardness, high-temperature red hardness, and processing stability of cemented carbide cutting tools.

[0023] This invention enhances the interatomic bonding force by adding TiCN with a high N content, causing lattice distortion and stronger ability to hinder dislocation movement, thus greatly improving the material's resistance to plastic deformation and achieving peak microhardness. The high N content TiCN can form a very dense and stable TiN-based or Ti(O,N) mixed oxide film, effectively preventing the diffusion of elements such as Ti in cemented carbide into the chips, and also preventing the diffusion of Fe elements from the workpiece into the tool, giving the tool extremely excellent thermal stability and resistance to diffusion wear.

[0024] The use of a lower deposition temperature in the MT-TiCN layer of CVD coating helps to suppress excessive grain growth, refine the grains, make the coating microstructure denser, and improve the coating's hardness, impact resistance, and resistance to thermal crack propagation.

[0025] The coating of this invention is a multi-layer composite coating, which can significantly improve the toughness of the coating through crack deflection and other means, thereby improving the coating bonding strength to a certain extent, ensuring the stability of the coating during the cutting process, and thus improving the service life of the cutting tool.

[0026] By employing a rational combination of substrate and CVD coating, a comprehensive improvement in tool machining performance can be achieved. The combination of a high-hardness substrate and a high-hardness, high-toughness CVD coating can significantly improve the hardness and wear resistance of carbide-coated tools, thereby enhancing tool durability and thermal stability.

[0027] This technical solution is simple, easy to operate, low in cost, highly efficient, and has a long tool life, enabling mass production. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the coating structure designed for this invention.

[0029] Figures 2-5The images show the metallographic microstructures of the cemented carbide substrates prepared in Examples 1-3 and Comparative Example 1 of this invention.

[0030] Figures 6-9 The images show SEM images of the cemented carbide substrates prepared in Examples 1-3 and Comparative Example 1 of this invention.

[0031] Figure 10 This is a SEM image of the cemented carbide coated cutting tool prepared in Example 3 of the present invention. Detailed Implementation

[0032] The present invention will be described below with reference to examples. These examples are only used to explain the present invention and are not intended to limit the scope of the present invention.

[0033] Example 1 (1) Weigh the corresponding raw materials according to the corresponding formula ratio: WC raw material with a Fisher particle size of 4.0 μm: 87.5%, Co: 5.5%, (W,Ti)C: 3.0%, (Ta,Nb)C: 3.0%, Ti(C) 0.3 N 0.7 ): 1.0%, the mixed powder is added to a ball mill, 2.0wt% paraffin is added, the ball-to-powder ratio is 6:1, alcohol is used as the wet grinding medium, the liquid-to-solid ratio is 1:2, the ball milling time is 29h, and the mixed powder is obtained by granulation.

[0034] (2) The mixed powder was pressed into PS21B compact sample strips with dimensions of 6.50×5.25×20mm and WNMG080412-DX type blades. The pressing temperature was 20℃ and the pressing humidity was 45%. The sample strips and blades were placed in a pressure sintering furnace for sintering, and were subjected to dewaxing sintering, vacuum sintering, partial pressure sintering and high temperature and high pressure sintering in sequence. Dewaxing sintering: room temperature to 500℃, sintering time approximately 6 hours, heating rate 1-2℃ / min, vacuum degree of dewaxing sintering 2600Pa; Vacuum sintering: 500~1200℃, vacuum degree of vacuum sintering 5-10Pa, heating rate 4℃ / min, sintering time 4 hours; Partial pressure sintering: sintering temperature 1350~1470℃, partial pressure sintering vacuum degree 100Pa, heating rate 4℃ / min, sintering time 3 hours; High temperature and high pressure sintering: sintering temperature 1470℃, pressure 5MPa, holding time 40 minutes; After furnace cooling to room temperature, the sample strip and blade substrate are removed.

[0035] (3) The sintered blade substrate is subjected to pre-coating treatments such as fine grinding, sandblasting, and passivation, and then plasma cleaning for 20 minutes.

[0036] (4) Deposition of CVD coating: A. Preparation of TiN layer: N2 was used as nitrogen source, H2 as carrier gas and equilibrium gas, TiCl4 as Ti source, deposition temperature was 900℃, deposition time was 75min, deposition pressure was 200mbar, and reaction gas ratio TiCl4:N2=4:23. B. Preparation of MT-TiCN layer: CH3CN was used as carbon and nitrogen elements, TiCl4 as titanium source, and H2 as carrier gas and equilibrium gas. A TiCN (i.e. MT-TiCN) layer was deposited on the TiN layer using a medium-temperature chemical vapor deposition (MT-CVD) coating process: the deposition temperature was 820℃, the deposition time was 6 hours, the deposition pressure was 90 mbar, and the reaction gas ratio TiCl4:CH3CN=5:1. C. Preparation of the transition layer: TiCl4 was used as the titanium source, H2 as the carrier gas and equilibrium gas, N2 as the nitrogen source, and CH4 as the carbon source to deposit an HT-TiCN layer on top of the TiCN layer. The deposition temperature was 980℃, the deposition time was 40 min, and the deposition pressure was 150 mbar. Then, TiCl4 was used as the titanium source, H2 as the carrier gas, N2 as the nitrogen source, CO and CO2 as the oxygen source, and AlCl3 as the aluminum source to deposit a Ti(Al)CNO layer. The deposition temperature was 1010℃, the deposition time was 0.3 h, and the deposition pressure was 120 mbar. The reaction gas ratio was N2:CO:CO2:AlCl3:TiCl4 = 4:1:1:3:3. D. Preparation of Al2O3 layer: AlCl3 is used as aluminum source, H2 is used as carrier gas and equilibrium gas, and CO2 is used as oxygen source. An Al2O3 layer is deposited on the transition layer at a deposition temperature of 1020℃, a deposition time of 8 hours, a deposition pressure of 70mbar, and a reaction gas ratio of AlCl3:CO2:H2S:HCl=10:7:1:4. E. Preparation of TiN layer: N2 was used as nitrogen source, H2 as carrier gas and equilibrium gas, TiCl4 as Ti source, deposition temperature was 1000℃, deposition time was 0.5 hours, deposition pressure was 700 mbar, and reaction gas ratio TiCl4:N2=4:29.

[0037] Example 2 The difference from Example 1 is as follows: The raw material used was WC with a Fisher particle size of 4.0 μm: 84.2%, (Ta, Nb)C: 6.0%, Ti(C) 0.3 N 0.7 ): 1.3%.

[0038] Example 3 The difference from Example 1 is as follows: The raw materials used were WC with a Fisher particle size of 4.0 μm: 84.8%, (W,Ti)C: 3.5%, (Ta,Nb)C: 5.2%.

[0039] Comparative Example 1 The difference from Example 1 is as follows: The raw materials used were WC (84.8%) with a Fisher particle size of 4.0 μm, (W,Ti)C (3.5%), (Ta,Nb)C (5.2%), and Ti(C)... 0.5 N 0.5 ): 1.0%.

[0040] Figure 1 The schematic diagram of the blade coating structure designed in this invention shows that the coating consists of a 5-layer multi-layer composite structure, which consists of the following layers from the base layer to the top layer: TiN layer, TiCN layer, Ti(Al)CNO transition layer, Al2O3 layer, and TiN layer. This multi-layer composite structure improves the bonding strength between the substrate and the coating, and between the coating layers, to a certain extent, ensuring the stability of the coating during the cutting process, thereby improving the service life of the blade.

[0041] Figure 2-5 The figures show the metallographic structures of the cemented carbide substrates prepared in Examples 1-3 and Comparative Example 1 of this invention. As can be seen from the figures, the thinner β-layer in Example 1 makes it prone to crack propagation and coating peeling when the coating adheres to the substrate. The thicker β-layer in Example 2, however, results in excessive TiCN addition, significantly reducing the bending strength of the substrate and making it susceptible to chipping and breakage during cutting. The moderately thick β-layer in Example 3 greatly enhances coating adhesion, improves resistance to thermal cracking and plastic deformation, and enhances the overall performance of the cutting tool.

[0042] Figure 6-9 The images show the SEM morphology of the cemented carbide substrates prepared in Examples 1-3 and Comparative Example 1 of this invention. As can be seen from the images, the WC grains of the cemented carbide substrates prepared in the three examples and the comparative example have a reasonable size distribution, high density, no obvious pores, and no abnormally large grains.

[0043] Figure 10 The image shows the SEM morphology of the cross-section of the cemented carbide coating prepared in Example 3 of this invention. As can be seen from the image, the composite coating exhibits a dense structure within itself and at the interface between the coating and the substrate, free from structural defects such as pores and peeling. The reasonable coating thickness and fine coating grains constitute the high-density structure of the coating. The TiCN layer grains show a tightly packed distribution, with crystals growing along specific crystal planes, exhibiting a distinct columnar crystal structure. The grains are fine and uniform with minimal size variation, and the interface shows no obvious roughness or irregularity. The Al2O3 layer grains are relatively uniform in size, orderly arranged, with smooth and fine grain boundaries, and no obvious grain aggregation or dispersion.

[0044] Performance testing: (1) The PS21B sample strips and WNMG080412-DX cemented carbide insert substrates prepared in Examples 1-3 and Comparative Example 1 were subjected to performance tests. The sample strips were used to test the bending strength performance, and the insert products were used to test the Vickers hardness and coercivity Hc value. The test results are shown in Table 1.

[0045] (2) The thickness of the cemented carbide coating of the present invention was measured by a ball pit tester, and the bonding strength of the coating was tested by the scratch test method (JB / T8554-1997). The scratch test parameters were: loading speed 100N / min, scratch length 5mm, and termination load 180N.

[0046] Table 1. Test results of the sample strips and cemented carbide insert matrix of the examples and comparative examples.

[0047] (1) As can be seen from Table 1, the cemented carbide matrix prepared in Example 3 has the best comprehensive performance, with high hardness and bending strength, and good hardness and wear resistance; the matrix prepared in Comparative Example 1 has the lowest hardness; and the matrix in Example 2 has the lowest strength.

[0048] (2) The coating thickness prepared by this invention is approximately 18.0 μm, and the critical load value of the coating is 146 N. This indicates that the multilayer composite coating composed of the medium-temperature TiCN coating and the Al2O3 coating designed in this invention improves the density of the coating through grain refinement and grain-oriented growth technology, thereby improving the hardness and wear resistance of the coating. At the same time, it avoids local stress concentration or crack propagation caused by uneven grain and non-directional growth, improves the adhesion of the coating, and enhances the overall performance of the coating.

[0049] Comparative cutting experiments of carbide-coated cutting tools: Cutting tests were conducted using the cutting tool WNMG080412-DX prepared according to the embodiments of the present invention and the existing cutting tool WNMG080412-43. The material of the machined product was 42CrMo, and the cutting conditions were as follows: Turning, wet cutting; Cutting speed Vc = 350 m / min; Feed rate f = 0.25 mm / r; The cutting depth ap = 2.0 mm; The test results are shown in Table 2: Table 2 Cutting performance test results

[0050] As shown in Table 1, under the same insert type and cutting conditions, the carbide-coated inserts prepared in Examples 2 and 3 of this invention have a longer service life and better performance under turning conditions than commercially available inserts. Compared with Examples 1, 2, and Comparative Example 1, the technical effect and performance of Example 3 are better, and the overall performance is superior. Example 1 uses a low content of (Ta,Nb)C solid solution in the matrix, resulting in poor high-temperature red hardness of the insert and unstable high-temperature cutting performance. The thinner β-layer and narrower buffer zone between the matrix and coating lead to easy crack propagation, affecting the bonding force between the matrix and coating, and thus affecting the stability of the insert's cutting performance. Example 2 has a higher (Ta,Nb)C solid solution content, which greatly increases production costs. Furthermore, to increase the thickness of the β-layer and thus improve the Ti(C) content... 0.3 N 0.7 The content of α-nitrogen (Ni) leads to a decrease in bending strength, making the cutting tool more prone to chipping and breakage when encountering harsh working conditions with oxide scale. In Embodiment 3 of this invention, to increase the thickness of the β-layer, Ti(C) with a higher Ni content is used. 0.3 N 0.7 The introduction of high-nitrogen atoms enhances the interatomic bonding force, causing lattice distortion and significantly improving the migration ability of Ti, Ta, and Nb elements at high temperatures. This allows the material to maintain a β-layer thickness of approximately 20 μm without reducing bending strength. This improves the adhesion between the cutting tool coating and the substrate, preventing crack propagation and plastic deformation, while also giving the cutting tool excellent high-temperature red hardness, thus increasing its cutting life and stability on steel parts. Comparative Example 1 uses Ti(C)... 0.5 N 0.5 The raw materials have low nitrogen activity in the matrix, and the gradient structure is not easy to form at the same sintering temperature. When machining steel parts at high speed, the tool tip may form crescent-shaped pits more quickly due to diffusion wear.

[0051] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A carbide-coated cutting tool for continuous turning of steel parts, characterized in that, The invention comprises a cemented carbide substrate and a multilayer composite CVD coating deposited thereon; the cemented carbide substrate is composed of the following raw materials in weight percentages: WC with a Fisher particle size of 4.0 μm: 80.0–90.0%, Co: 5.0–8.0%, (W,Ti)C: 2.0–4.0%, (Ta,Nb)C: 0–6.0%, Ti(C) 0.3 N 0.7 ): 0~1.5%; The multilayer composite CVD coating includes, from the inside out: a TiN substrate layer, an MT-TiCN layer, a transition layer composed of an HT-TiCN layer and a Ti(Al)CNO layer, an Al2O3 layer, and an outermost TiN layer.

2. The carbide-coated cutting tool according to claim 1, characterized in that, The total thickness of the multilayer composite CVD coating is 18.0 μm.

3. A method for preparing a cemented carbide coated cutting tool as described in any one of claims 1 to 2, characterized in that, Includes the following steps: (1) Wet grinding of raw materials: Weigh the raw materials according to the mass percentage of claim 1; add the mixed powder to the ball mill, add 2.0wt% paraffin, the ball-to-material ratio is 6:1, use alcohol as wet grinding medium, ball mill for 25-40h, and granulate to obtain mixed powder; (2) Press molding and sintering: Press the mixed powder into shape, and then sinter it to obtain the blade substrate; (3) Pre-coating treatment: Fine grind, sandblast, passivate and plasma clean the sintered blade substrate; (4) Deposition of CVD coating: Sequentially deposit the multilayer composite CVD coating of claim 1 on the pre-treated blade substrate.

4. The method according to claim 3, characterized in that, The sintering process described in step (2) specifically involves placing the pressed billet in a pressure sintering furnace and performing the following steps in sequence: Dewaxing sintering: heating from room temperature to 500℃ at a rate of 1-2℃ / min, with a vacuum of 2600Pa and a holding time of 6h; Vacuum sintering: heating from 500℃ to 1200℃ at a rate of 4℃ / min, with a vacuum of 5-10Pa and a holding time of 4h. Partial pressure sintering: heating to 1350~1470℃, heating rate 4℃ / min, vacuum degree 100Pa, holding time 3h; High-temperature and high-pressure sintering: At a temperature of 1470℃, a pressure of 5MPa is applied and held for 40 minutes; then the furnace is cooled to room temperature.

5. The method according to claim 3, characterized in that, The process parameters for depositing the CVD coating in step (4) are as follows: The TiN substrate was deposited at a temperature of 900℃ for 75 min, a deposition pressure of 200 mbar, and a ratio of TiCl4 to N2 of the reaction gases of 4:

23. The MT-TiCN layer was deposited at a deposition temperature of 820℃, a deposition time of 6h, a deposition pressure of 90mbar, and a ratio of TiCl4 to CH3CN of the reaction gases of 5:

1. Deposition of the HT-TiCN layer in the transition layer: deposition temperature 980℃, deposition time 40 min, deposition pressure 150 mbar; The Ti(Al)CNO layer in the transition layer was deposited at a deposition temperature of 1010℃, a deposition time of 0.3h, a deposition pressure of 120mbar, and the ratio of the reaction gases N2, CO, CO2, AlCl3, and TiCl4 was 4:1:1:3:

3. The Al2O3 layer was deposited at a temperature of 1020℃ for 8 hours, a pressure of 70 mbar, and the ratio of the reaction gases AlCl3, CO2, H2S, and HCl was 10:7:1:

4. The outermost TiN layer was deposited at a deposition temperature of 1000℃, a deposition time of 0.5h, a deposition pressure of 700mbar, and a ratio of TiCl4 to N2 of the reaction gases of 4:

29.

6. The application of a carbide-coated insert as described in any one of claims 1 to 2 in turning 42CrMo steel parts.

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