Polycrystalline diamond-hard alloy composite tool and preparation method thereof

Abstract

The invention belongs to the field of superhard material synthesis, and particularly relates to a method for preparing a polycrystalline diamond-hard alloy composite cutter, which comprises the following steps: firstly, providing a hard alloy comprising a base and a boss; the surface of the boss is subjected to acid pickling cobalt removal; forming a coating layer on the surface of the boss; then carrying out annealing treatment to obtain a hard alloy preform; providing a carbon cup comprising a substrate and at least one channel; the hard alloy prefabricated body is placed in the hole channel, and a gap exists between the coating layer and the inner wall of the hole channel; the gap is filled with a mixture containing diamond powder and a binder, and a composite tool raw material block is obtained; and the composite cutter raw material block is sequentially sintered and subjected to finish machining, and the polycrystalline diamond-hard alloy composite cutter is obtained. According to the method, the limitation of complex tool cutting edge machining is broken through, and precise forming is achieved; the interlayer interface bonding strength between the hard alloy and the polycrystalline diamond is enhanced, and the high-temperature stability and the service life of the composite tool are improved.

Description

Technical Field

[0001] This application belongs to the field of superhard material synthesis, specifically involving polycrystalline diamond-hard alloy composite cutting tools and their preparation methods. Background Technology

[0002] In current processes, the polycrystalline diamond layer of composite cutting tools needs to be welded to the surface of a cemented carbide substrate. This results in weak interfacial bonding strength between the cemented carbide and polycrystalline diamond, insufficient impact resistance, and a low heat resistance threshold. This method is no longer suitable for the machining requirements of composite cutting tools under extreme working conditions and also limits their machining efficiency. Furthermore, due to the limitations of existing manufacturing processes, it is impossible to achieve precise shaping of complex cutting edges, further restricting their adaptation to the needs of high-end manufacturing scenarios. Therefore, the manufacturing methods for composite cutting tools require further improvement.

[0003] Application content This application aims to at least partially solve one of the technical problems in the related art. To this end, this application proposes a method for preparing a polycrystalline diamond-cement carbide composite tool and a corresponding polycrystalline diamond-cement carbide composite tool. This method breaks through the limitations of machining complex tool edges, realizes the precision forming of complex tool edges, enhances the interlayer interface bonding strength between cemented carbide and polycrystalline diamond, or improves the high-temperature stability and service life of polycrystalline diamond-cement carbide composite tools.

[0004] A first aspect of this application provides a method for preparing polycrystalline diamond-cement composite cutting tools, comprising: A cemented carbide is provided, the cemented carbide including a connected base and a boss, the orthographic projection of the boss in the axial direction falling inside the orthographic projection of the base in the axial direction, and there is a gap between the outer contour line of the orthographic projection of the base in the axial direction and the outer contour line of the orthographic projection of the boss in the axial direction. The surface of the boss is acid-washed to remove cobalt, resulting in a roughened cemented carbide. A coating layer is formed on the surface of the boss to obtain a coated cemented carbide, wherein the coating layer comprises elemental Ti powder, TiC, B4C, and Y2O3; The coated cemented carbide is annealed to obtain a cemented carbide preform; A carbon cup is provided, the carbon cup comprising a matrix and at least one channel located in the matrix; The cemented carbide preform is placed in the channel, the cemented carbide preform matches the channel, and there is a gap between the coating layer and the inner wall of the channel; The gap is filled with a mixture of diamond powder and binder to obtain a composite tool raw material block; The composite tool raw material block is sintered under a pressure of 4GPa-5GPa to obtain a polycrystalline diamond-hard alloy composite tool precursor.

[0005] The polycrystalline diamond-cement composite tool precursor is precision machined to obtain the polycrystalline diamond-cement composite tool.

[0006] Therefore, the above method breaks through the limitations of machining complex cutting edges of polycrystalline diamond-carbide composite tools, achieving precision forming of complex cutting edges of composite tools. Furthermore, this application sets a coating layer between the cemented carbide and polycrystalline diamond, effectively improving the interfacial bonding strength between the two, thereby significantly improving the high-temperature stability and service life of the polycrystalline diamond-carbide composite tool.

[0007] According to embodiments of this application, at least one of the following conditions is met: the mass ratio of the Ti elemental powder, TiC, B4C, and Y2O3 is 30-68:15-34:15-34:2, and the mass ratio of TiC to B4C is 1:1. Therefore, within the above-mentioned mass ratio range, it helps to improve the hardness and wear resistance of the coating layer, and also improves the bonding strength between the coating layer and the boss surface.

[0008] According to an embodiment of this application, the thickness of the coating layer is 0.2 mm to 0.5 mm. Within this range, good adhesion between the coating layer and the boss surface can be ensured, while providing sufficient hardness and wear resistance.

[0009] According to an embodiment of this application, the method further includes: purifying the composite tool raw material block. The composite tool raw material block is treated at 800℃-1000℃ for 1-2 hours. Under these conditions, it helps to fully remove moisture and volatile impurities, improving the purity of the composite tool raw material block, thereby increasing the strength and service life of the polycrystalline diamond-carbide composite tool.

[0010] According to embodiments of this application, at least one of the following conditions is met: the acid used for pickling includes nitric acid; the concentration of the acid used for pickling is 5 mol / L-6.5 mol / L; and the pickling time is 40 min-50 min. Therefore, under the above conditions, it is helpful to accurately control the cobalt removal depth while ensuring the integrity of the porous structure and avoiding pore wall collapse.

[0011] According to embodiments of this application, at least one of the following conditions is met: the binder includes at least one of Co and Ni; in the mixture, the mass ratio of the diamond powder to the binder is 5-20:80-95. Therefore, the binder exhibits excellent ductility and adhesion, which helps to tightly bond polycrystalline diamond grains, thereby giving the composite tool higher hardness and extending its service life.

[0012] According to embodiments of this application, the annealing satisfies at least one of the following conditions: the annealing temperature is 500°C-600°C; and the annealing time is 5 h-8 h. Therefore, appropriate annealing time and temperature help to fully eliminate thermal stress in the coating layer, thereby improving the bonding strength between the coating layer and the boss.

[0013] According to an embodiment of this application, the sintering further includes: assembling the composite tool raw material block into a composite block, and sintering it at a temperature of 1300℃-1500℃ for 10min-20min in a six-sided top press. Thus, within the above temperature and time range, it helps the components of the coating layer to achieve sufficient metallurgical bonding with the interface of the diamond powder, completely eliminating porosity and achieving strong bonding strength.

[0014] A second aspect of this application provides a polycrystalline diamond-cement composite tool, which is prepared by the method described above. This composite tool possesses all the features and advantages of the method described above for preparing polycrystalline diamond-cement composite tools, which will not be elaborated further here. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the shape of a cemented carbide according to an embodiment of this application.

[0016] Figure 2 This is a schematic diagram of the channels of a honeycomb carbon cup according to an embodiment of this application.

[0017] Figure 3 This is a schematic diagram of the preparation process of a polycrystalline diamond-hard carbide composite tool according to an embodiment of this application.

[0018] Figure 4 This is a schematic diagram of the preparation process of a polycrystalline diamond-hard carbide composite tool according to another embodiment of this application.

[0019] Figure 5 This is a schematic diagram of the structure of a composite block according to an embodiment of this application.

[0020] Reference numerals: 10: base; 11: outer contour of the base as an orthographic projection in the axial direction; 20: boss; 21: outer contour of the boss as an orthographic projection in the axial direction; d: gap; 30: carbon cup; 41: magnesium oxide cup; 42: pyrophyllite block; 43: pyrophyllite ring; 44: dolomite ring; 45: steel cap; 46: barium zirconate tube; 47: dolomite insulation tube; 48: magnesium oxide sheet; 49: graphite tube; 50: graphite column; 51: graphite sheet; 52: molybdenum circle. Detailed Implementation

[0021] The embodiments of this application are described in detail below, with examples of these embodiments illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application.

[0022] In existing processes, the polycrystalline diamond layer of polycrystalline diamond-carbide composite tools needs to be welded to the surface of the carbide substrate. This results in weak interfacial bonding strength between the carbide and polycrystalline diamond, insufficient impact resistance, and a low heat resistance threshold. This method is no longer suitable for the machining requirements of composite tools under extreme working conditions and also restricts its machining efficiency. In addition, due to the limitations of existing manufacturing processes, it is impossible to achieve precise forming of complex cutting edges. For example, the current process first cuts the polycrystalline diamond composite sheet into different shaped cutting tips and then welds them onto the carbide substrate of the composite tool. However, it is difficult to achieve complex cutting edges such as arc surfaces, spirals, or curved surfaces using welding methods. Moreover, the forming accuracy of the cutting edge directly affects the precision and efficiency of composite tool machining, further restricting its adaptability to the needs of high-end manufacturing scenarios.

[0023] Based on the above research, this application pre-processes cemented carbide into a specific shape and coats a layer on part of its surface. This coating layer can enhance the interfacial bonding strength between cemented carbide and polycrystalline diamond, significantly improving the service life and high-temperature stability of the composite tool. Furthermore, the method of sintering polycrystalline diamond onto the cemented carbide substrate has a higher interfacial bonding strength compared to traditional welded tools, and it is easier to achieve precise forming of complex cutting edges.

[0024] A first aspect of this application provides a method for preparing polycrystalline diamond-cement composite cutting tools, comprising: S10: A cemented carbide is provided, the cemented carbide including a connected base 10 and a boss 20, the orthographic projection of the boss 20 in the axial direction falling inside the orthographic projection of the base 10 in the axial direction, and there is a gap d between the outer contour line 11 of the orthographic projection of the base in the axial direction and the outer contour line 21 of the orthographic projection of the boss in the axial direction. (See schematic diagram). Figure 1 The image below.

[0025] In this step, a cylindrical carbide bar is machined into a specific shape with a connected base and a boss. The ratio of the axial dimension of the base to the axial dimension of the boss is not specifically limited and can be selected according to the specific specifications of the composite tool. The radial diameter of the base is larger than the radial diameter of the boss. In some embodiments, the carbide can be... Figure 1 The shape shown in (a) is shown in the figure; in other embodiments, the cemented carbide may be used. Figure 1 The shape shown in (b) is shown in the image.

[0026] According to embodiments of this application, the cemented carbide comprises tungsten carbide and cobalt. Therefore, the cemented carbide possesses high hardness, wear resistance, and high-temperature resistance, thereby contributing to improved hardness and high-temperature performance of composite cutting tools.

[0027] S20: The surface of the boss is acid-washed to remove cobalt, resulting in a roughened cemented carbide.

[0028] In this step, acid etching to remove cobalt from the boss surface can dissolve the cobalt on the boss surface, forming a porous structure, which makes the coating layer formed in subsequent processes more bonded to the boss; at the same time, the boss surface still retains the tungsten carbide skeleton to maintain the mechanical strength of the cemented carbide.

[0029] According to an embodiment of this application, cobalt removal by acid etching includes immersing the bosses in a nitric acid solution at a temperature of 20°C-25°C for 40-50 minutes. Nitric acid, with its strong oxidizing properties, helps to precisely control the cobalt removal depth at the aforementioned temperature and time, while ensuring the integrity of the porous structure and preventing framework collapse.

[0030] According to the embodiments of this application, the solubility of nitric acid is 5 mol / L-6.5 mol / L. Therefore, a suitable concentration ensures a moderate reaction rate in the cobalt removal process, thereby obtaining a uniform porous structure.

[0031] According to embodiments of this application, after acid pickling to remove cobalt, the cemented carbide is further washed with deionized water until the pH reaches 7, and then subjected to a 1×10⁻⁶ ppm process. -2 Drying is performed at a vacuum of 80℃-100℃ for 3-5 hours. Washing removes residual nitric acid solution from the boss surface, preventing excessive corrosion; drying at the above temperature and time facilitates the thorough removal of residual deionized water from the porous structure.

[0032] According to an embodiment of this application, the cobalt content of the boss after drying is less than 2%. This is beneficial for enhancing the bonding strength between the coating layer formed in subsequent processes and the boss.

[0033] According to embodiments of this application, the decobalt removal depth is 30µm-50µm, specifically 30µm, 35µm, 40µm, 45µm, 50µm, or any range between two of these. Therefore, within this depth range, sufficient adhesion area can be formed while maintaining the integrity of the tungsten carbide skeleton, ensuring that the cemented carbide still possesses excellent hardness and wear resistance, thereby guaranteeing the structural stability of the composite tool. If the depth is too large, it may excessively damage the tungsten carbide skeleton, weakening the support force on the boss surface and thus reducing the impact resistance of the composite tool; if the depth is too small, the porous structure layer may be too thin, resulting in a reduced specific surface area and thus a decrease in the bonding strength between the coating layer and the boss.

[0034] S30: A coating layer is formed on the surface of the boss to obtain a coated cemented carbide, wherein the coating layer comprises elemental Ti powder, TiC, B4C, and Y2O. 3。

[0035] According to embodiments of this application, the coating layer is formed by at least one of plasma spraying, physical vapor deposition, chemical vapor deposition, and laser cladding. As a specific example, laser cladding is used. Therefore, laser cladding is simple to operate and has low cost.

[0036] As an example, the synthesis process of laser cladding coating includes: using a high-energy laser beam as the core energy source, the metallurgical preparation of the coating is achieved through the interaction between the laser and the material. The specific principle is as follows: a mixture of high-purity Ti elemental powder, TiC, B4C, and Y2O3 powder is placed around the boss of a cemented carbide rod. The laser beam is focused on the interface region between the composite powder and the rod according to a preset trajectory. The high energy generated after focusing instantly creates a local high temperature of several thousand degrees Celsius (temperatures can reach over 2000℃). The Ti elemental powder melts rapidly at this high temperature, forming a uniformly distributed molten metal pool, providing a high-temperature reaction environment and matrix raw materials for subsequent reactions. Liquid Ti reacts with B4C in the mixed powder at high temperature, causing B4C to decompose and release C element. C combines with Ti to form a new TiC phase. Simultaneously, the existing TiC particles in the mixed powder act as nucleation cores, guiding the uniform growth of the newly formed TiC phase, providing a strengthening foundation for the coating. Simultaneously, liquid Ti slowly diffuses towards the surface of the boss, interpenetrating with components such as WC and Co in the cemented carbide to form an interdiffusion layer with mixed components, laying the structural foundation for the bonding between the coating layer and the cemented carbide. As the laser beam moves along the preset trajectory, the molten metal pool area that has completed the reaction moves out of the laser's invasive range and solidifies during rapid cooling. Finally, a coating layer is formed around the boss of the cemented carbide bar. This coating layer uses Ti as the matrix, uniformly distributing the TiC phase, and achieves a high-strength metallurgical bond with the cemented carbide boss through the bridging effect of the TiC phase and the component fusion of the interdiffusion layer. During the rapid solidification process of laser cladding, Y₂O₃ acts as a heterogeneous nucleation core, promoting the non-uniform nucleation of hard phases such as TiC in the molten pool and refining the grain size. Refined grain structure can improve the density and toughness of coating and reduce cracking tendency. In addition, Y2O3 has high chemical stability and can react with impurities in the molten pool (such as O, S, etc.) to generate high melting point oxides or rare earth compounds, purifying the grain boundaries. Pure grain boundaries can enhance the metallurgical bonding force between the coating and the cemented carbide bosses and reduce interface defects.

[0037] According to embodiments of this application, the mass ratio of Ti elemental powder, TiC, B4C, and Y2O3 is 30-68:15-34:15-34:2, specifically 30:34:34:2, 30:15:15:2, or any range between two of these. The mass ratio of TiC to B4C is 1:1. Therefore, within the above-mentioned mass ratio range, it helps to improve the hardness and wear resistance of the coating layer, and also increases the bonding strength between the coating layer and the boss surface, thereby extending the service life of the composite tool.

[0038] According to embodiments of this application, the particle size of the Ti elemental powder is 15µm-30µm, specifically 15µm, 20µm, 25µm, 30µm, or any combination thereof. Therefore, within this range, the Ti elemental powder can be more uniformly distributed in the mixture, thereby forming a more uniform coating layer during the coating process.

[0039] According to embodiments of this application, the thickness of the coating layer is 0.2mm-0.5mm, specifically 0.2mm, 0.3mm, 0.4mm, 0.5mm, or any combination thereof. Within this range, good adhesion between the coating layer and the boss surface can be ensured, while providing sufficient hardness and wear resistance. If the coating layer is too thin, it may not be able to fully fill the porous structure of the boss surface, resulting in insufficient adhesion; if the coating layer is too thick, the difference in thermal expansion coefficients between the coating layer and the boss may be greater, easily leading to cracking or peeling of the coating layer.

[0040] S40: Anneal the coated cemented carbide to obtain a cemented carbide preform.

[0041] According to an embodiment of this application, the annealing temperature is 500℃-600℃, specifically 500℃, 550℃, 600℃, or any range between two of these. Therefore, within this annealing temperature range, it helps to fully eliminate the thermal stress in the coating layer, thereby improving the bonding strength between the coating layer and the boss. If the annealing temperature is too high, it may cause cracks or peeling in the coating layer; if the annealing temperature is too low, the thermal stress in the coating layer may not be fully eliminated, thereby reducing the bonding strength between the coating layer and the boss.

[0042] According to embodiments of this application, the annealing time is 5-8 hours, specifically 5 hours, 6 hours, 7 hours, 8 hours, or any combination thereof. This annealing time helps to fully eliminate thermal stress in the coating layer, thereby improving the bonding strength between the coating layer and the boss. If the annealing time is too long, it may not improve the degree of thermal stress elimination, but instead increase time costs; if the annealing time is too short, the thermal stress in the coating layer may not be completely eliminated, leading to coating layer peeling.

[0043] S50: A carbon cup 30 is provided, the carbon cup comprising a substrate and at least one channel 31 located in the substrate, the cross-sectional view of the carbon cup being referenced. Figure 2 The cemented carbide preform is placed in the channel 31, with the preform matching the channel, and a gap exists between the coating layer and the inner wall of the channel. The gap is filled with a mixture comprising diamond powder and binder to obtain a composite tool raw material block.

[0044] In this step, a carbon sheet of a certain thickness is first processed into a carbon cup. The duct size of the carbon cup can be designed according to the shape and size of the cemented carbide preform. Then, the cemented carbide preform is placed into the duct, and the gap between the boss and the inner wall of the duct is filled with polycrystalline diamond powder and binder to form a polycrystalline diamond layer.

[0045] In some embodiments, reference is made to Figure 3 In (a), use Figure 1 The cemented carbide shown in (a) is prepared to obtain Figure 3 The thread milling cutter blank shown in (b) includes a cemented carbide base 10 and a polycrystalline diamond layer 40, which is processed to obtain... Figure 3 Different shaped thread milling cutters are shown in (c) above. In other embodiments, refer to... Figure 4 In (a), use Figure 1 The cemented carbide shown in (b) is prepared to obtain Figure 4 (b) shows a slot milling cutter blank comprising a cemented carbide base 10 and a polycrystalline diamond layer 40, which is processed to obtain... Figure 4 The finished slot end mill shown in (c) is a slot end mill.

[0046] It is understandable that there is no limit to the specific thickness of the carbon sheet; it can be selected based on the specific length of the composite tool.

[0047] According to embodiments of this application, the binder includes at least one of Co and Ni. Therefore, the binder possesses excellent ductility and adhesion, which helps to tightly bond polycrystalline diamond grains.

[0048] According to embodiments of this application, the particle size of the polycrystalline diamond powder is 2µm-10µm, specifically within the range of 2µm, 3µm, 4µm, 5µm, 6µm, 7µm, 8µm, 9µm, 10µm, or any two of these ranges. Within this range, the interparticle voids can be reduced, resulting in a denser particle packing and thus ensuring the toughness and impact resistance of the composite tool. If the particle size is too large, the binder may have difficulty completely filling the pores between the particles, thereby reducing the bonding strength between the two and the toughness of the composite tool. If the particle size is too small, agglomeration may easily occur between the particles, resulting in uneven dispersion between the binder and the polycrystalline diamond, which will also reduce the bonding strength between the two and the toughness of the composite tool.

[0049] According to embodiments of this application, the particle size of the binder is 1µm-20µm, specifically 1µm, 2µm, 5µm, 8µm, 10µm, 12µm, 15µm, 17µm, 19µm, 20µm, or any two of these ranges. Within this range, the binder can better fill the tiny gaps between polycrystalline diamond particles, improving the bonding force of the polycrystalline diamond particles and contributing to the overall strength of the composite tool. If the binder particle size is too large, it may not effectively fill the tiny gaps between the polycrystalline diamond particles, resulting in a loose structure of the polycrystalline diamond layer and a decrease in the strength and stability of the composite tool. If the binder particle size is too small, its specific surface area is large, which may cause the binder particles to agglomerate, preventing them from being uniformly dispersed within the polycrystalline diamond particles, thereby increasing the stress in the polycrystalline diamond layer and reducing the strength of the composite tool.

[0050] According to embodiments of this application, the mass ratio of the diamond powder to the binder in the mixture is 5-20:80-95, specifically 5:95, 10:90, 15:85, 20:80, or any two of these ranges. Within this range, the polycrystalline diamond particles can achieve high bonding strength, resulting in higher hardness and extended service life of the composite tool. If the mass ratio is too high, the diamond powder content will be too high, potentially increasing processing difficulty and costs significantly; if the mass ratio is too low, the diamond powder content will be too low, potentially reducing the overall strength and wear resistance of the composite tool.

[0051] According to an embodiment of this application, after the gap is filled, the composite tool raw material block is further purified, which helps to further improve the purity of the composite tool raw material block, thereby improving the strength and service life of the composite tool.

[0052] According to embodiments of this application, the purification treatment temperature is 800℃-1000℃, specifically 800℃, 850℃, 900℃, 950℃, 1000℃, or any range between two of these. Within this range, it helps to fully remove moisture and volatile impurities, improving the purity of the composite tool and thus increasing its strength and service life. If the temperature is too low, moisture and impurities may not be fully removed, resulting in a decrease in the purity of the composite tool; if the temperature is too high, it may introduce new thermal stress, causing cracks or deformation in the composite tool.

[0053] According to embodiments of this application, the purification process takes 1-2 hours, specifically 1 hour, 1.5 hours, 2 hours, or any combination thereof. This helps to thoroughly remove moisture and volatile impurities, improving the purity of the composite tool and thus increasing its strength and service life. If the time is too long, the removal of moisture and impurities will not be improved, increasing time costs; if the time is too short, moisture and impurities may not be completely removed.

[0054] S60: Sinter the composite tool raw material block to obtain a polycrystalline diamond-hard alloy composite tool precursor; perform finishing on the polycrystalline diamond-hard alloy composite tool precursor to obtain a polycrystalline diamond-hard alloy composite tool.

[0055] In this step, the composite tool raw material block is sintered in a six-sided press to make the filled polycrystalline diamond dense and form a polycrystalline diamond layer, thus obtaining the polycrystalline diamond-hard carbide composite tool precursor. After subsequent finishing, the composite tool is obtained.

[0056] According to an embodiment of this application, before sintering, the process further includes: placing the composite tool raw material block into a magnesium oxide cup 41 to obtain an inner assembly block; then assembling the inner assembly block with the following components: pyrophyllite block 42, pyrophyllite ring 43, dolomite ring 44, steel cap 45, barium zirconate tube 46, dolomite insulation tube 47, magnesium oxide sheet 48, graphite tube 49, graphite column 50, graphite sheet 51, and molybdenum circle 52, to form a composite block. A schematic diagram of the composite block is shown below. Figure 5 Therefore, the above materials can play the roles of pressure transmission, heat preservation, and sealing during the sintering process, creating a high-pressure, high-temperature, clean, and stable sintering environment for the composite tool raw material block. Ultimately, this ensures that the composite tool raw material block can be uniformly dense, reducing defects and thus improving the performance of the composite tool.

[0057] According to embodiments of this application, the sintering pressure is 4 GPa-5.5 GPa, specifically within the range of 4 GPa, 4.5 GPa, 5 GPa, 5.5 GPa, or any two thereof. Within this pressure range, close contact between the components in the coating layer and the polycrystalline diamond powder can be promoted, reducing porosity and enhancing the metallurgical bonding at the interface between the coating layer and the polycrystalline diamond powder. If the sintering pressure is too high, stress concentration may occur at the interface between the coating layer and the polycrystalline diamond powder due to excessive compression, leading to cracking; if the sintering pressure is too low, insufficient contact between the coating layer and the polycrystalline diamond powder may result in weak interfacial bonding and easy delamination.

[0058] According to embodiments of this application, the sintering temperature is 1300℃-1500℃, specifically 1300℃, 1350℃, 1400℃, 1450℃, 1500℃, or any range between two of these. Within this temperature range, it facilitates the metallurgical bonding of the components in the coating layer with the polycrystalline diamond powder interface, further promoting densification and enhancing interlayer bonding strength. If the temperature is too high, it may lead to excessive growth of polycrystalline diamond grains, thereby reducing the strength of the composite tool; if the temperature is too low, the atomic diffusion rate is slow, which may result in insufficient metallurgical bonding between the coating layer and the polycrystalline diamond powder interface, leading to low densification and weak bonding.

[0059] According to embodiments of this application, the sintering time is 10-20 minutes, specifically 10 minutes, 12 minutes, 14 minutes, 16 minutes, 18 minutes, 20 minutes, or any combination thereof. Within this time range, it facilitates sufficient metallurgical bonding between the coating layer and the diamond powder interface, completely eliminating porosity and achieving strong bonding strength. If the time is too long, it may lead to excessive growth of polycrystalline diamond grains, thereby reducing the strength of the composite tool; if the time is too short, it may lead to insufficient metallurgical bonding between the coating layer and the polycrystalline diamond powder interface, thereby reducing the bonding strength at the interface.

[0060] According to the embodiments of this application, there are no specific limitations on the finishing method. The appropriate machining method can be flexibly selected according to the cutting edge size of the required composite tool or the required accuracy.

[0061] A second aspect of this application proposes a composite cutting tool prepared by the method described above. This composite cutting tool possesses all the features and advantages of the method described above for preparing composite cutting tools, which will not be elaborated further here.

[0062] The embodiments of this application are described in detail below.

[0063] Example 1 1. Machining cemented carbide into the following shapes: Figure 1 The shape shown in (a) includes the base and the boss.

[0064] 2. The above-mentioned cemented carbide was acid-washed with a 6.5 mol / L nitric acid solution for 40 min to remove cobalt, achieving a cobalt removal depth of 35 μm. The surface cobalt content was measured to be 1.5% at this point. After acid washing and cobalt removal, the cemented carbide was washed with deionized water until pH=7 and then subjected to vacuum at 100℃ (vacuum degree 1×10⁻⁶). -2 Dry for 5 hours (Pa); 3. Ti elemental powder (particle size 15 μm), TiC, B4C, and Y2O3 were mixed in a mass ratio of 30:34:34:2. Then, under a nitrogen atmosphere, the mixture was laser-clad to form a 0.5 mm coating layer on the boss surface. Subsequently, it was annealed at 500°C for 8 hours to obtain the coated cemented carbide. 4. Process the carbon sheet into a honeycomb-shaped carbon cup. Mix polycrystalline diamond powder and cobalt binder at a mass ratio of 90:10 to obtain a mixture. Then, place the cemented carbide-coated material into the channels of the honeycomb-shaped carbon cup, ensuring the cemented carbide base matches the channel size. At this point, there is a gap between the boss and the inner wall of the channel. Fill the gap with the mixture, cover it with the carbon sheet, and obtain the composite tool raw material block. 5. The composite tool raw material block is purified at 800℃ for 2 hours, and then placed in a magnesium oxide cup to obtain an inner assembly block; the inner assembly block is assembled with pyrophyllite blocks, pyrophyllite rings, dolomite rings, steel caps, barium zirconate tubes, etc. to form a composite block; 6. Place the composite block into a six-sided press and sinter for 20 minutes at a sintering pressure of 5 GPa and a sintering temperature of 1400℃. After cooling, the composite tool blank is obtained.

[0065] 7. Weld the cemented carbide base of the above blank onto another cemented carbide tool base, and obtain a composite tool after machining.

[0066] Example 2 Same as Example 1, except that the mass ratio of Ti elemental powder (particle size of 20 μm), TiC, B4C and Y2O3 is 68:15:15:2.

[0067] Comparative Example 1 Same as Example 1, except that the coating layer is formed directly without acid washing to remove cobalt in step 2.

[0068] Comparative Example 2 Same as Example 1, except that no coating is applied after acid washing to remove cobalt.

[0069] As can be seen from the data in Table 1, after 50 cycles at 800℃... After thermal cycling at 25 °C, the interfacial strength and high-temperature strength retention rates of Examples 1 and 2 remained at high levels. In contrast, Comparative Examples 1 and 2 exhibited lower interfacial strengths and significantly reduced strength retention rates at high temperatures. This indicates that the polycrystalline diamond-cement composite tool prepared by the method described in this application can significantly improve the interfacial strength between cemented carbide and polycrystalline diamond, as well as the high-temperature stability of the composite tool.

[0070] Table 1

[0071] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0072] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0073] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A method for preparing polycrystalline diamond-cement composite cutting tools, characterized in that, include: A cemented carbide is provided, the cemented carbide including a connected base and a boss, the orthographic projection of the boss in the axial direction falling inside the orthographic projection of the base in the axial direction, and there is a gap between the outer contour line of the orthographic projection of the base in the axial direction and the outer contour line of the orthographic projection of the boss in the axial direction. The surface of the boss is acid-washed to remove cobalt; A coating layer is formed on the surface of the boss to obtain a coated cemented carbide, wherein the coating layer comprises elemental Ti powder, TiC, B4C, and Y2O3; The coated cemented carbide is annealed to obtain a cemented carbide preform; A carbon cup is provided, the carbon cup comprising a matrix and at least one channel located in the matrix; The cemented carbide preform is placed in the channel, the cemented carbide preform matches the channel, and there is a gap between the coating layer and the inner wall of the channel; The gap is filled with a mixture of diamond powder and binder to obtain a composite tool raw material block; The composite tool raw material block was sintered under a pressure of 4GPa-5GPa to obtain a polycrystalline diamond-hard alloy composite tool precursor. The polycrystalline diamond-cement composite tool precursor is precision machined to obtain the polycrystalline diamond-cement composite tool.

2. The method according to claim 1, characterized in that, At least one of the following conditions must be met: The mass ratio of the Ti elemental powder, TiC, B4C, and Y2O3 is 30-68:15-34:15-34:2, and preferably the mass ratio of TiC to B4C is 1:

1. The thickness of the coating layer is 0.2mm-0.5mm.

3. The method according to claim 1, further comprising: The raw material block for the composite cutting tool is purified.

4. The method according to claim 3, wherein the purification process comprises: The composite tool raw material block is treated at 800℃-1000℃ for 1-2 hours.

5. The method according to claim 1, characterized in that, At least one of the following conditions must be met: The acid used in the pickling includes nitric acid; The concentration of the acid used in the pickling process is 5 mol / L-6.5 mol / L; The pickling time is 40-50 minutes.

6. The method according to claim 1, characterized in that, At least one of the following conditions must be met: The binder includes at least one of Co and Ni; In the mixture, the mass ratio of the diamond powder to the binder is 5-20:80-95.

7. The method according to claim 1, characterized in that, The annealing satisfies at least one of the following conditions: The annealing temperature is 500 ℃-600 ℃; The annealing time is 5 h-8 h.

8. The method according to claim 1, wherein the sintering further comprises: The composite tool raw material blocks are assembled into a composite block and sintered in a six-sided press at a temperature of 1300℃-1500℃ for 10min-20min.

9. A polycrystalline diamond-hard carbide composite tool, prepared by any one of claims 1 to 8.

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