High-temperature-resistant polycrystalline wire drawing die and preparation method thereof

Abstract

The invention discloses a high-temperature-resistant polycrystalline wire-drawing die and a preparation method thereof, and relates to the technical field of wire-drawing dies, the die comprises a boron carbide whisker reinforced silicon carbide ceramic matrix, a modified composite polycrystalline working layer and a titanium carbide-tungsten carbide-cobalt multiphase gradient transition layer between the boron carbide whisker reinforced silicon carbide ceramic matrix and the modified composite polycrystalline working layer; the working layer contains coarse and fine graded diamond particles, tungsten carbide-titanium carbide composite particles and a rare earth modified cobalt-nickel alloy binding agent. The preparation method comprises the steps of matrix preparation, pretreatment, gradient transition layer spraying, rare earth modified binding agent preparation, polycrystalline material mixing, compression molding and step-by-step sintering. According to the invention, the matrix toughness is enhanced by the whiskers, the wear resistance and high temperature resistance of the working layer are enhanced by the graded particles and the modified binding agent, and the interface combination is optimized by the gradient transition layer, so that the problems of fragile matrix, easy damage of the working layer and easy stripping of the interface of the traditional mold are solved, the overall service performance of the mold is obviously improved, and the mold is suitable for industrial production.

Description

Technical Field

[0001] This invention relates to the field of wire drawing die preparation technology, specifically to a high-temperature resistant polycrystalline wire drawing die and its preparation method. Background Technology

[0002] Wire drawing dies are core tools in the cold drawing process of metal wires. Their service environment must withstand the local high temperature generated by the high-speed friction of the wire, the axial pressure during the drawing process, and the shear stress between the wire and the inner wall of the die. Therefore, there are stringent requirements for the high temperature resistance, wear resistance, interface bonding stability, and matrix mechanical properties of the die. With the increasing demand for high-precision and high-strength metal wires in fields such as new energy and aerospace, traditional polycrystalline wire drawing dies have gradually exposed many performance shortcomings and are difficult to adapt to the use requirements of high-end manufacturing scenarios. Regarding the mold matrix, existing technologies mostly use pure silicon carbide ceramics as the matrix material. Although it has certain high temperature resistance and chemical stability, it is brittle and cracks in the crystal structure are prone to propagate rapidly along the grain boundaries. When subjected to impact loads or temperature fluctuations during the drawing process, the matrix is ​​prone to fracture, leading to the overall failure of the mold. Some improvement schemes attempt to improve toughness by adding granular reinforcing phases, but the interfacial bonding area between the particles and the matrix is ​​limited, resulting in poor reinforcement and stress concentration within the matrix. For polycrystalline working layers, traditional formulations often use diamond particles of a single size. If coarse particles are used, the working layer lacks density and is prone to porosity defects, leading to scratches on the wire surface. If fine particles are used, although density can be improved, wear resistance is weak, resulting in a short die life. At the same time, the binder of the working layer is mostly a common cobalt-nickel alloy, which is prone to grain growth and alloy softening under high temperature conditions, failing to provide stable support and bonding for the diamond particles, causing the working layer particles to fall off. In addition, some solutions add single hard particles (such as tungsten carbide or titanium carbide) for auxiliary reinforcement, but single particles cannot simultaneously achieve a balance between wear resistance and high temperature resistance, and cannot form a synergistic reinforcement effect with diamond particles. At the interface bonding level, the material properties of the substrate and the polycrystalline working layer are significantly different. The thermal expansion coefficients of the silicon carbide ceramic substrate and the diamond-metal bonded working layer are mismatched. Under temperature changes during mold preparation and service, large thermal stress is easily generated at the interface. Existing technologies mostly adopt direct composite methods, lacking an effective interface transition structure, resulting in low bonding strength between the working layer and the substrate. Under high temperature conditions, interlayer delamination is very likely to occur, causing the mold to be scrapped prematurely.

[0003] Therefore, in order to solve the above problems and improve the high temperature resistance, wear resistance and interface stability of the mold, a high temperature resistant polycrystalline wire drawing mold and its preparation method are proposed. Summary of the Invention

[0004] The present invention aims to provide a high-temperature resistant polycrystalline wire drawing die and its preparation method to solve the problems of brittle matrix, easily damaged working layer and easy peeling of interface in traditional dies.

[0005] To achieve the above objectives, the present invention provides the following technical solution: The technical solution provided by this invention is: A high-temperature resistant polycrystalline wire drawing die includes a die substrate and a modified composite polycrystalline working layer; The mold matrix is ​​a boron carbide whisker-reinforced silicon carbide ceramic matrix, wherein the boron carbide whiskers are 5-10 parts and the silicon carbide ceramic powder is 90-95 parts. The modified composite polycrystalline working layer is laminated onto the inner wall of the wire drawing hole of the mold substrate. The modified composite polycrystalline working layer is composed of the following components in parts: 65-80 parts diamond particles, 5-15 parts tungsten carbide-titanium carbide composite particles, and 10-20 parts rare earth modified cobalt-nickel alloy binder. The diamond particles are graded by coarse and fine particle size distribution, with fine particles of 5-10μm accounting for 40-60 parts of the total diamond particles and coarse particles of 20-40μm accounting for 40-60 parts of the total diamond particles. The ratio of tungsten carbide to titanium carbide in tungsten carbide-titanium carbide composite particles is 2:1 to 3:1.

[0006] Furthermore, the rare earth modified cobalt-nickel alloy binder contains cobalt to nickel in a ratio of 3:1 to 5:1, and also contains 1-3% molybdenum powder and 0.5-1.5% rare earth mixed powder, which is a mixture of cerium and lanthanum, with a ratio of cerium to lanthanum of 1:1 to 2:1.

[0007] Furthermore, a gradient transition layer is provided between the mold substrate and the modified composite polycrystalline working layer. The gradient transition layer is a titanium carbide-tungsten carbide-cobalt multiphase gradient layer. From the side closer to the substrate to the side closer to the polycrystalline working layer, the amount of cobalt gradually decreases from 15-20 parts to 5-10 parts, the amount of titanium carbide gradually increases from 5-10 parts to 15-20 parts, and the amount of tungsten carbide gradually decreases from 70-80 parts to 70-75 parts.

[0008] A method for preparing a high-temperature resistant polycrystalline wire drawing die includes the following steps: S1: Matrix Preparation: Boron carbide whiskers (10-50 μm in length, 0.5-2 μm in diameter) are calcined at 1000-1100℃ for 2-3 hours to remove surface impurities. Silicon carbide ceramic powder (1-5 μm in particle size) is dried at 800-900℃ for 4-6 hours. The two materials are mixed at a ratio of 5-10 parts boron carbide whiskers to 90-95 parts silicon carbide ceramic powder. 3-5% polyvinyl alcohol binder and 10-15% deionized water are added to the mixture. The mixture is then ground in a planetary ball mill at a ball-to-material ratio of 4:1-6:1 and a speed of 150-200 r / min. After 1-2 hours, spray granulation (inlet air temperature 180-200℃, outlet air temperature 80-100℃) is used to produce particles with a diameter of 50-100μm. The granulated particles are then filled into a mold and hot-pressed at 180-220℃ and 50-80MPa for 10-15 minutes to obtain a matrix green body. The green body is then heated to 2050-2200℃ under argon protection and held for 3-4 hours at a heating rate of 3-5℃ / min. It is then cooled to room temperature in the furnace and machined to form a boron carbide whisker-reinforced silicon carbide ceramic matrix with wire drawing holes. S2: Matrix pretreatment: The boron carbide whisker-reinforced silicon carbide ceramic matrix is ​​ultrasonically cleaned with acetone for 30-40 min and ultrasonically cleaned with deionized water for 20-30 min in sequence. Then, the inner wall of the wire drawing hole is sandblasted with 100-150 mesh silicon carbide sand at a treatment pressure of 0.4-0.6 MPa. After treatment, the inner wall roughness Ra is controlled at 1.5-3.0 μm. S3: Gradient transition layer preparation: According to the component gradient ratio of the gradient transition layer and the component gradient requirements from the side near the substrate to the side near the polycrystalline working layer, prepare 3-5 groups of titanium carbide-tungsten carbide-cobalt mixed powders respectively. The composition of each group of powders meets the following requirements: Group 1 near the substrate: 15-20 parts cobalt, 5-10 parts titanium carbide, and 75-80 parts tungsten carbide; Group 2 near the polycrystalline working layer: 5-10 parts cobalt, 15-20 parts titanium carbide, and 70-75 parts tungsten carbide; The content of each component in the intermediate group changes linearly and continuously along the above direction; Plasma spraying process is used, starting from the first group of powders and spraying layer by layer, with a spraying power of 30-40kW, a spraying temperature of 900-1000℃, a single coating thickness of 20-30μm, and a total transition layer thickness of 60-150μm; S4: Preparation of rare earth modified binder: Weigh cobalt powder and nickel powder according to the ratio of cobalt to nickel 3:1-5:1, add 1-3% molybdenum powder and 0.5-1.5% rare earth mixed powder (cerium to lanthanum ratio 1:1-2:1) according to the binder mass, melt at 1500-1600℃ for 2-3 hours under argon protection, quench with water and ball mill to a particle size of 5-10μm to obtain rare earth modified cobalt-nickel alloy binder; S5: Polycrystalline material preparation: Weigh diamond particles (40-60% each of 5-10μm fine particles and 20-40μm coarse particles), tungsten carbide-titanium carbide composite particles (tungsten carbide to titanium carbide ratio 2:1-3:1) and the binder obtained in S4 according to the following proportions. Add them to a planetary ball mill, using ethanol as the dispersant. The amount of dispersant is 12-18% of the total mass of the mixture. Ball mill at a ball-to-material ratio of 6:1-10:1 and a speed of 250-350 r / min for 3-5 h. Then, vacuum dry at 90-110℃ for 5-7 h to obtain polycrystalline material. S6: Compression molding: The polycrystalline material is uniformly filled into the drawing holes of the matrix with a gradient transition layer, and cold isostatic pressing is used for molding. The pressure is 180-220MPa and the pressure is held for 8-12min. S7: Stepwise sintering: First, under a vacuum degree ≤5×10 -3 Low-temperature pre-firing under Pa environment: temperature 650-750℃, hold for 1.5-2.5h; then heat to 1450-1550℃ at a rate of 6-10℃ / min, apply 6-9MPa pressure, hold for 2.5-3.5h, purged with argon gas during the heating stage, and finally cooled to room temperature with the furnace to obtain the final product.

[0009] Furthermore, during S3 spraying, the distance between the spray gun and the inner wall of the wire drawing hole is maintained at 80-100mm, and the spraying angle is 90°.

[0010] Furthermore, in S5, agate balls are used as the grinding media in the ball mill. The ball mill is paused for 5 minutes every 30 minutes during operation to avoid overheating. The vacuum degree of vacuum drying is ≥0.09MPa.

[0011] Furthermore, after the S7 medium-low temperature pre-firing is completed, the vacuum environment is replaced with inert gas 2-3 times, and the pressure is held for 10-15 minutes after each replacement before the temperature is raised for sintering.

[0012] The beneficial effects of this technical solution are: (1) The mold matrix adopts a boron carbide whisker reinforced silicon carbide ceramic structure. The boron carbide whiskers are needle-shaped and can form a three-dimensional network support structure in the silicon carbide ceramic matrix, which can effectively prevent the initiation and propagation of cracks and make up for the brittle defects of pure silicon carbide ceramic matrix. At the same time, silicon carbide ceramic itself has excellent high temperature resistance and chemical stability, and has good physical and chemical compatibility with boron carbide whiskers. The matrix formed by the combination of the two has both high strength and high toughness and can withstand the impact load and high temperature during the drawing process.

[0013] (2) In the modified composite polycrystalline working layer, the diamond particles adopt a coarse and fine particle size distribution design. The fine particles can fill the gaps between the coarse particles to form a dense particle packing structure and reduce the porosity inside the working layer. In the tungsten carbide-titanium carbide composite particles, tungsten carbide has high hardness and wear resistance, while titanium carbide has excellent high temperature resistance and chemical stability. The two work together to complement the diamond particles and further enhance the overall wear resistance and high temperature resistance of the working layer. In the rare earth modified cobalt-nickel alloy binder, rare earth elements can refine the alloy grains and improve the microstructure uniformity of the binder. Molybdenum elements can improve the high temperature stability of the binder and prevent the binder from softening at high temperatures, ensuring stable bonding support for the diamond particles and tungsten carbide-titanium carbide composite particles.

[0014] (3) The gradient transition layer between the mold substrate and the modified composite polycrystalline working layer is a titanium carbide-tungsten carbide-cobalt composite structure. Its composition changes continuously along the direction from the substrate to the working layer. The composition closer to the substrate is closer to the material properties of the substrate, and the composition closer to the working layer is more compatible with the material properties of the working layer. Through the gradient transition of the composition, the difference in thermal expansion coefficient between the two can be effectively buffered, the thermal stress concentration at the interface can be reduced, the interfacial bonding between the working layer and the substrate can be strengthened, and the interlayer delamination phenomenon can be avoided.

[0015] (4) The components have good physical and chemical compatibility. The combination of boron carbide whiskers and silicon carbide ceramics, the connection between the gradient transition layer and the matrix and working layer, and the interaction between diamond particles, composite particles and binder inside the working layer form a continuous performance transition system from the matrix to the working layer. The advantages of each component can be fully utilized, and the overall service performance of the mold can be improved in a synergistic way. Attached Figure Description

[0016] Figure 1 This is a flowchart illustrating the preparation process of a high-temperature resistant polycrystalline wire drawing die and its preparation method proposed in this invention. Detailed Implementation

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] The following experimental materials were used: boron carbide whiskers (length 10-50 μm, diameter 0.5-2 μm), silicon carbide ceramic powder (particle size 1-5 μm), polyvinyl alcohol binder, diamond particles (5-10 μm, 20-40 μm), tungsten carbide powder (particle size 3-8 μm), titanium carbide powder (particle size 2-6 μm), cobalt powder (particle size 5-10 μm), nickel powder (particle size 5-10 μm), molybdenum powder (particle size 1-3 μm), rare earth mixed powder (cerium powder, lanthanum powder, particle size 2-5 μm), ethanol (analytical grade), and acetone (analytical grade).

[0019] The specific implementation process is as follows: Example 1: Please see Figure 1 The present invention provides a technical solution: a high-temperature resistant polycrystalline wire drawing die and its preparation method, comprising the following steps: S1: Matrix Preparation: Take 5g of boron carbide whiskers and calcine them at 1000℃ for 3h to remove surface impurities; take 95g of silicon carbide ceramic powder and dry it at 800℃ for 6h to remove moisture. Mix the pretreated boron carbide whiskers with the silicon carbide ceramic powder, add 4.5g of polyvinyl alcohol binder (3% of the total mass of the mixed raw materials) and 15g of deionized water (15% of the total mass of the mixed raw materials), place the mixture in a planetary ball mill, and mix at a ball-to-material ratio of 4:1 and a speed of 150r / min for 2h. After mixing, use a spray granulation process. Granulation was carried out with an inlet air temperature of 180℃ and an outlet air temperature of 80℃ to produce particles with a diameter of 50-80μm. The granulated particles were filled into a special mold and the matrix green body was prepared by hot pressing. The molding temperature was set to 180℃, the molding pressure to 50MPa, and the holding time to 15min. The matrix green body was placed in a sintering furnace and heated to 2050℃ at a heating rate of 3℃ / min under an argon protective atmosphere. It was held for 4h and then cooled to room temperature with the furnace. The matrix green body was then machined to form a boron carbide whisker-reinforced silicon carbide ceramic matrix with wire drawing holes. S2: Matrix pretreatment: The machined boron carbide whisker-reinforced silicon carbide ceramic matrix was placed in acetone solution and ultrasonically cleaned for 40 minutes to remove surface oil. Then it was placed in deionized water and ultrasonically cleaned for 30 minutes to remove residual acetone. After cleaning, it was dried for later use. The inner wall of the wire drawing hole of the boron carbide whisker-reinforced silicon carbide ceramic matrix was sandblasted using a sandblasting device. 100-mesh silicon carbide sand was selected as the sandblasting medium and the treatment pressure was set to 0.4MPa. After treatment, the roughness Ra of the inner wall of the wire drawing hole was controlled at 1.5-2.0μm. S3: Gradient transition layer preparation: According to the composition gradient requirements of the gradient transition layer from the side near the boron carbide whisker-reinforced silicon carbide ceramic matrix to the side near the modified composite polycrystalline working layer, three groups of titanium carbide-tungsten carbide-cobalt mixed powders were prepared respectively. The first group (close to the boron carbide whisker-reinforced silicon carbide ceramic matrix) of mixed powder consists of: 15 parts cobalt, 8 parts titanium carbide, and 77 parts tungsten carbide. The second group (intermediate group) of mixed powder consists of: 12 parts cobalt, 12 parts titanium carbide, and 76 parts tungsten carbide; The third group (near the modified composite polycrystalline working layer) of mixed powder consists of: 8 parts cobalt, 17 parts titanium carbide, and 75 parts tungsten carbide. Each group of mixed powders was placed in a three-dimensional mixer and mixed at 80 r / min for 2 hours to ensure uniformity of components. Plasma spraying equipment was used to spray layer by layer starting from the first group of mixed powders. The spraying power was set to 30 kW, the spraying temperature to 900 ℃, the thickness of a single coating layer was controlled to 30 μm, and the total thickness of the gradient transition layer was 90 μm. During the spraying process, the distance between the spray gun and the inner wall of the wire drawing hole was kept at 80 mm, and the spraying angle was 90°. S4: Preparation of rare earth modified cobalt-nickel alloy binder: Weigh 7.5g of cobalt powder and 2.5g of nickel powder according to a cobalt to nickel ratio of 3:1. Add 0.1g of molybdenum powder (1% of the total mass of the rare earth modified cobalt-nickel alloy binder) and 0.05g of rare earth mixed powder (0.5% of the total mass of the rare earth modified cobalt-nickel alloy binder). The rare earth mixed powder is a mixture of cerium and lanthanum, with 0.025g of cerium powder and 0.025g of lanthanum powder, and the ratio of cerium to lanthanum is 1:1. Place the above raw materials in a vacuum melting furnace and melt at 1500℃ for 3 hours under an argon protective atmosphere. After melting, perform water quenching treatment. Place the water-quenched alloy block in a ball mill and ball mill it to a particle size of 5-8μm to obtain rare earth modified cobalt-nickel alloy binder powder. S5: Polycrystalline Material Preparation: Weigh out 65g of diamond particles, 5g of tungsten carbide-titanium carbide composite particles, and 10g of rare earth modified cobalt-nickel alloy binder according to the following proportions: The diamond particles are graded by coarse and fine particle size distribution, with 26g of fine particles (5-10μm) and 39g of coarse particles (20-40μm), accounting for 40% and 60% of the total diamond particles, respectively; the ratio of tungsten carbide to titanium carbide in the tungsten carbide-titanium carbide composite particles is 2:1, and the binder is composed of rare earth modified cobalt-nickel alloy binder. The mixture consists of 3.3g of tungsten powder and 1.7g of titanium carbide powder. The above raw materials are added to a planetary ball mill, and 10.2g of ethanol (12% of the total mass of the mixture) is added as a dispersant. Agate balls are used as the grinding medium. The ball-to-material ratio is set to 6:1, the rotation speed is 250r / min, and the mixture is ball-milled for 5h. After the ball milling is completed, the mixture is placed in a vacuum drying oven and dried for 7h at 90℃ and a vacuum degree of 0.09MPa to obtain the polycrystalline material for the modified composite polycrystalline working layer. S6: Compression molding: The prepared polycrystalline material is uniformly filled into the wire drawing holes of the boron carbide whisker-reinforced silicon carbide ceramic matrix with a gradient transition layer, and the molding is carried out by cold isostatic pressing process, with the molding pressure set at 180MPa and the holding time at 12min. S7: Step-by-step sintering: The molded blank is placed in a high-pressure sintering furnace, first under a vacuum of 5×10⁻⁶. -3 Low-temperature pre-firing was carried out under a vacuum environment of Pa, with the pre-firing temperature set at 650℃ and the holding time at 2.5h. After pre-firing, the vacuum environment was replaced twice with inert gas, and the pressure was maintained for 15min after each replacement. Then, the temperature was increased to 1450℃ at a heating rate of 6℃ / min, and a pressure of 6MPa was applied. The temperature was held for 3.5h, and argon gas was introduced for protection during the heating stage. After sintering, the furnace was cooled to room temperature to obtain a high-temperature resistant polycrystalline wire drawing mold.

[0020] Test Project Specific indicators Test Results High temperature resistance Appearance after heat preservation at 1200℃ No cracks Hardness variation rate of modified composite polycrystalline working layer 8% abrasion resistance Cumulative wire drawing length (to 0.1mm wear) 8000m Interface bonding strength Boron carbide whiskers enhance the shear strength of silicon carbide ceramic matrix and modified composite polycrystalline working layer 180MPa As can be seen from the table above, the high-temperature resistant polycrystalline wire drawing die prepared in Example 1 has basic high-temperature resistance. After holding at 1200℃, no cracks were generated in either the boron carbide whisker-reinforced silicon carbide ceramic matrix or the modified composite polycrystalline working layer, indicating that the boron carbide whisker-reinforced matrix and the modified composite polycrystalline working layer can jointly withstand the high-temperature environment. The hardness change rate of the modified composite polycrystalline working layer is 8%, reflecting that the rare earth modified cobalt-nickel alloy binder has a certain high-temperature stability, but the change rate is relatively high, which is speculated to be related to the low addition amount of rare earth mixed powder (0.5%). In terms of wear resistance, the cumulative wire drawing length reached 8000m, indicating that the coarse and fine particle size distribution of diamond particles and tungsten carbide-titanium carbide composite particles formed a certain wear-resistant structure, which can effectively resist the frictional loss during the copper wire drawing process. The interface bonding strength is 180MPa. The gradient transition layer with three groups of components effectively alleviated the interface stress between the boron carbide whisker-reinforced silicon carbide ceramic matrix and the modified composite polycrystalline working layer, and achieved a stable bond between the two.

[0021] Example 2: Please see Figure 1 The present invention provides a technical solution: a high-temperature resistant polycrystalline wire drawing die and its preparation method, comprising the following steps: S1: Matrix Preparation: 7g of boron carbide whiskers were calcined at 1050℃ for 2.5h to remove surface impurities; 93g of silicon carbide ceramic powder was dried at 850℃ for 5h to remove moisture. The pretreated boron carbide whiskers and silicon carbide ceramic powder were mixed, and 5.6g of polyvinyl alcohol binder (4% of the total mass of the mixed raw materials) and 13.5g of deionized water (13% of the total mass of the mixed raw materials) were added. The mixture was placed in a planetary ball mill and mixed at a ball-to-material ratio of 5:1 and a speed of 180r / min for 1.5h. After mixing, the mixture was spray-milled. Granulation is carried out using a granulation process, with the inlet air temperature set at 190℃ and the outlet air temperature at 90℃, to produce particles with a diameter of 60-90μm. The granulated particles are then filled into a special mold, and a matrix blank is prepared using a hot pressing molding process, with the molding temperature set at 200℃, the molding pressure at 65MPa, and the holding time at 12min. The matrix blank is then placed in a sintering furnace, and under an argon protective atmosphere, the temperature is raised to 2100℃ at a heating rate of 4℃ / min and held for 3.5h. Subsequently, it is cooled to room temperature with the furnace, and then machined to form a boron carbide whisker-reinforced silicon carbide ceramic matrix with wire drawing holes. S2: Matrix pretreatment: The machined boron carbide whisker-reinforced silicon carbide ceramic matrix was placed in acetone solution and ultrasonically cleaned for 35 minutes to remove surface oil. Then it was placed in deionized water and ultrasonically cleaned for 25 minutes to remove residual acetone. After cleaning, it was dried for later use. The inner wall of the wire drawing hole of the boron carbide whisker-reinforced silicon carbide ceramic matrix was sandblasted using a sandblasting device. 120 mesh silicon carbide sand was selected as the sandblasting medium and the treatment pressure was set to 0.5 MPa. After treatment, the roughness Ra of the inner wall of the wire drawing hole was controlled at 2.0-2.5 μm. S3: Gradient transition layer preparation: According to the composition gradient requirements of the gradient transition layer from the side near the boron carbide whisker-reinforced silicon carbide ceramic matrix to the side near the modified composite polycrystalline working layer, four groups of titanium carbide-tungsten carbide-cobalt mixed powders were prepared respectively. The first group (close to the boron carbide whisker-reinforced silicon carbide ceramic matrix) of mixed powder consists of: 17 parts cobalt, 7 parts titanium carbide, and 76 parts tungsten carbide. The second group of mixed powders consists of: 14 parts cobalt, 10 parts titanium carbide, and 76 parts tungsten carbide. The third group of mixed powders consists of: 11 parts cobalt, 13 parts titanium carbide, and 76 parts tungsten carbide. The fourth group (near the modified composite polycrystalline working layer) of mixed powder consists of: 8 parts cobalt, 19 parts titanium carbide, and 73 parts tungsten carbide. Each group of mixed powders was placed in a three-dimensional mixer and mixed at 80 r / min for 2 hours to ensure uniformity of components. Plasma spraying equipment was used to spray layer by layer starting from the first group of mixed powders. The spraying power was set to 35 kW and the spraying temperature to 950 ℃. The thickness of a single coating layer was controlled to be 25 μm and the total thickness of the gradient transition layer was 100 μm. During the spraying process, the distance between the spray gun and the inner wall of the wire drawing hole was kept at 90 mm and the spraying angle was 90°. S4: Preparation of rare earth modified cobalt-nickel alloy binder: Weigh 8g of cobalt powder and 2g of nickel powder according to a cobalt to nickel ratio of 4:1. Add 0.2g of molybdenum powder (2% of the total mass of the rare earth modified cobalt-nickel alloy binder) and 0.1g of rare earth mixed powder (1% of the total mass of the rare earth modified cobalt-nickel alloy binder). The rare earth mixed powder is a mixture of cerium and lanthanum, with 0.067g of cerium powder and 0.033g of lanthanum powder. The ratio of cerium to lanthanum is 2:1. Place the above raw materials in a vacuum melting furnace and melt at 1550℃ for 2.5h under an argon protective atmosphere. After melting, perform water quenching treatment. Place the water-quenched alloy block in a ball mill and ball mill it to a particle size of 6-10μm to obtain rare earth modified cobalt-nickel alloy binder powder. S5: Polycrystalline Material Preparation: Weigh out 72g of diamond particles, 10g of tungsten carbide-titanium carbide composite particles, and 15g of rare earth modified cobalt-nickel alloy binder according to the following proportions: The diamond particles are graded with a coarse-fine particle size distribution, consisting of 36g of fine particles (5-10μm) and 36g of coarse particles (20-40μm), with fine and coarse particles accounting for 50% and 50% of the total diamond particles, respectively; the ratio of tungsten carbide to titanium carbide in the tungsten carbide-titanium carbide composite particles is 2:1, derived from the carbonization of the tungsten carbide. The mixture consists of 6.7g of tungsten powder and 3.3g of titanium carbide powder. The above raw materials are added to a planetary ball mill, and 14.55g of ethanol (15% of the total mass of the mixture) is added as a dispersant. Agate balls are used as the grinding medium. The ball-to-material ratio is set to 8:1, the rotation speed is 300r / min, and the mixture is ball-milled for 4 hours. After the ball milling is completed, the mixture is placed in a vacuum drying oven and dried at 100℃ and 0.09MPa for 6 hours to obtain the polycrystalline material for the modified composite polycrystalline working layer. S6: Compression molding: The prepared polycrystalline material is uniformly filled into the wire drawing holes of the boron carbide whisker-reinforced silicon carbide ceramic matrix with a gradient transition layer, and the molding is carried out by cold isostatic pressing process, with the molding pressure set at 200MPa and the holding time at 10min. S7: Step-by-step sintering: The molded blank is placed in a high-pressure sintering furnace, first under a vacuum of 3×10⁻⁶. -3Low-temperature pre-firing was carried out under a vacuum environment of Pa, with the pre-firing temperature set at 700℃ and the holding time at 2h. After pre-firing, the vacuum environment was replaced three times with inert gas, and the pressure was maintained for 12min after each replacement. Then, the temperature was increased to 1500℃ at a heating rate of 8℃ / min, and a pressure of 7MPa was applied. The temperature was held for 3h, and argon gas was introduced for protection during the heating stage. After sintering, the furnace was cooled to room temperature to obtain a high-temperature resistant polycrystalline wire drawing mold.

[0022] Test Project Specific indicators Test Results High temperature resistance Appearance after heat preservation at 1200℃ No cracks Hardness variation rate of modified composite polycrystalline working layer 5% abrasion resistance Cumulative wire drawing length (to 0.1mm wear) 12000m Interface bonding strength Boron carbide whiskers enhance the shear strength of silicon carbide ceramic matrix and modified composite polycrystalline working layer 220MPa As can be seen from the table above, the high-temperature resistant polycrystalline wire drawing die prepared in Example 2 has the best overall performance. In terms of high-temperature resistance, after holding at 1200℃, neither the boron carbide whisker-reinforced silicon carbide ceramic matrix nor the modified composite polycrystalline working layer showed any cracks. Moreover, the hardness change rate of the modified composite polycrystalline working layer was only 5%, significantly lower than that in Example 1. This is due to the optimized combination of 1% rare earth mixed powder and the cerium-lanthanum ratio (2:1). The rare earth elements have a better effect on refining the alloy grains. Combined with the addition of molybdenum powder, the high-temperature stability of the rare earth modified cobalt-nickel alloy binder is greatly improved, and the wear resistance is outstanding. The cumulative wire drawing performance is excellent. With a length of 12,000m, the diamond particles are designed with an equal ratio of fine and coarse particles, which optimizes the density of the modified composite polycrystalline working layer. The 10g tungsten carbide-titanium carbide composite particles and diamond particles form a synergistic reinforcement effect, further enhancing the wear resistance of the working layer. The interfacial bonding strength reaches 220MPa. The gradient transition layer with four groups of components with varying gradients makes the compositional changes between the boron carbide whisker-reinforced silicon carbide ceramic matrix and the modified composite polycrystalline working layer more continuous, perfectly matching the performance differences between the two, minimizing interfacial stress, and achieving high-strength bonding.

[0023] Example 3: Please see Figure 1 The present invention provides a technical solution: a high-temperature resistant polycrystalline wire drawing die and its preparation method, comprising the following steps: S1: Matrix Preparation: Take 9g of boron carbide whiskers and calcine them at 1100℃ for 2h to remove surface impurities; take 91g of silicon carbide ceramic powder and dry it at 900℃ for 4h to remove moisture. Mix the pretreated boron carbide whiskers with the silicon carbide ceramic powder, add 6.3g of polyvinyl alcohol binder (5% of the total mass of the mixed raw materials) and 11g of deionized water (11% of the total mass of the mixed raw materials), place the mixture in a planetary ball mill, and mix at a ball-to-material ratio of 6:1 and a speed of 200r / min for 1h. After mixing, use a spray granulation process for further processing. Granulation was performed with an inlet air temperature of 200℃ and an outlet air temperature of 100℃ to produce particles with a diameter of 70-100μm. The granulated particles were then filled into a special mold, and a matrix green body was prepared by hot pressing. The molding temperature was set to 220℃, the molding pressure to 80MPa, and the holding time to 10min. The matrix green body was placed in a sintering furnace and heated to 2200℃ at a heating rate of 5℃ / min under an argon protective atmosphere. It was held at that temperature for 3h and then cooled to room temperature with the furnace. The resulting material was machined to form a boron carbide whisker-reinforced silicon carbide ceramic matrix with wire drawing holes. S2: Matrix pretreatment: The machined boron carbide whisker-reinforced silicon carbide ceramic matrix was placed in acetone solution and ultrasonically cleaned for 30 minutes to remove surface oil. Then it was placed in deionized water and ultrasonically cleaned for 20 minutes to remove residual acetone. After cleaning, it was dried for later use. The inner wall of the wire drawing hole of the boron carbide whisker-reinforced silicon carbide ceramic matrix was sandblasted using a sandblasting device. 150 mesh silicon carbide sand was selected as the sandblasting medium and the treatment pressure was set to 0.6 MPa. After treatment, the roughness Ra of the inner wall of the wire drawing hole was controlled at 2.5-3.0 μm. S3: Gradient transition layer preparation: According to the composition gradient requirements of the gradient transition layer from the side near the boron carbide whisker-reinforced silicon carbide ceramic matrix to the side near the modified composite polycrystalline working layer, 5 groups of titanium carbide-tungsten carbide-cobalt mixed powders were prepared respectively. The first group (close to the boron carbide whisker-reinforced silicon carbide ceramic matrix) of mixed powder consists of: 20 parts cobalt, 5 parts titanium carbide, and 75 parts tungsten carbide. The second group of mixed powders consisted of 17 parts cobalt, 9 parts titanium carbide, and 74 parts tungsten carbide. The third group of mixed powders consists of: 14 parts cobalt, 13 parts titanium carbide, and 73 parts tungsten carbide. The fourth group of mixed powders consists of: 10 parts cobalt, 17 parts titanium carbide, and 73 parts tungsten carbide. The fifth group (near the modified composite polycrystalline working layer) of mixed powder consists of: 7 parts cobalt, 20 parts titanium carbide, and 73 parts tungsten carbide. Each group of mixed powders was placed in a three-dimensional mixer and mixed at 80 r / min for 2 hours to ensure uniformity of components. Plasma spraying equipment was used to spray layer by layer starting from the first group of mixed powders. The spraying power was set to 40 kW, the spraying temperature to 1000 ℃, the thickness of a single coating layer was controlled to 20 μm, and the total thickness of the gradient transition layer was 100 μm. During the spraying process, the distance between the spray gun and the inner wall of the wire drawing hole was kept at 100 mm, and the spraying angle was 90°. S4: Preparation of rare earth modified cobalt-nickel alloy binder: Weigh 9g of cobalt powder and 1.8g of nickel powder according to a cobalt to nickel ratio of 5:1. Add 0.3g of molybdenum powder (3% of the total mass of the rare earth modified cobalt-nickel alloy binder) and 0.15g of rare earth mixed powder (1.5% of the total mass of the rare earth modified cobalt-nickel alloy binder). The rare earth mixed powder is a mixture of cerium and lanthanum, with 0.1g of cerium powder and 0.05g of lanthanum powder. The ratio of cerium to lanthanum is 2:1. Place the above raw materials in a vacuum melting furnace and melt at 1600℃ for 2 hours under an argon protective atmosphere. After melting, perform water quenching treatment. Place the water-quenched alloy block in a ball mill and ball mill it to a particle size of 5-9μm to obtain rare earth modified cobalt-nickel alloy binder powder. S5: Polycrystalline Material Preparation: Weigh out 80g of diamond particles, 15g of tungsten carbide-titanium carbide composite particles, and 20g of rare earth modified cobalt-nickel alloy binder according to the following proportions: The diamond particles are graded with a coarse-fine particle size distribution, consisting of 48g of fine particles (5-10μm) and 32g of coarse particles (20-40μm), accounting for 60% and 40% of the total diamond particles, respectively; the tungsten carbide-titanium carbide composite particles have a tungsten carbide to titanium carbide ratio of 3:1, and are prepared from tungsten carbide powder. The mixture consists of 11.25g of powdered titanium carbide and 3.75g of titanium carbide powder. The above raw materials are added to a planetary ball mill, and 17.25g of ethanol (18% of the total mass of the mixture) is added as a dispersant. Agate balls are used as the grinding medium. The ball-to-material ratio is set to 10:1, the rotation speed is 350r / min, and the mixture is ball-milled for 3h. After the ball milling is completed, the mixture is placed in a vacuum drying oven and dried for 5h at 110℃ and 0.09MPa vacuum to obtain the polycrystalline material for the modified composite polycrystalline working layer. S6: Compression molding: The prepared polycrystalline material is uniformly filled into the wire drawing holes of the boron carbide whisker-reinforced silicon carbide ceramic matrix with a gradient transition layer, and the molding is carried out by cold isostatic pressing process, with the molding pressure set at 220MPa and the holding time at 8min. S7: Step-by-step sintering: The molded blank is placed in a high-pressure sintering furnace, first under a vacuum of 2×10⁻⁶. -3Low-temperature pre-firing was carried out under a vacuum environment of 750℃ and a holding time of 1.5h. After pre-firing, the vacuum environment was replaced with inert gas three times, and the pressure was maintained for 10min after each replacement. Then, the temperature was increased to 1550℃ at a heating rate of 10℃ / min, a pressure of 9MPa was applied, and the temperature was held for 2.5h. Argon gas was introduced for protection during the heating stage. After sintering, the furnace was cooled to room temperature to obtain a high-temperature resistant polycrystalline wire drawing mold. Test Project Specific indicators Test Results High temperature resistance Appearance after heat preservation at 1200℃ No cracks Hardness variation rate of modified composite polycrystalline working layer 4% abrasion resistance Cumulative wire drawing length (to 0.1mm wear) 11000m Interface bonding strength Boron carbide whiskers enhance the shear strength of silicon carbide ceramic matrix and modified composite polycrystalline working layer 210MPa As can be seen from the table above, the high-temperature resistant polycrystalline wire drawing die prepared in Example 3 exhibits the best high-temperature resistance, with a hardness change rate of only 4% in the modified composite polycrystalline working layer. This is because the content of molybdenum powder (3%) and rare earth mixed powder (1.5%) in the rare earth modified cobalt-nickel alloy binder are the highest among the four examples. The grain refinement effect of rare earth elements and the high-temperature stabilizing effect of molybdenum elements work synergistically, resulting in the binder hardly softening at a high temperature of 1200℃. The interfacial bonding strength is 210MPa, slightly lower than that of Example 2. It is speculated that this is due to the excessive number of coating layers in the 5 groups. Minor defects exist in the interlayer bonding of the gradient transition layer, affecting the overall interface bonding effect, but still maintaining a high bonding strength. In terms of wear resistance, the cumulative wire drawing length is 11,000m. The high proportion of fine particles (60%) in the diamond particles makes the modified composite polycrystalline working layer extremely dense, effectively reducing particle shedding during the friction process. However, the reduced proportion of coarse particles (40%) leads to a slight decrease in the initial wear resistance. Nevertheless, the addition of 15g of tungsten carbide-titanium carbide composite particles (tungsten carbide to titanium carbide ratio 3:1) still ensures the overall high wear resistance of the working layer.

[0024] Example 4: Please see Figure 1 The present invention provides a technical solution: a high-temperature resistant polycrystalline wire drawing die and its preparation method, comprising the following steps: S1: Matrix Preparation: Take 10g of boron carbide whiskers and calcine them at 1050℃ for 2.5h to remove surface impurities; take 90g of silicon carbide ceramic powder and dry it at 850℃ for 5h to remove moisture. Mix the pretreated boron carbide whiskers with the silicon carbide ceramic powder, add 4.5g of polyvinyl alcohol binder (3% of the total mass of the mixed raw materials) and 13.5g of deionized water (13% of the total mass of the mixed raw materials), place the mixture in a planetary ball mill, and mix at a ball-to-material ratio of 5:1 and a speed of 180r / min for 1.5h. After mixing, use a spray mill to... Granulation is carried out using a granulation process, with the inlet air temperature set at 190℃ and the outlet air temperature at 90℃, to produce particles with a diameter of 60-90μm. The granulated particles are then filled into a special mold, and a matrix green body is prepared using a hot pressing molding process, with the molding temperature set at 200℃, the molding pressure at 70MPa, and the holding time at 12min. The matrix green body is then placed in a sintering furnace, and under an argon protective atmosphere, the temperature is raised to 2100℃ at a heating rate of 4℃ / min and held for 3.5h. Subsequently, it is cooled to room temperature with the furnace, and then machined to form a boron carbide whisker-reinforced silicon carbide ceramic matrix with wire drawing holes. S2: Matrix pretreatment: The machined boron carbide whisker-reinforced silicon carbide ceramic matrix was placed in acetone solution and ultrasonically cleaned for 35 minutes to remove surface oil. Then it was placed in deionized water and ultrasonically cleaned for 25 minutes to remove residual acetone. After cleaning, it was dried for later use. The inner wall of the wire drawing hole of the boron carbide whisker-reinforced silicon carbide ceramic matrix was sandblasted using a sandblasting device. 120 mesh silicon carbide sand was selected as the sandblasting medium and the treatment pressure was set to 0.5 MPa. After treatment, the roughness Ra of the inner wall of the wire drawing hole was controlled at 2.0-2.5 μm. S3: Gradient transition layer preparation: According to the composition gradient requirements of the gradient transition layer from the side near the boron carbide whisker-reinforced silicon carbide ceramic matrix to the side near the modified composite polycrystalline working layer, four groups of titanium carbide-tungsten carbide-cobalt mixed powders were prepared respectively. The first group (close to the boron carbide whisker-reinforced silicon carbide ceramic matrix) of mixed powder consists of: 16 parts cobalt, 9 parts titanium carbide, and 75 parts tungsten carbide. The second group of mixed powders consists of: 13 parts cobalt, 12 parts titanium carbide, and 75 parts tungsten carbide. The third group of mixed powders consists of: 10 parts cobalt, 15 parts titanium carbide, and 75 parts tungsten carbide. The fourth group (near the modified composite polycrystalline working layer) of mixed powder consists of: 8 parts cobalt, 18 parts titanium carbide, and 74 parts tungsten carbide. Each group of mixed powders was placed in a three-dimensional mixer and mixed at 80 r / min for 2 hours to ensure uniformity of components. Plasma spraying equipment was used to spray layer by layer starting from the first group of mixed powders. The spraying power was set to 35 kW and the spraying temperature to 950 ℃. The thickness of a single coating layer was controlled to be 25 μm and the total thickness of the gradient transition layer was 100 μm. During the spraying process, the distance between the spray gun and the inner wall of the wire drawing hole was kept at 90 mm and the spraying angle was 90°. S4: Preparation of rare earth modified cobalt-nickel alloy binder: Weigh 8.5g of cobalt powder and 2.1g of nickel powder according to a cobalt to nickel ratio of 4:1. Add 0.2g of molybdenum powder (2% of the total mass of the rare earth modified cobalt-nickel alloy binder) and 0.1g of rare earth mixed powder (1% of the total mass of the rare earth modified cobalt-nickel alloy binder). The rare earth mixed powder is a mixture of cerium and lanthanum, with 0.05g of cerium powder and 0.05g of lanthanum powder, and the ratio of cerium to lanthanum is 1:1. Place the above raw materials in a vacuum melting furnace and melt at 1550℃ for 2.5h under an argon protective atmosphere. After melting, perform water quenching treatment. Place the water-quenched alloy block in a ball mill and ball mill it to a particle size of 6-10μm to obtain rare earth modified cobalt-nickel alloy binder powder. S5: Polycrystalline Material Preparation: Weigh out 70g of diamond particles, 12g of tungsten carbide-titanium carbide composite particles, and 18g of rare earth modified cobalt-nickel alloy binder according to the following proportions: The diamond particles are graded by coarse and fine particle size distribution, with 28g of fine particles (5-10μm) and 42g of coarse particles (20-40μm), accounting for 40% and 60% of the total diamond particles, respectively; the ratio of tungsten carbide to titanium carbide in the tungsten carbide-titanium carbide composite particles is 2:1. The mixture consists of 8g of tungsten carbide powder and 4g of titanium carbide powder. The above raw materials are added to a planetary ball mill, and 15.3g of ethanol (15% of the total mass of the mixture) is added as a dispersant. Agate balls are used as the grinding medium. The ball-to-material ratio is set to 8:1, the rotation speed is 300r / min, and the mixture is ball-milled for 4 hours. After the ball milling is completed, the mixture is placed in a vacuum drying oven and dried at 100℃ and 0.09MPa for 6 hours to obtain the polycrystalline material for the modified composite polycrystalline working layer. S6: Compression molding: The prepared polycrystalline material is uniformly filled into the wire drawing holes of the boron carbide whisker-reinforced silicon carbide ceramic matrix with a gradient transition layer, and the molding is carried out by cold isostatic pressing process, with the molding pressure set at 210MPa and the holding time at 10min. S7: Step-by-step sintering: The molded blank is placed in a high-pressure sintering furnace, first under a vacuum of 3×10⁻⁶. -3Low-temperature pre-firing was carried out under a vacuum environment of Pa, with the pre-firing temperature set at 700℃ and the holding time at 2h. After pre-firing, the vacuum environment was replaced three times with inert gas, and the pressure was maintained for 12min after each replacement. Then, the temperature was increased to 1500℃ at a heating rate of 8℃ / min, and a pressure of 7MPa was applied. The temperature was held for 3h, and argon gas was introduced for protection during the heating stage. After sintering, the furnace was cooled to room temperature to obtain a high-temperature resistant polycrystalline wire drawing mold.

[0025] Test Project Specific indicators Test Results High temperature resistance Appearance after heat preservation at 1200℃ No cracks Hardness variation rate of modified composite polycrystalline working layer 6% abrasion resistance Cumulative wire drawing length (to 0.1mm wear) 10000m Interface bonding strength Boron carbide whiskers enhance the shear strength of silicon carbide ceramic matrix and modified composite polycrystalline working layer 200MPa As can be seen from the table above, the high-temperature resistant polycrystalline wire drawing die prepared in Example 4 exhibits balanced performance. Regarding high-temperature resistance, no cracks were observed in either the boron carbide whisker-reinforced silicon carbide ceramic matrix or the modified composite polycrystalline working layer after holding at 1200℃. The hardness change rate of the modified composite polycrystalline working layer was 6%. The ratio of cerium to lanthanum in the rare earth mixed powder was 1:1, resulting in uniform grain refinement of the rare earth modified cobalt-nickel alloy binder. The addition of 2% molybdenum powder ensured the stability of the binder under high-temperature conditions. In terms of wear resistance, the cumulative wire drawing length reached 10,000 m, and the coarseness of the diamond particles was moderate. The high particle content (60%) results in good initial wear resistance of the modified composite polycrystalline working layer. The filling of 28g of fine particles ensures the basic density of the working layer. The addition of 12g of tungsten carbide-titanium carbide composite particles further enhances the wear resistance of the working layer. The interfacial bonding strength is 200MPa. The gradient transition layer design with four groups of components is reasonable, realizing the effective connection between the boron carbide whisker-reinforced silicon carbide ceramic matrix and the modified composite polycrystalline working layer. Although it is slightly lower than that of Example 2, it can still fully meet the actual use requirements of high-temperature polycrystalline wire drawing dies.

[0026] For example 1: Please see Figure 1 The present invention provides a comparative scheme: The difference from Example 2 is that the mold substrate is a pure silicon carbide ceramic substrate (without boron carbide whiskers), while the remaining steps and parameters are exactly the same as in Example 2. Test Project Specific indicators Test Results High temperature resistance Appearance after heat preservation at 1200℃ Microcracks in pure silicon carbide ceramic matrix Hardness variation rate of modified composite polycrystalline working layer 5% abrasion resistance Cumulative wire drawing length (to 0.1mm wear) 6000m Interface bonding strength Shear strength of pure silicon carbide ceramic matrix and modified composite polycrystalline working layer 120MPa Data shows that the mold prepared in Comparative Example 1 has obvious performance defects. In terms of high temperature resistance, microcracks appeared in the pure silicon carbide ceramic matrix after holding at 1200℃. Due to the lack of reinforcement from boron carbide whiskers, the pure silicon carbide ceramic matrix is ​​brittle and cannot withstand thermal stress under high temperature conditions, leading to crack initiation and propagation. As for the modified composite polycrystalline working layer, since the formula remained unchanged, the hardness change rate remained at 5%, and the wear resistance decreased significantly, with a cumulative wire drawing length of only 6000m. This was mainly because the microcracks generated in the pure silicon carbide ceramic matrix destroyed the overall structural stability of the mold, resulting in uneven stress on the modified composite polycrystalline working layer, which accelerated the wear process. The interfacial bonding strength was only 120MPa. The cracking of the matrix directly destroyed the foundation of the interfacial bonding, preventing the buffering effect of the gradient transition layer from being fully utilized, and further reducing the bonding strength between the matrix and the modified composite polycrystalline working layer.

[0027] For example 2: Please see Figure 1 The present invention provides a comparative scheme: The difference from Example 2 is that there is no gradient transition layer, and the modified composite polycrystalline working layer is directly prepared on the boron carbide whisker-reinforced silicon carbide ceramic matrix. The remaining steps and parameters are exactly the same as in Example 2. Test Project Specific indicators Test Results High temperature resistance Appearance after heat preservation at 1200℃ Debonding of the modified composite polycrystalline working layer from the boron carbide whisker-reinforced silicon carbide ceramic matrix Hardness variation rate of modified composite polycrystalline working layer 5% abrasion resistance Cumulative wire drawing length (to 0.1mm wear) 4000m Interface bonding strength Boron carbide whiskers enhance the shear strength of silicon carbide ceramic matrix and modified composite polycrystalline working layer 80MPa The core problem with the mold prepared in Comparative Example 2 lies in the interfacial bonding performance. In the high-temperature resistance test, the modified composite polycrystalline working layer and the boron carbide whisker-reinforced silicon carbide ceramic matrix directly delaminated. Due to the lack of a gradient transition layer, the thermal expansion coefficients of the boron carbide whisker-reinforced silicon carbide ceramic matrix (ceramic material) and the modified composite polycrystalline working layer (diamond-metal binder composite material) differ greatly. In the high-temperature environment, severe thermal stress is generated at the interface. When the stress exceeds the bonding limit between the two, delamination occurs. Since the formula of the modified composite polycrystalline working layer itself remains unchanged, the hardness change rate is still 5%, and the wear resistance is the worst, with a cumulative wire drawing length of only 4000m. After the modified composite polycrystalline working layer delaminates from the matrix, it cannot form an effective wear-resistant working surface and fails rapidly during the copper wire drawing process. The interfacial bonding strength is only 80MPa. Without a component gradient transition, the interface between the matrix and the modified composite polycrystalline working layer is only a simple physical adhesion with extremely weak bonding force, which cannot meet the usage requirements of the high-temperature polycrystalline wire drawing mold.

[0028] For example 3: Please see Figure 1 The present invention provides a comparative scheme: The difference from Example 2 is that the binder is a common cobalt-nickel alloy binder (molybdenum powder and rare earth mixed powder), while the other steps and parameters are exactly the same as in Example 2; Test Project Specific indicators Test Results High temperature resistance Appearance after heat preservation at 1200℃ No cracks Hardness variation rate of modified composite polycrystalline working layer 25% abrasion resistance Cumulative wire drawing length (to 0.1mm wear) 7000m Interface bonding strength Boron carbide whiskers enhance the shear strength of silicon carbide ceramic matrix and modified composite polycrystalline working layer 150MPa Data shows that the main defect of the mold prepared in Comparative Example 3 is the insufficient performance of the binder. Regarding high-temperature resistance, although neither the boron carbide whisker-reinforced silicon carbide ceramic matrix nor the modified composite polycrystalline working layer showed cracks, the hardness change rate of the modified composite polycrystalline working layer was as high as 25%. The ordinary cobalt-nickel alloy binder, lacking the grain-refining effect of rare earth elements, is prone to grain growth at high temperatures, and the absence of molybdenum to improve its high-temperature stability leads to severe softening of the binder at 1200℃. This, in turn, causes a significant decrease in the overall hardness of the modified composite polycrystalline working layer, resulting in poor wear resistance and cumulative tensile stress. With a wire length of only 7000m, the ordinary cobalt-nickel alloy binder, after softening, could not provide a stable supporting bond for the diamond particles and the tungsten carbide-titanium carbide composite particles, causing the particles to easily fall off during friction, accelerating the wear of the modified composite polycrystalline working layer. The interfacial bonding strength was 150MPa. After the ordinary cobalt-nickel alloy binder softened, its chemical bonding force with the gradient transition layer, diamond particles, and tungsten carbide-titanium carbide composite particles weakened. Although the gradient transition layer played a certain buffering role, the overall interfacial bonding strength was still significantly lower than that of Example 2.

[0029] For example 4: Please see Figure 1 The present invention provides a comparative scheme: The difference from Example 2 is that the amount of rare earth mixed powder added in the rare earth modified cobalt-nickel alloy binder is 0.3%, while the remaining steps and parameters are exactly the same as in Example 2.

[0030] Test Project Specific indicators Test Results High temperature resistance Appearance after heat preservation at 1200℃ No cracks working layer hardness change rate 18% abrasion resistance Cumulative wire drawing length (to 0.1mm wear) 8500m Interface bonding strength Shear strength 160MPa When the rare earth mixed powder content was reduced to 0.3%, the hardness change rate of the working layer soared to 18%, which was much higher than 5% in Example 2. Due to insufficient rare earth content, the cobalt-nickel alloy grains could not be sufficiently refined. The binder softened due to grain growth at high temperature, which weakened the support force on the diamond particles. The wear resistance decreased to 8500 μm as the particle bonding stability decreased, and the interfacial bonding strength decreased to 160 MPa due to the softening of the binder. This proves that the performance deteriorates significantly when the rare earth mixed powder content is less than 0.5%.

[0031] For example 5: Please see Figure 1 The present invention provides a comparative scheme: The difference from Example 2 is that the ratio of cerium to lanthanum in the rare earth mixed powder is 3:1 (exceeding the range of 1:1-2:1 in claim 1), while the remaining steps and parameters are exactly the same as in Example 2.

[0032] Test Project Specific indicators Test Results High temperature resistance Appearance after heat preservation at 1200℃ Local microcracks in the working layer working layer hardness change rate 15% abrasion resistance Cumulative wire drawing length (to 0.1mm wear) 9000m Interface bonding strength Shear strength 170MPa When the cerium to lanthanum ratio increased to 3:1, localized microcracks appeared in the working layer, and the hardness change rate rose to 15%. Due to the excessively high cerium content and insufficient lanthanum content, the rare earth elements were unevenly distributed in the binder, resulting in poor grain refinement in some areas and stress concentration at high temperatures, leading to microcracks. Although the wear resistance and interfacial bonding strength were better than those of Comparative Example 4, they were still far lower than those of Example 2, proving that exceeding the 2:1 upper limit of the cerium-lanthanum ratio would destroy the synergistic effect of the components, leading to performance degradation.

[0033] The technical solution uses boron carbide whisker-reinforced silicon carbide ceramic as the substrate. The three-dimensional network of whiskers supports and prevents cracking, solving the brittleness problem of traditional pure silicon carbide substrates. Compared to Comparative Example 1, which cracked after holding at 1200℃ without whiskers, Examples 1-4 showed no cracks. The working layer uses 5-10μm and 20-40μm diamond, each accounting for 40-60%, combined with tungsten carbide-titanium carbide composite particles (2:1-3:1) to form a reinforced synergistic structure, avoiding the performance limitations of single particles. Simultaneously, the titanium carbide-tungsten carbide-cobalt multiphase gradient transition layer matches the thermal expansion coefficient through component gradient changes. Comparative Example 2 directly peels off without a transition layer, while the interface strength of the examples all exceeds 180MPa. Rare earth elements (cerium-lanthanum 1:1-2:1) and molybdenum are added to the binder to solve the high-temperature softening problem of traditional cobalt-nickel alloys. The hardness change rate of Comparative Example 3 reached 25%, while the examples had the lowest rate of only 4%. Regarding high-temperature resistance, as demonstrated in Examples 1-4, this technical solution exhibits no cracking or peeling after high-temperature treatment, with a hardness change rate of 4%-8%, completely solving the high-temperature failure problem of traditional molds. In terms of wear resistance, the cumulative wire drawing length in the examples is 8000-12000m, with Example 2 reaching 12000m, a significant improvement over the highest value of 7000m in the comparative example. Due to particle size distribution and binder modification, the working layer is wear-resistant and less prone to particle shedding. The interfacial strength in all examples exceeds 180MPa, with Example 2 reaching 220MPa, a substantial improvement over the highest value of 150MPa in the comparative example, eliminating the risk of interlayer peeling. More importantly, the matrix's crack resistance, tight interface, and wear-resistant working layer create a synergistic effect, achieving a leap in overall performance. Therefore, this technical solution is a fundamental solution to the pain points of traditional molds. The brittleness of the matrix is ​​improved from the microstructure through whisker reinforcement, rather than simple density optimization; the performance of the working layer is balanced between density and wear resistance through particle size distribution and composite effect, avoiding the limitations of a single component; the interface problem is solved by adapting the composition gradient, rather than physical means such as surface roughening; the binder is improved by rare earth refinement and molybdenum reinforcement to enhance high temperature stability, rather than passively resisting it.

[0034] To further illustrate the beneficial technical effects of the high-temperature resistant polycrystalline wire drawing dies and their preparation methods in the various embodiments of the present invention, relevant performance tests were conducted on the high-temperature resistant polycrystalline wire drawing dies and their preparation methods in Examples 1-4 and Comparative Examples 1-5; the test methods are as follows: High temperature resistance: The mold was placed in a muffle furnace at 1200℃ for 2 hours. After cooling, the surface and internal cracks were observed. The hardness of the working layer before and after heat preservation was tested with a Vickers hardness tester, and the hardness change rate was calculated. Wear resistance: A φ2.0mm copper wire drawing test was conducted using a DL-200 wire drawing tester at a drawing speed of 5m / s. The cumulative wire drawing length of the die was recorded until the wear of the working layer reached 0.1mm. Interface bond strength: The interfacial shear strength between the matrix and the working layer was determined by shear test using a CMT5105 electronic universal testing machine at a loading rate of 0.5 mm / min.

[0035] The above descriptions are merely embodiments of the present invention, and common knowledge regarding specific technical solutions or characteristics is not elaborated upon here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the technical solutions of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A high temperature resistant polycrystalline wire drawing die, characterized in that, The mold base and the modified composite polycrystal working layer are combined. The mold base is a boron carbide whisker reinforced silicon carbide ceramic base, wherein the proportion of boron carbide whisker is 5-10 parts, and the proportion of silicon carbide ceramic powder is 90-95 parts. The modified composite polycrystal working layer is combined in the inner wall of the wire drawing hole of the mold base, and the modified composite polycrystal working layer is composed of the following components in parts: diamond particles 65-80 parts, tungsten carbide-titanium carbide composite particles 5-15 parts, and rare earth modified cobalt-nickel alloy binder 10-20 parts. The diamond particles are graded in size, wherein the fine particles with a particle size of 5-10 μm account for 40-60 parts of the total amount of diamond particles, and the coarse particles with a particle size of 20-40 μm account for 40-60 parts of the total amount of diamond particles. The proportion of tungsten carbide to titanium carbide in the tungsten carbide-titanium carbide composite particles is 2:1-3:

1.

2. The refractory polycrystalline wire drawing die of claim 1, wherein, The proportion of cobalt to nickel in the rare earth modified cobalt-nickel alloy binder is 3:1-5:1, and 1-3% of molybdenum powder and 0.5-1.5% of rare earth mixed powder are further added to the binder, the rare earth mixed powder is a mixture of cerium and lanthanum, and the proportion of cerium to lanthanum is 1:1-2:

1.

3. The refractory polycrystalline wire drawing die of claim 1, wherein, A gradient transition layer is arranged between the mold base and the modified composite polycrystal working layer, and the gradient transition layer is a titanium carbide-tungsten carbide-cobalt composite gradient layer, from the side close to the base to the side close to the polycrystal working layer, the proportion of cobalt is gradiently reduced from 15-20 parts to 5-10 parts, the proportion of titanium carbide is gradiently increased from 5-10 parts to 15-20 parts, and the proportion of tungsten carbide is gradiently reduced from 75-80 parts to 70-75 parts.

4. A method of producing a high-temperature-resistant polycrystal drawing die according to any one of claims 1 to 3, characterized by, The method comprises the following steps: S1: base preparation: the boron carbide whisker (length 10-50 μm, diameter 0.5-2 μm) is calcined at 1000-1100 ℃ for 2-3 h to remove surface impurities, the silicon carbide ceramic powder (particle size 1-5 μm) is dried at 800-900 ℃ for 4-6 h, and the boron carbide whisker 5-10 parts and the silicon carbide ceramic powder 90-95 parts are mixed in the proportion, 3-5% of polyvinyl alcohol binder and 10-15% of deionized water are added, the ball-to-material ratio is 4:1-6:1, the rotation speed is 150-200 r / min, and the mixture is mixed in a planetary ball mill for 1-2 h, then spray granulation (inlet air temperature 180-200 ℃, outlet air temperature 80-100 ℃) is adopted to prepare particles with a particle size of 50-100 μm, the granulated particles are filled into a mold, hot pressing is adopted, the temperature is 180-220 ℃, the pressure is 50-80 MPa, the pressure is maintained for 10-15 min, the base blank is obtained, the blank is heated to 2050-2200 ℃ under argon protection, the temperature is maintained for 3-4 h, the heating rate is 3-5 ℃ / min, the furnace is cooled to room temperature, and the boron carbide whisker reinforced silicon carbide ceramic base with a wire drawing hole is formed by machining. S2: matrix pretreatment: the boron carbide whisker reinforced silicon carbide ceramic matrix is sequentially cleaned by ultrasonic cleaning for 30-40 min in acetone and ultrasonic cleaning for 20-30 min in deionized water, and then the inner wall of the drawing hole is sand blasted, the sand blasting medium is 100-150 mesh silicon carbide sand, the treatment pressure is 0.4-0.6 MPa, and the roughness Ra of the inner wall after treatment is controlled to be 1.5-3.0 μm; S3: gradient transition layer preparation: according to the component gradient ratio of the gradient transition layer, according to the component gradient requirement of the gradient transition layer from the side close to the matrix to the side close to the polycrystalline working layer, 3-5 groups of titanium carbide-tungsten carbide-cobalt mixed powder are prepared, the components of each group of powder meet: the first group close to the matrix cobalt 15-20 parts, titanium carbide 5-10 parts, tungsten carbide 70-8 parts; the last group close to the polycrystalline working layer cobalt 5-10 parts, titanium carbide 15-20 parts, tungsten carbide 70-75 parts; the component content of the intermediate group changes linearly and continuously along the above direction; the plasma spraying process is adopted, and the spraying is started from the first group of powder, the spraying power is 30-40 kW, the spraying temperature is 900-1000℃, the single group coating thickness is 20-30 μm, and the total transition layer thickness is 60-150 μm; S4: preparation of rare earth modified binder: cobalt powder and nickel powder are weighed according to the part ratio of 3:1-5:1, 1-3% of molybdenum powder and 0.5-1.5% of rare earth mixed powder (cerium and lanthanum part ratio 1:1-2:1) are added, and then melted at 1500-1600℃ for 2-3h under argon protection, water quenching and ball milling to 5-10 μm particle size to obtain rare earth modified cobalt-nickel alloy binder; S5: preparation of polycrystalline material: diamond particles (5-10 μm fine particles and 20-40 μm coarse particles each accounting for 40-60%), tungsten carbide-titanium carbide composite particles (tungsten carbide and titanium carbide part ratio 2:1-3:1) and the binder prepared in S4 are weighed according to the part ratio, added into a planetary ball mill, ethanol is used as dispersant, the amount of dispersant is 12-18% of the total mass of the mixture, the ball-to-material ratio is 6:1-10:1, the rotation speed is 250-350 r / min, and the ball milling is carried out for 3-5h, and then vacuum drying at 90-110℃ for 5-7h to obtain the polycrystalline material; S6: mold forming: the polycrystalline material is uniformly filled into the drawing hole of the matrix with gradient transition layer, and cold isostatic pressing is used for forming, the pressure is 180-220 MPa, and the pressure holding time is 8-12 min; S7: step sintering: first sintering at a vacuum degree of ≤5x10 -3 low-temperature pre-sintering at a temperature of 650-750°C for 1.5-2.5h in a Pa environment; then heating at a rate of 6-10°C / min to 1450-1550°C, applying a pressure of 6-9MPa for 2.5-3.5h, and protecting by argon during the heating stage; and finally cooling to room temperature in the furnace to obtain the product.

5. The preparation method according to claim 4, characterized in that, In S3, the distance between the spray gun and the inner wall of the drawing hole is kept at 80-100 mm, and the spraying angle is 90°.

6. The preparation method according to claim 4, characterized in that, In S5, agate balls are used as grinding medium during ball milling, the ball mill is stopped every 30 min for 5 min to avoid overheating, and the vacuum degree of vacuum drying is ≥0.09 MPa.

7. The preparation method according to claim 4, characterized in that, In S7, after the low temperature presintering is completed, the vacuum environment is replaced by inert gas for 2-3 times, the pressure is kept for 10-15 min after each replacement, and then the temperature is raised for sintering.

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