PCBN cutting tool composite material and sintering preparation process thereof

Abstract

The application belongs to the technical field of PCBN cutter preparation, and particularly relates to a PCBN cutter composite material and a sintering preparation process thereof, which comprises the following steps: treating PS microspheres with hydrochloric acid dopamine, dispersing titanium carbide and titanium nitride in a mixed solution of anhydrous ethanol and a dispersing agent, adding a premixed solution and water for reaction, carrying out temperature reaction after treatment with a phenolic resin ethanol solution, and removing carbon with nitric acid solution to obtain hollow microspheres; uniformly mixing the hollow microspheres, cBN, aluminum-titanium alloy powder and a binder, drying, compression molding, degreasing, and then carrying out infiltration treatment and sintering treatment to obtain the PCBN cutter composite material. In the application, titanium nitride and titanium carbide are prepared into hollow microspheres, ceramic microparticle agglomeration is avoided, aluminum-titanium alloy powder is filled in the hollow microspheres after melting, a three-dimensional metal network interlocked with the hollow microspheres is formed, and the wear resistance and impact resistance of the PCBN cutter composite material are improved.

Description

Technical Field

[0001] This invention belongs to the field of PCBN tool manufacturing technology, and particularly relates to a PCBN tool composite material and its sintering preparation process. Background Technology

[0002] PCBN (polycrystalline cubic boron nitride) tool composites are key tool materials in high-end cutting processes such as high-speed dry cutting and interrupted milling, primarily used for finishing and semi-finishing gray and white cast iron, powder metallurgy parts, and other materials. In existing technologies, PCBN tool composites are produced by mixing cBN (cubic boron nitride single crystal) micro-powder with a metal binder and then sintering under high temperature and pressure. While these composites exhibit good toughness and impact resistance in practical applications, their wear resistance is relatively poor.

[0003] Chinese patent application CN121245027A discloses a polycrystalline cubic boron nitride coated cutting tool, comprising a PCBN substrate and a first coating formed on the PCBN substrate. The PCBN substrate has at least a polycrystalline layer, which includes cubic boron nitride, a first binder, and a second binder. The first binder is a mixture selected from one or more of titanium carbide, titanium nitride, niobium nitride, silicon nitride, alumina, yttrium oxide, and silicon. The second binder is selected from one or more of aluminum, titanium, cobalt, nickel, tungsten, niobium, tantalum, and zirconium. Although the simultaneous addition of a metallic binder and a ceramic binder can theoretically improve the wear resistance of the PCBN cutting tool composite material through the ceramic phase, the physical properties of the ceramic phase and the metallic phase are quite different. During mixing and sintering, the ceramic phase is prone to agglomeration, resulting in significant differences in wear resistance and impact resistance in different regions of the PCBN cutting tool. This reduces the wear resistance and impact resistance of the PCBN cutting tool composite material, leading to poor tool stability. Summary of the Invention

[0004] This invention provides a PCBN tool composite material and its sintering preparation process. Titanium nitride and titanium carbide are prepared into hollow microspheres. The pre-made hollow microspheres serve as independent composite units, effectively preventing the agglomeration of titanium nitride and titanium carbide. After melting, aluminum-titanium alloy powder permeates and connects the hollow microspheres, forming a continuous three-dimensional metal network interlocked with the hollow microspheres. This network absorbs impact force through deformation while inhibiting the propagation of interfacial cracks, thereby improving the wear resistance and impact resistance of the PCBN tool composite material.

[0005] To solve the above problems, the present invention provides the following technical solution: A sintering preparation process for a PCBN tool composite material includes the following steps: S1. Dopamine hydrochloride was used to coat PS microspheres. Titanium carbide, titanium nitride, and the coated PS microspheres were added to a mixture of anhydrous ethanol and a dispersant. A premix and deionized water were added and reacted. After washing, the mixture was impregnated with a phenolic resin ethanol solution and then heated in an inert atmosphere. After cooling, the mixture was dispersed in a nitric acid solution and reacted. After washing and drying, hollow microspheres were obtained. The premix was prepared by adding isopropyl titanate and acetylacetone to anhydrous ethanol and reacting. S2. Hollow microspheres, cBN, aluminum-titanium alloy powder and binder are mixed evenly, dried, pressed into shape, degreased and then infiltrated by heating and pressurizing to obtain preforms. S3. The preform is sintered by heating and pressurizing to obtain PCBN tool composite material.

[0006] This invention prepares a PCBN tool composite material by mixing, drying, and pressing cBN, aluminum-titanium alloy powder, hollow microspheres, and a binder. During the heating and pressurization process, the molten metal formed by the partial melting of the aluminum-titanium alloy powder permeates the hollow microspheres. Subsequently, sintering is performed under high temperature and high pressure conditions. In the preparation of the hollow microspheres, titanium nitride, titanium carbide, and dopamine hydrochloride-coated PS microspheres are connected through a titanium-oxygen network via alcoholysis and hydrolysis of isopropyl titanate. Phenolic resin adheres to the titanium-oxygen network through hydrogen bonding and other interactions, and is carbonized in an inert atmosphere to form amorphous carbon. With further temperature increases, the amorphous carbon reacts with nitrogen in the titanium-oxygen network and the titanium nitride lattice to form a titanium-carbon-nitrogen solid solution, connecting adjacent titanium carbide and titanium nitride to form a continuous ceramic framework. High-temperature calcination removes the PS microspheres, and nitric acid solution is used to dissolve and remove unreacted amorphous carbon, resulting in hollow microspheres with a double-layered through-pore structure.

[0007] During the infiltration process, aluminum-titanium alloy powder forms a titanium-containing molten metal at high temperature. This molten metal has good wettability to hollow microspheres and can penetrate into their interior along the pores. During high-pressure sintering, the molten metal penetrating into the hollow microspheres can support the sphere walls, alleviate the pressure difference between the inside and outside of the hollow microspheres, and maintain the structural integrity of the hollow microspheres. After penetrating the hollow microspheres, the molten metal connects adjacent hollow microspheres, forming a continuous three-dimensional metal network structure that is mechanically interlocked with the hollow microspheres. Under sintering cooling and cutting conditions, the strain energy at the interface between the hollow microspheres and the metal can be transferred to the entire three-dimensional metal network. By extending the propagation path of interfacial cracks, the formation of macro-microcracks is prevented. When subjected to impact, the continuous three-dimensional metal network structure facilitates the diffusion of impact force, ensuring that the PCBN tool composite material has good impact resistance. Since the hollow microspheres are prefabricated independent composite units, the positions of titanium nitride and titanium carbide in the hollow microspheres are fixed and will not agglomerate due to surface energy. The adjacent hollow microspheres have discrete point contact, which reduces the range of van der Waals forces between hollow microspheres, inhibits the agglomeration of hollow microspheres, and improves the overall wear resistance of the PCBN tool composite material.

[0008] Furthermore, in step S1, PS microspheres with a particle size of 4-5 μm and PS microspheres with a particle size of 250-300 nm are coated, respectively. The particle size of titanium nitride is 100-200 nm, and the particle size of titanium carbide is 100-200 nm.

[0009] Using two different sizes of PS microspheres as pore-forming templates, a dual-level pore structure was introduced into the hollow microspheres: after the large-diameter PS microspheres (4-5μm) were removed in situ, a micron-sized internal main cavity was formed, providing a low-resistance filling space for the molten metal and improving the filling speed of the molten metal; after the small-diameter PS microspheres (250-300nm) were removed in situ, nano-sized through pores were left on the hollow microspheres, connecting the main cavity with the external space, promoting the full filling of the internal pores of the hollow microspheres by the molten metal under pressure, increasing the filling amount of molten metal in the hollow microspheres, which can significantly improve the fracture resistance of the hollow microspheres under high-pressure sintering conditions, and at the same time increase the contact area between the metal three-dimensional network structure and the hollow microspheres, which is conducive to the rapid transfer and dissipation of strain energy at the interface between the hollow microspheres and the metal, and significantly improves the impact resistance of the PCBN tool composite material.

[0010] Furthermore, the PS microspheres are coated in the following manner: PS microspheres are added to and dispersed in a 0.1-0.2wt% PVP-K30 aqueous solution, ammonia is added to adjust and maintain the pH value at 8.5-8.8, dopamine hydrochloride is added and reacted for 5-6 hours, filtered, washed with deionized water and anhydrous ethanol, and then dispersed in anhydrous ethanol at 0-5℃.

[0011] Under pH conditions of 8.5-8.8, dopamine hydrochloride is oxidized and adsorbed onto the surface of PS microspheres through hydrophobic interactions. Then, polymerization continues, forming a polydopamine coating layer on the outside of the PS microspheres. The polydopamine layer contains catechol hydroxyl and amino functional groups, which can serve as active sites for the subsequent adsorption of isopropyl titanate hydrolysis products and the formation of titanium oxide networks.

[0012] Further, in step S1, the premixed solution is added and reacted for 3-4 hours. Deionized water is added under continuous stirring. The pH is adjusted and maintained at 8-8.5 using ammonia water, and the reaction continues for 4-5 hours. After washing with anhydrous ethanol, the mixture is added to a 5-7 wt% phenolic resin ethanol solution for impregnation treatment for 45-55 minutes. After filtration, the mixture is heated to 100-110℃ under argon protection and dried for 3-4 hours. The temperature is then raised to 650-660℃ and kept at that temperature for 2-3 hours. The temperature is then raised to 1400-1450℃ and kept at that temperature for 1.5-2 hours. After cooling, the mixture is added to a 20-23 wt% nitric acid solution and heated to 60-70℃ for 2-3 hours. After washing with deionized water, the mixture is placed in an environment of 110-120℃ and dried for 5-6 hours. After cooling, hollow microspheres are obtained.

[0013] In the premixed solution, isopropyl titanate undergoes alcoholysis with anhydrous ethanol. The alcoholysis products are enriched on PS microspheres through coordination with catechol in the polydopamine membrane, and on the surfaces of titanium nitride and titanium carbide through coordination with titanium hydroxyl groups. With the addition of ethanol solution, the alcoholysis products are continuously hydrolyzed under the action of water. The titanium hydroxyl groups of the hydrolysate undergo condensation reactions, connecting the PS microspheres, titanium carbide, and titanium nitride through a titanium-oxygen network to form a microsphere precursor. At this time, the microsphere precursor is in an anhydrous ethanol swollen state. Phenolic resin can penetrate into the microsphere precursor through capillary action and through hydrogen bonding. By combining the phenolic resin with a titanium oxide network, followed by drying and dehydration at 100-110℃ and heat treatment at 650-660℃, the phenolic resin is carbonized to form amorphous carbon, further densifying the titanium oxide network. At 1400-1450℃, the amorphous carbon reacts with nitrogen in the titanium oxide network and titanium nitride lattice to form a titanium carbon nitride solid solution, connecting adjacent titanium carbide and titanium nitride to form a robust ceramic framework. PS microspheres decompose in situ at high temperature, forming pores. Unreacted amorphous carbon is decomposed and removed by oxidation with concentrated nitric acid solution, while the ceramic framework is preserved due to its stable chemical properties, resulting in hollow microspheres with a permeable porous structure. By controlling the concentration of the phenolic resin ethanol solution and the soaking time, the amount of amorphous carbon formed is controlled, improving the utilization rate of amorphous carbon, avoiding the reduction of mechanical strength of the hollow microspheres due to nitric acid washing, and preventing residual amorphous carbon from affecting the mechanical properties of the PCBN tool composite material.

[0014] Furthermore, the premixed solution is prepared by adding isopropyl titanate and acetylacetone to anhydrous ethanol and reacting for 15-20 minutes to obtain the premixed solution.

[0015] Furthermore, in step S1, before adding titanium nitride and titanium carbide to the mixture of anhydrous ethanol and dispersant, titanium carbide and titanium nitride are dispersed in a 20-25 wt% hydrogen peroxide aqueous solution and reacted for 10-15 min. After washing with deionized water and anhydrous ethanol, they are added to the mixture of anhydrous ethanol and dispersant PVP-K30.

[0016] Oxidation treatment with hydrogen peroxide aqueous solution increases the density of titanium hydroxyl groups on the surface of titanium nitride and titanium carbide, and also increases the density of the titanium oxygen network on the surface of titanium carbide and titanium nitride, which is beneficial to improving the mechanical strength of hollow microspheres.

[0017] Further, in step S2, under nitrogen protection, cBN, aluminum-titanium alloy powder, 0.5-0.7wt% PVB ethanol solution of binder, and hollow microspheres are mixed and dried in an environment of 40-50℃ and 15-20kPa for 4-6 hours. The mixture is then placed in a mold, subjected to a pressure of 200-250MPa and held for 15-20 minutes, and placed in an argon atmosphere for degreasing at 500-550℃ and 100-130Pa for 1-1.5 hours. After infiltration treatment at 35-40MPa and 820-830℃ for 50-55 minutes, the preform is obtained after holding the pressure and cooling.

[0018] PVB is decomposed and removed under conditions of 500-550℃ and 100-130Pa. Under conditions of 35-40MPa and 820-830℃, aluminum-titanium alloy powder is melted to obtain titanium-containing molten metal. The introduction of titanium increases the affinity between the molten metal and the hollow microspheres, which is conducive to its penetration and filling into the pores of the hollow microspheres under pressure, thereby improving the ability of the hollow microspheres to resist pressure during subsequent high-pressure sintering. Cooling is carried out under pressure to provide external constraint force for the hollow microspheres and inhibit the hollow microspheres from cracking under stress during metal shrinkage.

[0019] Furthermore, in step S3, the pressure is increased to 0.8-1 GPa, the temperature is increased to 850-900℃, and sintering is performed for 10-12 minutes. Then, the pressure is increased to 5.5-6 GPa, the temperature is increased to 1450-1460℃, and sintering is performed for 10-15 minutes. After holding the pressure and cooling to 650-670℃, the pressure is released and further cooled to obtain the PCBN tool composite material.

[0020] A PCBN tool composite material, prepared by the sintering process of the above-mentioned PCBN tool composite material, comprises the following raw materials in parts by weight: 70-75 parts cBN, 40-44 parts aluminum-titanium alloy powder, and 15-20 parts hollow microspheres; wherein the hollow microspheres comprise the following raw materials in parts by weight: 10.5-11.9 parts PS microspheres, 25-30 parts titanium nitride, 10-15 parts titanium carbide, 13-16 parts isopropyl titanate, 9-11 parts deionized water, 300-310 parts 5-7wt% phenolic resin ethanol solution, and dopamine hydrochloride; wherein the mass ratio of dopamine hydrochloride to PS microspheres is 1:(15-17).

[0021] Furthermore, the PS microspheres comprise 7.5-8.5 parts by weight of PS microspheres with a particle size of 4-5 μm and 3-3.4 parts by weight of PS microspheres with a particle size of 250-300 nm.

[0022] The present invention has the following beneficial effects: This invention prepares PCBN tool composite material by mixing cBN, aluminum-titanium alloy powder, hollow microspheres and binder, drying and pressing them into shape, followed by infiltration treatment and sintering treatment. Hollow microspheres use PS microspheres as pore-forming templates and titanium carbide and titanium nitride connected by a titanium-nitrogen-carbon solid solution as a ceramic skeleton. During the infiltration process, the titanium-containing molten metal formed by melting aluminum-titanium alloy powder infiltrates into the hollow microspheres through the pores created by the in-situ removal of PS microspheres, providing support for the hollow microspheres and preventing them from breaking during high-pressure sintering. The molten metal can connect adjacent hollow microspheres to form a continuous three-dimensional metal network structure that is mechanically interlocked with the hollow microspheres. The three-dimensional metal network can not only absorb impact force through its deformation capacity, but also prevent the formation of macro-microcracks by extending the propagation path of interface cracks, thereby improving the impact resistance of PCBN tool composite materials. At the same time, the hollow microspheres are independent composite units, and the positions of titanium nitride and titanium carbide are fixed, which improves the dispersion of titanium nitride and titanium carbide. The high modulus of titanium nitride and titanium carbide enhances the overall wear resistance of PCBN tool composite materials. Attached Figure Description

[0023] Figure 1 This is a graph showing the mercury intrusion-mercury removal capillary pressure curve of the hollow microspheres prepared in Example 6; Figure 2 The X-ray diffraction pattern is shown for the hollow microspheres prepared in Example 6. Detailed Implementation

[0024] Preparation Example 1 Add 8.5g of PS (polystyrene) microspheres with a particle size of 5μm to 120g of 0.1wt% PVP-K30 (polyvinylpyrrolidone, model K30) aqueous solution, sonicate at 50W for 15min, adjust and maintain the pH value of 8.5 by adding 5wt% ammonia water dropwise, add 0.5g of dopamine hydrochloride, stir at 300rpm for 5h, filter, wash 4 times alternately with deionized water and anhydrous ethanol, add to 60g of 0℃ anhydrous ethanol, stir at 500rpm for 10min, and restore to room temperature to obtain a modified large microsphere suspension; add 3.4g of PS microspheres with a particle size of 250nm to 50g of 0.1wt% PVP-K30 aqueous solution, sonicate at 100W for 30min, adjust and maintain the pH value of 8.5 by adding 5wt% ammonia water dropwise, add 0.2g of dopamine hydrochloride, stir at 300rpm for 5h, filter, wash 4 times alternately with deionized water and anhydrous ethanol, add to 60g of 0℃ anhydrous ethanol, stir at 500rpm for 5h, filter, wash 4 times alternately with deionized water and anhydrous ethanol, add to 60g of 0℃ anhydrous ethanol, stir at 500rpm for 30min, and restore to room temperature to obtain a modified large microsphere suspension; The modified microsphere suspension was obtained by stirring at 500 rpm for 10 min in anhydrous ethanol at 0℃ and then allowing it to return to room temperature.

[0025] Add 14g of isopropyl titanate and 2.5g of acetylacetone to 50g of anhydrous ethanol, stir at 300rpm for 15min to obtain a premix; add 25g of titanium nitride with a particle size of 200nm and 10g of titanium carbide with a particle size of 200nm to 300g of 20wt% hydrogen peroxide aqueous solution, sonicate at 100W for 15min, filter, wash three times with deionized water, and wash three times with anhydrous ethanol to complete the pretreatment of titanium nitride and titanium carbide; add 1g of... PVP-K30 was stirred at 300 rpm for 15 min, followed by the addition of pretreated titanium nitride and titanium carbide. The mixture was stirred at 1000 rpm for 10 min, then the modified microsphere suspension was added. The mixture was stirred at 1000 rpm for 15 min, followed by the addition of the modified large microsphere suspension. The mixture was stirred at 1000 rpm for 10 min, and then the premixed solution was slowly added while stirring at 800 rpm. After the addition was complete, the mixture was stirred at 300 rpm for 3 h, and then 9 g of deionized water was slowly added while stirring at 1000 rpm. After the addition was complete, 5 wt% ammonia was added dropwise to adjust and maintain the pH at 8. The mixture was stirred at 400 rpm for 4 h, filtered, and washed twice with anhydrous ethanol to obtain the microsphere precursor.

[0026] Preparation Example 2 Add 7.5g of PS microspheres with a particle size of 4.5μm to 120g of 0.15wt% PVP-K30 aqueous solution, sonicate at 50W for 15min, adjust and maintain the pH value of 8.8 by adding 5wt% ammonia dropwise, add 0.5g of dopamine hydrochloride, stir at 300rpm for 5.5h, filter, wash 4 times alternately with deionized water and anhydrous ethanol, add to 60g of anhydrous ethanol at 2℃, stir at 500rpm for 10min, and return to room temperature to obtain a modified large microsphere suspension; add 3g of PS microspheres with a particle size of 300nm to 50g of 0.15wt% PVP-K30 aqueous solution, sonicate at 100W for 30min, adjust and maintain the pH value of 8.6 by adding 5wt% ammonia dropwise, add 0.2g of dopamine hydrochloride, stir at 300rpm for 6h, filter, wash 4 times alternately with deionized water and anhydrous ethanol, add to 60g of anhydrous ethanol at 2℃ for 10min, and return to room temperature to obtain a modified large microsphere suspension; The modified microsphere suspension was obtained by stirring at 500 rpm for 10 min in anhydrous ethanol at 5℃ and then allowing it to return to room temperature.

[0027] Add 13g of isopropyl titanate and 2.5g of acetylacetone to 50g of anhydrous ethanol, stir at 300rpm for 18min to obtain a premix; add 30g of titanium nitride with a particle size of 150nm and 12g of titanium carbide with a particle size of 100nm to 300g of 25wt% hydrogen peroxide aqueous solution, sonicate at 100W for 10min, filter, wash three times with deionized water, and wash three times with anhydrous ethanol to complete the pretreatment of titanium nitride and titanium carbide; add 1g of... PVP-K30 was stirred at 300 rpm for 15 min, then pretreated titanium nitride and titanium carbide were added, and the mixture was stirred at 1000 rpm for 10 min. The modified microsphere suspension was then added, and the mixture was stirred at 1000 rpm for 15 min. The modified large microsphere suspension was then added, and the mixture was stirred at 1000 rpm for 10 min. The premixed solution was then slowly added while stirring at 800 rpm. After the addition was complete, the mixture was stirred at 300 rpm for 4 h. 10 g of deionized water was then slowly added while stirring at 1000 rpm. After the addition was complete, 5 wt% ammonia was added dropwise to adjust and maintain the pH at 8.2. The mixture was stirred at 400 rpm for 5 h, filtered, and washed twice with anhydrous ethanol to obtain the microsphere precursor.

[0028] Preparation Example 3 Add 8g of PS microspheres with a particle size of 4μm to 120g of 0.2wt% PVP-K30 aqueous solution, sonicate at 50W for 15min, adjust and maintain the pH value of 8.6 by adding 5wt% ammonia dropwise, add 0.5g of dopamine hydrochloride, stir at 300rpm for 6h, filter, wash 4 times alternately with deionized water and anhydrous ethanol, add to 60g of anhydrous ethanol at 5℃, stir at 500rpm for 10min, and return to room temperature to obtain a modified large microsphere suspension; add 3.2g of PS microspheres with a particle size of 280nm to 50g of 0.2wt% PVP-K30 aqueous solution, sonicate at 100W for 30min, adjust and maintain the pH value of 8.8 by adding 5wt% ammonia dropwise, add 0.2g of dopamine hydrochloride, stir at 300rpm for 6h, filter, wash 4 times alternately with deionized water and anhydrous ethanol, add to 60g of anhydrous ethanol at 5℃, stir at 500rpm for 10min, and return to room temperature to obtain a modified large microsphere suspension; The modified microsphere suspension was obtained by stirring at 500 rpm for 10 min in anhydrous ethanol at 3℃ and then allowing it to return to room temperature.

[0029] Add 16g of isopropyl titanate and 2.5g of acetylacetone to 50g of anhydrous ethanol, stir at 300rpm for 20min to obtain a premix; add 28g of titanium nitride with a particle size of 100nm and 15g of titanium carbide with a particle size of 150nm to 300g of 23wt% hydrogen peroxide aqueous solution, sonicate at 100W for 12min, filter, wash three times with deionized water, and wash three times with anhydrous ethanol to complete the pretreatment of titanium nitride and titanium carbide; add 1g of... PVP-K30 was stirred at 300 rpm for 15 min, then pretreated titanium nitride and titanium carbide were added, and the mixture was stirred at 1000 rpm for 10 min. The modified microsphere suspension was then added, and the mixture was stirred at 1000 rpm for 15 min. The modified large microsphere suspension was then added, and the mixture was stirred at 1000 rpm for 10 min. The premixed solution was then slowly added while stirring at 800 rpm. After the addition was complete, the mixture was stirred at 300 rpm for 3.5 h. 11 g of deionized water was then slowly added while stirring at 1000 rpm. After the addition was complete, 5 wt% ammonia was added dropwise to adjust and maintain the pH at 8.5. The mixture was stirred at 400 rpm for 4.5 h, filtered, and washed twice with anhydrous ethanol to obtain the microsphere precursor.

[0030] Example 1 The microsphere precursor was immersed in an ethanol solution of 310 g of 5 wt% phenolic resin (polymerized from phenol and formaldehyde, with a number-average degree of polymerization of 4), stirred at 600 rpm for 45 min, filtered, drained until no liquid dripped, placed in a tube furnace, heated to 100 °C for 3 h under argon protection, heated to 650 °C for 2 h, heated to 1400 °C for 2 h, cooled to room temperature, added to 300 g of 20 wt% nitric acid solution, heated to 60 °C, stirred at 500 rpm for 2 h, filtered, washed with deionized water until the washings were neutral, placed in an environment of 110 °C for 5 h, cooled to room temperature, and hollow microspheres were obtained.

[0031] Under nitrogen protection, 70g of cBN with a particle size of 2μm and 40g of aluminum-titanium alloy powder with a particle size of 3μm (the mass ratio of aluminum to titanium is 3:1) were added to a mixer. 40g of 0.5wt% PVB (polyvinyl butyral, with an average molar amount of 40000g / mol) ethanol solution was added, and the mixture was stirred at 50rpm for 2h. 15g of hollow microspheres were added, and the mixture was stirred at 50rpm for 30min. The mixture was then dried at 40℃ and 15kPa for 4h. The mixture was placed in a mold, and a pressure of 200MPa was applied and held for 20min. The mixture was then placed in a tube furnace, and under argon protection, the temperature was adjusted to 500℃ and the pressure to 100Pa. The mixture was held for degreasing for 1h. The mixture was then placed in a hot press furnace, and the pressure was increased to 35MPa and the temperature was increased to 820℃. The mixture was held for infiltration treatment for 50min and then cooled to room temperature while maintaining a pressure of 35MPa to obtain the preform.

[0032] The preforms were placed into a six-sided press, the mold was closed, the pressure was slowly increased to 0.8 GPa, and the temperature was increased to 900℃. The temperature was held for sintering for 12 min, the pressure was slowly increased to 5.5 GPa, and the temperature was increased to 1450℃. The temperature was held for sintering for 10 min, the pressure was maintained at 5.5 GPa, and the temperature was cooled to 650℃. The pressure was slowly released to atmospheric pressure and cooled to room temperature to obtain the PCBN tool composite material.

[0033] The microsphere precursor used in this embodiment was prepared by preparation method 1.

[0034] Example 2 The microsphere precursor was immersed in an ethanol solution of 310 g of 5 wt% phenolic resin (polymerized from phenol and formaldehyde, with a number-average degree of polymerization of 4), stirred at 600 rpm for 45 min, filtered, drained until no liquid dripped, placed in a tube furnace, heated to 100 °C for 3 h under argon protection, heated to 650 °C for 2 h, heated to 1400 °C for 2 h, cooled to room temperature, added to 300 g of 20 wt% nitric acid solution, heated to 60 °C, stirred at 500 rpm for 2 h, filtered, washed with deionized water until the washings were neutral, placed in an environment of 110 °C for 5 h, cooled to room temperature, and hollow microspheres were obtained.

[0035] Under nitrogen protection, 75g of cBN with a particle size of 2μm and 43g of aluminum-titanium alloy powder with a particle size of 3μm (the mass ratio of aluminum to titanium is 3:1) were added to a mixer. 40g of 0.5wt% PVB (average molar amount of 40000g / mol) ethanol solution was added, and the mixture was stirred at 50rpm for 2h. 18g of hollow microspheres were added, and the mixture was stirred at 50rpm for 30min. The mixture was then dried at 45℃ and 18kPa for 6h. The mixture was placed in a mold, and a pressure of 250MPa was applied and held for 15min. The mixture was then placed in a tube furnace, and under argon protection, the temperature was adjusted to 550℃ and the pressure to 130Pa. The mixture was held for degreasing for 1.5h. The mixture was then placed in a hot press furnace, and the pressure was increased to 35MPa and the temperature was increased to 820℃. The mixture was held for infiltration treatment for 50min and then cooled to room temperature while maintaining a pressure of 35MPa to obtain the preform.

[0036] The preforms were placed into a six-sided press, the mold was closed, the pressure was slowly increased to 0.9 GPa, and the temperature was increased to 880℃. The temperature was held for sintering for 10 min, the pressure was slowly increased to 5.8 GPa, and the temperature was increased to 1455℃. The temperature was held for sintering for 15 min, the pressure was maintained at 5.8 GPa, and the temperature was cooled to 660℃. The pressure was slowly released to normal pressure and cooled to room temperature to obtain the PCBN tool composite material.

[0037] The microsphere precursor used in this embodiment was prepared by preparation method 1.

[0038] Example 3 The microsphere precursor was immersed in an ethanol solution of 300 g of 6 wt% phenolic resin (polymerized from phenol and formaldehyde, with a number-average degree of polymerization of 4), stirred at 600 rpm for 55 min, filtered, drained until no liquid dripped, placed in a tube furnace, heated to 110 °C for 3.5 h under argon protection, heated to 655 °C for 3 h, heated to 1450 °C for 1.8 h, cooled to room temperature, added to 300 g of 22 wt% nitric acid solution, heated to 65 °C, stirred at 500 rpm for 3 h, filtered, washed with deionized water until the washings were neutral, placed in an environment of 120 °C for 5.5 h, cooled to room temperature, and hollow microspheres were obtained.

[0039] Under nitrogen protection, 73g of cBN with a particle size of 2μm and 44g of aluminum-titanium alloy powder with a particle size of 3μm (the mass ratio of aluminum to titanium is 3:1) were added to a mixer. 40g of 0.6wt% PVB (average molar amount of 40000g / mol) ethanol solution was added, and the mixture was stirred at 50rpm for 2h. 20g of hollow microspheres were added, and the mixture was stirred at 50rpm for 30min. The mixture was then dried at 50℃ and 20kPa for 5h. The mixture was placed in a mold, and a pressure of 230MPa was applied and held for 18min. The mixture was then placed in a tube furnace, and under argon protection, the temperature was adjusted to 520℃ and the pressure to 120Pa. The mixture was held for degreasing for 1.2h. The mixture was then placed in a hot press furnace, and the pressure was increased to 40MPa and the temperature was increased to 825℃. The mixture was held for infiltration treatment for 55min and then cooled to room temperature while maintaining a pressure of 40MPa to obtain the preform.

[0040] The preforms were placed into a six-sided press, the mold was closed, the pressure was slowly increased to 1 GPa, and the temperature was increased to 850℃. The temperature was held for sintering for 11 min, the pressure was slowly increased to 6 GPa, and the temperature was increased to 1460℃. The temperature was held for sintering for 12 min, the pressure was maintained at 6 GPa, and the temperature was cooled to 670℃. The pressure was slowly released to normal pressure and cooled to room temperature to obtain the PCBN tool composite material.

[0041] The microsphere precursor used in this embodiment was prepared by preparation two.

[0042] Example 4 The microsphere precursor was immersed in an ethanol solution of 300 g of 6 wt% phenolic resin (polymerized from phenol and formaldehyde, with a number-average degree of polymerization of 4), stirred at 600 rpm for 55 min, filtered, drained until no liquid dripped, placed in a tube furnace, heated to 110 °C for 3.5 h under argon protection, heated to 655 °C for 3 h, heated to 1450 °C for 1.8 h, cooled to room temperature, added to 300 g of 22 wt% nitric acid solution, heated to 65 °C, stirred at 500 rpm for 3 h, filtered, washed with deionized water until the washings were neutral, placed in an environment of 120 °C for 5.5 h, cooled to room temperature, and hollow microspheres were obtained.

[0043] Under nitrogen protection, 75g of cBN with a particle size of 2μm and 40g of aluminum-titanium alloy powder with a particle size of 3μm (the mass ratio of aluminum to titanium is 3:1) were added to a mixer. 40g of 0.5wt% PVB (average molar amount of 40000g / mol) ethanol solution was added, and the mixture was stirred at 50rpm for 2h. 17g of hollow microspheres were added, and the mixture was stirred at 50rpm for 30min. The mixture was then dried at 40℃ and 15kPa for 4h. The mixture was placed in a mold, and a pressure of 200MPa was applied and held for 20min. The mixture was then placed in a tube furnace, and under argon protection, the temperature was adjusted to 500℃ and the pressure to 100Pa. The mixture was held for degreasing for 1h. The mixture was then placed in a hot press furnace, and the pressure was increased to 40MPa and the temperature was increased to 825℃. The mixture was held for infiltration treatment for 55min and then cooled to room temperature while maintaining a pressure of 40MPa to obtain the preform.

[0044] The preforms were placed into a six-sided press, the mold was closed, the pressure was slowly increased to 0.8 GPa, and the temperature was increased to 900℃. The temperature was held for sintering for 12 min, the pressure was slowly increased to 5.5 GPa, and the temperature was increased to 1450℃. The temperature was held for sintering for 10 min, the pressure was maintained at 5.5 GPa, and the temperature was cooled to 650℃. The pressure was slowly released to atmospheric pressure and cooled to room temperature to obtain the PCBN tool composite material.

[0045] The microsphere precursor used in this embodiment was prepared by preparation two.

[0046] Example 5 The microsphere precursor was immersed in an ethanol solution of 305 g of 7 wt% phenolic resin (polymerized from phenol and formaldehyde, with a number-average degree of polymerization of 4), stirred at 600 rpm for 50 min, filtered, drained until no liquid dripped, placed in a tube furnace, heated to 105 °C for 4 h under argon protection, heated to 660 °C for 2.5 h, heated to 1440 °C for 1.5 h, cooled to room temperature, added to 300 g of 23 wt% nitric acid solution, heated to 70 °C, stirred at 500 rpm for 2.5 h, filtered, washed with deionized water until the washings were neutral, dried at 115 °C for 6 h, and cooled to room temperature to obtain hollow microspheres.

[0047] Under nitrogen protection, 73g of cBN with a particle size of 2μm and 44g of aluminum-titanium alloy powder with a particle size of 3μm (the mass ratio of aluminum to titanium is 3:1) were added to a mixer. 40g of 0.7wt% PVB (average molar amount of 40000g / mol) ethanol solution was added, and the mixture was stirred at 50rpm for 2h. 19g of hollow microspheres were added, and the mixture was stirred at 50rpm for 30min. The mixture was then dried at 45℃ and 18kPa for 6h. The mixture was placed in a mold, and a pressure of 250MPa was applied and held for 15min. The mixture was then placed in a tube furnace, and under argon protection, the temperature was adjusted to 550℃ and the pressure to 130Pa. The mixture was held for degreasing for 1.5h. The mixture was then placed in a hot press furnace, and the pressure was increased to 38MPa and the temperature was increased to 830℃. The mixture was held for infiltration treatment for 53min and then cooled to room temperature while maintaining a pressure of 38MPa to obtain the preform.

[0048] The preforms were placed into a six-sided press, the mold was closed, the pressure was slowly increased to 0.9 GPa, and the temperature was increased to 880℃. The temperature was held for sintering for 10 min, the pressure was slowly increased to 5.8 GPa, and the temperature was increased to 1455℃. The temperature was held for sintering for 15 min, the pressure was maintained at 5.8 GPa, and the temperature was cooled to 660℃. The pressure was slowly released to normal pressure and cooled to room temperature to obtain the PCBN tool composite material.

[0049] The microsphere precursor used in this embodiment was prepared by preparation method 3.

[0050] Example 6 The microsphere precursor was immersed in an ethanol solution of 305 g of 7 wt% phenolic resin (polymerized from phenol and formaldehyde, with a number-average degree of polymerization of 4), stirred at 600 rpm for 50 min, filtered, drained until no liquid dripped, placed in a tube furnace, heated to 105 °C for 4 h under argon protection, heated to 660 °C for 2.5 h, heated to 1440 °C for 1.5 h, cooled to room temperature, added to 300 g of 23 wt% nitric acid solution, heated to 70 °C, stirred at 500 rpm for 2.5 h, filtered, washed with deionized water until the washings were neutral, dried at 115 °C for 6 h, and cooled to room temperature to obtain hollow microspheres.

[0051] Under nitrogen protection, 72g of cBN with a particle size of 2μm and 42g of aluminum-titanium alloy powder with a particle size of 3μm (the mass ratio of aluminum to titanium is 3:1) were added to a mixer. 40g of 0.6wt% PVB (average molar amount of 40000g / mol) ethanol solution was added, and the mixture was stirred at 50rpm for 2h. 20g of hollow microspheres were added, and the mixture was stirred at 50rpm for 30min. The mixture was then dried at 50℃ and 20kPa for 5h. The mixture was placed in a mold, and a pressure of 230MPa was applied and held for 18min. The mixture was then placed in a tube furnace, and under argon protection, the temperature was adjusted to 520℃ and the pressure to 120Pa. The mixture was held for degreasing for 1.2h. The mixture was then placed in a hot press furnace, and the pressure was increased to 38MPa and the temperature was increased to 830℃. The mixture was held for infiltration treatment for 53min and then cooled to room temperature while maintaining a pressure of 38MPa to obtain the preform.

[0052] The preforms were placed into a six-sided press, the mold was closed, the pressure was slowly increased to 1 GPa, and the temperature was increased to 850℃. The temperature was held for sintering for 11 min, the pressure was slowly increased to 6 GPa, and the temperature was increased to 1460℃. The temperature was held for sintering for 12 min, the pressure was maintained at 6 GPa, and the temperature was cooled to 670℃. The pressure was slowly released to normal pressure and cooled to room temperature to obtain the PCBN tool composite material.

[0053] The microsphere precursor used in this embodiment was prepared by preparation method 3.

[0054] The present invention also includes comparative examples and related experiments.

[0055] Comparative Example 1 The difference between this comparative example and Example 6 is that the PS microspheres with a particle size of 4 μm are replaced with PS microspheres with a particle size of 280 nm of the same mass. The remaining operation steps and reaction conditions are the same as in Example 6, and PCBN tool composite material is obtained.

[0056] Comparative Example 2 The difference between this comparative example and Example 6 is that the PS microspheres with a particle size of 280 nm are replaced with PS microspheres with a particle size of 4 μm of the same mass. The remaining operation steps and reaction conditions are the same as in Example 6, and PCBN tool composite material is obtained.

[0057] Comparative Example 3 The difference between this comparative example and Example 6 is that the premixed solution was prepared by mixing anhydrous ethanol and acetylacetone. The remaining operation steps and reaction conditions were the same as in Example 6, resulting in PCBN tool composite material.

[0058] Comparative Example 4 The difference between this comparative example and Example 6 is that the microsphere precursor was not soaked in phenolic resin ethanol solution. The remaining operation steps and reaction conditions are the same as in Example 6, and PCBN tool composite material is obtained.

[0059] Comparative Example 5 The difference between this comparative example and Example 6 is that the infiltration treatment was not carried out at 38 MPa and 830°C. The remaining operation steps and reaction conditions are the same as in Example 6, and PCBN tool composite material is obtained.

[0060] Performance test The impact resistance of the PCBN tool composite material specimens prepared in each embodiment and comparative example was tested using a drop hammer impact testing machine. The sintered PCBN tool composite material was fabricated into cuboid specimens with dimensions of 3mm × 4mm × 40mm and a surface roughness Ra ≤ 0.4μm. The hammer mass was set to 2kg. The critical drop height required for complete specimen fracture was determined through preliminary testing. The impact energy (J) absorbed when the specimen fractured was recorded. The impact toughness value (J / cm²) was calculated using the following formula. 2 ):

[0061] The cross-sectional area of ​​the sample is 0.12 cm². 2 The wear ratio of the PCBN tool composite material samples prepared in each embodiment and comparative example was tested using a wear ratio testing machine. The grinding wheel in the wear ratio testing machine was a corundum grinding wheel (hardness F100), the linear speed was set to 20 m / s, the loading pressure on the sample was 5 N, and after a cumulative grinding distance of 1000 m, the wear ratio was calculated according to the following formula: The results are shown in Table 1.

[0062] Table 1

[0063] As shown in Table 1, the impact toughness of the CBN tool composite material prepared in Example 6 is higher than that of Comparative Examples 1 and 2. This indicates that using PS microspheres of different particle sizes is beneficial for constructing hollow microspheres with a through-hole bilevel pore structure. The molten metal can fill the pore structure to maintain the integrity of the hollow microspheres during high-pressure sintering, improving the continuity of the three-dimensional metal network. When the sample is subjected to impact, the stress at the interface between the hollow microspheres and the metal can be rapidly dissipated, improving the impact resistance of the sample. Figure 1 As shown, the mercury intrusion curve has a steep rising section, and the mercury removal curve has a significant hysteresis loop, indicating that there are interconnected bilevel pores in the hollow microspheres.

[0064] The impact toughness of the PCBN tool composite material prepared in Example 6 is higher than that of Comparative Examples 3 and 4, while its wear ratio is lower. This indicates that the treatment with isopropyl titanate and phenolic resin ethanol solution allows titanium nitride and titanium carbide to be linked through a titanium carbonitride solid solution, forming a stable ceramic skeleton structure. This inhibits the agglomeration of titanium nitride and titanium carbide, thereby improving the impact toughness and impact resistance of the PCBN tool composite material. Figure 2 As shown, the baseline rises and forms a bulge between 2θ and 36.1° and 36.5°, which proves the formation of titanium carbon nitride solid solution.

[0065] The impact toughness value of the PCBN tool composite material prepared in Example 6 is higher than that in Comparative Example 5, indicating that through infiltration treatment, molten metal can be filled into hollow microspheres before high-pressure sintering. The hollow microspheres can remain intact during high-pressure sintering, improving the continuity of the three-dimensional metal network. When the PCBN tool composite material is subjected to impact, it is beneficial to the rapid dissipation of stress at the interface between the hollow microspheres and the metal, thereby improving the impact resistance of the PCBN tool composite material.

Claims

1. A sintering preparation process for PCBN tool composite materials, characterized in that, Includes the following steps: S1. Dopamine hydrochloride is used to coat PS microspheres. Titanium carbide, titanium nitride, and the coated PS microspheres are added to a mixture of anhydrous ethanol and a dispersant. A premix and deionized water are added and reacted. After washing, the mixture is impregnated with a phenolic resin ethanol solution and then heated in an inert atmosphere. After cooling, it is dispersed in a nitric acid solution and reacted. After washing and drying, hollow microspheres are obtained. The premix is ​​prepared by adding isopropyl titanate and acetylacetone to anhydrous ethanol and reacting. S2. Under nitrogen protection, cBN, aluminum-titanium alloy powder, and 0.5-0.7 wt% binder are added. PVB ethanol solution and hollow microspheres are mixed and dried in an environment of 40-50℃ and 15-20kPa for 4-6 hours. The mixture is then placed in a mold, and a pressure of 200-250MPa is applied and held for 15-20 minutes. The mixture is then placed in an argon atmosphere and degreased at 500-550℃ and 100-130Pa for 1-1.5 hours. It is then infiltrated at 35-40MPa and 820-830℃ for 50-55 minutes. After holding the pressure and cooling, a preform is obtained. S3: The pressure is increased to 0.8-1GPa and the temperature is increased to 850-900℃. The mixture is sintered for 10-12 minutes. The pressure is increased to 5.5-6GPa and the temperature is increased to 1450-1460℃. The mixture is sintered for 10-15 minutes. After holding the pressure and cooling to 650-670℃, the pressure is released and the mixture is further cooled to obtain PCBN tool composite material. The tool composite material comprises the following raw materials in parts by weight: 70-75 parts cBN, 40-44 parts aluminum-titanium alloy powder, and 15-20 parts hollow microspheres, wherein the aluminum-titanium alloy powder contains aluminum and titanium in a mass ratio of 3:1; the hollow microspheres comprise the following raw materials in parts by weight: 10.5-11.9 parts PS microspheres, 25-30 parts titanium nitride, 10-15 parts titanium carbide, 13-16 parts isopropyl titanate, 9-11 parts deionized water, and 300-310 parts of 5-7wt% phenolic resin ethanol solution; the mass ratio of dopamine hydrochloride to PS microspheres is 1:(15-17); the PS microspheres comprise 7.5-8.5 parts by weight of PS microspheres with a particle size of 4-5 μm and 3-3.4 parts by weight of PS microspheres with a particle size of 250-300 nm.

2. The sintering preparation process of a PCBN tool composite material according to claim 1, characterized in that, In step S1, PS microspheres with a particle size of 4-5 μm and PS microspheres with a particle size of 250-300 nm are coated, respectively. The particle size of titanium nitride is 100-200 nm, and the particle size of titanium carbide is 100-200 nm.

3. The sintering preparation process of a PCBN tool composite material according to claim 2, characterized in that, The PS microspheres were coated by adding PS microspheres to a 0.1-0.2wt% PVP-K30 aqueous solution and dispersing them. Ammonia was added to adjust and maintain the pH value at 8.5-8.

8. Dopamine hydrochloride was added and reacted for 5-6 hours. The mixture was filtered, washed with deionized water and anhydrous ethanol, and then dispersed in anhydrous ethanol at 0-5℃.

4. The sintering preparation process of a PCBN tool composite material according to claim 3, characterized in that, In step S1, the premixed solution is added and reacted for 3-4 hours. Deionized water is added under continuous stirring. The pH is adjusted and maintained at 8-8.5 using ammonia water, and the reaction continues for 4-5 hours. After washing with anhydrous ethanol, the mixture is immersed in a 5-7 wt% phenolic resin ethanol solution for 45-55 minutes. After filtration, the mixture is heated to 100-110℃ under argon protection and dried for 3-4 hours. The temperature is then raised to 650-660℃ and kept at that temperature for 2-3 hours. The temperature is then raised to 1400-1450℃ and kept at that temperature for 1.5-2 hours. After cooling, the mixture is added to a 20-23 wt% nitric acid solution and heated to 60-70℃ for 2-3 hours. After washing with deionized water, the mixture is dried at 110-120℃ for 5-6 hours. After cooling, hollow microspheres are obtained.

5. The sintering preparation process of a PCBN tool composite material according to claim 4, characterized in that, The premixed solution is prepared by adding isopropyl titanate and acetylacetone to anhydrous ethanol and reacting for 15-20 minutes to obtain the premixed solution.

6. The sintering preparation process of a PCBN tool composite material according to claim 1, characterized in that, In step S1, before adding titanium nitride and titanium carbide to the mixture of anhydrous ethanol and dispersant, titanium carbide and titanium nitride are dispersed in a 20-25wt% hydrogen peroxide aqueous solution and reacted for 10-15 minutes. After washing with deionized water and anhydrous ethanol, they are added to the mixture of anhydrous ethanol and dispersant PVP-K30.

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