A pcbn tool material and a method of making the same

Abstract

The application provides a PCBN cutter material and a preparation method thereof, and belongs to the technical field of superhard materials, and comprises the following steps: cBN powder is treated by boiling with a hydrochloric acid solution and a NaOH solution, cleaned, alcohol-washed and vacuum-dried to obtain pretreated cBN powder; carbon nanotubes are mixed with polyvinylpyrrolidone and anhydrous ethanol after acidification treatment to obtain a dispersion liquid; the pretreated cBN powder and a binder are added into the dispersion liquid and mixed and stirred, vacuum-dried, high-pressure sintered, cooled and pressure-released to obtain the PCBN cutter material. In the application, the carbon nanotubes are treated by nitric acid and polyvinylpyrrolidone and participate in mixing in the form of a dispersion liquid, the dispersion uniformity of the carbon nanotubes in the PCBN system is improved, and the fracture toughness and the anti-chipping property of the PCBN cutter material are improved.

Description

Technical Field

[0001] This invention relates to the field of superhard materials technology, specifically to a PCBN tool material and its preparation method. Background Technology

[0002] Polycrystalline cubic boron nitride (PCBN) tool materials possess high hardness, wear resistance, thermal stability, and chemical stability, meeting the machining requirements of high-speed cutting, dry cutting, and hard-state cutting. They are commonly used in high-end equipment manufacturing fields such as automotive manufacturing. With the expanding application of difficult-to-machine materials and the increasing demands for precision machining, PCBN tool materials not only need to possess high hardness and wear resistance but also good fracture toughness to reduce the risk of microcrack propagation, chipping, and abnormal failure during cutting.

[0003] Currently, PCBN tool materials are typically produced by high-temperature and high-pressure sintering of cBN powder and a binder. The binder promotes bonding between cBN particles, improving the density and forming stability of the sintered body. However, due to the high hardness and brittleness of cBN itself, the grain interfaces and bonding phase regions within the PCBN sintered body easily become pathways for crack initiation and propagation. This results in PCBN tool materials still exhibiting insufficient toughness and limited resistance to chipping under interrupted cutting, heavy-load cutting, or complex operating conditions.

[0004] Patent document CN107759227A discloses a method for preparing PCBN tool material using a catalytic method. This method involves mixing composite particles, cubic boron nitride micropowder, diamond micropowder, inorganic non-metallic whiskers, and a binder to obtain a mixture. Finally, the mixture is placed in a graphite mold and sintered under ultra-high pressure and high temperature to obtain the PCBN tool material. This method utilizes a catalytic method to directly convert some hexagonal boron nitride into cubic boron nitride, and combines this with diamond micropowder, inorganic non-metallic whiskers, and a binder to improve the fracture toughness and impact resistance of the PCBN tool material. However, directly incorporating inorganic non-metallic whiskers into the mixture can create locally rich agglomerates and weakly bonded regions within the PCBN tool material, thus limiting further improvements in fracture toughness and chipping resistance.

[0005] In summary, there is a need to provide a PCBN tool material and its preparation method to solve the problems existing in the prior art. Summary of the Invention

[0006] To address the problem in the prior art that reinforcing phases such as carbon nanotubes tend to agglomerate and disperse unevenly in PCBN tool materials, thereby affecting the fracture toughness and chipping resistance of PCBN tool materials, this invention provides a PCBN tool material and its preparation method.

[0007] To achieve the above objectives, a method for preparing PCBN tool material includes the following preparation steps: S1. Place cBN powder in hydrochloric acid solution, boil and wash with water, then place in NaOH solution, boil and wash with water, centrifuge, wash with water, wash with alcohol, and vacuum dry to obtain pretreated cBN powder. S2. Pour carbon nanotubes into nitric acid solution, disperse ultrasonically, heat and stir, filter, wash with water and alcohol to obtain acidified carbon nanotubes; mix polyvinylpyrrolidone and anhydrous ethanol, add acidified carbon nanotubes, disperse ultrasonically, heat and stir to obtain dispersion. S3. Add the pretreated cBN powder and binder to the dispersion and mix. After vacuum drying and heat treatment, a mixed powder is obtained. S4. The mixed powder is loaded into a mold, sintered under high pressure, cooled and depressurized to obtain PCBN tool material; The binder includes Al powder, Ti powder and Al2O3 powder.

[0008] This invention introduces polyvinylpyrrolidone (PVP) to modify carbon nanotubes in the PCBN tool material system, and incorporates the PVP-modified carbon nanotubes into the subsequent mixing process in the form of a dispersion (the solvent of the dispersion is anhydrous ethanol). This improves the problem of easy entanglement and secondary agglomeration of carbon nanotubes when they are directly added, allowing the carbon nanotubes to be more evenly distributed between the cBN powder and the binder, which helps to improve the fracture toughness and chipping resistance of the PCBN tool material.

[0009] This invention first acidifies carbon nanotubes with nitric acid, then modifies the surface of the acidified carbon nanotubes with polyvinylpyrrolidone (PVP). The PPVP-modified carbon nanotubes can form a relatively stable dispersion in anhydrous ethanol. Therefore, in the subsequent high-energy ball milling process, the carbon nanotubes are no longer added directly as dry material, but rather enter the mixing system along with the dispersion, which helps reduce secondary agglomeration of the carbon nanotubes. Through this treatment method, the carbon nanotubes can more uniformly enter the interstitial region between cBN powder and the binder, and remain as a dispersed reinforcing phase inside the PCBN tool material after high-temperature and high-pressure sintering. Due to the high aspect ratio and good mechanical stability of carbon nanotubes, they can form a slender reinforcing structure within the material. When the PCBN tool material is subjected to external loads during sintering cooling, subsequent processing, or cutting service, the carbon nanotubes distributed between the cBN particles can hinder crack propagation and consume crack propagation energy through pull-out and load transfer, reducing the possibility of rapid crack penetration into the material. As a result, a composite reinforcement structure composed of cBN main crystalline phase, binder and carbon nanotubes is formed inside the PCBN tool material, which helps to improve the fracture toughness of the PCBN tool material and its resistance to chipping during the cutting process.

[0010] Optionally, the binder may also include a Ti-Al composite.

[0011] Optionally, the Ti-Al composite is obtained by mixing Al powder and Ti powder, pressing them into a green body under a pressure of 60~70MPa, heat-treating it at 1050~1160℃ for 1~2h, cooling it to room temperature, lightly grinding and dispersing it, and passing it through a 100~300 mesh sieve; the thickness of the green body is 1~2mm.

[0012] This invention prepares a Ti-Al composite with in-situ Al2O3 whiskers formed on the surface by sintering Al and Ti powders. This composite is then used as a binder along with the remaining Al, Ti, and Al2O3 powders. The raw materials for this Ti-Al composite are derived from the existing binder materials (Al and Ti powders), eliminating the need for additional purchased whisker materials, thus reducing the introduction of impurities and maintaining the consistency of the binder system composition. Specifically, the preform, formed by pressing a mixture of Al and Ti powders, undergoes partial oxidation after heat treatment, forming Al2O3 whiskers. These whiskers are distributed between cBN particles along with the binder, creating fine bridging and crack-resistant structures in the binder phase and grain boundary regions. When the PCBN tool material is subjected to external loads during sintering, cooling, subsequent processing, or cutting service, the Al2O3 whiskers can hinder crack propagation, causing crack deflection, passivation, or dispersion, thereby consuming crack propagation energy and reducing the likelihood of rapid crack propagation along the binder phase or grain boundary regions. Meanwhile, Al2O3 whiskers, as a rigid ceramic reinforcing structure, can synergistically enhance carbon nanotubes, further improving the fracture toughness and chipping resistance of PCBN tool materials.

[0013] In this invention, Al powder and Ti powder are mixed and pressed into a green body under 60-70 MPa. This allows for a more stable contact state between the Al and Ti powders, which is beneficial for the subsequent Ti-Al reaction and the formation of surface whisker structures. Controlling the green body thickness within the range of 1-2 mm facilitates heat transfer and ensures more uniform reactions inside and outside the green body.

[0014] Optionally, in step S1, cBN powder is poured into a 10wt%~30wt% hydrochloric acid solution, boiled for 20~40 minutes, washed with distilled water, then placed in a 10wt%~30wt% NaOH solution and boiled for 20~40 minutes, washed with distilled water, centrifuged, washed with distilled water, then washed with anhydrous ethanol, and finally vacuum dried to obtain pretreated cBN powder.

[0015] In this invention, cBN powder is boiled in hydrochloric acid solution and NaOH solution, followed by water washing, alcohol washing and vacuum drying to remove impurities and residues from the surface of the cBN powder, thereby improving the cleanliness of the cBN powder surface and reducing the adverse effects of moisture and impurities on subsequent mixing and high-temperature and high-pressure sintering. This allows for more complete contact between the cBN powder and the binder, which helps to improve the structural uniformity of the PCBN tool material.

[0016] Optionally, in step S2, carbon nanotubes are poured into a 20wt%~30wt% nitric acid solution, ultrasonically dispersed for 20~40 min, stirred at 40~60℃ for 20~24 h, filtered and washed with distilled water until the filtrate is neutral, and then washed with anhydrous ethanol to obtain acidified carbon nanotubes; polyvinylpyrrolidone is added to anhydrous ethanol, stirred evenly, acidified carbon nanotubes are added, ultrasonically treated at 30~50kHz for 1~4 h, and stirred at 30~40℃ for 80~100 min to obtain a dispersion.

[0017] This invention first acidifies carbon nanotubes with nitric acid, then modifies the surface of the acidified carbon nanotubes with polyvinylpyrrolidone, enabling the treated carbon nanotubes to form a relatively stable dispersion in anhydrous ethanol. Thus, the carbon nanotubes can participate in subsequent mixing in the form of a dispersion, improving the dispersion uniformity among cBN powder, binder, and carbon nanotubes.

[0018] Optionally, in step S3, pretreated cBN powder, Al powder, Ti powder and Al2O3 powder are added to a dispersion and mixed using a high-energy ball mill. After stirring at a speed of 300~400 r / min for 24~30 h, the mixture is vacuum dried and heat-treated to obtain a mixed powder.

[0019] In this invention, pretreated cBN powder, Al powder, Ti powder, and Al2O3 powder are thoroughly mixed with a dispersion to reduce local enrichment or uneven mixing. Subsequently, the solvent and residual organic matter are removed by vacuum drying and heat treatment to obtain a uniformly composed mixed powder, which provides a foundation for the subsequent preparation of stable PCBN tool materials.

[0020] Optionally, in step S3, the vacuum drying temperature is 60~65℃ and the time is 24~26h.

[0021] Optionally, in step S3, the heat treatment temperature is 500~600℃ and the time is 2~3h.

[0022] Optionally, in step S4, the pressure of the high-pressure sintering is 5~6 GPa, the temperature is 1450~1550℃, and the time is 5~10 min.

[0023] Optionally, PCBN tool material can be brazed to WC alloy substrate to obtain PCBN tool.

[0024] The present invention also provides a PCBN tool material, which is prepared by the above-mentioned method for preparing PCBN tool material. The PCBN tool material comprises the following raw materials in parts by weight: 75-82 parts of cBN powder, 3.3-4.7 parts of Al powder, 2.2-3.1 parts of Ti powder, 11-15.7 parts of Al2O3 powder, 0.8-1.5 parts of carbon nanotubes, and 1.6-3 parts of polyvinylpyrrolidone.

[0025] The above-described technical solution of the present invention has at least the following beneficial effects: This invention modifies carbon nanotubes with polyvinylpyrrolidone (PVP) and incorporates it into subsequent mixing in the form of anhydrous ethanol dispersion. This prevents the carbon nanotubes from being added directly as dry material, but instead introduces them into the mixing system along with the anhydrous ethanol dispersion. This ensures that the carbon nanotubes maintain a continuous dispersion state from surface modification and dispersion to ball milling and mixing, thereby improving the problem of secondary agglomeration that easily occurs when carbon nanotubes are added directly.

[0026] Through the above treatment method, carbon nanotubes can more uniformly penetrate the interstitial region between cBN powder and the binder, and remain as a dispersed reinforcing phase inside the PCBN tool material after high-temperature and high-pressure sintering. This results in a composite reinforcing structure composed of the cBN main crystalline phase, the binder, and carbon nanotubes within the PCBN tool material. This composite reinforcing structure can hinder crack propagation under external loads, thereby improving the fracture toughness and chipping resistance of the PCBN tool material. Attached Figure Description

[0027] Figure 1 This is a scanning electron microscope image of the Ti-Al composite prepared in Example 1 of the present invention. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. The described embodiments are some embodiments of the present invention, and all other embodiments obtained by those skilled in the art based on the described embodiments of the present invention are within the scope of protection of the present invention.

[0029] Example 1 The raw materials in this embodiment include 82 parts cBN powder (size 4μm~6μm, purity 99.9%), 4.7 parts Al powder, 3.1 parts Ti powder, 15.7 parts Al2O3 powder, 1.5 parts carbon nanotubes, and 3 parts polyvinylpyrrolidone. The cBN powder was purchased from Zhengzhou Zhongnan Jiete Superhard Materials Co., Ltd., model CBNM-W; the Al powder, Ti powder, Al2O3 powder, carbon nanotubes, and polyvinylpyrrolidone were all commercially available raw materials.

[0030] 82 parts of cBN powder were placed in 600 parts of 10wt% hydrochloric acid solution, boiled for 40 minutes, washed with distilled water, then placed in 550 parts of 10wt% NaOH solution and boiled for 40 minutes, washed with distilled water, centrifuged, washed with distilled water, washed with anhydrous ethanol, and finally vacuum dried to obtain pretreated cBN powder.

[0031] 1.5 parts of carbon nanotubes were poured into 90 parts of 20wt% nitric acid solution, ultrasonically dispersed for 40 min, stirred at 60℃ for 20 h, filtered and washed with distilled water until the filtrate was neutral, and then washed with anhydrous ethanol to obtain acidified carbon nanotubes; 3 parts of polyvinylpyrrolidone were added to 200 parts of anhydrous ethanol, stirred evenly, acidified carbon nanotubes were added, ultrasonically treated at 50 kHz for 1 h, and stirred at 40℃ for 80 min to obtain a dispersion.

[0032] 2.4 parts Al powder and 1.2 parts Ti powder were mixed (the weight ratio of Al powder to Ti powder was 2:1) and pressed into a blank with a thickness of 1 mm under a pressure of 70 MPa. The blank was placed in a crucible and buried with a mixture of graphite powder / alumina powder. It was then placed in a box-type resistance furnace and heated to 1160℃ for 1 hour. After cooling to room temperature, it was lightly ground and passed through a 300-mesh sieve to obtain the Ti-Al composite.

[0033] Al₂O₃ powder, the remaining Al powder, the remaining Ti powder, and the Ti-Al composite were added to a dispersion along with pretreated cBN powder. The mixture was then stirred in a high-energy ball mill at 400 rpm for 24 hours. Following this, the mixture was dried under vacuum at 65°C for 24 hours, and then further dried at 600°C for 2 hours to obtain the mixed powder. Notably, no additional anhydrous ethanol was added during the mixing process in the high-energy ball mill.

[0034] The mixed powder was loaded into a synthesis mold to form a synthesis block, and then placed in a six-sided press for high-temperature and high-pressure sintering. The sintering pressure was 6 GPa, the sintering temperature was 1550℃, and the holding time was 5 min. After sintering, the temperature was lowered and the pressure was released. After cooling to room temperature, the sample was taken out and the surface was polished to obtain PCBN tool material.

[0035] Example 2 The raw materials in this embodiment include 78 parts cBN powder (size 4μm~6μm, purity 99.9%), 3.9 parts Al powder, 2.6 parts Ti powder, 13 parts Al2O3 powder, 1.2 parts carbon nanotubes, and 2.4 parts polyvinylpyrrolidone. The cBN powder was purchased from Zhengzhou Zhongnan Jiete Superhard Materials Co., Ltd., model CBNM-W; the Al powder, Ti powder, Al2O3 powder, carbon nanotubes, and polyvinylpyrrolidone were all commercially available raw materials.

[0036] 78 parts of cBN powder were placed in 580 parts of 20wt% hydrochloric acid solution, boiled for 30 minutes, and then washed with distilled water. The powder was then placed in 500 parts of 20wt% NaOH solution and boiled for 30 minutes, and washed with distilled water. After centrifugation, the powder was first washed with distilled water, then washed with anhydrous ethanol, and finally vacuum dried to obtain pretreated cBN powder.

[0037] 1.2 parts of carbon nanotubes were poured into 85 parts of 25wt% nitric acid solution, ultrasonically dispersed for 30 min, stirred at 50℃ for 22 h, filtered and washed with distilled water until the filtrate was neutral, and then washed with anhydrous ethanol to obtain acidified carbon nanotubes; 2.4 parts of polyvinylpyrrolidone were added to 200 parts of anhydrous ethanol, stirred evenly, acidified carbon nanotubes were added, ultrasonically treated at 40 kHz for 2 h, and stirred at 35℃ for 90 min to obtain a dispersion.

[0038] 1.5 parts Al powder and 0.75 parts Ti powder were mixed (the weight ratio of Al powder to Ti powder was 2:1) and pressed into a blank with a thickness of 1.5 mm under a pressure of 65 MPa. The blank was placed in a crucible and buried with a mixture of graphite powder / alumina powder. It was then placed in a box-type resistance furnace and heated to 1080℃ for 1.5 h for heat treatment. After cooling to room temperature, it was lightly ground and passed through a 200-mesh sieve to obtain the Ti-Al composite.

[0039] Al₂O₃ powder, the remaining Al powder, the remaining Ti powder, and the Ti-Al composite were added to a dispersion along with pretreated cBN powder. The mixture was then stirred in a high-energy ball mill at 300 rpm for 26 hours. Following this, the mixture was dried under vacuum at 63°C for 25 hours, and then further dried at 550°C for 2.5 hours to obtain the mixed powder. Notably, no additional anhydrous ethanol was added during the mixing process in the high-energy ball mill.

[0040] The mixed powder was filled into a synthesis mold to form a synthesis block, and then placed in a six-sided press for high-temperature and high-pressure sintering. The sintering pressure was 5.5 GPa, the sintering temperature was 1500℃, and the holding time was 7 min. After sintering, the temperature was lowered and the pressure was released. After cooling to room temperature, the sample was taken out and the surface was polished to obtain PCBN tool material.

[0041] Example 3 The raw materials in this embodiment include 75 parts cBN powder (size 4μm~6μm, purity 99.9%), 3.3 parts Al powder, 2.2 parts Ti powder, 11 parts Al2O3 powder, 0.8 parts carbon nanotubes, and 1.6 parts polyvinylpyrrolidone. The cBN powder was purchased from Zhengzhou Zhongnan Jiete Superhard Materials Co., Ltd., model CBNM-W; the Al powder, Ti powder, Al2O3 powder, carbon nanotubes, and polyvinylpyrrolidone were all commercially available raw materials.

[0042] 75 parts of cBN powder were placed in 450 parts of 30wt% hydrochloric acid solution, boiled for 20 minutes, washed with distilled water, then placed in 450 parts of 30wt% NaOH solution and boiled for 20 minutes, and washed with distilled water. After centrifugation, the powder was first washed with distilled water, then washed with anhydrous ethanol, and finally vacuum dried to obtain pretreated cBN powder.

[0043] 0.8 parts of carbon nanotubes were poured into 80 parts of 30wt% nitric acid solution, ultrasonically dispersed for 40 min, stirred at 40℃ for 24 h, filtered and washed with distilled water until the filtrate was neutral, and then washed with anhydrous ethanol to obtain acidified carbon nanotubes; 1.6 parts of polyvinylpyrrolidone were added to 200 parts of anhydrous ethanol, stirred evenly, acidified carbon nanotubes were added, ultrasonically treated at 30 kHz for 4 h, and stirred at 30℃ for 100 min to obtain a dispersion.

[0044] 1.2 parts Al powder and 0.6 parts Ti powder were mixed (the weight ratio of Al powder to Ti powder was 2:1) and pressed into a blank with a thickness of 2 mm under a pressure of 60 MPa. The blank was placed in a crucible and buried with a mixture of graphite powder / alumina powder. It was then placed in a box-type resistance furnace and heated to 1050℃ for 2 hours. After cooling to room temperature, it was lightly ground and passed through a 100-mesh sieve to obtain the Ti-Al composite.

[0045] Al₂O₃ powder, the remaining Al powder, the remaining Ti powder, and the Ti-Al composite were added to a dispersion along with pretreated cBN powder. The mixture was then stirred in a high-energy ball mill at 300 rpm for 30 hours. Following this, the mixture was dried under vacuum at 60°C for 26 hours, and then further dried at 500°C for 3 hours to obtain the mixed powder. Notably, no additional anhydrous ethanol was added during the mixing process in the high-energy ball mill.

[0046] The mixed powder was filled into a synthesis mold to form a synthesis block, and then placed in a six-sided press for high-temperature and high-pressure sintering. The sintering pressure was 5 GPa, the sintering temperature was 1450℃, and the holding time was 10 min. After sintering, the temperature was lowered and the pressure was released. After cooling to room temperature, the sample was taken out and the surface was polished to obtain PCBN tool material.

[0047] Example 4 The raw materials in this embodiment include 82 parts cBN powder (size 4μm~6μm, purity 99.9%), 4.7 parts Al powder, 3.1 parts Ti powder, 15.7 parts Al2O3 powder, 1.5 parts carbon nanotubes, and 3 parts polyvinylpyrrolidone. The cBN powder was purchased from Zhengzhou Zhongnan Jiete Superhard Materials Co., Ltd., model CBNM-W; the Al powder, Ti powder, Al2O3 powder, carbon nanotubes, and polyvinylpyrrolidone were all commercially available raw materials.

[0048] 82 parts of cBN powder were placed in 600 parts of 10wt% hydrochloric acid solution, boiled for 40 minutes, washed with distilled water, then placed in 550 parts of 10wt% NaOH solution and boiled for 40 minutes, washed with distilled water, centrifuged, washed with distilled water, washed with anhydrous ethanol, and finally vacuum dried to obtain pretreated cBN powder.

[0049] 1.5 parts of carbon nanotubes were poured into 90 parts of 20wt% nitric acid solution, ultrasonically dispersed for 40 min, stirred at 60℃ for 20 h, filtered and washed with distilled water until the filtrate was neutral, and then washed with anhydrous ethanol to obtain acidified carbon nanotubes; 3 parts of polyvinylpyrrolidone were added to 200 parts of anhydrous ethanol, stirred evenly, acidified carbon nanotubes were added, ultrasonically treated at 50 kHz for 1 h, and stirred at 40℃ for 80 min to obtain a dispersion.

[0050] Pretreated cBN powder, Al2O3 powder, Al powder, and Ti powder were added to a dispersion and mixed using a high-energy ball mill. After stirring at 400 rpm for 24 hours, the mixture was first dried at 65°C for 24 hours under vacuum, and then heated to 600°C for 2 hours to obtain a mixed powder. Notably, no additional anhydrous ethanol was added during the mixing process in the high-energy ball mill.

[0051] The mixed powder was loaded into a synthesis mold to form a synthesis block, and then placed in a six-sided press for high-temperature and high-pressure sintering. The sintering pressure was 6 GPa, the sintering temperature was 1550℃, and the holding time was 5 min. After sintering, the temperature was lowered and the pressure was released. After cooling to room temperature, the sample was taken out and the surface was polished to obtain PCBN tool material.

[0052] Example 5 The raw materials in this embodiment include 78 parts cBN powder (size 4μm~6μm, purity 99.9%), 3.9 parts Al powder, 2.6 parts Ti powder, 13 parts Al2O3 powder, 1.2 parts carbon nanotubes, and 2.4 parts polyvinylpyrrolidone. The cBN powder was purchased from Zhengzhou Zhongnan Jiete Superhard Materials Co., Ltd., model CBNM-W; the Al powder, Ti powder, Al2O3 powder, carbon nanotubes, and polyvinylpyrrolidone were all commercially available raw materials.

[0053] 78 parts of cBN powder were placed in 580 parts of 20wt% hydrochloric acid solution, boiled for 30 minutes, and then washed with distilled water. The powder was then placed in 500 parts of 20wt% NaOH solution and boiled for 30 minutes, and washed with distilled water. After centrifugation, the powder was first washed with distilled water, then washed with anhydrous ethanol, and finally vacuum dried to obtain pretreated cBN powder.

[0054] 1.2 parts of carbon nanotubes were poured into 85 parts of 25wt% nitric acid solution, ultrasonically dispersed for 30 min, stirred at 50℃ for 22 h, filtered and washed with distilled water until the filtrate was neutral, and then washed with anhydrous ethanol to obtain acidified carbon nanotubes; 2.4 parts of polyvinylpyrrolidone were added to 200 parts of anhydrous ethanol, stirred evenly, acidified carbon nanotubes were added, ultrasonically treated at 40 kHz for 2 h, and stirred at 35℃ for 90 min to obtain a dispersion.

[0055] Pretreated cBN powder, Al2O3 powder, Al powder, and Ti powder were added to a dispersion and mixed using a high-energy ball mill. After stirring at 300 rpm for 26 hours, the mixture was first dried at 63℃ for 25 hours under vacuum, and then heated to 550℃ for 2.5 hours to obtain a mixed powder. Notably, no additional anhydrous ethanol was added during the mixing process in the high-energy ball mill.

[0056] The mixed powder was filled into a synthesis mold to form a synthesis block, and then placed in a six-sided press for high-temperature and high-pressure sintering. The sintering pressure was 5.5 GPa, the sintering temperature was 1500℃, and the holding time was 7 min. After sintering, the temperature was lowered and the pressure was released. After cooling to room temperature, the sample was taken out and the surface was polished to obtain PCBN tool material.

[0057] Example 6 The raw materials in this embodiment include 75 parts cBN powder (size 4μm~6μm, purity 99.9%), 3.3 parts Al powder, 2.2 parts Ti powder, 11 parts Al2O3 powder, 0.8 parts carbon nanotubes, and 1.6 parts polyvinylpyrrolidone. The cBN powder was purchased from Zhengzhou Zhongnan Jiete Superhard Materials Co., Ltd., model CBNM-W; the Al powder, Ti powder, Al2O3 powder, carbon nanotubes, and polyvinylpyrrolidone were all commercially available raw materials.

[0058] 75 parts of cBN powder were placed in 450 parts of 30wt% hydrochloric acid solution, boiled for 20 minutes, washed with distilled water, then placed in 450 parts of 30wt% NaOH solution and boiled for 20 minutes, and washed with distilled water. After centrifugation, the powder was first washed with distilled water, then washed with anhydrous ethanol, and finally vacuum dried to obtain pretreated cBN powder.

[0059] 0.8 parts of carbon nanotubes were poured into 80 parts of 30wt% nitric acid solution, ultrasonically dispersed for 40 min, stirred at 40℃ for 24 h, filtered and washed with distilled water until the filtrate was neutral, and then washed with anhydrous ethanol to obtain acidified carbon nanotubes; 1.6 parts of polyvinylpyrrolidone were added to 200 parts of anhydrous ethanol, stirred evenly, acidified carbon nanotubes were added, ultrasonically treated at 30 kHz for 4 h, and stirred at 30℃ for 100 min to obtain a dispersion.

[0060] Pretreated cBN powder, Al2O3 powder, Al powder, and Ti powder were added to a dispersion and mixed using a high-energy ball mill. After stirring at 300 rpm for 30 hours, the mixture was first dried at 60°C for 26 hours under vacuum, and then heated to 500°C for 3 hours to obtain a mixed powder. Notably, no additional anhydrous ethanol was added during the mixing process in the high-energy ball mill.

[0061] The mixed powder was filled into a synthesis mold to form a synthesis block, and then placed in a six-sided press for high-temperature and high-pressure sintering. The sintering pressure was 5 GPa, the sintering temperature was 1450℃, and the holding time was 10 min. After sintering, the temperature was lowered and the pressure was released. After cooling to room temperature, the sample was taken out and the surface was polished to obtain PCBN tool material.

[0062] The present invention also includes comparative examples and related experiments.

[0063] Comparative Example 1 The only difference from Example 1 is that anhydrous ethanol is used instead of the dispersion, while the other components and preparation steps are completely the same, resulting in PCBN tool material.

[0064] Comparative Example 2 The only difference from Example 1 is that polyvinylpyrrolidone was not added; all other components and preparation steps were exactly the same, resulting in PCBN tool material.

[0065] Comparative Example 3 The only difference from Example 1 is that nitric acid was not used to treat the carbon nanotubes; the other components and preparation steps are completely the same, resulting in PCBN tool material.

[0066] Performance testing: The Vickers hardness of the PCBN tool materials in Examples 1-6 and Comparative Examples 1-3 was tested according to the standard GB / T 4340.1-2024. The test results are shown in Table 1.

[0067] The fracture toughness of the PCBN tool materials in Examples 1-6 and Comparative Examples 1-3 was tested according to the standard JB / T 12607-2016. The test results are shown in Table 1.

[0068] The wear ratio of the PCBN tool materials in Examples 1-6 and Comparative Examples 1-3 was tested according to the standard JB / T 3235-2023. The test results are shown in Table 1.

[0069] The bending strength of the PCBN tool materials in Examples 1-6 and Comparative Examples 1-3 was tested using the three-point bending method. The loading speed used in the three-point bending method was 0.5 mm / min. The test results are shown in Table 1.

[0070] Table 1

[0071] As shown in Table 1, the Vickers hardness of the PCBN tool materials in Examples 1-6 ranges from 4195 to 4392 Hv, and the fracture toughness ranges from 7.05 to 7.54 MPa·m. 1 / 2 Within the specified range, the wear ratio is distributed in the range of 7095~8012, and the flexural strength is distributed in the range of 672~723 MPa, indicating that the present invention has good process adaptability. Among these, compared to Examples 4~6, Examples 1~3 further employ a Ti-Al composite based on the dispersion. The Al2O3 whiskers on the surface of the Ti-Al composite can form fine bridging and crack-resistant structures in the binder phase and grain boundary regions. Figure 1 The image shown is a scanning electron microscope image of the Ti-Al composite prepared in Example 1 of this invention, which improves the material's resistance to crack propagation and enhances the wear resistance, fracture toughness, and chipping resistance of PCBN tool materials.

[0072] Based on the data in Table 1, it can be seen from Example 1 and Comparative Example 1 that Comparative Example 1 used anhydrous ethanol instead of dispersion liquid and did not add carbon nanotubes to the PCBN tool material. The resulting PCBN tool material had significantly reduced fracture toughness, wear ratio, and bending strength. This indicates that the addition of carbon nanotubes can improve the internal reinforcing structure of the PCBN tool material, enabling the material to better hinder crack propagation during stress and improve the material's wear resistance, fracture toughness, and chipping resistance. Compared to Example 1, the carbon nanotubes in Comparative Example 2 were not treated with polyvinylpyrrolidone, and the carbon nanotubes in Comparative Example 3 were not treated with nitric acid. The Vickers hardness, fracture toughness, wear ratio, and bending strength of the PCBN tool materials in Comparative Examples 2 and 3 all decreased. The carbon nanotubes treated with nitric acid and polyvinylpyrrolidone successively had a better dispersion effect in anhydrous ethanol, which is conducive to the full distribution of carbon nanotubes between cBN powder and binder, thereby improving the wear resistance, fracture toughness, and chipping resistance of the PCBN tool material.

[0073] The above are preferred embodiments of the present invention. Those skilled in the art can make several improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing PCBN tool material, characterized in that, The preparation steps include the following: S1. Place cBN powder in hydrochloric acid solution, boil and wash with water, then place in NaOH solution, boil and wash with water, centrifuge, wash with water, wash with alcohol, and vacuum dry to obtain pretreated cBN powder. S2. Pour carbon nanotubes into nitric acid solution, disperse ultrasonically, heat and stir, filter, wash with water and alcohol to obtain acidified carbon nanotubes; mix polyvinylpyrrolidone and anhydrous ethanol, add acidified carbon nanotubes, disperse ultrasonically, heat and stir to obtain dispersion. S3. Add the pretreated cBN powder and binder to the dispersion and mix. After vacuum drying and heat treatment, a mixed powder is obtained. S4. The mixed powder is loaded into a mold, sintered under high pressure, cooled and depressurized to obtain PCBN tool material; The binder includes Al powder, Ti powder and Al2O3 powder.

2. The method for preparing a PCBN tool material according to claim 1, characterized in that, The binder also includes a Ti-Al complex.

3. The method for preparing a PCBN tool material according to claim 2, characterized in that, The Ti-Al composite is obtained by mixing Al powder and Ti powder, pressing them into a green body under a pressure of 60~70MPa, heat-treating it at 1050~1160℃ for 1~2h, cooling it to room temperature, lightly grinding and dispersing it, and then passing it through a 100~300 mesh sieve; the thickness of the green body is 1~2mm.

4. The method for preparing a PCBN tool material according to claim 1, characterized in that, In step S1, cBN powder is poured into a 10wt%~30wt% hydrochloric acid solution, boiled for 20~40 minutes, washed with distilled water, then placed in a 10wt%~30wt% NaOH solution and boiled for 20~40 minutes, washed with distilled water, centrifuged, washed with distilled water, then washed with anhydrous ethanol, and finally vacuum dried to obtain pretreated cBN powder.

5. The method for preparing a PCBN tool material according to claim 1, characterized in that, In step S2, carbon nanotubes are poured into a 20wt%~30wt% nitric acid solution, ultrasonically dispersed for 20~40 min, stirred at 40~60℃ for 20~24 h, filtered and washed with distilled water until the filtrate is neutral, and then washed with anhydrous ethanol to obtain acidified carbon nanotubes. Polyvinylpyrrolidone was added to anhydrous ethanol and stirred until homogeneous. Acidified carbon nanotubes were then added, and the mixture was sonicated at 30-50 kHz for 1-4 h and stirred at 30-40 °C for 80-100 min to obtain a dispersion.

6. The method for preparing a PCBN tool material according to claim 1, characterized in that, In step S3, pretreated cBN powder, Al powder, Ti powder and Al2O3 powder are added to a dispersion and mixed using a high-energy ball mill. After stirring at a speed of 300~400 r / min for 24~30 h, the mixture is vacuum dried and heat-treated to obtain a mixed powder.

7. The method for preparing a PCBN tool material according to claim 6, characterized in that, In step S3, the vacuum drying temperature is 60~65℃ and the time is 24~26h.

8. The method for preparing a PCBN tool material according to claim 1, characterized in that, In step S3, the heat treatment temperature is 500~600℃ and the time is 2~3h.

9. The method for preparing a PCBN tool material according to claim 1, characterized in that, In step S4, the pressure of high-pressure sintering is 5~6 GPa, the temperature is 1450~1550℃, and the time is 5~10 min.

10. A PCBN tool material, prepared by the method for preparing a PCBN tool material according to any one of claims 1 to 9, characterized in that, The PCBN tool material comprises the following raw materials in parts by weight: 75-82 parts cBN powder, 3.3-4.7 parts Al powder, 2.2-3.1 parts Ti powder, 11-15.7 parts Al2O3 powder, 0.8-1.5 parts carbon nanotubes, and 1.6-3 parts polyvinylpyrrolidone.

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