Carbon nanotube reinforced tungsten carbide titanium metal ceramic material as well as preparation method and application thereof

Abstract

The invention discloses a carbon nano tube reinforced tungsten carbide titanium metal ceramic material as well as a preparation method and application thereof, and belongs to the field of metal ceramic materials. According to the invention, a spark plasma coupling high-frequency induction sintering method is adopted, CNTs are uniformly dispersed in a material matrix through a method of dispersing CNTs through dry ball milling again, and the uniformly dispersed CNTs improve the discharge environment, reduce the sintering current and reduce the energy consumption under the spark plasma coupling high-frequency induction effect in the sintering process. The high-compactness, high-strength and high-wear-resistance (W, Ti) C-based metal ceramic material is prepared at the sintering temperature of 1350 DEG C by utilizing the ultrahigh conductive complementary effect of the (W, Ti) C metal ceramic material and the CNTs.

Description

Technical Field

[0001] The present invention belongs to the field of metal ceramic materials, and in particular relates to a carbon nanotube reinforced tungsten carbide titanium metal ceramic material and a preparation method and application thereof. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance understanding of the overall background of the invention and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to those skilled in the art.

[0003] In the field of mechanical manufacturing, high-quality cutting tools are particularly important due to the need for cutting operations. Ceramic materials offer the advantages of high hardness and heat resistance, but their relatively low strength and toughness are the main reasons limiting their widespread application. Among metal-ceramic composite materials, (W,Ti)C-based cermet tools offer unparalleled advantages over other tool materials in high-speed machining. They combine the high strength of cemented carbide tools with a higher hardness, making them ideal for the production of high-performance cutting tools.

[0004] Current research indicates that there are numerous attempts to develop (W,Ti)C-based cermets. Existing technologies include spark plasma sintering (SPS) at 1500°C, self-propagating combustion synthesis (SHS) at 1600°C, and pressureless sintering at 1450°C. These methods utilize significant Joule heat to achieve material densification, resulting in high energy consumption and limited mechanical properties. Summary of the Invention

[0005] To address the shortcomings of the prior art, the present invention provides a carbon nanotube-reinforced tungsten carbide titanium cermet material, its preparation method, and its application. The present invention utilizes a spark plasma-coupled high-frequency induction sintering method, and further disperses the CNTs in the material matrix through dry ball milling. During the sintering process, the uniformly dispersed CNTs improve the discharge environment, reduce the sintering current, and minimize energy consumption under the action of spark plasma-coupled high-frequency induction. Leveraging the complementary ultrahigh electrical conductivity of the (W,Ti)C cermet and CNTs, a highly densified, high-strength, and highly wear-resistant (W,Ti)C-based cermet material was prepared at a sintering temperature of 1350°C.

[0006] In order to achieve the above object, the technical solution of the present invention is: In a first aspect, the present invention provides a carbon nanotube reinforced tungsten titanium carbide cermet material (CNTs-(W,Ti)C), comprising a matrix, a metal binder phase, and a reinforcement phase, wherein the matrix is ​​(W,Ti)C, the reinforcement phase is carbon nanotubes (CNTs), and the metal binder phase is Ni, Mo, and Co; The mass percentage of each component is: (W, Ti) C 84.5-85%, Ni 3-4%, Mo 6-7%, Co 4.5-5.5%, CNTs 0-0.5%, and the sum of the mass of each component is 100%.

[0007] The present invention uses (W, Ti) C ceramic as the matrix, adds Ni, Mo, and Co as the metal phase, and CNTs as the reinforcement phase. It is made by discharge plasma coupling high-frequency induction sintering. By utilizing the good conductivity of carbon nanotubes, the discharge environment is improved and the material densification sintering is completed.

[0008] In a second aspect, the present invention provides a method for preparing the above-mentioned carbon nanotube-reinforced tungsten carbide titanium metal ceramic material, comprising the following steps: (W, Ti) C powder, Ni powder, Mo powder, and Co powder are mixed according to a mass ratio and dispersed in a polyethylene glycol-anhydrous ethanol dispersion. The obtained (W, Ti) C metal ceramic mixed powder is subjected to a first ball milling treatment; The acidified and purified CNTs are dispersed and added to the (W,Ti)C metal ceramic mixed powder that has been ball-milled for the first time, and then ball-milled for the second time and dried. The dried mixed powder is subjected to a third ball milling process to obtain a mixed powder, and the mixed powder is subjected to spark plasma coupled high frequency induction sintering to obtain the obtained product.

[0009] In a third aspect, the present invention provides the use of the above-mentioned carbon nanotube reinforced tungsten carbide titanium metal ceramic material in the preparation of ceramic cutting tools and electric spark machining electrodes.

[0010] In a fourth aspect, the present invention provides a metal ceramic cutting tool comprising the above-mentioned carbon nanotube reinforced tungsten carbide titanium metal ceramic material.

[0011] One or more of the above technical solutions have the following advantages or beneficial effects: (1) The present invention discloses a carbon nanotube-reinforced tungsten carbide titanium metal ceramic tool material, which has a (W,Ti)C ceramic matrix, a highly conductive CNTs as a reinforcement phase, and Ni, Mo, and Co as a metal binder phase. The addition of carbon nanotubes can make the carbon nanotube-reinforced tungsten carbide titanium metal ceramic material not only have excellent mechanical properties but also excellent conductivity, thereby reducing the sintering temperature.

[0012] (2) The present invention adopts discharge plasma coupled high-frequency induction sintering. The preparation method is to first wet-mill (W, Ti) C, Ni, Mo, and Co, then add the dispersed CNTs and perform a second wet-milling, dry-mill for a third time after drying to obtain a mixed powder, and then adopt discharge plasma coupled high-frequency induction sintering. This method is conducive to improving the dispersion effect of CNTs. By utilizing the discharge sintering effect of highly conductive CNTs, the current intensity required for (W, Ti) C metal ceramic tool materials is reduced, sintering is completed at a lower sintering temperature, the density is greatly improved, and grain refinement is achieved, thereby improving the mechanical properties of the material, and having the advantages of reducing energy consumption and saving costs.

[0013] (3) The (W,Ti)C metal ceramic cutting tool prepared by the present invention has higher toughness and hardness as well as excellent anti-friction and wear resistance, and can be applied in the field of high-speed and high-efficiency cutting processing.

[0014] (4) The present invention adopts a dry ball milling method to disperse CNTs again, so that CNTs are uniformly dispersed in the (W,Ti)C-based cermet powder. Through the dispersion treatment, the CNTs are well dispersed in the cermet material. During the spark plasma coupled high-frequency induction sintering process, the CNTs form a continuous conductive network along the grain boundaries, reducing the contact resistance between the powder particles by 1 to 2 orders of magnitude, making it easier for the pulse current to generate Joule heat and spark discharge between the particles, thereby reducing the breakdown voltage.

[0015] (5) Compared with the existing method that requires densification sintering of materials at 1450°C, the present invention adopts discharge plasma coupled high-frequency induction sintering. By adding carbon nanotubes and utilizing the good conductivity of carbon nanotubes to improve the discharge environment, the material densification sintering is completed at 1350°C, which reduces the sintering temperature by 100°C, reduces energy loss, and reduces the sintering current peak by 143A, greatly reducing production costs.

[0016] (6) The present invention provides a method for preparing a carbon nanotube-reinforced tungsten carbide titanium metal ceramic material with better comprehensive mechanical properties. The parameters of the obtained metal ceramic material sample are: average grain size 3.8~4.6μm, relative density 98.6~99.4%, flexural strength 983~1127MPa, fracture toughness 7.3~8.7MPa·m 1 / 2 , hardness 18.69~19.83GPa. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0018] Figure 1 The dispersion of CNTs in the metal ceramic powder after dry ball milling in the embodiment of the present invention; Figure 2 sintering current curves during spark plasma coupled high frequency induction sintering in Comparative Example 1 and Example 2 of the present invention; Figure 3 This is a cross-sectional morphology of the carbon nanotube-reinforced tungsten carbide titanium metal ceramic material obtained in Example 2 of the present invention; Figure 4 are morphologies of Comparative Examples 1 to 5 of the present invention; wherein, (a) is a morphology of Comparative Example 1, (b) is a morphology of Comparative Example 2, (c) is a morphology of Comparative Example 3, (d) is a morphology of Comparative Example 4, and (e) is a morphology of Comparative Example 5; Figure 5 Elemental analysis diagram of the crack on the polished surface and its extension of the material prepared in Example 2 of the present invention; wherein (a) is the morphology diagram of the crack on the polished surface, and (b) is the elemental analysis diagram of the extension of the crack on the polished surface. DETAILED DESCRIPTION

[0019] In the present invention, unless otherwise specified, other test materials and instruments and equipment are conventional test materials in this field and can be purchased through commercial channels.

[0020] In the present invention, "+" means "and".

[0021] The following standards are used for testing materials: Flexural Strength: Three-point bending method, ASTM C1161 / ISO 14705.

[0022] Fracture toughness: indentation method, IF method, ISO 28079.

[0023] Vickers hardness: Vickers indentation method, ASTM E384 / ISO 6507-1, where Vickers hardness is measured at a load of 196N.

[0024] Given the shortcomings of existing technologies, there is an urgent need to develop a method for preparing (W,Ti)C-based cermets with low energy consumption and excellent mechanical properties. This invention utilizes (W,Ti)C ceramics as a matrix, adds Ni, Mo, and Co as the metal phase, and uses CNTs as a reinforcement phase. The process is fabricated through spark plasma-coupled high-frequency induction sintering. By utilizing the excellent electrical conductivity of carbon nanotubes, the discharge environment is improved, achieving material densification during sintering.

[0025] Among them, carbon nanotubes (CNTs) are seamless microtubes formed by the arrangement and curling of carbon atoms in a tubular structure. They are divided into single-walled carbon nanotubes and multi-walled carbon nanotubes according to the number of carbon atom layers. The carbon atoms in CNTs are all sp2 Hybridized, they are bonded by CC bonds, so they have the characteristics of high hardness, high modulus and high strength. In addition, carbon nanotubes (CNTs) have the characteristics of high hardness, high modulus and high strength due to the one-dimensional quantum confinement effect and sp 2 Ultra-high current density (>10 9 A cm -2 ) and ballistic transport length (micrometer level), it can be used as an ideal alternative material to break through the "electromigration bottleneck" of traditional copper interconnects.

[0026] (W,Ti)C cermets possess excellent electrical conductivity (far superior to Ti(C,N)-based cermets). Under spark plasma-coupled high-frequency induction sintering, the electrical conductivity of the (W,Ti)C cermet and CNTs is not simply superimposed, but rather exhibits a coupled relationship of "complementarity, synergy, and amplification," resulting in a complementary "ultra-high electrical conductivity" effect and a synergistic loop of low-resistance pathways, high thermal bridges, and uniform temperature fields. The high electrical conductivity of CNTs is leveraged to reduce the current intensity required for sintering the (W,Ti)C-based cermet, allowing sintering to be completed at lower temperatures and suppressing grain growth. According to the Hall-Petch relationship, grain refinement contributes to improved mechanical properties, resulting in significantly improved mechanical properties of the (W,Ti)C cermet tool material. This is the result of the complementary ultra-high electrical conductivity of the two, something that cannot be achieved with a single conductive phase.

[0027] The technical effects of adding carbon nanotubes vary depending on the matrix. If carbon nanotubes are added to a Ti(C,N) matrix, all the technical effects of the present invention cannot be achieved simultaneously. The specific reasons are as follows: (1) The wetting angle between (W,Ti)C and the metal binder phase (Co / Ni / Mo) is slightly smaller than that of Ti(C,N), so CNTs are more easily wrapped by the liquid phase and have a higher grain boundary pinning efficiency. Ti(C,N) is prone to denitrification during the heating process, and CNTs mainly inhibit denitrification holes. However, (W,Ti)C has no denitrification problem, and CNTs are more focused on inhibiting the reprecipitation and growth of WC. Therefore, the matrix is ​​different, and the mechanism of action between the matrix and carbon nanotubes is different, and the grain refinement range of the present invention is larger.

[0028] (2) Diffusion activation energy: W solid solution increases the diffusion activation energy of the matrix. The "fast thermal and electrical conductivity network" of CNTs exhibits more significant local Joule heat compensation and diffusion channel shortening effects in (W,Ti)C. Therefore, the addition of CNTs to (W,Ti)C causes a greater decrease in the sintering temperature, while the change is not obvious when added to the Ti(C,N) matrix.

[0029] (3) The electrical conductivity of (W,Ti)C cermets is 1-2 orders of magnitude higher than that of the Ti(C,N) system, and is closer to that of traditional cemented carbide. While titanium carbonitride cermets are conductive, they are still in the "moderately conductive" category, and the resistance needs to be further reduced by increasing the metal binder phase content or adding a third phase. Therefore, the addition of highly conductive CNTs significantly reduces the peak sintering current of highly conductive (W,Ti)C cermets, while for low-conductivity Ti(C,N), the "complementary-synergistic-amplification" coupling relationship cannot be achieved, and the complementary effect of "ultra-high conductivity" cannot be achieved.

[0030] In summary, the present invention uses (W, Ti) C metal ceramics as the matrix and adds CNTs, which can make good use of the high conductivity of the (W, Ti) C matrix itself and the high conductivity of CNTs. It can play a synergistic role in spark plasma coupled high-frequency induction sintering to achieve the effects of reducing the sintering current peak, lowering the sintering temperature, and refining the grains, ultimately achieving the goal of reducing energy consumption and production costs.

[0031] This invention utilizes the discharge effect of carbon nanotubes to form a "CNTs conductive and thermal bridge + rapid Joule heating spike + traditional liquid phase" system. This system utilizes the one-dimensional quantum transport of CNTs to achieve "low-temperature fast heating," resulting in a material with integrated mechanical and electrical conductivity. This invention relies on "one-dimensional CNT enhancement + electric-thermal field coupling."

[0032] In a first embodiment, the present invention provides a carbon nanotube-reinforced tungsten carbide titanium metal ceramic material (CNTs-(W,Ti)C), comprising a matrix, a metal bonding phase, and a reinforcement phase, wherein the matrix is ​​(W,Ti)C, the reinforcement phase is carbon nanotubes (CNTs), and the metal bonding phase is Ni, Mo, and Co; the mass percentage of each component is: (W,Ti)C 84.5~85%, Ni 3~4%, Mo 6~7%, Co 4.5~5.5%, CNTs 0~0.5%, and the sum of the mass of each component is 100%.

[0033] To further achieve better technical effects, the weight percentages of the components are: (W, Ti) C 84.5-85%, Ni 3-4%, Mo 6-7%, Co 4.5-5.5%, CNTs 0.01-0.5%, with the total weight of each component being 100%. Furthermore, the weight percentages of the components are: (W, Ti) C 84.5-85%, Ni 3-4%, Mo 6-7%, Co 4.5-5.5%, CNTs 0.1-0.5%, with the total weight of each component being 100%.

[0034] The specific amount of CNTs added can be 0%, 0.01%, 0.05%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, or 0.5%. Preferably, the amount of CNTs is 0.1-0.3%. When the amount of CNTs added is too low, the CNTs cannot form an effective reinforcing skeleton, resulting in limited conductivity and performance improvements. When the amount of CNTs added is too high, agglomeration leads to decreased density and interfacial bonding, and overall deterioration of mechanical and functional properties.

[0035] In one or more embodiments, the average particle size of the (W,Ti)C powder is 1-3 μm, preferably 2-2.5 μm. The average particle size of the Ni powder, Mo powder, and Co powder is 1-1.5 μm.

[0036] There are no specific restrictions on carbon nanotubes (CNTs). They can be multi-walled or single-walled, with multi-walled CNTs being preferred, with typical diameters ranging from 7 to 30 nm and lengths from 5 to 20 µm. This is because the 7-30 nm diameter and the (W,Ti)C particles (2 to 2.5 µm) form a "particle-fiber" scale synergy, preventing blockage of liquid phase channels while effectively pinning at grain boundaries. Compared to single-walled CNTs, multi-walled CNTs offer increased rigidity and fewer defects, maintaining structural integrity under the transient high pressures of SPS. Furthermore, their multi-walled walls provide additional electrical and thermal conduction pathways, resulting in more uniform local current flow and Joule heating distribution.

[0037] The average grain size of the carbon nanotube-reinforced tungsten carbide titanium metal ceramic material is 3.5-5 μm, preferably 3.8-4.6 μm, and the relative density of the material is greater than 98%, preferably greater than 98.5%, and more preferably 99%, such as 98-99.5%.

[0038] In this invention, three metal components—Ni powder, Mo powder, and Co powder—form the metallic binder phase. Their roles in the SPS-HF (spark plasma coupled high-frequency induction sintering) CNTs-(W,Ti)C system are "liquid phase formation + interfacial wetting + carbon activity buffering." Ni, Mo, and Co are not randomly combined; each performs a specific function. Any addition or subtraction significantly alters the final microstructure and properties through three pathways: liquidus temperature, wetting angle, and carbon activity.

[0039] (1) “Division of labor” of existing ternary bonding phases Co (main binder phase): forms a low-melting eutectic (≈1280°C) with (W,Ti)C, providing a highly fluid liquid phase to ensure rapid densification; with a wetting angle of 25~30° for CNTs, it is the core of forming a continuous metal network.

[0040] Ni (auxiliary wetting): Lowers the liquidus by 20-30°C, improves chemical affinity with CNTs, and reduces CNT agglomeration; at the same time, it forms an infinite solid solution with Co, inhibiting the precipitation of brittle η phase.

[0041] Mo (carbon activity buffer + solid solution strengthening): preferentially reacts with free carbon to form Mo2C, preventing excessive dissolution of CNTs; after solid solution in the hard phase, it increases the hardness by 5~8%.

[0042] (2) The impact of omitting an element Removing Co: The liquidus rises to above 1380℃, and the SPS temperature needs to be increased from 1450℃ to 1500℃, the grain coarsening is 30%, and the toughness decreases by 25%.

[0043] Or, remove Ni: the liquid phase wetting angle increases to 45°, CNTs show obvious agglomeration, the conductive network is discontinuous, and the resistivity increases by one order of magnitude.

[0044] Alternatively, removing Mo: the free carbon activity increases, and CNTs begin to be eroded by the liquid phase at 1350 °C, resulting in a 12% decrease in hardness and a 2% increase in porosity.

[0045] (3) Effect of introducing the fourth metal powder Adding a small amount of Fe (≤3wt%): the liquidus line drops by another 15℃, which can further refine the grains. However, if the temperature is >3wt%, brittle (Fe, Co)7W6 phase is easily generated, and the toughness drops sharply.

[0046] Alternatively, adding Cr: improves oxidation resistance but reduces wettability, and requires simultaneously increasing the sintering temperature by 20~30℃ to offset the refinement effect.

[0047] Alternatively, adding Cu: the liquid phase wetting angle drops sharply to 15°, but the interface reaction between Cu and CNTs is weak, resulting in poor interface bonding and an 18% decrease in flexural strength.

[0048] Alternatively, add Al powder: Al reacts weakly with the CNTs interface to form Al4C3 brittle phase, and the flexural strength will drop by about 18%; when Al>3wt%, continuous Al4C3 at the grain boundary causes cracks to extend along the grain, and the toughness drops sharply.

[0049] Alternatively, adding Ti powder: Ti reacts with CNTs to form a TiC coating. While this protects the CNTs, it also deprives them of their electrical and thermal bridge functions, increasing resistivity by a factor of two. Although the (W,Ti)C matrix contains Ti, it is a carbide and does not react with the CNTs. When Ti content exceeds 2wt%, the TiC coating becomes too thick, hindering liquid penetration and reducing density by 3%.

[0050] In summary, the Ni-Mo-Co ternary binder phase forms an optimal balance of "low melting point, high wettability, and carbon activity buffer" in the CNTs-(W,Ti)C system. The absence of any single element significantly degrades the densification temperature, CNT integrity, or mechanical properties. If a fourth metal is introduced, its content must be limited to 1-3 wt% and verified for interfacial reactions; otherwise, the overall gains will be offset by brittle phases or wetting imbalances.

[0051] In a second embodiment, the present invention provides a method for preparing the carbon nanotube-reinforced tungsten carbide titanium metal ceramic material, comprising the following steps: (W, Ti) C powder, Ni powder, Mo powder, and Co powder are mixed according to a mass ratio and dispersed in a polyethylene glycol-anhydrous ethanol dispersion. The obtained (W, Ti) C metal ceramic mixed powder is subjected to a first ball milling treatment; The purified and neutralized CNTs are dispersed and added to the (W,Ti)C metal ceramic mixed powder after the first ball milling, and then subjected to a second ball milling process and dried. The dried mixed powder is subjected to a third ball milling process to obtain a mixed powder, and the mixed powder is subjected to spark plasma coupled high frequency induction sintering to obtain the obtained product.

[0052] In one or more embodiments, polyethylene glycol is added to anhydrous ethanol, stirred in a water bath, and cooled to room temperature to prepare a polyethylene glycol-anhydrous ethanol dispersion. The water bath is kept at a constant temperature of 60-70°C, and the stirring is performed using magnetic stirring for 15-20 minutes. The polyethylene glycol dispersion contains 3-5 g / L of polyethylene glycol.

[0053] The mass of polyethylene glycol in the polyethylene glycol-anhydrous ethanol dispersion is 0.5% to 1.5% of the total mass of the (W,Ti)C powder, the Ni powder, the Mo powder, and the Co powder. Specifically, the mass can be 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, or 1.5%, preferably 0.9% to 1.1%, and most preferably 1%.

[0054] The molecular weight of polyethylene glycol is 5000-7000, preferably PEG6000.

[0055] (W,Ti)C powder, Ni powder, Mo powder, and Co powder are mixed and added to the prepared polyethylene glycol-anhydrous ethanol dispersion. Ultrasonic dispersion and stirring are performed to produce a (W,Ti)C metal ceramic mixed powder. Ultrasonic dispersion is performed for 45-60 minutes, and mechanical stirring is used to achieve sufficient dispersion.

[0056] In one or more embodiments, the first ball milling process is performed in a protective atmosphere at a weight ratio of 1:8-15 of the total raw material ((W,Ti)C powder, Ni powder, Mo powder, and Co powder) to the grinding balls. The milling is performed for 24-72 hours. Preferably, the milling time is 40-60 hours (preferably 44-47 hours). The first ball milling process is wet milling.

[0057] The protective atmosphere during ball milling was nitrogen, and the grinding balls used were cemented carbide grinding balls. The cemented carbide balls were a mixture of 4 mm and 8 mm diameter cemented carbide grinding balls, with a mass ratio of 4 mm to 8 mm diameter cemented carbide balls of (2-2.5):(3-3.5). The mass ratio of balls to materials was (10-15):1.

[0058] In one or more embodiments, the purification (acidification) treatment of CNTs is as follows: mixing CNTs with a sufficient amount of concentrated nitric acid, ultrasonically vibrating for 20 to 40 minutes, and then allowing to stand for 12 to 36 hours (preferably 20 to 30 hours), ultrasonically vibrating for a second time for 1 to 5 hours (preferably 2 to 4 hours), and then allowing to stand for 12 to 36 hours (preferably 20 to 30 hours), and ultrasonically vibrating for a third time for 1 to 5 hours (preferably 2 to 4 hours), and then allowing to stand for 0.5 to 3 hours (preferably 1.5 to 2.5 hours).

[0059] Use 25-35 wt% analytical grade concentrated nitric acid. There's no specific limit on the amount of concentrated nitric acid needed, as long as it's sufficient for dispersion. For example, to disperse 0.05-0.15 g of CNTs at a time, use 150-200 ml of concentrated nitric acid.

[0060] After purification (acidification), neutralization and washing are performed to obtain neutralized CNTs. During this neutralization and washing process, the centrifugation parameters are set to a speed of 6000-7000 rpm, preferably 6500 rpm, for 4-6 minutes, preferably 5 minutes. The centrifugation is repeated 5-8 times until the pH of the CNT suspension reaches 6.8-7.2. Distilled water is used as the washing agent.

[0061] In one or more embodiments, sodium lauryl sulfate is dissolved in anhydrous ethanol, heated in a water bath to fully dissolve the sodium lauryl sulfate, and then the neutralized CNTs are added, and the mixture is vigorously stirred and dispersed in an ultrasonic bath for 0.5 to 2 hours to obtain dispersed CNTs.

[0062] Furthermore, during the dispersion of the CNTs, the mass ratio of sodium lauryl sulfate to CNTs is (0.9-1.1):(0.9-1.1), preferably 1:1.

[0063] Furthermore, the temperature and time of water bath heating are not specifically limited, and existing conventional parameters can be used as long as the sodium lauryl sulfate is fully dissolved.

[0064] In one or more embodiments, the second ball milling process is performed for a time of 2 to 4 hours (preferably 2.5 to 3.5 hours) and is wet ball milling.

[0065] Specifically, the metal ceramic matrix is ​​ball-milled for a total of 48 hours during the two wet ball-milling processes. After the ball-milling process reaches 45 hours, the dispersed CNTs are added and the ball-milling process is completed for the remaining 3 hours.

[0066] In one or more embodiments, the dried mixed powder is subjected to a third ball milling treatment, which may be performed by vacuum drying at a vacuum drying temperature of 115-125° C. for a vacuum drying time of 36-48 h, preferably 42 h.

[0067] In one or more embodiments, the third ball milling treatment is dry ball milling for 0.5 to 1.5 hours. After dry ball milling, the powder is sieved using a 100-300 mesh, preferably 200 mesh. Dry ball milling is used to further disperse the CNTs, resulting in a uniform dispersion of the CNTs within the (W,Ti)C-based cermet powder.

[0068] In one or more embodiments, the mixed powder is placed in a graphite mold and subjected to spark plasma coupled high-frequency induction sintering in a vacuum atmosphere to produce a carbon nanotube reinforced tungsten carbide titanium metal ceramic material.

[0069] In spark plasma coupled high-frequency induction sintering, the sintering temperature is 1300°C to 1400°C, specifically 1300°C, 1310°C, 1320°C, 1330°C, 1340°C, 1350°C, 1360°C, 1370°C, 1380°C, 1390°C, 1400°C, etc., preferably 1300°C to 1380°C, more preferably 1320°C to 1380°C, and most preferably 1350°C. Sintering cannot be achieved at temperatures that are too low, while excessively high temperatures can lead to abnormal grain growth and the presence of numerous pores in the cross-section of the material.

[0070] In spark plasma coupled high frequency induction sintering, the sintering pressure is 30-40 MPa, such as 30 MPa, 32 MPa, 33 MPa, 34 MPa, 35 MPa, 36 MPa, 37 MPa, 38 MPa, 40, etc., preferably 34-36 MPa.

[0071] In the spark plasma coupled high-frequency induction sintering, the specific heating rates include: preheating to 560-580°C (such as 570°C), and heating to 590-610°C (such as 600°C) within 1 minute; heating to 890-910°C (such as 900°C) at 90-110°C / min (such as 100°C / min); heating to 1240-1260°C (such as 1250°C) at 70-80°C / min (such as 75°C / min); heating to the target temperature at 45-55°C / min (such as 50°C / min), and holding time of 5-15 minutes (such as 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 minutes, preferably 8-12 minutes).

[0072] Before the addition of carbon nanotubes, the peak sintering current was above 2700 A, such as 2745 A in Comparative Example 1. After the addition of carbon nanotubes, the peak sintering current was lower than 2700 A, specifically 2684 A, 2620 A, 2653 A, 2636 A, 2675 A, etc., preferably 2600-2690 A, and more preferably 2620-2685 A.

[0073] The present invention's preparation of carbon nanotube-reinforced tungsten-titanium carbide ceramic material requires the use of a spark plasma-coupled high-frequency induction sintering process. Using cold pressing followed by vacuum hot pressing sintering will not achieve the same technical benefits as the present invention for the following reasons: (1) First, a key point of the present invention is to utilize the high conductivity of CNTs to reduce the sintering current through spark plasma coupled high-frequency induction sintering (SPS-HF), thereby reducing the sintering temperature, energy consumption and production costs. However, the cold pressing followed by vacuum hot pressing sintering method does not involve the use of an electric field and cannot utilize the high conductivity of CNTs.

[0074] The pulsed direct current of SPS-HF generates instantaneous Joule heating and microplasma at the CNTs-(W,Ti)C interface, raising the local temperature by 200-300°C in less than 60 seconds. This causes the CNTs to straighten and embed themselves into the particle surface, forming a low-resistance conductive network. Vacuum hot pressing relies solely on external radiation heating, with a heating rate of ≤15°C / min. CNTs relax and aggregate between 800-1200°C, losing their one-dimensional orientation and causing subsequent breakage of the conductive / thermal bridges.

[0075] (2) Influence of constant pressure environment, etc. Spark plasma coupled high frequency induction sintering is completed in a constant pressure environment, which can significantly inhibit the growth of grains through constant pressure. However, the method of cold pressing followed by vacuum hot pressing sintering has no pressure field during the sintering process. During the sintering process, the grains will grow uncontrollably due to heat, and good densification sintering cannot be achieved.

[0076] SPS-HF achieves densification simultaneously with a 35MPa uniaxial pressure and 10-minute heat hold, inhibiting WC reprecipitation and achieving grain refinement. Vacuum hot pressing, on the other hand, requires 30-60 minutes to achieve the same density, and the prolonged high temperature promotes WC growth.

[0077] (3) Rapid sintering by spark plasma coupled high-frequency induction sintering can achieve rapid heating of the material and rapid densification of the material, ensuring the integrity of CNTs and achieving densification sintering.

[0078] The rapid densification process of SPS-HF (5-15 minutes) locks oxygen and nitrogen impurities outside the grain boundaries, preserving the integrity of the carbon layer on the CNT surface. However, prolonged exposure to vacuum hot pressing (>30 minutes) causes the CNTs to react with trace oxygen to form CO / CO₂, resulting in a 5-10 nm decarbonized layer at the interface. This increases the resistivity by an order of magnitude and eliminates the conductivity-enhancing effect.

[0079] To sum up: cold pressing-vacuum hot pressing lacks the three-field coupling of "pulsed electric field-instantaneous high temperature-constant pressure", and cannot simultaneously achieve CNTs orientation maintenance, grain refinement, rapid densification and interface cleanliness. Therefore, it cannot replicate the conductive-mechanical synergistic gain brought by discharge plasma coupled high-frequency induction sintering, resulting in the failure of the technical effect.

[0080] The sintering process of spark plasma coupled high-frequency induction sintering (SPS-HF) involves the strong coupling of four physical fields: electric, thermal, magnetic, and mechanical. This is primarily the mutual coupling between the electromagnetic field and the thermal, stress, and thermal fields. The magnetic induction heating of the high-frequency coil and the Joule heating generated by the SPS-HF pulsed current flowing through the powder particles demonstrate the coupling of the electromagnetic and thermal fields, promoting material densification. The alternating magnetic field promotes liquid flow. The primary parameter of the stress field is axial pressure, which is also the primary driving force for densification. The interaction between temperature and pressure enhances the viscosity and plastic flow of the particles, promoting densification. This coupling promotes the sintering of metal-ceramic materials.

[0081] As a preferred embodiment, a method for preparing a carbon nanotube reinforced tungsten carbide titanium metal ceramic material comprises the following steps: (1) Add polyethylene glycol to anhydrous ethanol, stir in a water bath at a constant temperature, and cool to room temperature to prepare a polyethylene glycol-anhydrous ethanol dispersion.

[0082] (2) Mix (W, Ti) C powder, Ni powder, Mo powder and Co powder according to the mass ratio, add them to the prepared polyethylene glycol-anhydrous ethanol dispersion, ultrasonically disperse and stir to obtain a (W, Ti) C metal ceramic mixed powder.

[0083] (3) Pour the prepared mixed solution and grinding balls into a tank, set a certain weight ratio between the total amount of raw materials and the number of grinding balls (e.g., 1:10), and ball mill under a protective atmosphere for, e.g., 48 hours.

[0084] (4) Add sufficient concentrated nitric acid to the beaker containing CNTs, ultrasonically vibrate (e.g., for 30 minutes) and then let it stand (e.g., for 24 hours), ultrasonically vibrate for the second time (e.g., for 3 hours) and then let it stand (e.g., for 24 hours), and ultrasonically vibrate for the third time (e.g., for 3 hours) and then let it stand (e.g., for 2 hours).

[0085] (5) The purified CNTs are neutralized and cleaned using a centrifuge and set aside.

[0086] (6) Weigh a certain amount of sodium dodecyl sulfate and pour it into a beaker. Add an appropriate amount of anhydrous ethanol to the beaker to fully dissolve the sodium dodecyl sulfate by heating in a water bath. Add the purified CNTs to the beaker and vigorously stir and disperse them in an ultrasonic bath (60 min).

[0087] (7) Add the dispersed CNTs to the milled (W,Ti)C metal ceramic mixed powder and continue milling (e.g., for 3 h). Vacuum dry the milled slurry.

[0088] (8) The dried mixed powder is put back into the ball mill for dry ball milling and then sieved to obtain the mixed powder, which is then sealed for later use.

[0089] (9) The prepared mixed powder is placed in a graphite mold and subjected to discharge plasma coupled high-frequency induction sintering in a vacuum atmosphere to obtain a carbon nanotube reinforced tungsten carbide titanium metal ceramic material.

[0090] In a third embodiment, the present invention provides the use of the carbon nanotube-reinforced tungsten carbide titanium metal ceramic material in the preparation of ceramic cutting tools and EDM electrodes. The material prepared by the present invention has high electrical conductivity and can be used in EDM (Electro-Discharge Machining) electrodes.

[0091] In a fourth embodiment, the present invention provides a metal ceramic cutting tool comprising the above-mentioned carbon nanotube reinforced tungsten carbide titanium metal ceramic material.

[0092] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0093] Example 1 In the embodiment, the average particle size of the (W, Ti) C powder is 1-3 μm, and the average particle size of the Ni, Mo, and Co powders is 1-1.5 μm, all of which are commercially available products. The polyethylene glycol is PEG6000.

[0094] The mass percentage of each component in the carbon nanotube reinforced tungsten carbide titanium metal ceramic material is: (W, Ti) C 84.9%, Ni 3.5%, Mo 6.5%, Co 5%, and CNTs 0.1%.

[0095] The preparation method of the carbon nanotube reinforced tungsten carbide titanium metal ceramic material comprises the following steps: (1) Place anhydrous ethanol in a beaker, weigh and add polyethylene glycol, place the beaker in a water bath, and stir magnetically at 65°C for 15 minutes until the polyethylene glycol is completely dissolved. Cool to room temperature to obtain a polyethylene glycol-anhydrous ethanol dispersion with a dispersion volume of 3 g / L. (2) Mix the powders of (W, Ti) C 84.9%, Ni 3.5%, Mo 6.5%, and Co 5% according to the mass percentage of each component, add them to the polyethylene glycol-anhydrous ethanol dispersion prepared in step (1), ultrasonically disperse for 60 minutes and mechanically stir to prepare a mixed solution; the mass of polyethylene glycol in the polyethylene glycol-anhydrous ethanol dispersion is 1% of the total mass of the (W, Ti) C, Ni, Mo, and Co powders; (3) The prepared mixed solution was placed in a ball mill, wherein the grinding balls used in the ball mill were cemented carbide grinding balls, the cemented carbide balls were mixed cemented carbide grinding balls with diameters of 4 mm and 8 mm, the mass ratio of cemented carbide balls with diameters of 4 mm and 8 mm was 2:3, and the mass ratio of balls to materials was 10:1, and the ball milling was carried out under a nitrogen protective atmosphere for 48 h; (4) Weigh 0.1% of the total mass of CNTs and place them in a beaker for purification. Add sufficient concentrated nitric acid to the beaker containing CNTs, ultrasonically vibrate for 30 minutes, then let it stand for 24 hours. Ultrasonicate for the second time for 3 hours, then let it stand for 24 hours. Ultrasonicate for the third time for 3 hours, then let it stand for 2 hours. (5) The purified CNTs were neutralized and cleaned using a centrifuge and then set aside. A Michael high-speed centrifuge was used with the centrifugation parameters set to a speed of 6500 r / min and a time of 5 min. The centrifugation was repeated 7 times until the pH value of the CNT suspension reached 7. The cleaning agent was distilled water. (6) Weigh the same mass of sodium dodecyl sulfate as that of CNTs and pour it into a beaker. Add 100 ml of anhydrous ethanol to the beaker to fully dissolve the sodium dodecyl sulfate by heating in a water bath. Add the neutralized CNTs to the beaker and vigorously stir and disperse them in an ultrasonic bath for 60 min. (7) Add the dispersed CNTs to the milled (W,Ti)C metal ceramic powder mixture and continue milling for 3 h. Dry the milled slurry in a vacuum at 120 °C for 36 h. (8) The dried mixed powder is put into the ball mill again for dry ball milling for 1 hour, and then passed through a 200-mesh sieve to obtain carbon nanotube-reinforced tungsten carbide titanium metal ceramic powder, which is sealed and set aside.

[0096] (9) The carbon nanotube reinforced tungsten carbide titanium metal ceramic powder was placed in a graphite mold and subjected to spark plasma coupled high-frequency induction sintering in a vacuum atmosphere. The sintering temperature was 1350℃, the sintering pressure was 35MPa, and the heating rate was as follows: preheating to 570℃ and heating to 600℃ within 1min; heating to 900℃ at 100℃ / min; heating to 1250℃ at 75℃ / min; heating to the target temperature at 50℃ / min, and holding time was 10min to obtain carbon nanotube reinforced tungsten carbide titanium metal ceramic material. The sintering current peak was 2684A, the average grain size was 4.4μm, and the relative density of the material was 99.3%. The obtained ceramic material sample was cut and processed, and its mechanical properties were measured as follows: flexural strength 1046MPa, fracture toughness 7.3MPa·m 1 / 2 , Vickers hardness 19.45GPa.

[0097] Example 2 In the embodiment, the average particle size of the (W, Ti) C powder is 1-3 μm, and the average particle size of the Ni, Mo, and Co powders is 1-1.5 μm, all of which are commercially available products. The polyethylene glycol is PEG6000.

[0098] The mass percentages of the components in the carbon nanotube-reinforced tungsten carbide titanium metal ceramic material are as follows: (W, Ti) C 84.8%, Ni 3.5%, Mo 6.5%, Co 5%, and CNTs 0.2%.

[0099] The preparation method of the carbon nanotube reinforced tungsten carbide titanium metal ceramic material comprises the following steps: (1) Place anhydrous ethanol in a beaker, weigh and add polyethylene glycol, place the beaker in a water bath, and stir magnetically at 65°C for 15 minutes until the polyethylene glycol is completely dissolved. Cool to room temperature to obtain a polyethylene glycol-anhydrous ethanol dispersion with a dispersion volume of 3 g / L. (2) Mix the powders of (W, Ti) C 84.8%, Ni 3.5%, Mo 6.5%, and Co 5% according to the mass percentage of each component, add them to the polyethylene glycol-anhydrous ethanol dispersion prepared in step (1), ultrasonically disperse for 60 minutes and mechanically stir to prepare a mixed solution; the mass of polyethylene glycol in the polyethylene glycol-anhydrous ethanol dispersion is 1% of the total mass of the (W, Ti) C, Ni, Mo, and Co powders; (3) The prepared mixed solution was placed in a ball mill, wherein the grinding balls used in the ball mill were cemented carbide grinding balls, the cemented carbide balls were mixed cemented carbide grinding balls with diameters of 4 mm and 8 mm, the mass ratio of cemented carbide balls with diameters of 4 mm and 8 mm was 2:3, and the mass ratio of balls to materials was 10:1, and the ball milling was carried out under a nitrogen protective atmosphere for 48 h; (4) Weigh 0.2% of the total mass of CNTs and place them in a beaker for purification. Add sufficient concentrated nitric acid to the beaker containing CNTs, ultrasonically vibrate for 30 minutes, then let it stand for 24 hours. Ultrasonicate for the second time for 3 hours, then let it stand for 24 hours. Ultrasonicate for the third time for 3 hours, then let it stand for 2 hours. (5) The purified CNTs were neutralized and cleaned using a centrifuge and then set aside. A Michael high-speed centrifuge was used with the centrifugation parameters set to a speed of 6500 r / min and a time of 5 min. The centrifugation was repeated 7 times until the pH value of the CNT suspension reached 7. The cleaning agent was distilled water. (6) Weigh the same mass of sodium dodecyl sulfate as that of CNTs and pour it into a beaker. Add 100 ml of anhydrous ethanol to the beaker to fully dissolve the sodium dodecyl sulfate by heating in a water bath. Add the neutralized CNTs to the beaker and vigorously stir and disperse them in an ultrasonic bath for 60 min. (7) Add the dispersed CNTs to the milled (W,Ti)C metal ceramic powder mixture and continue milling for 3 h. Dry the milled slurry in a vacuum at 120 °C for 36 h. (8) The dried mixed powder is put into the ball mill again for dry ball milling for 1 hour, and then passed through a 200-mesh sieve to obtain carbon nanotube-reinforced tungsten carbide titanium metal ceramic powder, which is sealed and set aside.

[0100] (9) The carbon nanotube reinforced tungsten carbide titanium metal ceramic powder was placed in a graphite mold and subjected to spark plasma coupled high-frequency induction sintering in a vacuum atmosphere. The sintering temperature was 1350℃, the sintering pressure was 35MPa, and the heating rate was as follows: preheating to 570℃ and heating to 600℃ within 1min; heating to 900℃ at 100℃ / min; heating to 1250℃ at 75℃ / min; heating to the target temperature at 50℃ / min, and holding time was 10min to obtain carbon nanotube reinforced tungsten carbide titanium metal ceramic material. The sintering current peak was 2602A, the average grain size was 4.1μm, and the relative density of the material was 99.4%. The obtained ceramic material sample was cut and processed, and its mechanical properties were measured as follows: flexural strength 1127MPa, fracture toughness 7.5MPa·m 1 / 2 , Vickers hardness 19.83GPa.

[0101] Example 3 In the embodiment, the average particle size of the (W, Ti) C powder is 1-3 μm, and the average particle size of the Ni, Mo, and Co powders is 1-1.5 μm, all of which are commercially available products. The polyethylene glycol is PEG6000.

[0102] The mass percentages of the components in the carbon nanotube-reinforced tungsten carbide titanium metal ceramic material are as follows: (W, Ti) C 84.7%, Ni 3.5%, Mo 6.5%, Co 5%, and CNTs 0.3%.

[0103] The preparation method of the carbon nanotube reinforced tungsten carbide titanium metal ceramic material comprises the following steps: (1) Place anhydrous ethanol in a beaker, weigh and add polyethylene glycol, place the beaker in a water bath, and stir magnetically at 65°C for 15 minutes until the polyethylene glycol is completely dissolved. Cool to room temperature to obtain a polyethylene glycol-anhydrous ethanol dispersion with a dispersion volume of 3 g / L. (2) Mix the powders of (W, Ti) C 84.8%, Ni 3.5%, Mo 6.5%, and Co 5% according to the mass percentage of each component, add them to the polyethylene glycol-anhydrous ethanol dispersion prepared in step (1), ultrasonically disperse for 60 minutes and mechanically stir to prepare a mixed solution; the mass of polyethylene glycol in the polyethylene glycol-anhydrous ethanol dispersion is 1% of the total mass of the (W, Ti) C, Ni, Mo, and Co powders; (3) The prepared mixed solution was placed in a ball mill, wherein the grinding balls used in the ball mill were cemented carbide grinding balls, the cemented carbide balls were mixed cemented carbide grinding balls with diameters of 4 mm and 8 mm, the mass ratio of cemented carbide balls with diameters of 4 mm and 8 mm was 2:3, and the mass ratio of balls to materials was 10:1, and the ball milling was carried out under a nitrogen protective atmosphere for 48 h; (4) Weigh 0.3% of the total mass of CNTs and place them in a beaker for purification. Add sufficient concentrated nitric acid to the beaker containing CNTs, ultrasonically vibrate for 30 minutes, then let it stand for 24 hours. Ultrasonicate for the second time for 3 hours, then let it stand for 24 hours. Ultrasonicate for the third time for 3 hours, then let it stand for 2 hours. (5) The purified CNTs were neutralized and cleaned using a centrifuge and then set aside. A Michael high-speed centrifuge was used with the centrifugation parameters set to a speed of 6500 r / min and a time of 5 min. The centrifugation was repeated 7 times until the pH value of the CNT suspension reached 7. The cleaning agent was distilled water. (6) Weigh the same mass of sodium dodecyl sulfate as that of CNTs and pour it into a beaker. Add 100 ml of anhydrous ethanol to the beaker to fully dissolve the sodium dodecyl sulfate by heating in a water bath. Add the neutralized CNTs to the beaker and vigorously stir and disperse them in an ultrasonic bath for 60 min. (7) Add the dispersed CNTs to the milled (W,Ti)C metal ceramic powder mixture and continue milling for 3 h. Dry the milled slurry in a vacuum at 120 °C for 36 h. (8) The dried mixed powder is put into the ball mill again for dry ball milling for 1 hour, and then passed through a 200-mesh sieve to obtain carbon nanotube-reinforced tungsten carbide titanium metal ceramic powder, which is sealed and set aside.

[0104] (9) The carbon nanotube reinforced tungsten carbide titanium metal ceramic powder was placed in a graphite mold and subjected to spark plasma coupled high-frequency induction sintering in a vacuum atmosphere. The sintering temperature was 1350℃, the sintering pressure was 35MPa, and the heating rate was as follows: preheating to 570℃ and heating to 600℃ within 1min; heating to 900℃ at 100℃ / min; heating to 1250℃ at 75℃ / min; heating to the target temperature at 50℃ / min, and holding time was 10min to obtain carbon nanotube reinforced tungsten carbide titanium metal ceramic material. The sintering current peak was 2653A, the average grain size was 3.8μm, and the relative density of the material was 99.1%. The obtained ceramic material sample was cut and processed, and its mechanical properties were measured as follows: flexural strength 1026MPa, fracture toughness 7.6MPa·m 1 / 2 , Vickers hardness 19.23GPa.

[0105] Example 4 In the embodiment, the average particle size of the (W, Ti) C powder is 1-3 μm, and the average particle size of the Ni, Mo, and Co powders is 1-1.5 μm, all of which are commercially available products. The polyethylene glycol is PEG6000.

[0106] The mass percentages of the components in the carbon nanotube-reinforced tungsten carbide titanium metal ceramic material are as follows: (W, Ti) C 84.6%, Ni 3.5%, Mo 6.5%, Co 5%, and CNTs 0.4%.

[0107] The preparation method of the carbon nanotube reinforced tungsten carbide titanium metal ceramic material comprises the following steps: (1) Place anhydrous ethanol in a beaker, weigh and add polyethylene glycol, place the beaker in a water bath, and stir magnetically at 65°C for 15 minutes until the polyethylene glycol is completely dissolved. Cool to room temperature to obtain a polyethylene glycol-anhydrous ethanol dispersion with a dispersion volume of 3 g / L. (2) Mix the powders of (W, Ti) C 84.6%, Ni 3.5%, Mo 6.5%, and Co 5% according to the mass percentage of each component, add them to the polyethylene glycol-anhydrous ethanol dispersion prepared in step (1), ultrasonically disperse for 60 minutes and mechanically stir to prepare a mixed solution; the mass of polyethylene glycol in the polyethylene glycol-anhydrous ethanol dispersion is 1% of the total mass of the (W, Ti) C, Ni, Mo, and Co powders; (3) The prepared mixed solution was placed in a ball mill, wherein the grinding balls used in the ball mill were cemented carbide grinding balls, the cemented carbide balls were mixed cemented carbide grinding balls with diameters of 4 mm and 8 mm, the mass ratio of cemented carbide balls with diameters of 4 mm and 8 mm was 2:3, and the mass ratio of balls to materials was 10:1, and the ball milling was carried out under a nitrogen protective atmosphere for 48 h; (4) Weigh 0.4% of the total mass of CNTs and place them in a beaker for purification. Add sufficient concentrated nitric acid to the beaker containing CNTs, ultrasonically vibrate for 30 minutes, then let it stand for 24 hours. Ultrasonicate for the second time for 3 hours, then let it stand for 24 hours. Ultrasonicate for the third time for 3 hours, then let it stand for 2 hours. (5) The purified CNTs were neutralized and cleaned using a centrifuge and then set aside. A Michael high-speed centrifuge was used with the centrifugation parameters set to a speed of 6500 r / min and a time of 5 min. The centrifugation was repeated 7 times until the pH value of the CNT suspension reached 7. The cleaning agent was distilled water. (6) Weigh the same mass of sodium dodecyl sulfate as that of CNTs and pour it into a beaker. Add 100 ml of anhydrous ethanol to the beaker to fully dissolve the sodium dodecyl sulfate by heating in a water bath. Add the neutralized CNTs to the beaker and vigorously stir and disperse them in an ultrasonic bath for 60 min. (7) Add the dispersed CNTs to the milled (W,Ti)C metal ceramic powder mixture and continue milling for 3 h. Dry the milled slurry in a vacuum at 120 °C for 36 h. (8) The dried mixed powder is put into the ball mill again for dry ball milling for 1 hour, and then passed through a 200-mesh sieve to obtain carbon nanotube-reinforced tungsten carbide titanium metal ceramic powder, which is sealed and set aside.

[0108] (9) The carbon nanotube reinforced tungsten carbide titanium metal ceramic powder was placed in a graphite mold and subjected to spark plasma coupled high-frequency induction sintering in a vacuum atmosphere. The sintering temperature was 1350℃, the sintering pressure was 35MPa, and the heating rate was as follows: preheating to 570℃ and heating to 600℃ within 1min; heating to 900℃ at 100℃ / min; heating to 1250℃ at 75℃ / min; heating to the target temperature at 50℃ / min, and holding time was 10min to obtain carbon nanotube reinforced tungsten carbide titanium metal ceramic material. The sintering current peak was 2636A, the average grain size was 4.4μm, and the relative density of the material was 98.9%. The obtained ceramic material sample was cut and processed, and its mechanical properties were measured as follows: flexural strength 996MPa, fracture toughness 7.8MPa·m 1 / 2 , Vickers hardness 18.86GPa.

[0109] Example 5 In the embodiment, the average particle size of the (W, Ti) C powder is 1-3 μm, and the average particle size of the Ni, Mo, and Co powders is 1-1.5 μm, all of which are commercially available products. The polyethylene glycol is PEG6000.

[0110] The mass percentages of the components in the carbon nanotube-reinforced tungsten carbide titanium metal ceramic material are as follows: (W, Ti) C 84.5%, Ni 3.5%, Mo 6.5%, Co 5%, and CNTs 0.5%.

[0111] The preparation method of the carbon nanotube reinforced tungsten carbide titanium metal ceramic material comprises the following steps: (1) Place anhydrous ethanol in a beaker, weigh and add polyethylene glycol, place the beaker in a water bath, and stir magnetically at 65°C for 15 minutes until the polyethylene glycol is completely dissolved. Cool to room temperature to obtain a polyethylene glycol-anhydrous ethanol dispersion with a dispersion volume of 3 g / L. (2) Mix the powders of (W, Ti) C 84.5%, Ni 3.5%, Mo 6.5%, and Co 5% according to the mass percentage of each component, add them to the polyethylene glycol-anhydrous ethanol dispersion prepared in step (1), ultrasonically disperse for 60 minutes and mechanically stir to prepare a mixed solution; the mass of polyethylene glycol in the polyethylene glycol-anhydrous ethanol dispersion is 1% of the total mass of the (W, Ti) C, Ni, Mo, and Co powders; (3) The prepared mixed solution was placed in a ball mill, wherein the grinding balls used in the ball mill were cemented carbide grinding balls, the cemented carbide balls were mixed cemented carbide grinding balls with diameters of 4 mm and 8 mm, the mass ratio of cemented carbide balls with diameters of 4 mm and 8 mm was 2:3, and the mass ratio of balls to materials was 10:1, and the ball milling was carried out under a nitrogen protective atmosphere for 48 h; (4) Weigh 0.5% of the total mass of CNTs and place them in a beaker for purification. Add sufficient concentrated nitric acid to the beaker containing CNTs, ultrasonically vibrate for 30 minutes, then let it stand for 24 hours. Ultrasonicate for the second time for 3 hours, then let it stand for 24 hours. Ultrasonicate for the third time for 3 hours, then let it stand for 2 hours. (5) The purified CNTs were neutralized and cleaned using a centrifuge and then set aside. A Michael high-speed centrifuge was used with the centrifugation parameters set to a speed of 6500 r / min and a time of 5 min. The centrifugation was repeated 7 times until the pH value of the CNT suspension reached 7. The cleaning agent was distilled water. (6) Weigh the same mass of sodium dodecyl sulfate as that of CNTs and pour it into a beaker. Add 100 ml of anhydrous ethanol to the beaker to fully dissolve the sodium dodecyl sulfate by heating in a water bath. Add the neutralized CNTs to the beaker and vigorously stir and disperse them in an ultrasonic bath for 60 min. (7) Add the dispersed CNTs to the milled (W,Ti)C metal ceramic powder mixture and continue milling for 3 h. Dry the milled slurry in a vacuum at 120 °C for 36 h. (8) The dried mixed powder is put into the ball mill again for dry ball milling for 1 hour, and then passed through a 200-mesh sieve to obtain carbon nanotube-reinforced tungsten carbide titanium metal ceramic powder, which is sealed and set aside.

[0112] (9) The carbon nanotube reinforced tungsten carbide titanium metal ceramic powder was placed in a graphite mold and subjected to spark plasma coupled high-frequency induction sintering in a vacuum atmosphere. The sintering temperature was 1350℃, the sintering pressure was 35MPa, and the heating rate was as follows: preheating to 570℃ and heating to 600℃ within 1min; heating to 900℃ at 100℃ / min; heating to 1250℃ at 75℃ / min; heating to the target temperature at 50℃ / min, and holding time was 10min to obtain carbon nanotube reinforced tungsten carbide titanium metal ceramic material. The sintering current peak was 2675A, the average grain size was 4.6μm, and the relative density of the material was 98.6%. The obtained ceramic material sample was cut and processed, and its mechanical properties were measured as follows: flexural strength 983MPa, fracture toughness 8.7MPa·m 1 / 2 , Vickers hardness 18.69GPa.

[0113] Comparative Example 1 This comparative example is the same as Example 2, except that the mass percentage in step (2) is (W,Ti)C 85%, Ni 3.5%, Mo 6.5%, and Co 5%. CNTs are not added to the tungsten carbide titanium metal ceramic powder. The other preparations are the same as Example 2. The sintering current peak is 2745A, the average grain size is 3.2μm, and the material relative density is 95.3%. At this time, the grains have not grown sufficiently and densification sintering has not been achieved. The obtained ceramic material sample was cut and processed, and its mechanical properties were measured as follows: flexural strength 532MPa, fracture toughness 5.6MPa·m 1 / 2 , Vickers hardness 12.76GPa.

[0114] Comparative Example 2 This comparative example is the same as Example 2, except that the sintering temperature in step (9) is set to 1400°C. The other preparation steps are the same as in Example 2. The average grain size is 7.2 μm, and the relative density is 96.2%. At this point, the grains have grown abnormally large and a large number of pores are present in the cross section of the material. The obtained ceramic material sample was cut and its mechanical properties were measured as follows: flexural strength 764 MPa, fracture toughness 6.7 MPa·m 1 / 2 , Vickers hardness 16.26GPa.

[0115] Comparative Example 3 This comparative example is the same as Example 2, except that the dry ball milling in step (8) is not performed and the sample is directly sieved out. The other preparations are the same as Example 2. The obtained ceramic material sample is cut and processed, and its mechanical properties are measured as follows: flexural strength 938MPa, fracture toughness 7.2MPa·m 1 / 2 , Vickers hardness 18.34GPa. Average grain size 4.9μm.

[0116] Comparative Example 4 This comparative example is the same as Example 2, except that the spark plasma coupled high frequency induction sintering is not used in step (9), and only the spark plasma sintering is used. The other preparations are the same as those in Example 2. The obtained ceramic material sample is cut and processed, and its mechanical properties are measured as follows: flexural strength 823 MPa, fracture toughness 6.9 MPa·m 1 / 2 , Vickers hardness 15.47GPa. Average grain size 4.8μm.

[0117] Comparative Example 5 This comparative example is the same as Example 2, except that the mass percentage content in step (2) is (W,Ti)C 85%, Ni 3.5%, Mo 6.5%, and Co 5%, CNTs are not added to the tungsten carbide titanium metal ceramic powder, and the sintering temperature in step (9) is changed to 1450°C. The other preparations are the same as in Example 2.

[0118] The sintering current peak was 2857A, the average grain size was 5.8μm, and the relative density of the material was 99.1%. At this time, the grains were fully grown and densified sintering was achieved. The obtained ceramic material samples were cut and processed, and their mechanical properties were measured as follows: flexural strength 869MPa, fracture toughness 7.0MPa·m 1 / 2 , Vickers hardness 19.63GPa.

[0119] Comparison of Example 2 with Examples 1-5 and Comparative Example 1 shows that the added content of CNTs has a significant impact on the discharge environment during the sintering process, thereby affecting the mechanical properties of the material.

[0120] From the comparison between Example 2 and Comparative Example 2, it can be seen that the addition of CNTs reduces the sintering temperature and achieves reduced energy consumption.

[0121] From the comparison between Example 2 and Comparative Example 3, it can be seen that the dry ball milling and re-ball milling method improves the dispersion effect of CNTs and enhances the mechanical properties of the material.

[0122] From the comparison between Example 2 and Comparative Example 4, it can be seen that spark plasma coupled high-frequency induction sintering has a great impact on improving the sintering environment of CNTs.

[0123] Comparison of Example 2 with Comparative Examples 1 and 5 shows that, when preparing ceramic materials without CNTs, densification sintering at only 1350°C is not possible; a higher temperature (1450°C) is required. Furthermore, the resulting mechanical properties and electrical conductivity are inferior to those of the present invention. The present invention utilizes spark plasma-coupled high-frequency induction sintering, leveraging the excellent electrical conductivity of carbon nanotubes to improve the discharge environment. Densification sintering is achieved at 1350°C, reducing the sintering temperature by 100°C, lowering energy loss and sintering current peaks, significantly lowering production costs, and further improving mechanical properties and electrical conductivity.

[0124] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A carbon nanotube reinforced tungsten carbide titanium metal ceramic material, characterized in that: It includes a matrix, a metal bonding phase and a reinforcement phase, wherein the matrix is ​​(W, Ti) C, the reinforcement phase is CNTs, and the metal bonding phase is Ni, Mo, and Co; The mass percentage of each component is: (W, Ti) C 84.5-85%, Ni 3-4%, Mo 6-7%, Co 4.5-5.5%, CNTs 0-0.5%, and the sum of the mass of each component is 100%.

2. The carbon nanotube reinforced tungsten carbide titanium metal ceramic material according to claim 1, characterized in that: The mass percentage of each component is: (W, Ti) C 84.5-85%, Ni 3-4%, Mo 6-7%, Co 4.5-5.5%, CNTs 0.01-0.5%, and the sum of the mass of each component is 100%.

3. The carbon nanotube reinforced tungsten carbide titanium metal ceramic material according to claim 2, characterized in that: The mass percentage of each component is: (W, Ti) C 84.5-85%, Ni 3-4%, Mo 6-7%, Co 4.5-5.5%, CNTs 0.1-0.5%, and the sum of the mass of each component is 100%; The average particle size of (W,Ti)C powder is 1~3μm; The average particle size of Ni powder, Mo powder, and Co powder is 1~1.5μm; The average grain size of carbon nanotube reinforced tungsten carbide titanium metal ceramic material is 3.5~5μm.

4. A method for preparing the carbon nanotube reinforced tungsten carbide titanium metal ceramic material according to any one of claims 1 to 3, characterized in that: The following steps are involved: (W, Ti) C powder, Ni powder, Mo powder, and Co powder are mixed according to a mass ratio and dispersed in a polyethylene glycol-anhydrous ethanol dispersion. The obtained (W, Ti) C metal ceramic mixed powder is subjected to a first ball milling treatment; The purified and neutralized CNTs are dispersed and added to the (W,Ti)C metal ceramic mixed powder after the first ball milling, and then subjected to a second ball milling process and dried. The dried mixed powder is subjected to a third ball milling process to obtain a mixed powder, and the mixed powder is subjected to spark plasma coupled high frequency induction sintering to obtain the obtained product.

5. The preparation method according to claim 4, characterized in that Adding polyethylene glycol to anhydrous ethanol, stirring in a water bath at a constant temperature, and cooling to room temperature to prepare a polyethylene glycol-anhydrous ethanol dispersion; The water bath is kept at a constant temperature of 60-70° C., magnetic stirring is used for stirring, and the stirring time is 15-20 min. In the polyethylene glycol-anhydrous ethanol dispersion, the dispersion amount of polyethylene glycol is 3-5 g / L. The mass of the polyethylene glycol in the polyethylene glycol-anhydrous ethanol dispersion is 0.5% to 1.5% of the total mass of the (W,Ti)C powder, the Ni powder, the Mo powder, and the Co powder; The first ball milling process is as follows: the weight ratio of the total amount of raw materials to the grinding balls is 1: (8-15), and the ball milling time is 24-72 hours under a protective atmosphere; The protective atmosphere during the ball milling process was nitrogen, and the grinding balls used in the ball milling were cemented carbide grinding balls; the cemented carbide balls were mixed cemented carbide grinding balls with diameters of 4 mm and 8 mm, and the mass ratio of the cemented carbide balls with diameters of 4 mm to 8 mm was (2-2.5):(3-3.5); In the second ball milling process, the ball milling time is 2 to 4 hours; The third ball milling process is dry ball milling, and the ball milling time is 0.5 to 1.5 hours.

6. The preparation method according to claim 4, characterized in that The purification process of CNTs is as follows: CNTs are mixed with concentrated nitric acid, ultrasonically shaken for 20-40 minutes, and then allowed to stand for 12-36 hours. The second ultrasonic shaken for 1-5 hours, and then allowed to stand for 12-36 hours. The third ultrasonic shaken for 1-5 hours, and then allowed to stand for 0.5-3 hours. Wherein, 25~35wt% concentrated nitric acid is used; After the purification treatment, neutralization and washing are performed to obtain neutralized CNTs. During the neutralization and washing process, the centrifugation parameters are set to a speed of 6000-7000 rpm and a time of 4-6 minutes. The centrifugation is repeated 5-8 times until the pH value of the CNT suspension reaches 6.8-7.

2. Sodium lauryl sulfate is dissolved in anhydrous ethanol, heated in a water bath to fully dissolve the sodium lauryl sulfate, and then neutralized CNTs are added, and vigorously stirred and dispersed in an ultrasonic bath for 0.5 to 2 hours to obtain dispersed CNTs; wherein, during the dispersion of the CNTs, the mass ratio of the sodium lauryl sulfate to the CNTs is (0.9 to 1.1):(0.9 to 1.1).

7. The preparation method according to claim 4, characterized in that Placing the mixed powder in a graphite mold, and performing spark plasma coupled high-frequency induction sintering in a vacuum atmosphere to prepare a carbon nanotube reinforced tungsten carbide titanium metal ceramic material; In spark plasma coupled high frequency induction sintering, the sintering temperature is 1300℃~1400℃, and the sintering pressure is 30~40MPa. The specific heating rates include: preheating to 560~580℃ and heating to 590~610℃ within 1 minute; heating to 890~910℃ at 90~110℃ / min; heating to 1240~1260℃ at 70~80℃ / min; heating to the target temperature at 45~55℃ / min, and keeping warm for 5~15 minutes.

8. The preparation method according to claim 7, characterized in that The sintering temperature is 1300~1380℃; the sintering pressure is 34~36MPa; and the holding time is 8~12min.

9. Use of the carbon nanotube-reinforced tungsten carbide titanium metal ceramic material according to any one of claims 1 to 3 or the carbon nanotube-reinforced tungsten carbide titanium metal ceramic material obtained by the preparation method according to any one of claims 4 to 8 in the preparation of ceramic tools and electric discharge machining electrodes.

10. A metal ceramic tool, characterized in that: The invention comprises the carbon nanotube reinforced tungsten carbide titanium metal ceramic material according to any one of claims 1 to 3 or the carbon nanotube reinforced tungsten carbide titanium metal ceramic material obtained by the preparation method according to any one of claims 4 to 8.

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