A carbon nanotube-reinforced tungsten carbide titanium cermet material, its preparation method and application

Abstract

This invention discloses a carbon nanotube-reinforced tungsten carbide titanium cermet material, its preparation method, and its applications, belonging to the field of cermet materials. This invention employs a spark-plasma coupled high-frequency induction sintering method, using a method of re-dry ball milling to disperse CNTs uniformly in the material matrix. During sintering, the uniformly dispersed CNTs improve the discharge environment, reduce sintering current, and decrease energy consumption under the high-frequency induction effect of spark-plasma coupling. Utilizing the complementary effect of the ultra-high conductivity of (W,Ti)C cermet material and CNTs, a highly densified, high-strength, and highly wear-resistant (W,Ti)C-based cermet material is prepared at a sintering temperature of 1350℃.

Description

Technical Field

[0001] This invention belongs to the field of metal ceramic materials, specifically relating to a carbon nanotube-reinforced tungsten carbide titanium metal ceramic material, its preparation method, and its application. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] In the field of mechanical manufacturing, a high-quality cutting tool is particularly important due to the need for machining. Ceramic materials have the advantages of high hardness and high heat resistance, but their relatively low strength and toughness are the main reasons limiting their widespread application. Among cermet composites, (W,Ti)C-based cermet cutting tools have 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 an ideal material for manufacturing high-performance cutting tools.

[0004] Current research indicates that there are numerous studies on (W,Ti)C-based cermet materials. Existing technologies include spark plasma sintering at 1500℃; self-propagating combustion synthesis at 1600℃; and pressureless sintering at 1450℃. However, these sintering methods rely heavily on Joule heating to achieve densification, resulting in significant energy consumption and room for improvement in mechanical properties. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a carbon nanotube-reinforced tungsten carbide titanium cermet material, its preparation method, and its applications. This invention employs a spark-plasma coupled high-frequency induction sintering method, using a secondary dry ball milling method to uniformly disperse CNTs within the material matrix. During sintering, the uniformly dispersed CNTs, under the influence of spark-plasma coupled high-frequency induction, improve the discharge environment, reduce sintering current, and decrease energy consumption. Utilizing the complementary effect of the ultra-high conductivity of (W,Ti)C cermet material 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℃.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows:

[0007] In a first aspect, the present invention provides a carbon nanotube-reinforced tungsten carbide titanium cermet material (CNTs-(W,Ti)C), comprising a matrix, a metal binder phase, and a reinforcing phase, wherein the matrix is ​​(W,Ti)C, the reinforcing phase is carbon nanotubes (CNTs), and the metal binder phase is Ni, Mo, or Co;

[0008] The mass percentage of each component is as follows: (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 masses of each component is 100%.

[0009] This invention uses (W,Ti)C ceramic as the matrix, adds Ni, Mo, and Co as metallic phases, and CNTs as reinforcing phases, and is fabricated by high-frequency induction sintering via spark plasma coupling. By utilizing the good conductivity of carbon nanotubes, the discharge environment is improved, and the material is densified by sintering.

[0010] Secondly, the present invention provides a method for preparing the above-mentioned carbon nanotube-reinforced tungsten carbide titanium cermet material, comprising the following steps:

[0011] (W,Ti)C powder, Ni powder, Mo powder and Co powder are mixed in a mass ratio and dispersed in a polyethylene glycol-anhydrous ethanol dispersion. The resulting (W,Ti)C cermet mixed powder is then subjected to a first ball milling process.

[0012] The acidified and purified CNTs were dispersed, and the dispersed CNTs were added to the (W,Ti)C cermet mixed powder that had been ball-milled in the first ball milling process, and then ball-milled again and dried.

[0013] The dried mixed powder is subjected to a third ball milling process to obtain a mixed powder body, which is then subjected to discharge plasma coupling high-frequency induction sintering to obtain the final product.

[0014] Thirdly, the present invention provides the application of the above-mentioned carbon nanotube-reinforced tungsten carbide titanium cermet material in the preparation of ceramic cutting tools and electrical discharge machining electrodes.

[0015] Fourthly, the present invention provides a metal-ceramic cutting tool, comprising the above-mentioned carbon nanotube-reinforced tungsten carbide titanium metal-ceramic material.

[0016] One or more of the above technical solutions have the following advantages or beneficial effects:

[0017] (1) This invention discloses a carbon nanotube-reinforced tungsten carbide titanium cermet material, using (W,Ti)C ceramic as the matrix, CNTs with high conductivity as the reinforcing phase, and adding Ni, Mo, and Co as the metal binder phase. The addition of carbon nanotubes enables the carbon nanotube-reinforced tungsten carbide titanium cermet material to not only have excellent mechanical properties but also excellent electrical conductivity, thereby also achieving a reduction in sintering temperature.

[0018] (2) This invention employs discharge plasma coupling high-frequency induction sintering. The preparation method involves first wet ball milling (W,Ti)C, Ni, Mo, and Co, followed by adding dispersed CNTs for a second wet ball milling, drying, and then a third dry ball milling to obtain a mixed powder. This powder is then subjected to discharge plasma coupling high-frequency induction sintering. This method improves the dispersion of CNTs and utilizes the discharge sintering effect of highly conductive CNTs, reducing the current intensity required for (W,Ti)C cermet cutting tool materials. Sintering is completed at a lower sintering temperature, significantly increasing density and refining grains, thereby improving the mechanical properties of the material. This method offers advantages such as reduced energy consumption and cost savings.

[0019] (3) The (W,Ti)C cermet cutting tool prepared by the present invention has higher toughness and hardness as well as excellent friction reduction and wear resistance, and can be applied to the field of high-speed and high-efficiency cutting.

[0020] (4) The present invention employs a dry ball milling method to further disperse CNTs, thereby uniformly dispersing CNTs in (W,Ti)C-based cermet powder. Through dispersion treatment, CNTs are well dispersed in the cermet material. During the discharge plasma coupling high-frequency induction sintering process, CNTs form a continuous conductive network along the grain boundaries, reducing the contact resistance between powder particles by 1 to 2 orders of magnitude. This makes it easier for pulse current to generate Joule heating and spark discharge between particles, thereby reducing the breakdown voltage.

[0021] (5) Compared with the existing method of achieving material densification sintering at 1450℃, the present invention adopts high-frequency induction sintering with discharge plasma coupling. By adding carbon nanotubes, the good conductivity of carbon nanotubes is used to improve the discharge environment, and material densification sintering is completed at 1350℃. This reduces the sintering temperature by 100℃, reduces energy loss, and reduces the peak sintering current by 143A, greatly reducing production costs.

[0022] (6) This invention provides a method for preparing a carbon nanotube-reinforced tungsten carbide titanium cermet material with better overall mechanical properties. The parameters of the obtained cermet material sample are as follows: average grain size 3.8~4.6μm, relative density 98.6~99.4%, flexural strength 983~1127MPa, and fracture toughness 7.3~8.7MPa·m. 1 / 2Hardness 18.69~19.83GPa. Attached Figure Description

[0023] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0024] Figure 1 This illustrates the dispersion of CNTs in the metal-ceramic powder after dry ball milling in an embodiment of the present invention.

[0025] Figure 2 The sintering current curves during the discharge plasma coupling high-frequency induction sintering process in Comparative Example 1 and Example 2 of this invention are shown.

[0026] Figure 3 This is a cross-sectional morphology image of the carbon nanotube-reinforced tungsten carbide titanium cermet material prepared in Example 2 of the present invention;

[0027] Figure 4 These are topographic images of Comparative Examples 1 to 5 of the present invention; wherein, (a) is a topographic image of Comparative Example 1, (b) is a topographic image of Comparative Example 2, (c) is a topographic image of Comparative Example 3, (d) is a topographic image of Comparative Example 4, and (e) is a topographic image of Comparative Example 5.

[0028] Figure 5 The image shows the elemental analysis of the polished surface cracks and their propagation in the material prepared in Example 2 of this invention; wherein, (a) is a morphology image of the polished surface cracks, and (b) is an elemental analysis image of the propagation of the polished surface cracks. Detailed Implementation

[0029] In this invention, unless otherwise specified, all other test materials and instruments are conventional test materials in the field and can be purchased through commercial channels.

[0030] In this invention, "+" means "and".

[0031] The following standards are used for testing the materials:

[0032] Bending strength: Three-point bending test, ASTM C1161 / ISO 14705.

[0033] Fracture toughness: Indentation method, IF method, ISO 28079.

[0034] Vickers hardness: Vickers indentation method, ASTM E384 / ISO 6507-1, wherein Vickers hardness is measured under a load of 196N.

[0035] Due to the shortcomings of existing technologies, there is an urgent need to develop a method for preparing (W,Ti)C-based cermet materials with low energy consumption and excellent mechanical properties. This invention uses (W,Ti)C ceramic as the matrix, adds Ni, Mo, and Co as metallic phases, and CNTs as reinforcing phases, and prepares the material through high-frequency induction sintering via spark plasma coupling. The excellent conductivity of carbon nanotubes is utilized to improve the discharge environment, thereby achieving material densification through sintering.

[0036] Carbon nanotubes (CNTs) are seamless microtubes formed by the tubular arrangement and coiling of carbon atoms. They are classified into single-walled and multi-walled carbon nanotubes based on the number of carbon atom layers. All carbon atoms in CNTs are sp. 2 They are formed by hybridization, bonded together by C-C bonds, thus possessing high hardness, high modulus, and high strength. Furthermore, carbon nanotubes (CNTs) exhibit one-dimensional quantum confinement effect and sp... 2 The ultra-high current density (>10) imparted by the hybrid carbon network 9 A cm -2 With ballistic transport lengths (micrometers), it can serve as an ideal alternative material to overcome the "electromigration bottleneck" of traditional copper interconnects.

[0037] (W,Ti)C cermet materials possess superior electrical conductivity (far exceeding that of Ti(C,N)-based cermet materials). Under spark plasma coupled high-frequency induction sintering, the conductivity of (W,Ti)C cermet materials and CNTs is not simply superimposed, but rather exhibits a "complementary-synergistic-amplified" coupling relationship, producing a complementary "ultra-high conductivity" effect. This forms a synergistic loop of low-resistance pathway, high thermal bridge, and uniform temperature field. Utilizing the high conductivity of CNTs reduces the current intensity required for sintering (W,Ti)C-based cermets, allowing sintering to be completed at a lower temperature and suppressing grain growth. According to the Hall-Petch relationship, grain refinement is beneficial for improving mechanical properties. Therefore, the mechanical properties of (W,Ti)C cermet tool materials are significantly improved. This is a result of the complementary ultra-high conductivity of the two materials, which cannot be achieved by a single conductive phase.

[0038] The technical effects of adding carbon nanotubes vary depending on the matrix. Adding carbon nanotubes to a Ti(C,N) matrix does not simultaneously achieve all the technical effects of this invention. The specific reasons are as follows:

[0039] (1) The wetting angle of (W,Ti)C with the metal binder phase (Co / Ni / Mo) is slightly smaller than that of Ti(C,N), and CNTs are more easily encapsulated by the liquid phase, resulting in higher grain boundary pinning efficiency. Ti(C,N) is prone to denitrification reaction during heating, and CNTs mainly inhibit denitrification pores. However, (W,Ti)C does not have denitrification problems, and CNTs are more focused on inhibiting the re-precipitation and growth of WC. Therefore, the matrix and the mechanism of action of carbon nanotubes are different, and the grain refinement range of the present invention is greater.

[0040] (2) Diffusion activation energy: W solid solution increases the diffusion activation energy of the matrix. The "rapid thermal-electrical 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 results in a greater decrease in sintering temperature, while the change is not obvious when added to the Ti(C,N) matrix.

[0041] (3) The conductivity of (W,Ti)C cermets is 1 to 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 "medium conductivity" category, and their resistance needs to be further reduced by increasing the content of the metal binder phase or adding a third phase. Therefore, the addition of high conductivity CNTs has a more significant effect on reducing the peak sintering current of high conductivity (W,Ti)C cermets, but for low conductivity Ti(C,N), it cannot achieve a "complementary-synergistic-amplification" coupling relationship and cannot produce a "super high conductivity" complementary effect.

[0042] In summary, this invention uses (W,Ti)C cermet as the matrix and incorporates CNTs, which can effectively utilize the high conductivity of the (W,Ti)C matrix and the high conductivity of CNTs to achieve a synergistic effect in spark plasma coupling high-frequency induction sintering. This results in reduced peak sintering current, lower sintering temperature, and refined grain size, ultimately achieving the goals of reducing energy consumption and production costs.

[0043] This invention utilizes the discharge effect of carbon nanotubes to form a system of "CNTs conductive-thermal bridge + rapid Joule thermal spike + traditional liquid phase". By utilizing the one-dimensional quantum transport of CNTs, "low-temperature rapid burning" is achieved, and the resulting material has integrated mechanical and electrical properties. This invention relies on "one-dimensional enhancement of CNTs + electric field-thermal field coupling".

[0044] In a first embodiment, the present invention provides a carbon nanotube-reinforced tungsten carbide titanium cermet material (CNTs-(W,Ti)C), comprising a matrix, a metal binder phase, and a reinforcing phase, wherein the matrix is ​​(W,Ti)C, the reinforcing 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%.

[0045] To achieve even better technical results, the mass percentage of each component is as follows: (W,Ti)C 84.5~85%, Ni 3~4%, Mo 6~7%, Co 4.5~5.5%, CNTs 0.01~0.5%, with the sum of the masses of all components being 100%. Further, the mass percentage of each component is as follows: (W,Ti)C 84.5~85%, Ni 3~4%, Mo 6~7%, Co 4.5~5.5%, CNTs 0.1~0.5%, with the sum of the masses of all components being 100%.

[0046] The specific addition amount of CNTs 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 CNT content is 0.1% to 0.3%. When the addition amount of CNTs is too low, the CNTs cannot form an effective reinforcing framework, resulting in limited improvement in conductivity and performance. When the addition amount of CNTs is too high, agglomeration leads to a decrease in density and interfacial bonding, resulting in a comprehensive deterioration of mechanical and functional properties.

[0047] 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.

[0048] Carbon nanotubes (CNTs) are not specifically limited in their composition. Multi-walled or single-walled CNTs can be selected, with multi-walled CNTs being preferred. Typical diameters range from 7 to 30 nm, and lengths from 5 to 20 µm. This is because the 7–30 nm diameter and (W,Ti)C particles (2–2.5 µm) create 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 exhibit higher rigidity and fewer defects, maintaining structural integrity under instantaneous high pressure during SPS (Supersonic Polarization). Furthermore, their multi-walled structure provides additional conductive and thermal pathways, resulting in more uniform local current and Joule heat distribution.

[0049] The average grain size of the carbon nanotube-reinforced tungsten carbide titanium cermet material is 3.5~5μm, preferably 3.8~4.6μm, and the relative density of the material is greater than 98%, preferably greater than 98.5%, and more preferably 99%. For example, it can be 98~99.5%.

[0050] In this invention, Ni powder, Mo powder, and Co powder are used as the metal binder phase. Their role in the SPS-HF (spark plasma coupled high-frequency induction sintering) sintered CNTs-(W,Ti)C system is "liquid phase formation + interface wetting + carbon activity buffering". The three elements Ni, Mo, and Co are not arbitrarily combined, but each plays a specific role; any addition or subtraction will significantly change the final microstructure and properties through three pathways: liquidus temperature, wetting angle, and carbon activity.

[0051] (1) The “division of labor” of existing ternary binder phases

[0052] Co (main binder phase): forms a low-melting eutectic with (W,Ti)C (≈1280℃), providing a highly fluid liquid phase to ensure rapid densification; it has a wetting angle of 25~30° for CNTs and is the core for forming a continuous metal network.

[0053] Ni (auxiliary wetting): lowers the liquidus temperature by 20-30°C, improves the chemical affinity for CNTs, and reduces CNT aggregation; at the same time, it forms an unlimited solid solution with Co, inhibiting the precipitation of brittle η phase.

[0054] 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%.

[0055] (2) The effect of omitting a certain element

[0056] Removing Co raises the liquidus temperature to above 1380℃, requiring the SPS temperature to be increased from 1450℃ to 1500℃, resulting in a 30% coarsening of the grains and a 25% decrease in toughness.

[0057] Alternatively, removing Ni increases the liquid phase wetting angle to 45°, causing significant aggregation of CNTs, discontinuous conductive networks, and an increase in resistivity by one order of magnitude.

[0058] Alternatively, removing Mo: the activity of free carbon increases, and CNTs begin to be eroded by the liquid phase at 1350℃, resulting in a 12% decrease in hardness and a 2% increase in porosity.

[0059] (3) The effect of introducing a fourth type of metal powder

[0060] Adding a small amount of Fe (≤3wt%): the liquidus temperature drops by another 15℃, which can further refine the grains. However, if the amount is >3wt%, a brittle (Fe,Co)7W6 phase is easily formed, and the toughness drops sharply.

[0061] Alternatively, adding Cr can improve antioxidant properties but reduce wettability. Therefore, the sintering temperature needs to be increased by 20-30°C to offset the refining effect.

[0062] Alternatively, adding Cu: the liquid phase wetting angle drops sharply to 15°, but the interfacial reaction between Cu and CNTs is weak, resulting in poor interfacial bonding and a 18% decrease in flexural strength.

[0063] Alternatively, Al powder can be added: Al reacts weakly with CNTs at the interface, forming a brittle Al4C3 phase, which reduces the bending strength by about 18%; when Al > 3wt%, the continuous Al4C3 at the grain boundaries causes cracks to propagate along the grain, resulting in a sharp drop in toughness.

[0064] Alternatively, Ti powder can be added: Ti reacts with CNTs to form a TiC coating layer, which protects the CNTs but causes them to lose their electrical / thermal bridging function, resulting in a 2-fold increase in resistivity. Although the (W,Ti)C matrix contains Ti, it is a carbide and will not react with CNTs. When Ti > 2 wt%, the TiC coating layer is too thick, which hinders liquid phase penetration and causes a 3% decrease in density.

[0065] 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 will significantly deteriorate the densification temperature, CNT integrity, or mechanical properties. If a fourth metal is introduced, it must be controlled within the range of 1-3 wt% and the interfacial reaction must be verified; otherwise, the overall gain will be offset by the brittle phase or wettability imbalance.

[0066] In a second embodiment, the present invention provides a method for preparing the above-mentioned carbon nanotube-reinforced tungsten carbide titanium metal ceramic material, comprising the following steps:

[0067] (W,Ti)C powder, Ni powder, Mo powder and Co powder are mixed in a mass ratio and dispersed in a polyethylene glycol-anhydrous ethanol dispersion. The resulting (W,Ti)C cermet mixed powder is then subjected to a first ball milling process.

[0068] The purified and neutralized CNTs were dispersed, and the dispersed CNTs were added to the (W,Ti)C cermet mixed powder that had been ball-milled in the first ball milling process. The powder was then ball-milled a second time and dried.

[0069] The dried mixed powder is subjected to a third ball milling process to obtain a mixed powder body, which is then subjected to discharge plasma coupling high-frequency induction sintering to obtain the final product.

[0070] In one or more embodiments, polyethylene glycol is added to anhydrous ethanol and stirred in a water bath at a constant temperature, then cooled to room temperature to obtain a polyethylene glycol-anhydrous ethanol dispersion. The water bath temperature is 60-70°C, and magnetic stirring is used for 15-20 minutes. The amount of polyethylene glycol dispersed in the polyethylene glycol-anhydrous ethanol dispersion is 3-5 g / L.

[0071] The mass of polyethylene glycol in the polyethylene glycol-anhydrous ethanol dispersion is 0.5% to 1.5% of the sum of the masses of (W,Ti)C powder, Ni powder, Mo powder, and Co powder. Specifically, it 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%.

[0072] The molecular weight of polyethylene glycol is 5000~7000, preferably PEG6000.

[0073] (W,Ti)C powder, Ni powder, Mo powder, and Co powder are mixed and added to a prepared polyethylene glycol-anhydrous ethanol dispersion. The mixture is then ultrasonically dispersed and stirred to obtain a (W,Ti)C cermet mixed powder. The ultrasonic dispersion time is 45-60 minutes, and mechanical stirring is used to ensure thorough dispersion.

[0074] In one or more embodiments, the first ball milling process is as follows: the total amount of raw materials ((W,Ti)C powder, Ni powder, Mo powder, Co powder) to the weight ratio of grinding balls is 1:(8~15), and ball milling is carried out for 24~72 hours under a protective atmosphere; preferably, the ball milling time is 40~60 hours (preferably 44~47 hours). The first ball milling process is wet ball milling.

[0075] The protective atmosphere during the ball milling process is nitrogen, and the grinding balls used are cemented carbide grinding balls. The cemented carbide balls are a mixture of 4mm and 8mm diameter cemented carbide grinding balls, with a mass ratio of 4mm to 8mm diameter cemented carbide balls of (2~2.5):(3~3.5). The ball-to-material mass ratio is (10~15):1.

[0076] In one or more embodiments, the purification (acidification) treatment of CNTs is as follows: CNTs are mixed with sufficient concentrated nitric acid, ultrasonically vibrated for 20-40 min and then allowed to stand for 12-36 h (preferably 20-30 h), ultrasonically vibrated a second time for 1-5 h (preferably 2-4 h) and then allowed to stand for 12-36 h (preferably 20-30 h), ultrasonically vibrated a third time for 1-5 h (preferably 2-4 h) and then allowed to stand for 0.5-3 h (preferably 1.5-2.5 h).

[0077] Use 25-35 wt% analytical grade concentrated nitric acid. There is no specific limit to the amount of concentrated nitric acid used, as long as it can fully disperse the nitric acid. For example, if 0.05-0.15 g of CNTs can be dispersed in one go, use 150-200 ml of concentrated nitric acid.

[0078] After purification (acidification), neutralization and washing are performed to obtain neutralized CNTs. During the neutralization and washing process, the centrifugation parameters are set as follows: speed 6000-7000 r / min, preferably 6500 r / min; time 4-6 min, preferably 5 min; repeat centrifugation 5-8 times until the pH of the CNTs suspension reaches 6.8-7.2. The washing agent is distilled water.

[0079] In one or more embodiments, sodium dodecyl sulfate is dissolved in anhydrous ethanol, and the sodium dodecyl sulfate is fully dissolved by heating in a water bath. Then, 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.

[0080] Furthermore, during the dispersion of CNTs, the mass ratio of sodium dodecyl sulfate to CNTs is (0.9~1.1):(0.9~1.1), preferably 1:1.

[0081] Furthermore, there are no specific limitations on the temperature and time of water bath heating; existing conventional parameters can be used as long as they allow sodium dodecyl sulfate to dissolve completely.

[0082] In one or more embodiments, the second ball milling process is performed for a time of 2-4 hours (preferably 2.5-3.5 hours). The second ball milling process is wet ball milling.

[0083] For example, the process could be as follows: during the two wet ball milling processes, the metal-ceramic matrix is ​​ball milled for a total of 48 hours. At the 45-hour mark of the ball milling process, the dispersed CNTs are added, and the remaining 3 hours of ball milling are completed.

[0084] In one or more embodiments, the dried mixed powder is subjected to a third ball milling process, which can be performed by vacuum drying at a temperature of 115~125°C for 36~48 hours, preferably 42 hours.

[0085] In one or more embodiments, the third ball milling process is dry ball milling, with a milling time of 0.5 to 1.5 hours. After dry ball milling, the powder is sieved with a screen of 100 to 300 mesh, preferably 200 mesh. This dry ball milling method further disperses the CNTs, ensuring that the CNTs are uniformly dispersed in the (W,Ti)C-based cermet powder.

[0086] In one or more embodiments, the mixed powder is placed in a graphite mold and subjected to high-frequency induction sintering via discharge plasma coupling under a vacuum atmosphere to obtain a carbon nanotube-reinforced tungsten carbide titanium metal ceramic material.

[0087] In spark plasma coupled high-frequency induction sintering, the sintering temperature is 1300℃~1400℃, specifically 1300℃, 1310℃, 1320℃, 1330℃, 1340℃, 1350℃, 1360℃, 1370℃, 1380℃, 1390℃, 1400℃, etc., preferably 1300~1380℃, further preferably 1320~1380℃, and most preferably 1350℃. Too low a temperature will prevent sintering, while too high a temperature will cause abnormal grain growth and a large number of pores in the material cross-section.

[0088] In spark plasma coupled high-frequency induction sintering, the sintering pressure is 30~40MPa, specifically 30MPa, 32MPa, 33MPa, 34MPa, 35MPa, 36MPa, 37MPa, 38MPa, 40, etc., preferably 34~36MPa.

[0089] In spark plasma coupled high-frequency induction sintering, the specific heating rates include: preheating to 560~580℃ (e.g., 570℃), and then heating to 590~610℃ (e.g., 600℃) within 1 minute; heating to 890~910℃ (e.g., 900℃) at 90~110℃ / min (e.g., 100℃ / min); heating to 1240~1260℃ (e.g., 1250℃) at 70~80℃ / min (e.g., 75℃ / min); and heating to the target temperature at 45~55℃ / min (e.g., 50℃ / min), with a holding time of 5~15 minutes (e.g., 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 minutes, preferably 8~12 minutes).

[0090] Before the addition of carbon nanotubes, the peak sintering current is above 2700A, such as 2745A in Comparative Example 1. After the addition of carbon nanotubes, the peak sintering current is below 2700A, specifically 2684A, 2620A, 2653A, 2636A, 2675A, etc., preferably 2600~2690A, and more preferably 2620~2685A.

[0091] In the preparation of carbon nanotube-reinforced tungsten-titanium carbide cermet materials according to this invention, a spark plasma coupling high-frequency induction sintering process is required. If a cold pressing followed by vacuum hot pressing sintering is used, the technical effects of this invention cannot be achieved. The specific reasons are as follows:

[0092] (1) Firstly, a key point of this invention is to utilize the high conductivity of CNTs to reduce the sintering current through discharge plasma coupling high-frequency induction sintering (SPS-HF), thereby reducing the sintering temperature, energy consumption, and production costs. However, the method of cold pressing followed by vacuum hot pressing sintering does not involve an electric field and cannot utilize the high conductivity of CNTs.

[0093] The pulsed DC current of SPS-HF generates instantaneous Joule heating and micro-plasma at the CNTs-(W,Ti)C interface, raising the local temperature by 200-300°C within <60s. This causes the CNTs to straighten and embed into the particle surface, forming a low-resistivity conductive network. In contrast, vacuum hot pressing relies solely on external radiation heating, with a heating rate ≤15°C / min. In this case, the CNTs loosen and aggregate in the 800-1200°C range, losing their one-dimensional orientation and leading to the breakage of subsequent conductive / thermal bridges.

[0094] (2) The constant pressure environment and other factors: Discharge plasma coupling high frequency induction sintering is completed under constant pressure environment. The growth of grains can be significantly suppressed by constant pressure. However, the method of cold pressing and then vacuum hot pressing sintering does not have a 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.

[0095] SPS-HF achieves densification simultaneously with 35MPa uniaxial pressure and 10 min of heat treatment, suppressing WC re-precipitation and refining grains. In contrast, vacuum hot pressing requires 30-60 min to achieve the same density, and the prolonged high temperature promotes WC growth.

[0096] (3) Rapid sintering by discharge plasma coupling high frequency induction sintering can achieve rapid heating of materials to achieve rapid densification of materials, and ensure the integrity of CNTs to achieve densification sintering.

[0097] Rapid densification by SPS-HF (5-15 min in total) "locks" oxygen and nitrogen impurities outside the grain boundaries, keeping the carbon layer on the CNT surface intact. However, prolonged exposure during vacuum hot pressing (>30 min) causes CNTs to react with trace amounts of oxygen to generate CO / CO2, resulting in a 5-10 nm decarburized layer at the interface, an increase in resistivity by an order of magnitude, and the loss of the conductivity enhancement effect.

[0098] In summary, cold pressing-vacuum hot pressing lacks the three-field coupling of "pulsed electric field - instantaneous high temperature - constant pressure", and cannot simultaneously achieve CNT orientation maintenance, grain refinement, rapid densification and interface cleanliness. Therefore, it cannot replicate the conductive-mechanical synergistic gain brought about by discharge plasma coupling high-frequency induction sintering, resulting in the failure of the technical effect.

[0099] The sintering process of spark plasma coupled high-frequency induction sintering (SPS-HF) involves strong coupling of four physical fields: electro-thermal-magnetic-mechanical. Primarily, it involves the mutual coupling between the electromagnetic field and the thermal field, stress field, and the thermal field itself. 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 effect between the electromagnetic and thermal fields, promoting material densification. The alternating magnetic field promotes liquid phase flow. The main parameter of the stress field is axial pressure, which is also the main driving force for densification. The interaction between temperature and pressure enhances the viscosity and plastic flow of the particles, which is beneficial for densification. The coupling effect of these two factors promotes the sintering of cermet materials.

[0100] As a preferred embodiment, the preparation method of carbon nanotube-reinforced tungsten carbide titanium cermet material includes the following steps:

[0101] (1) Polyethylene glycol is added to anhydrous ethanol and stirred in a water bath at a constant temperature. The mixture is then cooled to room temperature to obtain a polyethylene glycol-anhydrous ethanol dispersion.

[0102] (2) Mix (W,Ti)C powder, Ni powder, Mo powder and Co powder according to the mass ratio, add to the prepared polyethylene glycol-anhydrous ethanol dispersion, ultrasonically disperse and stir to obtain (W,Ti)C metal ceramic mixed powder.

[0103] (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 amount of grinding balls (e.g., 1:10). Grind under a protective atmosphere for 48 hours.

[0104] (4) Add sufficient concentrated nitric acid to the beaker containing CNTs, sonicate (e.g., for 30 min) and let stand (e.g., for 24 h), sonicate a second time (e.g., for 3 h) and let stand (e.g., for 24 h), sonicate a third time (e.g., for 3 h) and let stand (e.g., for 2 h).

[0105] (5) The purified CNTs were neutralized and washed using a centrifuge and then kept for later use.

[0106] (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 dissolve the sodium dodecyl sulfate fully by heating in a water bath. Add the purified CNTs to the beaker and disperse them by vigorous stirring in an ultrasonic bath (60 min).

[0107] (7) Add the dispersed CNTs to the (W,Ti)C cermet mixture powder after ball milling and continue ball milling (e.g., for 3 hours). Vacuum dry the ball-milled slurry.

[0108] (8) Put the dried mixed powder back into the ball mill jar for dry ball milling and then sieve it to obtain mixed powder, and seal it for later use.

[0109] (9) The mixed powder was placed in a graphite mold and subjected to high-frequency induction sintering by discharge plasma coupling under a vacuum atmosphere to obtain carbon nanotube-reinforced tungsten carbide titanium metal ceramic material.

[0110] In a third embodiment, the present invention provides the application of the above-mentioned carbon nanotube-reinforced tungsten carbide titanium cermet material in the preparation of ceramic cutting tools and electrical discharge machining (EDM) electrodes. The material prepared by the present invention also has high conductivity and can be used as an EDM electrode.

[0111] 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.

[0112] To enable those skilled in the art to better 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.

[0113] Example 1

[0114] In the examples, the average particle size of the (W,Ti)C powder was 1~3μm, and the average particle size of the Ni, Mo, and Co powders was 1~1.5μm; all were commercially available products. The polyethylene glycol used was PEG6000.

[0115] The mass percentage of each component in the carbon nanotube-reinforced tungsten carbide titanium cermet material is as follows: (W,Ti)C 84.9%, Ni 3.5%, Mo 6.5%, Co 5%, CNTs 0.1%.

[0116] The preparation method of the carbon nanotube-reinforced tungsten carbide titanium cermet material includes the following steps:

[0117] (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 amount of 3 g / L.

[0118] (2) Mix the powders of (W,Ti)C 84.9%, Ni 3.5%, Mo 6.5%, and Co 5% according to their mass percentages, add them to the polyethylene glycol-anhydrous ethanol dispersion prepared in step (1), ultrasonically disperse for 60 min and mechanically stir to obtain a mixed solution; the mass of polyethylene glycol in the polyethylene glycol-anhydrous ethanol dispersion is 1% of the sum of the mass of (W,Ti)C, Ni, Mo, and Co powders.

[0119] (3) The prepared mixed solution is placed in a ball milling jar, wherein the grinding balls used for ball milling are cemented carbide grinding balls, and the cemented carbide grinding balls are a mixture of cemented carbide grinding balls with diameters of 4 mm and 8 mm. The mass ratio of cemented carbide grinding balls with diameters of 4 mm and 8 mm is 2:3, and the mass ratio of ball to material is 10:1. The ball milling is carried out for 48 hours under a nitrogen protective atmosphere.

[0120] (4) Weigh 0.1% of the total mass of CNTs and put them into a beaker for purification. Add sufficient concentrated nitric acid to the beaker containing CNTs, sonicate for 30 min and let stand for 24 h, sonicate for 3 h a second time and let stand for 24 h, sonicate for 3 h a third time and let stand for 2 h.

[0121] (5) The purified CNTs were neutralized and washed by centrifugation and then set aside for use. A Michael high-speed centrifuge was used, and the centrifugation parameters were set to 6500 r / min and 5 min. The centrifugation was repeated 7 times until the pH of the CNTs suspension reached 7. The washing agent was distilled water.

[0122] (6) Weigh out sodium dodecyl sulfate of the same mass as CNTs and pour it into a beaker. Add 100 ml of anhydrous ethanol to the beaker and dissolve the sodium dodecyl sulfate by heating in a water bath. Add the neutralized CNTs to the beaker and disperse them by vigorous stirring in an ultrasonic bath for 60 min.

[0123] (7) Add the dispersed CNTs to the (W,Ti)C cermet mixture powder after ball milling and continue ball milling for 3 h. Dry the ball milling slurry under vacuum at 120℃ for 36 h;

[0124] (8) The dried mixed powder is put back into the ball mill jar 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 then sealed for later use.

[0125] (9) Carbon nanotube-reinforced tungsten carbide titanium cermet powder was placed in a graphite mold and subjected to high-frequency induction sintering via discharge plasma coupling under a vacuum atmosphere. The sintering temperature was 1350℃, the sintering pressure was 35MPa, and the heating rate was as follows: preheating to 570℃ and then heating to 600℃ within 1 min; heating to 900℃ at 100℃ / min; heating to 1250℃ at 75℃ / min; heating to the target temperature at 50℃ / min, with a holding time of 10 min, to obtain carbon nanotube-reinforced tungsten carbide titanium cermet material. The peak sintering current 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 19.45 GPa.

[0126] Example 2

[0127] In the examples, the average particle size of the (W,Ti)C powder was 1~3μm, and the average particle size of the Ni, Mo, and Co powders was 1~1.5μm; all were commercially available products. The polyethylene glycol used was PEG6000.

[0128] The mass percentage of each component in the carbon nanotube-reinforced tungsten carbide titanium cermet material is as follows: (W,Ti)C 84.8%, Ni 3.5%, Mo 6.5%, Co 5%, CNTs 0.2%.

[0129] The preparation method of the carbon nanotube-reinforced tungsten carbide titanium cermet material includes the following steps:

[0130] (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 amount of 3 g / L.

[0131] (2) Mix the powders of (W,Ti)C 84.8%, Ni 3.5%, Mo 6.5%, and Co 5% according to their mass percentages, add them to the polyethylene glycol-anhydrous ethanol dispersion prepared in step (1), ultrasonically disperse for 60 min and mechanically stir to obtain a mixed solution; the mass of polyethylene glycol in the polyethylene glycol-anhydrous ethanol dispersion is 1% of the sum of the mass of (W,Ti)C, Ni, Mo, and Co powders.

[0132] (3) The prepared mixed solution is placed in a ball milling jar, wherein the grinding balls used for ball milling are cemented carbide grinding balls, and the cemented carbide grinding balls are a mixture of cemented carbide grinding balls with diameters of 4 mm and 8 mm. The mass ratio of cemented carbide grinding balls with diameters of 4 mm and 8 mm is 2:3, and the mass ratio of ball to material is 10:1. The ball milling is carried out for 48 hours under a nitrogen protective atmosphere.

[0133] (4) Weigh 0.2% of the total mass of CNTs and put them into a beaker for purification. Add sufficient concentrated nitric acid to the beaker containing CNTs, sonicate for 30 min and let stand for 24 h, sonicate for 3 h a second time and let stand for 24 h, sonicate for 3 h a third time and let stand for 2 h.

[0134] (5) The purified CNTs were neutralized and washed by centrifugation and then set aside for use. A Michael high-speed centrifuge was used, and the centrifugation parameters were set to 6500 r / min and 5 min. The centrifugation was repeated 7 times until the pH of the CNTs suspension reached 7. The washing agent was distilled water.

[0135] (6) Weigh out sodium dodecyl sulfate of the same mass as CNTs and pour it into a beaker. Add 100 ml of anhydrous ethanol to the beaker and dissolve the sodium dodecyl sulfate by heating in a water bath. Add the neutralized CNTs to the beaker and disperse them by vigorous stirring in an ultrasonic bath for 60 min.

[0136] (7) Add the dispersed CNTs to the (W,Ti)C cermet mixture powder after ball milling and continue ball milling for 3 h. Dry the ball milling slurry under vacuum at 120℃ for 36 h;

[0137] (8) The dried mixed powder is put back into the ball mill jar 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 then sealed for later use.

[0138] (9) Carbon nanotube-reinforced tungsten carbide titanium cermet powder was placed in a graphite mold and subjected to high-frequency induction sintering via discharge plasma coupling under a vacuum atmosphere. The sintering temperature was 1350℃, the sintering pressure was 35MPa, and the heating rate was as follows: preheating to 570℃ and then heating to 600℃ within 1 min; heating to 900℃ at 100℃ / min; heating to 1250℃ at 75℃ / min; heating to the target temperature at 50℃ / min, with a holding time of 10 min, to obtain carbon nanotube-reinforced tungsten carbide titanium cermet material. The peak sintering current 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 19.83 GPa.

[0139] Example 3

[0140] In the examples, the average particle size of the (W,Ti)C powder was 1~3μm, and the average particle size of the Ni, Mo, and Co powders was 1~1.5μm; all were commercially available products. The polyethylene glycol used was PEG6000.

[0141] The mass percentage of each component in the carbon nanotube-reinforced tungsten carbide titanium cermet material is as follows: (W,Ti)C 84.7%, Ni 3.5%, Mo 6.5%, Co 5%, CNTs 0.3%.

[0142] The preparation method of the carbon nanotube-reinforced tungsten carbide titanium cermet material includes the following steps:

[0143] (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 amount of 3 g / L.

[0144] (2) Mix the powders of (W,Ti)C 84.8%, Ni 3.5%, Mo 6.5%, and Co 5% according to their mass percentages, add them to the polyethylene glycol-anhydrous ethanol dispersion prepared in step (1), ultrasonically disperse for 60 min and mechanically stir to obtain a mixed solution; the mass of polyethylene glycol in the polyethylene glycol-anhydrous ethanol dispersion is 1% of the sum of the masses of (W,Ti)C, Ni, Mo, and Co powders.

[0145] (3) The prepared mixed solution is placed in a ball milling jar, wherein the grinding balls used for ball milling are cemented carbide grinding balls, and the cemented carbide grinding balls are a mixture of cemented carbide grinding balls with diameters of 4 mm and 8 mm. The mass ratio of cemented carbide grinding balls with diameters of 4 mm and 8 mm is 2:3, and the mass ratio of ball to material is 10:1. The ball milling is carried out for 48 hours under a nitrogen protective atmosphere.

[0146] (4) Weigh 0.3% of the total mass of CNTs and put them into a beaker for purification. Add sufficient concentrated nitric acid to the beaker containing CNTs, sonicate for 30 min and let stand for 24 h, sonicate for 3 h a second time and let stand for 24 h, sonicate for 3 h a third time and let stand for 2 h.

[0147] (5) The purified CNTs were neutralized and washed by centrifugation and then set aside for use. A Michael high-speed centrifuge was used, and the centrifugation parameters were set to 6500 r / min and 5 min. The centrifugation was repeated 7 times until the pH of the CNTs suspension reached 7. The washing agent was distilled water.

[0148] (6) Weigh out sodium dodecyl sulfate of the same mass as CNTs and pour it into a beaker. Add 100 ml of anhydrous ethanol to the beaker and dissolve the sodium dodecyl sulfate by heating in a water bath. Add the neutralized CNTs to the beaker and disperse them by vigorous stirring in an ultrasonic bath for 60 min.

[0149] (7) Add the dispersed CNTs to the (W,Ti)C cermet mixture powder after ball milling and continue ball milling for 3 h. Dry the ball milling slurry under vacuum at 120℃ for 36 h;

[0150] (8) The dried mixed powder is put back into the ball mill jar 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 then sealed for later use.

[0151] (9) Carbon nanotube-reinforced tungsten carbide titanium cermet powder was placed in a graphite mold and subjected to high-frequency induction sintering via discharge plasma coupling under a vacuum atmosphere. The sintering temperature was 1350℃, the sintering pressure was 35MPa, and the heating rate was as follows: preheating to 570℃ and then heating to 600℃ within 1 min; heating to 900℃ at 100℃ / min; heating to 1250℃ at 75℃ / min; heating to the target temperature at 50℃ / min, with a holding time of 10 min, to obtain carbon nanotube-reinforced tungsten carbide titanium cermet material. The peak sintering current 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 19.23 GPa.

[0152] Example 4

[0153] In the examples, the average particle size of the (W,Ti)C powder was 1~3μm, and the average particle size of the Ni, Mo, and Co powders was 1~1.5μm; all were commercially available products. The polyethylene glycol used was PEG6000.

[0154] The mass percentage of each component in the carbon nanotube-reinforced tungsten carbide titanium cermet material is as follows: (W,Ti)C 84.6%, Ni 3.5%, Mo 6.5%, Co 5%, CNTs 0.4%.

[0155] The preparation method of the carbon nanotube-reinforced tungsten carbide titanium cermet material includes the following steps:

[0156] (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 amount of 3 g / L.

[0157] (2) Mix the powders of (W,Ti)C 84.6%, Ni 3.5%, Mo 6.5%, and Co 5% according to their mass percentages, add them to the polyethylene glycol-anhydrous ethanol dispersion prepared in step (1), ultrasonically disperse for 60 min and mechanically stir to obtain a mixed solution; the mass of polyethylene glycol in the polyethylene glycol-anhydrous ethanol dispersion is 1% of the sum of the mass of (W,Ti)C, Ni, Mo, and Co powders.

[0158] (3) The prepared mixed solution is placed in a ball milling jar, wherein the grinding balls used for ball milling are cemented carbide grinding balls, and the cemented carbide grinding balls are a mixture of cemented carbide grinding balls with diameters of 4 mm and 8 mm. The mass ratio of cemented carbide grinding balls with diameters of 4 mm and 8 mm is 2:3, and the mass ratio of ball to material is 10:1. The ball milling is carried out for 48 hours under a nitrogen protective atmosphere.

[0159] (4) Weigh 0.4% of the total mass of CNTs and put them into a beaker for purification. Add sufficient concentrated nitric acid to the beaker containing CNTs, sonicate for 30 min and let stand for 24 h, sonicate for 3 h a second time and let stand for 24 h, sonicate for 3 h a third time and let stand for 2 h.

[0160] (5) The purified CNTs were neutralized and washed by centrifugation and then set aside for use. A Michael high-speed centrifuge was used, and the centrifugation parameters were set to 6500 r / min and 5 min. The centrifugation was repeated 7 times until the pH of the CNTs suspension reached 7. The washing agent was distilled water.

[0161] (6) Weigh out sodium dodecyl sulfate of the same mass as CNTs and pour it into a beaker. Add 100 ml of anhydrous ethanol to the beaker and dissolve the sodium dodecyl sulfate by heating in a water bath. Add the neutralized CNTs to the beaker and disperse them by vigorous stirring in an ultrasonic bath for 60 min.

[0162] (7) Add the dispersed CNTs to the (W,Ti)C cermet mixture powder after ball milling and continue ball milling for 3 h. Dry the ball milling slurry under vacuum at 120℃ for 36 h;

[0163] (8) The dried mixed powder is put back into the ball mill jar 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 then sealed for later use.

[0164] (9) Carbon nanotube-reinforced tungsten carbide titanium cermet powder was placed in a graphite mold and subjected to high-frequency induction sintering via discharge plasma coupling under a vacuum atmosphere. The sintering temperature was 1350℃, the sintering pressure was 35MPa, and the heating rate was as follows: preheating to 570℃ and then heating to 600℃ within 1 min; heating to 900℃ at 100℃ / min; heating to 1250℃ at 75℃ / min; heating to the target temperature at 50℃ / min, with a holding time of 10 min, to obtain carbon nanotube-reinforced tungsten carbide titanium cermet material. The peak sintering current 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: bending strength 996MPa, fracture toughness 7.8MPa·m. 1 / 2 Vickers hardness 18.86 GPa.

[0165] Example 5

[0166] In the examples, the average particle size of the (W,Ti)C powder was 1~3μm, and the average particle size of the Ni, Mo, and Co powders was 1~1.5μm; all were commercially available products. The polyethylene glycol used was PEG6000.

[0167] The mass percentage of each component in the carbon nanotube-reinforced tungsten carbide titanium cermet material is as follows: (W,Ti)C 84.5%, Ni 3.5%, Mo 6.5%, Co 5%, CNTs 0.5%.

[0168] The preparation method of the carbon nanotube-reinforced tungsten carbide titanium cermet material includes the following steps:

[0169] (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 amount of 3 g / L.

[0170] (2) Mix the powders of (W,Ti)C 84.5%, Ni 3.5%, Mo 6.5%, and Co 5% according to their mass percentages, add them to the polyethylene glycol-anhydrous ethanol dispersion prepared in step (1), ultrasonically disperse for 60 min and mechanically stir to obtain a mixed solution; the mass of polyethylene glycol in the polyethylene glycol-anhydrous ethanol dispersion is 1% of the sum of the mass of (W,Ti)C, Ni, Mo, and Co powders.

[0171] (3) The prepared mixed solution is placed in a ball milling jar, wherein the grinding balls used for ball milling are cemented carbide grinding balls, and the cemented carbide grinding balls are a mixture of cemented carbide grinding balls with diameters of 4 mm and 8 mm. The mass ratio of cemented carbide grinding balls with diameters of 4 mm and 8 mm is 2:3, and the mass ratio of ball to material is 10:1. The ball milling is carried out for 48 hours under a nitrogen protective atmosphere.

[0172] (4) Weigh 0.5% of the total mass of CNTs and put them into a beaker for purification. Add sufficient concentrated nitric acid to the beaker containing CNTs, sonicate for 30 min and let stand for 24 h, sonicate for 3 h a second time and let stand for 24 h, sonicate for 3 h a third time and let stand for 2 h.

[0173] (5) The purified CNTs were neutralized and washed by centrifugation and then set aside for use. A Michael high-speed centrifuge was used, and the centrifugation parameters were set to 6500 r / min and 5 min. The centrifugation was repeated 7 times until the pH of the CNTs suspension reached 7. The washing agent was distilled water.

[0174] (6) Weigh out sodium dodecyl sulfate of the same mass as CNTs and pour it into a beaker. Add 100 ml of anhydrous ethanol to the beaker and dissolve the sodium dodecyl sulfate by heating in a water bath. Add the neutralized CNTs to the beaker and disperse them by vigorous stirring in an ultrasonic bath for 60 min.

[0175] (7) Add the dispersed CNTs to the (W,Ti)C cermet mixture powder after ball milling and continue ball milling for 3 h. Dry the ball milling slurry under vacuum at 120℃ for 36 h;

[0176] (8) The dried mixed powder is put back into the ball mill jar 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 then sealed for later use.

[0177] (9) Carbon nanotube-reinforced tungsten carbide titanium cermet powder was placed in a graphite mold and subjected to high-frequency induction sintering via discharge plasma coupling under a vacuum atmosphere. The sintering temperature was 1350℃, the sintering pressure was 35MPa, and the heating rate was as follows: preheating to 570℃ and then heating to 600℃ within 1 min; heating to 900℃ at 100℃ / min; heating to 1250℃ at 75℃ / min; heating to the target temperature at 50℃ / min, with a holding time of 10 min, to obtain carbon nanotube-reinforced tungsten carbide titanium cermet material. The peak sintering current 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: bending strength 983MPa, fracture toughness 8.7MPa·m. 1 / 2 Vickers hardness 18.69 GPa.

[0178] Comparative Example 1

[0179] This comparative example is the same as Example 2, but the mass percentage content in step (2) is (W,Ti)C 85%, Ni 3.5%, Mo 6.5%, Co 5%, and CNTs are not added to the tungsten carbide titanium cermet powder. Other preparation methods are the same as in Example 2. The peak sintering current is 2745A, the average grain size is 3.2μm, and the relative density of the material is 95.3%. At this point, the grains have not grown sufficiently, and densification sintering has not been achieved. The obtained ceramic material sample is cut and processed, and its mechanical properties are measured as follows: bending strength 532MPa, fracture toughness 5.6MPa·m. 1 / 2 Vickers hardness 12.76 GPa.

[0180] Comparative Example 2

[0181] This comparative example is the same as Example 2, but the sintering temperature in step (9) is set to 1400℃, and the other preparations are the same as in Example 2. The average grain size is 7.2μm, and the relative density is 96.2%. At this point, the grains have grown abnormally and there are a large number of pores on the material cross-section. The obtained ceramic material sample was cut and processed, and its mechanical properties were measured as follows: bending strength 764MPa, fracture toughness 6.7MPa·m. 1 / 2 Vickers hardness 16.26 GPa.

[0182] Comparative Example 3

[0183] This comparative example is the same as Example 2, except that the dry ball milling in step (8) was not performed and the sample was directly sieved. Other preparations were the same as in Example 2. The obtained ceramic material sample was cut and processed, and its mechanical properties were measured as follows: bending strength 938 MPa, fracture toughness 7.2 MPa·m. 1 / 2 Vickers hardness 18.34 GPa. Average grain size 4.9 μm.

[0184] Comparative Example 4

[0185] This comparative example is the same as Example 2, except that in step (9), high-frequency induction sintering coupled with spark plasma coupling was not used; only spark plasma sintering was used. The other preparation methods are the same as in Example 2. The obtained ceramic material sample was cut and processed, and its mechanical properties were measured as follows: flexural strength 823 MPa, fracture toughness 6.9 MPa·m. 1 / 2 Vickers hardness 15.47 GPa. Average grain size 4.8 μm.

[0186] Comparative Example 5

[0187] This comparative example is the same as Example 2, but the mass percentage content in step (2) is (W,Ti)C 85%, Ni 3.5%, Mo 6.5%, 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℃. Other preparations are the same as in Example 2.

[0188] The peak sintering current was 2857 A, the average grain size was 5.8 μm, and the material relative density was 99.1%, indicating sufficient grain growth and achieving densified sintering. The prepared ceramic material sample was cut and processed, and its mechanical properties were measured as follows: flexural strength 869 MPa, fracture toughness 7.0 MPa·m. 1 / 2 Vickers hardness 19.63 GPa.

[0189] As can be seen from the comparison between Example 2 and Examples 1-5 and Comparative Example 1, the content of CNTs added has a significant impact on the discharge environment during the sintering process, and thus affects the mechanical properties of the material.

[0190] As can be seen from the comparison between Example 2 and Comparative Example 2, the addition of CNTs reduced the sintering temperature, thereby reducing energy consumption.

[0191] As can be seen from the comparison between Example 2 and Comparative Example 3, the method of dry ball milling followed by ball milling improves the dispersion effect of CNTs and enhances the mechanical properties of the material.

[0192] As can be seen from the comparison between Example 2 and Comparative Example 4, the discharge plasma coupling high-frequency induction sintering has a significant impact on improving the sintering environment of CNTs.

[0193] A comparison of Example 2 with Comparative Examples 1 and 5 shows that, without the addition of CNTs, densification sintering cannot be achieved at 1350℃ during the preparation of ceramic materials; a higher temperature (1450℃) is required. Furthermore, the mechanical properties and electrical conductivity of the resulting ceramic material are inferior to those of the present invention. The present invention employs spark plasma coupling high-frequency induction sintering, utilizing the excellent conductivity of carbon nanotubes to improve the discharge environment. This allows for material densification sintering at 1350℃, reducing the sintering temperature by 100℃, decreasing energy loss, lowering the peak sintering current, significantly reducing production costs, and further improving mechanical properties and electrical conductivity.

[0194] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A carbon nanotube-reinforced tungsten carbide titanium cermet material, characterized in that, It includes a matrix, a metal binder phase, and a reinforcing phase, wherein the matrix is ​​(W,Ti)C, the reinforcing phase is CNTs, and the metal binder phase is Ni, Mo, and Co; The mass percentages of each component are as follows: (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 masses of each component is 100%. The preparation method of the carbon nanotube-reinforced tungsten carbide titanium metal ceramic material includes the following steps: (W,Ti)C powder, Ni powder, Mo powder and Co powder are mixed in a mass ratio and dispersed in a polyethylene glycol-anhydrous ethanol dispersion. The resulting (W,Ti)C cermet mixed powder is then subjected to a first ball milling process. The purified and neutralized CNTs were dispersed, and the dispersed CNTs were added to the (W,Ti)C cermet mixed powder that had been ball-milled in the first ball milling process. The powder was then ball-milled a second time and dried. The dried mixed powder is subjected to a third ball milling process to obtain a mixed powder body, which is then subjected to discharge plasma coupling high-frequency induction sintering to obtain the final product.

2. The carbon nanotube-reinforced tungsten carbide titanium cermet material according to claim 1, characterized in that, The mass percentage of each component is as follows: (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 masses of each component is 100%.

3. The carbon nanotube-reinforced tungsten carbide titanium cermet material according to claim 2, characterized in that, The mass percentages of each component are as follows: (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 masses 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 cermet is 3.5~5μm.

4. A method for preparing the carbon nanotube-reinforced tungsten carbide titanium cermet material according to any one of claims 1-3, characterized in that, Includes the following steps: (W,Ti)C powder, Ni powder, Mo powder and Co powder are mixed in a mass ratio and dispersed in a polyethylene glycol-anhydrous ethanol dispersion. The resulting (W,Ti)C cermet mixed powder is then subjected to a first ball milling process. The purified and neutralized CNTs were dispersed, and the dispersed CNTs were added to the (W,Ti)C cermet mixed powder that had been ball-milled in the first ball milling process. The powder was then ball-milled a second time and dried. The dried mixed powder is subjected to a third ball milling process to obtain a mixed powder body, which is then subjected to discharge plasma coupling high-frequency induction sintering to obtain the final product.

5. The preparation method according to claim 4, characterized in that, Polyethylene glycol was added to anhydrous ethanol and stirred in a water bath at a constant temperature. The mixture was then cooled to room temperature to obtain a polyethylene glycol-anhydrous ethanol dispersion. The water bath temperature is 60-70℃, the stirring is done with magnetic stirring, and the stirring time is 15-20 minutes; the polyethylene glycol-anhydrous ethanol dispersion contains 3-5 g / L of polyethylene glycol. The mass of polyethylene glycol in the polyethylene glycol-anhydrous ethanol dispersion is 0.5% to 1.5% of the sum of the masses of (W,Ti)C powder, Ni powder, Mo powder, and Co powder. The first ball milling process is as follows: the total amount of raw material to the weight ratio of grinding balls is 1:(8~15), and the ball milling time is 24~72h under a protective atmosphere; The protective atmosphere during the ball milling process is nitrogen, and the grinding balls used are cemented carbide grinding balls; the cemented carbide balls are a mixture of 4mm and 8mm diameter cemented carbide grinding balls, and the mass ratio of 4mm and 8mm diameter cemented carbide balls is (2~2.5):(3~3.5); In the second ball milling process, the ball milling time is 2-4 hours; The third ball milling process is dry ball milling, with a milling time of 0.5 to 1.5 hours.

6. The preparation method according to claim 4, characterized in that, The purification process for CNTs was as follows: CNTs were mixed with concentrated nitric acid, ultrasonically vibrated for 20-40 min and then allowed to stand for 12-36 h, ultrasonically vibrated for 1-5 h a second time and then allowed to stand for 12-36 h, and ultrasonically vibrated for 1-5 h a third time and then allowed to stand for 0.5-3 h. Among them, 25~35wt% concentrated nitric acid is used; After purification, neutralization and washing are required to obtain neutralized CNTs. During the neutralization and washing process, the centrifugation parameters are set to 6000~7000 r / min and 4~6 min. The centrifugation is repeated 5~8 times until the pH value of the CNTs suspension reaches 6.8~7.

2. Sodium dodecyl sulfate was dissolved in anhydrous ethanol and heated in a water bath to fully dissolve it. Then, neutralized CNTs were added and the mixture was vigorously stirred and dispersed in an ultrasonic bath for 0.5 to 2 hours to obtain dispersed CNTs. During the dispersion of CNTs, the mass ratio of sodium dodecyl sulfate to CNTs was (0.9 to 1.1):(0.9 to 1.1).

7. The preparation method according to claim 4, characterized in that, The mixed powder was placed in a graphite mold and subjected to high-frequency induction sintering by discharge plasma coupling under a vacuum atmosphere to obtain 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 then heating to 590~610℃ within 1 minute; heating to 890~910℃ at 90~110℃ / min; heating to 1240~1260℃ at 70~80℃ / min; and heating to the target temperature at 45~55℃ / min, with a holding time of 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. The application of the carbon nanotube-reinforced tungsten carbide titanium metal ceramic material according to any one of claims 1-3 or the carbon nanotube-reinforced tungsten carbide titanium metal ceramic material obtained by the preparation method according to any one of claims 4-8 in the preparation of ceramic cutting tools and electrical discharge machining electrodes.

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

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