A method for preparing high-entropy carbide-based cermet

Abstract

The present invention discloses a method for preparing a high-entropy carbide-based cermet, comprising the following steps: step one, preparing the cermet according to the molar ratio of the carbide additive phase, placing the powder in a sand mill, and first ball milling the cermet; step two, ball milling the cermet for the second time, adding a metal binder, carbon black, paraffin wax, rubber, or polyvinyl alcohol, and then ball milling the mixed carbide powder; after the ball milling is completed, the mixed powder is spray-dried; step three, pressing the powder into a shape at a pressure of 50-200 MPa; step four, degreasing and sintering the pressed green body to obtain a high-entropy carbide-based cermet. The present invention can obtain a flexural strength better than 2100 MPa and a fracture toughness better than 8.5 MPa·m 0.5 , Rockwell hardness better than 92.0, high entropy carbide-based metal ceramic materials can be widely used in bearing materials, cutting tools, mold materials and other fields.

Description

Technical Field

[0001] The present invention relates to the technical field of metal ceramics, and in particular to a method for preparing high-entropy carbide-based metal ceramics. Background Art

[0002] Transition metal carbides, such as TiC, WC, and Mo2C, possess high red hardness, high strength, and excellent wear resistance, making them the primary wear-resistant components of high-speed cutting tools and hot-working die materials for processing steel and other metals. Currently, transition metal carbides composed of four or five equal (or near-equal) molar ratios of metal atoms, such as (TiWMoVNb)C and (TaZrNbWMo)C, have become a research hotspot. Due to their high entropy, these high-entropy carbides possess a more stable phase structure than conventional transition metal carbides, exhibiting excellent chemical stability, high red hardness, and wear resistance, making them potential candidates for the next generation of cermets. Consequently, developing cermets composed of high-entropy carbides as the primary ceramic component, bonded by a metallic binder such as iron, cobalt, or nickel, holds great potential for performance and application.

[0003] However, obtaining high-entropy carbide-based cermets with uniform phases, high density, and fine grains is currently a significant challenge. The main reasons are as follows: 1. The preparation of high-entropy carbide ceramic powder raw materials is still immature. Although there are many chemical synthesis methods such as co-precipitation to achieve this, they are difficult to mass-produce and are costly. 2. If high-entropy carbide powder is prepared by mixing multiple components and then calcining them, the calcination temperature must be relatively high (up to 1900-2000°C) to achieve uniform diffusion between the multiple components. This will result in coarse grains in the generated high-entropy carbide powder, which reduces the mechanical properties of the cermet.

[0004] In order to obtain high-performance high-entropy cermets with fine grains and a single phase, existing high-entropy cermets require ultrafine high-entropy carbide ceramic powder with high sintering activity. Therefore, there are two main problems.

[0005] Question 1: Ultra-high-activity high-entropy carbide ceramic powder needs to have a powder particle size of micro-nano level, such as below 0.5 microns. However, the synthesis temperature of high-entropy carbide powder is high (it needs to diffuse evenly to form a high-entropy ceramic single phase), which easily produces powder particles with larger grains. At the same time, if chemical synthesis is adopted, although ultra-fine high-entropy ceramic powder can be synthesized using precursors, this method is not suitable for industrial mass production.

[0006] Question 2: High-entropy carbides are difficult to form high-entropy phases and require very high carbonization temperatures, which will result in coarse grain structure of the formed high-entropy metal ceramics and mechanical properties that are difficult to match those of conventional metal ceramic materials. Summary of the Invention

[0007] The purpose of the present invention is to solve the shortcomings of the prior art and to propose a method for preparing a high entropy carbide-based cermet.

[0008] In order to achieve the above object, a method for preparing a high entropy carbide-based cermet comprises the following steps:

[0009] Step 1: Prepare the powder according to the molar ratio of the carbide additive phase, place the powder in a sand mill, and first perform the first ball milling with a ball-to-material ratio of 10-15:1, a ball milling time of 2-5 hours, a ball milling speed of 50-100 r / min, and anhydrous ethanol as the grinding medium. Then, vacuum dry the powder after high-energy milling. After drying, vacuum pack and store it;

[0010] Step 2: Perform a second ball milling. The mixed carbide powder is then added with a metal binder, carbon black, and a binder such as paraffin, rubber, or polyvinyl alcohol. The mixture is then ball milled using anhydrous ethanol as the milling medium, a ball-to-material ratio of 5:1-8:1, and a milling time of 24-48 hours at a speed of 80-120 rpm. After ball milling, the mixed powder is spray dried at a temperature of 50-80°C to a particle size of 20-50 microns.

[0011] Step 3: Press the powder into a mold at a pressure of 50-200 MPa.

[0012] In step 4, the green compact is degreased and sintered to obtain a high-entropy carbide-based cermet; the sintering is vacuum sintering or atmosphere pressure sintering. If vacuum sintering is performed, the vacuum degree is 5-50 Pa; if atmosphere pressure sintering is performed, the protective gas is argon, and the pressure is 0.5-5 MPa; the sintering temperature is 1400-1500°C, and the sintering time is 1-3 hours.

[0013] Preferably, in step 1, the carbide is commercial carbide powder, which is composed of at least 4-6 transition metal carbides selected from TiC, WC, Mo2C, TaC, NbC, ZrC, VC, HfC and Cr2C3; the molar ratio of the metal elements of each added phase is 0.8-1:1-1.2, and the ratio difference is ≤20wt%, and the metal binder phase used is at least one of iron, cobalt and nickel.

[0014] Preferably, the 4-6 transition metal carbides contain at least two phases of TiC and WC.

[0015] Preferably, in step 1, the carbide additive phase can be added in the form of elemental carbide powder or solid solution powder.

[0016] Preferably, in step 1, the molar ratio of the metal elements of each added phase of the carbide is 0.9-1:1-1.1.

[0017] Preferably, the average particle size of the commercial carbide powder is 0.5-5.0 microns, the average particle size of the binder phase powder is 1.0-3.0 microns, and the average particle size of the carbon black is 0.1-2.0 microns.

[0018] Preferably, in step 2, the metal binder content is 15-25wt%, the carbon black mass fraction accounts for 0.8-2.0% of the total powder, and the binder content such as paraffin, rubber or polyvinyl alcohol accounts for 1.0-3.0wt% of the metal ceramic powder mass.

[0019] Preferably, in step 2, the carbon black is one of colloidal graphite and pyrolytic carbon black.

[0020] Preferably, in step 4, the degreasing is carried out in a vacuum environment, the degreasing temperature is 300-500° C., and the degreasing time is 2-5 hours.

[0021] Preferably, in step 4, the sintering process is to first raise the temperature to 1000-1200° C. in a vacuum environment, keep the temperature for 1-3 hours, and then perform vacuum sintering, or introduce argon gas for pressure sintering.

[0022] Using a sand mill, 4-5 transition metal carbides are subjected to high-energy ball milling. The obtained mixed powder has reached a near-nanoscale mixing level. Although no single high-entropy carbide component is formed, it has high sintering activity and can easily form a high-entropy carbide single phase in the subsequent sintering process. The sintering temperature is low, and fine-grained high-entropy carbide-based metal ceramics can be formed.

[0023] Through the two-step ball milling method, a carbide-based metal-ceramic composite powder with high sintering activity is obtained. After subsequent liquid phase sintering, a high-entropy carbide-based metal-ceramic material with fine grains and high mechanical properties can be obtained.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1. The present invention cleverly utilizes a double ball milling process. In the first process, high-energy ball milling is used, combined with the grinding efficiency of a sand mill, to grind 4-5 transition metal carbides to the nanometer level. In the second process, the mixed transition metal carbide powders are evenly mixed with a binder phase such as iron, cobalt, and nickel. After subsequent sintering, a high-entropy carbide-based cermet is obtained.

[0026] 2. The sand mill improves the sintering activity of metal ceramic nanopowders, but the adsorbed oxygen content on its surface is significantly higher than that of conventional mixed powders. Therefore, the present invention ensures the preparation of high-entropy carbide-based metal ceramics with high sintering activity by adjusting the addition of carbon content and performing negative pressure insulation at the deoxidation temperature.

[0027] 3. The present invention can obtain a bending strength better than 2100 MPa and a fracture toughness better than 8.5 MPa·m 0.5 , Rockwell hardness better than 92.0, high entropy carbide-based metal ceramic materials can be widely used in bearing materials, cutting tools, mold materials and other fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments are briefly introduced below.

[0029] Figure 1 The present invention is a flow chart of a preparation method of high entropy carbide-based cermet.

[0030] Figure 2 This is the morphology of the high entropy carbide ceramic powder after the first step of ball milling in Example 1 of the present invention. After ball milling, the particle size of the multi-component metal ceramic carbide powder is about 200 nm.

[0031] Figure 3 This is the microscopic morphology of the high-entropy metal ceramic in Example 1 of the present invention. DETAILED DESCRIPTION

[0032] To make the objectives, technical solutions, and advantages of the present invention more clearly understood, the present invention will be further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings. It should be understood that these descriptions are merely exemplary and are not intended to limit the scope of the present invention. In addition, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessary confusion of the concepts of the present invention.

[0033] like Figure 1-Figure 3 As shown, the composition is: 83.5(W, Ta, Ti, Nb, Zr)C-15Ni-1.5C metal ceramic, where the atomic ratio of W:Ta:Ti:Nb:Zr is 1.0:1:1.1:0.9:1.0.

[0034] The cermet composition comprises 83.5 parts by weight of high-entropy carbide ceramic powder, 15 parts of a binder phase, and 1.5 parts of pyrolytic carbon black. The high-entropy carbide powders are added in the form of single-phase WC, TaC, TiC, NbC, and ZrC, with average particle sizes of 0.8, 1.2, 1.5, 0.5, and 1.0 microns, respectively. The nickel powder has a particle size of 1.0 micron, and the carbon black has a particle size of 0.2 micron.

[0035] The preparation steps of the high entropy carbide-based cermet are as follows: (1) performing the first ball milling, preparing the powder according to the molar ratio of the carbide additive phase, placing the powder in a sand mill, with a ball-to-material ratio of 12:1, a ball milling time of 3 hours, a ball milling speed of 60 r / min, and anhydrous ethanol as the grinding medium. Subsequently, the powder after high-energy grinding is vacuum dried, and after drying, vacuum packaged and stored; (2) performing the second ball milling, adding nickel powder and carbon black to the mixed carbide powder; adding paraffin wax accounting for 2 wt% of the above powder as a forming agent, and then ball milling and mixing, with anhydrous ethanol as the ball milling medium, a ball-to-material ratio of 8:1, a ball milling time of 36 hours, and a ball milling speed of 100 r / min. After ball milling, the mixed powder is spray-dried at a drying temperature of 60°C and a particle size of 20 microns; (3) the powder is pressed into a shape at a pressing pressure of 80 MPa; (4) the pressed green body is degreased and sintered to obtain a high-entropy carbide-based metal ceramic; the degreasing is carried out in a vacuum environment at a degreasing temperature of 450°C and a degreasing time of 2 hours; the sintering is vacuum sintering at a vacuum degree of 10 Pa; first, the temperature is raised to 1100°C in a vacuum environment and kept at this temperature for 2 hours, and then vacuum sintering is carried out at a sintering temperature of 1450°C and kept at this temperature for 2 hours to obtain a high-entropy carbide-based metal ceramic material.

[0036] The high entropy carbide ceramic has a grain size of 2.5 microns, a porosity of A04B00C00, a flexural strength of 2100 MPa, and a fracture toughness of 8.5 MPa·m 0.5 , Rockwell hardness is 93.2 HRA, and it is a metal ceramic tool and mold material with wide application potential.

[0037] like Figure 1 As shown, the composition is: 79(W, Mo,Ti, V, Zr)C-20Co-1.0C metal ceramic, where the atomic ratio of W: Mo:Ti:V:Zr is 1:0.9:1.0:1.0:0.8.

[0038] The cermet composition comprises 79 parts by weight of high-entropy carbide ceramic powder, 20 parts by weight of a binder phase, and 1.0 parts by weight of pyrolytic carbon black. The high-entropy carbide powders are added in the form of single-phase WC, Mo2C, TiC, VC, and ZrC, with average particle sizes of 1.5, 1.0, 1.2, 0.8, and 1.8 microns, respectively. The cobalt powder has a particle size of 1.0 micron, and the carbon black has a particle size of 0.2 micron.

[0039] The preparation steps of the high entropy carbide-based cermet are as follows: (1) performing the first ball milling, preparing the powder according to the molar ratio of the carbide additive phase, placing the powder in a sand mill, with a ball-to-material ratio of 10:1, a ball milling time of 2 hours, a ball milling speed of 60 r / min, and anhydrous ethanol as the grinding medium. Subsequently, the powder after high-energy grinding is vacuum dried, and after drying, vacuum packaged and stored; (2) performing the second ball milling, adding cobalt powder and carbon black to the mixed carbide powder; adding paraffin wax accounting for 2 wt% of the above powder as a forming agent, and then ball milling and mixing, with anhydrous ethanol as the ball milling medium, a ball-to-material ratio of 6:1, a ball milling time of 24 hours, and a ball milling speed of 100 r / min. After ball milling, the mixed powder is spray-dried at a drying temperature of 60°C and a particle size of 30 microns; (3) the powder is pressed into a shape at a pressing pressure of 100 MPa; (4) the pressed green body is degreased and sintered to obtain a high-entropy carbide-based metal ceramic; the degreasing is carried out in a vacuum environment at a degreasing temperature of 450°C and a degreasing time of 2 hours; the sintering is vacuum sintering at a vacuum degree of 10 Pa; first, the temperature is raised to 1100°C in a vacuum environment and kept at this temperature for 2 hours, and then vacuum sintering is carried out at a sintering temperature of 1450°C and kept at this temperature for 2 hours to obtain a high-entropy carbide-based metal ceramic material.

[0040] The high entropy carbide ceramic has a grain size of 1.5 microns, a porosity of A04B00C00, a flexural strength of 2240 MPa, and a fracture toughness of 9.0 MPa·m 0.5 , Rockwell hardness is 92.8 HRA, and it is a metal ceramic tool and mold material with wide application potential.

[0041] like Figure 1 As shown, the composition is: 74.2(W, Nb, Ti, V, Cr)C-15Fe-10Co-0.8C metal ceramic, where the atomic ratio of W:Nb:Ti:V:Cr is 1:0.9:1.0:1.0:0.8.

[0042] The metal ceramic component comprises 74.2 parts by weight of high-entropy carbide ceramic powder, 25 parts of a metallic binder phase, and 0.8 parts of pyrolytic carbon black. The high-entropy carbide powder is added in the form of a solid solution of (Ti0.8, W0.2)C, WC, NbC, VC, and Cr2C3. The average particle sizes of these powders are 2.5, 3.0, 1.8, 2.5, and 1.6 microns, respectively. The particle size of the iron powder is 2.0 microns, the particle size of the cobalt powder is 2.5 microns, and the particle size of the carbon black is 0.2 microns.

[0043] The preparation steps of the high entropy carbide-based cermet are as follows: (1) performing the first ball milling, preparing the powder according to the molar ratio of the carbide additive phase, placing the powder in a sand mill, with a ball-to-material ratio of 15:1, a ball milling time of 2 hours, a ball milling speed of 80 r / min, and anhydrous ethanol as the grinding medium. Subsequently, the powder after high-energy grinding is vacuum dried, and after drying, vacuum packaged and stored; (2) performing the second ball milling, adding iron powder and cobalt powder and carbon black to the mixed carbide powder; adding rubber as a forming agent with a mass fraction of 3wt% of the above powder, and then ball milling and mixing, with anhydrous ethanol as the grinding medium, a ball-to-material ratio of 8:1, a ball milling time of 48 hours, and a ball milling speed of 80 r / min. After ball milling, the mixed powder is spray-dried at a drying temperature of 60°C and a particle size of 40 microns; (3) the powder is pressed into a shape at a pressing pressure of 150 MPa; (4) the pressed green body is degreased and sintered to obtain a high-entropy carbide-based metal ceramic; the degreasing is carried out in a vacuum environment at a degreasing temperature of 480°C and a degreasing time of 3 hours; the sintering is atmosphere pressure sintering at an atmosphere pressure of 2 MPa; before sintering, the mixture is first heated to 1100°C in a vacuum environment at a vacuum degree of 10 Pa and kept warm for 2 hours, and then argon is introduced and atmosphere pressure sintering is carried out at an intake air pressure of 1420°C and an atmosphere pressure of 2 MPa, and kept warm for 1 hour, thereby obtaining a high-entropy carbide-based metal ceramic material.

[0044] The high entropy carbide ceramic has a grain size of 2.5 microns, a porosity of A02B00C00, a flexural strength of 2180 MPa, and a fracture toughness of 9.2 MPa·m 0.5 , Rockwell hardness is 92.1 HRA, and it is a metal ceramic tool and mold material with wide application potential.

[0045] Comparative Example 1

[0046] Other conditions were the same as those in Example 1, except that the added carbide additive phase powder, metal phase powder, and graphite powder were directly ball-milled without going through step 1.

[0047] The high entropy carbide ceramic grain size was found to be 5.0 microns, its porosity reached the A06B02C00 level, its bending strength was 1780 MPa, and its fracture toughness was 6.8 MPa·m 0.5 , Rockwell hardness is 91.0 HRA, which is difficult to meet the industrial demand for tooling products.

[0048] Comparative Example 2

[0049] Other conditions were the same as those in Example 2. During vacuum sintering, the temperature was directly raised to 1450° C. for sintering instead of being kept at 1100° C. for 2 h.

[0050] After testing, the grain size of the high entropy carbide ceramic is 2.0 microns, its porosity reaches the A08B00C00 level, its bending strength is 2050MPa, and its fracture toughness is 7.8MPa·m 0.5 The Rockwell hardness is 91.8 HRA. Due to the high oxygen content, the generated gas can no longer be removed during the pore opening and sintering stage, resulting in a large number of fine pores inside the sintered sample, which makes it difficult to meet the industrial demand for tooling products.

[0051] Comparative Example 3

[0052] Other conditions were the same as those in Example 3, except that the atomic ratio of W:Nb:Ti:V:Cr was 1:0.7:1.0:1.0:0.9.

[0053] After testing, the grain size of the high entropy carbide ceramic is 3.5 microns, its porosity reaches the A06B02C00 level, its bending strength is 1980MPa, and its fracture toughness is 7.5MPa·m 0.5 , Rockwell hardness is 91.0 HRA, no single high-entropy carbide ceramic phase is formed, and it is difficult to meet the industrial demand for tooling products.

[0054] It should be understood that the above-described specific embodiments of the present invention are merely illustrative or illustrative of the principles of the present invention and do not constitute limitations of the present invention. Therefore, any modifications, equivalent substitutions, improvements, etc. made without departing from the spirit and scope of the present invention should be included within the scope of protection of the present invention. In addition, the appended claims are intended to cover all variations and modifications that fall within the scope and metes and bounds of the appended claims, or equivalents thereof.

Claims

1. A method for preparing a high entropy carbide-based cermet, characterized in that: The steps include: Step 1: According to the molar ratio of the carbide additive phase, the powder is prepared and placed in a sand mill for the first ball milling. The ball-to-material ratio is 10-15:1, the ball milling time is 2-5 hours, the ball milling speed is 50-100 r / min, and the grinding medium is anhydrous ethanol. The powder after high-energy grinding is then vacuum dried. After drying, it is vacuum packaged and stored. The carbide is commercial carbide powder, which is composed of 4-6 transition metal carbides selected from TiC, WC, Mo2C, TaC, NbC, ZrC, VC, HfC and Cr2C3; Step 2: performing a second ball milling, adding a metal binder and carbon black to the mixed carbide powder, wherein the mass fraction of the carbon black is 0.8-2.0% of the total powder, paraffin, rubber or polyvinyl alcohol binder, and then ball milling. The ball milling medium is anhydrous ethanol, the ball-to-material ratio is 5:1-8:1, the ball milling time is 24-48 hours, the ball milling speed is 80-120 r / min, and after the ball milling is completed, the mixed powder is spray dried at a drying temperature of 50-80°C, and the particle size of the mixed powder is 20-50 microns; Step 3: Press the powder into a mold at a pressure of 50-200 MPa. In step 4, the green compact is degreased and sintered to obtain a high-entropy carbide-based cermet; the sintering is vacuum sintering or atmosphere pressure sintering. If vacuum sintering is performed, the vacuum degree is 5-50 Pa; if atmosphere pressure sintering is performed, the protective gas is argon, and the pressure is 0.5-5 MPa; the sintering temperature is 1400-1500°C, and the sintering time is 1-3 hours. The sintering process is to first raise the temperature to 1000-1200°C in a vacuum environment, keep warm for 1-3 hours, and then perform vacuum sintering, or introduce argon for pressure sintering.

2. The method for preparing a high entropy carbide-based cermet according to claim 1, characterized in that: The metal binder used is at least one of iron, cobalt and nickel.

3. The method for preparing a high entropy carbide-based cermet according to claim 2, characterized in that: The 4-6 transition metal carbides contain at least two phases, TiC and WC.

4. The method for preparing a high entropy carbide-based cermet according to claim 1, characterized in that: The carbide additive phase can be added in the form of single carbide powder or solid solution powder.

5. The method for preparing a high entropy carbide-based cermet according to claim 1, characterized in that: The average particle size of the commercial carbide powder is 0.5-5.0 microns, the average particle size of the metal binder is 1.0-3.0 microns, and the average particle size of the carbon black is 0.1-2.0 microns.

6. The method for preparing a high entropy carbide-based cermet according to claim 1, characterized in that: The content of the metal binder is 15-25 wt %, and the content of the paraffin wax, rubber or polyvinyl alcohol binder is 1.0-3.0 wt % of the mass of the metal ceramic powder.

7. The method for preparing a high entropy carbide-based cermet according to claim 1, characterized in that: In step 2, the carbon black is one of colloidal graphite and pyrolytic carbon black.

8. The method for preparing a high entropy carbide-based cermet according to claim 1, characterized in that: In step 4, the degreasing is carried out in a vacuum environment, the degreasing temperature is 300-500° C., and the degreasing time is 2-5 hours.

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