A high entropy composite toughened gradient ceramic tool material and its preparation method and application

Abstract

The present invention discloses a high-entropy composite toughened gradient ceramic tool material and its preparation method and application, belonging to the technical field of ceramic tool materials. It has a symmetrical five-layer structure, which is a surface layer, a transition layer, a core layer, a transition layer and a surface layer in order; by mass, the surface layer includes 85-91 parts of aluminum oxide and 9-15 parts of high-entropy carbide; the transition layer includes 82.8-90.8 parts of aluminum oxide, 6-12 parts of high-entropy carbide, 3-5 parts of zirconium dioxide, and 0.2 parts of graphene; the core layer includes 82-91 parts of aluminum oxide, 3-9 parts of high-entropy carbide, and 6-9 parts of high-entropy alloy. The thermal stress relief and surface residual compressive stress characteristics of the gradient structure are organically combined with the various toughening mechanisms introduced by the high-entropy composite of graphene, and a high-hardness, high-toughness, high-entropy composite toughened gradient ceramic tool material is obtained through liquid phase + solid phase two-step sintering, which significantly improves the adaptability and resistance of the tool to high-speed cutting.

Description

Technical Field

[0001] The present invention belongs to the technical field of ceramic cutting tool materials, and particularly relates to a high-entropy composite toughened gradient ceramic cutting tool material, a preparation method thereof and an application thereof. Background Art

[0002] Disclosing the information of this background art section is only intended to enhance the overall understanding of the present invention, and it is not necessarily regarded as an admission or any form of implication that this information constitutes the prior art already known to those of ordinary skill in the art.

[0003] Ceramic cutting tools have high hardness, wear resistance, heat resistance and chemical stability, and their main raw materials such as Al, O, Si, etc. are the most abundant elements in the earth's crust, having a very broad application prospect. However, the inherent brittleness of ceramic cutting tools limits their wide application. Since the birth of ceramic cutting tools, "toughening" has always been a core issue in their research, which can be essentially divided into intrinsic toughening and external toughening, and has experienced two main research stages: traditional toughening and new concept toughening. Traditional toughening methods mainly include: particle dispersion toughening, phase transformation toughening, whisker or fiber toughening and synergistic toughening, etc. New concept toughening methods mainly include: nano-composite toughening, carbon nanotube toughening, in-situ toughening and gradient structure toughening, etc. However, since ceramic materials are all polycrystalline structures composed of ionic bonds or covalent bonds and lack a slip system that can promote material deformation, even though the toughness of ceramic materials can be improved by the above traditional toughening and new concept toughening methods, their toughening effect is still relatively limited.

[0004] High-entropy materials are formed by multiple components mutually dissolving in an equal proportion or nearly equal proportion. Based on the synergistic effects of high-entropy effect, sluggish diffusion effect, lattice distortion effect and cocktail effect, this "super solid solution" of high-entropy materials exhibits significantly better structural stability and comprehensive properties such as thermal-mechanical-chemical than traditional materials, and has great academic research value and industrial application prospects in the fields of aerospace, composite materials, high-speed cutting tools, etc. It is a most potential toughening phase for ceramic cutting tool materials, but no research on high-entropy composite toughened ceramic cutting tools has been found. Summary of the Invention

[0005] In order to solve the deficiencies of the prior art, the purpose of the present invention is to provide a high-entropy composite toughened gradient ceramic cutting tool material, a preparation method thereof and an application thereof. The present invention provides a high-entropy composite toughened gradient ceramic cutting tool material, which has the characteristics of high hardness and high toughness, and has a simple preparation process and is suitable for industrial production.

[0006] In order to achieve the above purpose, the technical solution of the present invention is as follows:

[0007] In the first aspect of the present invention, a high-entropy composite toughened gradient ceramic cutting tool material is provided. The material has a symmetric five-layer structure, which is successively a surface layer, a transition layer, a core layer, a transition layer, and a surface layer;

[0008] The surface layer includes 85-91 parts by mass of aluminum oxide and 9-15 parts by mass of high-entropy carbide;

[0009] The transition layer includes 82.8-90.8 parts by mass of aluminum oxide, 6-12 parts by mass of high-entropy carbide, 3-5 parts by mass of zirconia, and 0.2 part by mass of graphene;

[0010] The core layer includes 82-91 parts by mass of aluminum oxide, 3-9 parts by mass of high-entropy carbide, and 6-9 parts by mass of high-entropy alloy.

[0011] In some embodiments of the present invention, the high-entropy carbide includes any five of HfC, NbC, TaC, TiC, WC, and ZrC in equimolar ratio; the high-entropy alloy includes any five of Fe, Co, Ni, Cr, Mn, and Al in equimolar ratio.

[0012] In the present invention, introducing cubic-phase high-entropy carbide into the surface layer significantly improves the hardness of the ceramic cutting tool material to meet the requirements of high wear resistance of the rake face of the cutting tool during high-speed cutting; on the basis of introducing high-entropy carbide into the transition layer, nano-zirconia and graphene are introduced, which significantly improves the toughness of the tool transition layer on the basis of high wear resistance and effectively inhibits the crack from spreading into the tool interior; introducing both high-entropy carbide and high-entropy alloy into the core layer can greatly improve the overall strength and toughness of the ceramic cutting tool material to meet the requirements of high anti-destruction of the cutting tool during high-speed cutting. In addition, in the present invention, the content of high-entropy carbide decreases from the surface to the inside, and the total content of oxide and high-entropy alloy increases, which can ensure the formation of residual compressive stress on the surface layer of the ceramic cutting tool material, thereby significantly improving the anti-fatigue performance of the tool. Combining the thermal stress relief and surface residual compressive stress characteristics of the gradient structure with the multiple toughening mechanisms introduced by graphene high-entropy composite, through two-step liquid-phase + solid-phase sintering, a high-hardness, high-strength and tough high-entropy composite toughened gradient ceramic cutting tool material is obtained, thereby significantly improving the adaptability and resistance of the ceramic cutting tool to high-speed cutting.

[0013] In the second aspect of the present invention, a preparation method of the above-mentioned high-entropy composite toughened gradient ceramic cutting tool material is provided, including the following steps:

[0014] Prepare the powders of each layer according to the raw material ratio of each layer of the five-layer symmetric layer structure. The powders of each layer are loaded by the layered pressing method, and the five-layer gradient powder body is pressed into shape, and then two-step spark plasma sintering is carried out to obtain the product.

[0015] In some embodiments of the present invention, the process of the two-step spark plasma sintering is as follows:

[0016] The vacuum degree is maintained below 10 Pa, heated to 1700 - 1750 °C at a rate of 100 - 200 °C / min, held for 1 - 5 min, then cooled to 1400 - 1600 °C at a rate of 100 - 200 °C / min and held for 1 - 6 h, and then cooled in the furnace; during the heating process, the pressure is maintained at 15 - 25 MPa from room temperature to 1150 - 1250 °C, and at 45 - 55 MPa from 1200 - 1400 °C to 1750 °C; during the cooling process, the pressure is maintained at 5 - 15 MPa from 1150 - 1250 °C to room temperature.

[0017] In some embodiments of the present invention, the preparation process of the high-entropy carbide is as follows:

[0018] Five carbide powders are respectively added to anhydrous ethanol (dispersion solvent) containing polyethylene glycol (dispersion medium) to make five carbide suspensions. The five carbide suspensions are mixed under the conditions of mechanical stirring and ultrasonic dispersion to obtain a high-entropy carbide suspension, which is ball-milled, dried, dry-milled, dispersed and then dried and sieved to obtain high-entropy carbide powder.

[0019] Preferably, the five carbide powders are submicron powders. Further preferably, the powder particle size is 0.3 - 0.6 μm.

[0020] Preferably, the ball-milling time is 15 - 25 h; the dry-milling time is 1 - 5 h. During dry-milling, it can be carried out in the way of milling for 5 min and stopping for 2 min.

[0021] In some embodiments of the present invention, the preparation process of the high-entropy alloy is as follows:

[0022] Five metal powders are respectively added to anhydrous ethanol (dispersion solvent) containing polyethylene glycol (dispersion medium) to make five metal powder suspensions. The five metal powder suspensions are mixed under the conditions of mechanical stirring and ultrasonic dispersion to obtain a high-entropy alloy suspension, and then ball-milled, dried and sieved to obtain high-entropy alloy powder.

[0023] Preferably, the five metal powders are submicron powders. Preferably, the powder particle size is 0.3 - 0.6 μm.

[0024] Preferably, the ball-milling time is 20 - 30 h.

[0025] In some embodiments of the present invention, aluminum oxide is submicron powder. Preferably, the powder particle size is 0.3 - 0.6 μm.

[0026] In some embodiments of the present invention, zirconia is nanometer powder. Preferably, the powder particle size is 80 - 120 nm.

[0027] In some embodiments of the present invention, the preparation process of each layer of powder is as follows:

[0028] Graphene is configured into a suspension and heated and ultrasonically treated for standby; zirconia is configured into a suspension and heated and ultrasonically treated for standby;

[0029] Mix aluminum oxide powder, high-entropy carbide powder, high-entropy alloy powder, graphene suspension and zirconia suspension respectively according to the raw material ratio of each layer of the five-layer symmetric layer structure, heat and ultrasonically treat to obtain each gradient layer powder suspension, ball mill, and sieve after drying to obtain each gradient layer powder.

[0030] In some embodiments of the present invention, in the graphene suspension, the dispersing solvent is anhydrous ethanol, and the dispersant adopts a compound dispersant (polyethylene glycol: polyvinylpyrrolidone = 1:1), and its dosage is 80% of the mass of graphene.

[0031] In some embodiments of the present invention, in the nano-zirconia suspension, the dispersing solvent is anhydrous ethanol, and the dispersant is polyethylene glycol, and its dosage is 0.5% - 1.5% of the mass of nano-zirconia.

[0032] In some embodiments of the present invention, the layer thickness ratio is 0.312. The layer thickness ratio in the present invention is based on the square of the golden ratio and refers to the ratio of the thickness of adjacent layers, that is, the surface layer thickness / transition layer thickness, transition layer thickness / core layer thickness.

[0033] The high-entropy composite toughened gradient ceramic tool material prepared by the present invention has high hardness and high toughness, and improves the adaptability and resistance of ceramic tools to high-speed cutting.

[0034] Therefore, in the third aspect of the present invention, there is provided an application of the above-mentioned high-entropy composite toughened gradient ceramic tool material or the high-entropy composite toughened gradient ceramic tool material obtained by the above-mentioned preparation method in the preparation of high-speed cutting tools.

[0035] The beneficial effects of the present invention are as follows:

[0036] The present invention discloses a high-entropy composite toughening gradient ceramic cutting tool material, which has a symmetric five-layer structure, namely a surface layer, a transition layer, a core layer, a transition layer and a surface layer in sequence; the surface layer includes 85-91 parts by mass of aluminum oxide and 9-15 parts by mass of high-entropy carbide; the transition layer includes 82.8-90.8 parts by mass of aluminum oxide, 6-12 parts by mass of high-entropy carbide, 3-5 parts by mass of zirconia and 0.2 part by mass of graphene; the core layer includes 82-91 parts by mass of aluminum oxide, 3-9 parts by mass of high-entropy carbide and 6-9 parts by mass of high-entropy alloy. In the present invention, high-entropy carbide and high-entropy alloy are used as performance-enhancing phases of the ceramic cutting tool. Through the reasonable gradient configuration of high-entropy materials in different gradient layers, the thermal stress relief and surface residual compressive stress characteristics of the gradient structure are organically combined with various toughening mechanisms introduced by graphene high-entropy composite, realizing the synchronous improvement of the hardness, toughness and wear resistance of the ceramic cutting tool material, and significantly improving the adaptability and resistance of the ceramic cutting tool to high-speed cutting. Specifically, cubic high-entropy carbide is introduced into the surface layer of the present invention, which can significantly improve the hardness and wear resistance of the tool material to meet the requirements of high wear resistance of the rake face of the tool for high-speed cutting; on the basis of introducing high-entropy carbide into the transition layer, a designed content of nano-zirconia and graphene is introduced, which significantly improves the toughness of the tool transition layer on the basis of high wear resistance and effectively inhibits the crack from expanding into the tool interior; by introducing high-entropy carbide and high-entropy alloy into the core layer at the same time, the overall strength and toughness of the ceramic cutting tool material can be greatly improved to meet the requirements of high anti-destructive performance of the tool for high-speed cutting. By designing a high-entropy composite toughening gradient ceramic cutting tool material with a specific structure, the present invention organically combines the thermal stress relief and surface residual compressive stress characteristics of the gradient structure with various toughening mechanisms introduced by graphene high-entropy composite. The content of high-entropy carbide decreases from the surface to the inside, and the total content of oxide and high-entropy alloy increases, which can ensure the formation of residual compressive stress on the surface layer of the ceramic cutting tool material, thus significantly improving the fatigue resistance of the tool and significantly improving the adaptability and resistance of the tool to high-speed cutting.

[0037] The preparation process of the high-entropy composite toughening gradient ceramic cutting tool material of the present invention is simple and very suitable for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The specification drawings forming a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention.

[0039] Figure 1 It is a sectional view of the gradient layer of the high-entropy composite toughening gradient ceramic cutting tool material of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0040] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with specific embodiments.

[0041] Example 1

[0042] (1) Take HfC, NbC, TaC, TiC, and ZrC carbide powders with a particle size of 0.4μm as raw materials and mix them in an equal molar ratio. Use anhydrous ethanol as the dispersion solvent and polyethylene glycol as the dispersion medium to prepare five carbide suspensions respectively, and heat them in a water bath at 100℃ for ultrasonic dispersion for 1h. Under mechanical stirring and ultrasonic dispersion, the five carbide suspensions are mixed and ultrasonic dispersion is continued for 1h. Add grinding balls according to a certain ball-to-material ratio (20:1), ball mill for 20h, then dry in a vacuum drying oven (80℃), and sieve to obtain a carbide mixed powder. Dry grind the above mixed powder for 2h (grind for 5 minutes, stop for 2 minutes), then add anhydrous ethanol for ultrasonic dispersion for 30 minutes, dry and sieve to obtain high entropy carbide powder.

[0043] (2) Take five kinds of metal powders of Fe, Co, Ni, Cr and Mn with a particle size of 0.4μm as raw materials and mix them in equal molar ratios. Use anhydrous ethanol as the dispersion solvent and polyethylene glycol as the dispersion medium to prepare five kinds of metal suspensions respectively, and heat them in a water bath at 100℃ for ultrasonic dispersion for 1h. Under mechanical stirring and ultrasonic dispersion, the five kinds of metal suspensions are mixed to obtain a high entropy alloy suspension, and ultrasonic dispersion is continued for 1h. Grinding balls are added according to a certain ball-to-material ratio (20:1), ball milled for 24h, and then dried in a vacuum drying oven (80℃), and sieved to obtain well-dispersed high entropy alloy powder.

[0044] (3) Graphene was dispersed using anhydrous ethanol as the dispersion solvent, and a composite dispersant (polyethylene glycol: polyvinyl pyrrolidone = 1:1, molar ratio) of 80% relative to the mass of graphene was added to prepare a suspension, which was then heated in a water bath at 100°C and ultrasonically dispersed for 60 min; nano ZrO 2 Anhydrous ethanol is used as the dispersion solvent, and relatively nano ZrO 2 The particles were prepared into a suspension with 1.0% polyethylene glycol and then ultrasonically dispersed in a 100°C water bath for 30 minutes.

[0045] (4) The high entropy carbide powder of step (1), the high entropy alloy powder of step (2), and Al with a particle size of 0.5 μm are used. 2 O 3 、ZrO with a particle size of 100nm 2 and graphene as raw materials, the proportions of each layer are as follows by weight:

[0046] Surface: Al 2 O 3 91 parts, high entropy carbide 9 parts;

[0047] Transition layer: Al 2 O 3 ​​90.8 parts, high entropy carbide 6 parts, ZrO 2 3 parts, graphene 0.2 parts;

[0048] Core layer: Al 2 O 3 91 parts, 3 parts of high entropy carbide, 6 parts of high entropy alloy.

[0049] (5) Al 2 O 3 The powder, high entropy carbide powder of step (1), high entropy alloy powder of step (2), graphene suspension obtained in step (3) and nano zirconium dioxide suspension are mixed according to the proportion of step (4), and ultrasonically dispersed in a water bath at 100°C for 30 minutes to obtain the powder suspension of each gradient layer. Grinding balls are added according to a certain ball-to-material ratio (20:1), ball-milled for 24 hours, and then dried in a vacuum drying oven (80°C), and sieved to obtain well-dispersed powders of each gradient layer.

[0050] (6) Adopt liquid phase + solid phase two-step spark plasma sintering process:

[0051] The vacuum degree is kept below 10Pa, the temperature is raised to 1700℃ at 150℃ / min, kept at this temperature for 3min, then cooled to 1500℃ at 150℃ / min, kept at this temperature for 2h, and then cooled with the furnace; during the heating process, the pressure is kept at 20MPa from room temperature to 1200℃, and at 50MPa from 1200-1700℃; during the cooling process, the pressure is kept at 10MPa from 1200℃ to room temperature.

[0052] After the sintering process is completed, a high-entropy composite toughening gradient ceramic tool material with high hardness and high toughness can be obtained. Its mechanical properties are: Vickers hardness 22.9GPa, bending strength 1129.4MPa, fracture toughness 11.7MPa·m 1 / 2 .

[0053] Example 2

[0054] (1) Take HfC, WC, TaC, TiC, and ZrC carbide powders with a particle size of 0.5μm as raw materials and mix them in an equal molar ratio. Use anhydrous ethanol as the dispersion solvent and polyethylene glycol as the dispersion medium to prepare five carbide suspensions respectively, and heat them in a water bath at 100℃ for ultrasonic dispersion for 1h. Under mechanical stirring and ultrasonic dispersion, the five carbide suspensions are mixed and ultrasonic dispersion is continued for 1h. Add grinding balls according to a certain ball-to-material ratio (20:1), ball mill for 20h, then dry in a vacuum drying oven (80℃), and sieve to obtain a carbide mixed powder; dry-grind the above mixed powder for 2h (grind for 5 minutes, stop for 2 minutes), then add anhydrous ethanol for ultrasonic dispersion for 30 minutes, dry and sieve to obtain high entropy carbide powder. ​​

[0055] (2) Take five kinds of metal powders of Fe, Co, Ni, Cr and Al with a particle size of 0.5μm as raw materials and mix them in equal molar ratios. Use anhydrous ethanol as the dispersion solvent and polyethylene glycol as the dispersion medium to prepare five kinds of metal suspensions respectively, and heat them in a water bath at 100℃ for ultrasonic dispersion for 1h. Under mechanical stirring and ultrasonic dispersion, the five kinds of metal suspensions are mixed to obtain a high entropy alloy suspension, and ultrasonic dispersion is continued for 1h. Grinding balls are added according to a certain ball-to-material ratio (20:1), ball milled for 24h, and then dried in a vacuum drying oven (80℃), and sieved to obtain well-dispersed high entropy alloy powder.

[0056] (3) Graphene was dispersed using anhydrous ethanol as the dispersion solvent, and a composite dispersant (polyethylene glycol: polyvinyl pyrrolidone = 1:1, molar ratio) of 80% relative to the mass of graphene was added to prepare a suspension, which was then heated in a water bath at 100°C and ultrasonically dispersed for 60 min; nano ZrO 2 Anhydrous ethanol is used as the dispersion solvent, and relatively nano ZrO 2 The particles were prepared into a suspension with 1.0% polyethylene glycol and then ultrasonically dispersed in a 100°C water bath for 30 minutes.

[0057] (4) The high entropy carbide powder of step (1), the high entropy alloy powder of step (2), and Al with a particle size of 0.5 μm are used. 2 O 3 、ZrO with a particle size of 100nm 2 and graphene as raw materials, the proportions of each layer are as follows by weight:

[0058] Surface: Al 2 O 3 85 parts, high entropy carbide 15 parts;

[0059] Transition layer: Al 2 O 3 82.8 parts, high entropy carbide 12 parts, ZrO 2 5 parts, graphene 0.2 parts;

[0060] Core layer: Al 2 O 3 82 parts, high entropy carbide 9 parts, high entropy alloy 9 parts.

[0061] (5) Al 2 O 3 ​​​​The powder, high entropy carbide powder of step (1), high entropy alloy powder of step (2), graphene suspension obtained in step (3) and nano zirconium dioxide suspension are mixed according to the proportion of step (4), and ultrasonically dispersed in a water bath at 100°C for 30 minutes to obtain the powder suspension of each gradient layer. Grinding balls are added according to a certain ball-to-material ratio (20:1), ball-milled for 24 hours, and then dried in a vacuum drying oven (80°C), and sieved to obtain well-dispersed powders of each gradient layer.

[0062] (6) Adopt liquid phase + solid phase two-step spark plasma sintering process:

[0063] The vacuum degree is kept below 10Pa, the temperature is raised to 1725℃ at 150℃ / min, kept at this temperature for 3min, then cooled to 1500℃ at 150℃ / min, kept at this temperature for 2h, and then cooled with the furnace; during the heating process, the pressure is kept at 20MPa from room temperature to 1200℃, and at 50MPa from 1200-1725℃; during the cooling process, the pressure is kept at 10MPa from 1200℃ to room temperature.

[0064] After the sintering process is completed, a high-entropy composite toughening gradient ceramic tool material with high hardness and high toughness can be obtained. Its mechanical properties are: Vickers hardness 22.4GPa, bending strength 1156.3MPa, fracture toughness 11.9MPa·m 1 / 2 .

[0065] Example 3

[0066] (1) Take TaC, NbC, TiC, WC, and VC carbide powders with a particle size of 0.5μm as raw materials and mix them in an equal molar ratio. Use anhydrous ethanol as the dispersion solvent and polyethylene glycol as the dispersion medium to prepare five carbide suspensions respectively, and heat them in a water bath at 100℃ for ultrasonic dispersion for 1h. Under mechanical stirring and ultrasonic dispersion, the five carbide suspensions are mixed and ultrasonic dispersion is continued for 1h. Add grinding balls according to a certain ball-to-material ratio (20:1), ball mill for 20h, then dry in a vacuum drying oven (80℃), and sieve to obtain a carbide mixed powder; dry-grind the above mixed powder for 2h (grind for 5 minutes, stop for 2 minutes), then add anhydrous ethanol for ultrasonic dispersion for 30 minutes, dry and sieve to obtain high entropy carbide powder.

[0067] (2) Take five kinds of metal powders of Fe, Co, Ni, Cr and Mn with a particle size of 0.5μm as raw materials and mix them in equal molar ratios. Use anhydrous ethanol as the dispersion solvent and polyethylene glycol as the dispersion medium to prepare five kinds of metal suspensions respectively, and heat them in a water bath at 100℃ for ultrasonic dispersion for 1h. Under mechanical stirring and ultrasonic dispersion, the five kinds of metal suspensions are mixed to obtain a high entropy alloy suspension, and ultrasonic dispersion is continued for 1h. Add grinding balls according to a certain ball-to-material ratio (20:1), ball mill for 24h, and then dry in a vacuum drying oven (80℃), and sieve to obtain well-dispersed high entropy alloy powder.

[0068] (3) Graphene was dispersed using anhydrous ethanol as the dispersion solvent, and a composite dispersant (polyethylene glycol: polyvinyl pyrrolidone = 1:1, molar ratio) of 80% relative to the mass of graphene was added to prepare a suspension, which was then heated in a water bath at 100°C and ultrasonically dispersed for 60 min; nano ZrO 2 Anhydrous ethanol is used as the dispersion solvent, and relatively nano ZrO 2 The particles were prepared into a suspension with 1.0% polyethylene glycol and then ultrasonically dispersed in a 100°C water bath for 30 minutes.

[0069] (4) The high entropy carbide powder of step (1), the high entropy alloy powder of step (2), and Al with a particle size of 0.4 μm are used. 2 O 3 、ZrO with a particle size of 100nm 2 and graphene as raw materials, the proportions of each layer are as follows by weight:

[0070] Surface: Al 2 O 3 88 parts, high entropy carbide 12 parts;

[0071] Transition layer: Al 2 O 3 87.8 parts, high entropy carbide 9 parts, ZrO 2 3 parts, graphene 0.2 parts;

[0072] Core layer: Al 2 O 3 89 parts, high entropy carbide 6 parts, high entropy alloy 5 parts.

[0073] (5) Al 2 O 3 ​​​​The powder, the high-entropy carbide powder in step (1), the high-entropy alloy powder in step (2), the prepared graphene suspension and nano-zirconia suspension are mixed according to the ratio in step (4), and ultrasonically dispersed in a water bath at 100 °C for 30 min to obtain the powder suspension of each gradient layer. Grinding balls are added according to a certain ball-to-material ratio (20:1), ball-milled for 24 h, then dried in a vacuum drying oven (80 °C), and sieved to obtain the well-dispersed powder of each gradient layer.

[0074] (6) Adopt the two-step spark plasma sintering process of liquid phase + solid phase:

[0075] The vacuum degree is maintained below 10 Pa, heated to 1725 °C at 150 °C / min, held for 5 min, then cooled to 1500 °C at 150 °C / min, held for 1.5 h, and then cooled with the furnace; during the heating process, the pressure is maintained at 20 MPa from room temperature to 1200 °C, and at 50 MPa from 1200 - 1700 °C; during the cooling process, the pressure is maintained at 10 MPa from 1200 °C to room temperature.

[0076] After the above sintering procedure runs to completion, a high-entropy composite toughened gradient ceramic tool material with high hardness and high strength and toughness can be obtained, and its mechanical properties are: Vickers hardness 22.7 GPa, flexural strength 1201.7 MPa, fracture toughness 11.5 MPa·m 1 / 2 .

[0077] Comparative Example 1

[0078] The difference from Example 1 is that it does not contain nano-zirconia.

[0079] After the sintering procedure runs to completion, the mechanical properties of the obtained high-entropy composite toughened gradient ceramic tool material are: Vickers hardness 20.8 GPa, flexural strength 1072.5 MPa, fracture toughness 10.1 MPa·m 1 / 2 .

[0080] Comparative Example 2

[0081] The difference from Example 1 is that it does not contain graphene.

[0082] After the sintering procedure runs to completion, the mechanical properties of the obtained high-entropy composite toughened gradient ceramic tool material are: Vickers hardness 20.1 GPa, flexural strength 913.6 MPa, fracture toughness 8.9 MPa·m 1 / 2 .

[0083] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A high entropy composite toughening gradient ceramic tool material, characterized in that: The material has a symmetrical five-layer structure, which is a surface layer, a transition layer, a core layer, a transition layer and a surface layer in sequence; The surface layer comprises 85-91 parts of aluminum oxide and 9-15 parts of high entropy carbide by mass; The transition layer comprises, by mass, 82.8 to 90.8 parts of aluminum oxide, 6 to 12 parts of high entropy carbide, 3 to 5 parts of zirconium dioxide, and 0.2 parts of graphene; The core layer comprises 82-91 parts of aluminum oxide, 3-9 parts of high entropy carbide, and 6-9 parts of high entropy alloy by mass. Aluminum oxide is a submicron powder; zirconium dioxide is a nanometer powder; The high entropy carbide comprises any five of HfC, NbC, TaC, TiC, WC and ZrC in equal molar ratios; the five carbide powders are submicron powders; The high entropy alloy comprises any five of Fe, Co, Ni, Cr, Mn and Al in equal molar ratios; the five metal powders are submicron powders; The preparation process of high entropy carbide is as follows: five kinds of carbide powders are respectively added to anhydrous ethanol containing polyethylene glycol to prepare five kinds of carbide suspensions, the five kinds of carbide suspensions are mixed under the conditions of mechanical stirring and ultrasonic dispersion to obtain high entropy carbide suspensions, and high entropy carbide powders are obtained by ball milling, drying, dry grinding, and drying and sieving after dispersion; The preparation process of the high entropy alloy is as follows: five kinds of metal powders are respectively added to anhydrous ethanol containing polyethylene glycol to prepare five kinds of metal powder suspensions, the five kinds of metal powder suspensions are mixed under the conditions of mechanical stirring and ultrasonic dispersion to obtain a high entropy alloy suspension, and then ball milling, drying and sieving are performed to obtain high entropy alloy powder.

2. A method for preparing the high entropy composite toughening gradient ceramic tool material according to claim 1, characterized in that: The steps include: Each layer of powder is prepared according to the raw material ratio of each layer of the five-layer symmetrical layer structure, and each layer of powder is loaded by a layered paving method. The five-layer gradient powder is pressed into shape, and then two-step spark plasma sintering is performed to obtain the product.

3. The preparation method according to claim 2, characterized in that: The process of the two-step spark plasma sintering is as follows: the vacuum degree is kept below 10Pa, the temperature is raised to 1700-1750°C at 100-200°C / min, the temperature is kept for 1-5min, then the temperature is cooled to 1400-1600°C at 100-200°C / min, the temperature is kept for 1-6h, and then the furnace is cooled; during the heating process, the pressure is kept at 15-25MPa from room temperature to 1150-1250°C, and the pressure is kept at 45-55MPa from 1200-1400°C to 1750°C; during the cooling process, the pressure is kept at 5-15MPa from 1150-1250°C to room temperature.

4. The preparation method according to claim 2, characterized in that: The preparation process of high entropy carbide is as follows: five kinds of carbide powders are respectively added to anhydrous ethanol containing polyethylene glycol to prepare five kinds of carbide suspensions, the five kinds of carbide suspensions are mixed under the conditions of mechanical stirring and ultrasonic dispersion to obtain high entropy carbide suspensions, and high entropy carbide powders are obtained by ball milling, drying, dry grinding, and drying and sieving after dispersion.

5. The preparation method according to claim 4, characterized in that: The five carbide powders are submicron powders with a particle size of 0.3 to 0.6 μm.

6. The preparation method according to claim 2, characterized in that: The preparation process of the high entropy alloy is as follows: five kinds of metal powders are respectively added to anhydrous ethanol containing polyethylene glycol to prepare five kinds of metal powder suspensions, the five kinds of metal powder suspensions are mixed under the conditions of mechanical stirring and ultrasonic dispersion to obtain a high entropy alloy suspension, and then ball milling, drying and sieving are performed to obtain high entropy alloy powder.

7. The preparation method according to claim 6, characterized in that: The five metal powders are submicron powders with a powder particle size of 0.3 to 0.6 μm.

8. The preparation method according to claim 2, characterized in that: Aluminum oxide is a submicron powder with a particle size of 0.3 to 0.6 μm.

9. The preparation method according to claim 2, characterized in that: Zirconium dioxide is a nano-scale powder with a particle size of 80 to 120 nm.

10. The preparation method according to claim 2, characterized in that: The preparation process of each layer of powder is as follows: The graphene is configured into a suspension, and is heated and ultrasonically prepared; the zirconium dioxide is configured into a suspension, and is heated and ultrasonically prepared; Aluminum oxide powder, high entropy carbide powder, high entropy alloy powder, graphene suspension and zirconium dioxide suspension are mixed according to the raw material ratio of each layer of the five-layer symmetrical layer structure, heated and ultrasonically obtained to obtain powder suspensions of each gradient layer, ball milled, dried and sieved to obtain powders of each gradient layer.

11. The preparation method according to claim 2, characterized in that: The layer thickness ratio is 0.

312.

12. Use of the high entropy composite toughened gradient ceramic tool material according to claim 1 or the high entropy composite toughened gradient ceramic tool material obtained by the preparation method according to any one of claims 2 to 11 in the preparation of high-speed cutting tools.

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