A ceramic cutting tool with a core-shell structure and a preparation method thereof

Abstract

The present invention discloses a ceramic tool with a core-shell structure and a preparation method thereof, relating to the technical field of ceramic cutting tools. The ceramic tool with a core-shell structure provided by the present invention has a shell layer made of Sialon ceramic material and a core layer made of Si3N4 ceramic material; the content of α-Sialon phase in the Sialon ceramic material is 80-100%; the content of β-Si3N4 phase in the Si3N4 ceramic material is 80-100%; through the "core-shell" structure design, a α-Sialon-rich ceramic material with high hardness and low thermal expansion coefficient is used as the surface layer material of the tool to ensure excellent wear resistance of the rake face and flank face of the tool; a Si3N4 ceramic material with high toughness and high strength is used as the inner layer material of the tool to ensure high anti-destruction ability of the tool body. The preparation method provided by the present invention uses a multi-material light-curing additive manufacturing technology to prepare a Sialon-Si3N4 ceramic tool with a core-shell structure, which can realize the regulation of the shape accuracy and surface integrity of the tool, and finally prepare a tool with excellent performance.

Description

Technical Field

[0001] The present invention relates to the technical field of ceramic cutting tools, and particularly to a ceramic tool with a core-shell structure and a preparation method thereof. Background Art

[0002] Superalloy is a typical difficult-to-machine material, but it has a wide range of applications in fields with extremely harsh service conditions such as aviation, aerospace, oil and gas exploitation, and marine engineering equipment. When machining superalloy, a large cutting force and a very high cutting temperature will be generated, so the requirements for tool performance are extremely strict.

[0003] Sialon tools have excellent anti-edge wear ability and are widely used in rough machining and interrupted machining of superalloys. Their main failure forms are flank wear and rake face wear. Sialon ceramics are solid solutions of Si 3 N 4 and Al 2 O 3 including two structures: α-Sialon and β-Sialon. α-Sialon has a relatively high hardness, but its strength and toughness are too low to be used as a tool alone. The strength and toughness of β-Sialon tools are quite good, but the hardness is too low. The strength and fracture toughness of Si 3 N 4 are very excellent (both are much higher than β-Sialon), but the hardness is too low, and there is a chemical reaction with the iron in superalloy. Therefore, pure Si 3 N 4 tools cannot be used to machine IN718. Therefore, how to obtain a Sialon ceramic tool that combines high hardness, high strength and toughness, and good high-temperature chemical stability is the key to improving the tool life and significantly enhancing the machining efficiency of superalloys.

[0004] Currently, the methods for obtaining Sialon ceramic tools with both high hardness and high strength and toughness mainly include: (1) By controlling the ratio of α-Sialon and β-Sialon to balance their hardness and fracture toughness to achieve optimized cutting performance, but there are still problems of rapid wear when cutting superalloys; (2) Depositing wear-resistant and high-hardness coatings on the surface of Sialon ceramic tools to improve the wear resistance of the tools, but the coatings are prone to peeling off from the substrate under the action of cutting force, affecting the service life of the tools; (3) Adding ceramic particles to toughen and strengthen Sialon ceramic tools, but these fine particles are prone to agglomeration during the dispersion process, affecting the toughening and strengthening effect; (4) Introducing a gradient functional ceramic structure to enhance. For example, the European ceramic tool manufacturer CeramTec obtained a dual-phase gradient Sialon tool with an α-Sialon-rich surface and a β-Sialon-rich core by controlling the sintering and cooling rate in its Sialon tool products of the SPK series in

US Patents US#10239794B2 and US#7514383B2

Chinese Patent Publication No. CN102320170A

[0005] The technical problem to be solved by the present invention is how to obtain both good hardness and toughness through structural and compositional design to improve the service life of the tool and make it applicable to both rough machining and finish machining of superalloys to achieve the multi-functionalization of the tool.

[0006] To solve the above problems, the present invention proposes the following technical solutions:

[0007] In the first aspect, the present invention provides a ceramic tool with a core-shell structure, the outer shell layer of the ceramic tool is made of Sialon ceramic material, and the inner core layer is Si 3 N 4Ceramic material; among them, the α-Sialon phase content of the Sialon ceramic material is 80-100%; the Si 3 N 4 ceramic material has a β-Si 3 N 4 phase content of 80-100%; the proportion of the outer shell layer in the total volume of the tool is 14.1-78.4%, and the proportion of the inner core layer in the total volume of the tool is 21.6-85.9%.

[0008] A further technical solution thereof is that the thickness of the outer shell layer of the ceramic tool is 0.2-1.5 mm, and the thickness of each part of the outer shell layer is uniform, with an error within 0.1 mm.

[0009] It should be noted that the ceramic tool provided by the present invention has a standard shape and a "core-shell" structure, and its shape can be circular, square, equilateral triangle or rhombus, etc. The outer shell layer is made of Sialon ceramic material, which has high hardness and can improve the wear resistance of the tool; the inner core layer is made of Si 3 N 4 ceramic material, which has high toughness and high strength and can improve the impact resistance of the tool; the combination of the "core-shell" structure can improve the service life of the tool and expand the use of the tool.

[0010] A further technical solution thereof is that the Sialon ceramic material is sintered from 85-99 parts by weight of Sialon powder and 1-15 parts by weight of a first sintering aid;

[0011] The Si 3 N 4 ceramic material is sintered from 80-99 parts by weight of Si 3 N 4 powder and 1-20 parts by weight of a second sintering aid, and the α-Si 3 N 4 phase content of the Si 3 N 4 powder is 80-100%, and the particle size is 0.1-5 μm.

[0012] A further technical solution thereof is that in the Sialon powder, by mass fraction, it is composed of 50-80% of Si 3 N 4 powder, 10-20% of AlN powder and 2-5% of Al 2 O 3 powder, and the α-Si 3 N 4 phase content of the Si 3 N 4The phase content is 90-99%, and the particle size is 0.1-5 μm; the particle size of the AlN powder is 0.8-1.5 μm; the particle size of the Al 2 O 3 powder is 0.1-5.5 μm.

[0013] A further technical solution thereof is that the first sintering aid is selected from Y 2 O 3 , Sm 2 O 3 , Yb 2 O 3 , Er 2 O 3 , La 2 O 3 , Dy 2 O 3 or several of them, and the particle size is preferably 0.2-10 μm; the second sintering aid is selected from Al 2 O 3 , MgO, TiO 2 , Re 2 O 3 or more of them; wherein, Re is one or more of Y, Sc, La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Er, Yb, Lu, and the particle size is preferably 0.2-10 μm.

[0014] Second, the present invention provides a method for preparing a ceramic tool with a core-shell structure by using a photocuring technology, including the following steps:

[0015] S1. Prepare the powder:

[0016] Prepare the Sialon ceramic powder: Take 85-99 parts by weight of Sialon powder, 1-15 parts by weight of the first sintering aid, and 0.25-3 parts by weight of the surface modifier and add them to a solvent for ball milling. After the ball milling is completed, dry the solvent and sieve it;

[0017] Prepare the Si 3 N 4 ceramic powder: Take 80-99 parts by weight of Si 3 N 4 powder, 1-20 parts by weight of the second sintering aid, and 0.25-3 parts by weight of the surface modifier and add them to a solvent for ball milling. After the ball milling is completed, dry the solvent and sieve it;

[0018] S2. Prepare the slurry: Respectively mix the Sialon ceramic powder and Si 3 N 4 ceramic powder prepared in step S1 with a photosensitive resin, a photoinitiator, and a dispersant to be uniformly mixed to obtain a Sialon ceramic slurry and Si 3 N4 Ceramic slurry; the Sialon ceramic slurry and Si 3 N 4 The solid phase content of the ceramic slurry is the same, being 40 - 60 vol%;

[0019] S3. Printing the tool: Place the Sialon ceramic slurry and the Si 3 N 4 ceramic slurry in different trays of a multi - material stereolithography printer respectively. After slicing the tool model according to the tool design shape, layer - by - layer printing and curing are carried out to obtain a green body;

[0020] S4. Debinding: Carry out vacuum debinding and air debinding on the green body;

[0021] S5. Sintering: Sinter the green body after debinding to obtain a sintered body;

[0022] S6. Post - treatment: Carry out hot isostatic pressing on the sintered body to obtain a ceramic tool with a core - shell structure. The temperature of the hot isostatic pressing is 50 - 200 °C lower than the sintering temperature.

[0023] Its further technical solution is that the α - Sialon phase content of the Sialon ceramic material is 80 - 100%; the β - Si 3 N 4 ceramic material has a β - Si 3 N 4 phase content of 80 - 100%;

[0024] The first sintering aid is selected from one or more of Y 2 O 3 、Sm 2 O 3 、Yb 2 O 3 、Er 2 O 3 、La 2 O 3 、Dy 2 O 3 ;

[0025] The second sintering aid is selected from one or more of Al 2 O 3 、MgO、TiO 2 、Re 2 O 3 ; where Re is one or more of Y, Sc, La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Er, Yb, Lu;

[0026] The surface modifier is selected from one or more of KH550, KH560, KH570, oleic acid, and stearic acid.

[0027] A further technical solution thereof is that in the step S1, the solvent is anhydrous ethanol, the grinding balls are silicon nitride, and the powder (including the sintering aid), anhydrous ethanol, and silicon nitride grinding balls are ball-milled and mixed evenly according to a mass ratio of 1:2:2. The rotation speed is 100 - 400 rpm, and the ball-milling time is 1 - 12 h. The mixed powder suspension is placed in an oven at 50 - 100 °C to dry the anhydrous ethanol. The dried powder passes through a 100-mesh sieve to obtain the required Sialon ceramic powder and Si 3 N 4 ceramic powder.

[0028] A further technical solution thereof is that the addition amount of the photoinitiator is 0.5 - 3% of the mass of the photosensitive resin; the addition amount of the dispersant is 0.25 - 3% of the mass of the powder.

[0029] It should be noted that in the present invention, the solid content and viscosity of the Sialon ceramic slurry and the Si 3 N 4 ceramic slurry should be kept consistent to avoid problems such as printing accuracy problems and inconsistent sintering shrinkage rates in the later stage. In addition, the solid content and viscosity of the slurry can be adjusted by adding the content of the dispersant.

[0030] A further technical solution thereof is that in the step S2, the photosensitive resin is selected from one or more of HDDA, PPTTA, TMPTA, and BPA2EODMA; the photoinitiator is one or two of Irgacure819 and Irgacure369; the dispersant is one or more of SOLSPERSE-24000, KOS-110, BYK-110, BYK-111, BYK-9076, BYK-163, and BYK-9077.

[0031] It should be noted that in order to make the ceramic slurry solid-liquid dispersed evenly, the Sialon ceramic powder and Si 3 N 4 ceramic powder prepared in S1 can be respectively mixed with the photosensitive resin, photoinitiator, and dispersant on a homogenizer at a rotation speed of 1000 - 3000 rpm for 1 - 5 min to obtain the required Sialon ceramic slurry and Si 3 N 4 ceramic slurry.

[0032] A further technical solution thereof is that the printing parameters in the step S3 are that the light source wavelength is 405 nm, and the ultraviolet light power density is 10 - 20 mW / cm 2, the single-layer exposure time is 5 - 25 s, and the slice thickness is 10 - 50 μm.

[0033] It should be noted that in the step S3, after slicing the ceramic tool model according to the designed shape of the tool, layer-by-layer printing is performed, and the printing mode is selected according to the materials included in the slice. For example, the first layer of the slice is the Sialon ceramic material of the outer shell layer, and only the Sialon ceramic material is printed during printing; when printing to the nth layer of the slice, if both Sialon ceramic material and Si 3 N 4 ceramic material appear in the same layer, first print the Sialon ceramic material, then scrub the slurry on the printing platform, transfer the printing platform to the material tank 2, and then print Si 3 N 4 ceramic material to complete the printing of the nth layer, and repeat this process to complete the printing of the complete ceramic tool (the printing process is as Figure 2 shown).

[0034] A further technical solution is that in the step S4, a debinding method combining vacuum debinding and air debinding is adopted. The green body is placed in an alumina crucible, first placed in a vacuum debinding furnace for debinding, and then put into an air furnace to remove residual carbon. The specific process is as follows: Vacuum debinding: The temperature is raised at a rate of 0.5 - 5 °C / min to 200 - 400 °C, held for 1 - 5 h, then raised at a rate of 0.5 - 5 °C / min to 550 - 650 °C and held for 1 - 5 h, and finally cooled to room temperature at a rate of 0.5 - 3 °C / min. Air debinding: The temperature is raised at a rate of 0.5 - 5 °C / min to 400 - 600 °C, held for 1 - 5 h, and finally cooled to room temperature at a rate of 0.5 - 3 °C / min.

[0035] A further technical solution is that in the step S5, it also includes placing the debound green body into a boron nitride crucible and burying it in a mixed powder of Si 3 N 4 :BN:AlN with a mass ratio of 5 - 7:2 - 4:1, and then placing it in a sintering furnace for sintering.

[0036] A further technical solution is that in the step S5, the sintering process is as follows: The temperature is raised at a rate of 5 - 20 °C / min to 1400 - 1600 °C and held for 1 - 3 h, then raised at a rate of 3 - 10 °C / min to 1700 - 1850 °C and held for 1 - 5 h, and finally cooled to 1200 °C at a rate of 5 - 10 °C / min, and then cooled to room temperature with the furnace.

[0037] It should be noted that in the step S5, the sintering method can be pressureless sintering (PS) or gas pressure sintering (GPS), and the inert gas used is N 2or Ar; In particular, the atmospheric pressure during pressure sintering is 1 to 10 MPa.

[0038] It should be noted that in step S6, the temperature of hot isostatic pressing is 50 to 200 °C lower than the sintering temperature (1700 to 1850 °C). The sintering temperature refers to the highest sintering temperature. In the present invention, the specific temperature range of hot isostatic pressing is 1500 to 1800 °C, with heat preservation for 0.5 to 4 h, and the nitrogen partial pressure is 50 to 200 MPa.

[0039] Compared with the prior art, the technical effects that the present invention can achieve include:

[0040] The ceramic tool with a core-shell structure provided by the present invention, the outer shell layer of the ceramic tool is made of Sialon ceramic material, and the inner core layer is Si 3 N 4 ceramic material; wherein, the content of α-Sialon phase in the Sialon ceramic material is 80 to 100%; the Si 3 N 4 ceramic material has a β-Si 3 N 4 phase content of 80 to 100%; by designing the "core-shell" structure of the ceramic tool, using a α-Sialon-rich ceramic material with high hardness and low thermal expansion coefficient as the tool surface material to ensure excellent wear resistance of the rake face and flank face of the tool; using a Si 3 N 4 ceramic material with high toughness and high strength as the inner layer material of the tool to ensure high anti-destruction ability of the tool body.

[0041] Furthermore, based on the "core-shell" structure design of the ceramic tool in the present invention, the thickness of the outer shell layer is adjustable. After the tool face is worn, the worn part can be polished to make the worn part repaired to be flat and smooth for the purpose of reuse. Compared with the laminated gradient ceramic tool and the coated tool, the problem that the traditional ceramic tool cannot be reused after the tool face is worn is solved, the service life of the tool is increased, and the cost is reduced.

[0042] The method for preparing a ceramic tool with a core-shell structure by using a photocuring technology provided by the present invention, by using a multi-material photocuring additive manufacturing technology to prepare a core-shell structured Sialon-Si 3 N 4Ceramic cutting tools can achieve the regulation of cutting tool shape accuracy (shape control) and surface integrity (controllability), and finally produce cutting tools with excellent performance, solving the problem that traditional molding methods cannot produce "core-shell" structure cutting tools. Compared with the current dual-phase gradient Sialon cutting tools that are rich in α-Sialon phase on the surface and rich in β-Sialon phase in the core by controlling the sintering cooling rate, the preparation method of the present invention can be more conducive to controlling the thickness, uniformity and proportion of the surface α-Sialon phase, bringing great benefits in ensuring the consistency of manufactured products, reducing the cost of later processing, and promoting its mass production. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 A schematic diagram of a ceramic tool with a core-shell structure provided in Example 1 of the present invention, Figure 1 In the figure, 1 is the outer shell layer Sialon ceramic material, 2 is the inner core layer Si 3 N 4 Ceramic materials;

[0044] Figure 2 A schematic diagram of the printing process in the method for preparing a ceramic cutting tool with a core-shell structure by using a photocuring technology provided by the present invention;

[0045] Figure 3 XRD of the outer core layer material of the ceramic tool with a core-shell structure provided in Example 1 of the present invention;

[0046] Figure 4 XRD of the inner core layer material of the ceramic tool with a core-shell structure provided in Example 1 of the present invention. DETAILED DESCRIPTION

[0047] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments. Obviously, the embodiments described below are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0048] It should be understood that when used in this specification and the appended claims, the terms "include" and "comprises" indicate the presence of described features, integers, steps and / or operations, but do not exclude the presence or addition of one or more other features, integers, steps, operations and / or groups thereof.

[0049] It should also be understood that the terms used in the specification of the embodiments of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the embodiments of the present invention. As used in the specification of the embodiments of the present invention and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to include the plural forms.

[0050] The raw materials used in the embodiments and comparative examples of the present invention are all commercially available or self-made.

[0051] Example 1

[0052] The embodiments of the present invention provide a ceramic tool with a core-shell structure and a preparation method thereof. The shape of the tool is a standard circle. The final dimensions of the tool are a diameter of 12.70 mm and a length of 4.76 mm. The thickness of the shell material is 0.5 mm. For a schematic diagram, see Figure 1 . The steps of the specific preparation method are as follows:

[0053] S1. Mixing of powders.

[0054] (1) Mixing of Sialon ceramic powders: Weigh 71.84 g of Si 3 N 4 powders with a particle size of 0.7 μm, 16.29 g of AlN powders with a particle size of 1 μm, and 2.53 g of Al 2 O 3 powders as raw materials and place them in a ball milling tank. The α-Si 3 N 4 phase content of the Si 3 N 4 powders is 90-99%. Then weigh 9.34 g of Y 2 O 3 with a particle size of 0.5 μm as a sintering aid, add 200 g of absolute ethanol and 200 g of silicon nitride grinding balls, and then add 1 g of silane coupling agent KH570 as a powder surface modifier. Ball mill at a rotation speed of 350 rpm for 4 h. Place the mixed powder suspension in an oven at 50 °C to dry the absolute ethanol. The dried powder is passed through a 100-mesh sieve to obtain the required Sialon ceramic powder.

[0055] (2) Mixing of Si 3 N 4 ceramic powders: Weigh 90 g of Si 3 N 4 powders with a particle size of 0.7 μm and place them in a ball milling tank. The α-Si 3 N 4 phase content of the Si 3 N 4 powders is 80-100%. Then weigh 6 g of Y2 O 3 and 4 g of Al powder with a particle size of 0.2 μm 2 O 3 powder was used as a sintering aid, 200 g of absolute ethanol and 200 g of silicon nitride grinding balls were added, and then 1 g of silane coupling agent KH570 was added as a powder surface modifier. The ball milling was carried out at a rotation speed of 350 rpm for 4 h. The mixed powder suspension was placed in an oven at 50 °C to dry the absolute ethanol. The dried powder was passed through a 100-mesh sieve to obtain the required Si 3 N 4 ceramic powder.

[0056] S2. Preparation of ceramic slurry.

[0057] (1) Preparation of Sialon slurry: Weigh 72.3 g of Sialon ceramic powder, 27.7 g of photosensitive resin (HDDA, PPTTA, TMPTA, and BPA2EODMA mixed in a mass ratio of 1:1:1:1), 0.277 g of Irgacure819 photoinitiator, and 0.723 g of BYK-110 into a grinding jar and mix them on a homogenizer at a rotation speed of 2500 rpm for 2 min to obtain a Sialon ceramic slurry with a solid content of 45 vol% and a viscosity of 10.2 Pa·s (shear rate of 30 s -1 ).

[0058] (2) Preparation of Si 3 N 4 ceramic slurry: Weigh 71.49 g of Si 3 N 4 ceramic powder, 28.51 g of photosensitive resin (HDDA, PPTTA, TMPTA, and BPA2EODMA mixed in a mass ratio of 1:1:1:1), 0.285 g of Irgacure819 photoinitiator, and 0.858 g of BYK-110 into a grinding jar and mix them on a homogenizer at a rotation speed of 2500 rpm for 2 min to obtain a Si -1 ceramic slurry with a solid content of 45 vol% and a viscosity of 10.4 Pa·s (shear rate of 30 s 3 N 4 ceramic slurry.

[0059] S3. Printing of the tool. Place the Sialon ceramic slurry and Si 3 N 4 ceramic slurry in the trays 1 and 2 of a multi-material photocuring printer respectively. After slicing the "core-shell" functional ceramic tool model according to the tool design shape, layer-by-layer printing is carried out. The schematic diagram of the printing process is as Figure 2 . The printing process conditions are: the light source wavelength is 405 nm, and the ultraviolet light power density is 15 mW / cm2 For monolayer exposure, the exposure time is 8 s and the slice thickness is 20 μm.

[0060] S4. Degreasing. Place the printed ceramic tool blank with a core - shell structure in an alumina crucible. First, degrease it in a vacuum degreasing furnace and then remove the residual carbon in an air furnace. The specific process is as follows: Vacuum degreasing: Heat up at a rate of 0.5 °C / min to 380 °C, hold for 2 h, then heat up at a rate of 0.5 °C / min to 600 °C and hold for 4 h, and finally cool down to room temperature at a rate of 2 °C / min. Air degreasing: Heat up at a rate of 1 °C / min to 450 °C, hold for 4 h, and finally cool down to room temperature at a rate of 2 °C / min.

[0061] S5. Sintering. Place the degreased ceramic tool blank with a core - shell structure in a boron nitride crucible and bury it in a mixed powder of Si 3 N 4 :BN:AlN with a mass ratio of 6:3:1. Finally, place it in a sintering furnace and perform atmospheric pressure sintering under a N 2 protective atmosphere. The sintering process is as follows: Heat up at a rate of 15 °C / min to 1500 °C and hold for 1 h, then heat up at a rate of 5 °C / min to 1750 °C and hold for 3 h, and finally cool down to 1200 °C at a rate of 10 °C / min and cool down to room temperature with the furnace, obtaining a sintered body of a ceramic tool with a core - shell structure.

[0062] S6. Post - treatment. Place the sintered "core - shell" functional ceramic tool in a hot isostatic pressing furnace and perform heat treatment at a nitrogen pressure of 100 MPa and a temperature of 1700 °C for 2 h. Obtain a ceramic tool with a core - shell structure

[0063] The mechanical properties of the ceramic tool material with a core - shell structure prepared in this example are as follows: hardness 19.3 GPa, flexural strength 860 MPa, fracture toughness 6.8 MPa·m 1 / 2 . The phase of the outer shell layer material is α - Sialon, and the main phase of the inner core layer material is β - Si 3 N 4 , as characterized in Figure 3 and Figure 4 shown.

[0064] Example 2

[0065] Embodiment 2 of the present invention provides a ceramic tool with a core - shell structure and its preparation method. The shape of the tool is a standard circle, the final dimensions of the tool are a diameter of 12.70 mm and a length of 4.76 mm, and the thickness of the outer shell material is 0.5 mm.

[0066] The preparation method of this embodiment is different from that of embodiment 1 in that the sintering process of this embodiment is as follows: placing the degreased ceramic tool blank with a core-shell structure into a boron nitride crucible and burying Si 3 N 4 :BN:AlN mixed powder with a mass ratio of 6:3:1, and finally placed in a sintering furnace 2 Normal pressure sintering was performed under a protective atmosphere. The sintering process was as follows: heating to 1500°C at a rate of 15°C / min and keeping the temperature for 1 hour, then heating to 1800°C at a rate of 5°C / min and keeping the temperature for 3 hours, and finally cooling to 1200°C at a rate of 10°C / min, and cooling to room temperature with the furnace. The other preparation steps and dosage parameters of this embodiment are the same as those of Example 1.

[0067] The mechanical properties of the ceramic tool material with a core-shell structure prepared in this embodiment are: hardness 18.4 GPa, bending strength 956 MPa, fracture toughness 8.2 MPa·m 1 / 2 The outer shell material phase is 85.4% α-Sialon and 16.6% β-Sialon, while the inner core material phase is mainly β-Si 3 N 4 .

[0068] It can be seen from Examples 1 and 2 that the change in sintering temperature will change the ratio of the α-Sialon phase to the β-Sialon phase in the shell layer material. The increase in the β-Sialon phase will improve the toughness of the tool, but the hardness will also decrease accordingly.

[0069] Example 3

[0070] Embodiment 3 of the present invention provides a ceramic cutting tool with a core-shell structure and a preparation method thereof. The preparation process, materials and parameters are basically the same as those of Embodiment 1, except that the shape of the cutting tool in this embodiment is a standard circle, the final dimensions of the cutting tool are a diameter of 12.70 mm, a length of 4.76 mm, and a shell material thickness of 0.3 mm.

[0071] The mechanical properties of the ceramic tool material with core-shell structure prepared in this embodiment are: hardness 19.4GPa, bending strength 924MPa, fracture toughness 7.2MPa·m 1 / 2 The outer shell material phase is α-Sialon, and the inner core material phase is β-Si 3 N 4 .

[0072] It can be seen from Examples 1 and 3 that changing the thickness of the outer shell material will change the residual stress at the tool interface. In addition, since the thermal expansion coefficient of the outer shell Sialon material is small, and the inner core Si 3 N4 The thermal expansion coefficient of the material is large, and the residual stress formed is compressive stress, which is beneficial to the improvement of mechanical properties.

[0073] Example 4

[0074] Embodiment 4 of the present invention provides a ceramic tool with a core-shell structure and a preparation method thereof. The shape of the tool is a standard circle. The final dimensions of the tool are a diameter of 12.70 mm, a length of 4.76 mm, and a shell material thickness of 0.5 mm.

[0075] The preparation process of this embodiment is basically the same as that of embodiment 1, except that the composition of the Sialon ceramic powder is different. The composition and preparation process of the Sialon ceramic powder of this embodiment are as follows: 67.16 g of Si with a particle size of 0.7 μm is taken. 3 N 4 powder, 15.23g AlN powder with a particle size of 1μm, 2.37g Al 2 O 3 The powder is placed in a ball mill as the raw material and Si 3 N 4 α-Si powder 3 N 4 The phase content is 90-99%, and then 15.24g of Yb with a particle size of 0.5μm is weighed. 2 O 3 As a sintering aid, 200g of anhydrous ethanol and 200g of silicon nitride grinding balls were added, and then 1g of silane coupling agent KH570 was added as a powder surface modifier, with a rotation speed of 350rpm and a ball milling time of 4h. The mixed powder suspension was placed in an oven at 50℃ to dry the anhydrous ethanol, and the dried powder was passed through a 100-mesh sieve to obtain the desired Sialon ceramic powder.

[0076] The mechanical properties of the ceramic tool material with core-shell structure prepared in this embodiment are: hardness 19.6 GPa, bending strength 901 MPa, fracture toughness 7.5 MPa·m 1 / 2 The outer shell material phase is α-Sialon, and the inner core material phase is β-Si 3 N 4 .

[0077] It can be seen from Example 1 and Example 4 that by changing the formula of the outer shell layer material, and thus changing the mechanical properties of the outer shell layer Sialon material, the overall mechanical properties of the tool can also be improved by adjusting the material formula.

[0078] Example 5

[0079] Example 5 of the present invention provides a ceramic tool with a core-shell structure. The shape of the tool is a standard circle, and the final dimensions of the tool are a diameter of 12.70 mm and a length of 4.76 mm. The thickness of the outer shell material is 0.5 mm. The preparation process is basically the same as that of Example 1, except that the solid content of the Sialon ceramic slurry and the Si 3 N 4 ceramic slurry is 50 vol%.

[0080] The mechanical properties of the ceramic tool material with a core-shell structure prepared in this example are: hardness 20.1 GPa, flexural strength 901 MPa, and fracture toughness 7.1 MPa·m 1 / 2 。 The phase of the outer shell layer material is α-Sialon, and the main phase of the inner core layer material is β-Si 3 N 4 。

[0081] It can be seen from Example 1 and Example 5 that increasing the solid content of the outer shell layer material and the inner core layer material is beneficial to the improvement of mechanical properties.

[0082] Example 6

[0083] Example 6 of the present invention is a comparative example of Example 1. The shape of the tool is a standard circle, and the final dimensions of the tool are a diameter of 12.70 mm and a length of 4.76 mm. Weigh 71.84 g of Si powder with a particle size of 0.7 μm 3 N 4 powder, 16.29 g of AlN powder with a particle size of 1 μm, and 2.53 g of Al powder with a particle size of 0.2 μm 2 O 3 powder as the raw materials. The preparation process is basically the same as that of Example 1, except that the tool material in this example is not designed with a "core-shell" structure, and a single Sialon ceramic material is used to prepare the tool.

[0084] The mechanical properties of the obtained pure Sialon ceramic tool material are: hardness 19.6 GPa, flexural strength 550 MPa, and fracture toughness 4.5 MPa·m 1 / 2 。 The phase of the material is α-Sialon.

[0085] Example 7

[0086] Example 7 of the present invention is a comparative example of Example 1. The shape of the tool is a standard circle, and the final dimensions of the tool are a diameter of 12.70 mm and a height of 4.76 mm. The preparation process is basically the same as that of Example 1, except that the tool material in this example is not designed with a "core-shell" structure, and a single Si 3 N 4A cutting tool is prepared from a ceramic material, and the ceramic powder is Si powder with a particle size of 0.7 μm 3 N 4 powder, and the Si 3 N 4 content of the α-Si 3 N 4 phase in the powder is 80-100%.

[0087] The mechanical properties of the pure Si 3 N 4 ceramic cutting tool material prepared in this example are: hardness 15.4 GPa, flexural strength 820 MPa, fracture toughness 6.7 MPa·m 1 / 2 , and the material phase is β-Si 3 N 4 .

[0088] It can be seen from Example 6 and Example 7 that if a cutting tool is prepared solely from Sialon ceramic material or Si 3 N 4 ceramic material, the comprehensive mechanical properties of the obtained tool material are poor.

[0089] In the above embodiments, the descriptions of each embodiment have their own emphases. For parts not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0090] The above is the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of various equivalent modifications or substitutions, and these modifications or substitutions should all be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. A ceramic cutting tool with a core-shell structure, characterized in that, The outer shell layer of the ceramic tool is made of Sialon ceramic material, and the inner core layer is made of Si 3 N 4 ceramic material; wherein, the content of α-Sialon phase in the Sialon ceramic material is 80-100%; the Si 3 N 4 ceramic material has a β-Si 3 N 4 phase content of 80-100%; the proportion of the outer shell layer in the total volume of the tool is 14.1-78.4%, and the proportion of the inner core layer in the total volume of the tool is 21.6-85.9%; the preparation method of the ceramic cutting tool comprises the following steps: S1. Prepare the powder: Prepare the Sialon ceramic powder: Take 85-99 parts by weight of Sialon powder, 1-15 parts by weight of the first sintering aid, and 0.25-3 parts by weight of the surface modifier, add them to a solvent for ball milling, and after the ball milling is completed, dry the solvent and sieve it; Prepare Si 3 N 4 Ceramic powder: Add 80-99 parts by weight of Si 3 N 4 powder, 1-20 parts by weight of a second sintering aid, and 0.25-3 parts by weight of a surface modifier to a solvent and ball mill. After ball milling is completed, dry the solvent and screen it. S2. Preparation of slurry: Mix the Sialon ceramic powder and Si 3 N 4 ceramic powder prepared in step S1 with a photosensitive resin, a photoinitiator, and a dispersant uniformly to obtain a Sialon ceramic slurry and a Si 3 N 4 ceramic slurry; the solid phase contents of the Sialon ceramic slurry and the Si 3 N 4 ceramic slurry are the same, being 40 - 60 vol%. S3. Print the cutting tool: Place the Sialon ceramic slurry and the Si 3 N 4 ceramic slurry in different trays of a multi-material stereolithography printer respectively. After slicing the cutting tool model according to the designed shape of the cutting tool, print and cure layer by layer to obtain a green body; S4. Debinding: Carry out vacuum debinding and air debinding on the green body; S5. Sintering: Sinter the green body after debinding to obtain a sintered body; The sintering process is: Raise the temperature to 1400-1600 °C at a heating rate of 5-20 °C / min and hold for 1-3 h, then raise the temperature to 1700-1850 °C at a heating rate of 3-10 °C / min and hold for 1-5 h, and finally cool down to 1200 °C at a rate of 5-10 °C / min, and then cool in the furnace to room temperature; S6. Post-treatment: Carry out hot isostatic pressing treatment on the sintered body to obtain a ceramic cutting tool with a core-shell structure, and the temperature of the hot isostatic pressing treatment is 50-200 °C lower than the sintering temperature; the thickness of the outer shell layer of the ceramic cutting tool is 0.2-1.5 m; In the Sialon powder, by mass fraction, it consists of 50-80% of Si 3 N 4 powder, 10-20% of AlN powder and 2-5% of Al 2 O 3 powder, and the α-Si 3 N 4 phase content of the Si 3 N 4 powder is 90-99%; The first sintering aid is selected from Y 2 O 3 , Sm 2 O 3 , Yb 2 O 3 , Er 2 O 3 , La 2 O 3 , Dy 2 O 3 or one or more of them; The second sintering aid is selected from one or more of Al 2 O 3 , MgO, TiO 2 , Re 2 O 3 ; wherein, Re is one or more of Y, Sc, La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Er, Yb, Lu.

2. The ceramic cutting tool with a core-shell structure according to claim 1, characterized in that, the thickness of each part of the outer shell layer of the ceramic cutting tool is uniform, and the error is within 0.1 mm.

3. The ceramic cutting tool with a core-shell structure according to claim 1, characterized in that, the surface modifier is selected from one or more of KH550, KH560, KH570, oleic acid, and stearic acid.

4. The ceramic cutting tool with a core-shell structure according to claim 1, characterized in that, in the step S2, the photosensitive resin is selected from one or more of HDDA, PPTTA, TMPTA, and BPA2EODMA; the photoinitiator is one or two of Irgacure819 and Irgacure369; the dispersant is one or more of SOLSPERSE-24000, KOS-110, BYK-110, BYK-111, BYK-9076, BYK-163, and BYK-9077.

5. The ceramic cutting tool with a core-shell structure according to claim 1, characterized in that, The printing parameters in the step S3 are as follows: the wavelength of the light source is 405 nm, the ultraviolet light power density is 10-20 mW / cm 2 , the single-layer exposure time is 5-25 s, and the slice thickness is 10-50 μm.

6. The ceramic cutting tool with a core-shell structure according to claim 1, characterized in that, In the step S5, it further includes placing the degreased green body into a boron nitride crucible and burying it in a mixed powder of Si 3 N 4 :BN:AlN with a mass ratio of 5-7:2-4:1, and then placing it in a sintering furnace for sintering.

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