Preparation method of easily collapsible high-strength composite ceramic core for hot isostatic pressing

Abstract

This invention relates to a method for preparing a collapsible, high-strength composite ceramic core for hot isostatic pressing, comprising the following steps: S1: preparing a skeleton ceramic slurry; S2: designing a three-dimensional model of the core skeleton according to the required core structure; S3: forming a collapsible ceramic skeleton using 3D printing technology based on the pre-designed three-dimensional model of the core skeleton; S4: preparing a matrix ceramic slurry; S5: combining the ceramic skeleton with the ceramic matrix using a gel casting process, filling the voids in the ceramic skeleton with the matrix ceramic slurry prepared in step S4, and gel-setting to obtain a ceramic core green body; S6: drying, degreasing, sintering, and post-treatment to obtain the desired ceramic core. The ceramic core prepared by this method provides support for the ceramic matrix through the ceramic skeleton, exhibits good mechanical properties, and is suitable for the high-temperature and high-pressure working environment of hot isostatic pressing. During core corrosion and core removal, the ceramic skeleton can be easily removed, and the ceramic matrix falls off on its own after losing support, demonstrating excellent core removal performance.

Description

Technical Field

[0001] This invention relates to the field of ceramic core technology, and in particular to a method for preparing a high-strength, easily collapsible composite ceramic core for hot isostatic pressing. Background Technology

[0002] Hot isostatic pressing (HIP) is a process that uses inert gases such as nitrogen or argon as the pressure transmission medium. The workpiece is placed in a sealed container and subjected to isotropic pressure at 900-2000℃ and 100-200MPa. This technology can be combined with mold control technology (the internal mold is called the core, and the external mold is called the casing) to densify powder materials and form parts under high temperature and high pressure. After HIP, the casing and core are removed, resulting in near-net-shape metal parts.

[0003] In the near-net-shape forming process of hot isostatic pressing, a control core (usually made of mild steel) is usually placed inside the casing to control the internal structure of complex parts. Then, powder is filled, air is removed and sealed, followed by hot isostatic pressing sintering. Traditional metal control cores have the following drawbacks: (1) Some parts have complex and special internal structures, and the control core inside the hot isostatic pressing part cannot be removed by conventional machining. Instead, it can only be removed by acid etching. Acid etching causes great environmental pollution, and the etching process is immature and easily damages the surface of the formed part; (2) Under the high temperature and high pressure of hot isostatic pressing, the metal control core is prone to severe interfacial diffusion with the formed part, contaminating the surface of the part; (3) Since the strength of metal materials decreases with the increase of temperature, the metal control core is prone to deformation under the high temperature and high pressure of hot isostatic pressing, resulting in poor internal dimensional accuracy and high surface roughness of the final formed part.

[0004] Ceramic materials possess many excellent properties, including but not limited to high hardness, high modulus, wear resistance, high temperature resistance, erosion resistance, and corrosion resistance, leading to their increasingly widespread application in aerospace, defense, machinery, and chemical industries. Using ceramics as core materials has been widely applied in high-temperature alloy precision casting, especially in hot-end components of aerospace engines. This demonstrates the potential of ceramic cores in near-net-shape forming via hot isostatic pressing.

[0005] Hot isostatic pressing (HIP) processes require cores with high compressive strength, flexural strength, and good high-temperature stability. Ceramic materials such as alumina possess excellent mechanical properties, a high melting point, and good high-temperature and chemical stability. They do not react with metals under high temperature and pressure, making them ideal core materials. However, due to the excellent stability and extremely high density of alumina ceramics, complex cores often can only be removed through alkaline etching after part forming, which is extremely inefficient and easily damages the metal surface.

[0006] Existing research on improving the core-removal performance of ceramic cores mainly focuses on two aspects: structure and materials. For example, CN114804842A discloses a method for preparing ceramic cores with controllable pore distribution and atmosphere. This method extends ordinary cores into composite ceramics. Based on the structural characteristics of the core, a dedicated core structure and core with built-in ultra-high porosity are prepared step by step in the thick part. The core slurry needs to use pore-forming agents and different atmosphere additives, and is calcined in a targeted manner according to the characteristics of its matrix and additives. Irregular micropores are constructed in the core by pore-forming agents to improve the core-removal performance of ceramic cores. However, this method will reduce the mechanical properties of the core to a certain extent and does not meet the high strength requirements of the core in the hot isostatic pressing process. For example, CN114907133A discloses a silicon-based ceramic core material, including silicon-based ceramic core powder. The silicon-based ceramic core powder includes refractory powder and mineralizer. By adding mineralizer, the degree of ceramic sintering is reduced, which improves the core removal performance to a certain extent. However, this method also has the problem of low core mechanical properties. Summary of the Invention

[0007] To address the current limitations of existing technologies in fabricating materials that meet the performance requirements of hot isostatic pressing (HIP), this invention provides a method for preparing easily collapsible high-strength composite ceramic cores for HIP. The method involves using 3D printing to prepare an easily collapsible interconnected ceramic skeleton, and then using gel casting to combine this skeleton with a high-performance ceramic matrix filler material. This solves the problems of ceramic cores with good mechanical properties being difficult to remove from the mold, and easily collapsible ceramic cores failing to meet the mechanical performance requirements of HIP.

[0008] A method for preparing a collapsible high-strength composite ceramic core for hot isostatic pressing includes the following steps: S1: preparing a skeleton ceramic slurry; S2: designing a three-dimensional model of the core skeleton according to the required core structure; S3: forming a collapsible ceramic skeleton using 3D printing technology based on the pre-designed three-dimensional model of the core skeleton; S4: preparing a matrix ceramic slurry; S5: combining the ceramic skeleton with a ceramic matrix using a gel casting process, filling the voids in the ceramic skeleton with the matrix ceramic slurry prepared in step S4, and gel-setting to obtain a ceramic core green body; S6: drying, degreasing, sintering, and post-processing the gel-set ceramic core green body to obtain the desired ceramic core.

[0009] In one embodiment, the specific steps for preparing the framework ceramic slurry are as follows: S11: The dispersant is completely dissolved in anhydrous ethanol, the framework ceramic powder is added to the ethanol solution, and the mixture is thoroughly mixed by ball milling. After drying and grinding, the modified powder is obtained after powder modification; S12: The photosensitive resin, the modified powder, and the photoinitiator are mixed and stirred by vacuum ball milling to obtain the uniformly dispersed framework ceramic slurry, wherein the volume fraction of the modified powder is 30-50 vol%, and the photoinitiator is 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (TPO).

[0010] In one embodiment, the dispersant may be ammonium acrylate, KH550, Solsperse 41000 or other commonly used ceramic dispersants.

[0011] In one embodiment, the photosensitive resin may be a commonly used photosensitive resin such as HDDA, TPGDA, or ACMO.

[0012] In one embodiment, the skeletal ceramic powder may be selected from one or a combination of two of calcium oxide and silicon oxide.

[0013] In one embodiment, the particle size of the skeleton powder is 0.5 to 10 micrometers, and the ceramic prepared therefrom has a dissolution rate of greater than 1% / min in weak acid or weak alkali solutions.

[0014] In one embodiment, in step S3, the easily collapsible ceramic skeleton is formed using a photopolymerization 3D printing process.

[0015] In one embodiment, the specific steps for preparing the matrix ceramic slurry are as follows: S41: The solvent, monomer, dispersant and crosslinking agent are thoroughly mixed to prepare a premixed liquid; S42: 30-50 vol% matrix ceramic powder is added to the premixed liquid in multiple portions, and after thorough ball milling and stirring, a uniformly dispersed mixture is obtained.

[0016] S43: Before injection molding, add initiator and catalyst to the mixture and stir again to obtain the matrix ceramic slurry.

[0017] In one embodiment, in step S42, the matrix ceramic powder may be alumina, zirconium oxide, etc., and the ceramic sample prepared therefrom has a flexural strength greater than 100 MPa, and the particle size of the matrix powder is 0.5 to 10 micrometers.

[0018] In one embodiment, in step S43, the solvent may be an organic solvent such as deionized water or anhydrous ethanol.

[0019] In one embodiment, the monomer may be selected from chitosan, acrylamide, methacrylamide, and trimethylolpropane triglycidyl ether;

[0020] In one embodiment, the dispersant may be one or a combination of at least two of ammonium polyacrylate, polyethylene glycol, and ammonium citrate;

[0021] In one embodiment, the crosslinking agent may be tetraethylenepentamine or glutaraldehyde.

[0022] In one embodiment, in step S2, the core skeleton has independent through-holes of the same size, which are used to form and accommodate rod-shaped ceramic substrates adapted to the through-holes.

[0023] In one embodiment, the volume ratio of the ceramic matrix to the ceramic skeleton can be 0.67 to 1.5.

[0024] In one embodiment, the cross-sectional shape of the channel can be selected as circular or regular hexagonal.

[0025] In one embodiment, the diameter of the channel is 1 to 10 mm.

[0026] In one embodiment, the specific steps of obtaining the desired ceramic core after drying, degreasing, and sintering are as follows: S61: Degreasing is performed slowly using the powder embedding method. The ceramic core green body is embedded in deactivated alumina powder, and the temperature is raised to the degreasing temperature at a relatively slow rate (0.5~2℃ / min) and held to complete the degreasing; S62: After cooling, the degreased green body is taken out from the deactivated alumina powder, and the temperature is raised to the sintering temperature at a relatively fast rate (>4℃ / min) and held to complete the sintering. After sintering, the skeleton and the matrix are tightly bonded and there are no obvious defects.

[0027] In summary, compared with the prior art, the above-described technical solutions conceived by this invention can achieve the following beneficial effects:

[0028] 1. The present invention designs corresponding ordered channel skeleton structures according to different cores. The ordered channel structure has better mechanical properties than the traditional disordered channel structure, and the composite core has high bending strength and compressive strength.

[0029] 2. This invention divides the core into two parts: a skeleton and a matrix. The matrix provides higher mechanical strength, while the skeleton provides better core removal performance. Overall, its mechanical properties and core removal performance are superior to methods that optimize the core structure or material composition alone.

[0030] 3. The skeleton structure in step S2 of the present invention can be adjusted according to actual needs, and different ordered channel structures can be replaced to adapt to various application scenarios.

[0031] 4. In step S3 of this invention, the 3D printing process can rapidly form any complex skeleton structure, and the design of the skeleton structure is not limited by the process.

[0032] 5. This invention combines 3D printing technology with gel casting technology. 3D printing can quickly form complex and easily collapsible ceramic skeletons, while gel casting ensures high solid content of the matrix ceramic and high strength after sintering.

[0033] 6. When removing the ceramic core prepared by the present invention, the part only needs to be placed in water, weak acid or weak alkali solution, and the connected skeleton will quickly disintegrate, causing the independent ceramic matrix to fall off, thereby achieving the effect of rapid core removal. Attached Figure Description

[0034] Figure 1 A schematic diagram of the process for preparing a collapsible high-strength composite ceramic core for hot isostatic pressing;

[0035] Figure 2 This is a schematic diagram of the specific process of S1;

[0036] Figure 3 This is a schematic diagram of the specific process of S4;

[0037] Figure 4 This is a schematic diagram of the specific process of S6;

[0038] Figure 5 A schematic diagram of a ceramic skeleton structure constructed as a preferred embodiment of the present invention;

[0039] Figure 6 A schematic diagram of a ceramic core structure constructed as a preferred embodiment of the present invention;

[0040] Figure 7 A schematic diagram of a ceramic core-shaped thermostatically pressed gear component prepared according to a preferred embodiment of the present invention;

[0041] Figure 8 This is a schematic diagram showing the relative positions of the ceramic core and the hot isostatic gear component prepared according to a preferred embodiment of the present invention.

[0042] The correspondence between the reference numerals and the component names is as follows:

[0043] 100 ceramic cores, 1 ceramic skeleton, 2 ceramic substrates;

[0044] 200 hot isostatic pressing gear parts. Detailed Implementation

[0045] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0046] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and therefore the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0047] The preparation method of easily collapsible high-strength composite ceramic core for hot isostatic pressing according to some embodiments of the present invention is described below with reference to the accompanying drawings.

[0048] like Figure 1 As shown in the figure, this embodiment discloses a method for preparing a collapsible high-strength composite ceramic core for hot isostatic pressing, including the following steps: S1: preparing a skeleton ceramic slurry; S2: designing a three-dimensional model of the core skeleton according to the required core structure; S3: forming a collapsible ceramic skeleton 1 using 3D printing technology based on the pre-designed three-dimensional model of the core skeleton; S4: preparing a matrix ceramic slurry; S5: combining the ceramic skeleton 1 and the ceramic matrix 2 using a gel casting process, filling the voids in the ceramic skeleton 1 with the matrix ceramic slurry prepared in step S4, and gel-setting to obtain a ceramic core green body; S6: drying, degreasing, sintering, and post-processing the gel-set ceramic core green body to obtain the required ceramic core 100.

[0049] like Figure 2 As shown, in addition to the features of the above embodiments, this embodiment further specifies the following specific steps for preparing the skeleton ceramic slurry: S11: Dissolve the dispersant completely in anhydrous ethanol, add the skeleton ceramic powder to the ethanol solution, mix thoroughly by ball milling, dry and grind, and obtain modified powder after powder modification; S12: Mix the photosensitive resin, the above modified powder, and the photoinitiator, and stir by vacuum ball milling to obtain a uniformly dispersed skeleton ceramic slurry, wherein the volume fraction of the modified powder is 30-50 vol%, and the photoinitiator is 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (TPO).

[0050] In addition to the features of the above embodiments, this embodiment further specifies that the dispersant can be one of ammonium acrylate, KH550, or Solsperse 41000.

[0051] In addition to the features of the above embodiments, this embodiment further specifies that the photosensitive resin can be selected from HDDA, TPGDA, and ACMO.

[0052] In addition to the features of the above embodiments, this embodiment further specifies that the skeletal ceramic powder can be selected from one or a combination of two of calcium oxide and silicon oxide.

[0053] In addition to the features of the above embodiments, this embodiment further specifies that: the particle size of the skeletal ceramic powder is 0.5-10 micrometers, and the ceramic prepared therefrom has a dissolution rate greater than 1% / min in weak acid or alkaline solutions. The resulting ceramic has good collapsibility and can dissolve rapidly in weak acid or alkaline core-removing solutions, thereby ensuring the core-removing performance of the ceramic skeleton, while also meeting the slurry flow performance and printing accuracy required for 3D printing.

[0054] In addition to the features of the above embodiments, this embodiment further specifies that: in step S3, a easily collapsible ceramic skeleton 1 is formed by photopolymerization 3D printing process.

[0055] like Figure 3 As shown, in addition to the features of the above embodiments, this embodiment further specifies the following specific steps for preparing the matrix ceramic slurry: S41: The solvent, monomer, dispersant and crosslinking agent are thoroughly mixed to prepare a premix; S42: 30-50 vol% matrix ceramic powder is added to the premix in multiple portions, and after thorough ball milling and stirring, a uniformly dispersed mixture is obtained; S43: Before injection molding, an initiator and catalyst are added to the mixture, and the mixture is stirred again to obtain the matrix ceramic slurry.

[0056] In addition to the features of the above embodiments, this embodiment further specifies that: in step S42, the matrix ceramic powder can be selected from one or a combination of alumina and zirconium oxide, the particle size of the matrix ceramic powder is 0.5-10 micrometers, and the flexural strength of the prepared ceramic sample is greater than 100 MPa. The prepared ceramic matrix 2 has good mechanical properties, the ceramic core 100 is not easily deformed, which can meet the high strength requirements of the core in the hot isostatic pressing process, and at the same time can also meet the requirements of slurry flow performance and curing performance required for gel casting.

[0057] In addition to the features of the above embodiments, this embodiment further specifies that: in step S43, the solvent can be an organic solvent such as deionized water or anhydrous ethanol.

[0058] In addition to the features of the above embodiments, this embodiment further specifies that the monomer may be selected from chitosan, acrylamide, methacrylamide, and trimethylolpropane triglycidyl ether.

[0059] In addition to the features of the above embodiments, this embodiment further specifies that the dispersant can be one or a combination of at least two of ammonium polyacrylate, polyethylene glycol, and ammonium citrate.

[0060] In addition to the features of the above embodiments, this embodiment further specifies that the crosslinking agent can be tetraethylenepentamine or glutaraldehyde.

[0061] In addition to the features of the above embodiments, this embodiment further specifies that: in step S2, there are mutually independent through-holes of the same size in the core skeleton, and the through-holes are used to form and accommodate rod-shaped ceramic substrates adapted to the through-holes. By setting mutually independent through-holes on the core skeleton and filling the through-holes with matrix ceramic slurry, multiple mutually discrete ceramic substrates 2 can be formed, which facilitates the rapid detachment of the ceramic substrates 2 when the ceramic core 100 is removed.

[0062] In addition to the features of the above embodiments, this embodiment further specifies that the volume ratio of the ceramic substrate 2 to the ceramic skeleton 1 can be 0.67 to 1.5.

[0063] In addition to the features of the above embodiments, this embodiment further specifies that the cross-sectional shape of the channel can be selected as circular or regular hexagonal.

[0064] In addition to the features of the above embodiments, this embodiment further specifies that the diameter of the channel is 1 to 10 mm.

[0065] like Figure 4 As shown, in addition to the features of the above embodiments, this embodiment further defines the specific steps for obtaining the desired ceramic core 100 after drying, degreasing, and sintering as follows: S61: Degreasing is performed slowly using the powder embedding method. The ceramic core green body is embedded in deactivated alumina powder, and the temperature is raised to the degreasing temperature at a relatively slow rate (0.5~2℃ / min) and held to complete the degreasing; S62: After cooling, the degreased green body is taken out from the deactivated alumina powder, and the temperature is raised to the sintering temperature at a relatively fast rate (>4℃ / min) and held to complete the sintering. After sintering, the skeleton and the matrix are tightly bonded and there are no obvious defects.

[0066] The ceramic core will be manufactured following the above process flow, and then applied to the near-net-shape hot isostatic pressing of TC4 titanium alloy gear parts, such as... Figures 5 to 8 The present invention will be further described in detail below.

[0067] Example 1

[0068] (a) Dissolve 5g of dispersant silane coupling agent KH550 completely in 200ml of anhydrous ethanol. Add 200cm³ of calcium oxide powder to the ethanol solution, ball mill for 6 hours, and then vacuum dry. The powder is then ground to complete the modification. Mix the photosensitive resin ACMO, the above modified powder, and the photoinitiator TPO, and vacuum ball mill for 3 hours to obtain the final slurry, wherein the volume fraction of the modified powder is 30%.

[0069] (b) A skeleton model was constructed using the modeling software SolidWorks. The cross-section of the skeleton channels was a regular hexagon with a side length of 2mm, and the distance between two channels was 1mm. The 3D model was then converted into an STL format file.

[0070] (c) Based on the three-dimensional model constructed in step (b), after slicing the file, import it into the printer and print the ceramic skeleton using digital light processing (DLP) technology. The specific printing process parameters are: slice thickness of 25μm, single-layer exposure time of 2s, and ultraviolet light power of 16%.

[0071] (d) A premix was prepared by completely dissolving 1 wt% chitosan in a 1 wt% aqueous acetic acid solution. 0.3 wt% ammonium polyacrylate, alumina powder, and the premix were mixed and ball-milled for 6 hours to obtain a well-dispersed mixture, wherein the alumina powder accounted for 45% of the volume fraction of the slurry. After thorough defoaming, 0.1 wt% glutaraldehyde, a crosslinking agent, was added, and the mixture was mixed again to obtain the final slurry.

[0072] (e) Place the skeleton printed in step (c) into the mold, and inject the slurry prepared in step (d) into the mold under negative pressure to ensure that the gas in the mold is fully discharged. Let it stand at room temperature for 24 hours to ensure that the slurry is fully gelled and shaped. After removing it from the mold, place it under the conditions of 50% humidity and room temperature to dry slowly to obtain the core blank.

[0073] (f) The core blank obtained in step (e) is embedded in deactivated alumina powder for degreasing. The temperature is first increased to 100°C at a rate of 2°C / min, then to 300°C at a rate of 1°C / min, and finally to 680°C at a rate of 0.5°C / min. During the heating process, the temperature is held at 300°C, 400°C, and 680°C for 2 hours each to completely remove organic matter from the blank. After cooling, the degreased blank is removed from the alumina powder and heated to 1500°C at a rate of 5°C / min, held for 2 hours, and then cooled to room temperature in the furnace to complete sintering. After simple post-treatment, a composite ceramic core 100 with high mechanical strength and excellent core-removing performance suitable for hot isostatic pressing is obtained.

[0074] (g) According to the size and shape of the gear, process the corresponding Q235 steel sleeve, install the ceramic core 100 obtained in step (f) into the sleeve, and fill the pores in the sleeve with powder.

[0075] (h) Place the above-mentioned casing in a heating furnace, and then use a vacuum device to evacuate the inside of the casing at 500°C through a vacuum tube. When the vacuum degree reaches 10-3 Pa, seal the vacuum tube.

[0076] (i) The package is placed in the hot isostatic pressing chamber for hot isostatic pressing. The hot isostatic pressing process parameters are: 920℃, 120MPa, and the temperature and pressure are increased simultaneously, and the temperature and pressure are maintained for 3 hours.

[0077] (j) After hot isostatic pressing, the outer casing is removed by machining. The part is then placed in water, and the ceramic skeleton 1 quickly disintegrates. The discrete ceramic matrix 2 falls off, and the ceramic core 100 is easily removed, resulting in the TC4 hot isostatic pressing gear part 200.

[0078] Example 2

[0079] (a) Dissolve 5g of dispersant Solsperse 41000 completely in 200ml of anhydrous ethanol. Add 200cm³ of calcium oxide powder to the ethanol solution, ball mill for 6 hours, and then vacuum dry. The powder is then ground to complete the modification. Mix the photosensitive resin ACMO, the above modified powder, and the photoinitiator TPO, and ball mill under vacuum for 3 hours to obtain the final slurry, wherein the volume fraction of the modified powder is 40%.

[0080] (b) The skeleton model was constructed using the modeling software SolidWorks. Each beam had a cross section of 1mm × 1mm and the spacing between adjacent beams on the same layer was 1mm, i.e., the porosity was 50%. The three-dimensional model was then converted into an STL format file.

[0081] (c) Based on the three-dimensional model constructed in step (b), after slicing the file, import it into the printer and print the ceramic skeleton using DLP technology. The specific printing process parameters are: slice thickness of 25μm, single-layer exposure time of 2s, and ultraviolet light power of 16%.

[0082] (d) A premix was prepared by completely dissolving 1 wt% chitosan in a 1 wt% aqueous acetic acid solution. 0.3 wt% ammonium polyacrylate, zirconium oxide powder, and the premix were mixed and ball-milled for 6 hours to obtain a well-dispersed mixture, wherein the alumina powder accounted for 40% of the volume fraction of the slurry. After thorough defoaming, 0.1 wt% glutaraldehyde, a crosslinking agent, was added, and the mixture was mixed again to obtain the final slurry.

[0083] (e) Place the skeleton printed in step (c) into the mold, and inject the slurry prepared in step (d) into the mold under negative pressure to ensure that the gas in the mold is fully discharged. Let it stand at room temperature for 24 hours to ensure that the slurry is fully gelled and shaped. After removing it from the mold, place it under the conditions of 50% humidity and room temperature to dry slowly to obtain the core blank.

[0084] (f) The core blank obtained in step (e) is embedded in deactivated alumina powder for degreasing. The temperature is first increased to 100°C at a rate of 2°C / min, then to 300°C at a rate of 1°C / min, and finally to 680°C at a rate of 0.5°C / min. During the heating process, the temperature is held at 300°C, 400°C, and 680°C for 2 hours respectively to completely remove organic matter from the blank. After cooling, the degreased blank is removed from the alumina powder and heated to 1450°C at a rate of 5°C / min, held for 2 hours, and then cooled to room temperature in the furnace to complete sintering. After simple post-treatment, a composite ceramic core 100 with high mechanical strength and excellent core removal performance suitable for hot isostatic pressing is obtained.

[0085] (g) According to the size and shape of the gear, process the corresponding Q235 steel sleeve, install the ceramic core 100 obtained in step (f) into the sleeve, and fill the pores in the sleeve with powder.

[0086] (h) Place the above-mentioned casing in a heating furnace, and then use a vacuum device to evacuate the inside of the casing at 500°C through a vacuum tube. When the vacuum degree reaches 10-3 Pa, seal the vacuum tube.

[0087] (i) The package is placed in the hot isostatic pressing chamber for hot isostatic pressing. The hot isostatic pressing process parameters are: 920℃, 120MPa, and the temperature and pressure are increased simultaneously, and the temperature and pressure are maintained for 3 hours.

[0088] (j) After hot isostatic pressing, the outer casing is removed by machining. The part is then placed in water, and the ceramic skeleton 1 quickly disintegrates. The discrete ceramic matrix 2 falls off, and the ceramic core 100 is easily removed, resulting in the TC4 hot isostatic pressing gear part 200.

[0089] Example 3

[0090] (a) Dissolve 5g of dispersant silane coupling agent KH550 completely in 200ml of anhydrous ethanol. Add 660g of calcium oxide powder (200cm3) to the ethanol solution, wherein the mass of the dispersant is 1% of the mass of the calcium oxide powder. Ball mill for 6h and then vacuum dry. The powder is then ground to complete the modification. Mix the photosensitive resin ACMO, the above modified powder, and the photoinitiator TPO, and vacuum ball mill for 3h to obtain the final slurry, wherein the volume fraction of the modified powder is 50%.

[0091] (b) The skeleton model was constructed using the modeling software SolidWorks. Each beam had a cross section of 2mm × 2mm and the spacing between adjacent beams on the same layer was 2mm, i.e., the porosity was 50%. The three-dimensional model was then converted into an STL format file.

[0092] (c) Based on the three-dimensional model constructed in step (b), after slicing the file, import it into the printer and print the ceramic skeleton using digital light processing (DLP) technology. The specific printing process parameters are: slice thickness of 25μm, single-layer exposure time of 2s, and ultraviolet light power of 16%.

[0093] (d) Dissolve 20 wt% trimethylolpropane triglycidyl ether (TTE) and 1 wt% polyethylene glycol 400 (PEG400) in 200 ml of anhydrous ethanol and disperse them thoroughly by ultrasonication to obtain a premix. Then, vacuum ball mill the premix, tetraethylenepentamine (TEPA), and zirconium oxide powder to obtain a slurry, wherein TEPA / TTE = 1 / 4 and the zirconium oxide powder accounts for 45% of the volume fraction of the slurry.

[0094] (e) Place the skeleton printed in step (c) into the mold, and inject the slurry prepared in step (d) into the mold under negative pressure to ensure that the gas in the mold is fully discharged. Let it stand at room temperature for 12 hours to ensure that the slurry is fully gelled and shaped. After removing it from the mold, place it under the conditions of 10% humidity and room temperature to dry slowly to obtain the core blank.

[0095] (f) The core blank obtained in step (e) is embedded in deactivated alumina powder for degreasing. The temperature is first increased to 100°C at a rate of 2°C / min, then to 300°C at a rate of 1°C / min, and finally to 600°C at a rate of 0.5°C / min. During the heating process, the temperature is held at 300°C, 400°C, and 600°C for 2 hours each to completely remove organic matter from the blank. After cooling, the degreased blank is removed from the alumina powder and heated to 1450°C at a rate of 5°C / min, held for 2 hours, and then cooled to room temperature in the furnace to complete sintering. After simple post-treatment, a composite ceramic core 100 with high mechanical strength and excellent core-removing performance suitable for hot isostatic pressing is obtained.

[0096] (g) According to the size and shape of the gear, process the corresponding Q235 steel sleeve, install the ceramic core 100 obtained in step (f) into the sleeve, and fill the pores in the sleeve with powder.

[0097] (h) Place the above-mentioned casing in a heating furnace, and then use a vacuum device to evacuate the inside of the casing at 500°C through a vacuum tube. When the vacuum degree reaches 10-3 Pa, seal the vacuum tube.

[0098] (i) The package is placed in the hot isostatic pressing chamber for hot isostatic pressing. The hot isostatic pressing process parameters are: 920℃, 120MPa, and the temperature and pressure are increased simultaneously, and the temperature and pressure are maintained for 3 hours.

[0099] (j) After hot isostatic pressing, the outer casing is removed by machining. The part is then placed in water, and the ceramic skeleton 1 quickly disintegrates. The discrete ceramic matrix 2 falls off, and the ceramic core 100 is easily removed, resulting in the TC4 hot isostatic pressing gear part 200.

[0100] As can be seen from the above description, the embodiments of the present invention achieve the following technical effects:

[0101] 1. The present invention designs corresponding ordered channel skeleton structures according to different cores. The ordered channel structure has better mechanical properties than the traditional disordered channel structure, and the composite core has high bending strength and compressive strength.

[0102] 2. This invention divides the core into two parts: a skeleton and a matrix. The matrix provides higher mechanical strength, while the skeleton provides better core removal performance. Overall, its mechanical properties and core removal performance are superior to methods that optimize the core structure or material composition alone.

[0103] 3. The skeleton structure in step S2 of the present invention can be adjusted according to actual needs, and different ordered channel structures can be replaced to adapt to various application scenarios.

[0104] 4. In step S3 of this invention, the 3D printing process can rapidly form any complex skeleton structure, and the design of the skeleton structure is not limited by the process.

[0105] 5. This invention combines 3D printing technology with gel casting technology. 3D printing can quickly form complex and easily collapsible ceramic skeletons, while gel casting ensures high solid content of the matrix ceramic and high strength after sintering.

[0106] 6. When removing the ceramic core prepared by the present invention, the part only needs to be placed in water, weak acid or weak alkali solution, and the connected skeleton will quickly disintegrate, causing the independent ceramic matrix to fall off, thereby achieving the effect of rapid core removal.

[0107] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0108] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for preparing a collapsible high-strength composite ceramic core for hot isostatic pressing, characterized in that, Includes the following steps: S1: Prepare a skeleton ceramic slurry, wherein the skeleton ceramic powder contained in the skeleton ceramic slurry is at least one of calcium oxide or silicon oxide; S2: Based on the required core structure, design a three-dimensional model of the core skeleton. The core skeleton contains mutually independent through channels of the same size. The channels are used to form and accommodate rod-shaped ceramic substrates that are adapted to the channels. S3: Based on the pre-designed three-dimensional model of the core skeleton, a easily collapsible ceramic skeleton is formed using 3D printing technology (1). S4: Prepare the matrix ceramic slurry; S5: The ceramic skeleton (1) and the ceramic matrix (2) are combined using a gel casting process. The ceramic matrix slurry prepared in step S4 is used to fill the gaps in the ceramic skeleton (1). The ceramic core green body is obtained by gel molding. S6: The ceramic core green body obtained by gel shaping is dried, degreased, sintered and then treated to obtain the desired ceramic core (100).

2. The method for preparing a collapsible high-strength composite ceramic core for hot isostatic pressing as described in claim 1, characterized in that, The specific steps for preparing the skeleton ceramic slurry are as follows: S11: The dispersant is completely dissolved in anhydrous ethanol, the skeleton ceramic powder is added to the ethanol solution, and the mixture is fully mixed by ball milling. After drying and grinding, the modified powder is obtained after the powder modification is completed. S12: The photosensitive resin, the modified powder, and the photoinitiator are mixed and stirred by vacuum ball milling to obtain the uniformly dispersed skeleton ceramic slurry, wherein the volume fraction of the modified powder is 30-50 vol%, and the photoinitiator is 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (TPO).

3. The method for preparing a collapsible high-strength composite ceramic core for hot isostatic pressing as described in claim 2, characterized in that, The dispersant is one of ammonium acrylate, KH550, and Solsperse 41000; And / or the photosensitive resin is one of HDDA, TPGDA, and ACMO; And / or the particle size of the skeleton ceramic powder is 0.5~10 micrometers, and the ceramic prepared therefrom has a dissolution rate of greater than 1% / min in weak acid or alkaline solution.

4. The method for preparing a collapsible high-strength composite ceramic core for hot isostatic pressing as described in claim 1, characterized in that, In step S3, the easily collapsible ceramic skeleton (1) is formed using a photopolymerization 3D printing process.

5. The method for preparing a collapsible high-strength composite ceramic core for hot isostatic pressing as described in claim 1, characterized in that, The specific steps for preparing the matrix ceramic slurry are as follows: S41: Thoroughly mix the solvent, monomer, dispersant and crosslinking agent to prepare a premix; S42: Add 30~50 vol% matrix ceramic powder to the premixed liquid in multiple portions, and after thorough ball milling and stirring, obtain a uniformly dispersed mixture; S43: Before injection molding, add initiator and catalyst to the mixture and stir again to obtain the matrix ceramic slurry.

6. The method for preparing a collapsible high-strength composite ceramic core for hot isostatic pressing as described in claim 5, characterized in that, In step S42, the matrix ceramic powder is at least one of alumina and zirconium oxide, the particle size of the matrix ceramic powder is 0.5~10 micrometers, and the flexural strength of the ceramic sample prepared therefrom is greater than 100 MPa.

7. The method for preparing a collapsible high-strength composite ceramic core for hot isostatic pressing as described in claim 5, characterized in that, In step S41, the solvent is deionized water or anhydrous ethanol; And / or the monomer is one of chitosan, acrylamide, methacrylamide, and trimethylolpropane triglycidyl ether; And / or the dispersant is one of ammonium polyacrylate, polyethylene glycol, and ammonium citrate; And / or the crosslinking agent is one of tetraethylenepentamine or glutaraldehyde.

8. The method for preparing a collapsible high-strength composite ceramic core for hot isostatic pressing as described in claim 1, characterized in that, The volume ratio of the ceramic matrix (2) to the ceramic skeleton (1) is 0.67~1.5; And / or the cross-sectional shape of the channel is circular or regular hexagonal; And / or the diameter of the channel is 1~10mm.

9. The method for preparing a collapsible high-strength composite ceramic core for hot isostatic pressing as described in any one of claims 1-7, characterized in that, The specific steps for obtaining the desired ceramic core (100) after drying, degreasing, and sintering are as follows: S61: Degreasing is performed slowly by embedding the ceramic core green body in deactivated alumina powder, heating it to the degreasing temperature at a heating rate of 0.5~2℃ / min and then holding it at that temperature to complete the degreasing process. S62: After cooling, the degreased blank is taken out from the deactivated alumina powder, heated to the sintering temperature at a heating rate of >4 ℃ / min, and held at that temperature to complete sintering. After sintering, the skeleton and the matrix are tightly bonded together and there are no obvious defects.

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