Silicon-based ceramic core with high temperature strength yielding property and method of making same

Abstract

This invention discloses a silicon-based ceramic core with high-temperature strength yielding properties and its preparation method. The silicon-based ceramic core includes a core matrix, strength yielding units, and a surface dense layer. The strength yielding units are uniformly embedded inside the core matrix, and the surface dense layer is uniformly coated on the outer surface of the core matrix. The mass ratio of the core matrix to the strength yielding units is 3-5.6:1. The preparation method includes the following steps: preparing a core matrix slurry, strength yielding units, and a surface dense layer slurry; mixing the strength yielding units into the core matrix slurry to obtain a mixed slurry; injecting the mixed slurry into a ceramic core mold for filling and die casting to obtain a wet blank; coating the outer surface of the wet blank with the surface dense layer slurry, drying it to obtain a silicon-based ceramic core blank, followed by degreasing and sintering. This invention solves the problems in the prior art such as the mismatch between the high-temperature strength of the ceramic core and the solidification stress of the alloy liquid, casting hot cracking, internal cavity recrystallization, core leakage, core deviation, and difficulty in core removal.

Description

Technical Field

[0001] This invention belongs to the field of ceramic core material design and preparation technology, specifically relating to a silicon-based ceramic core with high-temperature strength yielding properties and its preparation method. This silicon-based ceramic core is particularly suitable for the investment casting process of single-crystal high-temperature alloy blades in the aerospace field. Background Technology

[0002] Single-crystal blades are core components of high-end equipment such as aero-engines and gas turbines, and their performance directly determines the operating efficiency and service life of the equipment. Directional solidification technology is a key process in the preparation of single-crystal blades. In this process, a ceramic core is used to form the complex internal cavity of the blade, and its performance is crucial to the forming quality of the single-crystal blade.

[0003] Currently, existing ceramic core technologies face numerous technical challenges in the directional solidification of single-crystal blades, severely impacting blade forming quality and production efficiency. Firstly, the high-temperature strength of the ceramic core is difficult to precisely match with the stress during alloy solidification. If the ceramic core's high-temperature strength is too high, it will create a rigid barrier to the casting during solidification, generating internal stress. Excessive internal stress can directly cause thermal cracking. Even without cracking, residual internal stress can induce recrystallization within the casting cavity during subsequent heat treatment, thus reducing the blade's mechanical properties. Secondly, if the ceramic core's high-temperature strength is too low, it is susceptible to deformation and breakage due to molten metal impact during high-temperature alloy pouring, leading to defects such as core leakage and core misalignment, potentially resulting in scrapped castings. Third, the strength and density of ceramic cores are positively correlated. Excessive strength will lead to an increase in core density, making it difficult to remove the core after casting. This not only increases the production process, but may also affect the surface quality of the blade's inner cavity due to mechanical damage during the core removal process.

[0004] Existing technologies for improving the performance of ceramic cores mostly focus on optimizing a single property, such as increasing high-temperature strength by adjusting the raw material ratio or improving core removal efficiency by adding pore-forming agents. However, these methods have failed to solve the matching problem between the high-temperature strength of ceramic cores and the solidification stress of the alloy liquid, and therefore it is difficult to simultaneously meet the requirements of multiple properties such as anti-leakage, anti-eccentricity, anti-thermal cracking, and easy core removal.

[0005] Patent application CN116102364A discloses a crack-resistant inert ceramic core. By setting a silicon oxide substrate, an alumina transition layer, and a yttrium oxide surface layer, it solves the coating cracking problem, but does not address the issue of matching the high-temperature strength of the ceramic core with the solidification stress of the alloy melt. Patent application CN115846596A discloses a superalloy directional solidification core. By adjusting the type and mass ratio of raw materials, it improves both room-temperature and high-temperature strength, but exacerbates the difficulty of core removal and cannot avoid the generation of internal stress in the casting. Therefore, how to develop a ceramic core that can achieve a match between high-temperature strength and the solidification stress of the alloy melt, and possesses good anti-leakage, anti-eccentricity, and easy core removal characteristics, has become an urgent technical problem to be solved in the field of directional solidification of single-crystal blades. Summary of the Invention

[0006] To address the problems existing in the prior art, the present invention provides a silicon-based ceramic core with high-temperature strength yielding properties. The silicon-based ceramic core includes a core substrate, strength yielding units, and a surface dense layer. The strength yielding units are uniformly embedded inside the core substrate, and the surface dense layer uniformly covers the outer surface of the core substrate and is tightly bonded to the core substrate. The mass ratio of the core substrate to the strength yielding units is 3-5.6:1, and the thickness of the surface dense layer is 50-100 μm.

[0007] Preferably, the mass percentage of each substance in the core matrix is ​​60-75 wt% silica powder, 15-25 wt% alumina powder, 2-5 wt% mineralizer, 3-8 wt% binder, and 1-5 wt% sintering aid.

[0008] In any of the above embodiments, preferably, the mineralizing agent is composed of zirconium silicate and yttrium oxide, and the mass ratio of zirconium silicate to yttrium oxide is 1:0.8-1.2; the binder is composed of silica sol and polyvinyl alcohol, and the mass ratio of silica sol to polyvinyl alcohol is 3-5:1; the sintering aid is composed of zinc borate, neodymium oxide, scandium oxide, yttrium oxide and lanthanum oxide, wherein the total mass of zinc borate, neodymium oxide and scandium oxide accounts for 65-75 wt%, yttrium oxide accounts for 10-20 wt%, lanthanum oxide accounts for 10-20 wt%, and the mass ratio of zinc borate, neodymium oxide and scandium oxide is 1.5-2:1-1.5:1.

[0009] In any of the above embodiments, preferably, the silica powder includes three particle size ranges, with each particle size range accounting for the following mass percentages of the silica powder: 40μm≤particle size≤65μm accounts for 25-35wt%, 25μm≤particle size<40μm accounts for 38-50wt%, and 10μm≤particle size<25μm accounts for 20-30wt%; the alumina powder has a particle size of 5-20μm, and the sintering aid has a particle size of 1-10μm.

[0010] In this invention, silica powder is configured with three particle sizes, each in a reasonable mass ratio. This ensures both the molding performance of the core and provides space for the uniform distribution of strength relief units. Alumina powder is used to enhance the basic strength of the core matrix, preventing deformation during casting. Sintering aids lower the sintering temperature, promote the densification of raw material particles, and further improve the high-temperature performance of the core matrix. Mineralizers promote the crystal phase transformation during core sintering, optimizing the high-temperature stability of the core. The binder combines bonding strength and molding flowability, ensuring the quality of core molding.

[0011] In any of the above embodiments, it is preferred that the strength yielding unit is composed of high-temperature decomposable composite ceramic microspheres and an elastic binder, wherein the mass ratio of the high-temperature decomposable composite ceramic microspheres to the elastic binder is 2.5-4:1; and the particle size of the strength yielding unit is 0.1-0.5 mm.

[0012] In any of the above embodiments, it is preferred that the mass percentage of each substance in the high-temperature decomposable composite ceramic microspheres is as follows: calcium carbonate-zirconia composite microspheres 45-55 wt%, volcanic ash microspheres 10-20 wt%, hydroxyapatite microspheres 15-25 wt%, and biphasic calcium phosphate microspheres 10-20 wt%; and the elastic binder is nano-modified organosilicon rubber.

[0013] In this invention, the strength relief unit is the core structure for matching high-temperature strength with the solidification stress of the molten alloy. It is a spherical structure with a diameter of 0.1-0.5 mm, composed of high-temperature decomposable composite ceramic microspheres and an elastic binder. The high-temperature decomposable composite ceramic microspheres are composed of various microspheres and can gradually decompose within the core temperature range of 1200-1500℃ for the directional solidification of single-crystal blades, simultaneously forming numerous uniformly distributed micropores within the core matrix. The elastic binder is nano-modified silicone rubber, which maintains a certain elastic deformation at high temperatures, buffering the stress generated during the solidification of the molten alloy and achieving strength relief of the core, thus avoiding rigid obstruction to the casting. By adjusting the proportions of the various substances in the high-temperature decomposable composite ceramic microspheres, the degradation rate of the microspheres can be controlled, thereby adjusting the high-temperature strength of the core at different temperature stages to achieve matching with the solidification stress of the molten alloy. By controlling the mass ratio of the strength relief unit to the core matrix, the high-temperature strength and core removal performance of the ceramic core can be balanced, avoiding excessively high or low strength.

[0014] In any of the above embodiments, preferably, the dense surface layer is composed of alumina powder and a sol component, wherein the mass ratio of alumina powder to the sol component is 3.5-4.5:1; the sol component is composed of yttrium sol, aluminum sol and silica sol, wherein the mass ratio of yttrium sol, aluminum sol and silica sol is 1:0.5-1:1.5-3; and the particle size of the alumina powder is 0.1-1 μm.

[0015] In this invention, the thickness of the surface dense layer is 50-100μm, and it is composed of alumina powder and sol components. Its high temperature strength is higher than that of the core substrate. It is coated on the outer surface of the core substrate by spraying and then sintered together with the core substrate after drying to form a tightly bonded dense layer. This dense layer can effectively prevent high temperature alloy liquid from penetrating into the core, avoiding defects such as core leakage and core deviation, while not affecting the overall yielding performance and core removal efficiency of the core.

[0016] This invention also provides a method for preparing a silicon-based ceramic core with high-temperature strength yielding properties, the preparation method comprising the following steps in sequence: Step 1: Prepare the core matrix slurry, strength relief unit, and surface dense layer slurry according to the preset material ratio and process parameters; Step 2: Place the strength relief unit into the core matrix slurry and stir evenly to obtain a mixed slurry; Step 3: The mixed slurry is injected into the ceramic core mold using a pressure injection machine for filling and die casting to obtain a wet blank of silicon-based ceramic core; Step 4: Apply a dense surface slurry to the outer surface of the wet silicon-based ceramic core blank using a spraying device, and then dry it to obtain the silicon-based ceramic core blank. Step 5: The silicon-based ceramic core blank is subjected to degreasing and sintering treatment in sequence to obtain a silicon-based ceramic core with high-temperature strength yielding properties.

[0017] Preferably, in step one, the preparation process of the core matrix slurry is as follows: First, zinc borate, neodymium oxide, scandium oxide, yttrium oxide, and lanthanum oxide are mixed evenly at room temperature to obtain a sintering aid; second, a plasticizer is placed in a mixer and heated to melt while stirring, at a heating temperature of 100-130℃, a stirring speed of 300-500 rpm, and a stirring time of 1-3 hours, so that the plasticizer is completely melted; then, silica powder, alumina powder, the mineralizing agent components zirconium silicate and yttrium oxide, and the sintering aid are added to the mixer and stirring is continued for 48-72 hours to ensure that all substances are mixed evenly; finally, the binder components silica sol and polyvinyl alcohol are added to the mixer and stirring is continued for 4-8 hours to ensure that all substances are mixed evenly, thus obtaining the core matrix slurry, which is then kept warm for later use.

[0018] The plasticizer is composed of paraffin wax, beeswax, and polyethylene, with a mass ratio of 1:1:1. The amount of plasticizer added is 15-30 wt% of the total amount of each substance in the core matrix. In any of the above solutions, it is preferred that, in step one, the manufacturing process of the strength relief unit includes the following steps in sequence: Step 1.1: Preparation of calcium carbonate-zirconia composite microspheres: First, according to the mass ratio of calcium carbonate microspheres to zirconium sol of 1:4-8, the calcium carbonate microspheres and zirconium sol are placed in an ultrasonic container for ultrasonic dispersion at a frequency of 20-40 kHz for 30-60 min, so that the zirconium sol uniformly coats the calcium carbonate microspheres to obtain a composite slurry. Then, the composite slurry is placed in an oven for low-temperature curing at 60-80℃ for 2-3 h. Subsequently, it is placed in a heat treatment furnace for heat treatment at 180-250℃ for 1-2 h to solidify the zirconium oxide gel and obtain a composite powder. Finally, the composite powder is washed in an ethanol solution to remove residual sol, followed by freeze-drying at -30 to -20℃ for 24-48 h to obtain calcium carbonate-zirconia composite microspheres. Step 1.2: Mix calcium carbonate-zirconia composite microspheres, volcanic ash microspheres, hydroxyapatite microspheres, and biphasic calcium phosphate microspheres uniformly at room temperature to obtain high-temperature decomposable composite ceramic microspheres; Step 1.3: Place the high-temperature decomposable composite ceramic microspheres and nano-modified organosilicon rubber into a mixing container, stir at room temperature at a speed of 300-500 rpm for 4-6 hours to ensure uniform mixing of all materials and obtain the strength reduction unit slurry. Step 1.4: First, the strength yielding unit slurry is made into spherical particles with a particle size of 0.1-0.5mm using a spray granulator. The atomizing disc speed is 8000-12000rpm, the inlet air temperature is 180-300℃, the outlet air temperature is 90-120℃, and the feed rate is 100-200mL / min. Then, the spherical particles are placed in an oven for drying at a temperature of 80-100℃ for 12-24h to obtain the strength yielding unit.

[0019] In any of the above schemes, it is preferred that, in step one, the preparation process of the surface dense layer slurry is as follows: first, yttrium sol, aluminum sol and silica sol are mixed at room temperature for 1-3 hours to obtain sol components, and then the sol components and alumina powder are mixed at room temperature for 30-40 minutes to make the substances evenly mixed, thus obtaining the surface dense layer slurry.

[0020] In any of the above schemes, it is preferred that, in step two, the mixing temperature of the strength relief unit and the core matrix slurry is room temperature, the mixing speed is 200-300 rpm, and the mixing time is 10-12 h.

[0021] In any of the above schemes, the preferred method is that, in step three, the die-casting parameters of the silicon-based ceramic core wet blank are: die-casting pressure 3-8MPa, die-casting temperature 80-120℃, mold temperature 25-45℃, and holding time 15-30s.

[0022] In any of the above schemes, it is preferred that in step four, the drying temperature is 100-150℃, the drying time is 24-48h, and the thickness of the coated surface dense layer is 50-100μm.

[0023] In any of the above schemes, preferably, in step five, the degreasing process of the silicon-based ceramic core blank is as follows: the silicon-based ceramic core blank is placed in a degreasing furnace and heated from room temperature to 100-200℃ at a heating rate of 1-5℃ / min, and held at that temperature for 1-2 hours; the sintering process of the silicon-based ceramic core blank is as follows: the degreased silicon-based ceramic core blank is placed in a sintering furnace and heated from room temperature to 1200-1450℃ at a heating rate of 5-10℃ / min, held at that temperature for 3-8 hours, and then cooled to room temperature at a cooling rate of 1-5℃ / min.

[0024] In this invention, the mixers, injection molding machines, degreasing furnaces, sintering furnaces, drying ovens, spray granulators, spraying equipment, and ultrasonic equipment used are all existing equipment, and there are no special requirements for their structure or models. The manufacturing process of the ceramic core mold is a traditional process, with no special requirements for the process flow, process parameters, mold materials, or manufacturing equipment. The die-casting process of the ceramic core blank is also a traditional process, with no special requirements for the process flow, process parameters, or die-casting equipment; it is only necessary to ensure that the key die-casting parameters such as die-casting pressure, die-casting temperature, mold temperature, and holding time meet the requirements of this invention. The spraying process of the surface dense layer is also a traditional process, with no special requirements for the process flow or process parameters; it is only necessary to ensure that the thickness of the surface dense layer meets the requirements of this invention.

[0025] This invention provides a silicon-based ceramic core with high-temperature strength yielding properties and its preparation method, which solves the technical problems in the prior art such as the mismatch between the high-temperature strength of the ceramic core and the solidification stress of the alloy liquid, which easily leads to hot cracking of the casting, recrystallization of the inner cavity, core leakage and core deviation, and difficulty in core removal.

[0026] This invention innovatively designs the microstructure of a silicon-based ceramic core, which includes a core substrate, strength relief units, and a surface dense layer. The strength relief units are uniformly embedded inside the core substrate, and the surface dense layer is uniformly coated on the outer surface of the core substrate and tightly bonded to the core substrate.

[0027] This invention utilizes the high-temperature controllable deformation and decomposition characteristics of the strength relief unit to achieve precise design of the high-temperature strength of the ceramic core, ensuring it matches or approaches the stress during the solidification process of the alloy liquid. This reduces the core's obstruction to the solidification of the casting, decreases internal stress in the casting, and prevents hot cracking. Simultaneously, the decomposition of the strength relief unit forms numerous micropores, significantly improving core removal efficiency and effectively solving problems such as hot cracking, internal recrystallization, and core leakage / eccentricity in the casting, meeting the stringent requirements for directional solidification of single-crystal blades.

[0028] The present invention relates to a silicon-based ceramic core with high-temperature strength yielding properties and its preparation method, which has the following beneficial effects: (1) The present invention innovatively designs an embedded strength relief unit, which utilizes the decomposition characteristics of high-temperature decomposable composite ceramic microspheres and the buffering effect of elastic binder to achieve precise design of high-temperature strength of ceramic core, so that it is consistent with or close to the stress during the solidification process of alloy liquid, which can effectively reduce the hindering effect of core on casting solidification, reduce internal stress of casting, and fundamentally solve technical problems such as hot cracking and internal cavity recrystallization of casting.

[0029] (2) The present invention has a dense surface layer with a high temperature strength higher than that of the core matrix, which can effectively prevent the high temperature alloy liquid from penetrating into the core, avoid defects such as core leakage and core deviation during the casting process, and improve the casting qualification rate. At the same time, the high temperature decomposable composite ceramic microspheres in the embedded strength relief unit gradually decompose during the shell heating process before directional solidification, release gas and form a large number of uniformly distributed micropores. The released gas can be completely removed by vacuuming the melting furnace, which reduces the density of the core and greatly improves the core removal efficiency after casting. There is no need for a complicated core removal process, which reduces the production process and production cost, and can avoid mechanical damage to the blade cavity during the core removal process.

[0030] (3) By adjusting the material type and mass ratio of the core matrix, this invention improves the high-temperature stability and creep resistance of the core, enabling it to adapt to the high-temperature conditions of 1500-1650℃ during the directional solidification of single-crystal blades, thus preventing the core from deforming or breaking at high temperatures. At the same time, the dense surface layer is tightly bonded to the core matrix, further enhancing the stability of the overall core structure and extending its service life.

[0031] (4) The preparation method of the present invention is based on the existing ceramic core production equipment, without the need for additional complex equipment. The process steps are clear and controllable. Large-scale production can be achieved by adjusting the raw material ratio and process parameters, which is suitable for industrial batch preparation needs and has good industrialization prospects. Attached Figure Description

[0032] Figure 1 Photograph of the core matrix slurry prepared according to a preferred embodiment of the silicon-based ceramic core with high-temperature strength yielding properties and its preparation method of the present invention; Figure 2 for Figure 1 Photograph of the strength relief unit prepared in the embodiment shown; Figure 3 for Figure 1 Photographs of the surface-dense slurry prepared in the illustrated embodiment; Figure 4 for Figure 1 Photograph of the high-temperature decomposable composite ceramic microspheres prepared in the example shown; Figure 5 for Figure 1 Photograph of the silicon-based ceramic core preform prepared in the illustrated embodiment; Figure 6 for Figure 1 Photograph of the silicon-based ceramic core prepared in the illustrated embodiment; Figure 7 The image shows a partial photograph of the blade prepared in Example 1, wherein: (a) there is no recrystallization, and (b) there is no eccentricity. Figure 8The following are partial photographs of the blade prepared for Comparative Example 2, in which: (a) recrystallization is present, and (b) thermal cracking is present. Figure 9 The following are partial photographs of the blade prepared for Comparative Example 3, in which: (a) eccentricity, (b) core leakage. Detailed Implementation

[0033] To further understand the invention, the following detailed description of the invention will be provided in conjunction with specific embodiments.

[0034] Example 1: According to a preferred embodiment of the silicon-based ceramic core with high-temperature strength yielding properties of the present invention, the silicon-based ceramic core includes a core substrate, strength yielding units, and a surface dense layer. The strength yielding units are uniformly embedded in the interior of the core substrate, and the surface dense layer is uniformly covered on the outer surface of the core substrate and tightly bonded to the core substrate. The mass ratio of the core substrate to the strength yielding units is 4.3:1, and the thickness of the surface dense layer is 75 μm.

[0035] The mass percentages of each substance in the core matrix are as follows: 68 wt% silica powder, 20 wt% alumina powder, 4 wt% mineralizer, 5 wt% binder, and 3 wt% sintering aid. The mineralizer is composed of zirconium silicate and yttrium oxide, with a mass ratio of zirconium silicate to yttrium oxide of 1:1. The binder is composed of silica sol and polyvinyl alcohol, with a mass ratio of silica sol to polyvinyl alcohol of 4:1. The sintering aid is composed of zinc borate, neodymium oxide, scandium oxide, yttrium oxide, and lanthanum oxide. The sum of the masses of zinc borate, neodymium oxide, and scandium oxide is 70 wt%, yttrium oxide is 15 wt%, and lanthanum oxide is 15 wt%. The mass ratio of zinc borate, neodymium oxide, and scandium oxide is 1.8:1.2:1.

[0036] The silica powder comprises three particle sizes, with each particle size accounting for the following percentages by mass: 30 wt% for particles ≤ 65 μm, 45 wt% for particles ≤ 40 μm, and 25 wt% for particles ≤ 25 μm. The alumina powder has a particle size of 12 μm, and the sintering aid has a particle size of 5 μm.

[0037] The strength yielding unit is composed of high-temperature decomposable composite ceramic microspheres and an elastic binder, with a mass ratio of 3.2:1 between the high-temperature decomposable composite ceramic microspheres and the elastic binder; the particle size of the strength yielding unit is 0.3 mm. The mass percentage of each substance in the high-temperature decomposable composite ceramic microspheres is as follows: 50 wt% calcium carbonate-zirconia composite microspheres, 15 wt% volcanic ash microspheres, 20 wt% hydroxyapatite microspheres, and 15 wt% biphasic calcium phosphate microspheres. The elastic binder is nano-modified silicone rubber.

[0038] The dense surface layer is composed of alumina powder and sol components, with the mass ratio of alumina powder to sol components being 4:1; the sol components are composed of yttrium sol, aluminum sol, and silica sol, with the mass ratio of yttrium sol, aluminum sol, and silica sol being 1:0.8:2.3; and the alumina powder has a particle size of 0.5 μm.

[0039] This embodiment also provides a method for preparing a silicon-based ceramic core with high-temperature strength yielding properties, the preparation method comprising the following steps in sequence: Step 1: Prepare the core matrix slurry, strength relief unit, and surface dense layer slurry according to the preset material ratio and process parameters; Step 2: Place the strength relief unit into the core matrix slurry and stir evenly to obtain a mixed slurry; Step 3: The mixed slurry is injected into the ceramic core mold using a pressure injection machine for filling and die casting to obtain a wet blank of silicon-based ceramic core; Step 4: Apply a dense surface slurry to the outer surface of the wet silicon-based ceramic core blank using a spraying device, and then dry it to obtain the silicon-based ceramic core blank. Step 5: The silicon-based ceramic core blank is subjected to degreasing and sintering treatment in sequence to obtain a silicon-based ceramic core with high-temperature strength yielding properties.

[0040] In step one, the preparation process of the core matrix slurry is as follows: First, zinc borate, neodymium oxide, scandium oxide, yttrium oxide, and lanthanum oxide are mixed evenly at room temperature to obtain a sintering aid; second, the plasticizer is placed in a mixer and heated to melt while stirring, at a heating temperature of 115℃, a stirring speed of 400 rpm, and a stirring time of 2 hours, so that the plasticizer is completely melted; then, silica powder, alumina powder, the mineralizing agent components zirconium silicate and yttrium oxide, and the sintering aid are added to the mixer and stirred for another 60 hours to ensure that all substances are mixed evenly; finally, the binder components silica sol and polyvinyl alcohol are added to the mixer and stirred for another 6 hours to ensure that all substances are mixed evenly, thus obtaining the core matrix slurry, which is then kept at a constant temperature for later use. The plasticizer is composed of paraffin wax, beeswax, and polyethylene, with a mass ratio of 1:1:1, and the amount of plasticizer added is 22 wt% of the total amount of all substances in the core matrix; The manufacturing process of the strength relief unit includes the following steps in sequence: Step 1.1: Preparation of calcium carbonate-zirconia composite microspheres: First, according to the mass ratio of calcium carbonate microspheres to zirconium sol of 1:6, the calcium carbonate microspheres and zirconium sol were placed in an ultrasonic container for ultrasonic dispersion at a frequency of 30 kHz for 45 min, so that the zirconium sol uniformly coated the calcium carbonate microspheres to obtain a composite slurry. Then, the composite slurry was placed in an oven for low-temperature curing at 70℃ for 2.5 h. Subsequently, it was placed in a heat treatment furnace for heat treatment at 215℃ for 1.5 h to solidify the zirconium oxide gel and obtain a composite powder. Finally, the composite powder was washed in an ethanol solution to remove residual sol, followed by freeze-drying at -25℃ for 36 h to obtain calcium carbonate-zirconia composite microspheres. Step 1.2: Mix calcium carbonate-zirconia composite microspheres, volcanic ash microspheres, hydroxyapatite microspheres, and biphasic calcium phosphate microspheres uniformly at room temperature to obtain high-temperature decomposable composite ceramic microspheres; Step 1.3: Place the high-temperature decomposable composite ceramic microspheres and nano-modified organosilicon rubber into a mixing container, stir at room temperature at a speed of 400 rpm for 5 hours to ensure uniform mixing of all materials and obtain the strength reduction unit slurry. Step 1.4: First, the strength yielding unit slurry is made into spherical particles with a particle size of 0.3 mm using a spray granulator. The atomizing disc speed is 10000 rpm, the inlet air temperature is 240℃, the outlet air temperature is 105℃, and the feed rate is 150 mL / min. Then, the spherical particles are placed in an oven for drying at 90℃ for 18 hours to obtain the strength yielding unit.

[0041] The preparation process of the surface dense layer slurry is as follows: first, yttrium sol, aluminum sol and silica sol are mixed at room temperature for 2 hours to obtain sol components, and then the sol components and alumina powder are mixed at room temperature for 35 minutes to make the substances evenly mixed, thus obtaining the surface dense layer slurry.

[0042] In step two, the mixing temperature of the strength relief unit and the core matrix slurry is room temperature, the mixing speed is 250 rpm, and the mixing time is 11 hours.

[0043] In step three, the die-casting parameters for the silicon-based ceramic core wet blank are: die-casting pressure 5MPa, die-casting temperature 100℃, mold temperature 35℃, and holding time 22s.

[0044] In step four, the drying temperature is 125℃, the drying time is 36h, and the thickness of the coated dense layer is 75μm.

[0045] In step five, the degreasing process of the silicon-based ceramic core blank is as follows: the silicon-based ceramic core blank is placed in a degreasing furnace and heated from room temperature to 150°C at a heating rate of 3°C / min, and held at that temperature for 1.5 hours; the sintering process of the silicon-based ceramic core blank is as follows: the degreased silicon-based ceramic core blank is placed in a sintering furnace and heated from room temperature to 1325°C at a heating rate of 8°C / min, held at that temperature for 5 hours, and then cooled to room temperature at a cooling rate of 3°C / min.

[0046] In this embodiment, the prepared core matrix slurry is as follows: Figure 1 As shown, the prepared strength relief unit is as follows Figure 2 As shown, the prepared surface-dense slurry is as follows: Figure 3 As shown, the prepared high-temperature decomposable composite ceramic microspheres are as follows: Figure 4 As shown, the prepared silicon-based ceramic core preform is as follows: Figure 5 As shown, the prepared silicon-based ceramic core is as follows: Figure 6 As shown.

[0047] This embodiment has the following beneficial effects: (1) An embedded strength relief unit is designed, which utilizes the decomposition characteristics of high-temperature decomposable composite ceramic microspheres and the buffering effect of elastic binder to achieve precise design of the high-temperature strength of the ceramic core, so that it is consistent with or close to the stress during the solidification process of the alloy liquid, effectively reducing the hindering effect of the core on the solidification of the casting, reducing the internal stress of the casting, and fundamentally solving the technical problems of hot cracking and recrystallization of the casting cavity. (2) A surface dense layer is set, whose high-temperature strength is higher than that of the core matrix, which can effectively prevent the high-temperature alloy liquid from penetrating into the core, avoiding defects such as core leakage and core deviation during the pouring process; the high-temperature decomposable composite ceramic microspheres in the strength relief unit gradually decompose during the shell heating process before directional solidification, release gas and form a large number of uniformly distributed micropores, and the released gas can be completely removed by vacuuming the melting furnace, reducing the core density and greatly improving the core removal efficiency after casting. (3) The surface dense layer is tightly bonded to the core matrix, which enhances the stability of the overall core structure and extends its service life.

[0048] Example 2: According to another preferred embodiment of the silicon-based ceramic core with high-temperature strength yielding properties and its preparation method, its structural design, material selection for each module, preparation process, technical principle, and beneficial effects are basically the same as those in Embodiment 1, except that: The mass ratio of the core matrix to the strength relief unit is 3:1, and the thickness of the surface dense layer is 50μm.

[0049] The mass percentages of each substance in the core matrix are as follows: 60 wt% silica powder, 25 wt% alumina powder, 2 wt% mineralizer, 8 wt% binder, and 5 wt% sintering aid. The mineralizer has a zirconium silicate to yttrium oxide mass ratio of 1:0.8; the binder has a silica sol to polyvinyl alcohol mass ratio of 3:1. The sintering aid is composed of zinc borate, neodymium oxide, scandium oxide, yttrium oxide, and lanthanum oxide. The sum of the masses of zinc borate, neodymium oxide, and scandium oxide is 65 wt%, yttrium oxide is 18 wt%, and lanthanum oxide is 17 wt%. The mass ratio of zinc borate, neodymium oxide, and scandium oxide is 1.5:1:1.

[0050] The percentage of each particle size in the silica powder is as follows: 40μm ≤ particle size ≤ 65μm accounts for 25wt%, 25μm ≤ particle size < 40μm accounts for 48wt%, and 10μm ≤ particle size < 25μm accounts for 27wt%; the alumina powder has a particle size of 5μm, and the sintering aid has a particle size of 1μm.

[0051] The mass ratio of the high-temperature decomposable composite ceramic microspheres to the elastic binder in the strength relief unit is 2.5:1; the particle size of the strength relief unit is 0.1 mm. The mass percentage of each substance in the high-temperature decomposable composite ceramic microspheres is as follows: calcium carbonate-zirconia composite microspheres 45 wt%, volcanic ash microspheres 20 wt%, hydroxyapatite microspheres 15 wt%, and biphasic calcium phosphate microspheres 20 wt%. The elastic binder is nano-modified silicone rubber.

[0052] The mass ratio of alumina powder to sol component in the dense surface layer is 3.5:1; the mass ratio of yttrium sol, aluminum sol, and silica sol in the sol component is 1:0.5:1.5; and the particle size of the alumina powder is 0.1 μm.

[0053] In step one, the preparation process of the core matrix slurry includes the following main parameters: the plasticizer is heated to 100℃, the stirring speed is 300rpm, and the stirring time is 3h; silica powder, alumina powder, mineralizing agents zirconium silicate and yttrium oxide, and sintering aids are added to a mixer and stirred for 48h; the binder components silica sol and polyvinyl alcohol are added to a mixer and stirred for 4h to ensure uniform mixing. The amount of plasticizer added is 15wt% of the total amount of all substances in the core matrix. The preparation process of the strength yielding unit includes the following main parameters: Step 1.1, preparing calcium carbonate-zirconia composite microspheres: according to the mass ratio of calcium carbonate microspheres to zirconium sol 1:4, the two are placed in an ultrasonic container for ultrasonic dispersion, with an ultrasonic vibration frequency of 20kHz and an ultrasonic dispersion time of 60min; the composite slurry is placed in an oven for low-temperature curing, with a drying temperature of 60℃ and a drying time of 3h, followed by heat treatment at a temperature of 180℃ and a heat treatment time of 2h; the composite powder is placed in an ethanol solution to remove residual sol, followed by freeze-drying at a freeze-drying temperature of -30℃ and a freeze-drying time of 24h. Step 1.3, placing high-temperature decomposable composite ceramic microspheres and nano-modified organosilicon rubber in a stirring container and stirring at room temperature at a stirring speed of 300rpm for 6h. Step 1.4: The strength yielding unit slurry is made into spherical particles with a particle size of 0.1 mm using a spray granulator. The atomizing disc speed is 8000 rpm, the inlet air temperature is 180℃, the outlet air temperature is 90℃, and the feeding speed is 100 mL / min. The drying temperature of the spherical particles is 80℃, and the drying time is 24 h.

[0054] The preparation process of the surface dense layer slurry includes the following main parameters: yttrium sol, aluminum sol and silica sol are mixed at room temperature for 1 hour to obtain sol component, and sol component and alumina powder are mixed at room temperature for 30 minutes to obtain surface dense layer slurry.

[0055] In step two, the mixing speed of the strength relief unit and the core matrix slurry is 200 rpm, and the mixing time is 12 h.

[0056] In step three, the die-casting parameters for the silicon-based ceramic core wet blank are: die-casting pressure 3MPa, die-casting temperature 80℃, mold temperature 25℃, and holding time 30s.

[0057] In step four, the drying temperature is 100℃, the drying time is 48h, and the thickness of the coated dense layer is 50μm.

[0058] In step five, the degreasing process of the silicon-based ceramic core blank is as follows: the silicon-based ceramic core blank is placed in a degreasing furnace and heated from room temperature to 100°C at a heating rate of 1°C / min, and held for 2 hours; the sintering process of the silicon-based ceramic core blank is as follows: the degreased silicon-based ceramic core blank is placed in a sintering furnace and heated from room temperature to 1200°C at a heating rate of 5°C / min, held for 8 hours, and then cooled to room temperature at a cooling rate of 1°C / min.

[0059] Example 3: According to another preferred embodiment of the silicon-based ceramic core with high-temperature strength yielding properties and its preparation method, its structural design, material selection for each module, preparation process, technical principle, and beneficial effects are basically the same as those in Embodiment 1, except that: The mass ratio of the core matrix to the strength relief unit is 5.6:1, and the thickness of the surface dense layer is 100μm.

[0060] The mass percentages of each substance in the core matrix are as follows: 75 wt% silica powder, 15 wt% alumina powder, 5 wt% mineralizer, 3 wt% binder, and 2 wt% sintering aid. The mineralizer has a zirconium silicate to yttrium oxide mass ratio of 1:1.2; the binder has a silica sol to polyvinyl alcohol mass ratio of 5:1. The sintering aid is composed of zinc borate, neodymium oxide, scandium oxide, yttrium oxide, and lanthanum oxide. The sum of the masses of zinc borate, neodymium oxide, and scandium oxide is 75 wt%, yttrium oxide is 12 wt%, and lanthanum oxide is 13 wt%. The mass ratio of zinc borate, neodymium oxide, and scandium oxide is 2:1.5:1.

[0061] The percentage of each particle size in the silica powder is as follows: 40μm ≤ particle size ≤ 65μm accounts for 35wt%, 25μm ≤ particle size < 40μm accounts for 43wt%, and 10μm ≤ particle size < 25μm accounts for 22wt%; the alumina powder has a particle size of 20μm, and the sintering aid has a particle size of 10μm.

[0062] The mass ratio of the high-temperature decomposable composite ceramic microspheres to the elastic binder in the strength relief unit is 4:1; the particle size of the strength relief unit is 0.5 mm. The mass percentage of each substance in the high-temperature decomposable composite ceramic microspheres is as follows: calcium carbonate-zirconia composite microspheres 55 wt%, volcanic ash microspheres 10 wt%, hydroxyapatite microspheres 25 wt%, and biphasic calcium phosphate microspheres 10 wt%. The elastic binder is nano-modified silicone rubber.

[0063] The mass ratio of alumina powder to sol component in the dense surface layer is 4.5:1; the mass ratio of yttrium sol, aluminum sol, and silica sol in the sol component is 1:1:3; and the particle size of the alumina powder is 1 μm.

[0064] In step one, the preparation process of the core matrix slurry includes the following main parameters: the plasticizer is heated to 130℃, the stirring speed is 500 rpm, and the stirring time is 1 hour; silica powder, alumina powder, mineralizing agents zirconium silicate and yttrium oxide, and sintering aids are added to a mixer and stirred for 72 hours; the binder components silica sol and polyvinyl alcohol are added to a mixer and stirred for 8 hours to ensure uniform mixing. The amount of plasticizer added is 30 wt% of the total amount of all substances in the core matrix. The preparation process of the strength yielding unit includes the following main parameters: Step 1.1, preparing calcium carbonate-zirconia composite microspheres: according to the mass ratio of calcium carbonate microspheres to zirconium sol 1:8, the two are placed in an ultrasonic container for ultrasonic dispersion, with an ultrasonic vibration frequency of 40kHz and an ultrasonic dispersion time of 30min; the composite slurry is placed in an oven for low-temperature curing, with a drying temperature of 80℃ and a drying time of 2h, followed by heat treatment at a temperature of 250℃ and a heat treatment time of 1h; the composite powder is placed in an ethanol solution to remove residual sol, followed by freeze-drying at a freeze-drying temperature of -20℃ and a freeze-drying time of 48h. Step 1.3, placing high-temperature decomposable composite ceramic microspheres and nano-modified organosilicon rubber in a stirring container and stirring at room temperature at a stirring speed of 500rpm for 4h. Step 1.4: The strength yielding unit slurry is made into spherical particles with a particle size of 0.5 mm using a spray granulator. The atomizing disc speed is 12000 rpm, the inlet air temperature is 300℃, the outlet air temperature is 120℃, and the feeding speed is 200 mL / min. The drying temperature of the spherical particles is 100℃, and the drying time is 12 h.

[0065] The preparation process of the surface dense layer slurry includes the following main parameters: yttrium sol, aluminum sol and silica sol are mixed at room temperature for 3 hours to obtain sol components, and sol components and alumina powder are mixed at room temperature for 40 minutes to obtain surface dense layer slurry.

[0066] In step two, the mixing speed of the strength relief unit and the core matrix slurry is 300 rpm, and the mixing time is 10 h.

[0067] In step three, the die-casting parameters for the silicon-based ceramic core wet blank are: die-casting pressure 8MPa, die-casting temperature 120℃, mold temperature 45℃, and holding time 15s.

[0068] In step four, the drying temperature is 150℃, the drying time is 24h, and the thickness of the coated dense layer is 100μm.

[0069] In step five, the degreasing process of the silicon-based ceramic core blank is as follows: the silicon-based ceramic core blank is placed in a degreasing furnace and heated from room temperature to 200°C at a heating rate of 5°C / min, and held at that temperature for 1 hour; the sintering process of the silicon-based ceramic core blank is as follows: the degreased silicon-based ceramic core blank is placed in a sintering furnace and heated from room temperature to 1450°C at a heating rate of 10°C / min, held at that temperature for 3 hours, and then cooled to room temperature at a cooling rate of 5°C / min.

[0070] Comparative Example 1: This comparative example is a traditional ceramic core, which only includes the core matrix and the surface dense layer, without embedded strength relief units. The selection of raw materials, material ratios, preparation processes, and preparation methods of the ceramic core for the core matrix and the surface dense layer are basically the same as those in Example 1.

[0071] Comparative Example 2: The ceramic core of this comparative example includes a core matrix, a strength relief unit, and a surface dense layer. The selection of raw materials, material ratios, preparation processes, and preparation methods of the ceramic core for the core matrix and surface dense layer are basically the same as those in Example 1. However, the strength relief unit only contains volcanic ash microspheres, hydroxyapatite microspheres, and biphasic calcium phosphate microspheres, and does not contain calcium carbonate-zirconia composite microspheres or nano-modified silicone rubber.

[0072] Comparative Example 3: The ceramic core of this comparative example includes a core matrix and a strength relief unit, without a surface dense layer. The selection of raw materials, material ratios, preparation processes, and preparation methods of the ceramic core for the core matrix and strength relief unit are basically the same as those in Example 1.

[0073] Performance tests were conducted on the above embodiments and comparative examples under the same test conditions, environment, and equipment. The test results are shown in Table 1. A partial photograph of the blade prepared in Example 1 is shown below. Figure 7 As shown, (a) no recrystallization, (b) no eccentricity; a partial photograph of the blade prepared in Comparative Example 2 is shown. Figure 8 As shown, (a) shows recrystallization, and (b) shows thermal cracking; a partial photograph of the blade prepared in Comparative Example 3 is shown. Figure 9As shown, (a) off-center core, (b) leaky core.

[0074] Notes: (1) The alloy used in the test is a single crystal high temperature alloy with a solidification stress of 48 MPa; (2) The core removal efficiency is the time required for the core to be completely removed using the conventional alkaline core removal method; (3) The core leakage / eccentricity rate, casting hot crack rate, and internal cavity recrystallization rate are all statistical results after testing 100 single crystal blades.

[0075] From Table 1 and Figures 7-9 The comparison shows that the difference between the high-temperature strength and the solidification stress of the alloy liquid in the silicon-based ceramic cores prepared in the three embodiments does not exceed 12MPa, achieving precise matching. Therefore, the hot cracking rate and recrystallization rate of the casting are both 0, and there is no core leakage or core deviation. The core removal efficiency is only 2-3h, and the overall performance is excellent.

[0076] The ceramic core (without strength relief unit) in Comparative Example 1 has excessively high high-temperature strength, with a difference of 27 MPa between it and the solidification stress of the alloy, resulting in a hot cracking rate of 18% and an internal recrystallization rate of 22% in the casting, as well as extremely low core removal efficiency (8.5h).

[0077] In Comparative Example 2, the ceramic core (lacking an elastic binder in the strength concession unit and calcium carbonate-zirconia composite microspheres in the high-temperature decomposable composite ceramic microspheres) exhibited a high temperature strength-to-solidification stress difference of 20 MPa due to the lack of elastic buffering. This resulted in some casting hot cracking and internal cavity recrystallization issues, highlighting the crucial role of the elastic binder in stress buffering. Furthermore, the absence of the key component, calcium carbonate-zirconia composite microspheres, led to poorer overall performance.

[0078] The ceramic core of Comparative Example 3 (without a dense surface layer) did not exhibit recrystallization or hot cracking, but its core leakage / eccentricity rate reached 15%, resulting in a low casting qualification rate. This demonstrates the important role of the dense surface layer in preventing alloy melt from seeping in and avoiding core leakage / eccentricity.

[0079] In summary, the three embodiments, through the synergistic design of the core matrix, strength relief unit, and surface dense layer, achieve multiple requirements such as matching high-temperature strength with the solidification stress of the alloy liquid, preventing core leakage and core deviation, and facilitating core detachment, thus overcoming the technical defects of existing ceramic cores.

[0080] The raw materials used in the above embodiments and comparative examples were purchased from Aladdin Reagent Co., Ltd. and Sinopharm Chemical Reagent Co., Ltd.

[0081] Special Note: The technical solution of this invention involves numerous parameters, and the synergistic effects between these parameters must be comprehensively considered to achieve the beneficial effects and significant progress of this invention. Furthermore, the value ranges of each parameter in the technical solution were obtained through extensive experimentation. For each parameter and the combinations thereof, the inventors have recorded a large amount of experimental data; however, due to space limitations, the specific experimental data is not disclosed here.

[0082] It will be readily understood by those skilled in the art that this invention includes any combination of the inventive description and specific embodiments outlined in the foregoing specification, as well as the various parts shown in the accompanying drawings. Due to space limitations and for the sake of brevity, not all of these combinations have been described in detail. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A silicon-based ceramic core with high-temperature strength yielding properties, characterized in that, The silicon-based ceramic core includes a core substrate, strength relief units, and a surface dense layer. The strength relief units are uniformly embedded inside the core substrate, and the surface dense layer is uniformly covered on the outer surface of the core substrate and is tightly bonded to the core substrate. The mass ratio of the core substrate to the strength relief units is 3-5.6:1, and the thickness of the surface dense layer is 50-100 μm.

2. The silicon-based ceramic core with high-temperature strength yielding properties according to claim 1, characterized in that, The mass percentage of each substance in the core matrix is ​​as follows: 60-75 wt% silica powder, 15-25 wt% alumina powder, 2-5 wt% mineralizer, 3-8 wt% binder, and 1-5 wt% sintering aid.

3. The silicon-based ceramic core with high-temperature strength yielding properties according to claim 2, characterized in that, The mineralizing agent is composed of zirconium silicate and yttrium oxide, wherein the mass ratio of zirconium silicate to yttrium oxide is 1:0.8-1.2; The binder is composed of silica sol and polyvinyl alcohol, with the mass ratio of silica sol to polyvinyl alcohol being 3-5:1; the sintering aid is composed of zinc borate, neodymium oxide, scandium oxide, yttrium oxide, and lanthanum oxide, with the total mass of zinc borate, neodymium oxide, and scandium oxide accounting for 65-75 wt%, yttrium oxide accounting for 10-20 wt%, and lanthanum oxide accounting for 10-20 wt%, and the mass ratio of zinc borate, neodymium oxide, and scandium oxide being 1.5-2:1-1.5:

1.

4. The silicon-based ceramic core with high-temperature strength yielding properties according to claim 3, characterized in that, The silica powder comprises three particle sizes, with each particle size accounting for the following percentages by mass: 40μm≤particle size≤65μm accounts for 25-35wt%, 25μm≤particle size<40μm accounts for 38-50wt%, and 10μm≤particle size<25μm accounts for 20-30wt%. The alumina powder has a particle size of 5-20μm, and the sintering aid has a particle size of 1-10μm.

5. The silicon-based ceramic core with high-temperature strength yielding properties according to claim 4, characterized in that, The strength yielding unit is composed of high-temperature decomposable composite ceramic microspheres and an elastic binder, with a mass ratio of 2.5-4:1 between the high-temperature decomposable composite ceramic microspheres and the elastic binder; the particle size of the strength yielding unit is 0.1-0.5 mm.

6. The silicon-based ceramic core with high-temperature strength yielding properties according to claim 5, characterized in that, The mass percentages of each substance in the high-temperature decomposable composite ceramic microspheres are as follows: calcium carbonate-zirconia composite microspheres 45-55 wt%, volcanic ash microspheres 10-20 wt%, hydroxyapatite microspheres 15-25 wt%, and biphasic calcium phosphate microspheres 10-20 wt%; the elastic binder is nano-modified silicone rubber.

7. The silicon-based ceramic core with high-temperature strength yielding properties according to claim 6, characterized in that, The dense surface layer is composed of alumina powder and sol components, with the mass ratio of alumina powder to sol components being 3.5-4.5:1; the sol components are composed of yttrium sol, aluminum sol, and silica sol, with the mass ratio of yttrium sol, aluminum sol, and silica sol being 1:0.5-1:1.5-3; the particle size of the alumina powder is 0.1-1 μm.

8. A method for preparing a silicon-based ceramic core with high-temperature strength yielding properties according to any one of claims 1-7, characterized in that, The preparation method includes the following steps in sequence: Step 1: Prepare the core matrix slurry, strength relief unit, and surface dense layer slurry according to the preset material ratio and process parameters; Step 2: Place the strength relief unit into the core matrix slurry and stir evenly to obtain a mixed slurry; Step 3: The mixed slurry is injected into the ceramic core mold using a pressure injection machine for filling and die casting to obtain a wet blank of silicon-based ceramic core; Step 4: Apply a dense surface slurry to the outer surface of the wet silicon-based ceramic core blank using a spraying device, and then dry it to obtain the silicon-based ceramic core blank. Step 5: The silicon-based ceramic core blank is subjected to degreasing and sintering treatment in sequence to obtain a silicon-based ceramic core with high-temperature strength yielding properties.

9. The method for preparing a silicon-based ceramic core with high-temperature strength yielding properties according to claim 8, characterized in that, In step one, the preparation process of the core matrix slurry is as follows: First, zinc borate, neodymium oxide, scandium oxide, yttrium oxide, and lanthanum oxide are mixed evenly at room temperature to obtain a sintering aid; second, plasticizer is placed in a mixer and heated to melt while stirring, at a heating temperature of 100-130℃, a stirring speed of 300-500 rpm, and a stirring time of 1-3 hours, so that the plasticizer is completely melted; then, silica powder, alumina powder, the mineralizing agent components zirconium silicate and yttrium oxide, and the sintering aid are added to the mixer and stirring is continued for 48-72 hours to ensure that all substances are mixed evenly; finally, the binder components silica sol and polyvinyl alcohol are added to the mixer and stirring is continued for 4-8 hours to ensure that all substances are mixed evenly, thus obtaining the core matrix slurry, which is then kept warm for later use. The plasticizer is composed of paraffin wax, beeswax, and polyethylene, with a mass ratio of 1:1:

1. The amount of plasticizer added is 15-30 wt% of the total amount of each substance in the core matrix. The manufacturing process of the strength relief unit includes the following steps in sequence: Step 1.1: Preparation of calcium carbonate-zirconia composite microspheres: First, according to the mass ratio of calcium carbonate microspheres to zirconium sol of 1:4-8, the calcium carbonate microspheres and zirconium sol are placed in an ultrasonic container for ultrasonic dispersion at a frequency of 20-40 kHz for 30-60 min, so that the zirconium sol uniformly coats the calcium carbonate microspheres to obtain a composite slurry. Then, the composite slurry is placed in an oven for low-temperature curing at 60-80℃ for 2-3 h. Subsequently, it is placed in a heat treatment furnace for heat treatment at 180-250℃ for 1-2 h to solidify the zirconium oxide gel and obtain a composite powder. Finally, the composite powder is washed in an ethanol solution to remove residual sol, followed by freeze-drying at -30 to -20℃ for 24-48 h to obtain calcium carbonate-zirconia composite microspheres. Step 1.2: Mix calcium carbonate-zirconia composite microspheres, volcanic ash microspheres, hydroxyapatite microspheres, and biphasic calcium phosphate microspheres uniformly at room temperature to obtain high-temperature decomposable composite ceramic microspheres; Step 1.3: Place the high-temperature decomposable composite ceramic microspheres and nano-modified organosilicon rubber into a mixing container, stir at room temperature at a speed of 300-500 rpm for 4-6 hours to ensure uniform mixing of all materials and obtain the strength reduction unit slurry. Step 1.4: First, the strength yielding unit slurry is made into spherical particles with a particle size of 0.1-0.5mm using a spray granulator. The atomizing disc speed is 8000-12000rpm, the inlet air temperature is 180-300℃, the outlet air temperature is 90-120℃, and the feed rate is 100-200mL / min. Then, the spherical particles are placed in an oven for drying at a temperature of 80-100℃ for 12-24 hours to obtain the strength yielding unit. The preparation process of the surface dense layer slurry is as follows: first, yttrium sol, aluminum sol and silica sol are mixed at room temperature for 1-3 hours to obtain sol components, and then the sol components and alumina powder are mixed at room temperature for 30-40 minutes to make the substances evenly mixed, thus obtaining the surface dense layer slurry.

10. The method for preparing a silicon-based ceramic core with high-temperature strength yielding properties according to claim 8, characterized in that, In step two, the mixing temperature of the strength relief unit and the core matrix slurry is room temperature, the mixing speed is 200-300 rpm, and the mixing time is 10-12 hours. In step three, the die-casting parameters for the silicon-based ceramic core wet blank are: die-casting pressure 3-8MPa, die-casting temperature 80-120℃, mold temperature 25-45℃, and holding time 15-30s. In step four, the drying temperature is 100-150℃, the drying time is 24-48h, and the thickness of the coated dense layer is 50-100μm. In step five, the degreasing process of the silicon-based ceramic core blank is as follows: the silicon-based ceramic core blank is placed in a degreasing furnace and heated from room temperature to 100-200℃ at a heating rate of 1-5℃ / min, and held for 1-2 hours; the sintering process of the silicon-based ceramic core blank is as follows: the degreased silicon-based ceramic core blank is placed in a sintering furnace and heated from room temperature to 1200-1450℃ at a heating rate of 5-10℃ / min, held for 3-8 hours, and then cooled to room temperature at a cooling rate of 1-5℃ / min.

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