High-deformability ceramic core with compact surface and porous core structure and preparation method of high-deformability ceramic core

Abstract

The invention discloses a high-deformability ceramic core with a compact surface and a porous core structure and a preparation method of the high-deformability ceramic core. The ceramic core is formed by compounding a ceramic core with the porous core structure and a compact inert coating on the outer surface of the ceramic core, the ceramic core with the porous structure at the core part comprises the following substances in percentage by weight: 42 to 51 percent of ceramic powder component, 35 to 40 percent of hollow glass bead component, 4 to 9 percent of fiber component, 3 to 7 percent of graphite and 2 to 8 percent of starch; and the densified inert coating comprises the following substances in percentage by weight: 67 to 75 percent of sol component and 25 to 33 percent of nano powder component. The preparation method comprises the following steps: preparing a core porous structure ceramic core and densified inert coating slurry; and the ceramic core with the porous structure at the core part is impregnated with the densified inert coating slurry under sectional vacuum pressure in a gradient pressure reduction manner, and then is put into a heat treatment furnace for sintering treatment. The prepared ceramic core has excellent deformability, the problem of blade hot cracking can be solved, interface reaction can be avoided through the inert coating, and efficient depoling is facilitated through the porous structure of the core.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of ceramic core material design and preparation, and particularly relates to a high-sinkability ceramic core with a dense outer surface and a porous core, and a preparation method thereof. The technology is particularly suitable for the casting of complex internal cavity structure blades in hot end components such as aero-engines and gas turbines. BACKGROUND

[0002] In high-end equipment manufacturing industries such as aerospace and energy power, hot end components such as turbine blades of aero-engines and guide vanes of gas turbines, with the continuous improvement of the requirements of equipment on thrust-to-weight ratio and efficiency, their working environment is increasingly severe, and the structural design is also increasingly complex. In order to improve the cooling efficiency and mechanical properties of the blades, the internal cavity of the blade is often designed into a complex structure with multiple channels and multiple blind cavities, which puts forward high requirements on the ceramic core used for forming such a complex internal cavity structure. However, the traditional ceramic core has many technical problems in practical application.

[0003] Firstly, the high-temperature sinkability is insufficient. The traditional ceramic core is mostly dense or has a low porosity structure. During high-temperature casting, the metal liquid solidifies and shrinks, while the ceramic core cannot adapt to the alloy shrinkage due to its dense structure and poor high-temperature deformation ability, resulting in a large solidification stress in the internal cavity of the blade. In the corner, blind hole and other weak parts of the thin-walled and complex internal cavity blade, stress concentration easily causes solidification hot cracking or internal cavity metal recrystallization of the blade, reduces the mechanical properties of the blade, and leads to a high blade scrap rate of more than 30%.

[0004] Secondly, the interface reaction problem is prominent. With the increase of the turbine front temperature of the aero-engine, high-Hf alloy, high-Y alloy and cobalt-based alloy are widely used, but the active elements (such as Hf, Y and Co) in these alloys are easy to react with SiO2 and other components in the traditional silicon-based ceramic core, generate low-melting-point eutectic phases or brittle compounds, pollute the alloy matrix, form a hard and brittle layer at the interface, cause early cracking of the blade, and at the same time, damage the surface of the core, affect the size accuracy and aerodynamic performance of the internal cavity of the blade.

[0005] Furthermore, it is difficult to remove the core. The traditional ceramic core is often dense or has a low porosity to ensure dimensional stability, and the blade inner cavity is complex, with a large number of curved cavities, blind cavities and blind holes. Such a dense core structure makes it difficult for the core removal agent (such as a strong alkali solution) to penetrate. Therefore, it is necessary to prolong the core removal time, increase the core removal temperature or increase the concentration of the core removal agent, which not only increases the cost and energy consumption, but also may corrode the blade substrate. Even so, there are still more than 30% of the complex inner cavity structure blades with residual core problems, which further causes the blade inner cavity flow passage to be blocked, affects the cooling effect, and even causes the blade to overheat and fail. In the prior art, even if an improved ceramic core is used, it is difficult to balance multiple properties. For example: although some porous cores can improve the yield and core removal performance, they have a high surface activity and are prone to react with high-activity alloys; and although some surface-modified cores can reduce the risk of interfacial reaction, they are dense in the core and have insufficient yield. Therefore, developing a ceramic core with high yield, low surface activity and excellent core removal performance has become a key technical problem that needs to be solved in the field of precision casting technology. SUMMARY

[0006] To solve the problems in the prior art, the application provides a high-yield ceramic core with a dense outer surface and a porous core structure. The high-yield ceramic core is composed of a core porous structure ceramic core and a dense inert coating on the outer surface of the core. The mass percentage of each substance in the core porous structure ceramic core is as follows: ceramic powder component 42-51wt%, hollow glass bead component 35-40wt%, fiber component 4-9wt%, graphite 3-7wt%, and starch 2-8wt%. The mass percentage of each substance in the dense inert coating is as follows: sol component 67-75wt%, and nano-powder component 25-33wt%.

[0007] Preferably, the addition amount of the hollow glass bead component increases with the increase of the addition amount of the ceramic powder component. Within the mass percentage range of the hollow glass bead component and the ceramic powder component, when the addition amount of the ceramic powder component increases by 3wt%, the addition amount of the hollow glass bead component increases by 1.5-2wt%.

[0008] Preferably, in any of the above schemes, the mass percentage of each substance in the ceramic powder component is as follows: quartz glass powder 48-55wt%, white corundum powder 24-28wt%, and zirconium silicate powder 20-24wt%.

[0009] Preferably in any of the above solutions, the quartz glass powder, the white corundum powder and the zirconium silicate powder each comprises three particle sizes of 30-40 μm, 18-30 μm and 10-18 μm, and the mass ratio of the particle sizes of 30-40 μm, 18-30 μm and 10-18 μm is 2-3:1-2:1.

[0010] Preferably in any of the above solutions, the hollow glass microsphere component comprises hollow silica glass microspheres of 50-60 wt%, hollow alumina glass microspheres of 21-27 wt% and hollow zirconium silicate glass microspheres of 18-24 wt%.

[0011] Preferably in any of the above solutions, the hollow silica glass microspheres, the hollow alumina glass microspheres and the hollow zirconium silicate glass microspheres each comprises three particle sizes of 20-30 μm, 10-20 μm and 0-10 μm, and the mass ratio of the particle sizes of 20-30 μm, 10-20 μm and 0-10 μm is 2-3:1-2:1.

[0012] Preferably in any of the above solutions, the fiber component comprises short carbon fibers of 42-72 wt% and short aramid fibers of 28-58 wt%, and the diameters of the short carbon fibers and the short aramid fibers are controlled within a range of 2-8 μm, and the aspect ratios of the short carbon fibers and the short aramid fibers are controlled within a range of 10-25:1.

[0013] Preferably in any of the above solutions, the particle size of the graphite is controlled within a range of 1-5 μm.

[0014] Preferably in any of the above solutions, the sol component comprises silica sol of 42-47 wt%, aluminum sol of 30-35 wt% and yttrium sol of 21-25 wt%.

[0015] Preferably in any of the above solutions, the nano-powder component comprises nano-silicon dioxide of 24-31 wt%, nano-aluminum oxide of 17-24 wt%, nano-yttrium oxide of 10-17 wt% and nano-zirconium silicate of 34-41 wt%, and the particle sizes of the nano-silicon dioxide, the nano-aluminum oxide, the nano-yttrium oxide and the nano-zirconium silicate are controlled within a range of 10-30 nm.

[0016] The application further provides a preparation method of the high-ductility ceramic core with a compact outer surface and a porous core structure, which comprises the following steps in sequence: Step one: according to the design of the material ratio of each raw material for standby; Step two: according to the design of the process and parameters to prepare the core porous structure ceramic core; Step three: according to the design of the process and parameters to prepare the densification of inert coating slurry; Step four: using positioning fixture to suspend the core porous structure ceramic core in the vacuum impregnation equipment of the impregnation cavity, make the core porous structure ceramic core and the inner wall of the impregnation cavity keep appropriate gap, then slowly inject the densification of inert coating slurry into the impregnation cavity, until the densification of inert coating slurry completely immerse the core porous structure ceramic core; Step five: start the vacuum system of the vacuum impregnation equipment, using gradient pressure reduction method to make the core porous structure ceramic core impregnate the densification of inert coating slurry under the segmented vacuum pressure, make the densification of inert coating slurry fully penetrate into the pores of the outer surface of the core porous structure ceramic core, and form the densification of inert coating on its outer surface; Step six: put the core porous structure ceramic core with the attached densification of inert coating into the heat treatment furnace for sintering treatment, make the densification of inert coating and the outer surface of the core porous structure ceramic core tightly combined, that is, the outer surface of the core porous structure of high retractability ceramic core is prepared.

[0017] Preferably, in step two, the preparation method of the core porous structure ceramic core includes the following steps in order: Step 2.1: according to the design of the material ratio of each raw material for standby; Step 2.2: put all the quartz glass powder, white corundum powder and zirconium silicate powder of each grade particle size into the V-type mixer, mix at room temperature for 20-30 min, and the mixing speed is 100-200 r / min, so that the materials are uniformly mixed, and the ceramic powder component is prepared; Step 2.3: put all the hollow glass microspheres of silicon oxide, aluminum oxide and zirconium silicate into the V-type mixer, mix at room temperature for 20-30 min, and the mixing speed is 100-200 r / min, so that the materials are uniformly mixed, and the hollow glass microsphere component is prepared; Step 2.4: put the plasticizer into the blender, stir while heating, the stirring speed is 100-200 r / min, after the temperature is heated to 90-130℃, continue to stir for 20-30 min, so that it is completely melted; wherein, the addition amount of plasticizer is 15-25% of the mass of the core porous structure ceramic core, and the plasticizer is composed of 93wt% paraffin, 5wt% beeswax and 2wt% polyethylene; Step 2.5: keep the stirring temperature and stirring speed unchanged, add the ceramic powder component into the blender and continue to stir for 1-2 h, so that the materials are mutually fused; Step 2.6: Keep the stirring temperature and stirring speed unchanged, add the hollow glass bead component into the stirring machine and continue stirring for 1-2 h to make the substances fuse with each other; Step 2.7: Keep the stirring temperature and stirring speed unchanged, add the chopped carbon fiber and chopped aramid fiber into the stirring machine and continue stirring for 2-3 h to make the fiber components uniformly dispersed; Step 2.8: Keep the stirring temperature and stirring speed unchanged, add the graphite and starch into the stirring machine and continue stirring for 3-5 h to make the substances uniformly mixed, thereby preparing the ceramic core slurry; Step 2.9: Use the prepared ceramic core slurry to press the ceramic core green body, the pressing temperature is 90-130℃, the pressing pressure is 3-7 MPa, and the pressure holding time is 120-180 s; then put the ceramic core green body into a sintering furnace for low-temperature glue removal treatment and high-temperature sintering treatment, so that the organic matter in the ceramic core green body is decomposed and volatilized to form a porous structure, i.e. the core porous structure ceramic core is prepared.

[0018] The process system of the low-temperature glue removal treatment and high-temperature sintering treatment is as follows: put the ceramic core green body into the sintering furnace, first increase the temperature from room temperature to 400-600℃ at a rate of 5-10℃ / min, and keep the temperature for 10-20 h, i.e. complete the low-temperature glue removal treatment; then increase the temperature from 400-600℃ to 1100-1250℃ at a rate of 3-5℃ / min, keep the temperature for 4-8 h, and cool to room temperature with the furnace, i.e. complete the high-temperature sintering treatment; during the whole low-temperature glue removal treatment and high-temperature sintering treatment, no protective atmosphere is needed.

[0019] In any of the above schemes, preferably in step three, the preparation method of the densified inert coating slurry comprises the following steps in the order: Step 3.1: weigh each raw material according to the designed material ratio for standby; Step 3.2: put the silica sol, aluminum sol and yttrium sol into the stirring machine, stir at room temperature for 2-3 h at a stirring speed of 220-350 r / min, so that the substances are uniformly dispersed and fused, thereby preparing the sol component; Step 3.3: put the nano-silicon dioxide, nano-aluminum oxide, nano-yttrium oxide and nano-zirconium silicate into the V-type mixer, mix at room temperature for 20-30 min at a mixing speed of 100-200 r / min, so that the substances are uniformly mixed, thereby preparing the nano-powder component; Step 3.4: add the prepared nano-powder component into the stirring machine, and continue stirring with the sol component for 6-10 h to make the substances fuse with each other, thereby preparing the densified inert coating slurry.

[0020] In any of the above schemes, preferably, in step four, the densification inert coating slurry is slowly injected into the impregnation cavity until the liquid level of the densification inert coating slurry reaches a position 20-25 mm above the highest point of the core porous structure ceramic core.

[0021] In any of the above schemes, preferably, in step five, the core porous structure ceramic core is impregnated with the densification inert coating slurry under segmented vacuum pressure in a gradient pressure reduction mode, i.e. in three stages: first stage impregnation, 0.08 MPa≤ vacuum pressure < 0.1 MPa, impregnation time 2-5 min; second stage impregnation, 0.05 MPa≤ vacuum pressure < 0.08 MPa, impregnation time 10-15 min; third stage impregnation, 0.02 MPa≤ vacuum pressure < 0.05 MPa, impregnation time 5-8 min.

[0022] In the present application, the first stage impregnation can eliminate most of the free gas, the second stage impregnation can avoid the sudden expansion of the gas in the pores, and the third stage impregnation can ensure that the slurry fully penetrates into the pores.

[0023] In any of the above schemes, preferably, in step six, the sintering treatment temperature is 700-950℃ and the calcination treatment time is 3-6 h.

[0024] In the present application, the V-type mixer, stirrer, vacuum impregnation equipment, heat treatment furnace, core pressing machine, calcination furnace, etc. used are all conventional equipment, and there are no special requirements for the equipment structure and model. The positioning fixture used can be selected according to the actual situation. The quartz glass powder, white corundum powder and zirconium silicate powder all include three grades of particle size, i.e. particle size 30-40 μm, particle size 18-30 μm, particle size 10-18 μm, i.e. 30 μm≤ particle size ≤ 40 μm, 18 μm≤ particle size < 30 μm, 10 μm≤ particle size < 18 μm; the hollow glass microbeads of silicon oxide, aluminum oxide and zirconium silicate all include three grades of particle size, i.e. particle size 20-30 μm, particle size 10-20 μm, particle size 0-10 μm, i.e. 20 μm≤ particle size ≤ 30 μm, 10 μm≤ particle size < 20 μm, 0 μm < particle size < 10 μm; the particle size of nano-silicon dioxide, nano-aluminum oxide, nano-yttrium oxide and nano-zirconium silicate is controlled within the range of 10-30 nm, i.e. 10 nm≤ particle size ≤ 30 nm; the particle size of graphite is controlled within the range of 1-5 μm, i.e. 1 μm≤ particle size ≤ 5 μm. For each grade of particle size, the material obtained after the material passes through the upper and lower two screen holes in turn has a particle size between the upper and lower two screen holes, for example, the particle size 18-30 μm, i.e. the material obtained after the material passes through the 30 μm screen hole and the 18 μm screen hole in turn has a particle size between 18-30 μm.

[0025] In the present application, the hollow glass microsphere component is used to effectively improve the yielding property, collapsibility and easy removal of the ceramic core. The hollow silica glass microsphere and quartz glass powder have good thermal stability and low thermal expansion coefficient, can maintain structural stability at high temperature, and at the same time provide certain strength for the core; the hollow alumina glass microsphere and white corundum powder further enhance the high temperature strength of the core; the hollow zirconium silicate glass microsphere and zirconium silicate powder can improve the chemical stability of the material; graphite has a lubricating effect, which helps to improve the yielding property of the core and increase the porosity; starch decomposes to form pores at high temperature, increasing the porosity of the core; chopped carbon fiber and chopped aramid fiber can enhance the toughness of the core, prevent cracking, and increase the porosity.

[0026] In the present application, the silica sol, aluminum sol and yttrium sol play the role of binder in the coating, making the various nanoparticles tightly combined; the nanosilica, nanoalumina, nano yttria and nano zirconium silicate have high chemical stability and low activity, which can effectively isolate the contact between the high-activity alloy and the ceramic core matrix, and prevent interfacial reaction.

[0027] The present application has the following beneficial effects: (1) High yielding property: The core porous structure designed in the present application is the core of realizing high yielding property, which can fundamentally solve the problems of blade thermal cracking and internal cavity metal recrystallization. In the high-temperature casting environment, the core porous structure can realize active yielding in size through the compression and deformation of the pores, accurately matching the alloy solidification shrinkage requirement; at the same time, the porous structure makes the strength of the core decrease moderately with the increase of temperature, realizing strength yielding. This double yielding mechanism can effectively disperse and relieve the solidification stress in the blade internal cavity, especially in the stress concentration areas such as the corners and blind holes of thin-walled blades, which can completely avoid thermal cracking defects caused by excessive stress, and prevent the internal cavity metal from recrystallizing due to stress.

[0028] (2) Low interfacial reactivity: The densified inert coating of the present application has very low chemical activity, which can form an effective isolation layer between the ceramic core and the high-activity alloy. In the casting process, the coating can prevent the active elements in the alloy from reacting with the ceramic core matrix, ensuring that the microstructure and performance of the blade are not contaminated and damaged. For blades casted with high Hf alloy, the thickness of the interfacial reaction layer is reduced from 10-30 μm of traditional cores to less than 2 μm after using the ceramic core prepared by the present application, greatly improving the high-temperature performance and service life of the blade.

[0029] (3) Excellent core removal performance: The porous structure of the core facilitates the core removal process. During core removal, core removal agents such as alkali solution can quickly penetrate into the core through the porous structure, fully contact and react with the core material, causing the core to quickly collapse, achieving efficient core removal without residual core. Compared with traditional dense cores, the core removal time of the present invention can be shortened by more than 50%, and after core removal, there is no residual core in the blade cavity, and the surface quality is good, effectively improving the processing efficiency and quality of the blade. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 A microscopic photograph of a ceramic core with a porous core structure prepared according to a preferred embodiment of the present invention, wherein the ceramic core has a dense surface and a porous core structure, and a method for preparing the same; Figure 2 for Figure 1 Photographs of densified inert coating slurries prepared in the illustrated examples; Figure 3 for Figure 1 A photograph of the ceramic core (test rod) with a porous core structure in the embodiment shown before being immersed in the densified inert coating slurry; Figure 4 for Figure 1 A photograph of a ceramic core (test rod) having a porous core structure in the embodiment shown after being immersed in a densified inert coating slurry; Figure 5 for Figure 1 A photograph of the interface morphology between the ceramic core and the blade prepared in the embodiment shown; Figure 6 To adopt Figure 1 The ceramic core prepared in the embodiment shown is further used to cast blades, and the morphology of the blade cavity is shown in the figure.

[0031] Notes in the figure: 1-hollow glass microspheres, 2-pores. DETAILED DESCRIPTION

[0032] In order to further understand the content of the present invention, the present invention will be described in detail below with reference to specific embodiments.

[0033] Example 1: According to a preferred embodiment of the high-sink-resistance ceramic core with a dense outer core porous structure of the present application, the high-sink-resistance ceramic core is composed of a core porous structure ceramic core and a dense inert coating layer on the outer surface of the core porous structure ceramic core, the mass percentage of each substance in the core porous structure ceramic core is 42wt% of ceramic powder component, 35wt% of hollow glass microsphere component, 9wt% of fiber component, 7wt% of graphite, and 7wt% of starch, and the mass percentage of each substance in the dense inert coating layer is 67wt% of sol component and 33wt% of nano-powder component.

[0034] The addition amount of the hollow glass microsphere component increases with the increase of the addition amount of the ceramic powder component, and in the mass percentage range of the hollow glass microsphere component and the ceramic powder component, the addition amount of the hollow glass microsphere component increases by 1.5-2wt% when the addition amount of the ceramic powder component increases by 3wt%. In this embodiment, the ceramic powder component and the hollow glass microsphere component are both the minimum addition amount.

[0035] The mass percentage of each substance in the ceramic powder component is 48wt% of quartz glass powder, 28wt% of white corundum powder, and 24wt% of zirconium silicate powder. The quartz glass powder, the white corundum powder, and the zirconium silicate powder all include three grades of particle size, which are particle size 30-40μm, particle size 18-30μm, and particle size 10-18μm, and the mass ratio of the particle size 30-40μm, the particle size 18-30μm, and the particle size 10-18μm is 2:1:1.

[0036] The mass percentage of each substance in the hollow glass microsphere component is 50wt% of silicon oxide hollow glass microsphere, 27wt% of aluminum oxide hollow glass microsphere, and 23wt% of zirconium silicate hollow glass microsphere. The silicon oxide hollow glass microsphere, the aluminum oxide hollow glass microsphere, and the zirconium silicate hollow glass microsphere all include three grades of particle size, which are particle size 20-30μm, particle size 10-20μm, and particle size 0-10μm, and the mass ratio of the particle size 20-30μm, the particle size 10-20μm, and the particle size 0-10μm is 2:1:1.

[0037] The mass percentage of each substance in the fiber component is 42wt% of chopped carbon fiber and 58wt% of chopped aramid fiber; the diameter of the chopped carbon fiber and the chopped aramid fiber is controlled within the range of 2-8μm, and the aspect ratio is controlled within the range of 10-25:1. The particle size of the graphite is controlled within the range of 1-5μm.

[0038] The mass percentages of the various substances in the sol component are 42wt% silica sol, 34wt% alumina sol, and 24wt% yttrium sol. The mass percentages of the various substances in the nanopowder component are 24wt% nano-silicon dioxide, 18wt% nano-alumina, 17wt% nano-yttrium oxide, and 41wt% nano-zirconium silicate. The particle sizes of the nano-silicon dioxide, nano-alumina, nano-yttrium oxide, and nano-zirconium silicate are all controlled within the range of 10-30nm.

[0039] This embodiment also provides a method for preparing a highly yielding ceramic core having a dense outer surface and a porous inner structure. The method comprises the following steps in order: Step 1: Weigh all raw materials according to the designed material ratio; Step 2: Prepare a ceramic core with a porous core structure according to the designed process and parameters; Step 3: Prepare a densified inert coating slurry according to the designed process and parameters; Step 4: Use a positioning fixture to suspend the core porous structure ceramic core in the impregnation chamber of the vacuum impregnation equipment, so that the core porous structure ceramic core maintains an appropriate gap with the inner wall of the impregnation chamber, and then slowly inject the densified inert coating slurry into the impregnation chamber until the densified inert coating slurry completely immerses the core porous structure ceramic core; Step 5: Starting the vacuum system of the vacuum impregnation equipment, using a gradient pressure reduction method to impregnate the core porous structure ceramic core with the densified inert coating slurry under segmented vacuum pressure, so that the densified inert coating slurry fully penetrates the pores on the outer surface of the core porous structure ceramic core, forming a densified inert coating on the outer surface; Step 6: Place the core porous structure ceramic core with the densified inert coating in a heat treatment furnace for sintering, so that the densified inert coating is tightly bonded to the outer surface of the core porous structure ceramic core, thereby obtaining a high-yield ceramic core with a dense outer surface and a porous core structure.

[0040] In step 2, the method for preparing the ceramic core with a porous core structure includes the following steps in order: Step 2.1: Weigh all raw materials according to the designed material ratio; Step 2.2: Place all quartz glass powder, white corundum powder, and zirconium silicate powder of various particle sizes into a V-type mixer and mix them at room temperature for 20 minutes at a mixing speed of 200 r / min to uniformly mix the materials to obtain a ceramic powder component; Step 2.3: Put the silica hollow glass microspheres, alumina hollow glass microspheres, and zirconium silicate hollow glass microspheres of different sizes into a V-type mixer, mix at room temperature for 20 min at a mixing speed of 200 r / min, and mix the materials evenly to obtain a hollow glass microsphere component; Step 2.4: Put the plasticizer into a blender and stir while heating, the stirring speed is 200 r / min, continue to stir for 20 min after the temperature is heated to 90℃, so that it is completely melted; wherein the addition amount of plasticizer is 15% of the mass of the core porous structure ceramic core, and the plasticizer is composed of 93wt% paraffin, 5wt% beeswax and 2wt% polyethylene; Step 2.5: Keep the stirring temperature and stirring speed unchanged, add the ceramic powder component into the blender and continue to stir for 1h, so that the materials are fused with each other; Step 2.6: Keep the stirring temperature and stirring speed unchanged, add the hollow glass microsphere component into the blender and continue to stir for 1h, so that the materials are fused with each other; Step 2.7: Keep the stirring temperature and stirring speed unchanged, add the chopped carbon fiber and chopped aramid fiber into the blender and continue to stir for 2h, so that the fiber component is uniformly dispersed; Step 2.8: Keep the stirring temperature and stirring speed unchanged, add the graphite and starch into the blender and continue to stir for 3h, so that the materials are mixed evenly to obtain a ceramic core slurry; Step 2.9: Use the prepared ceramic core slurry to press the ceramic core blank, the pressing temperature is 90℃, the pressing pressure is 3MPa, and the holding time is 180s; then put the ceramic core blank into a sintering furnace for low-temperature glue removal treatment and high-temperature sintering treatment, so that the organic matter in the ceramic core blank is decomposed and volatilized to form a porous structure, that is, a core porous structure ceramic core is obtained.

[0041] The process system of low-temperature glue removal treatment and high-temperature sintering treatment is as follows: put the ceramic core blank into the sintering furnace, first increase the temperature from room temperature to 400℃ at a rate of 5℃ / min, and keep the temperature for 20h, that is, complete the low-temperature glue removal treatment; then increase the temperature from 400℃ to 1100℃ at a rate of 3℃ / min, keep the temperature for 8h, and cool to room temperature with the furnace, that is, complete the high-temperature sintering treatment; during the whole low-temperature glue removal treatment and high-temperature sintering treatment, no protective atmosphere is needed.

[0042] In step three, the preparation method of the densified inert coating slurry includes the following steps in the order: Step 3.1: Weigh each raw material according to the designed material ratio; Step 3.2: Put the silica sol, aluminum sol, and yttrium sol into a blender and stir at room temperature for 2h at a stirring speed of 350 r / min, so that the materials are uniformly dispersed and fused to obtain a sol component; Step 3.3: Place nano-silicon dioxide, nano-alumina, nano-yttrium oxide, and nano-zirconium silicate into a V-type mixer and mix them at room temperature for 20 minutes at a mixing speed of 200 r / min to uniformly mix the materials to obtain a nano-powder component; Step 3.4: Add the prepared nanopowder component into a blender and continue to stir with the sol component for 6 hours to allow the substances to blend with each other, thereby obtaining a densified inert coating slurry.

[0043] In step 4, the densified inert coating slurry is slowly injected into the impregnation chamber until the liquid level of the densified inert coating slurry reaches a position 20 mm above the highest point of the core porous structure ceramic core.

[0044] In step five, a gradient pressure reduction method is used to impregnate the core porous structure ceramic core with a densified inert coating slurry under segmented vacuum pressure, that is, the impregnation is divided into three stages: the first stage impregnation, 0.08MPa≤vacuum pressure<0.1MPa, the impregnation time is 2min; the second stage impregnation, 0.05MPa≤vacuum pressure<0.08MPa, the impregnation time is 10min; the third stage impregnation, 0.02MPa≤vacuum pressure<0.05MPa, the impregnation time is 5min.

[0045] In step six, the sintering temperature is 700° C. and the calcination time is 6 h.

[0046] The microstructure of the porous ceramic core prepared in this embodiment is as follows: Figure 1 As shown, it can be clearly seen that the core contains hollow glass beads 1 and pores 2. The designed core porous structure is the key to achieving high yield, which can fundamentally solve the problems of blade thermal cracking and inner cavity metal recrystallization. In a high-temperature casting environment, the core porous structure can achieve active dimensional yield through compression and deformation of the pores, accurately matching the alloy solidification shrinkage requirements. At the same time, the porous structure makes the core strength moderately decrease with increasing temperature, thereby achieving strength yield.

[0047] The densified inert coating slurry prepared in this embodiment is as follows Figure 2 As shown, the core porous structure ceramic core (test rod) before and after being impregnated with the densified inert coating slurry are shown in Figure 2. Figure 3 and Figure 4 shown.

[0048] The interface morphology between the ceramic core and the blade prepared in this embodiment is as follows Figure 5 As shown in the figure, no interface reaction occurs. The ceramic core prepared in this embodiment is used to further cast blades. The morphology of the blade cavity is as follows: Figure 6 As shown in the figure, it can be seen that no metal recrystallization occurs in the inner cavity of the blade.

[0049] The high-sacrifice ceramic core with a dense outer part and a porous core structure and the preparation method thereof have the following beneficial effects: high sacrifice, the designed core structure is the core of realizing high sacrifice, and the problems of blade thermal cracking and internal cavity metal recrystallization can be fundamentally solved; low interface reactivity, the dense inert coating has extremely low chemical activity, and an effective isolation layer can be formed between the ceramic core and the high-activity alloy; and excellent core removal performance, the porous structure of the core provides convenience for the core removal process.

[0050] Embodiment Two According to another preferred embodiment of the high-sacrifice ceramic core with a dense outer part and a porous core structure and the preparation method thereof, the material selection and ratio, the process flow and parameters, the technical principle, and the beneficial effects are basically the same as those of Embodiment One, except that: The mass percentage of each substance in the core structure ceramic core is 45wt% of the ceramic powder component, 36.5wt% of the hollow glass bead component, 8wt% of the fiber component, 6wt% of the graphite, and 4.5wt% of the starch. The mass percentage of each substance in the dense inert coating is 70wt% of the sol component and 30wt% of the nano-powder component. In this embodiment, when the addition amount of the ceramic powder component increases by 3wt%, the addition amount of the hollow glass bead component increases by 1.5wt% accordingly, and the increase is controlled within the range of 1.5-2wt%.

[0051] The mass percentage of each substance in the ceramic powder component is 50wt% of the quartz glass powder, 27wt% of the white corundum powder, and 23wt% of the zirconium silicate powder. The quartz glass powder, the white corundum powder, and the zirconium silicate powder all include three grades of particle sizes, and the mass ratio of the particle size of 30-40μm, the particle size of 18-30μm, and the particle size of 10-18μm is 2.5:1.5:1.

[0052] The mass percentage of each substance in the hollow glass bead component is 53wt% of the silica hollow glass bead, 25wt% of the alumina hollow glass bead, and 22wt% of the zirconium silicate hollow glass bead. The silica hollow glass bead, the alumina hollow glass bead, and the zirconium silicate hollow glass bead all include three grades of particle sizes, and the mass ratio of the particle size of 20-30μm, the particle size of 10-20μm, and the particle size of 0-10μm is 2.5:1.5:1.

[0053] The mass percentage of each substance in the fiber component is 52wt% of chopped carbon fiber and 48wt% of chopped aramid fiber; the diameter of the chopped carbon fiber and the chopped aramid fiber is controlled in the range of 2-8μm, and the aspect ratio is controlled in the range of 10-25:1. The particle size of the graphite is controlled in the range of 1-5μm.

[0054] The mass percentage of each substance in the sol component is 44wt% of silica sol, 33wt% of aluminum sol and 23wt% of yttrium sol. The mass percentage of each substance in the nano-powder component is 26wt% of nano-silicon dioxide, 20wt% of nano-aluminum oxide, 15wt% of nano-yttrium oxide and 39wt% of nano-zirconium silicate, and the particle size of each substance is controlled in the range of 10-30nm.

[0055] In step two, the preparation method of the core porous structure ceramic core comprises the following main parameters: step 2.2: put quartz glass powder, white corundum powder and zirconium silicate powder into a V-type mixer, mix at room temperature for 23min, and the mixing speed is 160r / min, to prepare a ceramic powder component; step 2.3: put hollow glass microspheres of silicon oxide, hollow glass microspheres of aluminum oxide and hollow glass microspheres of zirconium silicate into a V-type mixer, mix at room temperature for 23min, and the mixing speed is 160r / min, to prepare a hollow glass microsphere component; step 2.4: put 18% of the added amount of plasticizer into a stirrer, stir while heating, the stirring speed is 160r / min, continue to stir for 23min after the temperature is heated to 103℃; steps 2.5-2.8: keep the stirring temperature and stirring speed unchanged, add the ceramic powder component into the stirrer and continue to stir for 1.3h, add the hollow glass microsphere component into the stirrer and continue to stir for 1.3h, add the chopped carbon fiber and the chopped aramid fiber into the stirrer and continue to stir for 2.3h, add the graphite and the starch into the stirrer and continue to stir for 3.6h, to prepare a ceramic core slurry; step 2.9: use the ceramic core slurry to press a ceramic core blank, the pressing temperature is 103℃, the pressing pressure is 4MPa, and the pressure holding time is 160s, after low-temperature glue removal treatment and high-temperature sintering treatment, a core porous structure ceramic core is prepared.

[0056] The process system of the low-temperature glue removal treatment and the high-temperature sintering treatment is as follows: put the ceramic core blank into a sintering furnace, first increase the temperature from room temperature to 460℃ at a rate of 7℃ / min, keep the temperature for 16h, which is the low-temperature glue removal treatment; then increase the temperature from 460℃ to 1150℃ at a rate of 3.7℃ / min, keep the temperature for 6h, and cool down to room temperature in the furnace, which is the high-temperature sintering treatment.

[0057] In step three, the preparation method of the dense inert coating slurry comprises the following main parameters: step 3.2: the silica sol, the aluminum sol and the yttrium sol are put into a blender, stirred at room temperature for 2.3 hours at a stirring speed of 308 r / min, to obtain a sol component; step 3.3: the nano-silicon dioxide, the nano-aluminum oxide, the nano-yttrium oxide and the nano-zirconium silicate are put into a V-type mixer, mixed at room temperature for 23 minutes at a mixing speed of 160 r / min, to obtain a nano-powder component; step 3.4: the nano-powder component is added into the blender to continue stirring with the sol component for 7 hours, to obtain the dense inert coating slurry.

[0058] In step four, the dense inert coating slurry is slowly injected into the dipping cavity until the liquid level of the dense inert coating slurry reaches a position 22 mm above the highest point of the core porous structure ceramic core.

[0059] In step five, the core porous structure ceramic core is dipped in the dense inert coating slurry under the segmented vacuum pressure by using the gradient pressure reduction mode, i.e. three-stage dipping: first-stage dipping, 0.08 MPa≤ vacuum pressure < 0.1 MPa, and the dipping time is 3 minutes; second-stage dipping, 0.05 MPa≤ vacuum pressure < 0.08 MPa, and the dipping time is 12 minutes; third-stage dipping, 0.02 MPa≤ vacuum pressure < 0.05 MPa, and the dipping time is 6 minutes.

[0060] In step six, the sintering treatment temperature is 780℃, and the calcination treatment time is 5 hours.

[0061] Example three: According to another preferred embodiment of the outer dense core porous structure high-relief ceramic core and the preparation method thereof, the material selection and proportion, the process flow and parameters, the technical principle and the beneficial effects are basically the same as those of example one, except that: The mass percentage of each substance in the core porous structure ceramic core is 48wt% of the ceramic powder component, 38wt% of the hollow glass bead component, 5wt% of the fiber component, 5wt% of the graphite and 4wt% of the starch, and the mass percentage of each substance in the dense inert coating is 72wt% of the sol component and 28wt% of the nano-powder component. In this embodiment, when the addition amount of the ceramic powder component is increased by 3wt%, the addition amount of the hollow glass bead component is correspondingly increased by 1.5wt%, which is ensured to be controlled within the range of 1.5-2wt%.

[0062] The mass percentage of each substance in the ceramic powder component is 52wt% of quartz glass powder, 26wt% of white corundum powder, and 22wt% of zirconium silicate powder. The quartz glass powder, the white corundum powder, and the zirconium silicate powder each include three grades of particle size, and the mass ratio of the particle size 30-40μm, the particle size 18-30μm, and the particle size 10-18μm is 2.8:1.8:1.

[0063] The mass percentage of each substance in the hollow glass microsphere component is 56wt% of silicon oxide hollow glass microspheres, 23wt% of aluminum oxide hollow glass microspheres, and 21wt% of zirconium silicate hollow glass microspheres. The silicon oxide hollow glass microspheres, the aluminum oxide hollow glass microspheres, and the zirconium silicate hollow glass microspheres each include three grades of particle size, and the mass ratio of the particle size 20-30μm, the particle size 10-20μm, and the particle size 0-10μm is 2.8:1.8:1.

[0064] The mass percentage of each substance in the fiber component is 62wt% of chopped carbon fiber and 38wt% of chopped aramid fiber. The diameter of the chopped carbon fiber and the chopped aramid fiber is controlled within the range of 2-8μm, and the aspect ratio is controlled within the range of 10-25:1. The particle size of the graphite is controlled within the range of 1-5μm.

[0065] The mass percentage of each substance in the sol component is 45wt% of silicon sol, 33wt% of aluminum sol, and 22wt% of yttrium sol. The mass percentage of each substance in the nano-powder component is 29wt% of nano-silicon dioxide, 23wt% of nano-aluminum oxide, 12wt% of nano-yttrium oxide, and 36wt% of nano-zirconium silicate. The particle size of each substance is controlled within the range of 10-30nm.

[0066] In step two, the preparation method of the core porous structure ceramic core comprises the following main parameters: step 2.2: put the quartz glass powder, white corundum powder and zirconium silicate powder into a V-type mixer, mix at room temperature for 26 min, and the mixing speed is 130 r / min, to prepare a ceramic powder component; step 2.3: put the hollow glass microspheres of silicon oxide, hollow glass microspheres of aluminum oxide and hollow glass microspheres of zirconium silicate into a V-type mixer, mix at room temperature for 26 min, and the mixing speed is 130 r / min, to prepare a hollow glass microsphere component; step 2.4: put 21% of the added amount of plasticizer into a stirrer, stir while heating, the stirring speed is 130 r / min, continue to stir for 26 min after the temperature is heated to 116℃; steps 2.5-2.8: keep the stirring temperature and stirring speed unchanged, add the ceramic powder component into the stirrer and continue to stir for 1.6 h, add the hollow glass microsphere component into the stirrer and continue to stir for 1.6 h, add the chopped carbon fiber and chopped aramid fiber into the stirrer and continue to stir for 2.6 h, add the graphite and starch into the stirrer and continue to stir for 4.2 h, to prepare a ceramic core slurry; step 2.9: use the ceramic core slurry to press the ceramic core blank, the pressing temperature is 116℃, the pressing pressure is 5 MPa, and the pressure holding time is 140 s, after low-temperature glue removal treatment and high-temperature sintering treatment, the core porous structure ceramic core is prepared.

[0067] The process system of the low-temperature glue removal treatment and the high-temperature sintering treatment is as follows: put the ceramic core blank into a sintering furnace, first increase the temperature from room temperature to 520℃ at a rate of 8℃ / min, keep the temperature for 13 h, that is, complete the low-temperature glue removal treatment; then increase the temperature from 520℃ to 1200℃ at a rate of 4.4℃ / min, keep the temperature for 5 h, and cool to room temperature with the furnace, that is, complete the high-temperature sintering treatment.

[0068] In step three, the preparation method of the densified inert coating slurry comprises the following main parameters: step 3.2: put the silica sol, aluminum sol and yttrium sol into a stirrer, stir at room temperature for 2.6 h, and the stirring speed is 265 r / min, to prepare a sol component; step 3.3: put the nano-silicon dioxide, nano-aluminum oxide, nano-yttrium oxide and nano-zirconium silicate into a V-type mixer, mix at room temperature for 26 min, and the mixing speed is 130 r / min, to prepare a nano-powder component; step 3.4: add the nano-powder component into the stirrer to continue stirring with the sol component for 8 h, to prepare a densified inert coating slurry.

[0069] In step four, slowly inject the densified inert coating slurry into the impregnation cavity until the liquid level of the densified inert coating slurry reaches a position 23 mm above the highest point of the core porous structure ceramic core.

[0070] In step five, the core porous structure ceramic core is impregnated with the inert coating slurry under the segmented vacuum pressure in a gradient pressure reduction mode, namely, in three stages: in the first stage, 0.08 MPa≤ vacuum pressure < 0.1 MPa, and the impregnation time is 4 min; in the second stage, 0.05 MPa≤ vacuum pressure < 0.08 MPa, and the impregnation time is 13 min; in the third stage, 0.02 MPa≤ vacuum pressure < 0.05 MPa, and the impregnation time is 7 min.

[0071] In step six, the sintering treatment temperature is 870 ℃, and the calcination treatment time is 4 h.

[0072] Example Four: According to another preferred embodiment of the outer dense core porous structure high-relief ceramic core and the preparation method thereof, the material selection and proportion, the process flow and parameters, the technical principle, and the beneficial effects are basically the same as those of example one, except that: The mass percentage of each substance in the core porous structure ceramic core is 51 wt% of the ceramic powder component, 40 wt% of the hollow glass bead component, 4 wt% of the fiber component, 3 wt% of the graphite, and 2 wt% of the starch, and the mass percentage of each substance in the dense inert coating is 75 wt% of the sol component and 25 wt% of the nano-powder component. In this embodiment, when the addition amount of the ceramic powder component is increased by 3 wt%, the addition amount of the hollow glass bead component is correspondingly increased by 2 wt%, and the increase is controlled within the range of 1.5-2 wt%.

[0073] The mass percentage of each substance in the ceramic powder component is 55 wt% of the quartz glass powder, 25 wt% of the white corundum powder, and 20 wt% of the zirconium silicate powder. The quartz glass powder, the white corundum powder, and the zirconium silicate powder all include three grades of particle sizes, and the mass ratio of the particle size 30-40 μm, the particle size 18-30 μm, and the particle size 10-18 μm is 3:2:1.

[0074] The mass percentage of each substance in the hollow glass bead component is 60 wt% of the silica hollow glass bead, 22 wt% of the alumina hollow glass bead, and 18 wt% of the zirconium silicate hollow glass bead. The silica hollow glass bead, the alumina hollow glass bead, and the zirconium silicate hollow glass bead all include three grades of particle sizes, and the mass ratio of the particle size 20-30 μm, the particle size 10-20 μm, and the particle size 0-10 μm is 3:2:1.

[0075] The mass percentage of each substance in the fiber component is 72wt% of chopped carbon fiber and 28wt% of chopped aramid fiber; the diameter of the chopped carbon fiber and the chopped aramid fiber is controlled in the range of 2-8μm, and the aspect ratio is controlled in the range of 10-25:1. The particle size of the graphite is controlled in the range of 1-5μm.

[0076] The mass percentage of each substance in the sol component is 47wt% of silica sol, 32wt% of aluminum sol and 21wt% of yttrium sol. The mass percentage of each substance in the nano-powder component is 31wt% of nano-silicon dioxide, 24wt% of nano-aluminum oxide, 11wt% of nano-yttrium oxide and 34wt% of nano-zirconium silicate, and the particle size of each substance is controlled in the range of 10-30nm.

[0077] In step two, the preparation method of the core porous structure ceramic core comprises the following main parameters: step 2.2: put quartz glass powder, white corundum powder and zirconium silicate powder into a V-type mixer, mix at room temperature for 30min, and the mixing speed is 100r / min, to prepare a ceramic powder component; step 2.3: put hollow glass microspheres of silicon oxide, hollow glass microspheres of aluminum oxide and hollow glass microspheres of zirconium silicate into a V-type mixer, mix at room temperature for 30min, and the mixing speed is 100r / min, to prepare a hollow glass microsphere component; step 2.4: put 25% of the added amount of plasticizer into a stirrer, stir while heating, the stirring speed is 100r / min, continue to stir for 30min after the temperature is heated to 130℃; steps 2.5-2.8: keep the stirring temperature and stirring speed unchanged, add the ceramic powder component into the stirrer and continue to stir for 2h, add the hollow glass microsphere component into the stirrer and continue to stir for 2h, add the chopped carbon fiber and the chopped aramid fiber into the stirrer and continue to stir for 3h, add the graphite and the starch into the stirrer and continue to stir for 5h, to prepare a ceramic core slurry; step 2.9: use the ceramic core slurry to press a ceramic core blank, the pressing temperature is 130℃, the pressing pressure is 7MPa, and the pressure holding time is 120s, after low-temperature glue removal treatment and high-temperature sintering treatment, a core porous structure ceramic core is prepared.

[0078] The process system of the low-temperature glue removal treatment and the high-temperature sintering treatment is as follows: put the ceramic core blank into a sintering furnace, first increase the temperature from room temperature to 600℃ at a rate of 10℃ / min, keep the temperature for 10h, which is the low-temperature glue removal treatment; then increase the temperature from 600℃ to 1250℃ at a rate of 5℃ / min, keep the temperature for 4h, and cool down to room temperature with the furnace, which is the high-temperature sintering treatment.

[0079] In step three, the preparation method of the dense inert coating slurry comprises the following main parameters: step 3.2: the silica sol, aluminum sol, yttrium sol are put into a blender, stirred at room temperature for 3h, the stirring speed is 220r / min, and the sol component is prepared; step 3.3: the nano-silicon dioxide, nano-aluminum oxide, nano-yttrium oxide, nano-zirconium silicate are put into a V-type mixer, mixed at room temperature for 30min, the mixing speed is 100r / min, and the nano-powder component is prepared; step 3.4: the nano-powder component is added into the blender to continue stirring with the sol component for 10h, and the dense inert coating slurry is prepared.

[0080] In step four, the dense inert coating slurry is slowly injected into the dipping cavity until the liquid level of the dense inert coating slurry reaches a position 25mm above the highest point of the core porous structure ceramic core.

[0081] In step five, the core porous structure ceramic core is dipped in the dense inert coating slurry under the segmented vacuum pressure by using the gradient pressure reduction method, that is, the dipping is divided into three stages: in the first stage of dipping, the vacuum pressure is 0.08MPa≤vacuum pressure<0.1MPa, and the dipping time is 5min; in the second stage of dipping, the vacuum pressure is 0.05MPa≤vacuum pressure<0.08MPa, and the dipping time is 15min; in the third stage of dipping, the vacuum pressure is 0.02MPa≤vacuum pressure<0.05MPa, and the dipping time is 8min.

[0082] In step six, the sintering treatment temperature is 950℃, and the calcination treatment time is 3h.

[0083] Comparative Example One: A dense ceramic core is prepared by using a traditional formula, and quartz glass powder 60wt%, white corundum powder 25wt%, zirconium silicate powder 15wt% are weighed according to the mass percentage, 20wt% of the total mass of the powder is added as a plasticizer, after mixing and pressing, the whole dense structure ceramic core is obtained by calcining at 1200℃ for 5h. Comparative Example Two: The core porous structure ceramic core is prepared by using the material formula, process flow and process parameters of the embodiment one, but without the dipping treatment of the dense inert coating.

[0084] The ceramic cores prepared by using the above four embodiments and two comparative examples are further used for the casting of a complex inner cavity structure high Hf alloy blade in a certain type of aero-engine, and the quality of the castings is detected, and the detection results are shown in Table 1.

[0085] Table 1: Detection results of blade castings prepared by using different ceramic cores From the above detection results, it can be seen that the ceramic cores prepared in the four examples have high yielding property, low surface activity and excellent core removal performance, the further casting of the blade using the ceramic cores of the four examples can effectively solve the problems of the hot crack defects and recrystallization in the blade inner cavity, the thickness of the reaction layer of the interface can be reduced to below 2 μm, and there is no residual core in the blade inner cavity after core removal, and the qualified rate of the casting is as high as 90% or more.

[0086] The ceramic powder components, hollow glass microsphere components, fiber components, graphite, starch, sol components, nano-powder components, plasticizers and other raw materials used in the above examples are purchased from Aladdin Reagent Co., Ltd. and Sinopharm Chemical Reagent Co., Ltd.

[0087] Special note: The technical solutions of the present application involve many parameters, and the synergistic effect between each parameter needs to be considered in order to obtain the beneficial effects and significant progress of the present application. Moreover, the value range of each parameter in the technical solution is obtained through a large number of tests, and for each parameter and the mutual combination of each parameter, the inventors have recorded a large amount of test data, and due to the limited space, the specific test data is not disclosed here.

[0088] It is not difficult for those skilled in the art to understand that the present application includes any combination of the above-mentioned invention content and specific embodiment parts of the present application specification and the parts shown in the drawings, and due to the limited space and in order to make the specification concise, each scheme formed by these combinations is not described one by one. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A high-yield ceramic core with a dense surface and a porous core, characterized in that: The high-yield ceramic core is composed of a core porous structure ceramic core and a densified inert coating on its outer surface. The mass percentage of each substance in the core porous structure ceramic core is 42-51wt% of the ceramic powder component, 35-40wt% of the hollow glass microbead component, 4-9wt% of the fiber component, 3-7wt% of the graphite, and 2-8wt% of the starch. The mass percentage of each substance in the densified inert coating is 67-75wt% of the sol component and 25-33wt% of the nanopowder component.

2. The high-yield ceramic core with a dense surface and porous core structure according to claim 1, characterized in that: The addition amount of the hollow glass microsphere component increases with the increase in the addition amount of the ceramic powder component. Within the mass percentage range of the hollow glass microsphere component and the ceramic powder component, when the addition amount of the ceramic powder component increases by 3wt%, the addition amount of the hollow glass microsphere component correspondingly increases by 1.5-2wt%.

3. The high-yield ceramic core with a dense surface and porous core structure according to claim 2, characterized in that: The mass percentage of each substance in the ceramic powder component is 48-55wt% of quartz glass powder, 24-28wt% of white corundum powder, and 20-24wt% of zirconium silicate powder; The quartz glass powder, the white corundum powder, and the zirconium silicate powder all include three particle sizes, namely, 30-40 μm, 18-30 μm, and 10-18 μm. The mass ratios of the particle sizes of 30-40 μm, 18-30 μm, and 10-18 μm are all 2-3:1-2:

1.

4. The high-yield ceramic core with a dense outer surface and a porous core according to claim 3, characterized in that: The mass percentage of each substance in the hollow glass microsphere component is 50-60wt% of silicon oxide hollow glass microspheres, 21-27wt% of aluminum oxide hollow glass microspheres, and 18-24wt% of zirconium silicate hollow glass microspheres; The silicon oxide hollow glass microspheres, the aluminum oxide hollow glass microspheres, and the zirconium silicate hollow glass microspheres all include three particle sizes, namely, a particle size of 20-30 μm, a particle size of 10-20 μm, and a particle size of 0-10 μm. The mass ratios of the particle size of 20-30 μm, the particle size of 10-20 μm, and the particle size of 0-10 μm are all 2-3:1-2:

1.

5. The high-yield ceramic core with a dense outer surface and a porous core structure according to claim 4, characterized in that: The mass percentage of each substance in the fiber component is 42-72wt% of short carbon fiber and 28-58wt% of short aramid fiber; the diameters of the short carbon fiber and the short aramid fiber are both controlled within the range of 2-8μm, and the aspect ratio is both controlled within the range of 10-25:

1.

6. The high-yield ceramic core with a dense outer surface and a porous core structure according to claim 5, characterized in that: The mass percentage of each substance in the sol component is 42-47wt% of silica sol, 30-35wt% of aluminum sol, and 21-25wt% of yttrium sol; The mass percentage of each substance in the nano-powder component is 24-31wt% of nano-silicon dioxide, 17-24wt% of nano-aluminum oxide, 10-17wt% of nano-yttrium oxide, and 34-41wt% of nano-zirconium silicate; the particle sizes of the nano-silicon dioxide, the nano-aluminum oxide, the nano-yttrium oxide, and the nano-zirconium silicate are all controlled within the range of 10-30nm.

7. A method for preparing a highly yielding ceramic core having a dense surface and a porous core according to any one of claims 1 to 6, characterized in that: The preparation method comprises the following steps in chronological order: Step 1: Weigh all raw materials according to the designed material ratio; Step 2: Prepare a ceramic core with a porous core structure according to the designed process and parameters; Step 3: Prepare a densified inert coating slurry according to the designed process and parameters; Step 4: Use a positioning fixture to suspend the core porous structure ceramic core in the impregnation chamber of the vacuum impregnation equipment, so that the core porous structure ceramic core maintains an appropriate gap with the inner wall of the impregnation chamber, and then slowly inject the densified inert coating slurry into the impregnation chamber until the densified inert coating slurry completely immerses the core porous structure ceramic core; Step 5: Starting the vacuum system of the vacuum impregnation equipment, using a gradient pressure reduction method to impregnate the core porous structure ceramic core with the densified inert coating slurry under segmented vacuum pressure, so that the densified inert coating slurry fully penetrates the pores on the outer surface of the core porous structure ceramic core, forming a densified inert coating on the outer surface; Step 6: Place the core porous structure ceramic core with the densified inert coating in a heat treatment furnace for sintering, so that the densified inert coating is tightly bonded to the outer surface of the core porous structure ceramic core, thereby obtaining a high-yield ceramic core with a dense outer surface and a porous core structure.

8. The method for preparing a highly yielding ceramic core having a dense outer surface and a porous core according to claim 7, characterized in that: In step 2, the method for preparing the ceramic core with a porous core structure includes the following steps in order: Step 2.1: Weigh all raw materials according to the designed material ratio; Step 2.2: Place all the quartz glass powder, white corundum powder, and zirconium silicate powder of various particle sizes into a V-type mixer and mix them at room temperature for 20-30 minutes at a mixing speed of 100-200 r / min to uniformly mix the materials to obtain a ceramic powder component; Step 2.3: Place all hollow silica glass microspheres, hollow alumina glass microspheres, and hollow zirconium silicate glass microspheres of various particle sizes into a V-type mixer and mix them at room temperature for 20-30 minutes at a mixing speed of 100-200 rpm to uniformly mix the materials to obtain hollow glass microsphere components; Step 2.4: Place the plasticizer in a blender and heat while stirring at a speed of 100-200 rpm. After the temperature reaches 90-130°C, continue stirring for 20-30 minutes to completely melt the plasticizer. The amount of plasticizer added is 15-25% of the mass of the porous ceramic core. The plasticizer is composed of 93 wt% paraffin wax, 5 wt% beeswax, and 2 wt% polyethylene. Step 2.5: Keeping the stirring temperature and speed constant, add the ceramic powder components into the blender and continue stirring for 1-2 hours to allow the materials to blend together. Step 2.6: Keeping the stirring temperature and stirring speed constant, add the hollow glass microsphere component into the blender and continue stirring for 1-2 hours to allow the substances to blend together; Step 2.7: Keeping the stirring temperature and stirring speed constant, add the chopped carbon fiber and chopped aramid fiber into the blender and continue stirring for 2-3 hours to evenly disperse the fiber components; Step 2.8: Keeping the stirring temperature and speed constant, add graphite and starch into the blender and continue stirring for 3-5 hours to mix the materials evenly to prepare the ceramic core slurry; Step 2.9: Using the prepared ceramic core slurry, a ceramic core blank is pressed at a temperature of 90-130°C, a pressure of 3-7 MPa, and a holding time of 120-180 seconds. The ceramic core blank is then placed in a roasting furnace for low-temperature debinding treatment and high-temperature sintering to decompose and volatilize organic matter in the ceramic core blank, forming a porous structure, thereby producing a ceramic core with a porous core structure. The process system of low-temperature debinding treatment and high-temperature sintering treatment is as follows: the ceramic core blank is placed in a roasting furnace, first heated from room temperature to 400-600℃ at a heating rate of 5-10℃ / min, and kept warm for 10-20h to complete the low-temperature debinding treatment; then heated from 400-600℃ to 1100-1250℃ at a heating rate of 3-5℃ / min, kept warm for 4-8h, and cooled to room temperature with the furnace to complete the high-temperature sintering treatment; during the entire low-temperature debinding treatment and high-temperature sintering process, no protective atmosphere is required.

9. The method for preparing a highly yielding ceramic core having a dense outer surface and a porous core according to claim 8, characterized in that: In step 3, the method for preparing the densified inert coating slurry comprises the following steps in order: Step 3.1: Weigh all raw materials according to the designed material ratio; Step 3.2: Place the silica sol, aluminum sol, and yttrium sol into a blender and stir at room temperature for 2-3 hours at a stirring speed of 220-350 rpm to uniformly disperse and fuse the substances to obtain a sol component. Step 3.3: Place nano-silica, nano-alumina, nano-yttrium oxide, and nano-zirconium silicate into a V-type mixer and mix them at room temperature for 20-30 minutes at a mixing speed of 100-200 r / min to uniformly mix the materials to obtain a nano-powder component; Step 3.4: Add the prepared nanopowder component into a blender and continue to stir with the sol component for 6-10 hours to allow the various substances to blend with each other, thereby obtaining a densified inert coating slurry.

10. The method for preparing a highly yielding ceramic core having a dense outer surface and a porous inner structure according to claim 9, characterized in that: In step 4, the densified inert coating slurry is slowly injected into the impregnation chamber until the liquid level of the densified inert coating slurry reaches a position 20-25 mm above the highest point of the core porous structure ceramic core; In step five, a gradient pressure reduction method is used to impregnate the core porous structure ceramic core with a densified inert coating slurry under segmented vacuum pressure, that is, the impregnation is divided into three stages: the first stage impregnation, 0.08MPa≤vacuum pressure<0.1MPa, and the impregnation time is 2-5min; the second stage impregnation, 0.05MPa≤vacuum pressure<0.08MPa, and the impregnation time is 10-15min; the third stage impregnation, 0.02MPa≤vacuum pressure<0.05MPa, and the impregnation time is 5-8min; in step six, the sintering treatment temperature is 700-950℃ and the roasting treatment time is 3-6h.

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