Alumina-based ceramic core and its preparation and removal method

Abstract

The application relates to an alumina-based ceramic core and a preparation and removal method thereof, and relates to the technical field of engine blade casting. The alumina-based ceramic core comprises the following raw materials: solid powder and plasticizer; the mass ratio of the solid powder to the plasticizer is 1:0.1-0.8; the solid powder comprises the following raw materials with mass percentage: 0.5-10% composite mineralizer powder, 87%-99.5% alumina powder and 0.1%-3% fiber material. The alumina-based ceramic core is improved in a chemical removal rate without reducing the use strength and high-temperature strength of the alumina-based ceramic core, and the problem of alumina-based ceramic core removal difficulty which has long plagued the engine blade casting field is solved from the source.

Description

Technical Field

[0001] This invention relates to the field of engine blade casting technology, specifically to an alumina-based ceramic core and its preparation and removal methods. Background Technology

[0002] Hollow blades for aero engines and gas turbines are precision components that withstand high temperatures and pressures on the turbine rotor at the rear end of the sintering chamber. They are commonly manufactured using a master alloy melting and casting process. The mold material for the hollow portion of the hollow blade is called a ceramic core. This is a pre-formed part that needs to be shaped and sintered before casting. It needs to be pre-filled into a ceramic shell to provide shape stability and high-temperature mechanical properties during casting. After casting, the ceramic core is chemically removed to form the hollow blade. The dimensional stability and mechanical properties of the ceramic core are key auxiliary materials that determine whether the hollow cavity of the blade can be successfully generated and provide a continuous airflow channel. It is one of the high-end and key products in precision casting ceramic products.

[0003] Currently, commonly used ceramic cores mainly include aluminum-based cores with alumina as the main component and silicon-based cores with silicon oxide as the matrix. Other core materials include those with calcium oxide and magnesium oxide as the matrix. Cores require dimensional stability and excellent mechanical properties under high-temperature casting conditions to facilitate chemical removal. Silicon-based cores have the advantage of easy removal, but their high-temperature mechanical properties are unstable and cannot withstand long-term high-temperature testing. The process maturity of calcium oxide and magnesium oxide-based cores is not yet high, making large-scale production difficult. Aluminum-based ceramic cores have advantages such as good high-temperature stability, high strength, and low creep, and are currently the main source of cavities for single-crystal and oriented blades. However, their main problem is that their chemical properties are too stable, resulting in a slow removal rate in chemical removal solutions. This has a significant impact on the continuity of engine production, quality assurance rate, and blade yield, and is a key technical problem that must be faced and urgently needs to be solved in the development and use of aluminum-based cores.

[0004] Currently, the main methods to address these issues are to extend the chemical core removal time without restriction and to increase the core removal temperature and pressure. However, prolonged boiling of alloy hollow blades in the core removal liquid can lead to grain boundary defects, significantly increasing the probability of brittle fracture and having a fatal impact on engine life and flight safety. Research has also been conducted on increasing the porosity of ceramics, adding soluble mineralizers, and lowering the sintering temperature to reduce the core removal process cycle and the probability of blade surface defects, thereby improving the removal efficiency of aluminum-based ceramic cores. Some progress has been made, but overall, there is still no effective solution. Relatively speaking, there are few publicly disclosed technologies for aluminum-based ceramic cores. For example, patent 201410224781.2 discloses a method for preparing such aluminum-based cores using zirconium silicate, magnesium oxide, titanium oxide, or any mixture thereof as mineralizers, and zirconium oxide or yttrium oxide-coated corundum powder prepared by liquid-phase synthesis as the main raw material. However, the synthesis process of this technology is relatively complex.

[0005] To address the problem of difficult core removal from aluminum-based ceramic cores, this invention proposes an alumina-based ceramic core and its preparation and removal methods. Summary of the Invention

[0006] To address the aforementioned technical problems, the present invention aims to provide an alumina-based ceramic core and its preparation and removal method. The present invention effectively solves the problems of high probability of surface defects, complex synthesis process, and difficulty in core removal in the prior art.

[0007] The technical solution of the present invention to solve the above-mentioned technical problems is as follows:

[0008] An alumina-based ceramic core, the ceramic core comprising the following raw materials: solid powder and plasticizer; the mass ratio of the solid powder to the plasticizer is 1:0.1-0.8;

[0009] The solid powder comprises the following raw materials by mass percentage: 0.5-10% composite mineralizer powder, 87%-99.5% alumina powder, and 0.1%-3% fiber material.

[0010] The beneficial effects of this invention are as follows: Firstly, the core formulation of this invention using composite oxides as mineralizers has the advantage of forming solid solutions or compounds, which greatly promotes the sintering rate; secondly, the production process of the ceramic core of this invention can be adjusted according to the different casting target alloys, and the formulation and preparation scheme can be adjusted accordingly; finally, compared with the removal rate of cores with single mineralizers, the core removal time of this invention is shortened by more than half (i.e., the dissolution rate is increased by more than 1 time).

[0011] Furthermore, the composite mineralizer powder is a spherical powder without sharp edges, and the purity of the composite mineralizer powder is above 99.5%; wherein the particle size distribution of the powder exhibits a unimodal normal distribution.

[0012] Furthermore, the particle size of the composite mineralizer powder is 0.1-5 μm, and the volume of the powder smaller than 2.0 μm in the composite mineralizer powder is 40%-80%.

[0013] The beneficial effects of adopting the above-mentioned further scheme are: the mineralizer of this application must contain ultrafine powder to promote the sintering of the material, while forming new phases that combine with each other to form a skeleton and improve the performance of the ceramic core.

[0014] Furthermore, the composite mineralizer comprises two or more submicron-sized oxides, and at least one of the submicron-sized oxides contains substances similar to Al. 3+ Cations with different valence states.

[0015] The beneficial effects of adopting the above-mentioned further scheme are as follows: The mineralizer used in this invention is a composite oxide. Through lattice doping and solid solution reaction between metal ions of different valence states, the reaction rate and ion migration rate of alumina raw materials and mineralizer at the grain boundary are improved. Then, fiber materials are added to improve the high-temperature strength of ceramics, reduce the self-weight deflection at high temperature, and reduce the reaction energy barrier between ceramic grain boundaries and core removal liquid, thereby accelerating the dissolution reaction rate in the ceramic core removal process and achieving the purpose of improving the ceramic core removal rate from the source.

[0016] Furthermore, the composite mineralizer powder includes at least two of the following: CaO, SrO, BaO, Cr2O3, La2O3, Ga2O3, Co3O4, CeO2, SiO2, V2O5, and WO3, and includes CaO, SrO, BaO, Co3O4, and CeO. 2、 At least one of SiO2, V2O5, and WO3. The amount of any single oxide added shall not exceed 5% of the total solid powder mass.

[0017] The beneficial effects of adopting the above-mentioned further scheme are: the composite mineralizer powder selected in this invention is a composite oxide, and all of them are metal cation oxides. The selection principle is that at least one ion in the composite oxide reacts with Al. 3+ The different valence states of the oxides and their tendency to form compounds, limited miscibility, or unlimited solid solutions with Al2O3 greatly promote the sintering rate. When selecting the composite mineralizer powder of the present invention, it includes, but is not limited to, the above-mentioned divalent alkaline earth metal ion oxides such as CaO, SrO, and BaO, the trivalent metal cation oxides such as Cr2O3, La2O3, and Ga2O3, and two or more composite oxide powders among other metal oxides with different valence states such as Co3O4, CeO2, SiO2, V2O5, and WO3. As long as the selection principle is met, any oxide can be selected. The selection of different oxides should be purposefully made according to the strength of the core and the type of high-temperature alloy.

[0018] Furthermore, the fiber material has a length of 0.5-10 μm and an aspect ratio of 5-10:1.

[0019] The beneficial effects of adopting the above-mentioned further solution are that the added fibers can provide significant reinforcement to the ceramic core and can prevent the core from cracking during the firing process.

[0020] Furthermore, the fiber material is at least one of SiO2, Al2O3, La2O3, ZrO2, WO3, and mullite.

[0021] The beneficial effects of adopting the above-mentioned further solution are: by using the fiber material selected in this invention to add to the preparation of the ceramic core, the high-temperature strength of the ceramic core can be improved and the self-weight deflection at high temperature can be reduced; at the same time, the reaction energy barrier between the ceramic grain boundary and the core removal liquid is reduced, thereby accelerating the dissolution reaction rate in the ceramic core removal process.

[0022] A second objective of this invention is to provide a method for preparing an alumina-based ceramic core, characterized in that the method comprises the following steps:

[0023] (1) Grind the composite mineralizer and mix it evenly to obtain the finely ground composite mineralizer powder for later use; heat the plasticizer to melt it to obtain a mixed solution, then pour the finely ground composite mineralizer powder into the mixed solution, and add fiber material and mix evenly to obtain a mixture;

[0024] (2) After adding alumina powder to the mixture and stirring for 12-24 hours, the mixture is injected into a core mold under a pressure of 3-5 MPa. After cooling, the core is removed and sintered to obtain an alumina-based ceramic core.

[0025] Furthermore, the plasticizer includes the following raw materials: oleic acid, paraffin wax, and beeswax.

[0026] The beneficial effect of adopting the above-mentioned further scheme is that adding oleic acid, paraffin wax, and beeswax increases the plasticity of the ceramic core.

[0027] Furthermore, the sintering temperature is 1300-1380℃, and the holding time is 6-12h.

[0028] The third objective of this invention is to provide a method for removing alumina-based ceramic cores, the method comprising the following steps: immersing the alloy blades and the alumina-based ceramic core together in a core-removing solution and boiling for 12-72 hours.

[0029] The beneficial effects of this invention are: without reducing the strength and high-temperature strength of the aluminum-based ceramic core, this invention improves the chemical removal rate of the aluminum-based ceramic core, thus solving the problem of difficult removal of aluminum-based ceramic cores that has long plagued the field of engine blade casting.

[0030] Furthermore, the core-removing liquid comprises the following raw materials: saturated NaOH solution and KOH solution; the mass ratio of NaOH to KOH in the core-removing liquid is 5-10:1. Detailed Implementation

[0031] The principles and features of this invention are described below. The examples given are for illustrative purposes only and are not intended to limit the scope of the invention. Where specific techniques or conditions are not specified in the embodiments, they should be performed according to the techniques or conditions described in the literature in this field, or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased through legitimate channels.

[0032] Example 1: Preparation of alumina-based ceramic core

[0033] (1) Weigh out 4 kg of CaO, SiO2, WO3 nanofibers with a length of 2-5 μm and alumina powder as solid powder (the mass percentages of CaO, SiO2, WO3 nanofibers and alumina powder in the solid powder are 1%, 1%, 0.5% and 97.5% respectively); first mix CaO and SiO2 as a composite mineralizer, grind them finely and mix them evenly to obtain finely ground composite mineralizer powder for later use;

[0034] Weigh out 500g of paraffin wax, beeswax, and oleic acid in a mass ratio of 91:7:2 and mix them together. Heat and melt the mixture to obtain a mixed solution. Pour finely ground composite mineralizer powder into the mixed solution, and then add WO3 nanofiber material with a fiber length of 2-5μm and an aspect ratio of 5-10:1. Mix evenly to obtain a mixture.

[0035] (2) After adding alumina powder to the mixture and stirring for 24 hours, a slurry is obtained. The slurry is injected into the core mold at a pressure of 3 MPa on a die casting machine. The core is sintered at a final firing temperature of 1330℃ and held for 6 hours. After cooling, the core is removed to produce an alumina-based ceramic core.

[0036] Example 2: Preparation of alumina-based ceramic core

[0037] (1) Weigh out 4 kg of SrO, Cr2O3, mullite nanofibers with a length of 2-5 μm, and alumina powder as solid powder (the mass percentages of SrO, Cr2O3, mullite nanofibers, and alumina powder in the solid powder are 1%, 0.5%, 0.5%, and 98%, respectively); first mix SrO and Cr2O3 as a composite mineralizer, grind them finely and mix them evenly to obtain finely ground composite mineralizer powder for later use;

[0038] Weigh out 500g of paraffin wax, beeswax, and oleic acid in a mass ratio of 91:7:2, heat and melt them to obtain a mixed solution, pour finely ground composite mineralizer powder into the mixed solution, and then add mullite nanofiber material with a fiber length of 2-5μm and an aspect ratio of 5-10:1 and mix evenly to obtain a mixture.

[0039] (2) After adding alumina powder to the mixture and stirring for 24 hours, a slurry is obtained. The slurry is injected into the core mold at a pressure of 3 MPa on a die casting machine. The core is sintered at a final firing temperature of 1320℃ and held for 8 hours. After cooling, the core is removed to produce an alumina-based ceramic core.

[0040] Example 3: Preparation of alumina-based ceramic core

[0041] (1) Weigh out 4 kg of CeO2, WO3, SiO2 glass fiber with a length of 2-5 μm, and alumina powder as solid powder (the mass percentages of CeO2, WO3, SiO2 glass fiber, and alumina powder in the solid powder are 1%, 2%, 0.5%, and 96.5%, respectively); first mix CeO2 and WO3 as a composite mineralizer, grind them finely and mix them evenly to obtain finely ground composite mineralizer powder for later use;

[0042] Weigh out 500g of paraffin wax, beeswax, and oleic acid in a mass ratio of 91:7:2 and mix them. Heat and melt the mixture to obtain a mixed solution. Pour finely ground composite mineralizer powder into the mixed solution and add SiO2 glass fiber material with a fiber length of 2-5μm and an aspect ratio of 5-10:1. Mix evenly to obtain a mixture.

[0043] (2) After adding alumina powder to the mixture and stirring for 24 hours, a slurry is obtained. The slurry is injected into the core mold at a pressure of 5 MPa on a die casting machine. The core is sintered at a final firing temperature of 1380℃ and held for 8 hours. After cooling, the core is removed to produce an alumina-based ceramic core.

[0044] Example 4: Preparation of alumina-based ceramic core

[0045] (1) Weigh out 4 kg of CeO2, Cr2O3, SiO2 glass fiber with a length of 2-5 μm, and alumina powder as solid powder (the mass percentages of Cr2O3, Cr2O3, SiO2 glass fiber, and alumina powder in the solid powder are 1%, 1%, 0.5%, and 97.5%, respectively); first mix CeO2 and Cr2O3 as a composite mineralizer, grind them finely and mix them evenly to obtain finely ground composite mineralizer powder for later use;

[0046] Weigh out 500g of paraffin wax, beeswax, and oleic acid in a mass ratio of 91:7:2 and mix them. Heat and melt the mixture to obtain a mixed solution. Pour finely ground composite mineralizer powder into the mixed solution, and then add SiO2 glass fiber material with a fiber length of 2-5μm and an aspect ratio of 5-10:1 and mix evenly to obtain a mixture.

[0047] (2) After adding alumina powder to the mixture and stirring for 18 hours, a slurry is obtained. The slurry is injected into the core mold at a pressure of 4 MPa on a die casting machine. The core is sintered at a final firing temperature of 1350℃ and held for 8 hours. After cooling, the core is removed to produce an alumina-based ceramic core.

[0048] Example 5: Preparation of alumina-based ceramic core

[0049] (1) Weigh out 4 kg of BaO, Ga2O3, La2O3, Al2O3 nanofibers with a length of 2-5 μm, and alumina powder as solid powder (the mass percentages of BaO, Ga2O3, La2O3, Al2O3 nanofibers, and alumina powder in the solid powder are 0.5%, 0.5%, 0.5%, 0.5%, and 98%, respectively). First, mix BaO, Ga2O3, and La2O3 as a composite mineralizer, grind them finely, and mix them evenly to obtain a finely ground composite mineralizer powder for later use.

[0050] Weigh out 500g of paraffin wax, beeswax, and oleic acid in a mass ratio of 91:7:2 and mix them together. Heat and melt the mixture to obtain a mixed solution. Pour finely ground composite mineralizer powder into the mixed solution, and then add Al2O3 nanofiber material with a fiber length of 2-5μm and an aspect ratio of 5-10:1. Mix evenly to obtain a mixture.

[0051] (2) After adding alumina powder to the mixture and stirring for 24 hours, a slurry is obtained. The slurry is injected into the core mold at a pressure of 3 MPa on a die casting machine. The core is sintered at a final firing temperature of 1350℃ and held for 12 hours. After cooling, the core is removed to produce an alumina-based ceramic core.

[0052] Example 6: Preparation of alumina-based ceramic core

[0053] (1) Weigh out 4 kg of La2O3, CeO2, CaO, ZrO2 nanofibers with a length of 2-5 μm, and alumina powder as solid powder (the mass percentages of La2O3, CeO2, CaO, ZrO2 nanofibers, and alumina powder in the solid powder are 0.5%, 0.5%, 0.5%, 0.5%, and 98%, respectively). First, mix La2O3, CeO2, and CaO as a composite mineralizer, grind them finely, and mix them evenly to obtain a finely ground composite mineralizer powder for later use.

[0054] Weigh out 500g of paraffin wax, beeswax, and oleic acid in a mass ratio of 91:7:2 and mix them. Heat and melt the mixture to obtain a mixed solution. Pour finely ground composite mineralizer powder into the mixed solution and add ZrO2 nanofiber material with a fiber length of 2-5μm and an aspect ratio of 5-10:1. Mix evenly to obtain a mixture.

[0055] (2) Add alumina powder to the mixture and stir for 24 hours to obtain a slurry. Inject the slurry into the core mold at a pressure of 5 MPa on a die casting machine. Sinter the core at a final firing temperature of 1300℃ and hold for 12 hours. After cooling, remove the core to make an alumina-based ceramic core.

[0056] Comparative Example 1: Preparation of Alumina-based Ceramic Cores

[0057] The only difference between this comparative example and Example 1 is the composition of the solid powder in step (1). All other raw materials and steps are the same as in Example 1. The specific step (1) is as follows:

[0058] (1) Weigh 4 kg of SiO2, WO3 nanofibers with a length of 2-5 μm and alumina powder as solid powder (the mass percentages of SiO2, WO3 nanofibers and alumina powder in the solid powder are 2%, 0.5% and 97.5% respectively); grind SiO2 as a composite mineralizer and mix it evenly to obtain a finely ground composite mineralizer powder for later use.

[0059] Weigh out 500g of paraffin wax, beeswax, and oleic acid in a mass ratio of 91:7:2 and mix them. Heat and melt the mixture to obtain a mixed solution. Pour finely ground composite mineralizer powder into the mixed solution and add WO3 nanofiber material with a fiber length of 2-5μm and an aspect ratio of 5-10:1. Mix evenly to obtain a mixture.

[0060] Comparative Example 2: Preparation of Alumina-based Ceramic Cores

[0061] The only difference between this comparative example and Example 2 is the composition of the solid powder in step (1). All other raw materials and steps are the same as in Example 2. The specific step (1) is as follows:

[0062] (1) Weigh 4 kg of Cr2O3, mullite nanofibers with a length of 2-5 μm, and alumina powder as solid powder (the mass percentages of Cr2O3, mullite nanofibers, and alumina powder in the solid powder are 1.5%, 0.5%, and 98%, respectively); first grind Cr2O3 as a composite mineralizer and mix it evenly to obtain a finely ground composite mineralizer powder for later use.

[0063] Weigh out 500g of paraffin wax, beeswax, and oleic acid in a mass ratio of 91:7:2 and mix them. Heat and melt the mixture to obtain a mixed solution. Pour finely ground composite mineralizer powder into the mixed solution, and then add mullite nanofiber material with a fiber length of 2-5μm and an aspect ratio of 5-10:1. Mix evenly to obtain a mixture.

[0064] Comparative Example 3: Preparation of Alumina-based Ceramic Cores

[0065] The only difference between this comparative example and Example 3 is the composition of the solid powder in step (1). All other raw materials and steps are the same as in Example 3. The specific step (1) is as follows:

[0066] (1) Weigh 4 kg of WO3, SiO2 glass fiber with a length of 2-5 μm and alumina powder as solid powder (the mass percentages of WO3, SiO2 glass fiber and alumina powder in the solid powder are 2%, 0.5% and 97.5% respectively); first grind WO3 as a composite mineralizer and mix it evenly to obtain a finely ground composite mineralizer powder for later use.

[0067] Weigh out 500g of paraffin wax, beeswax, and oleic acid in a mass ratio of 91:7:2 and mix them. Heat and melt the mixture to obtain a mixed solution. Pour finely ground composite mineralizer powder into the mixed solution and add SiO2 glass fiber material with a fiber length of 2-5μm and an aspect ratio of 5-10:1. Mix evenly to obtain a mixture.

[0068] Comparative Example 4: Preparation of Alumina-based Ceramic Cores

[0069] The only difference between this comparative example and Example 4 is the composition of the solid powder in step (1). All other raw materials and steps are the same as in Example 4. The specific step (1) is as follows:

[0070] (1) Weigh 4 kg of Cr2O3, SiO2 glass fiber with a length of 2-5 μm, and alumina powder as solid powder (the mass percentages of Cr2O3, SiO2 glass fiber, and alumina powder in the solid powder are 1%, 0.5%, and 98.5%, respectively); first grind Cr2O3 as a composite mineralizer and mix it evenly to obtain a finely ground composite mineralizer powder for later use.

[0071] Weigh out 500g of paraffin wax, beeswax, and oleic acid in a mass ratio of 91:7:2 and mix them. Heat and melt the mixture to obtain a mixed solution. Pour finely ground composite mineralizer powder into the mixed solution, and then add SiO2 glass fiber material with a fiber length of 2-5μm and an aspect ratio of 5-10:1. Mix evenly to obtain a mixture.

[0072] Comparative Example 5: Preparation of Alumina-based Ceramic Cores

[0073] The only difference between this comparative example and Example 5 is the composition of the solid powder in step (1). All other raw materials and steps are the same as in Example 5. The specific step (1) is as follows:

[0074] (1) Weigh 4 kg of Ga2O3, Al2O3 nanofibers with a length of 2-5 μm, and alumina powder as solid powder (the mass percentages of Ga2O3, Al2O3 nanofibers, and alumina powder in the solid powder are 2%, 0.5%, and 97.5%, respectively); first, grind Ga2O3 as a composite mineralizer and mix it evenly to obtain a finely ground composite mineralizer powder for later use;

[0075] Weigh out 500g of paraffin wax, beeswax, and oleic acid in a mass ratio of 91:7:2 and mix them. Heat and melt the mixture to obtain a mixed solution. Pour finely ground composite mineralizer powder into the mixed solution, and then add Al2O3 nanofiber material with a fiber length of 2-5μm and an aspect ratio of 5-10:1. Mix evenly to obtain a mixture.

[0076] Comparative Example 6: Preparation of Alumina-based Ceramic Cores

[0077] The only difference between this comparative example and Example 6 is the composition of the solid powder in step (1). All other raw materials and steps are the same as in Example 6. The specific step (1) is as follows:

[0078] (1) Weigh 4 kg of CeO2, ZrO2 nanofibers with a length of 2-5 μm, and alumina powder as solid powder (the mass percentages of CeO2, ZrO2 nanofibers, and alumina powder in the solid powder are 1%, 0.5%, and 98.5%, respectively); first, grind CeO2 as a composite mineralizer and mix it evenly to obtain a finely ground composite mineralizer powder for later use;

[0079] Weigh out 500g of paraffin wax, beeswax, and oleic acid in a mass ratio of 91:7:2 and mix them. Heat and melt the mixture to obtain a mixed solution. Pour finely ground composite mineralizer powder into the mixed solution and add ZrO2 nanofiber material with a fiber length of 2-5μm and an aspect ratio of 5-10:1. Mix evenly to obtain a mixture.

[0080] Example 7: Removal of alumina-based ceramic core

[0081] The alloy blades and the alumina-based ceramic core are immersed together in a core-removing solution containing a mixture of saturated NaOH solution and 10% KOH solution (the mass ratio of NaOH to KOH in the core-removing solution is 5-10:1). The core-removing solution completely submerges the blades and cores, and they are repeatedly boiled at 200℃ for 24-120 hours until the alumina-based ceramic core is completely removed.

[0082] Experimental example:

[0083] The alumina-based ceramic cores prepared in Examples 1-6 and Comparative Examples 1-6 were tested for shrinkage rate, room temperature strength, and high temperature strength. The alumina-based ceramic cores prepared in Examples 1-6 and Comparative Examples 1-6 were removed using the removal method described in Example 7. The time for complete removal of the cores was recorded for each group. The results are shown in Table 1.

[0084] Table 1

[0085]

[0086] From Table 1, we can obtain:

[0087] Compared with Example 1, Comparative Examples 1-6 only differed in the composition of the solid powder. The complete decoction time for Comparative Examples 4-6 was 48 hours, but the product shrinkage rate was higher than that of Examples 1-6, and the room temperature strength and high temperature strength were both worse. The room temperature strength and high temperature strength of Comparative Examples 1-3 were better than those of Comparative Examples 4-6, but the product shrinkage rate was worse than that of Examples 1-6, and the decoction time was longer, making it difficult to solve the problem of decoction difficulty.

[0088] In summary, the ceramic core prepared by the scheme of the present invention can significantly improve the chemical removal rate of aluminum-based ceramic cores without reducing their strength and high-temperature strength, thus solving the problem of difficult core removal of aluminum-based ceramic cores that has long plagued the field of engine blade casting.

[0089] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. An alumina-based ceramic core, characterized in that, The ceramic core comprises the following raw materials: solid powder and plasticizer; the mass ratio of the solid powder to the plasticizer is 1:0.1-0.

8. The solid powder comprises the following raw materials in weight percentage: 0.5-10% composite mineralizer powder, 87%-99.5% alumina powder, and 0.1%-3% fiber material; The particle size of the composite mineralizer powder is 0.1-5μm, and the volume percentage of the powder smaller than 2.0μm in the composite mineralizer powder is 40%-80%. The composite mineralizer comprises two or more submicron-sized oxides, at least one of the submicron-sized oxides containing an element similar to Al. 3+ Cations with different valence states; The composite mineralizer powder includes at least two of CaO, SrO, BaO, Cr2O3, La2O3, Ga2O3, Co3O4, CeO2, SiO2, V2O5, and WO3, and includes at least one of CaO, SrO, BaO, Co3O4, CeO2, SiO2, V2O5, and WO3.

2. The alumina-based ceramic core according to claim 1, characterized in that, The fiber material has a length of 0.5-10 μm and an aspect ratio of 5-10:

1.

3. The alumina-based ceramic core according to claim 2, characterized in that, The fiber material is at least one of SiO2, Al2O3, La2O3, ZrO2, WO3, and mullite.

4. A method for preparing an alumina-based ceramic core according to any one of claims 1-3, characterized in that, The method includes the following steps: (1) Grind the composite mineralizer and mix it evenly to obtain finely ground composite mineralizer powder for later use; heat the plasticizer to melt it to obtain a mixed solution, then pour the composite mineralizer powder into the mixed solution, and add fiber material and mix evenly to obtain a mixture; (2) After adding alumina powder to the mixture and stirring for 12-24 hours, the mixture is injected into a core mold under a pressure of 3-5 MPa. After cooling, the core is removed and sintered to obtain an alumina-based ceramic core.

5. The method for preparing an alumina-based ceramic core according to claim 4, characterized in that, The sintering temperature is 1300-1380℃, and the holding time is 6-12h.

6. A method for removing an alumina-based ceramic core, characterized in that, The method includes the following steps: immersing the alloy blades together with the alumina-based ceramic core as described in any one of claims 1-3 in a core-removing solution and boiling for 12-72 hours.

7. The method for removing an alumina-based ceramic core according to claim 6, characterized in that, The core removal liquid includes the following raw materials: saturated NaOH solution and KOH solution; the mass ratio of NaOH to KOH in the core removal liquid is 5-10:1.

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