Titanium alloy casting composite ceramic core and preparation method and removal method thereof

Abstract

The application provides a composite ceramic core for titanium alloy casting and a preparation method and a removal method thereof. The composite ceramic core comprises a ceramic core base and a coating attached to the surface of the base. Raw materials of the ceramic core base comprise solid powder and a binder. The solid powder comprises, in terms of mass percentage, calcium hydroxide 30-55%, magnesium oxide 29-47.5%, metal aluminum powder 10-15% and zirconium oxide 5-15%. The mass ratio of the solid powder to the binder is 1:0.01-0.05. The coating is a yttrium oxide coating. The composite ceramic core has high bending strength and open porosity, and effectively reduces the hydration reaction occurring in the process of shell dewaxing, thereby preventing the collapse of the core and realizing rapid chemical corrosion core removal.

Description

Technical Field

[0001] This invention relates to the field of ceramic core technology, and more specifically, to a composite ceramic core for titanium alloy casting, its preparation method, and its removal method. 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 alloy melting and casting processes. The template material for the hollow portion of the blade is called a ceramic core, 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 ceramic core is a key component in forming the blade's internal cavity, and its manufacturing technology has become a crucial technology in hollow blade smelting and manufacturing.

[0003] Currently, the ceramic cores used domestically and internationally are mainly silicon oxide-based and alumina-based ceramic cores. Alumina-based ceramic cores have better thermal strength and stability, and exhibit structural stability during sintering and use, without high- or low-temperature crystal transformations, and good high-temperature resistance. However, removing aluminum-based ceramic cores is difficult and time-consuming, requiring repeated acid or alkali boiling to remove the core, which causes significant corrosion to the casting and severely affects its dimensional accuracy. Compared to aluminum-based ceramic cores, silicon-based ceramic cores have advantages such as lower sintering temperature, better controllability of cristobalite conversion rate, lower coefficient of thermal expansion, and better core removal performance. However, silicon oxide-based cores also generally suffer from low high-temperature strength, large deformation, and reaction with titanium alloys, affecting the production yield of alloy blades. Therefore, it is necessary to develop new types of ceramic cores to meet the requirements of aero-engine blades.

[0004] Calcium oxide, as a traditional refractory material, possesses a series of characteristics such as good chemical stability, good creep resistance, and no crystalline phase transformation. Calcium oxide is most likely to become a key core material for solving the problem of complex cavity forming of titanium alloys because, as a water-soluble ceramic core, it has low reactivity with molten titanium and is easy to remove from the core. However, calcium oxide ceramic cores face the problem of hydration during use. Summary of the Invention

[0005] Based on the above-mentioned technical problems in the existing technology, the present invention provides a composite ceramic core for titanium alloy casting. The composite ceramic core has high bending strength and porosity, and effectively reduces the hydration reaction that occurs during the dewaxing process of the shell, thereby preventing the core from collapsing, while achieving rapid core removal through chemical corrosion.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows:

[0007] A composite ceramic core for titanium alloy casting includes a ceramic core substrate and a coating adhered to the surface of the substrate; the raw materials of the ceramic core substrate include solid powder and a binder, wherein the solid powder, by mass percentage, comprises:

[0008] Calcium hydroxide 30-55%

[0009] Magnesium oxide 29-47.5%

[0010] 10-15% aluminum powder

[0011] Zirconia 5-15%;

[0012] The mass ratio of the solid powder to the binder is 1:0.01-0.05;

[0013] The coating is a yttrium oxide coating.

[0014] In some embodiments, the solid powder, by mass percentage, comprises:

[0015] Calcium hydroxide 47.2-47.5%

[0016] Magnesium oxide 31.5-31.7%

[0017] Aluminum powder 11-11.5%

[0018] Zirconia 10-10.5%.

[0019] In some embodiments, the average particle size of the calcium hydroxide ranges from 0.5 to 2 μm; the average particle size of the magnesium oxide ranges from 10 to 25 μm; the average particle size of the aluminum powder ranges from 5 to 20 μm; and the average particle size of the zirconium oxide ranges from 1 to 3 μm.

[0020] In some embodiments, the coating thickness is >150 μm; preferably, the coating thickness is ≤500 μm.

[0021] The present invention also provides a method for preparing a composite ceramic core for titanium alloy casting according to any of the above embodiments, the method comprising the following steps:

[0022] S1. Mix the calcium hydroxide, magnesium oxide, aluminum powder and zirconium oxide evenly to obtain a mixed powder;

[0023] S2. Add the aqueous solution of the binder to the mixed powder, mix evenly, and then pass through a 100-mesh sieve; take the sieved particles and place them in a mold for pressing to obtain a green body;

[0024] S3. The green body is dried and then sintered to obtain the ceramic core;

[0025] S4. Spray a yttrium oxide coating onto the surface of the ceramic core to obtain the composite ceramic core for titanium alloy.

[0026] In some embodiments, in step S2, the aqueous solution of the adhesive is a polyvinyl alcohol aqueous solution with a concentration of 3-10 wt%.

[0027] In some embodiments, the solid-liquid ratio of the mixed powder and the aqueous solution of the binder is 15-20 g: 1-3 mL.

[0028] In some embodiments, the sintering temperature in step S3 is 1350-1450°C.

[0029] In some implementations, the pressing pressure in step S2 is 3-10 MPa.

[0030] The present invention also provides a method for removing the above-mentioned composite ceramic core for titanium alloy casting, the method comprising the following steps:

[0031] The composite ceramic core is used as a template to cast the part, and then the part is immersed in an aqueous acetic acid solution to react; the reaction temperature is 60-100℃, and the concentration of the aqueous acetic acid solution is 5-10wt%.

[0032] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0033] This invention relates to a composite ceramic core for titanium alloy casting, using calcium hydroxide and magnesium oxide as main raw materials, and aluminum powder and zirconium oxide as additives. It utilizes the dehydration of calcium hydroxide during sintering to generate numerous pores, increasing the porosity and pore size of the ceramic core, thereby improving its collapse resistance. The volume expansion during the oxidation of aluminum powder to alumina effectively suppresses sintering and casting shrinkage. Alumina and zirconium oxide form a new phase, calcium aluminate, with calcium oxide at grain boundaries, which combines to form a framework and enhance the mechanical properties of the ceramic. The grain boundary pinning effect and solid solution strengthening mechanism of magnesium oxide significantly improve the core's resistance to hydration during shell dewaxing. This composite ceramic core exhibits excellent room temperature flexural strength, high temperature flexural strength, high porosity, and excellent hydration resistance, and does not react with titanium alloys. Using this composite ceramic core in titanium alloy casting effectively improves the chemical inertness between the ceramic core and the titanium alloy.

[0034] Furthermore, the composite ceramic core of the present invention is easy to remove and has a fast collapse rate, effectively solving the problem of difficult core removal for ceramic cores used in titanium alloy casting. Attached Figure Description

[0035] Figure 1 The image shows the XRD pattern of the ceramic core substrate prepared in Example 1 of this invention.

[0036] Figure 2 This is a SEM image of the surface of the composite ceramic core prepared in Example 1 of the present invention;

[0037] Figure 3 This is a SEM image of the fracture surface of the composite ceramic core prepared in Example 1 of the present invention. Detailed Implementation

[0038] Numerous specific details are set forth in the following description to provide a full understanding of the invention. However, the invention can be practiced in many other ways different from those described herein, and similar modifications can be made by those skilled in the art without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0039] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0040] Example 1: Preparation of Ceramic Core

[0041] Weigh out 50g of calcium hydroxide, magnesium oxide, aluminum powder, and zirconium oxide powder in sequence, ensuring their mass percentages are 47.4%, 31.6%, 11%, and 10%, respectively. Mix them and dry them thoroughly in an oven at 120℃. Transfer the dried powder to a ball mill jar with a ball-to-powder ratio of 2:1 and ball mill for 10-16 hours to obtain a mixed powder. Add 2.5mL of a 3-10wt% polyvinyl alcohol aqueous solution to the mixed powder at a solid-liquid ratio of 20g:1mL, mix thoroughly, and pass through a 100-mesh sieve. Weigh out a certain mass of the sieved powder and place it in a mold for pressing. The pressure used is 3-10MPa, and the holding time is 30-60s to obtain a green body. Transfer the green body to an oven at 100℃ for drying. Place the dried green body in a muffle furnace and sinter at 1400℃ to obtain a ceramic core.

[0042] The XRD pattern of the ceramic core obtained in this embodiment is as follows: Figure 1 As shown, the SEM images of the ceramic core surface and fracture surface are as follows: Figure 2 and Figure 3 As shown.

[0043] Comparative Example 1: Preparation of Ceramic Core

[0044] Weigh out 50g of calcium hydroxide, magnesium oxide, aluminum powder, and zirconium oxide powder in sequence, ensuring their mass percentages are 51%, 34%, 5%, and 10%, respectively. Mix them and dry them thoroughly in an oven at 120℃. Transfer the dried powder to a ball mill jar with a ball-to-powder ratio of 2:1 and ball mill for 10-16 hours to obtain a mixed powder. Add 2.5mL of a 3-10wt% polyvinyl alcohol aqueous solution to the mixed powder at a solid-liquid ratio of 20g:1mL, mix thoroughly, and pass through a 100-mesh sieve. Weigh out a certain mass of the sieved powder and place it in a mold for pressing. The pressure used is 3-10MPa, and the holding time is 30-60s to obtain a green body. Transfer the green body to an oven at 100℃ for drying. Place the dried green body in a muffle furnace and sinter at 1400℃ to obtain a ceramic core.

[0045] Comparative Example 2: Preparation of Ceramic Core

[0046] Weigh out 50g of calcium hydroxide, magnesium oxide, aluminum powder, and zirconium oxide powder in sequence, ensuring their mass percentages are 49.5%, 33%, 7.5%, and 10%, respectively. Mix them and dry them thoroughly in an oven at 120℃. Transfer the dried powder to a ball mill jar with a ball-to-powder ratio of 2:1 and ball mill for 10-16 hours to obtain a mixed powder. Add 2.5mL of a 3-10wt% polyvinyl alcohol aqueous solution to the mixed powder at a solid-liquid ratio of 20g:1mL, mix thoroughly, and pass through a 100-mesh sieve. Weigh out a certain mass of the sieved powder and place it in a mold for pressing. Use a pressure of 3-10MPa and a holding time of 30-60s to obtain a green body. Transfer the green body to an oven at 100℃ for drying. Place the dried green body in a muffle furnace and sinter at 1400℃ to obtain a ceramic core.

[0047] Comparative Example 3: Preparation of Ceramic Core

[0048] Weigh out 50g of calcium hydroxide, magnesium oxide, aluminum powder, and zirconium oxide powder in sequence, ensuring their mass percentages are 48%, 32%, 10%, and 10%, respectively. Mix them and dry them thoroughly in an oven at 120℃. Transfer the dried powder to a ball mill jar with a ball-to-powder ratio of 2:1 and ball mill for 10-16 hours to obtain a mixed powder. Add 2.5mL of a 3-10wt% polyvinyl alcohol aqueous solution to the mixed powder at a solid-liquid ratio of 20g:1mL, mix thoroughly, and pass through a 100-mesh sieve. Weigh out a certain mass of the sieved powder and place it in a mold for pressing. The pressure used is 3-10MPa, and the holding time is 30-60s to obtain a green body. Transfer the green body to an oven at 100℃ for drying. Place the dried green body in a muffle furnace and sinter at 1400℃ to obtain a ceramic core.

[0049] Comparative Example 4: Preparation of Ceramic Core

[0050] Weigh out 50g of calcium hydroxide, magnesium oxide, aluminum powder, and zirconium oxide powder in sequence, ensuring their mass percentages are 47.7%, 31.8%, 10.5%, and 10%, respectively. Mix them and dry them thoroughly in an oven at 120℃. Transfer the dried powder to a ball mill jar with a ball-to-powder ratio of 2:1 and ball mill for 10-16 hours to obtain a mixed powder. Add 2.5mL of a 3-10wt% polyvinyl alcohol aqueous solution to the mixed powder at a solid-liquid ratio of 20g:1mL, mix thoroughly, and pass through a 100-mesh sieve. Weigh out a certain mass of the sieved powder and place it in a mold for pressing. The pressure used is 3-10MPa, and the holding time is 30-60s to obtain a green body. Transfer the green body to an oven at 100℃ for drying. Place the dried green body in a muffle furnace and sinter at 1400℃ to obtain a ceramic core.

[0051] Comparative Example 5: Preparation of Ceramic Core

[0052] Weigh out 50g of calcium hydroxide, magnesium oxide, aluminum powder, and zirconium oxide powder in sequence, ensuring their mass percentages are 47.1%, 31.4%, 11.5%, and 10%, respectively. Mix them and dry them thoroughly in an oven at 120℃. Transfer the dried powder to a ball mill jar with a ball-to-powder ratio of 2:1 and ball mill for 10-16 hours to obtain a mixed powder. Add 2.5mL of a 3-10wt% polyvinyl alcohol aqueous solution to the mixed powder at a solid-liquid ratio of 20g:1mL, mix thoroughly, and pass through a 100-mesh sieve. Weigh out a certain mass of the sieved powder and place it in a mold for pressing. The pressure used is 3-10MPa, and the holding time is 30-60s to obtain a green body. Transfer the green body to an oven at 100℃ for drying. Place the dried green body in a muffle furnace and sinter at 1400℃ to obtain a ceramic core.

[0053] Comparative Example 6: Preparation of Ceramic Core

[0054] Weigh out 50g of calcium hydroxide, magnesium oxide, aluminum powder, and zirconium oxide powder in sequence, ensuring their mass percentages are 46.5%, 31%, 12.5%, and 10%, respectively. Mix them and dry them thoroughly in an oven at 120℃. Transfer the dried powder to a ball mill jar with a ball-to-powder ratio of 2:1 and ball mill for 10-16 hours to obtain a mixed powder. Add 2.5mL of a 3-10wt% polyvinyl alcohol aqueous solution to the mixed powder at a solid-liquid ratio of 20g:1mL, mix thoroughly, and pass through a 100-mesh sieve. Weigh out a certain mass of the sieved powder and place it in a mold for pressing. The pressure used is 3-10MPa, and the holding time is 30-60s to obtain a green body. Transfer the green body to an oven at 100℃ for drying. Place the dried green body in a muffle furnace and sinter at 1400℃ to obtain a ceramic core.

[0055] Comparative Example 7: Preparation of Ceramic Core

[0056] Weigh out 50g of calcium hydroxide, magnesium oxide, aluminum powder, and zirconium oxide powder in sequence, ensuring their mass percentages are 50.4%, 33.6%, 11%, and 5%, respectively. Mix them and dry them thoroughly in an oven at 120℃. Transfer the dried powder to a ball mill jar with a ball-to-powder ratio of 2:1 and ball mill for 10-16 hours to obtain a mixed powder. Add 2.5mL of a 3-10wt% polyvinyl alcohol aqueous solution to the mixed powder at a solid-liquid ratio of 20g:1mL, mix thoroughly, and pass through a 100-mesh sieve. Weigh out a certain mass of the sieved powder and place it in a mold for pressing. Use a pressure of 3-10MPa and a holding time of 30-60s to obtain a green body. Transfer the green body to an oven at 100℃ for drying. Place the dried green body in a muffle furnace and sinter at 1400℃ to obtain a ceramic core.

[0057] Comparative Example 8: Preparation of Ceramic Core

[0058] Weigh out 50g of calcium hydroxide, magnesium oxide, aluminum powder, and zirconium oxide powder in sequence, ensuring their mass percentages are 44.4%, 29.6%, 11%, and 15%, respectively. Mix them and dry them thoroughly in an oven at 120℃. Transfer the dried powder to a ball mill jar with a ball-to-powder ratio of 2:1 and ball mill for 10-16 hours to obtain a mixed powder. Add 2.5mL of a 3-10wt% polyvinyl alcohol aqueous solution to the mixed powder at a solid-liquid ratio of 20g:1mL, mix thoroughly, and pass through a 100-mesh sieve. Weigh out a certain mass of the sieved powder and place it in a mold for pressing. The pressure used is 3-10MPa, and the holding time is 30-60s to obtain a green body. Transfer the green body to an oven at 100℃ for drying. Place the dried green body in a muffle furnace and sinter at 1400℃ to obtain a ceramic core.

[0059] Comparative Example 9: Preparation of Ceramic Core

[0060] Weigh out 50g of calcium hydroxide, magnesium oxide, aluminum powder, and zirconium oxide powder in sequence, ensuring their mass percentages are 47.4%, 31.6%, 11%, and 10%, respectively. Mix them and dry them thoroughly in an oven at 120℃. Transfer the dried powder to a ball mill jar with a ball-to-powder ratio of 2:1 and ball mill for 10-16 hours to obtain a ceramic mixed powder. Add 2.5mL of a 3-10wt% polyvinyl alcohol aqueous solution to the mixed powder at a solid-liquid ratio of 20g:1mL, mix thoroughly, and pass through a 100-mesh sieve. Weigh out a certain mass of the sieved powder and place it in a mold for pressing. The pressure used is 3-10MPa, and the holding time is 30-60s to obtain a green body. Transfer the green body to an oven at 100℃ for drying. Place the dried green body in a muffle furnace and sinter at 1350℃ to obtain a ceramic core.

[0061] Comparative Example 10: Preparation of Ceramic Core

[0062] Weigh out 50g of calcium hydroxide, magnesium oxide, aluminum powder, and zirconium oxide powder in sequence, ensuring their mass percentages are 47.4%, 31.6%, 11%, and 10%, respectively. Mix them and dry them thoroughly in an oven at 120℃. Transfer the dried powder to a ball mill jar with a ball-to-powder ratio of 2:1 and ball mill for 10-16 hours to obtain a mixed powder. Add 2.5mL of a 3-10wt% polyvinyl alcohol aqueous solution to the mixed powder at a solid-liquid ratio of 20g:1mL, mix thoroughly, and pass through a 100-mesh sieve. Weigh out a certain mass of the sieved powder and place it in a mold for pressing. The pressure used is 3-10MPa, and the holding time is 30-60s to obtain a green body. Transfer the green body to an oven at 100℃ for drying. Place the dried green body in a muffle furnace and sinter at 1450℃ to obtain a ceramic core.

[0063] Comparative Example 11: Preparation of Ceramic Core

[0064] Weigh out 50g of calcium hydroxide, magnesium oxide, aluminum powder, and zirconium oxide powder in sequence, ensuring their mass percentages are 39.5%, 39.5%, 11%, and 10%, respectively. Mix them and dry them thoroughly in an oven at 120℃. Transfer the dried powder to a ball mill jar with a ball-to-powder ratio of 2:1 and ball mill for 10-16 hours to obtain a mixed powder. Add 2.5mL of a 3-10wt% polyvinyl alcohol aqueous solution to the mixed powder at a solid-liquid ratio of 20g:1mL, mix thoroughly, and pass through a 100-mesh sieve. Weigh out a certain mass of the sieved powder and place it in a mold for pressing. The pressure used is 3-10MPa, and the holding time is 30-60s to obtain a green body. Transfer the green body to an oven at 100℃ for drying. Place the dried green body in a muffle furnace and sinter at 1400℃ to obtain a ceramic core.

[0065] Comparative Example 12: Preparation of Ceramic Core

[0066] Weigh out 50g of calcium hydroxide, magnesium oxide, aluminum powder, and zirconium oxide powder in sequence, ensuring their mass percentages are 31.6%, 47.4%, 11%, and 10%, respectively. Mix them and dry them thoroughly in an oven at 120℃. Transfer the dried powder to a ball mill jar with a ball-to-powder ratio of 2:1 and ball mill for 10-16 hours to obtain a mixed powder. Add 2.5mL of a 3-10wt% polyvinyl alcohol aqueous solution to the mixed powder at a solid-liquid ratio of 20g:1mL, mix thoroughly, and pass through a 100-mesh sieve. Weigh out a certain mass of the sieved powder and place it in a mold for pressing. The pressure used is 3-10MPa, and the holding time is 30-60s to obtain a green body. Transfer the green body to an oven at 100℃ for drying. Place the dried green body in a muffle furnace and sinter at 1400℃ to obtain a ceramic core.

[0067] Example 2: Preparation of composite ceramic core for titanium alloy casting

[0068] 50g of calcium hydroxide, magnesium oxide, aluminum powder, and zirconium oxide powder were weighed in sequence, ensuring their mass percentages were 47.4%, 31.6%, 11%, and 10%, respectively. The mixture was then thoroughly dried in an oven at 120℃. The dried powder was transferred to a ball mill jar with a ball-to-powder ratio of 2:1 and ball-milled for 10-16 hours to obtain a mixed powder. 2.5mL of a 3-10wt% polyvinyl alcohol aqueous solution was added to the mixed powder at a solid-liquid ratio of 20g:1mL. After thorough mixing, the mixture was passed through a 100-mesh sieve. A certain mass of the sieved powder was weighed and placed in a mold for pressing at a pressure of 3-10MPa for 30-60s to obtain a green body. The green body was then dried in an oven at 100℃. The dried green body was placed in a muffle furnace and sintered at 1400℃ to obtain a ceramic core. A 200μm yttrium oxide coating was sprayed onto the surface of the ceramic core using plasma spraying to obtain a composite ceramic core for titanium alloy casting.

[0069] Comparative Example 13: Preparation of Composite Ceramic Cores for Titanium Alloy Casting

[0070] 50g of calcium hydroxide, magnesium oxide, aluminum powder, and zirconium oxide powder were weighed in sequence, ensuring their mass percentages were 47.4%, 31.6%, 11%, and 10%, respectively. The mixture was then thoroughly dried in an oven at 120℃. The dried powder was transferred to a ball mill jar with a ball-to-powder ratio of 2:1 and ball-milled for 10-16 hours to obtain a mixed powder. 2.5mL of a 3-10wt% polyvinyl alcohol aqueous solution was added to the mixed powder at a solid-liquid ratio of 20g:1mL. After thorough mixing, the mixture was passed through a 100-mesh sieve. A certain mass of the sieved powder was weighed and placed in a mold for pressing at a pressure of 3-10MPa for 30-60s to obtain a green body. The green body was then dried in an oven at 100℃. The dried green body was placed in a muffle furnace and sintered at 1400℃ to obtain a ceramic core. A 150μm yttrium oxide coating was sprayed onto the surface of the ceramic core using plasma spraying to obtain a composite ceramic core for titanium alloy casting.

[0071] The composite ceramic and titanium alloy casting composite ceramic cores prepared in Examples 1-2 and Comparative Examples 1-13 were tested for their product expansion rate, porosity, room temperature bending strength, high temperature bending strength and titanium alloy reaction inertness. The results are shown in Table 1.

[0072] Table 1

[0073]

[0074] As shown in Table 1, compared with Example 1, the mass ratio of calcium hydroxide to magnesium oxide remained unchanged in Comparative Examples 1-8, with only the content of metallic aluminum powder changing. Increasing the content of metallic aluminum powder can significantly reduce the volume shrinkage rate, room temperature flexural strength, and high temperature flexural strength of the ceramic core, and increase the porosity of the ceramic core. Compared with Example 1, when the mass ratio of calcium hydroxide to magnesium oxide was 6:4, the ceramic core exhibited the lowest volume shrinkage rate and the highest flexural strength in Comparative Examples 11-12. Compared with Example 2, Comparative Example 13 only showed a change in coating thickness. When the thickness of the yttrium oxide coating was greater than 150 μm, it provided excellent isolation, preventing the reaction between the composite ceramic core and the titanium alloy.

[0075] The composite ceramic core was weighed every two days to compare the weight change before and after hydration.

[0076] The ceramic cores prepared in Example 1, Comparative Example 1, and Comparative Example 7, and the composite ceramic core prepared in Example 2 were weighed and placed in a constant temperature and humidity chamber for hydration resistance testing. The temperature of the constant temperature and humidity chamber was 30°C and the humidity was maintained at 98%. The weight changes of the ceramic cores / composite ceramic cores after different hydration times were recorded, and the results are shown in Table 2.

[0077] Table 2

[0078]

[0079] As can be seen from Table 2, increasing the content of zirconium oxide and aluminum powder can significantly improve the hydration resistance of ceramic cores. Adding yttrium oxide coating further improves the hydration resistance. After 13 days of hydration test, the weight gain rate of the prepared composite ceramic core is only 0.081%, which shows good hydration resistance and can meet the requirements of titanium alloy casting.

[0080] Example 3: Removal of composite ceramic core for titanium alloy casting

[0081] A titanium alloy casting was obtained by using a composite ceramic core as a template for simulated casting. Several small holes were pre-drilled on the surface of the casting. The casting was then immersed in an aqueous solution containing 10% acetic acid at 80°C for 4 hours under atmospheric pressure, while simultaneously undergoing ultrasonic treatment.

[0082] Example 4: Removal of composite ceramic core for titanium alloy casting

[0083] A titanium alloy casting was obtained by using a composite ceramic core as a template for simulated casting. Several small holes were pre-drilled on the surface of the casting. The casting was then immersed in water at 60°C for 4 hours under atmospheric pressure, while simultaneously undergoing ultrasonic treatment.

[0084] Comparative Example 14: Removal of Composite Ceramic Cores for Titanium Alloy Casting

[0085] A titanium alloy casting was obtained by using a composite ceramic core as a template for simulated casting. Several small holes were pre-drilled on the surface of the casting. The casting was then immersed in a 10% acetic acid aqueous solution at 50°C for 4 hours under atmospheric pressure, while simultaneously undergoing ultrasonic treatment.

[0086] Comparative Example 15: Removal of Composite Ceramic Cores for Titanium Alloy Casting

[0087] A titanium alloy casting was obtained by using a composite ceramic core as a template for simulated casting. Several small holes were pre-drilled on the surface of the casting. The casting was then immersed in water at 80°C for 4 hours under atmospheric pressure, while simultaneously undergoing ultrasonic treatment.

[0088] The composite ceramic cores for titanium alloy casting prepared in Example 2 were removed using the removal methods of Examples 3-4 and Comparative Examples 14-15. The complete removal time for each group was recorded, and the results are shown in Table 3.

[0089] Table 3

[0090]

[0091] As can be seen from Table 3, the combination of acetic acid aqueous solution and ultrasonic dispersion effectively removes the ceramic core, and increasing the solution temperature effectively shortens the core removal time.

[0092] In summary, the ceramic core for titanium alloy casting prepared by the scheme of the present invention can significantly improve the chemical removal rate of the ceramic core while reducing the volume shrinkage rate of the ceramic core, and at the same time maintain the appropriate room temperature bending strength, high temperature bending strength, porosity and hydration resistance of the ceramic core, thus solving the long-standing problem of difficult core removal of ceramic cores for titanium alloy casting from the source.

[0093] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0094] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the appended claims.

Claims

1. A composite ceramic core for titanium alloy casting, characterized in that, Includes a ceramic core substrate and a coating attached to the surface of the substrate; The raw materials for the ceramic core matrix include solid powder and binder, wherein the solid powder, by mass percentage, comprises: Calcium hydroxide 30-55% Magnesium oxide 29-47.5% 10-15% aluminum powder Zirconia 5-15%; The mass ratio of the solid powder to the binder is 1:0.01-0.05; The coating is a yttrium oxide coating.

2. The composite ceramic core for titanium alloy casting according to claim 1, characterized in that, The solid powder, by mass percentage, includes: Calcium hydroxide 47.2-47.5% Magnesium oxide 31.5-31.7% Aluminum powder 11-11.5% Zirconia 10-10.5%.

3. The composite ceramic core for titanium alloy casting according to claim 1, characterized in that, The average particle size of the calcium hydroxide is 0.5-2 μm; the average particle size of the magnesium oxide is 10-25 μm; the average particle size of the aluminum powder is 5-20 μm; and the average particle size of the zirconium oxide is 1-3 μm.

4. The composite ceramic core for titanium alloy casting according to claim 1, characterized in that, The coating thickness is >150μm.

5. The method for preparing a composite ceramic core for titanium alloy casting according to any one of claims 1-4, characterized in that, Includes the following steps: S1. Mix the calcium hydroxide, magnesium oxide, aluminum powder and zirconium oxide evenly to obtain a mixed powder; S2. Add the aqueous solution of the binder to the mixed powder, mix evenly, and then pass through a 100-mesh sieve; take the sieved particles and place them in a mold for pressing to obtain a green body; S3. The green body is dried and then sintered to obtain the ceramic core; S4. Spray a yttrium oxide coating onto the surface of the ceramic core to obtain the composite ceramic core for titanium alloy casting.

6. The composite ceramic core for titanium alloy casting according to claim 5, characterized in that, In step S2, the aqueous solution of the adhesive is a polyvinyl alcohol aqueous solution with a concentration of 3-10 wt%.

7. The composite ceramic core for titanium alloy casting according to claim 6, characterized in that, The solid-liquid ratio of the mixed powder and the aqueous solution of the binder is 15-20g:1-3mL.

8. The composite ceramic core for titanium alloy casting according to claim 5, characterized in that, In step S3, the sintering temperature is 1350-1450℃.

9. The composite ceramic core for titanium alloy casting according to claim 5, characterized in that, In step S2, the pressing pressure is 3-10 MPa.

10. The method for removing the composite ceramic core for titanium alloy casting according to any one of claims 1-4, characterized in that, Includes the following steps: The composite ceramic core is used as a template to cast the part, and then the part is immersed in an aqueous acetic acid solution to react; the reaction temperature is 60-100℃, and the concentration of the aqueous acetic acid solution is 5-10wt%.

Images