Silicon-based ceramic, preparation method and application thereof, and method for removing ceramic core for titanium alloy casting

Abstract

The present invention relates to a silicon-based ceramic, a preparation method and application thereof, and a method for removing a ceramic core for titanium alloy casting. The raw materials of the silicon-based ceramic include solid powder and a binder, wherein the solid powder consists of 60-100wt% of silicon dioxide, 0-10wt% of mullite, 0-10wt% of kaolin, and 0-20wt% of yttrium oxide; the mass ratio of the solid powder to the binder is 1:0.01-0.05; the contents of the mullite, kaolin, and yttrium oxide are all greater than 0; and the silicon-based ceramic of the present invention has excellent room temperature and high temperature mechanical properties and good dissolution performance.

Description

Technical Field

[0001] The present invention relates to the technical field of ceramic cores for titanium alloy casting, and more particularly to a silicon-based ceramic, a preparation method and application thereof, and a method for removing the silicon-based ceramic core. Background Art

[0002] The hollow blades of aircraft engines and gas turbines are precision parts that are subjected to high temperature and high pressure conditions on the turbine rotor at the rear end of the calcination chamber. They are usually manufactured using an alloy melt casting process. The template material for the hollow part of the hollow blade is called a ceramic core. It is a prefabricated part that needs to be formed and sintered before casting. It needs to be pre-filled into the ceramic shell to provide shape stability and high-temperature mechanical properties during casting. After casting is completed, 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 ceramic products used in precision casting.

[0003] At present, the ceramic cores used at home and abroad mainly include aluminum-based ceramic cores and silicon-based ceramic cores. Aluminum-based ceramic cores have better thermal strength and thermal stability, and are structurally stable during sintering and use, without high- and low-temperature crystal transformations, and have good high-temperature resistance. However, aluminum-based ceramic cores are difficult to de-core, which inhibits their widespread practical application and development. Compared with aluminum-based ceramic cores, silicon-based ceramic cores have the advantages of low sintering temperature, better controllability of cristobalite conversion rate, small thermal expansion coefficient, and good de-coring performance. However, silicon oxide-based cores also generally have problems such as low high-temperature strength, large deformation, and reaction with titanium alloys, which affect the production qualification rate and cost of alloy blades.

[0004] In order to solve the problems of poor high-temperature mechanical properties, large deformation, and reaction with titanium alloy in silicon-based ceramic core chambers, the present invention provides a silicon-based ceramic core for titanium alloy casting and a preparation and removal method thereof. Summary of the Invention

[0005] Based on the above technical problems existing in the prior art, the present invention provides a silicon-based ceramic having excellent room temperature and high temperature mechanical properties and good dissolution performance.

[0006] In order to achieve the above object, the technical solution of the present invention is as follows:

[0007] A silicon-based ceramic, wherein the raw materials of the silicon-based ceramic include solid powder and a binder, wherein the solid powder is composed of 60-100wt% silicon dioxide, 0-10wt% mullite, 0-10wt% kaolin and 0-20wt% yttrium oxide; the mass ratio of the solid powder to the binder is 1:0.01-0.05; and the contents of the mullite, kaolin and yttrium oxide are all greater than 0.

[0008] In some embodiments, the average particle size of the silicon dioxide is 25-40 μm; the average particle size of the mullite is 10-20 μm; the average particle size of the yttrium oxide is 5-15 μm; and the average particle size of the kaolin is 0.5-2 μm.

[0009] The present invention also provides a method for preparing the silicon-based ceramic according to any of the above embodiments, the method comprising the following steps:

[0010] Silicon dioxide, mullite, kaolin and yttrium oxide powders are mixed evenly to obtain a mixed powder; a binder aqueous solution is then added and mixed evenly; the mixture is then pressed and formed to obtain a green body; the green body is dried and then sintered to obtain a silicon-based ceramic; and finally, an yttrium oxide coating is sprayed on the surface of the silicon-based ceramic to obtain the ceramic core.

[0011] In some embodiments, the sintering temperature is 1250-1450°C.

[0012] In some embodiments, the sintering holding time is 3-6 hours.

[0013] In some embodiments, the binder is polyvinyl alcohol; and the concentration of the binder aqueous solution is 3-10 wt %.

[0014] In some embodiments, the solid-to-liquid ratio of the mixed powder to the binder aqueous solution is 15-20 g:1-3 mL.

[0015] In some embodiments, the method for preparing the silicon-based ceramic comprises the following steps:

[0016] S1, mixing the silica, mullite, kaolin and yttrium oxide, and fully drying them at a temperature of 100-120° C.;

[0017] S2. ball-milling the fully dried raw materials to obtain a mixed powder; wherein the ball-to-material ratio is 2:1;

[0018] S3, adding the binder aqueous solution to the mixed powder, mixing evenly and then passing through a 100 mesh sieve; wherein the solid-liquid ratio is 15-20g:1-3mL;

[0019] S4. The powder under the sieve is placed in a mold and pressed at a pressure of 3-10 MPa for 30-60 seconds to obtain a green compact;

[0020] S5, fully drying the green body at a temperature of 100-120° C.;

[0021] S6. Place the dried green body in a muffle furnace and sinter it at a temperature of 1250-1450° C. to obtain the silicon-based ceramic.

[0022] The present invention also provides a silicon-based ceramic core, which includes a silicon-based ceramic and a coating on the silicon-based ceramic; the silicon-based ceramic is the silicon-based ceramic of any of the above-mentioned embodiments or the silicon-based ceramic obtained by the preparation method of any of the above-mentioned embodiments, and the coating is an yttrium oxide coating.

[0023] In some embodiments, the thickness of the coating is greater than 100 μm; preferably, the thickness of the coating is 150-300 μm; more preferably, 150-250 μm.

[0024] The present invention also provides a method for preparing the silicon-based ceramic core, which comprises the following steps:

[0025] The silicon-based ceramic is prepared by using the method for preparing the silicon-based ceramic in any of the above embodiments, and then an yttrium oxide coating is sprayed on the surface of the silicon-based ceramic to obtain the silicon-based ceramic core.

[0026] In some embodiments, the spraying method is: spraying the yttrium oxide coating on the surface of the silicon-based ceramic using a plasma spraying method.

[0027] The present invention also provides a method for removing a silicon-based ceramic core for titanium alloy casting, the method comprising the following steps:

[0028] (1) using the silicon-based ceramic core or the silicon-based ceramic core obtained by the above-mentioned method for preparing the silicon-based ceramic core as a template to cast a titanium alloy to obtain a casting;

[0029] (2) placing the casting with the silicon-based ceramic core in a mixed alkali solution and boiling it while ultrasonically treating the casting;

[0030] (3) After the treatment in the mixed alkali solution is completed, the casting is taken out and soaked in water to remove the residual alkali solution;

[0031] (4) immersing the casting treated in step (3) in a hydrochloric acid solution containing a corrosion inhibitor, reacting at a temperature of 80-100° C., and simultaneously performing ultrasonic treatment;

[0032] (5) Repeat steps (2) to (4) until the ceramic core is completely removed.

[0033] In some embodiments, the mixed alkali solution includes 30-60 wt % potassium hydroxide and 5-15 wt % sodium fluoride.

[0034] In some embodiments, the corrosion inhibitor is at least two of copper salts, molybdates, tungstates, zinc salts, potassium iodate, tropaeolum orange, quaternary ammonium salts, Mannich bases, cetyltrimethylammonium bromide, sodium lauroyl sarcosinate, and sodium lauryl sulfate. The use of a composite corrosion inhibitor can effectively inhibit the reaction between hydrochloric acid and the titanium alloy under high-temperature, high-concentration hydrochloric acid solution conditions, thereby preventing damage to the titanium alloy during the core removal process.

[0035] In some embodiments, in step (2), the casting with the silicon-based ceramic core is boiled in the mixed alkali solution for 12-36 hours at a pressure of natural atmospheric pressure.

[0036] In some embodiments, in step (4), the concentration of the hydrochloric acid solution is ≤6 mol / L; preferably, 4-6 mol / L.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] The silicon-based ceramic of the present invention uses silicon dioxide as a raw material and mullite, kaolin, and yttrium oxide as mineralizers. This material promotes sintering and the formation of cristobalite, increasing the open porosity and improving its collapsibility. It also forms new phases that combine to form a skeleton, enhancing the mechanical properties of the silicon-based ceramic. Using this silicon-based ceramic as a ceramic core for titanium alloy casting, and coating it with an yttrium oxide coating, it effectively improves the chemical inertness between the ceramic core and the titanium alloy.

[0039] The preparation method of the silicon-based ceramic provided by the present invention enables the obtained silicon-based ceramic to have excellent room-temperature high-temperature bending strength, high porosity and good dissolution performance.

[0040] The removal method provided by the present invention adopts alternate immersion of alkali and acid solutions in combination with corrosion inhibitors to allow silicon dioxide and alkali solution, yttrium oxide and hydrochloric acid solution to fully react and disintegrate, effectively improving the chemical removal efficiency of ceramic cores, and solving the problem of ceramic core removal difficulties that has long plagued the titanium alloy casting field from the source. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 This is an SEM image of the fracture surface of the silicon-based ceramic prepared in Example 1 of the present invention;

[0042] Figure 2 This is the XRD pattern of the silicon-based ceramic core for titanium alloy casting prepared in Example 2 of the present invention;

[0043] Figure 3 This is an SEM image of the fracture of the silicon-based ceramic core for titanium alloy casting prepared in Example 2 of the present invention. DETAILED DESCRIPTION

[0044] The following description sets forth numerous specific details to facilitate a thorough understanding of the present invention. However, the present invention can be implemented in many other ways than those described herein, and those skilled in the art may make similar modifications without departing from the scope of the present invention. Therefore, the present invention is not limited to the specific implementations disclosed below.

[0045] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in this specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0046] Example 1

[0047] A preparation method of silicon-based ceramics comprises the following steps:

[0048] 20 g of silica, mullite, kaolin, and yttrium oxide powders were weighed in sequence, ensuring a mass ratio of 15:2:1:2. The mixture was then thoroughly dried in a 120°C oven. The dried powders were transferred to a ball mill and ball milled for 10-16 hours to obtain a ceramic core powder with a ball-to-material ratio of 2:1. 1-3 mL of a 3-10 wt% aqueous solution of polyvinyl alcohol was added to the mixed powders, mixed evenly, and passed through a 100-mesh sieve. A certain mass of the undersize powder was weighed and placed in a mold for pressing at a pressure of 6-12 MPa for 30-60 seconds to obtain a green body.

[0049] The green body is transferred to an oven at 100°C for drying; the dried green body is placed in a muffle furnace and sintered at 1300°C for 4-6 hours to form a silicon-based ceramic.

[0050] The SEM image of the silicon-based ceramic fracture obtained in this embodiment is as follows Figure 1 shown.

[0051] Comparative Example 1

[0052] A preparation method of silicon-based ceramics comprises the following steps:

[0053] 20 g of silica and mullite powder were weighed in sequence, ensuring a mass ratio of 18:2. After mixing, the mixture was thoroughly dried in a 120°C oven. The dried powder was transferred to a ball mill and ball milled for 10-16 hours to obtain a ceramic core powder with a ball-to-material ratio of 2:1. 1-3 mL of a 3-10 wt% aqueous solution of polyvinyl alcohol was added to the mixed powder, mixed evenly, and passed through a 100-mesh sieve. A certain mass of the undersize powder was weighed and placed in a mold for pressing at a pressure of 6-12 MPa for 30-60 seconds to obtain a green body.

[0054] The green body is transferred into an oven at 100° C. for drying; the dried green body is placed in a muffle furnace and sintered at 1300° C. for 4-6 hours to obtain a silicon base.

[0055] Comparative Example 2

[0056] A preparation method of silicon-based ceramics comprises the following steps:

[0057] 20 g of silica, mullite, and kaolin powders were weighed in sequence, ensuring a mass ratio of 17.5:2:0.5. The mixture was then thoroughly dried in a 120°C oven. The dried powders were transferred to a ball mill and ball milled for 10-16 hours to obtain a ceramic core powder with a ball-to-material ratio of 2:1. 1-3 mL of a 3-10 wt% aqueous solution of polyvinyl alcohol was added to the mixed powders, mixed evenly, and passed through a 100-mesh sieve. A certain mass of the undersize powder was weighed and placed in a mold for pressing at a pressure of 6-12 MPa for 30-60 seconds to obtain a green body.

[0058] The green body is transferred into an oven at 100° C. for drying; the dried green body is placed in a muffle furnace and sintered at 1300° C. for 4-6 hours to obtain silicon-based ceramics.

[0059] Comparative Example 3

[0060] A preparation method of silicon-based ceramics comprises the following steps:

[0061] 20 g of silica, mullite, and kaolin powders were weighed in sequence, ensuring a mass ratio of 17:2:1. The mixture was then thoroughly dried in a 120°C oven. The dried powders were transferred to a ball mill and ball milled for 10-16 hours to obtain a ceramic core powder with a ball-to-material ratio of 2:1. 1-3 mL of a 3-10 wt% aqueous solution of polyvinyl alcohol was added to the mixed powders, mixed evenly, and passed through a 100-mesh sieve. A certain mass of the undersize powder was weighed and placed in a mold for pressing at a pressure of 6-12 MPa for 30-60 seconds to obtain a green body.

[0062] The green body is transferred into an oven at 100° C. for drying; the dried green body is placed in a muffle furnace and sintered at 1300° C. to obtain silicon-based ceramics.

[0063] Comparative Example 4

[0064] A preparation method of silicon-based ceramics comprises the following steps:

[0065] 20 g of silica, mullite, and kaolin powders were weighed in sequence, ensuring a mass ratio of 16.5:2:1.5. The mixture was then thoroughly dried in a 120°C oven. The dried powders were transferred to a ball mill and ball milled for 10-16 hours to obtain a ceramic core powder with a ball-to-material ratio of 2:1. 1-3 mL of a 3-10 wt% aqueous solution of polyvinyl alcohol was added to the mixed powders, mixed evenly, and passed through a 100-mesh sieve. A certain mass of the undersize powder was weighed and placed in a mold for pressing at a pressure of 6-12 MPa for 30-60 seconds to obtain a green body.

[0066] The green body is transferred into an oven at 100° C. for drying; the dried green body is placed in a muffle furnace and sintered at 1300° C. for 4-6 hours to obtain silicon-based ceramics.

[0067] Comparative Example 5

[0068] A preparation method of silicon-based ceramics comprises the following steps:

[0069] 20 g of silica, mullite, kaolin, and yttrium oxide powders were weighed in sequence, ensuring a mass ratio of 16:2:1:1. The mixture was then thoroughly dried in a 120°C oven. The dried powders were transferred to a ball mill and ball milled for 10-16 hours to obtain a ceramic core powder with a ball-to-material ratio of 2:1. 1-3 mL of a 3-10 wt% aqueous solution of polyvinyl alcohol was added to the mixed powders, mixed evenly, and passed through a 100-mesh sieve. A certain mass of the undersize powder was weighed and placed in a mold for pressing at a pressure of 6-12 MPa for 30-60 seconds to obtain a green body.

[0070] The green body is transferred into an oven at 100° C. for drying; the dried green body is placed in a muffle furnace and sintered at 1300° C. for 4-6 hours to obtain silicon-based ceramics.

[0071] Comparative Example 6

[0072] A preparation method of silicon-based ceramics comprises the following steps:

[0073] 20 g of silica, mullite, kaolin, and yttrium oxide powders were weighed in sequence, ensuring a mass ratio of 14:2:1:3. The mixture was then thoroughly dried in a 120°C oven. The dried powders were transferred to a ball mill and ball milled for 10-16 hours to obtain a ceramic core powder with a ball-to-material ratio of 2:1. 1-3 mL of a 3-10 wt% aqueous solution of polyvinyl alcohol was added to the mixed powders, mixed evenly, and passed through a 100-mesh sieve. A certain mass of the undersize powder was weighed and placed in a mold for pressing at a pressure of 6-12 MPa for 30-60 seconds to obtain a green body.

[0074] The green body is transferred into an oven at 100° C. for drying; the dried green body is placed in a muffle furnace and sintered at 1300° C. to obtain silicon-based ceramics.

[0075] Comparative Example 7

[0076] A preparation method of silicon-based ceramics comprises the following steps:

[0077] 20 g of silica, mullite, kaolin, and yttrium oxide powders were weighed in sequence, ensuring a mass ratio of 13:2:1:4. The mixture was then thoroughly dried in a 120°C oven. The dried powders were transferred to a ball mill and ball milled for 10-16 hours to obtain a ceramic core powder with a ball-to-material ratio of 2:1. 1-3 mL of a 3-10 wt% aqueous solution of polyvinyl alcohol was added to the mixed powders, mixed evenly, and passed through a 100-mesh sieve. A certain mass of the undersize powder was weighed and placed in a mold for pressing at a pressure of 6-12 MPa for 30-60 seconds to obtain a green body.

[0078] The green body is transferred into an oven at 100° C. for drying; the dried green body is placed in a muffle furnace and sintered at 1300° C. to obtain silicon-based ceramics.

[0079] Example 2

[0080] A preparation method of a silicon-based ceramic core for titanium alloy casting comprises the following steps:

[0081] 20 g of silica, mullite, kaolin, and yttrium oxide powders were weighed in sequence, ensuring a mass ratio of 15:2:1:2. The mixture was then thoroughly dried in a 120°C oven. The dried powders were transferred to a ball mill and ball milled for 10-16 hours to obtain a ceramic core powder with a ball-to-material ratio of 2:1. 1-3 mL of a 3-10 wt% aqueous solution of polyvinyl alcohol was added to the mixed powders, mixed evenly, and passed through a 100-mesh sieve. A certain mass of the undersize powder was weighed and placed in a mold for pressing at a pressure of 6-12 MPa for 30-60 seconds to obtain a green body.

[0082] The green body is transferred to an oven at 100°C for drying; the dried green body is placed in a muffle furnace and sintered at 1300°C for 4-6 hours to obtain silicon-based ceramics;

[0083] A 200 μm yttria coating was sprayed on the surface of silicon-based ceramics by plasma spraying to obtain a silicon-based ceramic core for titanium alloy casting.

[0084] The XRD patterns and fracture SEM patterns of the silicon-based ceramic core for titanium alloy casting obtained in this embodiment are shown in FIG. Figure 2 and Figure 3 shown.

[0085] Comparative Example 8

[0086] A preparation method of a silicon-based ceramic core for titanium alloy casting comprises the following steps:

[0087] 20 g of silica, mullite, kaolin, and yttrium oxide powders were weighed in sequence, ensuring a mass ratio of 15:2:1:2. The mixture was then thoroughly dried in a 120°C oven. The dried powders were transferred to a ball mill and ball milled for 10-16 hours to obtain a ceramic core powder with a ball-to-material ratio of 2:1. 1-3 mL of a 3-10 wt% aqueous solution of polyvinyl alcohol was added to the mixed powders, mixed evenly, and passed through a 100-mesh sieve. A certain mass of the undersize powder was weighed and placed in a mold for pressing at a pressure of 6-12 MPa for 30-60 seconds to obtain a green body.

[0088] The green body is transferred to an oven at 100°C for drying; the dried green body is placed in a muffle furnace and sintered at 1300°C for 4-6 hours to obtain silicon-based ceramics;

[0089] A 100 μm yttria coating was sprayed on the surface of silicon-based ceramics by plasma spraying to obtain a silicon-based ceramic core for titanium alloy casting.

[0090] Comparative Example 9

[0091] A preparation method of a silicon-based ceramic core for titanium alloy casting comprises the following steps:

[0092] 20 g of silica, mullite, kaolin, and yttrium oxide powders were weighed in sequence, ensuring a mass ratio of 15:2:1:2. The mixture was then thoroughly dried in a 120°C oven. The dried powders were transferred to a ball mill and ball milled for 10-16 hours to obtain a ceramic core powder with a ball-to-material ratio of 2:1. 1-3 mL of a 3-10 wt% aqueous solution of polyvinyl alcohol was added to the mixed powders, mixed evenly, and passed through a 100-mesh sieve. A certain mass of the undersize powder was weighed and placed in a mold for pressing at a pressure of 6-12 MPa for 30-60 seconds to obtain a green body.

[0093] The green body was transferred to an oven at 100°C for drying; the dried green body was placed in a muffle furnace and sintered at 1300°C for silicon-based ceramics;

[0094] A 300 μm yttria coating was sprayed on the surface of a ceramic core by plasma spraying to obtain a silicon-based ceramic core for titanium alloy casting.

[0095] Example 3

[0096] A method for removing a silicon-based ceramic core for titanium alloy casting comprises the following steps:

[0097] A titanium alloy simulation casting is performed using a silicon-based ceramic core for titanium alloy casting as a template to obtain a casting; the casting is immersed in a mixed solution containing 50wt% potassium hydroxide and 10wt% sodium fluoride and boiled for 8 hours at a natural atmospheric pressure, and the casting is ultrasonically treated at the same time; the casting is taken out and repeatedly soaked in deionized water; the casting is then immersed in a hydrochloric acid solution containing copper chloride and nasturtium orange, kept warm at 90°C for 4 hours, and the casting is ultrasonically treated at the same time; the concentrations of copper chloride, nasturtium orange, and hydrochloric acid are 10g / L, 1mmol / L, and 6mol / L, respectively; the casting is taken out and repeatedly soaked in deionized water, and then placed in a mixed solution containing 50wt% potassium hydroxide and 10wt% sodium fluoride and boiled for 8 hours; the casting is alternately treated with alkali and acid solutions until the core is completely removed.

[0098] Comparative Example 10

[0099] A method for removing a silicon-based ceramic core for titanium alloy casting comprises the following steps:

[0100] A silicon-based ceramic core for titanium alloy casting is used as a template for titanium alloy simulation casting to obtain a casting; the casting is immersed in a 50wt% potassium hydroxide solution and boiled for 8 hours at a natural atmospheric pressure, and the casting is ultrasonically treated at the same time; the casting is taken out and repeatedly soaked in deionized water; the casting is then immersed in a hydrochloric acid solution containing copper chloride and nasturtium orange, kept warm at 90°C for 4 hours, and the casting is ultrasonically treated at the same time; the concentrations of copper chloride, nasturtium orange, and hydrochloric acid are 10g / L, 1mmol / L, and 6mol / L, respectively; the casting is taken out and repeatedly soaked in deionized water, then taken out again and repeatedly soaked in ionized water, and then placed in a 50wt% potassium hydroxide solution and boiled for 8 hours; the casting is alternately treated with alkali and acid solutions until the core is completely removed.

[0101] Comparative Example 11

[0102] A method for removing a silicon-based ceramic core for titanium alloy casting comprises the following steps:

[0103] A titanium alloy casting method is disclosed. A titanium alloy casting method is disclosed. A silicon-based ceramic core for titanium alloy casting is used as a template for titanium alloy simulation casting. The casting is immersed in a mixed solution containing 30wt% potassium hydroxide and 10wt% sodium fluoride and boiled for 8 hours at a natural atmospheric pressure, while ultrasonically treating the casting. The casting is taken out and repeatedly soaked in deionized water. The casting is then immersed in a hydrochloric acid solution containing copper chloride and nasturtium orange, kept warm at 90°C for 4 hours, while ultrasonically treating the casting. The concentrations of copper chloride, nasturtium orange, and hydrochloric acid are 10g / L, 1mmol / L, and 6mol / L, respectively. The casting is taken out and repeatedly soaked in deionized water, then taken out and repeatedly soaked in deionized water, and then placed in a mixed solution containing 30wt% potassium hydroxide and 10wt% sodium fluoride and boiled for 8 hours. The casting is alternately treated with alkali and acid solutions until the core is completely removed.

[0104] Comparative Example 12

[0105] A method for removing a silicon-based ceramic core for titanium alloy casting comprises the following steps:

[0106] A titanium alloy casting simulation is performed using a silicon-based ceramic core for titanium alloy casting as a template to obtain a casting; the casting is immersed in a mixed solution containing 50wt% potassium hydroxide and 10wt% sodium fluoride and boiled for 8 hours at a natural atmospheric pressure, and the casting is simultaneously subjected to ultrasound; the casting is taken out and repeatedly soaked in deionized water; the casting is then immersed in a hydrochloric acid solution containing copper chloride and nasturtium orange, kept warm at 90°C for 4 hours, and the casting is simultaneously subjected to ultrasound; the concentrations of copper chloride, nasturtium orange, and hydrochloric acid are 10g / L, 1mmol / L, and 3mol / L, respectively; the casting is taken out and repeatedly soaked in deionized water, and then immersed in a mixed solution of 50wt% potassium hydroxide and 10wt% sodium fluoride and boiled for 8 hours; the casting is alternately treated with alkali and acid solutions until the core is completely removed.

[0107] Comparative Example 13

[0108] A method for removing a silicon-based ceramic core for titanium alloy casting comprises the following steps:

[0109] A titanium alloy casting simulation is performed using a silicon-based ceramic core for titanium alloy casting as a template to obtain a casting; the casting is immersed in a mixed solution containing 50wt% potassium hydroxide and 10wt% sodium fluoride and boiled for 8 hours at a natural atmospheric pressure, and the casting is simultaneously subjected to ultrasound; the casting is taken out and repeatedly soaked in deionized water; the casting is then immersed in a hydrochloric acid solution containing copper chloride and nasturtium orange, kept warm at 90°C for 4 hours, and the casting is simultaneously subjected to ultrasound; the concentrations of copper chloride, nasturtium orange, and hydrochloric acid are 10g / L, 1mmol / L, and 8mol / L, respectively; the casting is taken out and repeatedly soaked in deionized water, and then immersed in a mixed solution of 50wt% potassium hydroxide and 10wt% sodium fluoride and boiled for 8 hours; the casting is alternately treated with alkali and acid solutions until the core is completely removed.

[0110] Comparative Example 14

[0111] A method for removing a silicon-based ceramic core for titanium alloy casting comprises the following steps:

[0112] A casting is obtained by simulating titanium alloy pouring using a silicon-based ceramic core for titanium alloy casting as a template; the casting is immersed in a mixed solution containing 50wt% potassium hydroxide and 10wt% sodium fluoride and boiled for 8 hours at a natural atmospheric pressure, and the casting is ultrasonically treated at the same time; the casting is taken out and repeatedly soaked in deionized water; the casting is then immersed in a 6mol / L hydrochloric acid solution and kept warm at 90°C for 4 hours, and the casting is ultrasonically treated at the same time; the casting is taken out and repeatedly soaked in deionized water, and then immersed in a mixed solution of 50wt% potassium hydroxide and 10wt% sodium fluoride and boiled for 8 hours; the casting is alternately treated with alkali and acid solutions until the core is completely removed.

[0113] Comparative Example 15

[0114] A method for removing a silicon-based ceramic core for titanium alloy casting comprises the following steps:

[0115] A titanium alloy casting simulation is performed using a silicon-based ceramic core for titanium alloy casting as a template to obtain a casting; the casting is immersed in a mixed solution containing 50wt% potassium hydroxide and 10wt% sodium fluoride and boiled for 8 hours at a natural atmospheric pressure; the casting is taken out and repeatedly soaked in deionized water; the casting is then immersed in a hydrochloric acid solution containing copper chloride and nasturtium orange and kept warm at 90°C for 4 hours; the concentrations of copper chloride, nasturtium orange and hydrochloric acid are 10g / L, 1mmol / L and 6mol / L, respectively; the casting is taken out and repeatedly soaked in deionized water, and then immersed in a mixed solution of 50wt% potassium hydroxide and 10wt% sodium fluoride and boiled for 8 hours; the casting is alternately treated with alkali and acid solutions until the core is completely removed.

[0116] The silicon-based ceramic cores and silicon-based ceramic cores for titanium alloy casting prepared in Examples 1-2 and Comparative Examples 1-9 were tested for their product expansion rate, open porosity, room temperature strength, high temperature strength, high temperature deflection, and inertness to reaction with titanium alloy. The results are shown in Table 1.

[0117] The silicon-based ceramic core for titanium alloy casting prepared in Example 2 was removed using the removal methods of Example 3 and Comparative Examples 10-15. The complete removal time of each group was recorded. The results are shown in Table 2:

[0118] Table 1

[0119]

[0120] Table 2

[0121]

[0122]

[0123] As shown in Table 1, Comparative Examples 1-7 differ only in the composition and content of the mineralizers compared to Example 1. The simultaneous addition of the three mineralizers significantly improves the room-temperature strength, high-temperature strength, and open porosity of the ceramic core. Comparative Examples 8-9, on the other hand, differ only in the coating thickness compared to Example 2. When the yttrium oxide coating is thicker than 100 μm, it effectively isolates the silicon-based ceramic core from the titanium alloy.

[0124] As can be seen from Table 2, the ceramic core can be effectively removed by combining alternating high-temperature immersion in alkali and acid solutions with ultrasonic dispersion. Increasing the concentration of potassium hydroxide and adding sodium fluoride can effectively shorten the core removal time. The use of a composite corrosion inhibitor can effectively inhibit the corrosion of titanium alloy by high-concentration hydrochloric acid.

[0125] To sum up, the ceramic core for titanium alloy casting prepared by the scheme of the present invention can not only improve the room temperature strength, high temperature strength and open porosity of the base ceramic core, but also significantly improve the chemical removal rate of the ceramic core, thereby solving the problem of core removal difficulties that has long plagued the ceramic core for titanium alloy casting from the source.

[0126] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned 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.

[0127] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A method for preparing a silicon-based ceramic core, characterized in that: The following steps are involved: The silicon dioxide, mullite, kaolin and yttrium oxide powders are mixed uniformly to obtain a mixed powder; a binder aqueous solution is then added and mixed uniformly; the mixture is then pressed to obtain a green body; the green body is dried and then sintered to obtain a silicon-based ceramic; and an yttrium oxide coating is sprayed on the surface of the silicon-based ceramic to obtain the silicon-based ceramic core. The mixed powder is composed of silicon dioxide, mullite, kaolin and yttrium oxide, and the mass ratio of silicon dioxide, mullite, kaolin and yttrium oxide is 15:2:1:2; the binder is polyvinyl alcohol; the mass ratio of the mixed powder to the binder is 1:0.01-0.05; The average particle size of the silicon dioxide is 25-40 μm; the average particle size of the mullite is 10-20 μm; the average particle size of the yttrium oxide is 5-15 μm; and the average particle size of the kaolin is 0.5-2 μm. The sintering temperature is 1250-1450℃.

2. The method for preparing a silicon-based ceramic core according to claim 1, wherein: The sintering holding time is 3-6h.

3. The method for preparing a silicon-based ceramic core according to claim 1, wherein: The concentration of the binder aqueous solution is 3-10 wt %.

4. The method for preparing a silicon-based ceramic core according to claim 1, wherein: The solid-to-liquid ratio of the mixed powder to the binder aqueous solution is 15-20 g:1-3 mL.

5. The method for preparing a silicon-based ceramic core according to any one of claims 1 to 4, characterized in that: The following steps are involved: S1, mixing the silica, mullite, kaolin and yttrium oxide, and fully drying them at a temperature of 100-120° C.; S2. ball-milling the fully dried raw materials to obtain a mixed powder; wherein the ball-to-material ratio is 2:1; S3, adding the binder aqueous solution to the mixed powder, mixing evenly and then passing through a 100-mesh sieve; wherein the solid-liquid ratio of the mixed powder to the binder aqueous solution is 15-20 g:1-3 mL; S4, taking the powder under the sieve and placing it in a mold for pressing at a pressure of 3-10 MPa and a holding time of 30-60 s to obtain a green body; S5, fully drying the green body at a temperature of 100-120° C.; S6, placing the dried green body in a muffle furnace and sintering it at a temperature of 1250-1450° C. to obtain the silicon-based ceramic; S7. Spraying an yttrium oxide coating on the surface of the silicon-based ceramic to obtain the silicon-based ceramic core.

6. A silicon-based ceramic core, characterized in that: The method is obtained by the preparation method according to any one of claims 1 to 5.

7. A method for removing silicon-based ceramic cores for titanium alloy casting, characterized in that: The following steps are involved: (1) Using the silicon-based ceramic core obtained by the preparation method according to any one of claims 1 to 5 as a template, titanium alloy is cast to obtain a casting; (2) The casting with the silicon-based ceramic core is placed in a mixed alkali solution and boiled while the casting is ultrasonically treated; (3) After the treatment in the mixed alkali solution is completed, the casting is taken out and soaked in water to remove the residual alkali solution; (4) immersing the casting treated in step (3) in a hydrochloric acid solution containing a corrosion inhibitor, reacting at a temperature of 80-100° C. while performing ultrasonic treatment; (5) Repeat steps (2) to (4) until the ceramic core is completely removed; Wherein, the mixed alkali solution comprises 30-60wt% potassium hydroxide and 5-15wt% sodium fluoride; The corrosion inhibitors are copper salt and tropaeolum; the concentration of the hydrochloric acid solution is ≤6 mol / L.

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