A ceramic core with enhanced orientation of core-shell structure and its preparation method

Abstract

The present invention relates to the technical field of ceramic powder metallurgy, and discloses a ceramic core with a core-shell structure and enhanced orientation and its preparation method. Specifically, it includes: preparing a composite powder with a refractory material powder as the core and a metal phase as the shell, adding the composite powder to a dispersant according to a proportion, achieving uniform dispersion of the composite powder through vacuum stirring, preparing a green body of the ceramic core by hot pressing injection, and applying a magnetic field at the injection port position of the mold to control the directional stacking arrangement of the composite powder. After the green body of the ceramic core is buried, the metal shell layer is oxidized during the high-temperature sintering process to form a ceramic core with a directional arrangement that resists crack propagation. The present invention solves the problem of poor mixing uniformity of the two powders, and at the same time, by introducing a magnetic field to control the composite powder in the molten mixture, the directional stacking arrangement of the composite powder is realized, improving the comprehensive performance of the ceramic core.

Description

Technical Field

[0001] The present invention relates to the technical field of ceramic powder metallurgy, and particularly relates to a ceramic core with a core-shell structure and enhanced orientation and a preparation method thereof. Background Art

[0002] The ceramic core is one of the core components for manufacturing the hollow blades of aeroengines, and its performance plays a crucial role in the manufacturing and performance of the hollow blades. With the development of highly efficient air-cooled blades, the internal structure of the blades is becoming increasingly complex, resulting in higher requirements for the structure and performance of the ceramic cores for manufacturing hollow blades. At present, the performance of some ceramic cores can no longer meet the requirements brought about by the development of the blades. Therefore, it is urgent to explore and develop new methods for strengthening ceramic cores.

[0003] The method for manufacturing ceramic cores mainly relies on hot die casting. By mixing ceramic powder with molten paraffin and injecting it into a metal mold under certain temperature and pressure conditions, and utilizing the property that paraffin solidifies as the temperature decreases, after the liquid mixture fills the mold and solidifies, a ceramic core with a complex shape can be obtained. The ceramic cores prepared by this method are widely used in the manufacturing of aeroengine blades. However, as mentioned above, the performance of ceramic cores needs to be continuously improved to meet the increasing performance requirements of hollow blades. Currently, in the hot die casting method, the performance of ceramic cores is mainly regulated from the perspective of composition optimization. For example, second-phase particles such as zirconium silicate, zirconia, yttrium oxide, and magnesium oxide are added. Research shows that these second-phase particles can effectively improve the mechanical properties of ceramic cores. There are also studies on strengthening the comprehensive performance of ceramic cores by adding second-phase fibers such as alumina fibers and zirconia fibers. However, these methods are still limited in terms of improving the performance of ceramic cores, and the introduction of fibers can easily cause fiber agglomeration, reducing the solid content of the mixture, and thus affecting the overall performance of the ceramic core. At the same time, it is also necessary to ensure that the ceramic core has a low shrinkage rate to ensure the high quality of the prepared hollow blades.

[0004] In addition, some studies have shown that by adding metal powders such as Al powder, through the oxidation process during the later sintering process, the shrinkage of the ceramic core can be effectively inhibited, and at the same time, the bonding strength between particles can be improved. While ensuring a low shrinkage rate of the ceramic core, the porosity and mechanical properties of the ceramic core can be improved. However, currently, this ceramic powder and metal powder are still mixed in molten paraffin by mechanical stirring, and their mixing uniformity is poor, seriously affecting the improvement of the overall performance of the ceramic core.

[0005] The existing patent CN113319271A discloses an oxide-coated powder with a core-shell structure and a preparation method and application thereof, wherein helium and argon are injected into a plasma generator to generate a helium-argon mixed plasma; the powder is mixed with the helium-argon mixed plasma and then injected into water for self-oxidation to obtain an oxide-coated powder with a core-shell structure. The present invention is conducive to achieving densification, homogenization, high bonding and strong matching of the oxide shell layer.

[0006] The existing patent CN103130508B discloses a method for preparing textured boride-based ultra-high temperature ceramics, which uses IVB group metal elements, amorphous boron powder, silicon powder and transition metals as raw materials to prepare a composite powder containing boride seeds and silicide particles; the obtained composite powder is mixed with boride ceramic powder to prepare a slurry, a ceramic green body is prepared by a casting process or a strong magnetic field orientation process, and the ceramic green body is hot-pressed and sintered, thereby preparing a textured boride-based ultra-high temperature ceramic with anisotropic grain morphology.

[0007] In summary, the above two existing patents are to completely solve the problem of poor mixing uniformity of ceramic powder and metal powder in the prior art and limited improvement of ceramic core performance. Summary of the invention

[0008] Based on the above technical problems, the present invention proposes a core-shell structure orientation-enhanced ceramic core and a preparation method thereof, which solves the problem of poor mixing uniformity of ceramic powder and metal powder in the prior art and limited improvement of the performance of the ceramic core.

[0009] To achieve the above-mentioned purpose, the present invention proposes a core-shell structure oriented reinforced ceramic core and a preparation method thereof. The specific technical scheme is as follows:

[0010] A method for preparing a core-shell structure oriented reinforced ceramic core, the preparation method specifically comprising the following steps:

[0011] S1. Preparation of a core-shell composite powder having a refractory core and a metal shell;

[0012] S2. Using a core-shell structure composite powder to form a ceramic core slurry;

[0013] S3. Preparing a ceramic core blank and applying a magnetic field to regulate the directional stacking arrangement of the core-shell structure composite powder;

[0014] S4. After the ceramic core blank is buried, it is sintered at high temperature to form a ceramic core.

[0015] Furthermore, in step S1, a core-shell structure composite powder having a refractory core and a metal shell is prepared by a spray drying process;

[0016] The air flow temperature in the spray drying process is 80 - 120 °C, and the air flow rate is 1 - 10 kg / h.

[0017] Further, in step S1, the raw material liquid is added into a spray dryer, and the raw material liquid is atomized into mist-like liquid droplets by a high-speed centrifugal atomizer and contacted with hot air in a co-current manner to be dried.

[0018] The solid content in the raw material liquid is 50 - 70%, the solid phase includes refractory powder and metal powder, the weight percentage of the refractory powder in the solid phase is 70 - 90%, and the weight percentage of the metal powder in the solid phase is 10 - 30%.

[0019] The refractory powder is quartz glass powder, alumina powder, calcium oxide powder or magnesium oxide powder, the particle size of the refractory powder is 1 - 60 μm, and the purity is not less than 99.95%.

[0020] The metal powder is aluminum powder, zirconium powder or copper powder.

[0021] Further, in step S2, the core-shell structured composite powder is added to a dispersant, and a uniformly mixed ceramic core mold slurry is obtained through vacuum stirring.

[0022] The dispersant is liquid paraffin, the temperature of the liquid paraffin is 70 - 95 °C, the rotation speed of the vacuum stirring is 50 - 200 rpm / min, the stirring time is 10 - 36 h, and the vacuum degree is 5×10 -2 -6×10 -2 Pa.

[0023] Further, the weight percentage of the core-shell structured composite powder in the ceramic core mold slurry is 50 - 70%.

[0024] Further, in step S3, the ceramic core mold slurry is placed into a core pressing machine, and a green body of the ceramic core is pressed by using a mold, and at the same time, a magnetic field is applied at the injection port position of the mold to regulate the directional stacking arrangement of the core-shell structured composite powder.

[0025] The forming pressure of the core pressing machine is 1 - 10 MPa, and the magnetic field intensity of the magnetic field is 0.1 - 2 T.

[0026] Further, the magnetic field intensity of the magnetic field is 0.8 - 1.2 T.

[0027] Further, in step S4, after the green body of the ceramic core is buried in powder, it is sintered at a high temperature to form a ceramic core.

[0028] The heating process of the high-temperature sintering includes multiple stages. The temperature increase amplitude of each stage is 200 - 400 °C, the heating rate of each stage is 3 - 10 °C / min, and the heat preservation time after heating in each stage is 3 - 10 h;

[0029] The final sintering temperature in the high-temperature sintering is 1000 - 1600 °C.

[0030] Further, the multiple stages include: the first stage from room temperature to 200 °C, with a heating rate of 3 °C / min, heat preservation at 200 °C for 3 h; the second stage from 200 °C to 400 °C, with a heating rate of 3 °C / min, heat preservation at 400 °C for 3 h; the third stage from 400 °C to 600 °C, with a heating rate of 3 °C / min, heat preservation at 600 °C for 8 h; the fourth stage from 600 °C to 900 °C, with a heating rate of 5 °C / min, heat preservation at 900 °C for 8 h; and finally from 900 °C to 1200 °C, with a heating rate of 5 °C / min and heat preservation for 10 h.

[0031] The present invention also provides a ceramic core with enhanced orientation of the core-shell structure, which is prepared by using the preparation method of the ceramic core with enhanced orientation of the core-shell structure as described above.

[0032] Based on the above technical solutions, the present invention has at least the following beneficial effects:

[0033] 1. The present invention provides a ceramic core with enhanced orientation of the core-shell structure and its preparation method. By means of the spray drying process, a core-shell structure composite powder with a refractory material powder as the core and a metal as the shell is prepared, solving the problem of poor mixing uniformity of the two powders.

[0034] 2. The present invention provides a ceramic core with enhanced orientation of the core-shell structure and its preparation method. Before injecting the molten mixture into the metal mold, by introducing a magnetic field to regulate the core-shell structure composite powder in the molten mixture, the directional stacking arrangement of the core-shell structure composite powder is realized. Then, through the oxidation of the metal shell layer during the later sintering process, a ceramic core for resisting crack propagation with a directional arrangement is formed, improving its comprehensive performance.

[0035] 3. The present invention provides a ceramic core with enhanced orientation of the core-shell structure and its preparation method. The preparation process is simple, can effectively realize the directional stacking arrangement of the core-shell structure composite powder, and has an excellent strengthening effect on the performance of the core.

[0036] 4. The present invention provides a ceramic core with enhanced orientation of the core-shell structure and its preparation method, significantly enhancing the room temperature and high temperature bending strength and high temperature creep resistance of the ceramic core, and can be applied to the development and application of ceramic cores in other systems. Specific embodiments

[0037] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other. The present invention will be described in detail below in conjunction with the embodiments.

[0038] The following further describes the present invention in detail with specific embodiments, and these embodiments should not be construed as limiting the scope claimed by the present invention.

[0039] To solve the problems of poor mixing uniformity of ceramic powder and metal powder in the prior art and limited improvement in the performance of ceramic cores, the present invention proposes a ceramic core with magnetically controlled core-shell structure orientation enhancement and its preparation method.

[0040] To achieve the above object, the present invention proposes a ceramic core with magnetically controlled core-shell structure orientation enhancement and its preparation method. The preparation method of a ceramic core with magnetically controlled core-shell structure orientation enhancement specifically includes the following steps:

[0041] S1. Prepare a core-shell structure composite powder with a refractory material as the core and a metal as the shell;

[0042] Specifically, use the spray drying process to prepare a core-shell structure composite powder with a refractory material as the core and a metal as the shell. In the spray drying process, the drying air flow temperature is 80 - 120 °C, and the air flow rate is 1 - 10 kg / h; the solid-phase composition content in the raw material liquid is 50 - 70%, the weight percentage of the refractory powder in the solid phase is 70 - 90%, and the weight percentage of the metal powder in the solid phase is 10 - 30%.

[0043] The above-mentioned refractory powder is one of quartz glass powder, alumina powder, calcium oxide powder or magnesium oxide powder, and the particle size of the refractory powder is 1 - 60 μm, and the purity ≥ 99.95%; the above-mentioned metal powder is one of aluminum powder, zirconium powder or copper powder.

[0044] S2. Add the core-shell structure composite powder to liquid paraffin in proportion and disperse it evenly;

[0045] Specifically, weigh the core-shell structure composite powder in proportion, dry it and then add it to liquid paraffin, and achieve uniform dispersion of the composite powder in paraffin through vacuum stirring to obtain a uniformly mixed ceramic core slurry. Among them, the weight percentage of the core-shell structure composite powder in the ceramic core slurry is 50 - 70%, the vacuum stirring speed is 50 - 200 rpm / min, the stirring time is 10 - 36 h, the temperature of paraffin is 70 - 95 °C, and the vacuum degree is 5×10 -2 -6×10 -2 Pa.

[0046] S3. Prepare a green body of the ceramic core, and at the same time apply a magnetic field to control the directional stacking arrangement of the core-shell structure composite powder;

[0047] Specifically, a green body of the ceramic core is prepared by a hot pressing injection method. The ceramic core slurry is placed in a core pressing machine, and the green body of the ceramic core is pressed using a mold. Meanwhile, a magnetic field is applied at the injection port of the mold to control the directional stacking arrangement of the core-shell structure composite powder. Among them, the hot die casting forming pressure is 1-10 MPa, and the applied magnetic field strength is 0.1-2 T.

[0048] S4. After the green body of the ceramic core is buried, it is sintered at high temperature to form a ceramic core.

[0049] Specifically, after the green body of the ceramic core is buried using alumina powder as a filler, through the oxidation of the metal shell layer during the high-temperature sintering process, a ceramic core that resists crack propagation with a directional arrangement is formed. The final sintering temperature in the high-temperature sintering is 1000-1600 °C. The heating process in the high-temperature sintering includes multiple stages. The heating rate in each stage is 200-400 °C, the heating speed in each stage is 3-10 °C / min, and the holding time after heating in each stage is 3-10 h.

[0050] The following further illustrates the preparation method of the above-mentioned ceramic core with enhanced core-shell structure orientation in combination with specific implementation data.

[0051] Example 1

[0052] S1. A core-shell structure composite powder with a core of zirconia and a shell of zirconium is prepared by a spray drying process. The drying air flow temperature is 100 °C, and the air flow rate is 5 kg / h. The solid-phase composition content in the raw material liquid is 50%, the weight percentage of zirconia powder in the solid phase is 90%, and the weight percentage of zirconium powder in the solid phase is 10%.

[0053] S2. Weigh 50% of the core-shell structure composite powder by weight percentage, dry the composite powder for 12 h at a drying temperature of 120 °C, and then place it in a mixer with melted paraffin. After vacuum stirring, sufficient mixing is achieved. The mixing temperature is 90 °C, the vacuum degree is 5×10 -2 Pa, and the stirring time is 8 h to obtain a uniformly mixed ceramic core slurry.

[0054] S3. Place the ceramic core slurry in a core pressing machine, and use a mold to press the green body of the ceramic core. The pressing pressure is 5 MPa, and a magnetic field of 0.1 T is applied at the injection port during the pressing process to obtain a green body of the ceramic core with a directional arrangement of the core-shell structure.

[0055] S4. After filling the green core with alumina filler, sinter it. In the first stage, from room temperature to 200 °C, the heating rate is 3 °C / min, and keep it at 200 °C for 3 h; in the second stage, from 200 °C to 500 °C, the heating rate is 3 °C / min, and keep it at 500 °C for 3 h; in the third stage, from 500 °C to 800 °C, the heating rate is 3 °C / min, and keep it at 800 °C for 5 h; in the fourth stage, from 800 °C to 1200 °C, the heating rate is 5 °C / min, and keep it at 1200 °C for 5 h; finally, raise the temperature from 1200 °C to 1600 °C, the heating rate is 5 °C / min, and keep it for 8 h, and finally obtain a ceramic core with oriented arrangement and crack propagation resistance.

[0056] The flexural strength of the ceramic core in this example at room temperature is 52 MPa, the flexural strength at 1550 °C is 58 MPa, and the deflection at 1550 °C is 1.18 mm.

[0057] Example 2

[0058] S1. Prepare a core-shell structured composite powder with alumina as the core and copper as the shell through a spray drying process. The drying gas flow temperature is 100 °C, and the gas flow rate is 5 kg / h; the solid-phase composition content in the raw material liquid is 65%, the weight percentage of alumina powder in the solid phase is 88%, and the weight percentage of copper powder in the solid phase is 12%.

[0059] S2. Weigh 65% of the core-shell structured composite powder by weight percentage, dry the composite powder for 12 h at a drying temperature of 120 °C, then place it in a mixer with melted paraffin, and achieve full mixing through vacuum stirring. The mixing temperature is 90 °C, the vacuum degree is 5×10 -2 Pa, and the stirring time is 8 h to obtain a uniformly mixed ceramic core slurry.

[0060] S3. Place the ceramic core slurry into a core pressing machine, and use a mold to press the green ceramic core. The pressing pressure is 5 MPa, and apply a 1 T magnetic field at the injection port position during the pressing process to obtain a green ceramic core with oriented arrangement of the core-shell structure.

[0061] S4. After filling the green core with alumina filler, sinter it. In the first stage, from room temperature to 200 °C, the heating rate is 3 °C / min, and keep it at 200 °C for 3 h; in the second stage, from 200 °C to 400 °C, the heating rate is 3 °C / min, and keep it at 400 °C for 3 h; in the third stage, from 400 °C to 700 °C, the heating rate is 3 °C / min, and keep it at 700 °C for 5 h; in the fourth stage, from 700 °C to 1100 °C, the heating rate is 5 °C / min, and keep it at 1100 °C for 6 h; finally, raise the temperature from 1100 °C to 1500 °C, the heating rate is 8 °C / min, and keep it for 8 h, and finally obtain a ceramic core with oriented arrangement and crack propagation resistance.

[0062] The bending strength of the ceramic core in this embodiment at room temperature is 59 MPa, the bending strength at 1550 °C is 73 MPa, and the deflection at 1550 °C is 1.08 mm.

[0063] Example 3

[0064] S1. Prepare a core-shell structure composite powder with a core of magnesium oxide and a shell of aluminum through a spray drying process. The drying air flow temperature is 100 °C, and the air flow rate is 5 kg / h; the solid-phase composition content in the raw material liquid is 70%, the weight percentage of magnesium oxide powder in the solid phase is 70%, and the weight percentage of aluminum powder in the solid phase is 30%.

[0065] S2. Weigh 55% of the core-shell structure composite powder by weight percentage, dry the composite powder for 12 h at a drying temperature of 120 °C, then place it in a mixer where the paraffin has melted, and achieve full mixing through vacuum stirring. The mixing temperature is 90 °C, the vacuum degree is 5×10 -2 Pa, and the stirring time is 8 h to obtain a uniformly mixed ceramic slurry.

[0066] S3. Place the taken-out ceramic core slurry into a core pressing machine, and use a mold to press the green body of the ceramic core. The pressing pressure is 7 MPa, and a 2T magnetic field is applied at the injection port position during the pressing process to obtain a green body of the ceramic core with a core-shell structure arranged in an oriented manner.

[0067] S4. Use alumina filler to bury the green body of the core and sinter it. According to the first stage from room temperature to 200 °C, the heating rate is 3 °C / min, and it is held at 200 °C for 3 h; the second stage from 200 °C to 400 °C, the heating rate is 3 °C / min, and it is held at 400 °C for 3 h; the third stage from 400 °C to 650 °C, the heating rate is 3 °C / min, and it is held at 650 °C for 5 h; the fourth stage from 650 °C to 1000 °C, the heating rate is 5 °C / min, and it is held at 1000 °C for 6 h; finally, it is heated from 1000 °C to 1400 °C at a heating rate of 5 °C / min and held for 8 h to finally obtain an oriented ceramic core that resists crack propagation.

[0068] The bending strength of the ceramic core in this embodiment at room temperature is 53 MPa, the bending strength at 1550 °C is 55 MPa, and the deflection at 1550 °C is 1.08 mm.

[0069] Example 4

[0070] S1. Prepare a core-shell structured composite powder with a quartz glass core and an aluminum shell through a spray drying process. The solid-phase composition content in the raw material liquid is 50%. The weight percentage of quartz glass powder in the solid phase is 80%, and the weight percentage of aluminum powder in the solid phase is 20%. The drying air flow temperature is 100 °C, and the air flow rate is 5 kg / h.

[0071] S2. Weigh 60% of the core-shell structured composite powder by weight percentage. Dry the composite powder for 12 h at a drying temperature of 120 °C. Then add it to a mixer where the paraffin has melted. Achieve sufficient mixing of the composite powder and paraffin through vacuum stirring. The paraffin temperature is 90 °C, the vacuum stirring speed is 100 rpm / min, the stirring time is 8 h, and the vacuum degree is 5×10 -2 Pa to obtain a uniformly mixed ceramic slurry.

[0072] S3. Place the ceramic core slurry into a core pressing machine and use a mold to press the green body of the ceramic core. The pressing pressure is 5 MPa. Apply a 0.8 T magnetic field at the injection port position of the mold during the pressing process to obtain a green body of the ceramic core with a core-shell structure arranged directionally.

[0073] S4. Use alumina filler to bury the green body of the ceramic core and then conduct high-temperature sintering. According to the first stage from room temperature to 200 °C, the heating rate is 3 °C / min, and keep it at 200 °C for 3 h; the second stage from 200 °C to 400 °C, the heating rate is 3 °C / min, and keep it at 400 °C for 3 h; the third stage from 400 °C to 600 °C, the heating rate is 3 °C / min, and keep it at 600 °C for 8 h; the fourth stage from 600 °C to 900 °C, the heating rate is 5 °C / min, and keep it at 900 °C for 8 h; finally, raise the temperature from 900 °C to 1200 °C at a heating rate of 5 °C / min and keep it for 10 h to finally obtain a ceramic core with a directional arrangement that resists crack propagation.

[0074] The flexural strength of the ceramic core in this example at room temperature is 56 MPa, the flexural strength at 1550 °C is 69 MPa, and the deflection at 1550 °C is 0.87 mm.

[0075] Example 5

[0076] S1. Prepare a core-shell structured composite powder with a quartz glass core and a zircon shell through a spray drying process. The drying air flow temperature is 100 °C, and the air flow rate is 5 kg / h. The solid-phase composition content in the raw material liquid is 60%. The weight percentage of quartz glass powder in the solid phase is 85%, and the weight percentage of zircon powder in the solid phase is 15%.

[0077] S2. Weigh 70% of the core-shell structured composite powder by weight percentage, dry the composite powder for 12 h at a drying temperature of 120 °C, then place it in a mixer with melted paraffin, and achieve full mixing through vacuum stirring. The mixing temperature is 90 °C, the vacuum degree is 5×10 -2 Pa, and the stirring time is 8 h to obtain a uniformly mixed ceramic core paste;

[0078] S3. Place the ceramic core paste into a core pressing machine, and use a mold to press the green body of the ceramic core. The pressing pressure is 8 MPa, and a magnetic field of 1.2 T is applied at the injection port position during the pressing process to obtain a green body of the ceramic core with the core-shell structure arranged directionally;

[0079] S4. Use alumina filler to bury the green body of the core and then sinter it. According to the first stage from room temperature to 200 °C, the heating rate is 3 °C / min, and keep it at 200 °C for 3 h; the second stage from 200 °C to 500 °C, the heating rate is 3 °C / min, and keep it at 500 °C for 3 h; the third stage from 500 °C to 800 °C, the heating rate is 3 °C / min, and keep it at 800 °C for 5 h; the fourth stage from 800 °C to 1200 °C, the heating rate is 5 °C / min, and keep it at 1200 °C for 5 h; finally, raise the temperature from 1200 °C to 1600 °C, the heating rate is 5 °C / min, and keep it at this temperature for 6 h to finally obtain a ceramic core with directional arrangement and resistance to crack propagation.

[0080] The flexural strength of the ceramic core in this embodiment at room temperature is 55 MPa, the flexural strength at 1550 °C is 72 MPa, and the deflection at 1550 °C is 0.65 mm.

[0081] Comparative Example 1

[0082] S1. Prepare a core-shell structured composite powder with a core of quartz glass and a shell of aluminum through a spray drying process. The drying gas flow temperature is 100 °C, and the gas flow rate is 5 kg / h; the content range of the solid-phase composition in the raw material liquid is 50%, the weight percentage of quartz glass powder in the solid phase is 80%, and the weight percentage of aluminum powder in the solid phase is 20%;

[0083] S2. Weigh 60% of the core-shell structured composite powder by weight percentage, dry the composite powder for 12 h at a drying temperature of 120 °C, then place it in a mixer with melted paraffin, and achieve full mixing through vacuum stirring. The mixing temperature is 90 °C, the vacuum degree is 5×10 -2 Pa, and the stirring time is 8 h to obtain a uniformly mixed ceramic paste;

[0084] S3. Place the taken-out paste into a core pressing machine, and use a mold to press the green body of the core. The pressing pressure is 5 MPa;

[0085] S4. After filling the green body of the ceramic core with alumina filler, sinter it. In the first stage, from room temperature to 200 °C, the heating rate is 3 °C / min, and hold at 200 °C for 3 h; in the second stage, from 200 °C to 400 °C, the heating rate is 3 °C / min, and hold at 400 °C for 3 h; in the third stage, from 400 °C to 600 °C, the heating rate is 3 °C / min, and hold at 600 °C for 8 h; in the fourth stage, from 600 °C to 900 °C, the heating rate is 5 °C / min, and hold at 900 °C for 8 h; finally, raise the temperature from 900 °C to 1200 °C at a heating rate of 5 °C / min and hold for 10 h to finally obtain the ceramic core.

[0086] The flexural strength of the ceramic core in Comparative Example 1 at room temperature is 20 MPa, the flexural strength at 1550 °C is 36 MPa, and the deflection at 1550 °C is 1.87 mm.

[0087] Comparative Example 2

[0088] S1. Prepare a core-shell structured composite powder with alumina as the core and aluminum as the shell through a spray drying process. The drying air flow temperature is 100 °C, and the air flow rate is 5 kg / h; the solid composition content in the raw material liquid is 50%, the weight percentage of alumina powder in the solid phase is 80%, and the weight percentage of aluminum powder in the solid phase is 20%.

[0089] S2. Weigh 60% of the core-shell structured composite powder by weight percentage, dry the composite powder for 12 h at a drying temperature of 120 °C, then place it in a mixer with melted paraffin, and achieve full mixing through vacuum stirring. The mixing temperature is 90 °C, the vacuum degree is 5×10 -2 Pa, and the stirring time is 8 h to obtain a uniformly mixed ceramic slurry.

[0090] S3. Place the ceramic core slurry into a core pressing machine and use a mold to press the green body of the ceramic core. The pressing pressure is 5 MPa.

[0091] S4. After filling the green body of the ceramic core with alumina filler, sinter it. In the first stage, from room temperature to 200 °C, the heating rate is 3 °C / min, and hold at 200 °C for 3 h; in the second stage, from 200 °C to 400 °C, the heating rate is 3 °C / min, and hold at 400 °C for 3 h; in the third stage, from 400 °C to 600 °C, the heating rate is 3 °C / min, and hold at 600 °C for 8 h; in the fourth stage, from 600 °C to 900 °C, the heating rate is 5 °C / min, and hold at 900 °C for 8 h; finally, raise the temperature from 900 °C to 1600 °C at a heating rate of 5 °C / min and hold for 10 h to finally obtain the ceramic core.

[0092] The flexural strength of the ceramic core in Comparative Example 2 at room temperature is 35 MPa, the flexural strength at 1550 °C is 42 MPa, and the deflection at 1550 °C is 1.52 mm.

[0093] Compared with the results of Comparative Examples 1-2, for the ceramic cores prepared by the method of the present invention, the flexural strengths at room temperature and high temperature and the high-temperature creep resistance are all greater than those in the comparative examples, and the performance is significantly improved.

[0094] In some other embodiments, a core-shell structured composite powder with a core of zirconia and a shell of zirconium is prepared. The solid-phase composition content in the raw material liquid is 60% or 70%, the weight percentage of zirconia powder in the solid phase is 70% or 80%, and the corresponding weight percentage of zirconium powder in the solid phase is 30% or 20%;

[0095] In some other embodiments, a core-shell structured composite powder with a core of alumina and a shell of copper is prepared. The solid-phase composition content in the raw material liquid is 50% or 70%, the weight percentage of alumina powder in the solid phase is 70% or 90%, and the corresponding weight percentage of copper powder in the solid phase is 30% or 10%;

[0096] In some other embodiments, a core-shell structured composite powder with a core of magnesia and a shell of aluminum is prepared. The solid-phase composition content in the raw material liquid is 50% or 70%, the weight percentage of magnesia powder in the solid phase is 70% or 90%, and the corresponding weight percentage of aluminum powder in the solid phase is 30% or 10%;

[0097] In some other embodiments, a core-shell structured composite powder with a core of fused silica and a shell of aluminum is prepared. The solid-phase composition content in the raw material liquid is 60% or 70%, the weight percentage of fused silica powder in the solid phase is 70% or 90%, and the corresponding weight percentage of aluminum powder in the solid phase is 30% or 10%;

[0098] In some other embodiments, a core-shell structured composite powder with a core of fused silica and a shell of zirconium is prepared. The solid-phase composition content in the raw material liquid is 50% or 70%, the weight percentage of fused silica powder in the solid phase is 70% or 90%, and the corresponding weight percentage of zirconium powder in the solid phase is 30% or 10%;

[0099] Using the above composite powders can also achieve the technical effect that the flexural strengths at room temperature and high temperature and the high-temperature creep resistance of the ceramic core are superior to those of the comparative examples.

[0100] In some other embodiments, core-shell structured composite powders are prepared, including those with a quartz glass core and a copper shell, an alumina core and an aluminum shell, an alumina core and a zirconium shell, a magnesia core and a copper shell, a magnesia core and a zirconium shell, a calcium oxide core and a copper shell, and a calcium oxide core and an aluminum shell. In all these cases, the solid-phase composition content in the raw material liquid is 50 - 70%, the weight percentage of ceramic powder in the solid phase is 70 - 90%, and the weight percentage of metal powder in the solid phase is 10 - 30%.

[0101] Using the above composite powders can also achieve the technical effect that the room-temperature and high-temperature flexural strength and high-temperature creep resistance of the ceramic core are superior to those of the comparative example.

[0102] Through the orientation arrangement of the core-shell structured composite powder with a ceramic powder core and a metal-phase shell achieved by the present invention through a magnetic field, the room-temperature and high-temperature flexural strength and high-temperature creep resistance of the ceramic core are significantly enhanced, and the comprehensive performance of the core is improved. At the same time, the present invention can be applied to the development and application of ceramic cores in other systems.

[0103] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

[0104] It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or further includes elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "including a..." does not exclude the existence of additional identical elements in the process, method, article or device including the element.

[0105] It should be noted that in the description of this specification, the descriptions referring to the reference terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples", etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

Claims

1. A preparation method of a ceramic core with enhanced core-shell structure orientation, characterized in that, The preparation method specifically includes the following steps: S1. Prepare a core-shell structured composite powder with a refractory material as the core and a metal as the shell; S2. Use the core-shell structured composite powder to form a ceramic core paste; S3. Prepare a green body of the ceramic core, and at the same time apply a magnetic field to regulate the directional packing arrangement of the core-shell structured composite powder; S4. After burying the green body of the ceramic core, form the ceramic core through high-temperature sintering; In step S1, a core-shell structured composite powder with a refractory material as the core and a metal as the shell is prepared by a spray drying process. The raw material liquid is added to a spray dryer, and the raw material liquid is atomized into mist-like liquid droplets by a high-speed centrifugal atomizer and contacted with hot air in a parallel flow to be dried; The solid content in the raw material liquid is 50-70%, the solid phase includes a refractory powder and a metal powder, the weight percentage of the refractory powder in the solid phase is 70-90%, and the weight percentage of the metal powder in the solid phase is 10-30%; The refractory powder is alumina powder, calcium oxide powder or magnesium oxide powder, the particle size of the refractory powder is 1-60 μm, and the purity is not less than 99.95%. The metal powder is aluminum powder, zirconium powder or copper powder; In step S3, the magnetic field strength of the magnetic field is 0.1-2T.

2. The preparation method of the ceramic core with enhanced core-shell structure orientation according to claim 1, characterized in that: In step S1, the air flow temperature in the spray drying process is 80-120 °C, and the air flow rate is 1-10 kg / h.

3. The preparation method of the ceramic core with enhanced core-shell structure orientation according to claim 1, characterized in that, In step S2, the core-shell structured composite powder is added to a dispersant, and a uniformly mixed ceramic core paste is obtained through vacuum stirring; The dispersant is liquid paraffin, the temperature of the liquid paraffin is 70 - 95 °C, the rotation speed of the vacuum stirring is 50 - 200 rpm / min, the stirring time is 10 - 36 h, and the vacuum degree is 5×10 -2 -6×10 -2 Pa.

4. The preparation method of the ceramic core with enhanced core-shell structure orientation according to claim 3, characterized in that, The weight percentage of the core-shell structured composite powder in the ceramic core paste is 50-70%.

5. The preparation method of the ceramic core with enhanced core-shell structure orientation according to claim 1, characterized in that In step S3, the ceramic core paste is placed in a core pressing machine, and a green body of the ceramic core is pressed by using a mold. At the same time, a magnetic field is applied at the injection port position of the mold to regulate the directional packing arrangement of the core-shell structured composite powder; the forming pressure of the core pressing machine is 1-10 MPa.

6. The preparation method of the ceramic core with enhanced core-shell structure orientation according to claim 5, characterized in that: The magnetic field strength of the magnetic field is 0.8-1.2T.

7. The preparation method of the ceramic core with enhanced core-shell structure orientation according to claim 1, characterized in that In step S4, after burying the green body of the ceramic core with powder, the ceramic core is formed through high-temperature sintering; The final sintering temperature in the high-temperature sintering is 1000-1600 °C. The heating process of the high-temperature sintering includes multiple stages. The heating rate of each stage is 200-400 °C, the heating rate of each stage is 3-10 °C / min, and the holding time after heating in each stage is 3-10 h.

8. The preparation method of the ceramic core with enhanced core-shell structure orientation according to claim 7, characterized in that, The multiple stages include: the first stage from room temperature to 200 °C, the heating rate is 3 °C / min, and it is held at 200 °C for 3 h. The second stage from 200 °C to 400 °C, the heating rate is 3 °C / min, and it is held at 400 °C for 5 h. The third stage from 400 °C to 600 °C, the heating rate is 5 °C / min, and it is held at 600 °C for 8 h. The fourth stage from 600 °C to 900 °C, the heating rate is 8 °C / min, and it is held at 900 °C for 8 h. Finally, it is heated from 900 °C to 1200 °C, the heating rate is 10 °C / min, and it is held for 10 h.

9. A ceramic core with enhanced orientation of core-shell structure, characterized in that: The ceramic core is prepared by using the preparation method of the ceramic core with enhanced core-shell structure orientation as described in any one of claims 1-8.