CN112062587A - Preparation method of silicon-based ceramic core reinforced by in-situ authigenic mullite whiskers - Google Patents
Preparation method of silicon-based ceramic core reinforced by in-situ authigenic mullite whiskers Download PDFInfo
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Abstract
A method for preparing an in-situ authigenic mullite whisker reinforced silicon-based ceramic core comprises the steps of putting semi-refined paraffin wax, beeswax, polyethylene and oleic acid into a vacuum wax kettle, stirring and melting, then adding quartz glass powder, aluminum hydroxide powder, aluminum trifluoride powder and zirconium silicate powder, further stirring in vacuum, pouring out, and cooling to form a material ingot; adding the material ingot into a core pressing machine, and then performing melt pressing to obtain a ceramic core biscuit, wherein aluminum hydroxide and silicon dioxide in quartz glass powder are subjected to mullite treatment under the catalysis of aluminum trifluoride powder to generate mullite whiskers; embedding the ceramic core biscuit in light magnesium oxide powder, and sintering in four stages to obtain a ceramic core; and then the ceramic core is subjected to strengthening treatment to obtain a final ceramic core finished product. The invention can remarkably improve the high-temperature creep resistance of the silicon-based ceramic core and simultaneously keep good alkali liquor dissolution and depoling performances.
Description
Technical Field
The invention relates to a technology in the field of investment casting, in particular to a preparation method of an in-situ authigenic mullite whisker reinforced silicon-based ceramic core.
Background
The hollow turbine blade is a core part of an aeroengine and a gas turbine, and the interior of the hollow turbine blade contains a complex cooling flow passage structure. In the process of directional solidification of the hollow turbine blade, the ceramic core is required to bear the impact and soaking of molten metal and high temperature gradient, cracking and deformation cannot occur, and the working conditions of the ceramic core are very harsh. For many years, the preparation and performance improvement of ceramic cores have been leading edges and hot spots in the field of precision casting.
Silica-based cores based on quartz glass and aluminum-based cores based on alumina are currently two major ceramic cores. Among them, the silica-based cores are easily dissolved in alkali solution and thus are more easily removed from the hollow blades than the aluminum-based cores, but have lower refractoriness and poorer high-temperature creep resistance, and thus are generally used for casting high-temperature alloy hollow blades below 1550 ℃. In recent years, researchers have improved the high-temperature mechanical properties of silicon-based ceramic cores by adding reinforcing phases such as ceramic fibers and whiskers to a ceramic matrix. The composite of the reinforcing phase and the ceramic powder usually adopts a ball milling blending mode, the mechanical force in the ball milling process is easy to cause the breakage of the reinforcing phase such as fiber and the like, and simultaneously the reinforcing phase and the ceramic powder are easy to be entangled together due to electrostatic attraction.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides the preparation method of the silicon-based ceramic core reinforced by the in-situ authigenic mullite whiskers, which can remarkably improve the high-temperature creep resistance of the silicon-based ceramic core and simultaneously keep good alkali liquor dissolution and decoring performances.
The invention is realized by the following technical scheme:
the invention relates to a preparation method of an in-situ authigenic mullite whisker reinforced silicon-based ceramic core, which comprises the steps of putting semi-refined paraffin wax, beeswax, polyethylene and oleic acid into a vacuum wax kettle, stirring and melting the semi-refined paraffin wax, the beeswax, the polyethylene and the oleic acid, then adding quartz glass powder, aluminum hydroxide powder, aluminum trifluoride powder and zirconium silicate powder, further carrying out vacuum stirring, pouring out, and cooling to form a material ingot; adding the material ingot into a core pressing machine, and then performing melt pressing to obtain a ceramic core biscuit, wherein aluminum hydroxide and silicon dioxide in quartz glass powder are subjected to mullite treatment under the catalysis of aluminum trifluoride powder to generate mullite whiskers; embedding the ceramic core biscuit in light magnesium oxide powder, and sintering in four stages to obtain a ceramic core; and then the ceramic core is subjected to strengthening treatment to obtain a final ceramic core finished product.
The method comprises the following steps of: 70-80% of quartz glass powder, 5-15% of aluminum hydroxide powder, 1-3% of aluminum trifluoride powder, 5-7% of zirconium silicate powder, 4-8% of semi-refined paraffin, 0.1-0.5% of beeswax, 0.1-0.5% of polyethylene and 0.2-0.6% of oleic acid.
The particle size distribution of the quartz glass powder is 1-60 mu m, and the purity is more than or equal to 99.5 wt.%;
the particle size distribution of the aluminum hydroxide is 0.1-2 mu m, and the purity is more than or equal to 99 wt.%;
the particle size distribution of the aluminum trifluoride powder is 1-60 mu m, and the purity is more than or equal to 99 wt.%;
the particle size distribution of the zirconium silicate powder is 1-38 mu m, and the purity is more than or equal to 99 wt.%;
the semi-refined paraffin, the beeswax, the polyethylene and the oleic acid are all industrial products.
The quartz glass powder, the aluminum hydroxide powder, the aluminum trifluoride powder and the zirconium silicate powder are preferably dried before being mixed, and specifically comprise the following components: drying in air at 150 deg.C for 24 h.
The stirring speed is 120r/min, the temperature is 130 ℃, and the vacuum degree is 6 multiplied by 10-2Pa, and the stirring time is 1-12 h.
The vacuum stirring is preferably carried out at the stirring speed of 120r/min, the temperature of 130 ℃ and the vacuum degree of 6 multiplied by 10-2Pa, and the stirring time is 1-12 h.
The four-stage sintering is carried out by raising the temperature from room temperature to 1180-1220 ℃, and specifically comprises the following steps: in the first stage, the room temperature is between 300 ℃ and 30 ℃/h, and the temperature is kept at 300 ℃ for 2 to 4 h; in the second stage, the temperature is 300-600 ℃, the heating rate is 30 ℃/h, and the temperature is kept at 600 ℃ for 4-6 h; in the third stage, the temperature is 600-950 ℃, the heating rate is 30 ℃/h, and the temperature is kept at 950 ℃ for 6-8 h; in the fourth stage, the temperature is 900 ℃ to the highest sintering temperature, the heating rate is 30 ℃/h, and the temperature is kept for 4-6h at the highest sintering temperature.
The ceramic core sintered body is preferably further subjected to strengthening treatment, namely soaking in ethyl silicate hydrolysate and heating.
The preferable component formula of the ethyl silicate hydrolysate comprises the following components in percentage by weight: 31.3% of ethyl silicate, 28% of absolute ethyl alcohol, 1.5% of isopropanol, 13% of propylene glycol methyl ether and acidic silica sol (pH value is 2-3, SiO)2Content 25-28%) 25.8%, aqueous hydrochloric acid (20-20.2 wt.%) 0.4%.
And soaking, preferably soaking the core in ethyl silicate hydrolysate for 6 hours under a vacuum condition.
The heating is carried out for 12 hours in the air at 150 ℃.
The invention relates to a silicon-based ceramic core prepared by the method, which has the main performance indexes that: the room temperature bending strength is 26.8-31.2MPa, the bending strength at 1550 ℃ is 21.4-24.5MPa, the deflection at 1550 ℃ is 0.69-0.79mm, and the porosity is 27.8-34.5%.
Technical effects
Because aluminum hydroxide in the core biscuit can be decomposed to form gamma-Al at the temperature of about 300 DEG C2O3At about 950 ℃ with SiO in the quartz body2Chemical reaction is carried out to generate mullite crystal nucleus 3Al2O3·2SiO2The growth and development of mullite nuclei at higher temperatures during which AlF3The mullite crystal nucleus is promoted to grow along the c-axis direction under the action of a generated gas phase, so that the mullite crystal nucleus axially grows into the crystal whisker, the mullite crystal whisker formed by the in-situ reaction is tightly combined with other substances, the high-temperature strength and the high-temperature creep resistance of the ceramic core are obviously improved, and the dimensional stability of the core is improved. Meanwhile, the additives adopted in the invention are all powder raw materials, so that the flowing and filling performances of the quartz glass slurry are not damaged.
The invention integrally solves the problems that the existing ceramic core can not bear the high temperature of 1550 ℃ in the directional solidification process of the high-temperature alloy hollow blade and is easy to crack under the directional solidification high-temperature gradient.
Compared with the prior art, the blade hollow part prepared by the technology has good quality and high dimensional precision, so the blade hollow part has wide application prospect in the preparation of new generation aeroengine turbine blades, and can be applied to the directional solidification precision casting of the hollow turbine blades of high-performance gas turbines.
Detailed Description
Example 1
The embodiment comprises the following steps:
step 1) weighing 7kg of quartz glass powder, 1.5kg of aluminum hydroxide powder, 0.3kg of aluminum trifluoride powder and 0.64kg of zirconium silicate powder, and placing the materials in an oven to dry in the air at 150 ℃ for 24 hours for later use;
step 2) putting 0.4kg of semi-refined paraffin, 0.05kg of beeswax, 0.05kg of polyethylene and 0.06kg of oleic acid in a vacuum and wax kettle at 130 ℃ and vacuum degree of 6 multiplied by 10-2Stirring and mixing for 1h under the condition of Pa, then adding quartz glass powder, aluminum hydroxide powder, aluminum trifluoride powder and zirconium silicate powder into a wax mixing kettle, and stirring and mixing for 1h under vacuum degree of 6 multiplied by 10-2Pa, the mixing temperature is 130 ℃, and then the mixture is poured out and cooled to form a material ingot.
And 3) pressing the material ingot by a core pressing machine, utilizing a mould to press and form a ceramic core biscuit, embedding the core biscuit in light magnesium oxide powder, and sintering in the atmosphere by using a core roasting furnace: the first stage is that the temperature is between room temperature and 300 ℃, the temperature rising speed is 30 ℃/h, and the temperature is kept for 4h at 300 ℃; the second stage is that the temperature is 300 ℃ to 600 ℃, the temperature rising speed is 30 ℃/h, and the temperature is kept for 6h at 600 ℃; the third stage is 600 ℃ to 9500 ℃, the temperature rising speed is 30 ℃/h, and the temperature is kept for 8h at 950 ℃; the fourth stage is 900 ℃ to 1180 ℃, the temperature rising speed is 30 ℃/h, and the temperature is kept at 1180 ℃ for 6 h.
And 4) performing strengthening treatment on the sintered ceramic core by using ethyl silicate hydrolysate, namely soaking the core in the ethyl silicate hydrolysate for 6 hours under the vacuum condition, and then performing heat treatment in the air at 150 ℃ for 12 hours to finally obtain a finished product of the ceramic core.
The silicon-based ceramic core without aluminum hydroxide and aluminum trifluoride powder is used as a comparative example, and the bending strength at room temperature is 19.4MPa, the bending strength at 1550 ℃ is 12.3MPa, and the deflection at 1550 ℃ is 1.12 mm. The bending strength of the ceramic core in the embodiment at room temperature is 26.8MPa, the bending strength at 1550 ℃ is 21.4MPa, the deflection at 1550 ℃ is 0.79mm, the porosity is 34.5%, and the performance is obviously superior to that of the ceramic core in the comparative example.
Example 2
The embodiment comprises the following steps:
step 1) weighing 7.5kg of quartz glass powder, 1kg of aluminum hydroxide powder, 0.2kg of aluminum trifluoride powder and 0.6kg of zirconium silicate powder, and placing the materials in an oven to dry in the air at 150 ℃ for 24 hours for later use;
step 2) putting 0.6kg of semi-refined paraffin, 0.03kg of beeswax, 0.03kg of polyethylene and 0.04kg of oleic acid into a vacuum and wax kettle, and keeping the temperature at 110 ℃ and the vacuum degree at 6 multiplied by 10-2Stirring and mixing for 6h under the condition of Pa, then adding quartz glass powder, aluminum hydroxide powder, aluminum trifluoride powder and zirconium silicate powder into a wax mixing kettle, and stirring and mixing for 6h under vacuum degree of 6 multiplied by 10-2Pa, the mixing temperature is 130 ℃, and then the mixture is poured out and cooled to form a material ingot.
And 3) pressing the material ingot by a core pressing machine, utilizing a mould to press and form a ceramic core biscuit, embedding the core biscuit in light magnesium oxide powder, and sintering in the atmosphere by using a core roasting furnace: the first stage is that the temperature is between room temperature and 300 ℃, the temperature rising speed is 30 ℃/h, and the temperature is kept for 3h at 300 ℃; the second stage is that the temperature is 300 ℃ to 600 ℃, the temperature rising speed is 30 ℃/h, and the temperature is kept for 5h at 600 ℃; the third stage is 600 ℃ to 9500 ℃, the temperature rising speed is 30 ℃/h, and the temperature is kept for 7h at 950 ℃; the fourth stage is from 950 ℃ to the highest sintering temperature, the temperature rise speed is 30 ℃/h, and the temperature is kept at 1200 ℃ for 6 h.
And 4) performing strengthening treatment on the sintered ceramic core by using ethyl silicate hydrolysate, namely soaking the core in the ethyl silicate hydrolysate for 6 hours under the vacuum condition, and then performing heat treatment in the air at 150 ℃ for 12 hours to finally obtain a finished product of the ceramic core.
The silicon-based ceramic core without aluminum hydroxide and aluminum trifluoride powder is used as a comparative example, and the bending strength at room temperature is 19.4MPa, the bending strength at 1550 ℃ is 12.3MPa, and the deflection at 1550 ℃ is 1.12 mm. The bending strength of the ceramic core in the embodiment at room temperature is 28.4MPa, the bending strength at 1550 ℃ is 22.5MPa, the deflection at 1550 ℃ is 0.74mm, the porosity is 30.4%, and the performance is obviously superior to that of the ceramic core in the comparative example.
Example 3
The embodiment comprises the following steps:
step 1) weighing 8kg of quartz glass powder, 0.5kg of aluminum hydroxide powder, 0.1kg of aluminum trifluoride powder and 0.56kg of zirconium silicate powder, and placing the materials in an oven to dry in the air at 150 ℃ for 24 hours for later use;
step 2) putting 0.8kg of semi-refined paraffin, 0.01kg of beeswax, 0.01kg of polyethylene and 0.02kg of oleic acid into a vacuum and wax kettle, and keeping the temperature at 110 ℃ and the vacuum degree at 6 multiplied by 10-2Stirring and mixing for 6h under the condition of Pa, then adding quartz glass powder, aluminum hydroxide powder, aluminum trifluoride powder and zirconium silicate powder into a wax mixing kettle, and stirring and mixing for 12h under vacuum degree of 6 multiplied by 10-2Pa, the mixing temperature is 130 ℃, and then the mixture is poured out and cooled to form a material ingot.
And 3) pressing the material ingot by a core pressing machine, utilizing a mould to press and form a ceramic core biscuit, embedding the core biscuit in light magnesium oxide powder, and sintering in the atmosphere by using a core roasting furnace: the first stage is that the temperature is between room temperature and 300 ℃, the temperature rising speed is 30 ℃/h, and the temperature is kept for 3h at 300 ℃; the second stage is that the temperature is 300 ℃ to 600 ℃, the temperature rising speed is 30 ℃/h, and the temperature is kept for 5h at 600 ℃; the third stage is 600 ℃ to 9500 ℃, the temperature rising speed is 30 ℃/h, and the temperature is kept for 7h at 950 ℃; the fourth stage is 950-1220 deg.C, temperature raising rate is 30 deg.C/h, and heat preservation is carried out at 1220 deg.C for 4 h.
And 4) performing strengthening treatment on the sintered ceramic core by using ethyl silicate hydrolysate, namely soaking the core in the ethyl silicate hydrolysate for 6 hours under the vacuum condition, and then performing heat treatment in the air at 150 ℃ for 12 hours to finally obtain a finished product of the ceramic core.
The silicon-based ceramic core without aluminum hydroxide and aluminum trifluoride powder is used as a comparative example, and the bending strength at room temperature is 19.4MPa, the bending strength at 1550 ℃ is 12.3MPa, and the deflection at 1550 ℃ is 1.12 mm. The bending strength of the ceramic core in the embodiment at room temperature is 31.2MPa, the bending strength at 1550 ℃ is 24.5MPa, the deflection at 1550 ℃ is 0.69mm, the porosity is 27.8, and the performance is obviously superior to that of the ceramic core in the comparative example.
In summary, the process is carried out by means of aluminum hydroxide in the core biscuit and SiO in the quartz glass powder2In AlF3The mullite is generated under the catalysis, so that the mullite whisker is generated, the high-temperature strength and the high-temperature creep resistance of the ceramic core are obviously improved, and the dimensional stability of the core is improved.
Compared with the prior art, the bending strength at room temperature of the ceramic core is 26.8-31.2MPa, the bending strength at 1550 ℃ is 21.4-24.5MPa, and the deflection at 1550 ℃ is 0.69-0.79mm, while the bending strength at room temperature of the common silicon-based ceramic core without aluminum hydroxide and aluminum trifluoride powder is 19.4MPa, the bending strength at 1550 ℃ is 12.3MPa, and the deflection at 1550 ℃ is 1.12 mm. The performance index of the ceramic core is obviously improved.
The foregoing embodiments may be modified in many different ways by those skilled in the art without departing from the spirit and scope of the invention, which is defined by the appended claims and all changes that come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.
Claims (10)
1. A preparation method of an in-situ authigenic mullite whisker reinforced silicon-based ceramic core is characterized in that semi-refined paraffin wax, beeswax, polyethylene and oleic acid are placed in a vacuum wax kettle and stirred to be molten, then quartz glass powder, aluminum hydroxide powder, aluminum trifluoride powder and zirconium silicate powder are added, vacuum stirring is further carried out, then pouring is carried out, and after cooling, a material ingot is formed; adding the material ingot into a core pressing machine, and then performing melt pressing to obtain a ceramic core biscuit, wherein aluminum hydroxide and silicon dioxide in quartz glass powder are subjected to mullite treatment under the catalysis of aluminum trifluoride powder to generate mullite whiskers; embedding the ceramic core biscuit in light magnesium oxide powder, and sintering in four stages to obtain a ceramic core; and then the ceramic core is subjected to strengthening treatment to obtain a final ceramic core finished product.
2. The method for preparing the silicon-based ceramic core according to claim 1, wherein the raw materials account for the following overall mass ratio in sequence: 70-80% of quartz glass powder, 5-15% of aluminum hydroxide powder, 1-3% of aluminum trifluoride powder, 5-7% of zirconium silicate powder, 4-8% of semi-refined paraffin, 0.1-0.5% of beeswax, 0.1-0.5% of polyethylene and 0.2-0.6% of oleic acid.
3. The method for preparing the silicon-based ceramic core according to claim 1 or 2, wherein the particle size distribution of the quartz glass powder is 1-60 μm, and the purity is more than or equal to 99.5 wt.%;
the particle size distribution of the aluminum hydroxide is 0.1-2 mu m, and the purity is more than or equal to 99 wt.%;
the particle size distribution of the aluminum trifluoride powder is 1-60 mu m, and the purity is more than or equal to 99 wt.%;
the particle size distribution of the zirconium silicate powder is 1-38 mu m, and the purity is more than or equal to 99 wt.%;
the semi-refined paraffin, the beeswax, the polyethylene and the oleic acid are all industrial products.
4. The method for preparing the silicon-based ceramic core according to claim 1, wherein the quartz glass powder, the aluminum hydroxide powder, the aluminum trifluoride powder and the zirconium silicate powder are dried before being mixed, and the method comprises the following specific steps: drying in air at 150 deg.C for 24 h.
5. The method of claim 1, wherein the ceramic silica-based core is melted by stirring at a speed of 120r/min, at a temperature of 130 ℃ and a vacuum of 6 x 10-2Pa, and the stirring time is 1-12 h.
6. The method of claim 1, wherein the vacuum stirring is performed at a speed of 120r/min, at a temperature of 130 ℃ and a vacuum of 6 x 10-2Pa, and the stirring time is 1-12 h.
7. The method as claimed in claim 1, wherein the four-stage sintering is carried out at a temperature of 1180-: in the first stage, the room temperature is between 300 ℃ and 30 ℃/h, and the temperature is kept at 300 ℃ for 2 to 4 h; in the second stage, the temperature is 300-600 ℃, the heating rate is 30 ℃/h, and the temperature is kept at 600 ℃ for 4-6 h; in the third stage, the temperature is 600-950 ℃, the heating rate is 30 ℃/h, and the temperature is kept at 950 ℃ for 6-8 h; in the fourth stage, the temperature is 900 ℃ to the highest sintering temperature, the heating rate is 30 ℃/h, and the temperature is kept for 4-6h at the highest sintering temperature.
8. The method of claim 1, wherein the sintered ceramic core is further strengthened by immersing in a hydrolyzed solution of ethyl silicate and heating.
9. The method for preparing the silicon-based ceramic core according to claim 8, wherein the ethyl silicate hydrolysate comprises the following components in percentage by weight: 31.3% of ethyl silicate, 28% of absolute ethyl alcohol, 1.5% of isopropanol, 13% of propylene glycol methyl ether, 25.8% of acidic silica sol and 0.4% of hydrochloric acid aqueous solution;
the pH value of the acidic silica sol is 2-3 and SiO in the acidic silica sol2The content is 25-28%;
the concentration of the hydrochloric acid aqueous solution is 20-20.2 wt.%.
10. A silicon-based ceramic core produced according to any of the preceding claims, wherein the room temperature flexural strength is 26.8-31.2MPa, the flexural strength at 1550 ℃ is 21.4-24.5MPa, the deflection at 1550 ℃ is 0.69-0.79mm, and the porosity is 27.8-34.5%.
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Cited By (8)
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| CN113135738A (en) * | 2021-04-14 | 2021-07-20 | 上海联泰科技股份有限公司 | Mullite whisker in-situ generated reinforced silicon-based ceramic core and 3D printing preparation method thereof |
| CN114054682A (en) * | 2021-11-26 | 2022-02-18 | 江苏智疆航空科技发展有限公司 | Preparation process of ceramic core for aircraft engine |
| CN114082881A (en) * | 2021-11-26 | 2022-02-25 | 江苏智疆航空科技发展有限公司 | Preparation method of silicon-based ceramic core for aircraft engine blade |
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| CN114507079A (en) * | 2022-03-09 | 2022-05-17 | 陕西科技大学 | Mullite fiber reinforced metal matrix composite ceramic sheet and preparation method thereof |
| CN114507079B (en) * | 2022-03-09 | 2022-12-30 | 陕西科技大学 | Mullite fiber reinforced metal-based composite ceramic sheet and preparation method thereof |
| CN116020977A (en) * | 2023-02-06 | 2023-04-28 | 中国航发北京航空材料研究院 | Ceramic core with multi-layer wall structure and preparation method thereof |
| CN116020977B (en) * | 2023-02-06 | 2024-05-17 | 中国航发北京航空材料研究院 | Ceramic core with multi-layer wall structure and preparation method thereof |
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