CN111592379A - Preparation method of ceramic core coating based on dipping freeze drying technology - Google Patents
Preparation method of ceramic core coating based on dipping freeze drying technology Download PDFInfo
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- CN111592379A CN111592379A CN202010543028.5A CN202010543028A CN111592379A CN 111592379 A CN111592379 A CN 111592379A CN 202010543028 A CN202010543028 A CN 202010543028A CN 111592379 A CN111592379 A CN 111592379A
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B41/00—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone
- C04B41/80—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone of only ceramics
- C04B41/81—Coating or impregnation
- C04B41/85—Coating or impregnation with inorganic materials
- C04B41/87—Ceramics
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B41/00—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone
- C04B41/45—Coating or impregnating, e.g. injection in masonry, partial coating of green or fired ceramics, organic coating compositions for adhering together two concrete elements
- C04B41/50—Coating or impregnating, e.g. injection in masonry, partial coating of green or fired ceramics, organic coating compositions for adhering together two concrete elements with inorganic materials
- C04B41/5025—Coating or impregnating, e.g. injection in masonry, partial coating of green or fired ceramics, organic coating compositions for adhering together two concrete elements with inorganic materials with ceramic materials
- C04B41/5031—Alumina
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Abstract
The invention discloses a preparation method of a ceramic core coating based on dipping freeze drying, which comprises the following steps: s1, mixing aluminum isopropoxide and deionized water according to a molar ratio, and stirring; s2, adding a peptizing agent HNO3Controlling the pH value of the slurry, stirring in a water bath condition, and obtaining transparent alumina slurry after a period of time; s3, carrying out dipping treatment on the ceramic core substrate to obtain a ceramic core coating with a certain thickness; s4, pre-freezing the obtained ceramic core coating, and carrying out sublimation drying treatment; and S5, sintering the ceramic core coating after sublimation drying treatment, and keeping the temperature for a period of time. On one hand, the high-temperature thermal stability is good, the coating does not generate chemical reaction with elements such as Hf, Al, C and the like, and the prepared coating does not have cracking and peeling phenomena; on the other hand, the thickness of the ceramic core coating can be controlled; the core removing performance of the original silicon-based core is not reduced.
Description
Technical Field
The invention relates to the technical field of coating forming, in particular to a preparation method of a ceramic core coating based on a dipping freeze drying technology.
Background
The ceramic core is used for forming the inner cavity shape of the casting. The surface quality and dimensional accuracy of the casting cavity are completely determined by the ceramic core. It is therefore desirable that the ceramic cores do not react with the molten metal during casting, that the casting internal profile maintain a low roughness, and that they are easily removed from the casting internal cavity after casting is complete.
The traditional ceramic core coating forming technology mainly comprises a compressed air spraying method, a brushing method, a chemical vapor deposition method, a sol-gel method and the like. However, in the traditional process of preparing the ceramic core coating, two problems exist: firstly, the ceramic core coating manufactured by the traditional method has higher porosity, larger surface roughness and poorer thermal stability at high temperature. Secondly, the coating thickness of the ceramic core prepared by the traditional method is difficult to control, and the coating can crack and peel after a period of time, thus seriously affecting the service life of the ceramic core and the blade.
Disclosure of Invention
The present invention is intended to solve the above-mentioned technical problems.
Aiming at the technical problem, the invention provides a preparation method of a ceramic core coating based on dipping freeze drying, which comprises the following steps:
s1, mixing aluminum isopropoxide and deionized water according to a molar ratio, and stirring;
s2, adding a peptizing agent HNO3, controlling the pH value of the slurry, stirring in a water bath condition, and obtaining transparent alumina slurry after a period of time;
s3, carrying out dipping treatment on the ceramic core substrate to obtain a ceramic core coating with a certain thickness;
and S4, pre-freezing the obtained ceramic core coating and carrying out sublimation drying treatment.
And S5, sintering the ceramic core coating after sublimation drying treatment, and keeping the temperature for a period of time.
Preferably, in the step S1, the purity of the selected aluminum isopropoxide is analytically pure, and the molar ratio of the aluminum isopropoxide to the deionized water is 1:2 to 1: 10.
Preferably, in step S1, the stirring is performed by a heat-collecting magnetic stirrer, and the stirring time is 40min to 120 min.
Preferably, in the step S2, the PH of the slurry is controlled to be 2 to 5 by adding a peptizing agent HNO 3.
Preferably, in the step S2, magnetic stirring is performed under the water bath condition, wherein the magnetic stirring time is 12h-24h, and the water bath temperature is 85 ℃.
Preferably, in the step S3, the ceramic core substrate is dipped into the slurry for 30S to 150S, the core is slowly rotated by a rotating device at a rotating speed of 10 to 20r/min, and then dried in the air for 5 to 10min until the surface slurry is solidified.
Preferably, in step S3, the dipping times and slurry concentration are controlled according to the coating thickness requirement, wherein, the coating thickness is controlled to be 30 μm-100 μm each time.
Preferably, in the step S4, the pre-freezing treatment temperature of the ceramic core coating after the dipping is-20 ℃ to-30 ℃.
Preferably, in the step S4, the sublimation drying is performed at a temperature of-10 to 100 ℃ under a pressure of 10 to 100Pa, and ice crystals on the coating are sublimated and removed in a vacuum environment.
Preferably, in the step S5, the sintering temperature is 900-.
Compared with the prior art, the invention has at least the following beneficial effects:
1. the invention realizes that the metal liquid of the core at the temperature of (1580 +/-10) does not react with elements such as Hf, Al, C and the like, and the surface roughness of the formed ceramic core with the coating is not more than Ra2.4.
2. The coating prepared by the invention has the thickness range of 30-100 mu m, the thickness of the core coating can be controlled by adjusting the dipping times and the slurry concentration, and the coating has no cracking and stripping phenomena.
3. The invention can not reduce the original decoring performance of the silicon-based core, ensures that the casting can be completely decored in the conventional silicon-based decoring process and equipment, and the decoring time is not more than 24 h.
Drawings
FIG. 1 is a flow chart of a method for preparing a novel ceramic coating according to an embodiment of the present invention.
FIG. 2 is a graph showing the thickness of the alumina coating layer of one impregnation in the example of the present invention.
FIG. 3 is a graphical representation of the thickness of the alumina coating for three impregnations in an example of the invention.
Detailed Description
The invention is further illustrated with reference to the following figures and examples.
Example one
As shown in FIG. 1, the invention provides a preparation method of a ceramic core coating based on immersion freeze drying, which comprises the following steps:
s1, mixing aluminum isopropoxide and deionized water according to a molar ratio, and stirring;
s2, adding a peptizing agent HNO3, controlling the pH value of the slurry, stirring in a water bath condition, and obtaining transparent alumina slurry after a period of time;
s3, carrying out dipping treatment on the ceramic core substrate to obtain a ceramic core coating with a certain thickness;
and S4, pre-freezing the obtained ceramic core coating and carrying out sublimation drying treatment.
And S5, sintering the ceramic core coating after sublimation drying treatment, and keeping the temperature for a period of time.
In this embodiment, in the step S1, the purity of the selected aluminum isopropoxide should be analytically pure, and the molar ratio of the aluminum isopropoxide to the deionized water is in a range of 1:2 to 1: 10. This example illustrates mixing of aluminum isopropoxide with deionized water at a 1:3 molar ratio.
In this embodiment, in step S1, stirring is performed by a heat-collecting magnetic stirrer, and the stirring time is 40min to 120 min. This example is illustrated by stirring for 40 min.
In this embodiment, in the step S2, the peptizing agent HNO is added3The pH value of the slurry is controlled to be 2-5. In this example, the pH of the slurry is controlled to about 3.
In this embodiment, in the step S2, magnetic stirring is performed under the water bath condition, wherein the magnetic stirring time is 12h to 24h, and the water bath temperature is 85 ℃. This example is described with stirring for 12 h.
In this embodiment, in step S3, the ceramic core substrate is dipped into the slurry for 30S to 150S, the core is slowly rotated by a rotating device at a rotation speed of 10 to 20r/min, and then dried in air for 5 to 10min until the surface slurry is cured. In this example, the rotation speed was 10r/min, and the surface slurry was solidified after drying for 5 min. While another ceramic core substrate was impregnated 3 times under the same conditions as a comparative example.
In this embodiment, in step S3, the dipping times and slurry concentration are controlled according to the coating thickness requirement, wherein each coating thickness is controlled to be 30 μm-100 μm. In this example, the thickness of the coating, the number of dips, and the concentration of the slurry are proportional.
In this embodiment, the pre-freezing temperature of the impregnated ceramic core coating is-20 ℃ to-30 ℃ in step S4. This example is described with the prefreezing temperature set at-20 ℃.
In this embodiment, in the step S4, the sublimation drying is performed at a temperature of-10 to 100 ℃ under a pressure of 10 to 100Pa, and ice crystals on the coating are sublimated and removed in a vacuum environment. In the embodiment, the air pressure of vacuum drying is 50Pa, the temperature is-10 to 100 ℃ until ice crystals on the coating are sublimated and removed
In this embodiment, in the step S5, the sintering temperature is 900-. This example is described with a sintering temperature of 1000 ℃ and a holding time of 2 hours.
As shown in FIG. 2, the thickness of the alumina coating was about 50 μm for 1 impregnation in this example, and about 151 μm for 3 impregnations as shown in FIG. 3.
In the embodiment, the ceramic core coating obtained by vacuum freeze sublimation drying has good high-temperature thermal stability on one hand, does not react with elements such as Hf, Al, C and the like, and the prepared coating has no cracking and peeling phenomena; on the other hand, the thickness of the ceramic core coating can be controlled by adjusting the dipping times and the slurry concentration, and the coating has no cracking and stripping phenomena; the core removing performance of the original silicon-based core is not reduced, the casting can be completely removed in the conventional silicon-based core removing process and equipment, and the core removing time is not more than 24 hours.
The above examples are intended only to illustrate specific embodiments of the present invention. It should be noted that those skilled in the art should also realize that they fall within the scope of the present invention without departing from the spirit of the invention.
Claims (10)
1. A preparation method of a ceramic core coating based on immersion freeze drying is characterized by comprising the following steps:
s1, mixing aluminum isopropoxide and deionized water according to a molar ratio, and stirring;
s2, adding a peptizing agent HNO3Controlling the pH value of the slurry, stirring in a water bath condition, and obtaining transparent alumina slurry after a period of time;
s3, carrying out dipping treatment on the ceramic core substrate to obtain a ceramic core coating with a certain thickness;
s4, pre-freezing the obtained ceramic core coating, and carrying out sublimation drying treatment;
and S5, sintering the ceramic core coating after sublimation drying treatment, and keeping the temperature for a period of time.
2. The method for preparing the ceramic core coating based on the immersion freeze drying technology as claimed in claim 1, wherein in the step S1, the purity of the selected aluminum isopropoxide is analytically pure, and the molar ratio of the aluminum isopropoxide to the deionized water is in a range of 1:2 to 1: 10.
3. The method for preparing a ceramic core coating based on an immersion freeze-drying technology as claimed in claim 1, wherein in step S1, stirring is performed by a heat-collecting magnetic stirrer for 40min-120 min.
4. The method for preparing a ceramic core coating based on the immersion freeze drying technology as claimed in claim 1, wherein in the step S2, a peptizing agent HNO is added3The pH value of the slurry is controlled to be 2-5.
5. The method for preparing a ceramic core coating based on the immersion freeze drying technology as claimed in claim 1, wherein in the step S2, magnetic stirring is performed under the water bath condition, wherein the magnetic stirring time is 12h-24h, and the water bath temperature is 85 ℃.
6. The method as claimed in claim 1, wherein the step S3, the ceramic core substrate is dipped in the slurry for 30S-150S, the core is slowly rotated at a rotation speed of 10-20r/min by a rotating device, and then dried in air for 5-10min until the surface slurry is solidified.
7. The method for preparing a ceramic core coating based on the immersion freeze-drying technology as claimed in claim 1, wherein in step S3, the number of immersion times and slurry concentration are controlled according to the coating thickness requirement, wherein, each coating thickness is controlled to be 30 μm-100 μm.
8. The method for preparing a ceramic core coating based on the immersion freeze-drying technology as claimed in claim 1, wherein the temperature for pre-freezing the ceramic core coating after immersion in step S4 is-20 ℃ to-30 ℃.
9. The method for preparing the ceramic core coating based on the immersion freeze drying technology as claimed in claim 1, wherein in the step S4, the sublimation drying gas pressure is 10 to 100Pa, the temperature is-10 to 100 ℃, and ice crystals on the coating are removed by sublimation in a vacuum environment.
10. The method as claimed in claim 1, wherein the sintering temperature is 900-1050 ℃ and the holding time is 2-3 h in step S5.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115799552A (en) * | 2023-02-10 | 2023-03-14 | 海卓动力(青岛)能源科技有限公司 | Preparation method of composite graphite resin carbon fiber polar plate |
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| CN103320776A (en) * | 2013-06-08 | 2013-09-25 | 武汉理工大学 | Non-vacuum high temperature solar selective absorbing coating composite anti-reflection coating and preparation method thereof |
| CN103342576A (en) * | 2013-06-25 | 2013-10-09 | 西安交通大学 | Preparation method of nanocomposite Al2O3 ceramic filter element |
| KR101481465B1 (en) * | 2013-08-27 | 2015-01-13 | 한국지질자원연구원 | Method for manufacturing iron sulfide coated Porous supporter and iron sulfide coated Porous supporter manufactured by samemethod |
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2020
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Patent Citations (6)
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| CN102491785A (en) * | 2011-12-06 | 2012-06-13 | 辽宁速航特铸材料有限公司 | Method for improving property of ceramic core through high-temperature inorganic coating |
| CN103320776A (en) * | 2013-06-08 | 2013-09-25 | 武汉理工大学 | Non-vacuum high temperature solar selective absorbing coating composite anti-reflection coating and preparation method thereof |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN115799552A (en) * | 2023-02-10 | 2023-03-14 | 海卓动力(青岛)能源科技有限公司 | Preparation method of composite graphite resin carbon fiber polar plate |
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