CN116765325A - 1800 ℃ resistant directional solidification BN shell - Google Patents
1800 ℃ resistant directional solidification BN shell Download PDFInfo
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- CN116765325A CN116765325A CN202310731561.8A CN202310731561A CN116765325A CN 116765325 A CN116765325 A CN 116765325A CN 202310731561 A CN202310731561 A CN 202310731561A CN 116765325 A CN116765325 A CN 116765325A
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- shell
- directional solidification
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- pouring cup
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- 238000007711 solidification Methods 0.000 title claims abstract description 30
- 230000008023 solidification Effects 0.000 title claims abstract description 30
- 238000005245 sintering Methods 0.000 claims abstract description 22
- PZNSFCLAULLKQX-UHFFFAOYSA-N Boron nitride Chemical compound N#B PZNSFCLAULLKQX-UHFFFAOYSA-N 0.000 claims abstract description 21
- 238000000034 method Methods 0.000 claims abstract description 21
- 238000002360 preparation method Methods 0.000 claims abstract description 16
- 229910052582 BN Inorganic materials 0.000 claims abstract description 15
- 238000012545 processing Methods 0.000 claims abstract description 10
- 238000003754 machining Methods 0.000 claims abstract description 4
- 239000000843 powder Substances 0.000 claims description 15
- 238000002156 mixing Methods 0.000 claims description 4
- 235000019580 granularity Nutrition 0.000 claims description 3
- 239000012299 nitrogen atmosphere Substances 0.000 claims description 2
- 210000001503 joint Anatomy 0.000 claims 1
- 239000010410 layer Substances 0.000 abstract description 10
- 239000002344 surface layer Substances 0.000 abstract description 9
- 238000005266 casting Methods 0.000 abstract description 8
- 229910045601 alloy Inorganic materials 0.000 abstract description 7
- 239000000956 alloy Substances 0.000 abstract description 7
- 230000009286 beneficial effect Effects 0.000 abstract description 3
- 230000007547 defect Effects 0.000 abstract description 3
- 238000012797 qualification Methods 0.000 abstract description 2
- 230000035939 shock Effects 0.000 abstract description 2
- 239000000463 material Substances 0.000 description 16
- 230000008569 process Effects 0.000 description 9
- 239000000155 melt Substances 0.000 description 6
- RVTZCBVAJQQJTK-UHFFFAOYSA-N oxygen(2-);zirconium(4+) Chemical compound [O-2].[O-2].[Zr+4] RVTZCBVAJQQJTK-UHFFFAOYSA-N 0.000 description 5
- BRPQOXSCLDDYGP-UHFFFAOYSA-N calcium oxide Chemical compound [O-2].[Ca+2] BRPQOXSCLDDYGP-UHFFFAOYSA-N 0.000 description 4
- ODINCKMPIJJUCX-UHFFFAOYSA-N calcium oxide Inorganic materials [Ca]=O ODINCKMPIJJUCX-UHFFFAOYSA-N 0.000 description 4
- 239000000292 calcium oxide Substances 0.000 description 4
- 239000000919 ceramic Substances 0.000 description 4
- 229910052799 carbon Inorganic materials 0.000 description 3
- 239000002131 composite material Substances 0.000 description 3
- 238000002844 melting Methods 0.000 description 3
- 230000008018 melting Effects 0.000 description 3
- 229910000601 superalloy Inorganic materials 0.000 description 3
- 229910001928 zirconium oxide Inorganic materials 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 2
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 2
- 229910001069 Ti alloy Inorganic materials 0.000 description 2
- MCMNRKCIXSYSNV-UHFFFAOYSA-N ZrO2 Inorganic materials O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 description 2
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 2
- 239000011230 binding agent Substances 0.000 description 2
- 229910052810 boron oxide Inorganic materials 0.000 description 2
- JKWMSGQKBLHBQQ-UHFFFAOYSA-N diboron trioxide Chemical compound O=BOB=O JKWMSGQKBLHBQQ-UHFFFAOYSA-N 0.000 description 2
- 238000005495 investment casting Methods 0.000 description 2
- 239000004973 liquid crystal related substance Substances 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- 239000004576 sand Substances 0.000 description 2
- 230000009471 action Effects 0.000 description 1
- 238000005275 alloying Methods 0.000 description 1
- 230000002860 competitive effect Effects 0.000 description 1
- 238000009770 conventional sintering Methods 0.000 description 1
- 229910052593 corundum Inorganic materials 0.000 description 1
- 239000010431 corundum Substances 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000012938 design process Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- KZHJGOXRZJKJNY-UHFFFAOYSA-N dioxosilane;oxo(oxoalumanyloxy)alumane Chemical compound O=[Si]=O.O=[Si]=O.O=[Al]O[Al]=O.O=[Al]O[Al]=O.O=[Al]O[Al]=O KZHJGOXRZJKJNY-UHFFFAOYSA-N 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 239000000835 fiber Substances 0.000 description 1
- 238000011049 filling Methods 0.000 description 1
- 230000017525 heat dissipation Effects 0.000 description 1
- 238000007731 hot pressing Methods 0.000 description 1
- 238000009776 industrial production Methods 0.000 description 1
- 238000009413 insulation Methods 0.000 description 1
- 229910000765 intermetallic Inorganic materials 0.000 description 1
- 239000002932 luster Substances 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000011812 mixed powder Substances 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 229910052863 mullite Inorganic materials 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- LIZIAPBBPRPPLV-UHFFFAOYSA-N niobium silicon Chemical compound [Si].[Nb] LIZIAPBBPRPPLV-UHFFFAOYSA-N 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 230000006911 nucleation Effects 0.000 description 1
- 238000010899 nucleation Methods 0.000 description 1
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- RMAQACBXLXPBSY-UHFFFAOYSA-N silicic acid Chemical compound O[Si](O)(O)O RMAQACBXLXPBSY-UHFFFAOYSA-N 0.000 description 1
- 238000004513 sizing Methods 0.000 description 1
- 239000007921 spray Substances 0.000 description 1
- JINJMFAIGCWUDW-UHFFFAOYSA-L zirconium(2+);diacetate Chemical compound [Zr+2].CC([O-])=O.CC([O-])=O JINJMFAIGCWUDW-UHFFFAOYSA-L 0.000 description 1
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- Ceramic Products (AREA)
Abstract
The invention relates to a casting shell, in particular to a 1800 ℃ resistant directional solidification BN shell, which comprises a shell base, a shell main body and a pouring cup; the mold shell main body is assembled between the mold shell base and the pouring cup to form a mold shell for directional solidification; the shell base, the shell main body and the pouring cup are all formed by processing hexagonal boron nitride blocks sintered at high temperature and high pressure. Compared with the prior art, the invention fully plays the advantages of high-temperature high-pressure sintering BN, such as high density, small expansion coefficient, good thermal shock resistance and good machining property, adopts a mechanical processing and assembling method to replace the existing lost wax method preparation process, thoroughly solves the defects of easy falling-off of BN shell surface layer and insufficient strength of back layer in lost wax method preparation, and is beneficial to improving the directional solidification preparation qualification rate and quality of the ultra-high temperature alloy.
Description
Technical Field
The invention relates to a casting shell, in particular to a directional solidification BN shell resistant to 1800 ℃.
Background
The rapid development of the modern aviation industry places higher demands on thrust-to-weight ratio of an aeroengine, and increasing turbine front inlet temperature is one of the most effective ways to achieve large thrust-to-weight ratio. The research shows that when the temperature of the front inlet of the turbine is increased by 55 ℃, the thrust of the engine is increased by 10%, the temperature of the front inlet of the turbine of the next-generation high thrust-weight ratio aeroengine can reach 1827-2027 ℃, and more severe requirements are provided for materials of hot end components (such as turbine blades, turbine outer ring blocks, spray pipes and the like) of the engine. Therefore, developing materials with higher heat resistant temperatures is a critical task to increase the thrust-to-weight ratio of advanced aircraft engines. Currently, high temperature materials with application potential mainly include intermetallic materials (NbSi-based super-high temperature alloys), carbon/carbon composite materials, ceramic-based composite materials, and the like. Of these, nbSi-based ultrahigh-temperature alloys have been widely studied and paid attention to because of their high melting point (over 1700 ℃ C.) and high-temperature tensile properties (over 200MPa high-temperature tensile strength at 1200 ℃ C.).
In the directional solidification process, a shell having a blade shape is preheated in a heat-retaining furnace, and after a predetermined preheating temperature is reached, a high-temperature alloy melt is poured into the shell, and the shell is pulled out of the shell heat-retaining furnace together with the melt at a fixed pull rate, thereby forming a directional heat dissipation, and a columnar/single-crystal structure is obtained after the melt is directionally solidified. For nickel-based superalloy, the shell application temperature is about 1500 ℃, a lost wax method is generally adopted, the surface layer is generally high-purity corundum powder, and the back layer material is generally aluminum oxide/zirconium oxide sand/calcium oxide. However, for NbSi-based superalloys, on the one hand the facing material is easily reacted with the melt during directional solidification; on the other hand, the shell insulation temperature exceeds 1800 ℃, the conventional back layer material alumina is close to the melting point, and zirconium oxide, calcium oxide and the like are easy to soften, so that directional solidification is interrupted.
Patent CN 104550736A discloses a preparation method of boron nitride ceramic shell for titanium alloy precision casting, its technological route adopts lost wax method, surface layer material adopts 325 mesh boron nitride powder material and binder zirconium diacetate or silica sol to mix, and its back layer material adopts conventional mixture of alumina sand and mullite powder material, and is mainly used for solving the problem of shell surface layer and titanium alloy melt reaction. Patent CN 109108224A discloses a preparation method of a ceramic shell for directional solidification investment casting of niobium-silicon-based alloy blades, the process route is also a lost wax method, the surface layer material is mixed powder of calcium oxide stabilized zirconium dioxide and hexagonal boron nitride, the back layer material is calcium oxide stabilized zirconium dioxide powder and powdery zirconium oxide fiber, and the preparation method is mainly used for solving the problem that the ceramic shell is not deformed or cracked when bearing high temperature of 2000 ℃.
However, due to the process characteristics of the lost wax method (natural sizing, conventional sintering), although binders of different properties are tried, the bonding between BN is relatively loose, the surface layer of the shell has the disadvantage of easy falling off, and the back layer of the shell still has the disadvantage of softening at ultra-high temperature (above 1800 ℃). Therefore, for the characteristic of high melting point of intermetallic compound, it is necessary to develop a shell suitable for directional solidification at high temperature above 1800 ℃, and it is necessary to provide the following two conditions (1) that the material of the back layer of the shell can withstand high temperature in the directional solidification process for a long time, i.e. the back layer should have strength meeting the use requirement under the extreme high temperature condition; (2) The shell surface layer material cannot react chemically with the alloying elements, i.e. is still chemically inert with respect to the highly alloyed alloy melt at extremely high temperatures.
Disclosure of Invention
The invention aims to solve at least one of the problems and provide a directional solidification BN shell resistant to 1800 ℃ so as to solve the problems that a surface layer is easy to fall off and a back layer is easy to soften in the BN shell prepared by an ultrahigh temperature lost wax process in the prior art.
The aim of the invention is achieved by the following technical scheme:
a directional solidification BN mould shell resistant to 1800 ℃ comprises a mould shell base, a mould shell main body and a pouring cup;
the mold shell main body is assembled between the mold shell base and the pouring cup to form a mold shell for directional solidification;
the shell base, the shell main body and the pouring cup are all formed by processing hexagonal boron nitride blocks sintered at high temperature and high pressure.
Preferably, the preparation method of the hexagonal boron nitride block sintered at high temperature and high pressure comprises the following steps:
mixing at least two hexagonal boron nitride powders with different granularities, and then sintering at high temperature and high pressure.
Preferably, in the preparation method, hexagonal boron nitride powder of 20 meshes and 200 meshes is adopted for 2:8, mixing and sintering, and enabling small-diameter powder to be distributed in gaps of large-diameter powder through powder matching with different mesh numbers (particle sizes), so that the space filling rate of boron nitride and the compactness of boron nitride powder are improved.
Preferably, in the preparation method, the hexagonal boron nitride powder is sintered for 30 to 120 minutes at a sintering temperature of 1450 to 1650 ℃, a sintering pressure of 20 to 35MPa and a nitrogen atmosphere.
Preferably, the shell body is formed by assembling and butting a plurality of independent machined split components.
Preferably, the shell main body is formed by assembling and butting a concave main body and a cover plate; the concave main body opening is provided with a groove, and the cover plate is inserted into the groove for positioning.
Preferably, the top of the shell base is provided with a lower supporting structure extending towards the inside, the bottom of the pouring cup is provided with an upper supporting structure extending towards the inside, and the shell main body is assembled between the upper supporting structure and the lower supporting structure.
Preferably, the central channel formed by the upper support structure is matched with the main body of the mold shell, and the central channel formed by the lower support structure is matched with the main body of the mold shell.
Preferably, mounting holes are formed in two sides of the shell main body and used for hanging the core to prepare the hollow turbine blade.
Preferably, the machining precision is not more than +/-0.02 mm, which is beneficial to controlling the dimensional precision of the cast casting.
Compared with the prior art, the invention has the following beneficial effects:
the invention overturns the traditional process for preparing the shell for directional solidification by the lost wax method, prepares the BN shell with the temperature resistance of more than 1800 ℃ by directly sintering BN at high temperature and high pressure and adopting a mechanical processing and mechanical assembly method. The advantages of high density, small expansion coefficient, good thermal shock resistance and good machining performance of the high-temperature high-pressure sintering BN are fully exerted, the defects that the BN shell surface layer is easy to fall off and the back layer strength is insufficient in the preparation of the BN shell by a lost wax method are thoroughly overcome, and the quality and the qualification rate of the ultrahigh-temperature alloy directional solidification preparation product are improved. Meanwhile, the invention greatly shortens the preparation process flow of the directional solidification shell and greatly improves the industrial production efficiency.
Drawings
FIG. 1 is a schematic cross-sectional view of a BN shell;
FIG. 2 is a schematic side view of the structure of a BN shell;
FIG. 3 is a schematic cross-sectional view of the structure of section B-B of FIG. 2;
FIG. 4 is a photograph of a directionally solidified NbSi superalloy cast with a BN shell as described in example 1;
in the figure: 1-a shell base; a 2-type shell body; 21-a concave body; 22-cover plate; 3-pouring cup.
Detailed Description
The invention will now be described in detail with reference to the drawings and specific examples.
Example 1
In the embodiment, a shell for directional solidification at a high temperature of more than 1800 ℃ is used for preparing a NbSiTiAlNb directional solidification sample, and the design and preparation process of the shell are as follows;
a BN type shell structure for directional solidification resistant to high temperatures above 1800 ℃, as shown in fig. 1-3, can be divided into three parts, comprising: shell base, shell main part and pouring cup.
The shell main body is assembled between the shell base and the pouring cup to form a BN shell for directional solidification, and the shell base, the shell main body and the pouring cup are all formed by adopting a hexagonal boron nitride block body through high-temperature and high-pressure sintering after high-temperature and high-pressure sintering.
More specifically:
1) High-temperature high-pressure sintering of BN block: adopting hexagonal boron nitride powder compounded with different granularities to sinter BN blocks in a high-temperature and high-pressure environment;
2) Preparation of pouring cup, molded shell main body and molded shell base: respectively processing the BN block obtained in the step 1) into the shapes of a pouring cup, a casting main body and a shell base by utilizing a numerical control center;
3) Assembling BN type shell: the cast body type shell is assembled together first and then with the pouring cup bottom and shell base top to form the BN type shell shown in figures 1 and 2.
Wherein, the liquid crystal display device comprises a liquid crystal display device,
the BN high-temperature sintering process comprises the following steps: selecting high-purity hexagonal boron nitride powder with two particle sizes of 20 meshes and 200 meshes, wherein the purity is more than 99wt.%; the purity of the sintering aid boron oxide powder is more than 99 percent, and the addition amount of the sintering aid boron oxide powder is 5wt.%. Raw material powder is weighed according to the adding proportion (20 meshes: 200 meshes=2:8, mass ratio), and is put into a mixer to be mixed for 10 hours, and then is dried in a drying oven for 10 hours to obtain uniform composite powder. And (3) hot-pressing sintering is carried out under the protection of nitrogen after the material mixing is finished, wherein the sintering temperature is 1500 ℃, the sintering pressure is 30MPa, and the sintering time is 60 minutes, so that the large-size boron nitride block is obtained.
The pouring cup, the molded shell main body and the molded shell base are all obtained by processing the prepared hexagonal boron nitride block body through a numerical control center and sintering at high temperature and high pressure.
The lower part of the shell base is a relatively large hollow cuboid, the cross section of which is larger than that of the casting main body, and the hollow cuboid is used for exciting nucleation and competitive growth of a melt in a directional solidification process; the shell main body is of a hollow structure, is a main body part of directional solidification and is a casting body; the pouring cup is cup-shaped and can hold a certain amount of melt, and the bottom opening is used for inputting the melt into the shell main body.
The shell body is formed by a concave body (A surface of the shell body) and a cover plate (B surface of the shell body), and the concave body and the cover plate are respectively processed and molded, and then are assembled through a groove reserved at an opening of the concave body, as shown in fig. 3.
The pouring cup and the mold shell base are respectively provided with supporting structures (an upper supporting structure in the pouring cup and a lower supporting structure in the mold shell base) which extend inwards in a processing mode at the top of the mold shell base and at the bottom of the pouring cup, and the pouring cup and the mold shell base are in a T-shaped step mode and are used for limiting and assembling and fixing the mold shell main body as shown in fig. 1. The channel (inner hole) reserved in the center of the supporting structure is respectively corresponding and consistent with the two end heads of the shell main body in the specification of size, shape and the like, so that melt can smoothly pass through in the pouring process.
In order to ensure the stability of the whole assembly of the pouring cup, the molded shell main body and the molded shell base, the processing precision is controlled to be +/-0.02 mm in the processing process, and the assembly precision is ensured to be +0.01mm, so that the molded shell main body can not shake obviously relative to the pouring cup and the molded shell base even under the action of certain external force after the final assembly is completed.
As shown in FIG. 4, the NbSiTiNb directional solidification sample prepared by using the BN shell for directional solidification resistant to the temperature of more than 1800 ℃ is obviously shown from the surface of a casting, the surface of the casting presents bright metallic luster, no oxide or attachment exists, the melt does not chemically react with the shell, and meanwhile, no obvious defect exists at the joint of a concave main body and a cover plate, which indicates that the assembly is stable and firm, and further proves that the method is simple and feasible.
The BN shells may be provided with mounting holes on both sides of the shell body for suspending cores for use in the preparation of hollow turbine blades.
The previous description of the embodiments is provided to facilitate a person of ordinary skill in the art in order to make and use the present invention. It will be apparent to those skilled in the art that various modifications can be readily made to these embodiments and the generic principles described herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present invention is not limited to the above-described embodiments, and those skilled in the art, based on the present disclosure, should make improvements and modifications without departing from the scope of the present invention.
Claims (10)
1. A directional solidification BN mould shell resistant to 1800 ℃ is characterized by comprising a mould shell base (1), a mould shell main body (2) and a pouring cup (3);
the mold shell main body (2) is assembled between the mold shell base (1) and the pouring cup (3) to form a mold shell for directional solidification;
the shell base (1), the shell main body (2) and the pouring cup (3) are all formed by processing hexagonal boron nitride blocks sintered at high temperature and high pressure.
2. The directional solidification BN shell of claim 1, wherein the method for preparing the hexagonal boron nitride block by high-temperature high-pressure sintering is as follows:
mixing at least two hexagonal boron nitride powders with different granularities, and then sintering at high temperature and high pressure.
3. A directionally solidified BN shell resistant to 1800 ℃ as claimed in claim 2, wherein in the preparation method, 20 mesh and 200 mesh hexagonal boron nitride powder is used to produce a powder of 2:8 mass ratio, and sintering.
4. The directional solidification BN shell of claim 2, wherein the hexagonal boron nitride powder is sintered at 1450-1650 ℃, 20-35 MPa sintering pressure and nitrogen atmosphere for 30-120 min.
5. A directionally solidified BN shell resistant to 1800 ℃ as claimed in claim 1, wherein said shell body (2) is formed by assembled butt-joint of a plurality of separately machined split components.
6. A directionally solidified BN shell resistant to 1800 ℃ according to claim 5, characterized in that said shell body (2) is formed by the assembly butt joint of a concave body (21) and a cover plate (22); the opening of the concave main body (21) is provided with a groove, and the cover plate (22) is inserted into the groove for positioning.
7. A directionally solidified BN shell resistant to 1800 ℃ according to claim 1, characterized in that the top of the shell base (1) is provided with a lower support structure extending towards the inside, the bottom of the pouring cup (3) is provided with an upper support structure extending towards the inside, and the shell body (2) is assembled between the upper support structure and the lower support structure.
8. A directionally solidified BN shell as claimed in claim 7 in which the upper support structure forms a central channel matching the shell body (2) and the lower support structure forms a central channel matching the shell body (2).
9. A directionally solidified BN shell having resistance to 1800 ℃ as claimed in claim 1, wherein mounting holes are provided on both sides of the shell body (2) for suspending cores to produce hollow turbine blades.
10. A directionally solidified BN shell resistant to 1800 ℃ as claimed in any one of claims 1 to 9, wherein the machining accuracy is not greater than ± 0.02mm.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202310731561.8A CN116765325A (en) | 2023-06-20 | 2023-06-20 | 1800 ℃ resistant directional solidification BN shell |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202310731561.8A CN116765325A (en) | 2023-06-20 | 2023-06-20 | 1800 ℃ resistant directional solidification BN shell |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN116765325A true CN116765325A (en) | 2023-09-19 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202310731561.8A Pending CN116765325A (en) | 2023-06-20 | 2023-06-20 | 1800 ℃ resistant directional solidification BN shell |
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| Country | Link |
|---|---|
| CN (1) | CN116765325A (en) |
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- 2023-06-20 CN CN202310731561.8A patent/CN116765325A/en active Pending
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