CN112676535B - Preparation method of ceramic shell for single crystal high-temperature alloy blade - Google Patents
Preparation method of ceramic shell for single crystal high-temperature alloy blade Download PDFInfo
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Abstract
The invention relates to a preparation method of a ceramic shell for a single crystal superalloy blade, wherein the ceramic shell is used for casting and forming the superalloy blade; the preparation method comprises the following steps: 1) coating surface layer slurry on the wax mould, and drying after coating to obtain a first surface layer of the ceramic shell on the wax mould; 2) coating and drying the first surface layer with the back layer slurry for N times to obtain a back layer of the ceramic shell on the first surface layer; after each coating and hanging of the back layer slurry is finished, firstly spreading sand grains on the coated and hung back layer slurry, and then carrying out drying treatment; the sand grains sprinkled on the back layer slurry coated at least one time from the 2 nd time to the N-1 st time are calcium carbonate sand grains; 3) coating the back layer with surface layer slurry, and drying the coated back layer to obtain a second surface layer of the ceramic shell on the back layer; 4) and (5) carrying out roasting treatment to obtain the ceramic shell. The method is mainly used for preparing the ceramic shell capable of inhibiting the interface reaction with the high-temperature alloy melt.
Description
Technical Field
The invention relates to the technical field of investment casting, in particular to a preparation method of a ceramic shell for a single crystal high-temperature alloy blade.
Background
Superalloy components are key components in aircraft engines and industrial gas turbines, and the microstructure of the superalloy component plays a very critical role in the efficiency of the engine. With the increase of the temperature of an air inlet of an engine, the temperature bearing capacity of a single crystal high-temperature alloy blade (namely, the engine blade) is higher and higher. In the preparation process of the single crystal high temperature alloy blade, a reaction layer or a sand-bonded layer and other surface defects are formed on the surface of a casting due to the interface reaction of the high temperature molten alloy, the ceramic shell and the core material, so that the surface quality of the casting is reduced, and the performance of the single crystal high temperature alloy blade in the service process is finally influenced.
Because the single crystal superalloy contains active elements such as carbon, yttrium, hafnium and the like, the elements are easy to react with a ceramic shell to form micro-porosity under a high-temperature condition. Therefore, the control of the micro-porosity formed by the interface reaction has important engineering significance for improving the surface quality of the casting and improving the performance of the single crystal high-temperature alloy blade.
At present, the interface reaction between the high-temperature alloy melt and the ceramic shell is inhibited mainly by filling inert gas into directional solidification equipment and reducing the vacuum degree of the equipment. However, this method of filling with inert gas is disadvantageous for vacuum systems
Disclosure of Invention
In view of the above, the present invention provides a method for preparing a ceramic shell for a single crystal superalloy blade, and the main objective of the present invention is to prepare a ceramic shell capable of inhibiting an interfacial reaction with a superalloy melt.
In order to achieve the purpose, the invention mainly provides the following technical scheme:
in one aspect, an embodiment of the present invention provides a method for preparing a ceramic shell for a single crystal superalloy blade, wherein the ceramic shell is used for casting the superalloy blade, and the method for preparing the ceramic shell comprises the following steps:
1) coating surface layer slurry on the wax mould, and drying after coating to obtain a first surface layer of the ceramic shell on the wax mould;
2) coating and drying the first surface layer with the back layer slurry for N times to obtain a back layer of the ceramic shell on the first surface layer;
after each coating and hanging of the back layer slurry is finished, firstly, sand grains are scattered on the coated and hung back layer slurry, and then, drying treatment is carried out;
wherein N is more than or equal to 3; wherein, when N equals 3: the material of the sand grains scattered on the back layer slurry coated at the 2 nd time is calcium carbonate; when N is greater than 3: the sand grains sprinkled on the back layer slurry coated at least one time from the 2 nd time to the N-1 st time are calcium carbonate sand grains;
3) coating the back layer with surface layer slurry, and drying the coated back layer to obtain a second surface layer of the ceramic shell on the back layer; wherein the first facing and the second facing form a facing of a ceramic shell;
4) and (4) dewaxing, and then roasting to obtain the ceramic shell.
Preferably, when the sand grains scattered on the coated back layer slurry are calcium carbonate sand grains, a plurality of plastic filament clusters are put into the scattered calcium carbonate sand grains; preferably, a plurality of the plastic clusters are uniformly distributed; preferably, the spacing between a plurality of the plastic clusters is 5-10 mm; preferably, the plastic wire ball is formed by winding plastic wires into a wire ball with the diameter of 0.3-0.5 mm. Preferably, the material of the plastic silk ball is polypropylene.
Preferably, when the sand particles sprinkled on the coated backing layer slurry are calcium carbonate sand particles: the purity of the calcium carbonate sand grains is more than 95 percent, and the granularity is 100-150 mu m.
Preferably, in the step 2): the sand grains scattered on the back layer slurry coated for the 1 st time and the Nth time are alumina sand grains; preferably, the alumina grit has a purity of greater than 95% and a particle size of 49-52 μm.
Preferably, in the step 2): the coating times N of the back layer slurry meet the following requirements: the backing layer of the ceramic shell was made 6-8 mm.
Preferably, in the step 2), when N is greater than 3: in the backing layer slurries of the 2 nd to N-1 st coating: the sand grains scattered on the back layer slurry coated for even times are calcium carbonate sand grains; the sand grains scattered on the back layer slurry coated for odd times are alumina sand grains; or the sand grains sprinkled on the back layer slurry coated from the 2 nd to the N-1 st time are all calcium carbonate sand grains.
Preferably, the surface layer slurry comprises alumina powder, silica sol, a defoaming agent and a bactericide; wherein the weight ratio of the silica sol to the alumina powder to the defoaming agent to the bactericide is 1: (2.8-4.0): (0.05-1.2): (0.1-1.0); preferably, the purity of the alumina powder is more than 95%;
preferably, the alumina powder comprises, in weight percent:
a first alumina powder having a particle size of 5 to 10 μm: 0.5-0.8 wt%;
a second alumina powder with a particle size of 80-100 μm: 1-1.5 wt%;
200-350 μm particle size of third alumina powder: the balance;
further preferably, the preparation method of the facing layer slurry is as follows:
1) after mixing the silica sol, the defoaming agent and the bactericide, stirring for 5-7min at the stirring speed of 100-150r/min to obtain a mixed solution;
2) adding the first alumina powder into the mixed solution, stirring for 10-15min, then sequentially adding the second alumina powder and the third alumina powder, and stirring to obtain a surface layer slurry; preferably, the stirring speed after the second aluminum oxide powder and the third aluminum oxide powder are added is 250-320r/min, and the stirring time is 60-90 min; preferably, the interval between the addition of the second aluminum oxide powder and the addition of the third aluminum oxide powder is 20 minutes or more.
Preferably, the backing layer slurry comprises silica sol and mullite powder; preferably, the mass ratio of the silica sol to the mullite powder is 1: (1.4-1.5).
Preferably, the drying treatment is performed in a vacuum system; preferably, the degree of vacuum in the drying treatment is 0.9X 10-1-1.1×10-1Pa。
Preferably, in the step 4): the roasting temperature is not more than 850 ℃, and the roasting time is 4-6 h.
Preferably, the ceramic shell is used for casting and forming the high-temperature alloy blade, wherein the ceramic shell comprises a surface layer and a back layer positioned in the surface layer; wherein the back layer has calcium carbonate particles therein; preferably, the surface layer comprises a first surface layer and a second surface layer, and the first surface layer is used for contacting the high-temperature alloy melt; the second surface layer is used for sealing and coating the back layer hung on the first surface layer; preferably, the back layer is also provided with plastic clusters.
Compared with the prior art, the preparation method of the ceramic shell for the single crystal superalloy blade at least has the following beneficial effects:
the invention provides a preparation method of a ceramic shell for a single crystal superalloy blade, which comprises the steps of firstly preparing a first surface layer of the ceramic shell, then preparing a back layer on the first surface layer, and then preparing a second surface layer on the back layer; here, when the back layer is prepared, N times of back layer slurry is coated, and the sand grains scattered on the back layer slurry coated 2 times (when N is equal to 3) or on the back layer slurry coated at least one time of 2 times to N-1 times (when N is greater than 3) are calcium carbonate sand grains, so that when the high temperature alloy melt is directionally solidified, the calcium carbonate sand grains in the ceramic shell are decomposed to generate gas (carbon dioxide gas) and permeate into a gap between the high temperature melt and the ceramic shell, thereby reducing the vacuum degree between the ceramic shell and the high temperature melt, and further reducing the interface reaction between the ceramic shell and the high temperature melt. And because the back layer is sealed by the second surface layer, the gas is prevented from entering the directional solidification equipment (vacuum equipment) as much as possible so as to avoid being unfavorable for the directional solidification equipment (argon is not good for a vacuum system, the gas generating from the shell is still sealed in the shell, and the vacuum degree of the equipment cannot be influenced).
Furthermore, according to the preparation method of the ceramic shell for the single crystal superalloy blade, N times of back layer slurry is coated and hung when the back layer is prepared, and the sand grains sprayed on the 1 st and N times of coated back layer slurry are alumina sand grains, so that the strength of the first surface layer, the second surface layer and the whole ceramic shell can be ensured, the ceramic shell is not deformed at high temperature, and the function of controlling the size of the engine blade is achieved.
Furthermore, according to the preparation method of the ceramic shell for the single crystal superalloy blade, a plurality of plastic filament clusters are placed in calcium carbonate sand grains scattered in the coated backing layer slurry, so that when the high-temperature alloy melt is directionally solidified, the plastic filament clusters in the ceramic shell are melted under the action of high temperature, a channel is formed in the backing layer, and gas decomposed from the calcium carbonate sand grains is uniformly distributed through the channel.
In conclusion, the invention solves the problem of micro shrinkage porosity caused by interface reaction in the precision casting process of the single crystal superalloy blade; the invention has the advantages of reasonable design, simple operation process and low cost.
The foregoing description is only an overview of the technical solutions of the present invention, and in order to make the technical solutions of the present invention more clearly understood and to implement them in accordance with the contents of the description, the following detailed description is given with reference to the preferred embodiments of the present invention and the accompanying drawings.
Drawings
FIG. 1 is a schematic structural diagram of a ceramic shell for a single crystal blade according to an embodiment of the present invention;
FIG. 2 is a schematic view of a single crystal blade formed using a ceramic shell prepared in example 3;
FIG. 3 is a schematic view of a single crystal blade formed using a conventional ceramic shell mold.
Detailed Description
To further explain the technical means and effects of the present invention adopted to achieve the predetermined object, the following detailed description of the embodiments, structures, features and effects according to the present invention will be made with reference to the accompanying drawings and preferred embodiments. In the following description, different "one embodiment" or "an embodiment" refers to not necessarily the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.
On one hand, the embodiment of the invention provides a preparation method of a ceramic shell for a single crystal superalloy blade, which mainly comprises the following steps:
1) and coating the wax mould with surface layer slurry, and drying after coating to obtain a first surface layer of the ceramic shell on the wax mould.
Specifically, in the step, the wax mould is placed into the surface layer slurry for coating, and then the coated wax mould is placed into a vacuum system for drying; the vacuum degree of the vacuum system is 1 x 10-1pa。
The first surface layer of the ceramic shell is here intended primarily for contact with the superalloy melt.
2) And coating and drying the first surface layer with the back layer slurry for N times to obtain the back layer of the ceramic shell on the first surface layer.
Specifically, the wax mould coated with the first surface layer is placed into the back layer slurry for coating, then sand grains are scattered, drying treatment is carried out, and the steps are repeated for N times.
Wherein N is more than or equal to 3; wherein, when N equals 3: the material of the sand grains scattered on the back layer slurry coated at the 2 nd time is calcium carbonate; when N is greater than 3: the sand grains sprinkled on the back layer slurry coated at least one time from the 2 nd to the N-1 st times are calcium carbonate sand grains.
Preferably, in step 2): the sand grains scattered on the back layer slurry coated for the 1 st time and the Nth time are alumina sand grains; preferably, the alumina grit has a purity of greater than 95% and a particle size of 49-52 μm.
Preferably, in step 2), when N is greater than 3:
in the back layer slurry coated from the 2 nd time to the N-1 st time, the sand grains spread on the back layer slurry coated from the even number of times are calcium carbonate sand grains; the sand grains scattered on the back layer slurry coated for odd times are alumina sand grains. Or the sand grains sprinkled on the back layer slurry coated from the 2 nd to the N-1 st time are all calcium carbonate sand grains.
Preferably, in the step 2): the coating times N of the back layer slurry meet the following requirements: the backing layer of the ceramic shell was made 6-8 mm.
Preferably, in the step 2): when the sand grains scattered on the coated back layer slurry are calcium carbonate sand grains, a plurality of plastic filament clusters are put into the scattered calcium carbonate sand grains; the spacing between the plastic filament groups is 5-10 mm; the plastic wire ball is formed by winding plastic wires into wire balls with the diameter of 0.3-0.5 mm.
Preferably, when the sand particles sprinkled on the coated backing layer slurry are calcium carbonate sand particles: the purity of the calcium carbonate sand grains is more than 95 percent, and the granularity is 100-150 mu m.
Here, it should be noted that: on one hand, the back layer mainly improves the high-temperature strength of the ceramic shell, so that the ceramic shell is not deformed at high temperature and plays a role in controlling the size of the blade; and the strength of the ceramic shell can be further improved through the alumina sand grains. On the other hand, the key invention of the application is that calcium carbonate sand grains are scattered; thus, when the finally prepared ceramic shell is directionally solidified with the high-temperature alloy melt, the calcium carbonate sand grains are decomposed at high temperature to generate gas, and the gas can inhibit the interface reaction between the ceramic shell and the high-temperature alloy melt; and since the backing layer is sealed by the second facing layer, as little as possible of this gas will enter the vacuum system, thereby reducing the disadvantages to the vacuum system. In addition, by the effect of putting a plurality of plastic clusters in the sand grains of calcium carbonate, mainly the plastic clusters melt at high temperature, thereby forming channels inside the back layer of the ceramic shell, so that the gas of calcium carbonate pyrolysis is uniformly distributed through the channels.
Therefore, the present application sets "the N.gtoreq.3; wherein, when N equals 3: the material of the sand grains scattered on the back layer slurry coated at the 2 nd time is calcium carbonate; when N is greater than 3: the sand grains sprinkled on the back layer slurry coated at least one time from the 2 nd to the N-1 st times are calcium carbonate sand grains "; the effect of inhibiting the interface reaction between the ceramic shell and the high-temperature alloy melt is further ensured on the basis of ensuring the surface layer and the ceramic shell.
3) Coating and hanging the back layer with surface layer slurry, and then drying the back layer to obtain a second surface layer of the ceramic shell on the back layer; wherein the first facing and the second facing form a facing of a ceramic shell.
In the step, the wax mould coated with the first surface layer and the back layer in sequence is put into the surface layer slurry for coating, and the coating times are 1-2 times. The second surface layer is applied here in order to seal the back layer and prevent gases formed by the reaction in the mould shell from being released into the vacuum furnace.
4) And (4) dewaxing, and then roasting to obtain the ceramic shell.
In the step, the temperature of the roasting treatment is not more than 850 ℃ and the time is 4-6 h.
In another aspect, embodiments of the present invention also provide a ceramic shell, wherein the ceramic shell is used for casting and forming a superalloy blade, in particular for forming a single crystal superalloy blade. Therein, referring to fig. 1, a ceramic shell comprises a facing layer 1 and a backing layer 2 located within the facing layer 1; wherein, the back layer 2 is internally provided with calcium carbonate particles 3; the backing layer 2 is also provided with plastic clusters 4 inside. The facing 1 comprises a first facing 11 for contacting the superalloy melt and a second facing 12 for enclosing the backing 2. Here, the ceramic shell is prepared by any one of the above-described methods for preparing a ceramic shell.
In addition, when the ceramic shell prepared or provided by the embodiment of the invention is adopted to carry out directional solidification on the high-temperature alloy melt, the vacuum degree of investment casting is controlled to be 10-1-10-2pa。
The invention is further illustrated by the following specific experimental examples:
example 1
This example prepared a ceramic shell for a single crystal blade, and directionally solidified a nickel-based single crystal superalloy melt into a single crystal superalloy blade (engine blade) in a directional solidification apparatus using the ceramic shell as a shell. The components of the nickel-based single crystal superalloy melt are shown in table 1.
TABLE 1 weight percent (wt%) of elements in the nickel-based single crystal superalloy melt
| C | Cr | Mo | Al | W | Ti | Ta | Co | Ni |
| 0.15 | 8.0 | 2.0 | 5.6 | 5.0 | 1.0 | 4.0 | 6.0 | Balance of |
Preparing surface layer slurry: the raw materials for preparing the surface layer slurry are as follows: the weight ratio is 1: (2.8): (0.05): (0.1) silica sol, alumina powder, defoaming agent and bactericide. Wherein the alumina powder has different particle sizes, wherein the particle size of 5 μm accounts for 0.5 wt%, the particle size of 80 μm accounts for 1 wt%, and the rest particle size is 200 μm. Firstly, putting the silica sol, the defoaming agent and the bactericide into a stirring barrel, and stirring for 5min at a stirring speed of 100r/min to uniformly mix the solution. Then putting the alumina powder with the particle size of 5 mu m (the purity is more than 95%) into a stirring barrel, and stirring for 10min to ensure that the fine powder is fully distributed in the mixed solution to prevent clustering. And finally, sequentially adding alumina powder with the granularity of 80 microns and alumina powder with the granularity of 200 microns (the discharge interval of the two is more than 60 minutes) into the mixed solution, wherein the stirring speed is 250r/min, and the stirring time is 60 minutes, so as to obtain the surface layer slurry.
Preparing a first surface layer: putting the wax mould into the surface layer slurry for coating, putting the wax mould into a vacuum box, and vacuumizing to 1 multiplied by 10-1And pa, drying to obtain a first surface layer of the ceramic shell on the wax mold.
Preparing a back layer: the wax pattern was placed in a back layer slurry obtained by uniformly mixing silica sol and mullite powder in a mass ratio of 1:1.5, and the first surface layer was coated with the back layer slurry and dried 6 times to obtain a back layer of a ceramic shell (the back layer had a thickness of 6mm) on the first surface layer. After each coating and hanging of the back layer slurry is finished, firstly, sand grains are scattered on the coated and hung back layer slurry, and then, drying treatment is carried out;
wherein, on the back layer slurry coated at the 1 st, 3 rd, 5 th and 6 th times, the sand grains are aluminum oxide sand grains with the grain size of 50 μm, so that certain gaps are formed in the shell. On the back layer slurry coated in the 2 nd and 4 th times, the sand grains are calcium carbonate sand grains with the grain size of 100 mu m, a plurality of plastic clusters with the diameter of 0.3mm are evenly placed in the calcium carbonate sand grains at intervals, and the distance between the clusters is 5 mm.
Preparing a second surface layer: coating the back layer with the surface layer slurry, and drying after coating (coating and drying times are 1 time), so as to obtain a second surface layer of the ceramic shell on the back layer; wherein the first facing and the second facing form a facing of the ceramic shell.
Roasting: after dewaxing, carrying out roasting treatment to obtain a ceramic shell; wherein the roasting temperature is 850 ℃ and the roasting time is 4 hours.
Directional solidification: in a directional solidification device, the ceramic shell prepared above is used as a shell, and the single crystal high temperature alloy melt with the components shown in table 1 is subjected to directional solidification treatment to obtain the single crystal high temperature alloy blade. Wherein, during directional solidification, the vacuum degree of investment casting is controlled to be 10-1pa。
Example 2
This example prepared a ceramic shell for a single crystal blade, and directionally solidified a nickel-based superalloy melt into a superalloy blade (engine blade) in a directional solidification apparatus using the ceramic shell as a shell. The composition of the nickel-base superalloy melt is shown in table 2.
TABLE 2 weight percent (wt%) of elements in the nickel-base superalloy melt
| C | Hf | Cr | Co | Al | Ti | W | Ta | Nb | Ni |
| 0.05 | 1.0 | 9.0 | 6.0 | 5.5 | 1.0 | 9.5 | 3.0 | 1.0 | Surplus |
Preparing surface layer slurry: the raw materials for preparing the surface layer slurry are as follows: the weight ratio is 1: (4.0): (1.2): (1.0) silica sol, alumina powder, defoaming agent and bactericide. Wherein the alumina powder has different particle sizes, wherein the particle size of 10 μm accounts for 0.8 wt%, the particle size of 100 μm accounts for 1.5 wt%, and the rest is 350 μm. Firstly, putting the silica sol, the defoaming agent and the bactericide into a stirring barrel, and stirring for 7min at a stirring speed of 150r/min to uniformly mix the solution. Then putting the alumina powder with the particle size of 10 mu m (the purity is more than 95%) into a stirring barrel, and stirring for 15min to ensure that the fine powder is fully distributed in the mixed solution to prevent clustering. And finally, sequentially adding alumina powder with the granularity of 100 mu m and alumina powder with the granularity of 350 mu m into the mixed solution (the discharge interval of the two is more than 40 minutes), wherein the stirring speed is 320r/min, and the stirring time is 90min, so as to obtain the surface layer slurry.
Preparing a first surface layer: putting the wax mould into the surface layer slurry for coating, putting the wax mould into a vacuum box, and vacuumizing to 1 multiplied by 10-1pa, reducing the formation of bubbles in the first surface layer, and drying to obtain the first surface layer of the ceramic shell on the wax mould.
Preparing a back layer: the wax mold is placed into back layer slurry, silica sol and mullite powder are uniformly mixed according to the mass ratio of 1:1.4, the first surface layer is coated and dried 7 times, and the back layer of the ceramic shell is obtained on the first surface layer (the thickness of the back layer is 8 mm). After each coating and hanging of the back layer slurry is finished, firstly, sand grains are scattered on the coated and hung back layer slurry, and then, drying treatment is carried out;
wherein, on the back layer slurry coated at the 1 st, 3 rd, 5 th and 7 th times, the sand grains are aluminum oxide sand grains with the grain size of 50 μm, so that certain gaps are formed in the shell. On the back layer slurry coated in the 2 nd, 4 th and 6 th times, the sand grains are calcium carbonate sand grains with the grain size of 150 mu m, a plurality of plastic clusters with the diameter of 0.5mm are evenly placed in the calcium carbonate sand grains at intervals, and the distance between the clusters is 10 mm.
Preparing a second surface layer: coating the back layer with the surface layer slurry, and drying after coating (coating and drying times are 2 times), so as to obtain a second surface layer of the ceramic shell on the back layer; wherein the first facing and the second facing form a facing of the ceramic shell.
Roasting: after dewaxing, carrying out roasting treatment to obtain a ceramic shell; wherein the roasting temperature is 820 ℃ and the roasting time is 6 h.
Directional solidification: in the directional solidificationIn the equipment, the ceramic shell prepared above is used as a shell, and directional solidification treatment is carried out on the high-temperature alloy melt with the components shown in table 2, so as to obtain the high-temperature alloy blade. Wherein, during directional solidification, the vacuum degree of investment casting is controlled to be 10-2pa。
Example 3
This example prepared a ceramic shell for a single crystal blade and directionally solidified a nickel-based superalloy melt into a superalloy blade in a directional solidification apparatus using the ceramic shell as the shell. The composition of the nickel-base superalloy melt is shown in table 3.
TABLE 3 weight percent (wt%) of elements in the nickel-based single crystal superalloy melt
| C | Mo | Cr | Co | Al | Hf | W | Ta | Re | Y | Ni |
| 0.045 | 1.5 | 7.0 | 8.0 | 6.2 | 0.15 | 5.0 | 6.5 | 3.0 | 0.02 | Surplus |
Preparing surface layer slurry: the raw materials for preparing the surface layer slurry are as follows: the weight ratio is 1: (3.3): (1): (0.5) silica sol, alumina powder, defoaming agent and bactericide. The alumina powder had different particle sizes, with 8 μm of particle size accounting for 0.7 wt%, 90 μm of particle size accounting for 1.3 wt%, and the remainder being 280 μm. Firstly, putting the silica sol, the defoaming agent and the bactericide into a stirring barrel, and stirring for 6min at a stirring speed of 120r/min to uniformly mix the solution. Then putting the alumina powder with the particle size of 8 mu m (the purity is more than 95%) into a stirring barrel, and stirring for 12min to ensure that the fine powder is fully distributed in the mixed solution to prevent clustering. And finally, sequentially adding alumina powder with the granularity of 90 mu m and alumina powder with the granularity of 330 mu m into the mixed solution (the feeding interval of the two is more than 50 minutes), wherein the stirring speed is 290r/min, and the stirring time is 70min, so as to obtain the surface layer slurry.
Preparing a first surface layer: putting the wax mould into the surface layer slurry for coating, putting the wax mould into a vacuum box, and vacuumizing to 1 multiplied by 10-1And pa, drying to obtain a first surface layer of the ceramic shell on the wax mold.
Preparing a back layer: the wax pattern was put into a back layer slurry obtained by uniformly mixing silica sol and mullite powder at a ratio of 1:1.5, and the first surface layer was coated with the back layer slurry and dried 7 times to obtain a back layer of a ceramic shell (thickness of the back layer: 7mm) on the first surface layer. After each coating and hanging of the back layer slurry is finished, firstly, sand grains are scattered on the coated and hung back layer slurry, and then, drying treatment is carried out;
wherein, on the back layer slurry coated at the 1 st, 3 rd, 5 th and 7 th times, the sand grains are aluminum oxide sand grains with the grain size of 50 μm, so that certain gaps are formed in the shell. On the back layer slurry coated in the 2 nd, 4 th and 6 th times, the sand grains are calcium carbonate sand grains with the grain size of 120 mu m, a plurality of plastic clusters with the diameter of 0.4mm are evenly placed in the calcium carbonate sand grains at intervals, and the space between the clusters is 8 mm.
Preparing a second surface layer: coating the back layer with the surface layer slurry, and drying after coating (coating and drying times are 2 times), so as to obtain a second surface layer of the ceramic shell on the back layer; wherein the first facing and the second facing form a facing of the ceramic shell.
Roasting: after dewaxing, carrying out roasting treatment to obtain a ceramic shell; wherein the roasting temperature is 800 ℃, and the roasting time is 5 h.
Directional solidification: in a directional solidification device, the ceramic shell prepared as described above was used as a shell, and a high temperature alloy melt having the composition shown in table 3 was subjected to directional solidification treatment to obtain a high temperature alloy blade (see fig. 2). Wherein, during directional solidification, the vacuum degree of investment casting is controlled to be 10-2pa。
Wherein, fig. 2 is a schematic view of the single crystal blade prepared in example 3.
The high temperature alloy melt with the components shown in table 3 was subjected to directional solidification treatment using a conventional ceramic shell to obtain a high temperature alloy blade (single crystal blade) as shown in fig. 3.
As is evident from fig. 2 and 3: the single crystal blade shown in fig. 3 (a single crystal blade formed by using a conventional ceramic shell) is uneven, has a large amount of bonded sand, and has poor surface quality; the single crystal blade shown in fig. 2 (the single crystal blade formed by the ceramic shell prepared by the embodiment of the invention) has uniform structure and good surface quality.
In conclusion, the ceramic shell prepared by the method can obviously reduce the formation of the micro-porosity of the single crystal superalloy blade.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention in any way, and any simple modification, equivalent change and modification made to the above embodiment according to the technical spirit of the present invention are still within the scope of the technical solution of the present invention.
Claims (25)
1. A preparation method of a ceramic shell for a single crystal superalloy blade is provided, wherein the ceramic shell is used for casting and forming the superalloy blade, and is characterized by comprising the following steps:
1) coating surface layer slurry on the wax mould, and drying after coating to obtain a first surface layer of the ceramic shell on the wax mould;
2) coating and drying the first surface layer with the back layer slurry for N times to obtain a back layer of the ceramic shell on the first surface layer;
after each coating and hanging of the back layer slurry is finished, firstly, sand grains are scattered on the coated and hung back layer slurry, and then, drying treatment is carried out;
wherein N is more than or equal to 3; wherein, when N equals 3: the material of the sand grains scattered on the back layer slurry coated at the 2 nd time is calcium carbonate; when N is greater than 3: the sand grains sprinkled on the back layer slurry coated at least one time from the 2 nd time to the N-1 st time are calcium carbonate sand grains;
3) coating the back layer with surface layer slurry, and drying the coated back layer to obtain a second surface layer of the ceramic shell on the back layer; wherein the first facing and the second facing form a facing of a ceramic shell;
4) and (4) dewaxing, and then roasting to obtain the ceramic shell.
2. The method for preparing a ceramic shell for a single crystal superalloy blade of claim 1, wherein in step 2): when the sand grains scattered on the coated back layer slurry are calcium carbonate sand grains, a plurality of plastic filament clusters are put into the scattered calcium carbonate sand grains.
3. The method of preparing a ceramic shell mold for a single crystal superalloy blade of claim 2, wherein the plurality of plastic clusters are uniformly distributed.
4. The method of preparing a ceramic shell mold for a single crystal superalloy blade of claim 2, wherein a spacing between the plurality of plastic clusters is 5-10 mm.
5. The method of preparing a ceramic shell mold for a single crystal superalloy blade of claim 2, wherein the plastic wire mass is a wire mass wound from plastic wire to a diameter of 0.3-0.5 mm.
6. The method of claim 2, wherein the plastic clusters are made of polypropylene.
7. The method of manufacturing a ceramic shell mold for a single crystal superalloy blade of claim 2, wherein when the grit sprinkled on the coated backing slurry is calcium carbonate grit: the purity of the calcium carbonate sand grains is more than 95 percent, and the granularity is 100-150 mu m.
8. The method for preparing a ceramic shell for a single crystal superalloy blade according to any of claims 1 to 7, wherein in step 2):
the sand grains sprinkled on the back layer slurry coated at the 1 st and the Nth times are alumina sand grains.
9. The method of preparing a ceramic shell mold for a single crystal superalloy blade of claim 8, wherein the alumina grit has a purity of greater than 95% and a particle size of 49-52 μm.
10. The method of manufacturing a ceramic shell mold for a single crystal superalloy blade according to claim 8, wherein the number of coating times N of the back layer slurry satisfies: the thickness of the back layer of the ceramic shell is 6-8 mm.
11. The method for preparing a ceramic shell for a single crystal superalloy blade of claim 8, wherein in step 2), when N is greater than 3:
in the backing layer slurries of the 2 nd to N-1 st coating: the sand grains scattered on the back layer slurry coated for even times are calcium carbonate sand grains; the sand grains scattered on the back layer slurry coated for odd times are alumina sand grains; or
The sand grains sprinkled on the back layer slurry coated from the 2 nd to the N-1 st are all calcium carbonate sand grains.
12. The method for preparing a ceramic shell for a single crystal superalloy blade of claim 1, wherein the surface layer slurry comprises alumina powder, silica sol, a defoaming agent, a bactericide; wherein the content of the first and second substances,
the weight ratio of the silica sol to the alumina powder to the defoaming agent to the bactericide is 1: (2.8-4.0): (0.05-1.2): (0.1-1.0).
13. The method of preparing a ceramic shell for a single crystal superalloy blade of claim 12, wherein the alumina powder has a purity of greater than 95%.
14. The method of preparing a ceramic shell mold for a single crystal superalloy blade of claim 13, wherein the alumina powder comprises, in weight percent:
a first alumina powder having a particle size of 5 to 10 μm: 0.5-0.8 wt%;
a second alumina powder with a particle size of 80-100 μm: 1-1.5 wt%;
200-350 μm particle size of third alumina powder: and (4) the balance.
15. The method of preparing a ceramic shell mold for a single crystal superalloy blade of claim 14, wherein the facecoat slurry is formulated as follows:
1) after mixing the silica sol, the defoaming agent and the bactericide, stirring for 5-7min at the stirring speed of 100-150r/min to obtain a mixed solution;
2) and adding the first alumina powder into the mixed solution, stirring for 10-15min, then sequentially adding the second alumina powder and the third alumina powder, and stirring to obtain the surface layer slurry.
16. The method of preparing a ceramic shell mold for a single crystal superalloy blade of claim 15,
the stirring speed is 250-320r/min and the stirring time is 60-90min after the second aluminum oxide powder and the third aluminum oxide powder are added; and/or
The adding interval of the second aluminum oxide powder and the third aluminum oxide powder is more than 20 minutes.
17. The method of preparing a ceramic shell for a single crystal superalloy blade of claim 1, wherein the backing layer slurry comprises silica sol and mullite powder.
18. The method of preparing a ceramic shell for a single crystal superalloy blade of claim 17, wherein the mass ratio of silica sol to mullite powder is 1: (1.4-1.5).
19. The method of preparing a ceramic shell for a single crystal superalloy blade of claim 1, wherein the drying is performed in a vacuum apparatus.
20. The method of preparing a ceramic shell for a single crystal superalloy blade of claim 19, wherein the degree of vacuum of the drying process is 0.9 x 10-1-1.1×10-1Pa。
21. The method for preparing a ceramic shell for a single crystal superalloy blade of claim 1, wherein in step 4): the temperature of the roasting treatment is not more than 850 ℃; the roasting time is 4-6 h.
22. The method for preparing a ceramic shell for a single crystal superalloy blade of claim 1, wherein in step 4): the temperature of the roasting treatment is 830-850 ℃.
23. The method of making a ceramic shell for a single crystal superalloy blade of any of claims 1-7 and 12-22, wherein the ceramic shell is used for cast forming of the superalloy blade, wherein the ceramic shell comprises a facing layer and a backing layer within the facing layer; wherein the back layer has calcium carbonate particles therein.
24. The method of making a ceramic shell for a single crystal superalloy blade of claim 23, wherein the facing comprises a first facing and a second facing, the first facing for contacting a superalloy melt; the second facing is used to seal the backing layer suspended from the first facing.
25. The method of claim 24, wherein the backing layer further comprises a plastic filament mass.
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