CN115846596A - Superalloy directional solidification mold core and preparation method thereof - Google Patents
Superalloy directional solidification mold core and preparation method thereof Download PDFInfo
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Abstract
The invention relates to a superalloy directional solidification mold core and a preparation method thereof, and belongs to the technical field of ceramic mold core manufacturing. The preparation method of the superalloy directional solidification core comprises the following steps: s1, dry powder preparation: uniformly mixing 0.5-2% of active powder by mass fraction and the rest of matrix powder, and drying after mixing and stirring to obtain dry powder; s2, preparing wet powder: heating and melting the plasticizer accounting for 19-25% of the mass fraction of the dry powder in the step S1, adding the dry powder obtained in the step S1 after melting, and mixing and stirring at a constant temperature to obtain wet powder; s3, pressing a superalloy directional solidification core: and (3) pressing and injecting the wet powder obtained in the step (S2) to obtain a wet core, trimming and sizing the wet core, putting the wet core into a burning pot filled with fillers, sintering, keeping the temperature for 3-8h after sintering, and cooling to room temperature to obtain the superalloy directional solidification core. Has the advantages that: the method has the advantages of high room temperature strength, high temperature strength and good high temperature creep resistance, and can effectively improve the yield and the service performance of the superalloy directional solidification mold core.
Description
Technical Field
The invention belongs to the technical field of ceramic core manufacturing, and particularly relates to a superalloy directional solidification core and a preparation method thereof.
Background
The temperature of the turbine inlet of the aircraft engine can reach 1800K-2300K, which is far beyond the melting point of the high-temperature alloy for the engine. In the face of such a complex use environment, the engine blades must employ advanced cooling techniques to reduce the temperature of the blades. The early high-temperature alloy cast blades are solid blades without adopting a cooling technology, and the front inlet temperature of the turbine is limited by the blade material and is difficult to exceed 1050 ℃. Therefore, since the 60's of the twentieth century, the cooling technology of the hollow blade was internationally developed to improve the cooling effect. At present, a hollow blade is generally formed by adopting an investment precision casting mode, and an inner cavity of the blade is formed by using a ceramic core in a pouring process. Because the pouring conditions are harsh, the requirements on the performance of the ceramic core are extremely strict. The ceramic cores for high-temperature alloy precision investment casting are mainly divided into alumina-based cores and silica-based cores internationally, and the alumina-based cores are rarely researched and lack of effective core removing methods domestically, so that the oxidized superalloy directional solidification cores are mostly used.
Because the superalloy directional solidification core has weak high-temperature strength and high-temperature creep tendency, the use performance of the ceramic core must be strictly controlled and properly enhanced. At present, the preparation of the superalloy directional solidification mold core generally uses electric melting quartz glass powder as a base material, a mineralizer is used for reinforcement, the performance of the mold core in all aspects is properly enhanced, most of the mineralizer is selected to be zirconium silicate, and the addition amount can reach 20% -30%. Although the addition of the zirconium silicate can improve the high-temperature performance of the superalloy directional solidification core, the zirconium silicate is not easily removed by alkali liquor as silicon oxide, so that the removal efficiency of the superalloy directional solidification core is greatly reduced due to the existence of the zirconium silicate. The DS core is a ceramic core which takes high-purity quartz glass powder as a base material, takes active powder as an auxiliary material and takes cristobalite as a main crystal phase. The method is characterized by strong high-temperature creep resistance, and can be used for directional solidification casting and single crystal casting of the superalloy with the casting temperature higher than 1600 ℃; the dissolution property is excellent, and the method can be used for casting with a complex cavity structure.
Because the DS core forms more cristobalite crystal phases in the sintering process, the volume of the cristobalite crystal phases is changed due to phase change in the cooling process, microcracks are generated inside the core, and the sintering room temperature strength of the ceramic core is influenced, so the sintering strength of the DS core is generally low and only 4-8MPa, the low room temperature strength seriously influences the sand cleaning and mould repairing processes after sintering, and the core is easily damaged, and the yield and the production efficiency are influenced. In addition, although the DS core is excellent in high temperature creep resistance, the high temperature strength is often not high due to internal microcracks, and is susceptible to core breakage caused by molten metal impact during casting. Therefore, the development of the high-performance superalloy directional solidification core with high room temperature strength and high temperature strength has positive significance.
Disclosure of Invention
The invention provides a preparation method of a superalloy directional solidification mold core for solving the technical problems, which has the advantages of high room temperature strength, high temperature strength and good high temperature creep resistance, and can effectively improve the yield and the service performance of a DS mold core.
The technical scheme for solving the technical problems is as follows: a preparation method of a superalloy directional solidification core comprises the following steps of S1, dry powder preparation: uniformly mixing 0.5-2% of active powder by mass fraction and the rest of matrix powder, and drying after mixing and stirring to obtain dry powder; s2, preparing wet powder: heating and melting the plasticizer accounting for 19-25% of the mass fraction of the dry powder in the step S1, adding the dry powder obtained in the step S1 after melting, and mixing and stirring at a constant temperature to obtain wet powder; s3, pressing a superalloy directional solidification core: and (3) pressing and injecting the wet powder obtained in the step (S2) to obtain a wet core, trimming and sizing the wet core, putting the wet core into a burning pot filled with fillers, sintering, keeping the temperature for 3-8h after sintering, and cooling to room temperature to obtain the superalloy directional solidification core.
The principle of the preparation method of the superalloy directional solidification core of the invention is explained as follows:
the higher the purity of the quartz glass powder is, the less impurities are contained in the powder, the more difficult the powder is to sinter, and the less cristobalite is converted in the sintering process, but due to the lower impurity content, the high-purity quartz powder forms less low-melting-point liquid-phase compound with the impurities in the temperature rising process, so that the refractoriness is greatly improved, and the core can have good high-temperature creep resistance without depending on excessive cristobalite phases in the core. The purity of the quartz powder used in the invention is as high as 99.99%, the capability of converting into cristobalite in the sintering process is weak, the sintering driving force of the mold core can be improved by controlling the particle size distribution of the powder and properly using the powder with the particle size of 10um, and the proper sintering temperature is controlled, so that the mold core obtains a certain sintering degree and ensures the corresponding strength, meanwhile, the content of the cristobalite in the mold core is low after sintering is finished, and the strength performance is not deteriorated in the cooling process, thereby ensuring the high room temperature strength, the high temperature strength and the good high temperature creep resistance of the mold core.
Has the advantages that: the high-temperature-resistant DS mold core has the advantages of high room-temperature strength, high-temperature strength and good high-temperature creep resistance, and can effectively improve the yield and the service performance of the DS mold core.
On the basis of the technical scheme, the invention can be further improved as follows.
Further, in step S1, the active powder is any one of 300-500 mesh sodium silicate, sodium-containing silica gel dry powder or water glass dry powder.
Further, in step S1, the base powder is high-purity quartz glass powder, wherein S iO 2 The content reaches more than 99.99 percent.
Further, in step S1, the high-purity quartz glass powder is formed by mixing three kinds of high-purity quartz glass powders with D50 of 65um, 30um and 10um, and the mixing ratio of the three kinds of quartz glass powders is 10% -40%, 20% -50% and 20% -40%, respectively.
Further, in the step S1, the mixing and stirring time is not less than 4h, the drying temperature is 100-150 ℃, and the drying time is not less than 4h.
Further, in step S2, the plasticizer is a mixture of paraffin, stearic acid, and polyethylene.
Further, in step S2, the melting temperature is 100-130 ℃; the mixing and stirring time is not less than 24h, and the constant temperature range is 100-130 ℃.
Further, in step S3, the injection temperature is 80-100 ℃, the injection pressure is 1-7MPa, and the injection time is 5-15S.
Further, in step S3, the filler is kaolin or calcined alumina.
The second purpose of the invention is to provide the superalloy directional solidification core prepared by the preparation method.
Has the advantages that: the superalloy directional solidification core has the advantages of high room temperature strength, high temperature strength and good high temperature creep resistance.
Detailed Description
The principles and features of this invention are described below in conjunction with examples which are set forth to illustrate, but are not to be construed to limit the scope of the invention.
Example 1:
325 mesh sodium silicate powder and high-purity quartz glass powder with the S iO2 content of more than 99.99 percent are used as raw materials to prepare a core dry material, wherein the sodium silicate content is 0.5 percent, the rest is formed by mixing three high-purity quartz glass powders with D50 of 65um, 30um and 10um, and the mixing proportion of the three powders is 10 percent, 50 percent and 40 percent;
the plasticizer was prepared in an amount of 20% of the total dry powder, and the ratio of paraffin, stearic acid and polyethylene in the plasticizer was 85%, 10% and 5%, respectively.
Dry mixing: and (3) uniformly mixing all the weighed raw material powder in a mixer for 4 hours. And after the mixing is finished, placing the powder in a drying oven at 100 ℃ for drying for later use, wherein the drying time is 4 hours.
Wet mixing: and (3) putting the weighed plasticizer into a wet mixer, heating to melt, controlling the melting temperature at 130 ℃, gradually adding the mixed dry powder with the temperature of 130 ℃ into the melted accelerator in batches after melting, and stirring for 24 hours at the constant temperature of 130 ℃ to obtain the wet material.
Pressing: and (3) putting the wet material into a core pressing and injecting machine, and pressing the ceramic core under the process parameters of injection temperature of 100 ℃, injection pressure of 5MPa, injection time of 15s and pressure maintaining time of 10 s.
Core trimming and shaping: and finishing and shaping the wet core, and then sintering.
Loading a pot: the wet core was placed in an alumina beaker with kaolin filler, the core was 2cm from the bowl wall, 3cm from the bowl bottom, and 2cm core spacing, and the sagger was placed on a vibrating table and vibrated for 15s.
And (3) sintering: and (3) putting the burning pot with the mold core into a high-temperature sintering furnace, wherein the sintering schedule is that the temperature is increased to 150 ℃ at 1 ℃/min, is increased to 400 ℃ at 0.5 ℃/min, is increased to 700 ℃ at 2 ℃/min, is increased to 1250 ℃ at 5 ℃/min, is kept for 4h, and is cooled to room temperature along with the furnace.
And (3) testing: the cores were tested for room temperature strength, high temperature strength and high temperature deflection as per HB5353.3-2004 and HB5353.4-2004, respectively, and the test results are shown in Table 1.
Example 2:
silica gel powder containing sodium and high-purity quartz glass powder with the S iO2 content of more than 99.99 percent are used as raw materials to prepare a core dry material, wherein the silica gel dry powder content is 1.5 percent, the balance is formed by mixing three high-purity quartz glass powders with D50 of 65um, 30um and 10um, and the mixing proportion of the three powders is 20 percent, 40 percent and 40 percent.
The plasticizer was prepared in an amount of 20% of the total amount of the above dry powder, and the ratio of paraffin, stearic acid and polyethylene in the plasticizer was 85%, 10% and 5%, respectively.
Dry mixing: and (3) uniformly mixing all the weighed raw material powder in a mixer for 4 hours. And after the mixing is finished, placing the powder in a drying oven at 120 ℃ for drying for later use, wherein the drying time is 4 hours.
Wet mixing: and (3) putting the weighed plasticizer into a wet mixer, heating to melt, controlling the melting temperature at 120 ℃, gradually adding the mixed dry powder with the temperature of 120 ℃ into the melted accelerator in multiple times after melting, and stirring for 24 hours at the constant temperature of 120 ℃ to obtain the wet material.
Pressing: and (3) putting the wet material into a core pressing and injecting machine, and pressing the ceramic core under the process parameters of injection temperature of 90 ℃, injection pressure of 6MPa, injection time of 15s and pressure maintaining time of 10 s.
Core trimming and shaping: and finishing and shaping the wet core, and then sintering.
Loading a pot: the wet core was placed in an alumina beaker with calcined alumina, the core was 2cm from the bowl wall, 3cm from the bowl bottom, and the core spacing was 2cm, and the sagger was placed on a vibrating table and vibrated for 15s.
And (3) sintering: and (3) putting the burning pot with the core into a high-temperature sintering furnace, wherein the sintering schedule is that the temperature is increased to 200 ℃ at the speed of 2 ℃/min, is increased to 400 ℃ at the speed of 1 ℃/min, is increased to 700 ℃ at the speed of 3 ℃/min, is increased to 1225 ℃ at the speed of 4 ℃/min, is kept for 6h, and is cooled to room temperature along with the furnace.
And (3) testing: the cores were tested for room temperature strength, high temperature strength and high temperature deflection as per HB5353.3-2004 and HB5353.4-2004, respectively, and the test results are shown in Table 1.
To better illustrate the advantageous effects of the present invention, a DS core prepared by the same preparation method of the present invention using a general quartz powder material is now referred to as a comparative example. The raw material used in the comparative example is fused quartz powder with the purity of 99.2, sodium-containing silica gel powder and quartz glass powder are used as raw materials to prepare a core dry material, wherein the content of the silica gel dry powder is 1.5%, the balance is formed by mixing three high-purity quartz glass powders with the D50 of 75um, 40um and 25um, and the mixing ratio of the three powders is 20%, 40% and 40%. The rest of the preparation was the same as in example 2 and the comparative examples have the properties shown in Table 1.
TABLE 1 core Properties
In conclusion, according to the analysis of the embodiment 1-2, the quartz powder with higher purity is used as the raw material of the superalloy directional solidification core, and the appropriate grain size distribution and sintering temperature are selected, so that the room temperature strength and the high temperature strength of the superalloy directional solidification core can be effectively improved, and the low high temperature deformation is kept.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.
Claims (10)
1. A preparation method of a superalloy directional solidification core is characterized by comprising the following steps:
s1, dry powder preparation:
uniformly mixing 0.5-2% of active powder by mass fraction and the rest of matrix powder, and drying after mixing and stirring to obtain dry powder;
s2, preparing wet powder:
heating and melting the plasticizer accounting for 19-25% of the mass fraction of the dry powder in the step S1, adding the dry powder obtained in the step S1 after melting, and mixing and stirring at a constant temperature to obtain wet powder;
s3, pressing a superalloy directional solidification core:
and (3) pressing and injecting the wet powder obtained in the step (S2) to obtain a wet core, trimming and sizing the wet core, putting the wet core into a burning pot filled with fillers, sintering, keeping the temperature for 3-8h after sintering, and cooling to room temperature to obtain the superalloy directional solidification core.
2. The method for preparing the superalloy directional solidification core according to claim 1, wherein in step S1, the active powder is any one of 300-500 mesh sodium silicate, sodium-containing silica gel dry powder, or water glass dry powder.
3. The method of claim 1, wherein in step S1, the base powder is high purity silica glass powder, wherein SiO is present in the base powder 2 The content reaches more than 99.99 percent.
4. The method for preparing the superalloy directional solidification core according to claim 2, wherein in step S1, the high-purity silica glass frit is formed by mixing three kinds of high-purity silica glass frits with D50 of 65um, 30um and 10um, and the mixing ratio of the three kinds of silica glass frits is 10% -40%, 20% -50% and 20% -40%, respectively.
5. The production method according to claim 1, wherein in step S1, the mixing and stirring time is not less than 4 hours, the drying temperature is 100 to 150 ℃, and the drying time is not less than 4 hours.
6. The method of claim 1, wherein in step S2 the plasticizer is a mixture of paraffin wax, stearic acid, and polyethylene.
7. The method of claim 1, wherein in step S2, the melting temperature is 100 to 130 ℃; the mixing and stirring time is not less than 24h, and the constant temperature range is 100-130 ℃.
8. The method of claim 1, wherein in step S3, the injection temperature is 80-100 ℃, the injection pressure is 1-7MPa, and the injection time is 5-15S.
9. The method of claim 1, wherein in step S3 the filler is kaolin or calcined alumina.
10. A superalloy directional solidification core prepared by the method of any of claims 1 to 9.
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