阅读说明：本技术 碳化硅增强硅基陶瓷型芯及其制备方法 (Silicon carbide reinforced silicon-based ceramic core and preparation method thereof ) 是由 梁康硕 刘枫 于 2020-06-12 设计创作，主要内容包括：本发明的碳化硅增强硅基陶瓷型芯及其制备方法,陶瓷型芯原料包括碳化硅、碳化硅晶须、氧化硅、金属钇粉末和粘结剂；碳化硅晶须加入量为碳化硅粉末的10-18％；氧化硅加入量为碳化硅粉末30-50％；金属钇粉末加入量为碳化硅粉末的0.1-0.8％,粘结剂加入量为上述材料质量总和的10％-25％。制备时先进行干粉混合,然后再将混合均匀的粉料逐步加入融化的粘结剂中,压制成型,并在氧气氛围的梭式窑中烧结,终烧温度为1350-1650℃成型后制得补强的陶瓷型芯,该陶瓷型芯通过碳化硅复合,抗折断层具有大量球形样貌,产品强度明显提高,具有优异的物理性能,可以提高产品的耐高温、抗冲击等性能,并且提高了陶瓷型芯在1450℃在以上的工作时间。(The invention relates to a silicon carbide reinforced silicon-based ceramic core and a preparation method thereof, wherein the ceramic core comprises silicon carbide, silicon carbide whiskers, silicon oxide, yttrium metal powder and a binder; the addition amount of the silicon carbide whiskers is 10-18% of the silicon carbide powder; the adding amount of the silicon oxide is 30-50% of the silicon carbide powder; the addition amount of the metal yttrium powder is 0.1-0.8% of the silicon carbide powder, and the addition amount of the binder is 10-25% of the total mass of the materials. The preparation method comprises the steps of mixing dry powder, gradually adding the uniformly mixed powder into a molten binder, carrying out compression molding, sintering in a shuttle kiln in an oxygen atmosphere, and carrying out molding at a final sintering temperature of 1350-.)

1. The silicon carbide reinforced silicon-based ceramic core is characterized by comprising the following raw materials: silicon carbide powder, silicon carbide whiskers, metal yttrium powder, silicon oxide and a binder; wherein:

the silicon carbide powder has the purity of more than 99 percent, and the D50 has the following particle size distribution and mass percentage: 325-550 μm accounts for 4-15%, 120-180 μm accounts for 30-35%, 38-70 μm accounts for 30-55%; 25-40% of 18-23 μm;

the added mass of the silicon carbide whisker is 10-18% of that of silicon carbide powder;

the silicon oxide powder accounts for 30-50% of the silicon carbide powder by mass;

the mass of the added metal yttrium powder is 0.1-0.8% of that of the silicon carbide powder;

the adding mass of the binder is 10-25% of the total mass of the silicon carbide powder, the silicon carbide whisker, the metal yttrium powder and the silicon oxide material.

2. The silicon carbide reinforced silicon-based ceramic core as recited in claim 1, wherein the silicon carbide whiskers have an average particle size of 100nm and a specific surface area of 30m²The diameter of the whisker is 0.05-1 μm, and the length is 10-100 μm.

3. The silicon carbide reinforced silicon-based ceramic core of claim 1, wherein the silicon oxide powder particle size is from 62 μ ι η to 90 μ ι η.

4. The silicon carbide reinforced silicon-based ceramic core of claim 1, wherein the binder is liquid paraffin and paraffin in a mass ratio of (0.2-1): (1.5-2).

5. The method of making a silicon carbide reinforced silicon-based ceramic core of claim 1, comprising the steps of:

(1) preparing the raw materials of the silicon carbide reinforced silicon-based ceramic core according to the proportion;

(2) the method comprises the steps of uniformly stirring and mixing raw materials, pressing the raw materials into a blank, sintering the blank in a sintering furnace, and cooling the blank to obtain the silicon carbide reinforced silicon-based ceramic core, wherein the sintering adopts two-stage sintering, the first-stage sintering temperature is 1250 ℃, the sintering time is 1-2 hours, the second-stage sintering temperature is 1650 ℃, and the sintering time is 0.5-1.5 hours.

6. The method for preparing the silicon carbide reinforced silicon-based ceramic core according to claim 5, wherein in the step (2), the temperature is raised to the first-stage sintering temperature by a gradient temperature raising process before the first-stage sintering, and the specific process comprises the following steps:

(1) first-stage heating: the temperature is 0 ℃ to minus 250 ℃ and 300 ℃, the heating rate is 3 to 5 ℃/min, and the heat preservation time is 2.8 to 3.5 h;

(2) and (3) second-stage heating: (250-300 ℃) - (550-650 ℃), the heating rate is 1-3 ℃/min, and the heat preservation time is 2-3 h;

(3) and (3) three-stage heating: the temperature rise rate is 3-5 ℃/min at (550-.

7. The method for preparing the silicon carbide reinforced silicon-based ceramic core according to claim 5, wherein in the step (2), the two-stage sintering comprises the following specific steps: (1000-1250 ℃) - (1350-1650 ℃), the heating rate is 1-5 ℃/min, the sintering time is 0.5-1.5h, and the second-stage sintering is completed.

8. The method for preparing the silicon carbide reinforced silicon-based ceramic core according to claim 5, wherein in the step (2), the sintering furnace is an oxygen-atmosphere shuttle kiln, the sintering is carried out in an oxygen atmosphere, the volume percentage of oxygen in flue gas in the shuttle kiln is 2.5-5% during the sintering process, and the flow of the combustion air in the shuttle kiln is 15-38m³Min, gas flow of 1.1-2.1m³/min。

9. The method of claim 5, wherein in step (2), the silicon carbide reinforced silicon-based ceramic core is a ceramic core for directional, single crystal hollow blade casting.

10. The method for preparing the silicon carbide reinforced silicon-based ceramic core according to claim 5, wherein in the step (2), the prepared silicon carbide reinforced silicon-based ceramic core is detected to have the high-temperature rupture strength at 1520 ℃ of 31.1-42.6MPa, the casting yield of 85-89%, the depoling period of 7-9h, the shrinkage length of 0.18-0.32%, the width of 0.08-0.2%, the thickness of 0.1-0.47% and the porosity of 25-28%.

The technical field is as follows:

the invention belongs to the technical field of precision casting-ceramic cores, and particularly relates to a silicon carbide reinforced silicon-based ceramic core and a preparation method thereof.

Background art:

with the continuous development of cooling technology, the shape of the inner cavity of the blade is gradually complicated, and a ceramic core is required to be formed in investment casting. Therefore, the technical development of the ceramic core directly influences the level of the hollow blade, and the ceramic core is always a bottleneck in the development and casting of the hollow blade and determines the dimensional precision, the qualification rate and the production cost of the cast blade. Therefore, it is important to make continuous improvements in ceramic core materials and manufacturing techniques.

The silicon-based ceramic core has the advantages of small thermal expansion coefficient, excellent thermal stability, high mechanical strength, good chemical stability, convenient depoling and the like, particularly has short depoling period and high efficiency compared with other types of ceramic cores, so that the silicon-based ceramic core is widely applied to the field of manufacturing of hollow turbine blades, and a great deal of research work is internationally carried out on the series of ceramic cores. When the existing ceramic core is used for pouring the directional and single crystal hollow blade, the blade often deforms and even breaks due to poor high-temperature performance, and the yield of the blade is seriously influenced. Therefore, the development of silicon-based ceramic cores with excellent overall properties, in particular good high temperature creep resistance, is of great significance for the production of oriented, single crystal hollow blades.

The invention content is as follows:

the invention aims to overcome the defects in the prior art and provide the silicon carbide reinforced silicon-based ceramic core and the preparation method thereof. Meanwhile, the pure silicon-based ceramic core prepared by the technology has obvious advantages in removal effect, and is particularly suitable for thin, thick and large ceramic cores with complex sizes. The core-breaking process can greatly avoid the problems of long core-breaking period caused by thick and large complex sizes, core breaking caused by poor core-breaking strength of thin and complex sizes, short high-temperature service life and the like, and further avoid the problem of product waste caused by core breaking in the metal pouring process.

In order to achieve the purpose, the invention adopts the following technical scheme:

a silicon carbide reinforced silicon-based ceramic core comprises the following raw materials: silicon carbide powder, silicon carbide whiskers, metal yttrium powder, silicon oxide and a binder; wherein:

the silicon carbide powder has the purity of more than 99 percent, and the D50 has the following particle size distribution and mass percentage: 325-550 μm accounts for 4-15%, 120-180 μm accounts for 30-35%, 38-70 μm accounts for 30-55%; 25-40% of 18-23 μm;

the added mass of the silicon carbide whisker is 10-18% of that of silicon carbide powder;

the silicon oxide powder accounts for 30-50% of the silicon carbide powder by mass;

the mass of the added metal yttrium powder is 0.1-0.8% of that of the silicon carbide powder;

the adding mass of the binder is 10-25% of the total mass of the silicon carbide powder, the silicon carbide whisker, the metal yttrium powder and the silicon oxide material.

The average grain diameter of the silicon carbide whisker is 100nm, and the specific surface area is 30m²The diameter of the whisker is 0.05-1 μm, and the length is 10-100 μm.

The particle size of the silicon oxide powder is 62-90 μm.

The adhesive is prepared from liquid paraffin and paraffin according to the mass ratio of (0.2-1): (1.5-2).

The preparation method of the silicon carbide reinforced silicon-based ceramic core comprises the following steps:

(1) preparing the raw materials of the silicon carbide reinforced silicon-based ceramic core according to the proportion;

(2) the raw materials are stirred uniformly and mixed, pressed into a blank, sintered in a sintering furnace and cooled to prepare the silicon carbide reinforced silicon-based ceramic core, wherein the sintering adopts two-stage sintering, the first-stage sintering temperature is 1250 ℃, the sintering time is 1-2h, the second-stage sintering temperature is 1350-.

In the step (1), the raw materials are uniformly stirred and mixed, and then are pressed into a ceramic core blank body with a cuboid structure according to a mould.

In the step (2), the temperature rise rate of the first-stage sintering is 3-5 ℃/min.

In the step (2), a gradient heating process is specifically adopted to heat up to a first-stage sintering temperature before the first-stage sintering, and the specific process is as follows:

(1) first-stage heating: the temperature is 0 ℃ to minus 250 ℃ and 300 ℃, the heating rate is 3 to 5 ℃/min, and the heat preservation time is 2.8 to 3.5 h;

(2) and (3) second-stage heating: (250-300 ℃) - (550-650 ℃), the heating rate is 1-3 ℃/min, and the heat preservation time is 2-3 h;

(3) and (3) three-stage heating: the temperature rise rate is 3-5 ℃/min at (550-;

in the step (2), the temperature rise rate of the second-stage sintering is 1-5 ℃/min.

In the step (2), the specific process of the second-stage sintering is as follows: (1000- & lt 1250- & gt 1650 ℃), the heating rate is 1-5 ℃/min, the sintering time is 0.5-1.5h, the second-stage sintering is completed, and the silicon carbide is gradually oxidized and melted at the stage.

In the step (2), the temperature of the second-stage sintering is preferably 1450-1600 ℃.

In the step (2), the sintering furnace is a shuttle kiln with an oxygen atmosphere, sintering is carried out in the oxygen atmosphere, the volume percentage content of oxygen in flue waste gas in the shuttle kiln is 2.5-5% in the sintering process, and the flow rate of combustion-supporting air in the shuttle kiln is 15-38m³Min, gas flow of 1.1-2.1m³/min。

In the step (2), the silicon oxide is gradually melted in the first-stage sintering process;

in the step (2), in the process of secondary sintering, the silicon carbide is gradually oxidized and melted.

In the step (2), the cooling mode after sintering is furnace cooling.

In the step (2), the prepared silicon carbide reinforced silicon-based ceramic core is a ceramic core for casting directional and single crystal hollow blades.

In the step (2), through detection, the prepared silicon carbide reinforced silicon-based ceramic core has the high-temperature rupture strength of 31.1-42.6MPa at 1520 ℃, the casting qualification rate of 85-89%, the depoling period of 7-9h, the shrinkage length of 0.18-0.32%, the width of 0.08-0.2%, the thickness of 0.1-0.47% and the porosity of 25-28%.

In the step (2), the detection shows that the bending strength of the prepared silicon carbide reinforced silicon-based ceramic core at 1520 ℃ is 37.9-42.6 MPa.

The invention has the beneficial effects that:

(1) the comprehensive performance is excellent: the ceramic core is added with the silicon carbide and the silicon carbide whiskers, the silicon carbide, the oxygen and the silicon oxide are well fused under the condition of high-temperature oxygen atmosphere, the silicon oxide powder is fused by taking the silicon carbide whiskers as an axis, the silicon carbide is converted into the silicon oxide under the condition of the existence of yttrium metal, the silicon oxide and the silicon oxide powder are fused, coated and aggregated layer by layer to form a sphere, and the yttrium metal powder is converted into the yttrium oxide under the oxidation condition and then gradually plays a role of a mineralizer, so that the ceramic core has excellent mechanical property, heat resistance and high-temperature oxidation resistance, has stronger reinforcing and toughening effects, greatly improves the bending strength and impact strength of a product, and has high-temperature resistant service life during metal casting.

(2) The error rate is reduced: meanwhile, the ceramic core has small length, width and thickness (XYZ) deformation, reduces the size error of the inner cavity of the hollow blade, improves the product precision of the hollow blade, and reduces the consumption of manpower and material resources during the production of the hollow blade.

(3) The core removing efficiency is improved: meanwhile, as the main component of the hollow blade is high-purity silicon oxide (generated by silicon carbide oxidation reaction), the hollow blade can quickly react with alkali liquor with a certain temperature in the core removing liquid to dissolve, the core removing efficiency is improved, and the manufacturing period and the pollution in the production process of the hollow blade are reduced.

Description of the drawings:

FIG. 1 is a SEM image of the cross-section of a silicon carbide reinforced ceramic core prepared in accordance with example 1 of the present invention taken 80 times after high temperature flexural strength testing;

FIG. 2 is a SEM image of the cross-section of a SiC reinforced ceramic core prepared in accordance with example 1 of the present invention taken 1200 times after high temperature flexural strength testing; .

FIG. 3 is a SEM image of the cross-section of a silicon carbide reinforced ceramic core prepared in accordance with example 1 of the present invention taken after a high temperature flexural strength test at 3000 times;

FIG. 4 is an SEM image of the cross-section x 80 times after high temperature flexural strength testing of an unmodified silica ceramic core made according to a comparative example of the present invention;

FIG. 5 is an SEM image of cross-section x 1000 times after high temperature flexural strength testing of an unmodified silica ceramic core made according to a comparative example of the present invention;

FIG. 6 is an SEM image of cross-section x 2000 times after high temperature flexural strength testing of an unmodified silica ceramic core made according to a comparative example of the present invention;

FIG. 7 is a real-time plot of high temperature rupture value versus time for an unmodified silica ceramic core prepared in accordance with a comparative example of the present invention;

FIG. 8 is a real-time plot of high temperature rupture value versus time for a silicon carbide reinforced ceramic core made in accordance with example 1 of the present invention;

FIG. 9 is a real-time plot of high temperature rupture value versus time for a silicon carbide reinforced ceramic core made in accordance with example 2 of the present invention;

FIG. 10 is a real-time plot of high temperature rupture value versus time for a silicon carbide reinforced ceramic core prepared in accordance with example 3 of the present invention;

FIG. 11 is a real-time plot of high temperature rupture strength value versus time for a silicon carbide reinforced ceramic core made in accordance with example 4 of the present invention.

The specific implementation mode is as follows:

the present invention will be described in further detail with reference to examples.

The following examples and comparative examples:

the adopted shuttle kiln model is ASB-S5.45; the prepared ceramic core blank is in a cuboid structure with the same size; in the core-removing experiment, cuboid test bars with the same size are used for testing.

Comparative example

The unmodified silica ceramic core is prepared from 35 wt.% of SiO with 220 mesh particle size₂Powder, 18 wt.% of SiO with particle size 300 mesh₂Powder, 21 wt.% of SiO with a particle size of 350 mesh₂Powder, 26 wt.% ZrO with a particle size of 300 mesh₂Powder; mixing binder prepared from paraffin, Cera flava and polyethylene, and accounting for 15 wt% of the total powder.

The preparation steps are as follows:

(1) and (3) uniformly mixing the dry powder raw materials, gradually adding a binder, heating to 110 ℃ to form slurry, stirring for 2-5 h, then pouring the slurry into a material barrel of a ceramic core injection molding machine, and stirring for later use.

(2) Heating the ceramic core mold to 35 ℃, and controlling the mold closing pressure to be 9 Mpa. And (3) grouting at 4Mpa for 20 seconds, maintaining the pressure for 15 seconds, and molding into a ceramic core blank with a cuboid structure.

(3) Putting the ceramic core blank into kiln furniture and filling with Al₂O₃Filling, keeping the filling plain and solid, putting kiln furniture into a high-temperature furnace for roasting, firstly heating to 250 ℃ at the heating rate of 3.5 ℃/min, preserving heat for 3h, then heating to 500 ℃ at the heating rate of 1 ℃/min, preserving heat for 3h, then heating to 850 ℃ at the heating rate of 4 ℃/min, preserving heat for 4h, and finally heating to 1250 ℃ at the heating rate of 3 ℃/min, preserving heat for 6 h.

(4) And taking the ceramic core after roasting out of the kiln furniture, cleaning floating sand on the surface to obtain the unmodified silicon oxide ceramic core, wherein the SEM image of the fault section multiplied by 80 times is shown in figure 4, the SEM image multiplied by 1000 times is shown in figure 5, the SEM image multiplied by 2000 times is shown in figure 6 after the high-temperature flexural strength test at 1520 ℃, the real-time curve of the obtained high-temperature flexural strength value-time is shown in figure 7, the decoring period is 32h, the high-temperature flexural strength at 1520 ℃ is 17.9MPa, the shrinkage rate is 1.5 percent, the width is 2.5 percent, the thickness is 2.5 percent, and the porosity is 25 percent.

In the following embodiments 1-4, after mixing the dry powder raw materials in proportion, gradually adding the binder, uniformly mixing, uniformly heating to 110 ℃ to form slurry, stirring for 2-5 h, pouring the slurry into a material barrel of a ceramic core injection molding machine, and stirring for later use; and heating the ceramic core mold to 35 ℃, and controlling the mold closing pressure to be 9 Mpa. The grouting pressure is 4Mpa, the grouting time is 20 seconds, the pressure maintaining time is 15 seconds, after a ceramic core blank body with a cuboid structure is manufactured according to a mould, the ceramic core blank body is placed into a kiln tool and is filled with Al₂O₃Filling, keeping the filling flat and solid, putting the kiln furniture into a shuttle kiln, and sintering according to the system requirement.