CN103242036B - Method for preparing composite ceramic core - Google Patents

Abstract

The invention provides a method for preparing a composite ceramic core. An inner layer of the composite ceramic core is made from a silica-based material, and an outer layer of the composite ceramic core is made from an alumina-based or yttria-based ceramic material. The method provided by the invention mainly comprises the steps of preparing slurry, molding, baking, soaking, drying, sintering and the like. By adopting the method for preparing the composite ceramic core, provided by the invention, the composite ceramic core which has high strength and is easy to remove is prepared, and the need that airplane engine turbine blades are prepared in an efficient cooling manner is met.

Description

A kind of preparation technology of composite ceramic core

technical field

The invention belongs to the field of preparation of ceramic materials, in particular to the preparation technology of ceramic cores for precision casting aircraft engine turbine blades.

Background technique

With the development of modern aviation technology, the requirements for the temperature bearing capacity of the turbine blades of the aircraft engine are getting higher and higher. To adapt to the ever-increasing turbine inlet temperature, the working temperature of the turbine blade must be increased from the following two aspects. One is to increase the temperature bearing capacity of the blade material itself, and the other is to improve the cooling effect of the blade by improving the cooling structure of the blade. So far, the ability of blade materials to withstand high temperatures has been greatly improved, but compared with the actual needs of the blades, it is still far from meeting the requirements. Therefore, it is necessary to continuously update the blade cooling structure to improve the cooling effect of the blades and meet the requirements of advanced engines.

The typical feature of high-efficiency air-cooled blades is that the blade has a cavity structure, and the cavity structure is very complex. In the traditional process, the blade is prepared by precision casting. The cavity of the blade needs to be formed by a ceramic core. It must have high strength and high creep resistance in the environment. At the same time, the blade must be easily removed by chemical methods after casting. Therefore, the ceramic core must have a suitable density. If the density is too low, Then the high temperature strength and creep resistance will decrease obviously. If the density is too high, it will be unfavorable for the removal of the ceramic core; The strength of the ceramic core must also maintain a certain porosity, and this contradiction brings considerable difficulty to the preparation of the ceramic core.

Contents of the invention

Purpose of the present invention: In order to solve the above problems, the present invention provides a method for preparing a high-strength and easy-to-remove ceramic core, which meets the needs of efficiently cooling and preparing aircraft engine turbine blades.

Concrete process of the present invention:

1. Preparation of plasticizer: Melt paraffin or its mixture, gradually add polyethylene in this state, keep stirring, and heat up to 120°C-160°C until polyethylene is completely dissolved in paraffin, stir evenly and filter for later use ;

2. Preparation of silica slurry: melt the plasticizer, gradually add silica hot powder, stir while adding powder, and add 0.5%-1.0% surfactant at the same time, stirring time 2- 8 hours;

3. Molding of the inner ceramic core: control the temperature of the silica slurry at 100-140°C, and use injection molding to form the inner ceramic core;

4. Roasting: Put the inner ceramic core into the alumina powder filler for firing, the final firing temperature is 1150-1190°C, and the time is 3-5 hours;

5. Preparation of alumina or yttrium oxide or zirconia slurry: the combination of slurry is composed of alumina powder and aluminum sol or yttrium oxide powder and yttrium oxide sol or zirconia and zirconium sol;

6. Soaking and drying: Soak the ceramic core in alumina or yttrium oxide or zirconia slurry for 2-6 hours under negative pressure, and then dry it in the air;

7. Sintering: Re-sinter the dried ceramic core with a final firing temperature of 1350-1550°C for 20-60 minutes to obtain a composite ceramic core.

In the process of the present invention, in the plasticizer, the mass percentage of paraffin is 80-95%, polyethylene is 2-5%, and the rest is beeswax or stearic acid;

In the process of the present invention, the inner core ceramic powder is silica-based ceramic powder;

In the process of the present invention, the surfactant added in the silica-based ceramic powder is oleic acid or other fatty alcohols;

In the process of the present invention, the silica-based ceramic slurry is molded by injection molding, the molding pressure is 0.4-0.8MPa, the injection time is 20-120 seconds, and the holding time is 20-120 seconds;

In the process of the present invention, the plasticizer in the silica-based ceramic core is removed by a filler method, and the filler is aluminum oxide powder with a particle size of 100-300 mesh industrial alumina powder;

In the process of the present invention, the dewaxing stage of the silica-based ceramic core adopts low-temperature slow-rising sintering, and the temperature is lower than 500°C; the final sintering stage adopts high-temperature sintering, the silicon-based sintering is at 1150°C-1190°C, and the holding time is 3-5 hours , and then the furnace was cooled to room temperature;

In the process of the present invention, the prepared alumina or yttrium oxide or zirconia slurry is composed of alumina powder and aluminum sol or yttrium oxide and yttrium oxide sol or zirconia and zirconium sol, and the powder-liquid mass ratio is ( 1-2): 1, the particle size of the powder is 100nm-1000nm, and the particle size in the sol is 5-20nm;

In the process of the present invention, the inner ceramic core is immersed in alumina, yttrium oxide or zirconia slurry under negative pressure, and the pressure is 0.01-0.05MPa;

In the process of the present invention, after the inner layer ceramic core is soaked in alumina or yttrium oxide or zirconia slurry, it needs to be dried for 4-12 hours at 22-24°C with a relative humidity of 50%-70%, and then the ceramic core is Re-soak and re-dry, repeat the process 2-5 times, the thickness of the outer layer is controlled at 0.05-2mm; finally, the ceramic core is sintered at 1300°C-1550°C for 20-120 minutes, and cooled with the furnace;

In the process of the present invention, after the ceramic core is sintered, the ceramic core is immersed in thermosetting phenolic resin or urea, taken out and dried in the air.

The beneficial effect of the present invention is that: the composite ceramic core prepared by the preparation method of the present invention has a higher strength of 12-25 MPa and a higher resistance to deformation (deflection of 0.5-1.8 mm), and the ceramic core has a suitable density of 34-37%, which is beneficial to the removal of the ceramic core.

Description of drawings

Fig. 1 is an appearance view of a composite ceramic core prepared in preferred embodiment 1 of the present invention.

Fig. 2 is an appearance view of the composite ceramic core prepared in preferred embodiment 2 of the present invention.

Detailed ways

Embodiment one

Melt the paraffin and add 1% polyethylene, keep stirring, heat up to 130°C until the polyethylene is completely dissolved in the paraffin, then gradually add hot powder, the mass ratio of powder to plasticizer is 85:15, powder It is coarse quartz powder and fine quartz powder, and the mass ratio of the two is 30:70. While adding ceramic powder, stir, and at the same time, add 1.0% surfactant oleic acid with a total mass of 1.0%, and stir for 6 hours; After the plasticizer, powder, and surfactant are mixed evenly, the temperature is kept between 120°C. The ceramic core is pressed by injection method, the molding pressure is 0.4MPa, the injection time is 20 seconds, and the pressure holding time is 60 seconds; the ceramic core is loaded into the filler, and the filler is made of aluminum oxide powder with a particle size of 200 mesh for industrial use. Alumina powder; the dewaxing stage of the ceramic core is sintered with low temperature and slow heating, the heating rate is 5°C/min, and it is kept for 1 hour when it rises to 500°C; the final firing temperature is 1150°C, and the time is 4 hours. Prepare alumina slurry, which is composed of alumina powder and aluminum sol solution, the mass ratio of powder to liquid is 1:1, the particle size of alumina powder is 200nm, and the particle size in the sol is 10nm; the inner layer ceramic type Soak the core in alumina slurry at 0.01MPa for 20 minutes, then take out the ceramic core and dry it at 24°C with a relative humidity of 70% for 4 hours, repeat this process 4 times, and then sinter the ceramic core at 1450°C Cool with the furnace for 20 minutes; finally, immerse the ceramic core in thermosetting phenolic resin or urea, take it out and dry it in the air.

The prepared ceramic core is shown in Figure 1. From Figure 1, it can be seen that the composite ceramic core prepared in Example 1 of the present invention has a typical inner and outer layer structure; at the same time, it has excellent comprehensive performance. After testing, the high temperature bending strength of 1500 ° C can reach 15MPa, the deflection value can reach 0.8mm; while the 1500°C high-temperature bending strength of the ceramic core made of silicon base in the traditional preparation process only reaches 7MPa, and the deflection value has reached 1.8mm.

Embodiment two

Melt the paraffin and add 1% polyethylene, keep stirring, heat up to 130°C until the polyethylene is completely dissolved in the paraffin, then gradually add hot powder, the mass ratio of powder to plasticizer is 85:15, powder It is coarse quartz powder and fine quartz powder, and the mass ratio of the two is 30:70. While adding ceramic powder, stir, and at the same time, add 1.0% surfactant oleic acid with a total mass of 1.0%, and stir for 6 hours; After the plasticizer, powder, and surfactant are mixed evenly, the temperature is kept between 120°C. The ceramic core is pressed by injection method, the molding pressure is 0.4MPa, the injection time is 20 seconds, and the pressure holding time is 60 seconds; the ceramic core is loaded into the filler, and the filler is made of aluminum oxide powder with a particle size of 200 mesh for industrial use. Alumina powder; the dewaxing stage of the ceramic core is sintered with low temperature and slow heating, the heating rate is 5°C/min, and it is kept for 1 hour when it rises to 500°C; the final firing temperature is 1150°C, and the time is 4 hours. Prepare zirconia slurry, the slurry is composed of zirconia powder and zirconium sol solution, the mass ratio of powder to liquid is 1:1, the particle size of zirconia powder is 200nm, and the particle size in the sol is 10nm; the inner ceramic type Soak the core in zirconia slurry for 20 minutes under the condition of 0.01MPa, then take out the ceramic core and dry it for 4 hours at 24°C with a relative humidity of 70%, repeat this process 4 times, and then sinter the ceramic core at 1390°C For 40 minutes, cool with the furnace; finally, immerse the ceramic core in thermosetting phenolic resin or urea, take it out and dry it in the air.

Fig. 2 is the appearance diagram of the composite ceramic core prepared in the preferred embodiment 2 of the present invention. It can be seen from the figure that the composite ceramic core has a typical inner and outer layer structure, has excellent comprehensive performance, and the high temperature bending strength of 1550 ° C can reach 12MPa, the deflection value can reach 1.2mm; while the 1550°C high-temperature bending strength of the ceramic core made of silicon base in the traditional preparation process only reaches 3MPa, and the deflection value has reached 3.2mm.

Embodiment Three

Melt the paraffin and add 1% polyethylene, keep stirring, heat up to 130°C until the polyethylene is completely dissolved in the paraffin, then gradually add hot powder, the mass ratio of powder to plasticizer is 85:15, powder It is coarse quartz powder and fine quartz powder, and the mass ratio of the two is 30:70. While adding ceramic powder, stir, and at the same time, add 1.0% surfactant oleic acid with a total mass of 1.0%, and stir for 6 hours; After the plasticizer, powder, and surfactant are mixed evenly, the temperature is kept between 120°C. The ceramic core is pressed by injection method, the molding pressure is 0.4MPa, the injection time is 20 seconds, and the pressure holding time is 60 seconds; the ceramic core is loaded into the filler, and the filler is made of aluminum oxide powder with a particle size of 200 mesh for industrial use. Alumina powder; the dewaxing stage of the ceramic core is sintered with low temperature and slow heating, the heating rate is 5°C/min, and it is kept for 1 hour when it rises to 500°C; the final firing temperature is 1150°C, and the time is 4 hours. Prepare yttrium oxide slurry, the slurry is composed of yttrium oxide powder and yttrium sol solution, the mass ratio of powder to liquid is 1:1, the particle size of yttrium oxide powder is 200nm, and the particle size in the sol is 10nm; Soak the core in yttrium oxide slurry for 20 minutes under the condition of 0.01MPa, then take out the ceramic core and dry it for 4 hours at 24°C with a relative humidity of 70%, repeat the process 5 times, and then sinter the ceramic core at 1400°C For 30 minutes, cool with the furnace; finally, immerse the ceramic core in thermosetting phenolic resin or urea, take it out and dry it in the air.

The composite ceramic core prepared in Example 3 has a typical inner and outer layer structure, and has excellent comprehensive performance. The high temperature bending strength at 1500°C can reach 18MPa, and the deflection value can reach 0.9mm. However, the high-temperature flexural strength of the ceramic core made of silicon base only reaches 7MPa at 1500°C, and the deflection value has reached 1.8mm.

In summary, the composite ceramic core prepared by the preparation method of the present invention has a higher strength of 12-25MPa and a higher resistance to deformation (deflection of 0.5-1.8mm) in a high-temperature environment of 1500-1580°C At the same time, the ceramic core has a suitable density of 34-37%, which is beneficial to the removal of the ceramic core and meets the needs of efficient cooling for preparing aircraft engine turbine blades.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the scope of application of the present invention; all other equivalent changes or modifications that do not deviate from the essence disclosed in the present invention should be included in the following rights within the scope of the request.

Claims (4)

1. a composite ceramic core preparation method, the internal layer of described composite ceramic core is silica-based materials, skin is alumina base or yttria-base or zirconia-based material; It is characterized in that: described composite ceramic core preparation method comprises the steps:

(1) prepare softening agent: polyethylene will be added after melted paraffin wax, constantly stir, be warming up to 120 ℃-160 ℃, until polyethylene is dissolved in paraffin completely, after stirring, filter;

(2) prepare silica slurry: by described softening agent fusing, add gradually the hot powder of silicon-dioxide, stir while adding, stir the tensio-active agent that simultaneously adds 0.5%-1.0%, churning time 2-8 hour, described tensio-active agent is oleic acid or other aliphatic alcohols materials;

(3) internal layer ceramic core moulding: described silica slurry temperature is controlled to 100-140 ℃, adopts injection molding to carry out moulding;

(4) roasting (removing softening agent): internal layer ceramic core is packed in aluminum oxide powder filler and carries out roasting, and burning temperature is eventually 1150-1190 ℃, time 3-5 hour;

(5) the outer slip of preparation ceramic core: be preparation aluminum oxide or yttrium oxide or Zirconia Slurry, be combined as aluminum oxide powder and aluminium colloidal sol or yttrium oxide and the yttrium oxide colloidal sol or zirconium white and zirconium colloidal sol of slip form, powder liquid mass ratio is (1-2): 1, the particle diameter of powder is 100nm-1000nm, and in colloidal sol, size of particles is 5-20nm;

(6) soak, be dried: under 0.01-0.05MPa condition of negative pressure, internal layer ceramic core is immersed in to 2-6 hour in outer slip, then at air drying, need under 22-24 ℃ of relative humidity 50%-70% condition, be dried 4-12 hour, then ceramic core soaked again and be dried again, repeat this process 2-5 time, outer layer thickness is controlled at 0.05-2mm;

(7) sintering: dried ceramic core is carried out to sintering again, and burning temperature is eventually 1350-1550 ℃, and time 20-60 minute, finally makes composite ceramic core.

2. composite ceramic core preparation method according to claim 1, is characterized in that: the Quality of Paraffin Waxes per-cent in described step 1 softening agent is 80-95%, and polyethylene mass percent is 2-5%, and all the other are beeswax or stearic acid.

3. composite ceramic core preparation method according to claim 1 and 2, is characterized in that: described injection molding forming pressure is 0.4-0.8MPa, and be 20-120 second inject time, and the dwell time is 20-120 second.

4. composite ceramic core preparation method according to claim 1, it is characterized in that: in described roasting (removing softening agent) step, pack described internal layer ceramic core into aluminium sesquioxide powder, granularity is to carry out roasting in the industrial oxidation aluminium powder of 100-300 order, burning temperature is eventually 1150-1190 ℃, time 3-5 hour.