High-performance silicon nitride turbine rotor and method of making same

Abstract

The application provides a high-performance silicon nitride turbine rotor and a preparation method thereof, and belongs to the technical field of ceramic structural parts. The preparation method of the high-performance silicon nitride turbine rotor comprises the following steps: mixing silicon nitride powder, boron nitride nanotubes, zirconium oxide powder and a lithium oxide source, and then performing ball milling to obtain a mixed powder; mixing the mixed powder, a binder and water, and then injecting the mixture into a turbine rotor mold to perform press forming to obtain a blank; and sequentially performing vacuum pre-burning and vacuum hot-press sintering on the blank to obtain the high-performance silicon nitride turbine rotor. The mass of the boron nitride nanotubes is 1-7% of the mass of the silicon nitride powder; the mass of the zirconium oxide powder is 1-3% of the mass of the silicon nitride powder; and the mass of lithium in the lithium oxide source is 0.15-0.7% of the mass of the silicon nitride powder. The bending strength of the silicon nitride ceramic sample prepared by the preparation method can reach 952 MPa, and the fracture toughness can reach 9.3 MPa·m 1 / 2 .

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of ceramic structural parts, in particular to a high-performance silicon nitride turbine rotor and a preparation method thereof. BACKGROUND

[0002] The turbocharger is a device for improving the power of the engine, and the turbine rotor as a key component of the turbocharger directly affects the use reliability of the turbine at high temperature and high speed. With the development of turbocharger technology, the material of the turbine rotor as a key component is also constantly updated. Before 1988, the diesel engine turbocharger turbine generally used 20Cr3MoWV(A) material, then replaced with K213 nickel-based alloy, and several years later replaced with K418 nickel-based alloy. However, during use, it was found that the turbine made of K418 nickel-based alloy had blade deformation and flying crack failure at high temperature and high speed, and the turbine had large weight and poor responsiveness, and the surface was easy to form carbon blocks, and the small carbon blocks fell off and hit the turbine blades, resulting in blade fracture failure.

[0003] Compared with traditional metal turbine materials, engineering ceramics have become a research hotspot in recent years due to a series of excellent properties. As one of the commonly used high-temperature and high-strength structural ceramics, silicon nitride ceramic has good properties such as high strength, high hardness, oxidation resistance, wear resistance, and corrosion resistance, and is widely used in the fields of aerospace, electric power, and machinery. In the field of turbine rotor manufacturing, it becomes an ideal substitute material for nickel-based alloy. However, as a ceramic material, its intrinsic brittleness limits the development of silicon nitride ceramic. Under the load of high temperature and high speed, the ceramic material must have sufficient strength and fracture toughness to meet the working conditions of the turbine.

[0004] In order to improve the strength and crack propagation resistance of silicon nitride ceramic, many scholars at home and abroad have achieved toughening and reinforcing by adding particles or fibers to silicon nitride ceramic. Lange reported the use of sub-micron silicon carbide particles to reinforce silicon nitride ceramic and analyzed the mechanical properties, and the results showed that the toughness of the material was improved, but the room temperature strength was not ideal. Although the use of chopped carbon fibers to toughen silicon nitride ceramic can improve the fracture toughness of the ceramic, the reaction between carbon fibers and oxygen produces defects in the silicon nitride ceramic, which reduces the bending strength of the material.

[0005] Therefore, how to improve the comprehensive mechanical properties of the silicon nitride turbine rotor has become a technical problem to be solved in the field. SUMMARY

[0006] In view of this, the purpose of the present application is to provide a high-performance silicon nitride turbine rotor and a preparation method thereof. The high-performance silicon nitride turbine rotor prepared by the preparation method has excellent comprehensive mechanical properties.

[0007] To achieve the above-mentioned purposes of the application, the application provides the following technical solutions.

[0008] The application provides a preparation method of a high-performance silicon nitride turbine rotor, comprising the following steps:

[0009] (1) mixing silicon nitride powder, boron nitride nanotubes, zirconium oxide powder and lithium oxide source, and then performing ball milling to obtain mixed powder; the mass of the boron nitride nanotubes is 1-7% of the mass of the silicon nitride powder; the mass of the zirconium oxide powder is 1-3% of the mass of the silicon nitride powder; the mass of lithium in the lithium oxide source is 0.15-0.7% of the mass of the silicon nitride powder;

[0010] (2) mixing the mixed powder obtained in the step (1) with a binder and water, and then injecting into a turbine rotor mold to perform press forming to obtain a blank;

[0011] (3) sequentially performing vacuum pre-burning and vacuum hot-press sintering on the blank obtained in the step (2) to obtain a high-performance silicon nitride turbine rotor.

[0012] Preferably, the mass of the boron nitride nanotubes in the step (1) is 2-6% of the mass of the silicon nitride powder.

[0013] Preferably, the mass of the zirconium oxide powder in the step (1) is 1.5-2.5% of the mass of the silicon nitride powder.

[0014] Preferably, the mass of lithium in the lithium oxide source in the step (1) is 0.2-0.6% of the mass of the silicon nitride powder.

[0015] Preferably, the silicon nitride powder in the step (1) is subjected to airflow crushing before use.

[0016] Preferably, the ball-to-material ratio of the ball milling in the step (1) is (8-10):1, the rotation speed of the ball milling is 200-300 rpm, and the ball milling time is 20-24 h.

[0017] Preferably, the mass ratio of the mixed powder to the binder in the step (2) is 1:(0.5-1.5).

[0018] Preferably, the temperature of the vacuum pre-burning in the step (3) is 1450-1550 ℃, and the vacuum pre-burning time is 20-40 min.

[0019] Preferably, the temperature of the vacuum hot-press sintering in the step (3) is 1750-1850 ℃, the pressure of the vacuum hot-press sintering is 35-45 MPa, and the vacuum hot-press sintering time is 40-60 min.

[0020] The application further provides a high-performance silicon nitride turbine rotor prepared by the preparation method.

[0021] The application provides a preparation method of a high-performance silicon nitride turbine rotor, comprising the following steps: mixing silicon nitride powder, boron nitride nanotubes, zirconium oxide powder and a lithium oxide source, and then performing ball milling to obtain mixed powder; mixing the mixed powder, a binder and water, and then injecting the mixture into a turbine rotor mold to perform press forming to obtain a blank; and sequentially performing vacuum pre-sintering and vacuum hot-press sintering on the blank to obtain the high-performance silicon nitride turbine rotor; the mass of the boron nitride nanotubes is 1-7% of the mass of the silicon nitride powder; the mass of the zirconium oxide powder is 1-3% of the mass of the silicon nitride powder; and the mass of lithium in the lithium oxide source is 0.15-0.7% of the mass of the silicon nitride powder. In the application, the boron nitride nanotubes are added during the preparation of the silicon nitride turbine rotor to refine the crystal grains of the silicon nitride ceramic matrix, the strength and toughness of the ceramic matrix are improved by using fine-grain strengthening, the fracture toughness of the ceramic matrix is improved by controlling the addition amount of the boron nitride nanotubes to make the boron nitride nanotubes play the role of fiber reinforcement, the sintering stress is reduced by using the phase change of the zirconium oxide powder during sintering, the cracks caused by the sintering stress are eliminated by controlling the amount of the zirconium oxide powder, the toughness of the material is improved, the lithium oxide generated during sintering is used as a fluxing agent by using the lithium oxide source as a raw material, the amount of the fluxing agent is reduced, the purity and sintering density of the silicon nitride ceramic are improved, and the performance of the material is improved. The experimental results of the embodiments show that the bending strength of the silicon nitride ceramic sample prepared by the preparation method can reach 952 MPa, and the fracture toughness can reach 9.3 MPa·m 1 / 2 . DETAILED DESCRIPTION

[0022] The application provides a preparation method of a high-performance silicon nitride turbine rotor, comprising the following steps:

[0023] (1) mixing silicon nitride powder, boron nitride nanotubes, zirconium oxide powder and a lithium oxide source, and then performing ball milling to obtain mixed powder; the mass of the boron nitride nanotubes is 1-7% of the mass of the silicon nitride powder; the mass of the zirconium oxide powder is 1-3% of the mass of the silicon nitride powder; and the mass of lithium in the lithium oxide source is 0.15-0.7% of the mass of the silicon nitride powder;

[0024] (2) mixing the mixed powder obtained in the step (1), a binder and water, and then injecting the mixture into a turbine rotor mold to perform press forming to obtain a blank;

[0025] (3) sequentially performing vacuum pre-sintering and vacuum hot-press sintering on the blank obtained in the step (2) to obtain the high-performance silicon nitride turbine rotor.

[0026] Unless otherwise specified, the application does not have special limitations on the source of the raw materials, and commercially available products known to those skilled in the art can be used.

[0027] The present application mixes silicon nitride powder, boron nitride nanotube, zirconium oxide powder and lithium oxide source, and then performs ball milling to obtain a mixed powder.

[0028] In the present application, the particle size of the silicon nitride powder is preferably 0.1-10 μm, more preferably 0.2-5 μm, and most preferably 0.5-1 μm. By controlling the particle size of the silicon nitride powder, the sintering density of the silicon nitride ceramic can be improved, and thus the mechanical properties can be improved.

[0029] In the present application, the silicon nitride powder is preferably subjected to air flow crushing before use. By air flow crushing, the specific surface area, the loose bulk density, the tap density and the sphericity of the silicon nitride powder can be improved, which is more beneficial to injection molding, and thus the density and the consistency of the density distribution of the green body can be improved, and thus the sintering density and the mechanical properties of the silicon nitride ceramic can be further improved.

[0030] In the present application, the feeding rate of the air flow crushing is preferably 200-1000 g / min, more preferably 400-800 g / min, and most preferably 500-600 g / min; and the gas pressure of the air flow crushing is preferably 0.2-2 MPa, more preferably 0.5-1.5 MPa, and most preferably 1-1.2 MPa. By controlling the feeding rate and the gas pressure of the air flow crushing, the irregularly shaped silicon nitride powder can be fully collided and sheared in the grinding chamber to remove the edges and corners, and thus the sphericity can be further improved.

[0031] The device for the air flow crushing is not particularly limited in the present application, and any air flow crusher known to those skilled in the art can be used.

[0032] In the present application, the mass of the boron nitride nanotube is 1-7% of the mass of the silicon nitride powder, preferably 2-6%, more preferably 3-5%, and most preferably 4%. In the present application, the boron nitride nanotube as a raw material can refine the grains of the silicon nitride ceramic matrix during sintering, and thus the fine-grain strengthening effect can be achieved; and as a reinforcing phase, the boron nitride nanotube can deflect and bridge the crack propagation, consume the fracture energy, and improve the fracture toughness of the ceramic matrix; by controlling the addition amount of the boron nitride nanotube, the strength and the toughness of the silicon nitride ceramic can be improved at the same time, and thus excellent comprehensive mechanical properties can be achieved.

[0033] In the present application, the diameter of the boron nitride nanotube is preferably 20-30 nm, and more preferably 25 nm; and the length of the boron nitride nanotube is preferably 0.5-2 μm, and more preferably 1-1.5 μm. By selecting the boron nitride nanotube with the above-mentioned size, the reinforcing and toughening effect can be further improved.

[0034] In the present application, the mass of the zirconium oxide powder is 1-3% of the mass of the silicon nitride powder, preferably 1.5-2.5%, and more preferably 2%. In the present application, the zirconium oxide powder is used as a raw material, and phase transformation occurs during sintering, causing partial volume expansion, which compensates for the volume shrinkage of the silicon nitride ceramic during sintering, thereby reducing sintering stress. By controlling the amount, cracks caused by sintering stress are eliminated, and the toughness of the material is improved.

[0035] In the present application, the particle size of the zirconium oxide powder is preferably 0.1-10 μm, more preferably 0.2-5 μm, and most preferably 0.5-1 μm. By controlling the particle size of the zirconium oxide powder, the volume compensation effect is improved, and the mechanical properties are further improved.

[0036] In the present application, the mass of lithium in the lithium oxide source is 0.15-0.7% of the mass of the silicon nitride powder, preferably 0.2-0.6%, more preferably 0.3-0.5%, and most preferably 0.4%. In the present application, the lithium oxide source is used as a raw material, and lithium oxide is generated during sintering. The active lithium element assists in the breaking and formation of Si-N chemical bonds, improves the atomic diffusion coefficient in the silicon nitride powder during sintering, promotes the phase transition of silicon nitride from α to β, and further improves the fracture toughness of the ceramic material. At the same time, the amount of lithium oxide used as a fluxing agent is small, the content of the grain boundary phase between the silicon nitride grains in the sintered body is small, the purity and sintering density of the silicon nitride ceramic are improved, and the performance of the material is improved.

[0037] In the present application, the lithium oxide source preferably includes one or more of lithium oxide, lithium carbonate, and lithium acetate. In the present application, the lithium oxide source generates lithium oxide when heated and does not produce other solid substances, which can improve the purity of the ceramic matrix and further improve the mechanical properties.

[0038] The present application does not have special limitations on the mixing of the silicon nitride powder, boron nitride nanotubes, zirconium oxide powder, and lithium oxide source, and the material mixing technical solution well known to those skilled in the art can be used.

[0039] In the present application, the ball-to-material ratio of the ball milling is preferably (8-10):1, and more preferably 9:1. The rotation speed of the ball milling is preferably 200-300 rpm, and more preferably 250 rpm. The ball milling time is preferably 20-24 h, and more preferably 21-23 h. In the present application, the medium of the ball milling is preferably ethanol. Ball milling can avoid powder agglomeration, promote uniform mixing of the materials, and is beneficial to obtaining a product with uniform composition and organization.

[0040] After ball milling, the product of the ball milling is preferably dried to obtain a mixed powder. The present application does not have special limitations on the drying operation, and the ball milling medium can be removed.

[0041] After obtaining the mixed powder, the present application mixes the mixed powder with a binder and water, and then injects the mixture into a turbine rotor mold for pressure forming to obtain a blank.

[0042] In the present application, the mass ratio of the mixed powder to the binder is preferably 1:(0.5-1.5), more preferably 1:(1-1.2). In the present application, the binder is preferably silica sol. By selecting a suitable binder and controlling the amount thereof, the present application can reduce the adverse effects of the binder on the ceramic matrix during sintering while ensuring the formability of the blank, thereby further improving the mechanical properties.

[0043] In the present application, the mass ratio of the mixed powder to water is preferably 100:(10-15), more preferably 100:(11-14), and most preferably 100:(12-13). By controlling the amount of water, the present application can obtain a paste with good fluidity and filling property, which is beneficial to injection molding.

[0044] The present application does not have special limitations on the operation of mixing the mixed powder with the binder and water, and a uniform paste can be obtained by using a stirring method known to those skilled in the art.

[0045] The present application does not have special limitations on the injection and pressure forming operation, and the technical solution of injection molding known to those skilled in the art can be used.

[0046] After the pressure forming is completed, the present application preferably dries the product of the pressure forming to obtain a blank. The present application does not have special limitations on the drying operation, and the water content in the blank can be removed by using a drying device known to those skilled in the art.

[0047] After obtaining the blank, the present application sequentially performs vacuum pre-burning and vacuum hot-press sintering on the blank to obtain a high-performance silicon nitride turbine rotor.

[0048] In the present application, the temperature of the vacuum pre-burning is preferably 1450-1550℃, more preferably 1480-1520℃, and most preferably 1500℃; and the time of the vacuum pre-burning is preferably 20-40min, more preferably 30min. In the present application, the rate of heating to the temperature of the vacuum pre-burning is preferably 25-35℃ / min, more preferably 30℃ / min.

[0049] In the present application, after the vacuum pre-burning is completed, the temperature is not cooled down, but directly heated to the temperature of the vacuum hot-press sintering.

[0050] In the present application, the temperature of the vacuum hot-press sintering is preferably 1750-1850℃, more preferably 1780-1820℃, and most preferably 1800℃; the pressure of the vacuum hot-press sintering is preferably 35-45MPa, more preferably 38-42MPa, and most preferably 40MPa; the time of the vacuum hot-press sintering is preferably 40-60min, more preferably 45-55min, and most preferably 50min; and the rate of heating to the temperature of the vacuum hot-press sintering is preferably 25-35℃ / min, and more preferably 30℃ / min.

[0051] In the present application, the vacuum pre-sintering is performed at a lower temperature, which is conducive to promoting the rearrangement of the particles, and the generated β-silicon nitride crystal grains are interlaced to form closed pores, and then the temperature and pressure are increased to perform the vacuum hot-press sintering, which promotes the liquid phase to flow and fill, eliminates the closed pores, promotes the uniform growth of the crystal grains, and improves the density and comprehensive mechanical properties of the silicon nitride ceramic; and the two-step sintering method can avoid the existence of pores between the abnormally grown crystal grains in one-step sintering to reduce the high-temperature strength.

[0052] After the vacuum hot-press sintering is completed, the product of the vacuum hot-press sintering is preferably cooled to obtain the high-performance silicon nitride turbine rotor.

[0053] The present application also provides the high-performance silicon nitride turbine rotor prepared by the preparation method.

[0054] The high-performance silicon nitride turbine rotor provided by the present application has high density, excellent strength and toughness, and good comprehensive mechanical properties.

[0055] The technical solutions in the present application will be described clearly and completely below with reference to the embodiments in the present application. The described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of the present application.

[0056] Embodiment 1

[0057] A preparation method of a high-performance silicon nitride turbine rotor comprises the following steps:

[0058] (1) mixing silicon nitride powder, boron nitride nanotubes, zirconium oxide powder and lithium oxide source, and then performing ball milling and drying in sequence to obtain a mixed powder;

[0059] The particle size of the silicon nitride powder is 0.5-1μm; the silicon nitride powder is subjected to airflow crushing before use; the feeding rate of the airflow crushing is 800g / min, and the gas pressure is 2MPa;

[0060] The diameter of the boron nitride nanotube is 25 nm, and the length is 1 μm; the mass of the boron nitride nanotube is 1% of the mass of the silicon nitride powder;

[0061] The particle size of the zirconium oxide powder is 0.5-1 μm; the mass of the zirconium oxide powder is 1% of the mass of the silicon nitride powder;

[0062] The lithium oxide source is lithium carbonate; the mass of lithium element in the lithium oxide source is 0.15% of the mass of the silicon nitride powder;

[0063] The ball-to-material ratio of the ball milling is 10:1, the rotation speed is 250 rpm, the ball milling time is 20 h, and the ball milling medium is ethanol;

[0064] (2) After mixing the mixed powder obtained in step (1) with a binder and water, the mixture is injected into a turbine rotor mold for pressure forming and then dried to obtain a blank;

[0065] The binder is silica sol; the mass ratio of the mixed powder to the binder is 1:1.5; and the mass ratio of the mixed powder to water is 100:15;

[0066] (3) The blank obtained in step (2) is sequentially subjected to vacuum pre-baking and vacuum hot-press sintering, and then naturally cooled to room temperature to obtain a high-performance silicon nitride turbine rotor;

[0067] The temperature of the vacuum pre-baking is 1500℃, and the time is 30 min; the heating rate to the temperature of the vacuum pre-baking is 30℃ / min; the temperature of the vacuum hot-press sintering is 1750℃, the pressure of the vacuum hot-press sintering is 35 MPa, the time of the vacuum hot-press sintering is 60 min, and the heating rate to the temperature of the vacuum hot-press sintering is 30℃ / min.

[0068] Example 2

[0069] A method for preparing a high-performance silicon nitride turbine rotor, comprising the following steps:

[0070] (1) Mixing silicon nitride powder, boron nitride nanotubes, zirconium oxide powder, and a lithium oxide source, and then sequentially subjecting the mixture to ball milling and drying to obtain a mixed powder;

[0071] The particle size of the silicon nitride powder is 0.5-1 μm; the silicon nitride powder is subjected to airflow crushing before use; the airflow crushing has a feeding rate of 800 g / min and a gas pressure of 2 MPa;

[0072] The diameter of the boron nitride nanotube is 25 nm, and the length is 1 μm; the mass of the boron nitride nanotube is 3% of the mass of the silicon nitride powder;

[0073] The particle size of the zirconium oxide powder is 0.5-1 μm; the mass of the zirconium oxide powder is 2% of the mass of the silicon nitride powder;

[0074] The lithium oxide source is lithium carbonate; the mass of lithium element in the lithium oxide source is 0.3% of the mass of the silicon nitride powder;

[0075] The ball-to-material ratio of the ball milling is 10:1, the rotating speed is 250 rpm, the ball milling time is 20 h, and the ball milling medium is ethanol;

[0076] (2) After mixing the mixed powder obtained in step (1) with a binder and water, the mixture is injected into a turbine rotor mold for pressure forming and then dried to obtain a blank;

[0077] The binder is silica sol; the mass ratio of the mixed powder to the binder is 1:1.5; and the mass ratio of the mixed powder to water is 100:15;

[0078] (3) After vacuum pre-sintering and vacuum hot-press sintering of the blank obtained in step (2) in sequence, the blank is naturally cooled to room temperature to obtain a high-performance silicon nitride turbine rotor;

[0079] The temperature of the vacuum pre-sintering is 1500℃, the time is 30 min, the heating rate to the temperature of the vacuum pre-sintering is 30℃ / min, the temperature of the vacuum hot-press sintering is 1800℃, the pressure of the vacuum hot-press sintering is 40 MPa, the time of the vacuum hot-press sintering is 50 min, and the heating rate to the temperature of the vacuum hot-press sintering is 30℃ / min.

[0080] Example 3

[0081] A method for preparing a high-performance silicon nitride turbine rotor, comprising the following steps:

[0082] (1) After mixing silicon nitride powder, boron nitride nanotubes, zirconium oxide powder and a lithium oxide source, the mixture is subjected to ball milling and drying in sequence to obtain a mixed powder;

[0083] The particle size of the silicon nitride powder is 0.5-1 μm; the silicon nitride powder is subjected to airflow crushing before use; the feeding rate of the airflow crushing is 800 g / min, and the gas pressure is 2 MPa;

[0084] The diameter of the boron nitride nanotubes is 25 nm, and the length is 1 μm; the mass of the boron nitride nanotubes is 5% of the mass of the silicon nitride powder;

[0085] The particle size of the zirconium oxide powder is 0.5-1 μm; the mass of the zirconium oxide powder is 2% of the mass of the silicon nitride powder;

[0086] The lithium oxide source is lithium carbonate; the mass of lithium element in the lithium oxide source is 0.4% of the mass of the silicon nitride powder;

[0087] The ball milling ball-to-material ratio is 10:1, the rotating speed is 250 rpm, the ball milling time is 20 h, and the ball milling medium is ethanol;

[0088] (2) The mixed powder obtained in step (1) is mixed with a binder and water, and then injected into a turbine rotor mold for pressure forming and drying to obtain a blank;

[0089] The binder is silica sol; the mass ratio of the mixed powder to the binder is 1:1.5; and the mass ratio of the mixed powder to water is 100:15;

[0090] (3) The blank obtained in step (2) is sequentially subjected to vacuum pre-sintering and vacuum hot-press sintering, and then naturally cooled to room temperature to obtain a high-performance silicon nitride turbine rotor;

[0091] The vacuum pre-sintering temperature is 1500℃, the vacuum pre-sintering time is 30 min, the heating rate to the vacuum pre-sintering temperature is 30℃ / min, the vacuum hot-press sintering temperature is 1800℃, the vacuum hot-press sintering pressure is 45 MPa, the vacuum hot-press sintering time is 50 min, and the heating rate to the vacuum hot-press sintering temperature is 30℃ / min.

[0092] Example 4

[0093] A preparation method of a high-performance silicon nitride turbine rotor, comprising the following steps:

[0094] (1) A silicon nitride powder, a boron nitride nanotube, a zirconium oxide powder, and a lithium oxide source are mixed, and then sequentially subjected to ball milling and drying to obtain a mixed powder;

[0095] The particle size of the silicon nitride powder is 0.5-1 μm; the silicon nitride powder is subjected to airflow crushing before use; the airflow crushing feeding rate is 800 g / min, and the gas pressure is 2 MPa;

[0096] The diameter of the boron nitride nanotube is 25 nm, and the length is 1 μm; the mass of the boron nitride nanotube is 6% of the mass of the silicon nitride powder;

[0097] The particle size of the zirconium oxide powder is 0.5-1 μm; the mass of the zirconium oxide powder is 3% of the mass of the silicon nitride powder;

[0098] The lithium oxide source is lithium carbonate; the mass of lithium element in the lithium oxide source is 0.5% of the mass of the silicon nitride powder;

[0099] The ball milling ball-to-material ratio is 10:1, the rotating speed is 250 rpm, the ball milling time is 20 h, and the ball milling medium is ethanol;

[0100] (2) mixing the mixed powder obtained in step (1) with a binder and water, injecting into a turbine rotor mold for pressure forming, drying after pressure forming to obtain a blank;

[0101] The binder is silica sol; the mass ratio of the mixed powder to the binder is 1:1.5; the mass ratio of the mixed powder to water is 100:15;

[0102] (3) vacuum pre-sintering and vacuum hot-press sintering the blank obtained in step (2) in sequence, and naturally cooling to room temperature to obtain a high-performance silicon nitride turbine rotor;

[0103] The temperature of the vacuum pre-sintering is 1500℃, the time is 30min, the heating rate to the temperature of the vacuum pre-sintering is 30℃ / min; the temperature of the vacuum hot-press sintering is 1850℃, the pressure of the vacuum hot-press sintering is 45MPa, the time of the vacuum hot-press sintering is 40min, and the heating rate to the temperature of the vacuum hot-press sintering is 30℃ / min.

[0104] Example 5

[0105] A method for preparing a high-performance silicon nitride turbine rotor, comprising the following steps.

[0106] (1) mixing silicon nitride powder, boron nitride nanotube, zirconium oxide powder and lithium oxide source, and then performing ball milling and drying in sequence to obtain a mixed powder;

[0107] The particle size of the silicon nitride powder is 0.5-1μm; the silicon nitride powder is airflow pulverized before use; the feeding rate of the airflow pulverization is 800g / min, and the gas pressure is 2MPa;

[0108] The diameter of the boron nitride nanotube is 25nm, and the length is 1μm; the mass of the boron nitride nanotube is 7% of the mass of the silicon nitride powder;

[0109] The particle size of the zirconium oxide powder is 0.5-1μm; the mass of the zirconium oxide powder is 3% of the mass of the silicon nitride powder;

[0110] The lithium oxide source is lithium carbonate; the mass of lithium element in the lithium oxide source is 0.7% of the mass of the silicon nitride powder;

[0111] The ball-to-material ratio of the ball milling is 10:1, the rotation speed is 250rpm, the ball milling time is 20h, and the ball milling medium is ethanol;

[0112] (2) mixing the mixed powder obtained in step (1) with a binder and water, injecting into a turbine rotor mold for pressure forming, drying after pressure forming to obtain a blank;

[0113] The binder is silica sol; the mass ratio of the mixed powder to the binder is 1:1.5; and the mass ratio of the mixed powder to water is 100:15.

[0114] (3) vacuum pre-sintering and vacuum hot-press sintering are sequentially performed on the blank obtained in step (2) and then the blank is naturally cooled to room temperature to obtain a high-performance silicon nitride turbine rotor;

[0115] The temperature of the vacuum pre-sintering is 1500 DEG C, the time is 30 min, the rate of heating to the temperature of the vacuum pre-sintering is 30 DEG C / min, the temperature of the vacuum hot-press sintering is 1750 DEG C, the pressure of the vacuum hot-press sintering is 45 MPa, the time of the vacuum hot-press sintering is 40 min, and the rate of heating to the temperature of the vacuum hot-press sintering is 30 DEG C / min.

[0116] Performance test

[0117] The relative densities of the high-performance silicon nitride turbine rotors prepared in Examples 1-5 are respectively tested, and the results are shown in Table 1.

[0118] The high-performance silicon nitride turbine rotors prepared in Examples 1-5 are respectively processed to obtain strip-shaped samples with a size of 3.0 mm x 4.0 mm x 25 mm and single-edge notched beam samples with a size of 2.0 mm x 4.0 mm x 25 mm, a CMT5105 micro-control servo universal testing machine with a span of 20 mm is used to perform three-point bending strength test and fracture toughness test at a loading speed of 0.5 mm / min, and the results are shown in Table 1.

[0119] Table 1: Performance of high-performance silicon nitride turbine rotors in Examples 1-5

[0120] Performance Example 1 Example 2 Example 3 Example 4 Example 5 Density / % 99 98.6 98.3 98.5 98.2 Flexural strength / MPa 935 943 952 948 940 Fracture toughness / MPa-m 1 / 2 ]] 9.0 9.2 9.3 9.1 8.9

[0121] As can be seen from the above examples, the high-performance silicon nitride turbine rotor prepared by the preparation method has high density and excellent mechanical properties.

[0122] The above only describes the preferred embodiments of the present application, and it should be noted that, for those skilled in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, and these improvements and refinements should also be considered as the protection scope of the present application.

Claims

1. A method for preparing a high-performance silicon nitride turbine rotor, characterized in that: For the following steps: (1) mixing silicon nitride powder, boron nitride nanotubes, zirconium oxide powder and a lithium oxide source, and then ball milling and drying in sequence to obtain a mixed powder; The silicon nitride powder has a particle size of 0.5 to 1 μm; the silicon nitride powder is subjected to air flow pulverization before use; the feed rate of the air flow pulverization is 800 g / min, and the gas pressure is 2 MPa; The boron nitride nanotube has a diameter of 25 nm and a length of 1 μm; the mass of the boron nitride nanotube is 5% of the mass of the silicon nitride powder; The particle size of the zirconium oxide powder is 0.5 to 1 μm; the mass of the zirconium oxide powder is 2% of the mass of the silicon nitride powder; The lithium oxide source is lithium carbonate; the mass of lithium element in the lithium oxide source is 0.4% of the mass of silicon nitride powder; The ball-to-material ratio of the ball mill is 10:1, the rotation speed is 250 rpm, the ball milling time is 20 h, and the ball milling medium is ethanol; (2) mixing the mixed powder obtained in step (1) with a binder and water, injecting the mixed powder into a turbine rotor mold, performing press molding, and then drying to obtain a blank; The binder is silica sol; the mass ratio of the mixed powder to the binder is 1:1.5; the mass ratio of the mixed powder to water is 100:15; (3) vacuum pre-sintering and vacuum hot pressing the blank obtained in step (2) and then naturally cooling it to room temperature to obtain a high-performance silicon nitride turbine rotor; The vacuum pre-sintering temperature is 1500°C, the time is 30 minutes, and the heating rate to the vacuum pre-sintering temperature is 30°C / min. The vacuum hot pressing sintering temperature is 1800°C, the vacuum hot pressing sintering pressure is 45 MPa, the vacuum hot pressing sintering time is 50 minutes, and the heating rate to the vacuum hot pressing sintering temperature is 30°C / min. The high performance is bending strength.