Method for preparing high-performance silicon carbide ceramic through selective laser sintering

Abstract

The invention belongs to the technical field of ceramic material additive manufacturing, and particularly relates to a method for preparing high-performance silicon carbide ceramic through selective laser sintering, which comprises the following steps: heating and stirring silicon carbide powder, resin and a solvent to obtain homogeneous slurry, spraying the slurry into liquid nitrogen through an atomizer to obtain frozen microspheres, and sintering the frozen microspheres to obtain the high-performance silicon carbide ceramic. And then removing the residual solvent through freeze drying to obtain the silicon carbide / resin integrated composite microspheres for selective laser sintering, and after selective laser sintering molding, carrying out low-temperature carbonization pre-sintering and high-temperature liquid silicon reaction infiltration to obtain compact silicon carbide ceramic. According to the method, the ceramic / resin integrated composite microspheres obtained through freeze spray granulation have very excellent additive applicability, silicon carbide nanoparticles are reserved in a green body to achieve dispersion strengthening and toughening, the structure of the selective laser sintering silicon carbide ceramic material is homogenized, and the purpose of improving the comprehensive mechanical property of the selective laser sintering silicon carbide ceramic material is achieved.

Description

Technical Field

[0001] The present invention relates to the field of additive manufacturing of silicon carbide ceramic materials, and in particular to a method for preparing high-performance silicon carbide ceramics by laser selective sintering. Background Art

[0002] Silicon carbide ceramics have excellent room-temperature mechanical properties, such as high flexural strength, excellent oxidation resistance, good corrosion resistance, high wear resistance, and a low coefficient of friction. They have a wide range of applications, but traditional processing techniques can no longer meet the requirements for the molding of highly complex structural parts. The emergence of additive manufacturing technology has provided a new processing method for the preparation of ceramics with highly complex and lightweight structures. Selective laser sintering (SLS) technology is considered to be the most suitable additive manufacturing molding technology for ceramic materials. The process involves evenly mixing ceramic powder with a low-melting-point phase, melting the low-melting-point phase under the thermal effect of the laser, and bonding the ceramic powder to achieve molding. SLS technology breaks the traditional processing model. Based on the three-dimensional model data of a part or object, the molding equipment is used to accumulate materials to form physical parts. It solves the processing and manufacturing problems of lightweight and complex structural parts such as porous, hollow, and lattice parts that are difficult to solve with traditional manufacturing technologies.

[0003] Nano-ceramic composites are composite materials made by effectively dispersing and compounding nanoparticles so that they are uniformly dispersed within a ceramic matrix. Existing research indicates that increasing the grain size from micron to submicron and then to nanometer levels can significantly improve the strength and toughness of ceramic materials, thereby enhancing their overall mechanical properties. However, nanopowders are difficult to print due to agglomeration and electrostatic forces between the powder-laying roller and the powder.

[0004] The Chinese invention patent application CN10618719B discloses a method for preparing a silicon carbide ceramic part using a laser selective sintering process, comprising the following steps: weighing carbon powder, silicon carbide powder, a binder, and a curing agent according to a predetermined mass ratio, pouring them into a ball mill, and ball milling them to obtain a binder-silicon carbide mixed powder; using a computer to perform three-dimensional digital modeling of the part to be prepared, and inputting the three-dimensional digital model information into a laser selective sintering forming machine; using the binder-silicon carbide mixed powder as a raw material, powder sintering is performed using a laser selective sintering rapid prototyping process to obtain a silicon carbide blank of the part; heating and curing the silicon carbide blank; placing the cured silicon carbide blank in a medium-temperature tubular sintering furnace protected by Ar for carbonization treatment to obtain a porous silicon carbide blank; and performing melt infiltration sintering on the porous silicon carbide blank under vacuum to obtain a dense silicon carbide ceramic part.

[0005] A Chinese invention patent application, authorized by publication number CN114394836B, discloses a method for preparing nanocrystalline silicon carbide ceramics using phase-inversion microspheres (SLS). First, using nano-silicon carbide powder as the raw material, silicon carbide ceramic microspheres with a particle size of 40-100 μm are prepared using phase-inversion technology. The silicon carbide ceramics are then formed using SLS technology. Finally, densification is achieved through degreasing, carbonization, pre-sintering, and liquid silicon infiltration to produce the silicon carbide ceramics.

[0006] In summary, the current traditional processing methods are difficult to achieve the production of ceramic materials with complex structures and lightweight structures, and the general SLS preparation of silicon carbide ceramic materials is difficult to achieve the processing and forming of nano-scale powders. Therefore, it is of great significance to study the silicon carbide nanopowder granulation method and realize laser selective sintering to prepare high-performance silicon carbide ceramics. Summary of the Invention

[0007] In response to the shortcomings of the existing technology, the present invention provides a method for preparing high-performance silicon carbide ceramics by laser selective sintering. In this method, silicon carbide / resin composite microspheres are first prepared by a spray low-temperature freezing method, and then silicon carbide ceramic green bodies are formed by SLS technology. After low-temperature degreasing and carbonization in a vacuum tube furnace, high-temperature liquid silicon reaction infiltration is finally used to obtain high-performance silicon carbide ceramics with silicon carbide nanoparticle dispersion strengthening and toughening.

[0008] To achieve the above object, the present invention provides a method for preparing high-performance silicon carbide ceramics by laser selective sintering, characterized in that the method comprises the following steps:

[0009] (1) Silicon carbide powder, a binder, and a solvent are placed in a conical flask in a certain proportion, and the flask is placed in a water bath to keep warm. At the same time, a stirring rod connected to an electric stirrer is inserted into the flask and stirred continuously for 6 to 10 hours to obtain a homogeneous slurry with a certain viscosity, wherein the mass fraction of silicon carbide powder is 25 to 40%, the mass fraction of the binder is 5 to 20%, and the mass fraction of the solvent is 35 to 60%;

[0010] (2) the homogeneous slurry obtained in step (1) is added to a slurry cylinder after vacuum defoaming, and sprayed into a container containing liquid nitrogen through a spray device. At ultra-low temperature, the slurry droplets are instantly frozen to retain a spherical shape, and then the frozen SiC / resin composite microsphere powder is filtered out and placed in a freeze dryer for 24 to 48 hours to remove the solvent, wherein the spray pressure is controlled at 10 to 100 Pa, the nozzle diameter is 0.4 to 1 mm, and the freeze dryer temperature is -40 to -70 ° C.;

[0011] (3) vibrating and screening the freeze-dried SiC / resin composite microspheres obtained in step (2) to obtain SiC / resin composite microspheres with a particle size distribution of 30 to 100 μm;

[0012] (4) constructing an SLS printing model by computer design, exporting it into an STL file format, importing it into an SLS additive manufacturing system, and then adding the powder obtained in step (3) into a powder tank for printing to obtain a silicon carbide ceramic green body, wherein the laser power is 5-10W, the scanning speed is 1500-2000mm / s, the powder layer thickness is 50-200μm, the scanning spacing is 50-100μm, and the powder bed preheating temperature is 40-150℃;

[0013] (5) placing the silicon carbide ceramic green body printed in step (4) in a tubular furnace, introducing nitrogen / argon, and performing low-temperature degreasing to completely carbonize the binder. The temperature is controlled at 600°C to 1000°C, the heating rate is 1 to 3°C / min, and the holding time is 1 to 3 hours;

[0014] (6) The silicon carbide ceramic green body sintered and carbonized in step (5) is placed in Si powder, and liquid silicon reaction infiltration is carried out in a vacuum siliconizing furnace, wherein the siliconizing temperature is maintained at 1400-1700° C., and finally a high-performance silicon carbide ceramic with nano-silicon carbide particle dispersion strengthening and toughening is obtained.

[0015] Furthermore, the average particle size of the silicon carbide powder in step (1) is 50 to 1000 nm.

[0016] The binder in the further described step (2) is one of polystyrene powder, polyethersulfone, and phenolic resin, and the solvent is one of N-methyl-2-pyrrolidone, tert-butanol, and chloroform.

[0017] Beneficial effects

[0018] (1) The present invention can not only prepare silicon carbide ceramic microspheres with high sphericity and high dispersibility through spray freezing technology, but also retain nano-scale silicon carbide particles;

[0019] (2) The solvent is removed using a freeze dryer, retaining the SiC / resin integrated composite structure, which can be directly used for additive manufacturing. This solves the problem of uneven mixing of the binder and ceramic powder, further reduces defects in printed parts, and improves the product quality and printing speed of printed parts.

[0020] (3) Silicon carbide is generated in situ by the high-temperature liquid silicon reactive infiltration method in the printed parts after carbonization pre-sintering, achieving the dispersion strengthening and toughening of nano-silicon carbide particles, further improving the comprehensive mechanical properties of SLS-printed silicon carbide ceramics.

[0021] In summary, the method of the present invention not only meets the requirements of highly complex and lightweight structures, but also retains the toughening effect of nano-ceramic particle dispersion strengthening. Combined with siliconization reaction melt infiltration densification, high-performance silicon carbide ceramic components can be prepared to meet the use requirements of the aerospace field or other complex environment fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a schematic diagram of a freezing spray granulation device provided by the present invention: 1 is the air supply system, 2 is the air circuit, 3 is the ceramic slurry storage tank, 4 is the slurry conveying route, 5 is the atomizing nozzle system, 6 is the liquid nitrogen insulation interlayer, and 7 is the liquid nitrogen container and the ceramic microsphere collection container.

[0023] Figure 2 This is a schematic diagram of a SiC / resin integrated composite structure provided by the present invention: 1 is resin, and 2 is SiC particles.

[0024] Implementation Examples

[0025] The present invention is further illustrated below with reference to specific examples. It should be understood that these examples are only used to illustrate the present invention and are not used to limit the scope of the present invention. After reading the present invention, modifications of various equivalent forms of the present invention made by those skilled in the art are all within the scope of the claims attached to this application.

[0026] Example 1

[0027] (1) Silicon carbide ceramic powder with an average particle size of 200 nm, polystyrene powder, and chloroform were placed in a conical flask at a mass ratio of 3:1:6, and the flask was placed in a water bath for insulation. At the same time, a stirring rod connected to an electric stirrer was inserted into the flask and stirred continuously for 8 h to obtain a homogeneous slurry with a certain viscosity;

[0028] (2) The homogeneous slurry obtained in step (1) is added to a slurry cylinder after vacuum defoaming, and sprayed into a container containing liquid nitrogen through a spray device. At ultra-low temperature, the slurry droplets are instantly frozen to retain a spherical shape. The frozen silicon carbide microsphere powder is then filtered out and placed in a freeze dryer for 48 hours to remove the solvent, wherein the spray pressure is controlled at 20 Pa, the nozzle diameter is 0.8 mm, and the freeze drying temperature is -70°C;

[0029] (3) vibrating and screening the freeze-dried SiC / polystyrene composite microspheres in step (2) to obtain SiC / polystyrene composite microspheres with a particle size distribution of 30 to 100 μm;

[0030] (4) constructing an SLS printing model by computer design, exporting it into an STL file format, importing it into an SLS additive manufacturing system, and then adding the SiC / polystyrene composite microspheres obtained in step (3) into the powder cylinder for printing to obtain a silicon carbide ceramic green body, wherein the laser power is 5W, the scanning speed is 1500mm / s, the powder layer thickness is 150μm, the scanning spacing is 150μm, and the powder bed preheating temperature is 40℃;

[0031] (6) The silicon carbide ceramic green body printed in step (5) is placed in a tube furnace, argon is introduced, and low-temperature degreasing is performed to carbonize the binder. The temperature is controlled at 800°C, the heating rate is 2°C / min, and the holding time is 1 hour;

[0032] (7) The silicon carbide ceramic green body sintered and carbonized in step (6) is placed in Si powder and subjected to liquid silicon reaction infiltration in a vacuum siliconizing furnace, wherein the siliconizing temperature is maintained at 1500° C., and finally a high-performance silicon carbide ceramic with nano-silicon carbide particle dispersion strengthening and toughening is obtained.

[0033] Example 2

[0034] (1) Silicon carbide ceramic powder with an average particle size of 200 nm, phenolic resin, and tert-butyl alcohol were placed in a conical flask in a mass ratio of 3:1:6, and the flask was placed in a water bath for insulation. At the same time, a stirring rod connected to an electric stirrer was inserted into the flask and stirred continuously for 8 h to obtain a homogeneous slurry with a certain viscosity;

[0035] (2) The homogeneous slurry obtained in step (1) is added to a slurry cylinder after vacuum defoaming, and sprayed into a container containing liquid nitrogen through a spray device. At ultra-low temperature, the slurry droplets are instantly frozen to retain a spherical shape. The frozen silicon carbide microsphere powder is then filtered out and placed in a freeze dryer for 48 hours to remove the solvent, wherein the spray pressure is controlled at 20 Pa, the nozzle diameter is 0.8 mm, and the freeze drying temperature is -50°C;

[0036] (3) vibrating and screening the freeze-dried SiC / phenolic resin composite microspheres obtained in step (2) to obtain SiC / phenolic resin composite microspheres having a particle size distribution of 30 to 100 μm;

[0037] (5) constructing an SLS printing model by computer design, exporting it into an STL file format, importing it into an additive manufacturing system, and then adding the SiC / phenolic resin composite microspheres obtained in step (4) into the powder cylinder for printing to obtain a silicon carbide ceramic green body, wherein the laser power is 8W, the scanning speed is 1500mm / s, the powder layer thickness is 150μm, the scanning spacing is 150μm, and the powder bed preheating temperature is 60℃;

[0038] (6) The silicon carbide ceramic green body printed in step (5) is placed in a tube furnace, argon is introduced, and low-temperature degreasing is performed to carbonize the binder. The temperature is controlled at 800°C, the heating rate is 2°C / min, and the holding time is 2h;

[0039] (7) The silicon carbide ceramic green body sintered and carbonized in step (6) is placed in Si powder and subjected to liquid silicon reaction infiltration in a vacuum siliconizing furnace, wherein the siliconizing temperature is maintained at 1500° C., and finally a high-performance silicon carbide ceramic with nano-silicon carbide particle dispersion strengthening and toughening is obtained.

[0040] The above is only a specific embodiment of the present invention, but the design concept of the present invention is not limited to this. Any non-substantial modification of the present invention using this concept shall be deemed an infringement of the scope of protection of the present invention. However, any simple modification, equivalent change, and modification of the above embodiment made in accordance with the technical essence of the present invention without departing from the content of the technical solution of the present invention shall still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for preparing high-performance silicon carbide ceramics by laser selective sintering, characterized in that: The method comprises the following steps: (1) Silicon carbide powder, a binder, and a solvent are placed in a conical flask in a certain proportion, and the flask is placed in a water bath to keep warm. At the same time, a stirring rod connected to an electric stirrer is inserted into the flask and stirred continuously for 6 to 10 hours to obtain a homogeneous slurry with a certain viscosity, wherein the mass fraction of silicon carbide powder is 25 to 40%, the mass fraction of the binder is 5 to 20%, and the mass fraction of the solvent is 35 to 60%; (2) the homogeneous slurry obtained in step (1) is added to a slurry cylinder after vacuum defoaming, and sprayed into a container containing liquid nitrogen through a spray device. At ultra-low temperature, the slurry droplets are instantly frozen to retain a spherical shape, and then the frozen SiC / resin composite microsphere powder is filtered out and placed in a freeze dryer for 24 to 48 hours to remove the solvent, wherein the spray pressure is controlled at 10 to 100 Pa, the nozzle diameter is 0.4 to 1 mm, and the freeze dryer temperature is -40 to -70 ° C.; (3) vibrating and screening the freeze-dried SiC / resin composite microspheres obtained in step (2) to obtain SiC / resin composite microspheres with a particle size distribution of 30 to 100 μm; (4) constructing an SLS printing model by computer design and exporting it into an STL file format, and then importing it into an SLS additive manufacturing system, and then adding the powder obtained in step (3) into a powder cylinder for printing to obtain a silicon carbide ceramic green body, wherein the laser power is 5 to 10 W, the scanning speed is 1500 to 2000 mm / s, the powder layer thickness is 50 to 200 μm, the scanning spacing is 50 to 100 μm, and the powder bed preheating temperature is 40 to 150 ° C; (5) placing the silicon carbide ceramic green body printed in step (4) in a tubular furnace, introducing nitrogen / argon, and performing low-temperature degreasing to completely carbonize the binder. The temperature is controlled at 600°C to 1000°C, the heating rate is 1 to 3°C / min, and the holding time is 1 to 3 hours; (6) The silicon carbide ceramic green body sintered and carbonized in step (5) is placed in Si powder, and liquid silicon reaction infiltration is carried out in a vacuum siliconizing furnace, wherein the siliconizing temperature is maintained at 1400-1700° C., and finally a high-performance silicon carbide ceramic with nano-silicon carbide particle dispersion strengthening and toughening is obtained.

2. The method for preparing high-performance silicon carbide ceramics by selective laser sintering according to claim 1, characterized in that: The average particle size of the silicon carbide powder described in step (1) is 50 to 1000 nm.

3. The method for preparing high-performance silicon carbide ceramics by selective laser sintering according to claim 1, characterized in that: The binder described in step (1) is one of polystyrene powder, polyethersulfone resin, and phenolic resin, and the solvent is one of N-methyl-2-pyrrolidone, tert-butanol, and chloroform.

Images