A method for preparing uniform infiltration-strengthened 3D-printed silicon carbide ceramic complex preforms

Abstract

This invention discloses a method for preparing complex 3D-printed silicon carbide ceramic preforms with uniform infiltration strengthening. Using these preforms, silicon carbide ceramic materials with high density, high strength, and high toughness can be obtained. This invention utilizes a pre-embedded silicon source, allowing the silicon source pre-placed in the green body during reaction sintering to assist external silicon particles in achieving overall synergistic infiltration of molten silicon into the ceramic green body. This invention can shorten reaction sintering time, improve sintering efficiency, effectively reduce the content and distribution scale of residual silicon, improve the mechanical properties of the sintered body, and solve the problems of insufficient sintering and excessive residual carbon in large-size components. It also has advantages such as simple operation and ease of widespread application.

Description

Technical Field

[0001] This invention belongs to the field of advanced manufacturing technology and material design and preparation technology, specifically involving a method for preparing a 3D printed silicon carbide ceramic complex preform with uniform infiltration strengthening. Background Art

[0002] Silicon carbide possesses advantages such as low density, high strength, and low coefficient of thermal expansion, making it promising for applications in aerospace, semiconductors, and chemicals. In recent years, with advancements in high-end technologies, silicon carbide ceramic components have shown a trend towards larger size, lighter weight, and greater complexity. However, silicon carbide ceramics are characterized by high brittleness and hardness. Traditional processes such as dry pressing, slip casting, and isostatic pressing cannot overcome the limitations imposed by molds on the production of complex silicon carbide components, significantly increasing production costs and reducing efficiency. Laser selective sintering (LSS) technology, based on the discrete-stacking principle, uses a high-energy laser beam to scan the surface of a powder bed according to a pre-set slice model, melting and bonding the powder to form the desired cross-sectional shape. The next layer of powder is then laid and sintered, and the process is repeated layer by layer to create a three-dimensional part.

[0003] Compared to traditional processes, selective laser sintering (SLS) technology eliminates the need for molds, boasts high material utilization, and enables the rapid fabrication of arbitrarily complex structures, significantly shortening product development time and reducing production costs. The fabrication of silicon carbide ceramic parts using SLS first requires preparing a silicon carbide / polymer mixed powder. This powder is then shaped into a ceramic green body using SLS, followed by binder removal to remove organic matter. However, the organic matter in the green body undergoes pyrolysis during binder removal and escapes as gas, resulting in numerous pores within the green body. Therefore, further post-processing strengthening is necessary to obtain fully dense silicon carbide ceramics.

[0004] Currently, densification of pyrolysis-treated green bodies is commonly achieved through methods such as reaction sintering, chemical vapor infiltration, and precursor impregnation pyrolysis. Among these, reaction sintering, with its advantages of low production cost, short preparation cycle, and high densification degree, has become the most commonly used densification method. However, the current method of using selective laser sintering combined with reaction sintering to prepare large-size complex silicon carbide components still faces several challenges: Firstly, large-size complex components typically exhibit uneven wall thickness and large size spans, significantly prolonging the penetration path of molten silicon within the green body during reaction infiltration and reducing sintering efficiency. Secondly, the amorphous carbon within the green body has high reactivity with molten silicon, and the instantaneously generated silicon carbide can clog capillary channels, causing premature closure of the silicon infiltration channels and hindering further penetration of molten silicon into the green body. These problems make large-size components highly susceptible to uneven silicon infiltration during reaction infiltration, which is detrimental to improving the performance of silicon carbide ceramics and their components. Summary of the Invention

[0005] The purpose of this section is to outline some aspects of embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, to avoid obscuring the purpose of these documents; however, such simplifications or omissions should not be construed as limiting the scope of the invention.

[0006] In view of the problems existing in the above and / or prior art, the present invention is proposed.

[0007] Therefore, the purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing 3D printed complex silicon carbide ceramic preforms with uniform infiltration strengthening.

[0008] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a method for preparing a uniformly infiltrated and strengthened 3D-printed complex silicon carbide ceramic preform, comprising,

[0009] Xylene, silicon-rich binder, nylon 12, silicon carbide powder, silicon powder, and graphite powder are mixed, heated in an oil bath, cooled, washed with ethanol, dried, crushed, and sieved to obtain a composite powder.

[0010] The composite powder is added to a laser selective sintering equipment and sintered layer by layer to obtain a green body;

[0011] The green body is carbonized.

[0012] Ethyl silicate solution was added to boron phenolic resin solution and stirred to obtain modified phenolic resin solution;

[0013] By using modified phenolic resin as an impregnation liquid to repeatedly impregnate and carbonize the carbonized green body, a uniformly melt-infiltrated and strengthened 3D printed silicon carbide ceramic complex preform is obtained.

[0014] In a preferred embodiment of the preparation method described in this invention, xylene, a silicon-rich binder, nylon 12, silicon carbide powder, silicon powder, and graphite powder are mixed, wherein the volume ratio of xylene, silicon-rich binder, nylon 12, silicon carbide powder, silicon powder, and graphite powder is 80:4:8:4:2:4; the nylon 12 powder has a particle size of 50 μm, the silicon carbide powder has a particle size of 100–500 nm, the silicon powder has a particle size of 0.5–1 μm, the graphite powder is flake graphite with a particle size of 100–300 nm, and the silicon-rich binder is one or more of polycarbosilane, polysiloxane, methyltrimethoxysilane, and dimethyldimethoxysilane.

[0015] As a preferred embodiment of the preparation method described in this invention, the oil bath heating is performed with a vacuum evacuated, nitrogen as the protective gas, a heating rate of 3-5°C / min, a heating temperature of 134°C, and a holding time of 15min.

[0016] As a preferred embodiment of the preparation method described in this invention, the drying, crushing, and sieving processes include a drying temperature of 70°C, a drying time of 24 hours, and a particle size of 40–70 μm for the composite powder after sieving.

[0017] As a preferred embodiment of the preparation method described in this invention, the composite powder is added to a laser selective sintering (SSS) device and sintered layer by layer to obtain a green body. The powder bed of the SSS device is preheated to 150-160°C, the laser power is set to 8-12W, the printing layer thickness is 0.1-0.2mm, the laser scanning speed is 2000-3500mm / s, and the laser scanning spacing is 0.1-0.2mm.

[0018] As a preferred embodiment of the preparation method of the present invention, the green blank is subjected to carbonization treatment, wherein the carbonization treatment is carried out in an argon atmosphere, the heating rate is 1-2℃ / min, the carbonization temperature is 480℃, and the holding time is 3h.

[0019] In a preferred embodiment of the preparation method described in this invention, the ethyl silicate solution is added to the boron phenolic resin solution and stirred to obtain a modified phenolic resin solution. The boron phenolic resin solution is prepared by mixing boric acid, phenolic resin, and anhydrous ethanol at a mass ratio of 1:1:0.8–4; the ethyl silicate solution is prepared by mixing ethyl silicate and anhydrous ethanol at a mass ratio of 1:0.4–2; the stirring time is 30 min, the stirring rate is 1400 r / min, and the concentration of the modified phenolic resin solution is 70%.

[0020] As a preferred embodiment of the preparation method described in this invention, the modified phenolic resin is used as the impregnation liquid to perform cyclic impregnation carbonization on the carbonized green body. The cyclic impregnation carbonization involves immersing the carbonized green body into an impregnation tank containing modified phenolic resin and placing it in a vacuum impregnation chamber. The vacuum pump is turned on until the pressure inside the vacuum impregnation chamber reaches -0.05 MPa, and the pressure is maintained for 30 minutes. The green body is then removed and cured at 180°C for 1 hour. The cured green body is then placed in a carbonization furnace for a secondary carbonization treatment. The above steps are repeated 1 to 5 times.

[0021] As a preferred embodiment of the preparation method described in this invention, the secondary carbonization process involves placing the prepared green blank in a carbonization furnace, heating it to 850°C at a heating rate of 1-2°C / min under an argon atmosphere, holding it at that temperature for 3 hours, and then cooling it to room temperature with the furnace before removing it.

[0022] Another objective of this invention is to overcome the shortcomings of the prior art and provide a method for preparing highly efficient and dense silicon carbide ceramic components, characterized by comprising:

[0023] Silicon particles are placed on the upper and lower surfaces of the preform, and heated to 1400°C under vacuum at a heating rate of 5-10°C / min, then heated to 1650°C at a heating rate of 2-5°C / min and held at that temperature for 1 hour. After cooling to room temperature at a cooling rate of 5°C / min, the preform is removed to obtain a dense silicon carbide ceramic component. The preform is a uniformly infiltrated and strengthened 3D printed silicon carbide ceramic complex preform prepared by the preparation method described in any one of claims 1-9.

[0024] Beneficial effects of this invention:

[0025] This invention employs a pre-embedded silicon source, which allows the pre-placed silicon source in the green body during the reaction sintering process to assist external silicon particles in achieving overall synergistic penetration of molten silicon into the ceramic green body. This can shorten the reaction sintering time and improve sintering efficiency; it can effectively reduce the content and distribution scale of residual silicon, improve the mechanical properties of the sintered body, and obtain silicon carbide ceramic materials with high density, high strength, and high toughness.

[0026] This invention solves the problems of insufficient sintering and excessive residual carbon in large-sized components, and also has the advantages of simple operation and easy promotion and use. Attached Figure Description

[0027] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0028] Figure 1 This is a process flow diagram of the present invention.

[0029] Figure 2 This is a schematic diagram illustrating the principle of overall silicon infiltration and densification using multiple silicon sources in this invention. DETAILED DESCRIPTION

[0030] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0031] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0032] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0033] Unless otherwise specified, all raw materials used in the embodiments of this invention are commercially available.

[0034] The process flow for manufacturing complex silicon carbide ceramic parts based on 3D printing technology provided by this invention is as follows: Figure 1 As shown. First, silicon carbide powder, graphite powder, silicon-rich binder, nylon 12, and silicon powder are uniformly mixed using a thermally induced phase separation method to prepare a composite powder. The composite powder is then added to the powder spreading cylinder of a laser selective sintering (SSC) device for pre-spreading. The powder bed is preheated to 150–160°C, the laser power is set to 8–12W, the printing layer thickness is 0.1–0.2 mm, the laser scanning speed is 2000–3500 mm / s, and the laser scanning interval is 0.1–0.2 mm. Under the above process parameters, a specific area of ​​the powder bed is sintered layer by layer to obtain the green body. After carbonization treatment, the green body is circulated and impregnated with a modified phenolic resin impregnation solution for carbonization. Finally, after reaction sintering, a silicon carbide ceramic component is obtained.

[0035] During sintering, the densification principle of the preform is as follows: Figure 2 As shown. At high temperature, molten silicon on the upper and lower surfaces of the preform penetrates into the interior of the preform through capillary force. Simultaneously, silicon powder and organosilicon in the preform also melt and diffuse outwards. During this process, the carbon source inside the preform undergoes a dissolution and precipitation reaction, forming silicon carbide with silicon. The secondary silicon carbide first nucleates on the capillary wall and continues to grow, resulting in uniform closure of the capillary channels and densification of the preform.

[0036] Example 1

[0037] (1) Preparation of composite powder:

[0038] Xylene was poured into a reaction vessel, followed by the addition of polycarbosilane, nylon 12, silicon carbide powder, silicon powder, and graphite powder in that order. The volume ratio of xylene, polycarbosilane, nylon 12, silicon carbide powder, silicon powder, and graphite powder was 80:4:8:4:2:4. The reaction vessel was then evacuated and nitrogen was introduced as a protective gas. The mixture was heated to 134°C using an oil bath at a rate of 3°C / min and held at that temperature for 15 minutes. The heating system was then turned off, and the mixture was allowed to cool naturally to room temperature. The resulting mixture was repeatedly washed with ethanol and then placed in a drying oven at 70°C for 24 hours. After crushing and sieving, a composite powder was obtained.

[0039] (2) SLS green forming:

[0040] The composite powder is added to the powder spreading cylinder of the laser selective sintering equipment for pre-spreading. The powder bed is preheated to 150°C, the laser power is set to 8W, the layer thickness is set to 0.1mm, the printing speed is set to 2000mm / s, and the scanning interval is set to 0.2mm. Under the above process parameters, the powder bed is sintered layer by layer in a specific area to obtain a green body.

[0041] (3) Carbonization treatment of green body:

[0042] The prepared green body is placed in a carbonization furnace and heated to 850°C at a heating rate of 1°C / min under an argon atmosphere, and then held at that temperature for 3 hours for carbonization treatment.

[0043] (4) Preparation of modified resin:

[0044] Boric acid, phenolic resin, and anhydrous ethanol were mixed in a mass ratio of 1:1:0.8. The mixture was stirred in a magnetic stirrer for 30 minutes to synthesize a boron-phenolic resin solution. Similarly, ethyl silicate was mixed with anhydrous ethanol in a mass ratio of 1:0.4 to prepare an ethyl silicate solution. This ethyl silicate solution was then slowly added to the boron-phenolic resin solution as a modifier and stirred vigorously at room temperature for 30 minutes to prepare a 28% modified phenolic resin solution.

[0045] (5) Cyclic impregnation carbonization:

[0046] The carbonized preform is immersed in a container filled with modified phenolic resin and placed in a vacuum impregnation chamber. The vacuum pump is turned on until the pressure inside the vacuum impregnation chamber reaches -0.05 MPa, and the pressure is maintained for 30 minutes. The preform is then removed and cured at 180°C for 1 hour. The cured preform is placed in a graphite crucible and then placed in a tube furnace. Under an argon atmosphere, it is heated to 850°C at a heating rate of 2°C / min and held at that temperature for 3 hours. Then, it is cooled to room temperature in the furnace and removed. The above steps are repeated four times to obtain the preform.

[0047] (6) Reactive sintering densification:

[0048] Silicon particles were placed on the upper and lower surfaces of the preform and heated to 1400°C under vacuum at a heating rate of 10°C / min. Then, the preform was heated to 1650°C at a heating rate of 2°C / min and held at that temperature for 1 hour. After cooling to room temperature at a cooling rate of 5°C / min, the preform was removed to obtain a dense silicon carbide ceramic component.

[0049] The silicon carbide ceramic component obtained according to this embodiment has a tested bulk density of 2.82 g·cm³. -3(Measured using Archimedes' displacement method according to national standard GB / T 25995-2010), the flexural strength reaches 265.12 MPa (three-point bending, measured according to national standard GB / T 4741-1999), and the fracture toughness is 3.59 MPa·m. 0.5 (Measured using the fracture beam method, based on national standard GB / T 23806-2009).

[0050] Example 2

[0051] (1) Preparation of composite powder:

[0052] Xylene was poured into a reaction vessel, followed by the addition of methyltrimethoxysilane, nylon 12, silicon carbide powder, silicon powder, and graphite powder in that order. The volume ratio of xylene, methyltrimethoxysilane, nylon 12, silicon carbide powder, silicon powder, and graphite powder was 80:4:8:4:2:4. The reaction vessel was then evacuated and nitrogen was introduced as a protective gas. The mixture was heated to 134°C using an oil bath at a rate of 5°C / min and held at that temperature for 15 minutes. The heating system was then turned off, and the mixture was allowed to cool naturally to room temperature. The resulting mixture was repeatedly washed with ethanol and then placed in a drying oven at 70°C for 24 hours. After crushing and sieving, a composite powder was obtained.

[0053] (2) SLS green forming:

[0054] The composite powder is added to the powder spreading cylinder of the laser selective sintering equipment for pre-spreading. The powder bed is preheated to 150°C, the laser power is set to 12W, the layer thickness is set to 0.15mm, the printing speed is set to 3000mm / s, and the scanning interval is set to 0.1mm. Under the above process parameters, the powder bed is sintered layer by layer in a specific area to obtain a green body.

[0055] (3) Carbonization treatment of green body:

[0056] The prepared green body is placed in a carbonization furnace and heated to 850°C at a heating rate of 2°C / min under an argon atmosphere, and then held at that temperature for 3 hours for carbonization treatment.

[0057] (4) Preparation of modified resin:

[0058] Boric acid, phenolic resin, and anhydrous ethanol were mixed in a mass ratio of 1:1:4. The mixture was stirred in a magnetic stirrer for 30 minutes to synthesize a boron-phenolic resin solution. Similarly, ethyl silicate was mixed with anhydrous ethanol in a mass ratio of 1:2 to prepare an ethyl silicate solution. This ethyl silicate solution was then slowly added to the boron-phenolic resin solution as a modifier and stirred vigorously at room temperature for 30 minutes to prepare a modified phenolic resin solution with a concentration of 67%.

[0059] (5) Cyclic impregnation carbonization:

[0060] The carbonized preform is immersed in a container filled with modified phenolic resin and placed in a vacuum impregnation chamber. The vacuum pump is turned on until the pressure inside the vacuum impregnation chamber reaches -0.05 MPa, and the pressure is maintained for 30 minutes. The preform is then removed and cured at 180°C for 1 hour. The cured preform is placed in a graphite crucible and then placed in a tube furnace. Under an argon atmosphere, it is heated to 850°C at a heating rate of 2°C / min and held at that temperature for 3 hours. Then, it is cooled to room temperature with the furnace and removed. The above steps are repeated twice to obtain the preform.

[0061] (6) Reactive sintering densification:

[0062] Silicon particles were placed on the upper and lower surfaces of the preform and heated to 1400°C under vacuum at a heating rate of 5°C / min. Then, the temperature was increased to 1650°C at a heating rate of 5°C / min and held for 1 hour. The preform was then cooled to room temperature at a cooling rate of 5°C / min and removed to obtain a dense silicon carbide ceramic component.

[0063] The silicon carbide ceramic component obtained according to this embodiment has a tested bulk density of 2.89 g·cm³. -3 The bending strength reached 268.02 MPa, and the fracture toughness was 3.60 MPa·m. 0.5 .

[0064] Example 3

[0065] (1) Preparation of composite powder:

[0066] Xylene was poured into a reaction vessel, followed by the addition of polysiloxane, nylon 12, silicon carbide powder, silicon powder, and graphite powder in that order. The volume ratio of xylene, polysiloxane, nylon 12, silicon carbide powder, silicon powder, and graphite powder was 80:4:8:4:2:4. The reaction vessel was then evacuated and nitrogen was introduced as a protective gas. The mixture was heated to 134°C using an oil bath at a rate of 3.5°C / min and held at that temperature for 15 minutes. The heating system was then turned off, and the mixture was allowed to cool naturally to room temperature. The resulting mixture was repeatedly washed with ethanol and then placed in a drying oven at 70°C for 24 hours. After crushing and sieving, a composite powder was obtained.

[0067] (2) SLS green forming:

[0068] The composite powder is added to the powder spreading cylinder of the laser selective sintering equipment for pre-spreading. The powder bed is preheated to 155°C, the laser power is set to 12W, the layer thickness is set to 0.15mm, the printing speed is set to 2800mm / s, and the scanning interval is set to 0.15mm. Under the above process parameters, the powder bed is sintered layer by layer in a specific area to obtain a green body.

[0069] (3) Carbonization treatment of green body:

[0070] The prepared green body is placed in a carbonization furnace and heated to 850°C at a heating rate of 2°C / min under an argon atmosphere, and then held at that temperature for 3 hours for carbonization treatment.

[0071] (4) Preparation of modified resin:

[0072] Boric acid, phenolic resin, and anhydrous ethanol were mixed in a mass ratio of 1:1:2. The mixture was stirred in a magnetic stirrer for 30 minutes to synthesize a boron-phenolic resin solution. Similarly, ethyl silicate and anhydrous ethanol were mixed in a mass ratio of 1:1 to prepare an ethyl silicate solution. This ethyl silicate solution was then slowly added to the boron-phenolic resin solution as a modifier and stirred vigorously at room temperature for 30 minutes to prepare a 50% modified phenolic resin solution.

[0073] (5) Cyclic impregnation carbonization:

[0074] The carbonized preform is immersed in a container filled with modified phenolic resin and placed in a vacuum impregnation chamber. The vacuum pump is turned on until the pressure inside the vacuum impregnation chamber reaches -0.05 MPa, and the pressure is maintained for 30 minutes. The preform is then removed and cured at 180°C for 1 hour. The cured preform is placed in a graphite crucible and then placed in a tube furnace. Under an argon atmosphere, it is heated to 850°C at a heating rate of 2°C / min and held at that temperature for 3 hours. Then, it is cooled to room temperature with the furnace and removed. The above steps are repeated twice to obtain the preform.

[0075] (6) Reactive sintering densification:

[0076] Silicon particles were placed on the upper and lower surfaces of the preform and heated to 1400°C under vacuum at a heating rate of 10°C / min. Then, the preform was heated to 1650°C at a heating rate of 6°C / min and held at that temperature for 1 hour. After cooling to room temperature at a cooling rate of 5°C / min, the preform was removed to obtain a dense silicon carbide ceramic component.

[0077] The silicon carbide ceramic component obtained according to this embodiment has a tested bulk density of 2.92 g·cm³. -3 The bending strength reached 270.02 MPa, and the fracture toughness was 3.62 MPa·m. 0.5 .

[0078] Comparative Example 1

[0079] (1) Preparation of composite powder:

[0080] Nylon 12 and silicon carbide powder were mixed at a mass ratio of 15:85.

[0081] (2) SLS green forming:

[0082] The composite powder is added to the powder spreading cylinder of the laser selective sintering equipment for pre-spreading. The powder bed is preheated to 160°C, the laser power is set to 10W, the layer thickness is set to 0.15mm, the printing speed is set to 2200mm / s, and the scanning interval is set to 0.15mm. Under the above process parameters, the powder bed is sintered layer by layer in a specific area to obtain a green body.

[0083] (3) Carbonization treatment of green body:

[0084] The prepared green body is placed in a carbonization furnace and heated to 850°C at a heating rate of 2°C / min under an argon atmosphere, and then held at that temperature for 3 hours for carbonization treatment.

[0085] (4) Preparation of impregnation solution:

[0086] Phenolic resin and anhydrous ethanol were mixed at a mass ratio of 1:1. The mixture was stirred in a magnetic stirrer for 30 minutes to prepare a 50% phenolic resin solution.

[0087] (5) Cyclic impregnation carbonization:

[0088] The carbonized preform is immersed in a container filled with phenolic resin and placed in a vacuum impregnation chamber. The vacuum pump is turned on until the pressure inside the vacuum impregnation chamber reaches -0.05 MPa, and the pressure is maintained for 30 minutes. The preform is then removed and cured at 180°C for 1 hour. The cured preform is placed in a graphite crucible and then placed in a tube furnace. Under an argon atmosphere, it is heated to 850°C at a heating rate of 2°C / min and held at that temperature for 3 hours. Then, it is cooled to room temperature with the furnace and removed. The above steps are repeated twice to obtain the preform.

[0089] (6) Reactive sintering densification:

[0090] Silicon particles were placed on the upper and lower surfaces of the preform and heated to 1400°C under vacuum at a heating rate of 10°C / min. Then, the preform was heated to 1650°C at a heating rate of 6°C / min and held at that temperature for 1 hour. After cooling to room temperature at a cooling rate of 5°C / min, the preform was removed to obtain a dense silicon carbide ceramic component.

[0091] The silicon carbide ceramic component obtained according to this embodiment has a tested bulk density of 2.53 g·cm³. -3 The bending strength reached 204.71 MPa, and the fracture toughness was 2.87 MPa·m. 0.5 .

[0092] Table 1 shows a comparison of the properties of the silicon carbide ceramics prepared in Examples 1-3 with those prepared in Comparative Example 1.

[0093] Table 1

[0094]

[0095] Comparative Example 2

[0096] The difference between this comparative example and Example 1 is that the volume ratio of xylene, polycarbosilane, nylon 12, silicon carbide powder, silicon powder and graphite powder in step (1) is 80:2:8:4:4:4. The remaining steps are the same as in Example 1.

[0097] Comparative Example 3

[0098] The difference between this comparative example and Example 1 is that polycarbosilane was not used in the preparation of the composite powder in step (1), and the volume ratio of xylene, nylon 12, silicon carbide powder, silicon powder and graphite powder was 80:12:4:2:4. The remaining steps were the same as in Example 1.

[0099] Comparative Example 4

[0100] The difference between this comparative example and Example 1 is that the modified resin solution in steps (4) and (5) is replaced with 40% concentration phenolic resin 2133, while the other steps are the same as in Example 1.

[0101] The materials obtained in Comparative Examples 2 to 4 were subjected to performance testing, and the testing methods were the same as in Example 1. The performance comparisons are shown in Table 2.

[0102] Table 2

[0103]

[0104] To address the aforementioned shortcomings or improvement needs of existing laser selective sintering methods for manufacturing silicon carbide ceramic preforms, this invention provides a method for preparing complex 3D-printed silicon carbide ceramic preforms with uniform infiltration strengthening. This method employs a simultaneous reaction and infiltration of external silicon particles and internal silicon powder at high temperatures. The external silicon particles infiltrate from the outside in and react with carbon to form silicon carbide, while the internal silicon source infiltrates uniformly from the inside and reacts with the remaining silicon source. This synergistic infiltration and densification method using multiple silicon sources achieves post-processing strengthening of complex silicon carbide ceramic components manufactured through additive manufacturing. The silicon source pre-placed in the preform assists the external silicon particles in achieving overall synergistic infiltration of molten silicon into the ceramic preform during the reaction sintering process, thereby obtaining high-performance, dense silicon carbide ceramic components. This avoids the problems of incomplete sintering of thick-walled parts and slow, uneven infiltration of large parts when using only external silicon particles for infiltration. The preparation method is simple to operate, easy to promote and use, and produces silicon carbide ceramics with excellent performance, suitable for manufacturing large, complex silicon carbide ceramic components.

[0105] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the present invention.

Claims

1. A method for preparing a complex 3D-printed silicon carbide ceramic preform with uniform infiltration strengthening, characterized in that: include, Xylene, silicon-rich binder, nylon 12, silicon carbide powder, silicon powder, and graphite powder are mixed, heated in an oil bath, cooled, washed with ethanol, dried, crushed, and sieved to obtain a composite powder. The composite powder is added to a laser selective sintering equipment and sintered layer by layer to obtain a green body; Carbonize the green body; Ethyl silicate solution was added to boron phenolic resin solution and stirred to obtain modified phenolic resin solution; By using modified phenolic resin as an impregnation liquid to repeatedly impregnate and carbonize the carbonized green body, a uniformly melt-infiltrated and strengthened 3D printed silicon carbide ceramic complex preform is obtained. The mixture comprises xylene, a silicon-rich binder, nylon 12, silicon carbide powder, silicon powder, and graphite powder, wherein the volume ratio of xylene, silicon-rich binder, nylon 12, silicon carbide powder, silicon powder, and graphite powder is 80:4:8:4:2:4; the nylon 12 powder has a particle size of 50 μm, the silicon carbide powder has a particle size of 100~500 nm, the silicon powder has a particle size of 0.5~1 μm, the graphite powder is flake graphite with a particle size of 100~300 nm, and the silicon-rich binder is one or more of polycarbosilane, polysiloxane, methyltrimethoxysilane, and dimethyldimethoxysilane; The ethyl silicate solution is added to the boron phenolic resin solution and stirred to obtain a modified phenolic resin solution. The boron phenolic resin solution is prepared by mixing boric acid, phenolic resin, and anhydrous ethanol at a mass ratio of 1:1:0.8-4 until homogeneous. The ethyl silicate solution is prepared by mixing ethyl silicate and anhydrous ethanol at a mass ratio of 1:0.4-2 until homogeneous. The stirring time is 30 min, the stirring speed is 1400 r / min, and the concentration of the modified phenolic resin solution is 70%. The oil bath heating process involves evacuating the oil bath under vacuum, using nitrogen as a protective gas, with a heating rate of 3-5°C / min, a heating temperature of 134°C, and a holding time of 15min.

2. The preparation method according to claim 1, characterized in that: The drying, crushing, and sieving processes are carried out, with the drying temperature at 70℃ and the drying time at 24h. The particle size of the composite powder after sieving is 40~70 μm.

3. The preparation method according to claim 1, characterized in that: The composite powder is added to a laser selective sintering (SSS) device and sintered layer by layer to obtain a green body. The powder bed of the SSS device is preheated to 150-160°C, the laser power is set to 8-12W, the printing layer thickness is 0.1-0.2 mm, the laser scanning speed is 2000-3500 mm / s, and the laser scanning spacing is 0.1-0.2 mm.

4. The preparation method according to claim 1, characterized in that: The green blank is subjected to carbonization treatment, wherein the carbonization treatment is carried out in an argon atmosphere, the heating rate is 1~2 ℃ / min, the carbonization temperature is 480℃, and the holding time is 3h.

5. The preparation method according to claim 1, characterized in that: The modified phenolic resin is used as the impregnation liquid to perform cyclic impregnation carbonization on the carbonized green body. The cyclic impregnation carbonization involves immersing the carbonized green body into an impregnation tank containing modified phenolic resin and placing it in a vacuum impregnation chamber. The vacuum pump is turned on until the pressure in the vacuum impregnation chamber reaches -0.05 MPa, and the pressure is maintained for 30 min. The green body is then removed and cured at 180°C for 1 h. The cured green body is then placed in a carbonization furnace for a second carbonization treatment. The above steps are repeated 1 to 5 times.

6. The preparation method according to claim 5, characterized in that: The secondary carbonization process involves placing the prepared green blank in a carbonization furnace, heating it to 850°C at a heating rate of 1-2°C / min under an argon atmosphere, holding it at that temperature for 3 hours, and then cooling it to room temperature with the furnace before removing it.

7. A method for preparing a dense silicon carbide ceramic component, characterized in that: include, Silicon particles are placed on the upper and lower surfaces of the preform, and heated to 1400°C under vacuum at a heating rate of 5-10°C / min, then heated to 1650°C at a heating rate of 2-5°C / min and held at that temperature for 1 hour. After cooling to room temperature at a cooling rate of 5°C / min, the preform is removed to obtain a dense silicon carbide ceramic component. The preform is a uniformly infiltrated and strengthened 3D printed silicon carbide ceramic complex preform prepared by any one of the preparation methods described in claims 1-6.

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