Preforming method applied to complex structure of normal-pressure silicon carbide material
By dismantling the complex structural ceramic components into separate parts and designing corresponding molds, and molding and sintering using preforming methods, the problem of difficult to achieve high-quality and low-cost production of complex structures in the prior art is solved, and efficient and low-cost ceramic components are achieved.
Patent Information
- Application Number
- CN202510548515.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-28
- Publication Date
- 2025-06-17
AI Technical Summary
In the molding process of complex structural ceramic components, it is difficult for the prior art to take into account high precision and low cost, especially under the normal pressure sintering process, it is difficult to achieve high-quality and low-cost production of complex structures.
The preforming method is adopted to disassemble the target structure into a split part and a connecting part, and corresponding molds and sintering molds are designed. Through the preset steps of forming, sintering and bonding, integrated sintering is gradually realized to obtain preforms.
Through this method, the molding difficulty is reduced, the production efficiency is improved, the integrity of the complex structure is ensured, the yield rate and the mechanical performance and stability of the product are significantly improved, and the production cost is reduced.
Smart Images
Figure CN120157486A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the technical field of advanced ceramic material forming, and particularly to a preforming method applied to complex structures of atmospheric pressure silicon carbide materials. Background Art
[0002] Atmospheric pressure sintered silicon carbide materials are widely used in extreme working condition fields such as aerospace and semiconductor equipment due to their high strength, high hardness, high temperature resistance, and excellent chemical stability. In recent years, with the continuous progress of industrial technology, the demand for complex structure ceramic components has been increasing.
[0003] Currently, in the forming process of complex structure ceramic components, two main methods are usually adopted: high-pressure forming and machining. High-pressure forming includes processes such as isostatic pressing and hot die casting. These methods achieve material densification by applying high pressure and can effectively improve the forming accuracy. However, such processes require equipment and high-precision molds, resulting in a significant increase in production costs. Machining uses traditional cutting tools to finish the sintered ceramics. Although it can meet certain shape requirements, due to the brittle characteristics of silicon carbide materials, microcracks are easily caused and the yield rate is low. In addition, it is difficult for both of these methods to take into account the integrity control of complex structures. Especially in the production of complex structure ceramic components such as hollow configurations or special-shaped thin-walled parts, the breakage rate of green body demolding is relatively high, seriously affecting production efficiency and economy.
[0004] In the current forming process of complex structure ceramic components, there are generally problems such as high unit cost, low yield rate, and high breakage rate of green body demolding. Especially in the atmospheric pressure sintering process, it is difficult to achieve high-quality and low-cost production of complex structures. Therefore, there is an urgent need for a preforming technology that can reduce production costs and improve the yield rate while ensuring accuracy. Summary of the Invention
[0005] In order to improve the forming quality of preforming of complex structure ceramic components and reduce processing costs, this application provides a preforming method applied to complex structures of atmospheric pressure silicon carbide materials.
[0006] This application provides a preforming method applied to complex structures of atmospheric pressure silicon carbide materials, adopting the following technical solutions: A preforming method applied to complex structures of atmospheric pressure silicon carbide materials, comprising the following steps: Step 1. Raw material preparation: The prepared raw materials include atmospheric pressure sintered silicon carbide powder, sintering aids, binders, and dispersants. The binder contains a mixture of silicon carbide micropowder and polyacrylamide; Step 2. Mold Design: Analyze the target structure, disassemble it into a split part and a connection part, and respectively design a number of forming molds and sintering molds corresponding to the split part and the connection part; Step 3. Preparation of Split Parts: Using the forming mold and the sintering mold, prepare the split part and the connection part respectively through the forming and sintering processes to obtain a split green body and a connection green body; Step 4. Primary Machining: Perform local dimension machining on the split green body and the connection green body to eliminate appearance defects and meet the design dimension requirements; Step 5. Adhesive Pre - setting: After evenly applying the adhesive at the joint of the split green body and the connection green body, perform pre - setting integration to obtain an integrated green body; Step 6. Integrated Sintering: Place the integrated green body in a sintering furnace to complete sintering and obtain a pre - formed part.
[0007] By adopting the above - mentioned technical solution, disassembling the target structure into a split part and a connection part, and respectively designing corresponding forming molds and sintering molds can reduce the overall forming difficulty, improve production efficiency, and at the same time ensure the integrity of the complex target structure. Performing primary machining on the split green body and the connection green body to eliminate appearance defects and meet the design dimension requirements, ensuring the dimensional accuracy of each part, and providing a good foundation for subsequent integrated sintering. Using an adhesive made of a mixture of silicon carbide micropowder and polyacrylamide materials to bond and combine the obtained split green body and connection green body can significantly improve the bonding strength, reduce the generation of micro - cracks, and thus improve the yield. During the integrated sintering process, by performing high - temperature sintering on the integrated green body to obtain a pre - formed part, it is possible to achieve densification of the complex structure while ensuring material properties, further improving the mechanical properties and stability of the product.
[0008] Optionally, it further includes Step 7. Secondary Machining: Perform local dimension machining on the pre - formed part again to eliminate appearance defects.
[0009] By adopting the above - mentioned technical solution, performing secondary machining on the pre - formed part obtained by sintering, using numerical control machining equipment to achieve precise adjustment of local dimensions, effectively eliminating appearance defects, ensuring the smooth and flat surface of the product, and improving the appearance quality and consistency of the final product. It is applicable to the fine machining of complex - structure ceramic components, helping to improve the yield and reduce the rejection rate caused by dimensional deviation.
[0010] Optionally, it further includes Step 8. Post - treatment: Perform heat treatment on the pre - formed part after secondary machining to eliminate residual stress and finally obtain a pre - formed finished product.
[0011] By adopting the above technical solution, heat-treating the preform after secondary processing can effectively eliminate residual stress, thereby enhancing the structural stability and mechanical properties of the preform, reducing the risk of deformation during subsequent use, and ultimately obtaining a high-quality preformed finished product.
[0012] Optionally, the sintering aid includes a carbon source and a boron source.
[0013] By adopting the above technical solution, using the carbon source and the boron source as the sintering aid can effectively promote the growth and densification of grains during atmospheric pressure sintering, improve the sintering activity of the material, thereby improving the mechanical properties and density uniformity of the preform. It can reduce the requirements for sintering temperature, reduce the formation of defects during sintering, and enhance the strength and hardness of the final product.
[0014] Optionally, in the binder, the mass ratio of the silicon carbide micropowder is 10% - 60%.
[0015] By adopting the above technical solution, controlling the mass ratio of the silicon carbide micropowder in the binder within the range of 10% - 60% can effectively improve the bonding strength, while ensuring the fluidity and coating performance of the binder. The binder forms a uniform bonding layer at the joint between the split green body and the connecting green body, thereby improving the structural stability of the integrated green body and reducing the risk of cracking during the preforming process. A reasonable ratio of silicon carbide micropowder can also enhance the high-temperature resistance of the bonding interface, providing a reliable guarantee for the subsequent sintering process.
[0016] Optionally, the dispersant is an alcohol-based polymer, and the addition amount of the dispersant is 0.5% - 3% of the total mass of the raw materials.
[0017] By adopting the above technical solution, selecting an alcohol-based polymer as the dispersant can significantly improve the uniformity and stability of the raw material slurry, reduce the agglomeration phenomenon, thereby enhancing the densification and strength of the green body. Controlling the addition amount of the dispersant within the range of 0.5% - 3% of the total mass of the raw materials can not only ensure the dispersion effect but also avoid the problem of increased residual volatiles during sintering caused by excessive addition, ultimately improving the sintering quality of the preform and reducing the defect rate.
[0018] Optionally, the local dimension processing in Step 4 and Step 7 is completed by a CNC grinding machine or a machining center, and the machining accuracy is controlled within ±0.05 mm.
[0019] By adopting the above technical solution, machining is carried out using a CNC grinding machine or a machining center, ensuring the automation and controllability of the machining process, significantly improving the machining accuracy, controlling the machining error within ±0.05 mm, thus effectively eliminating appearance defects and meeting the design dimension requirements. This machining method not only improves the surface quality of the product but also provides a good foundation for subsequent integrated sintering and heat treatment, further ensuring the forming accuracy and yield rate of complex structure ceramic components.
[0020] Optionally, in the fifth step, the coating thickness of the adhesive is 0.1 - 0.5 mm, and it is left to stand and cure for 1 - 2 hours after pre-integration.
[0021] By adopting the above technical solution, controlling the coating thickness of the adhesive within the range of 0.1 - 0.5 mm can form a uniform adhesive layer at the joint of the split green body and the connecting green body, ensuring the joint strength while avoiding structural defects caused by excessive adhesive. In addition, leaving it to stand and cure for 1 - 2 hours after pre-integration can allow the adhesive to fully infiltrate and initially cure, thereby improving the stability of the integrated green body and reducing the deformation risk during subsequent machining and sintering.
[0022] Optionally, the sintering process parameters in the sixth step are: sintering temperature 1800 - 2100 °C, holding time 2 - 6 hours, and sintering shrinkage rate ≤ 5%.
[0023] By adopting the above technical solution, defining the sintering process parameters as sintering temperature 1800 - 2100 °C, holding time 2 - 6 hours, and sintering shrinkage rate ≤ 5% can effectively improve the densification degree of the atmospheric pressure silicon carbide material, ensuring that the sintered preform has high strength and high hardness properties. At the same time, controlling the sintering temperature and holding time helps to reduce abnormal grain growth and avoid internal stress concentration, thereby enhancing the structural stability and high-temperature resistance of the material. It ensures the dimensional accuracy of the preform, reduces the deformation risk caused by uneven shrinkage, and finally realizes the high-quality and low-cost production of complex structure ceramic components.
[0024] Optionally, the heat treatment conditions in the eighth step are: under argon protection, heating to 800 - 1000 °C at a rate of 5 - 10 °C / min, holding for 1 - 3 hours, and then slowly cooling to room temperature.
[0025] By adopting the above technical solution, heat-treating the preform can effectively prevent oxidation under argon protection, and at the same time ensure uniform temperature distribution at a heating rate of 5-10 °C / min to avoid thermal stress concentration. In the holding temperature range of 800-1000 °C, the internal residual stress of the preform is fully released, and the crystal structure tends to be stable, thereby significantly improving the mechanical properties and dimensional stability of the preformed product. The process of slow cooling to room temperature further reduces the impact of thermal shock on the material and ensures the integrity of the complex structure ceramic component.
[0026] In summary, the present application includes at least one of the following beneficial effects: 1. In the present application, by disassembling the target structure into a split part and a connecting part, and designing corresponding forming molds and sintering molds respectively, the overall forming difficulty can be reduced, the production efficiency can be improved, and at the same time the integrity of the complex structure can be ensured; 2. The present application uses an adhesive containing a mixture of silicon carbide micropowder and polyacrylamide to bond the split green body and the connecting green body, which can significantly improve the bonding strength, reduce the generation of microcracks, and thus improve the yield; 3. In the present application, the split green body and the connecting green body are subjected to primary processing to eliminate appearance defects and meet the design size requirements, ensuring the dimensional accuracy of each part and providing a good foundation for subsequent integrated sintering; 4. In the present application, during the integrated sintering process, by performing high-temperature sintering on the integrated green body to obtain a preform, densification of the complex structure can be achieved while ensuring the material properties, further improving the mechanical properties and stability of the product. BRIEF DESCRIPTION OF THE DRAWINGS
[0027] Figure 1 is a schematic diagram of consecutive steps of a preforming method for a complex structure of an atmospheric pressure silicon carbide material according to Embodiment 1 of the present application; Figure 2 is a schematic diagram of consecutive steps of a preforming method for a complex structure of an atmospheric pressure silicon carbide material according to Embodiment 2 of the present application; Figure 3 is a schematic diagram of consecutive steps of a preforming method for a complex structure of an atmospheric pressure silicon carbide material according to Embodiment 3 of the present application; DETAILED DESCRIPTION OF THE EMBODIMENTS The following will Figure 1 - be Figure 3 further described in detail with reference to the
[0028] Embodiment 1: Referring to Figure 1 , a preforming method for a complex structure of an atmospheric pressure silicon carbide material provided by an embodiment of the present application includes the following steps: Step 1. Raw material preparation: The raw materials prepared include atmospheric pressure sintered silicon carbide powder, sintering aids, binders, and dispersants.
[0029] Among them, the sintering aids are composed of a carbon source and a boron source. The carbon source can be phenolic resin or glucose, and the boron source can be boric acid or boron nitride. The selection of these raw materials can not only improve the sintering efficiency but also effectively control the sintering shrinkage rate. The binder contains silicon carbide micropowder and polyacrylamide, which is made by mixing silicon carbide micropowder and polyacrylamide in a certain proportion. The dispersant is an alcohol-based polymer, such as polyvinyl alcohol or polyethylene glycol, and its addition amount is 0.5%-3% of the total mass of the raw materials, which can effectively improve the fluidity and uniformity of the slurry.
[0030] When mixing silicon carbide micropowder and polyacrylamide, nanoscale silicon carbide micropowder needs to be selected. The particle size of the silicon carbide micropowder is controlled within 50-200nm, and the silicon carbide micropowder is placed in a vacuum drying oven and dried at 120-150°C for 2-4 hours to remove the surface adsorbed moisture. Mix polyacrylamide and deionized water in a mass ratio of 1:5-1:10, and stir in a water bath at 40-60°C until completely dissolved to form a transparent colloidal solution. Slowly add the dried nano-silicon carbide micropowder to the polyacrylamide solution at a mass ratio of 10%-60%. The mass ratio of the silicon carbide micropowder is preferably 35%; at the same time, mechanically stir at a rate of 500-1000r / min to avoid particle agglomeration. The mass ratio of the silicon carbide micropowder in the binder is 10%-60%, which can ensure that the binder has good bonding performance and high-temperature resistance.
[0031] Step 2. Mold design: Analyze the geometric structure of the target structure and disassemble it into a split part and a connection part, and design a number of forming molds and sintering molds corresponding to the split part and the connection part respectively. The specific number of the forming molds and the sintering molds is determined according to the total number of the split part and the connection part obtained by disassembly. The material of the forming mold can be graphite or silicon nitride, and the surface roughness Ra of the inner surface of the forming mold ≤1.6μm to ensure the smooth surface of the green body and reduce the risk of breakage during demolding.
[0032] To improve the durability and demolding performance of the forming mold and the sintering mold, an anti-adhesive coating, such as polytetrafluoroethylene or graphene coating, can be coated on the surfaces of the forming mold and the sintering mold. This surface treatment process can significantly reduce the friction between the green body and the mold, and further reduce the risk of breakage during demolding.
[0033] Step 3. Preparation of split parts: Use the forming mold and the sintering mold to prepare the split part and the connection part through the forming and sintering processes respectively to obtain a split green body and a connection green body.
[0034] During the forming process, the preliminary forming of the split green body and the connecting green body can be achieved by pressing, slip casting, gel casting or other methods. The sintering process parameters are as follows: the sintering temperature is controlled at 1800 - 2100 °C, the holding time is 2 - 6 hours, and the sintering shrinkage rate ≤ 5%. Such sintering conditions can ensure the densification of the green body while avoiding excessive shrinkage deformation.
[0035] Step Four, Primary Machining: Perform local dimension machining on the split green body and the connecting green body to eliminate appearance defects and meet the design dimension requirements. The machining equipment for primary machining can be a CNC grinding machine or a machining center, and the machining accuracy is controlled within ±0.05 mm. Through this high-precision machining, the fitting accuracy between various parts can be ensured, laying a foundation for subsequent bonding pre-setting.
[0036] Step Five, Bonding Pre-setting: After evenly applying the adhesive prepared in Step One at the joint of the split green body and the connecting green body, perform pre-set integration to obtain an integrated green body. When applying the adhesive, the application thickness is 0.1 - 0.5 mm, preferably 0.2 - 0.3 mm. And after pre-set integration, let it stand and cure for 1 - 2 hours.
[0037] Step Six, Integrated Sintering: Place the integrated green body in a sintering furnace to complete sintering and obtain a preform. Use an integrated mold and crucible to translate the integrated green body into a high-temperature sintering furnace for high-temperature sintering. The sintering process parameters are as follows: the sintering temperature is controlled at 1800 - 2100 °C, and the sintering time is adjusted according to the part size and shape.
[0038] Through raw material preparation, mold design, split body preparation, primary machining, bonding pre-setting, integrated sintering, etc. Each step cooperates with each other, achieving the effects of improving the forming quality and reducing the production cost.
[0039] The implementation principle of this embodiment is as follows: By splitting the design, the complex structure is decomposed into multiple simple parts, which are formed and sintered separately, and then integrated through bonding pre-setting. This method can not only effectively control the dimensional accuracy and shape integrity of each part, but also significantly reduce the production cost. In addition, by optimizing the sintering process parameters and the adhesive formula, the quality and performance of the preform can be further improved.
[0040] Example 2: Refer to Figure 2 This embodiment is different from Embodiment 1 in that Step Seven, Secondary Machining, is added: Perform local dimension machining on the preform again to eliminate appearance defects.
[0041] After the integrated sintering is completed, a numerical control processing device is used to perform local dimension processing on the preform again to further eliminate appearance defects. The processing equipment for the secondary processing is also selected as a numerical control grinding machine or a machining center, and the processing accuracy is controlled within ±0.05 mm.
[0042] The implementation principle of this embodiment is: it can further improve the quality and performance of the preform on the basis of integrated sintering. The secondary processing can not only eliminate the tiny defects that may occur during the sintering process, but also ensure the dimensional accuracy and surface finish of the preform, so as to meet the requirements of high-end applications.
[0043] Embodiment 3: Refer to Figure 3 , the difference between this embodiment and Embodiment 2 is that a post-treatment step is added. Step Eight, Post-treatment: The preform after secondary processing is heat-treated to eliminate residual stress, and finally a preformed finished product is obtained.
[0044] After the secondary processing, the preform is heat-treated to eliminate residual stress. The heat treatment conditions are: under argon protection, the temperature is raised to 800 - 1000 °C at a rate of 5 - 10 °C / min, and after holding for 1 - 3 hours, it is slowly cooled to room temperature. This heat treatment method can effectively relieve the residual stress generated during the sintering process and improve the mechanical properties and long-term stability of the preform.
[0045] The implementation principle of this embodiment is: by adding a post-treatment step, while ensuring the dimensional accuracy and surface quality of the finally obtained preformed finished product, the mechanical properties and long-term stability can be further improved. Heat treatment can eliminate the residual stress generated during the sintering process, prevent cracking or deformation problems caused by stress concentration, and thus improve the overall reliability of the preformed finished product.
[0046] Embodiment 4: The difference between this embodiment and Embodiment 1 is that the matching method between the split part and the connecting part is optimized.
[0047] In Step Two, the split part and the connecting part obtained by disassembly are designed to be matched through a mortise and tenon structure or a stepped interface at the connection. Using such a matching method can significantly improve the bonding strength and positioning accuracy.
[0048] The implementation principle of this embodiment is: by optimizing the matching method between the split part and the connecting part, the structural integrity and mechanical properties of the preform can be significantly improved. The mortise and tenon structure or the stepped interface can not only provide reliable positioning, but also effectively disperse the stress concentration at the joint, thereby improving the overall strength and reliability of the preform.
[0049] The above are all preferred embodiments of this application, and the protection scope of this application is not limited thereby. Therefore, all equivalent changes made according to the structure, shape, and principle of this application shall be covered within the protection scope of this application.
Claims
1. A preforming method for complex structures of atmospheric pressure silicon carbide materials, characterized in that: The following steps are involved: Step 1: Raw material preparation: The prepared raw materials include pressure-sintered silicon carbide powder, a sintering aid, a binder and a dispersant, wherein the binder comprises a mixture of silicon carbide micropowder and polyacrylamide; Step 2: Mold design: Analyze the target structure and disassemble it into separate parts and connecting parts, and design several molding molds and sintering molds corresponding to the separate parts and connecting parts respectively; Step 3: Separate preparation: using the molding die and the sintering die, the separate part and the connecting part are prepared respectively through molding and sintering processes to obtain a separate green blank and a connected green blank; Step 4: Initial processing: performing local size processing on the split green blank and the connected green blank to eliminate appearance defects and meet the design size requirements; Step 5: Pre-bonding: after evenly applying the adhesive at the joints of the split green blank and the connected green blank, pre-bonding and integration are performed to obtain an integrated green blank; Step 6: Integrated sintering: placing the integrated green blank in a sintering furnace to complete sintering to obtain a preform.
2. A preforming method for complex structures of atmospheric pressure silicon carbide materials according to claim 1, characterized in that: Also includes step seven, secondary processing: The preform is subjected to local dimension processing again to eliminate appearance defects.
3. A preforming method for complex structures of atmospheric pressure silicon carbide materials according to claim 2, characterized in that: Also includes step eight, post-processing: The preformed part after secondary processing is heat treated to eliminate residual stress, and finally a preformed finished product is obtained.
4. A preforming method for complex structures of atmospheric pressure silicon carbide materials according to claim 3, characterized in that: The sintering aid comprises a carbon source and a boron source.
5. A preforming method for complex structures of atmospheric pressure silicon carbide materials according to claim 4, characterized in that: In the adhesive, the mass proportion of the silicon carbide powder is 10%-60%.
6. A preforming method for complex structures of atmospheric pressure silicon carbide materials according to claim 5, characterized in that: The dispersant is an alcohol polymer, and the added amount of the dispersant is 0.5%-3% of the total mass of the raw materials.
7. A preforming method for complex structures of atmospheric pressure silicon carbide materials according to claim 6, characterized in that: The local dimension processing in step 4 and step 7 is completed by a CNC grinder or a machining center, and the processing accuracy is controlled within ±0.05mm.
8. A preforming method for complex structures of atmospheric pressure silicon carbide materials according to claim 7, characterized in that: In the step 5, the adhesive is applied with a thickness of 0.1-0.5 mm, and is left to cure for 1-2 hours after pre-integration.
9. A preforming method for complex structures of atmospheric pressure silicon carbide materials according to claim 8, characterized in that: The sintering process parameters in step six are: sintering temperature 1800-2100° C., holding time 2-6 hours, and sintering shrinkage rate ≤5%.
10. A preforming method for complex structures of atmospheric pressure silicon carbide materials according to claim 9, characterized in that: The heat treatment conditions in step eight are: under argon protection, heating to 800-1000° C. at a rate of 5-10° C. / min, keeping the temperature for 1-3 hours, and then slowly cooling to room temperature.