A semi-coated silicon carbide graphite piece and a method of making the same
By setting a composite gradient material layer and stress relief groove on the surface of the graphite matrix, the problem of stress accumulation caused by the difference in thermal expansion coefficients between silicon carbide and graphite is solved, realizing a semi-coated silicon carbide graphite part with high flatness and high stability, and reducing production costs.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- 湖南德智新材料股份有限公司
- Filing Date
- 2026-04-24
- Publication Date
- 2026-07-17
AI Technical Summary
During the preparation and service of semi-coated silicon carbide graphite parts, the stress mismatch caused by the difference in the thermal expansion coefficients of silicon carbide and graphite leads to the accumulation of internal stress, which affects the assembly accuracy and service life of the product.
A composite gradient material layer and a stress relief groove are set on the surface of a graphite matrix. The composite gradient material layer buffers the sudden change in the coefficient of thermal expansion, and the stress relief groove releases the internal stress. Combined with a constant temperature stress relief process, the residual stress is completely released.
It significantly improves the flatness and stability of semi-coated silicon carbide graphite parts, reduces machining requirements, lowers production costs, and is suitable for mass production.
Smart Images
Figure CN122404033A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of graphite materials technology, specifically to a semi-coated silicon carbide graphite part and its preparation method. Background Technology
[0002] Semi-coated silicon carbide graphite parts combine the excellent thermal conductivity and high temperature resistance of graphite with the high hardness, wear resistance, and corrosion resistance of silicon carbide coatings. They are widely used in semiconductor wafer carriers, precision mechanical parts, high-temperature furnaces, and other fields. In particular, six-inch and eight-inch disk-ring type integrated products have become core components in high-end manufacturing fields due to their strong overall structure and high assembly precision.
[0003] During the fabrication and subsequent service of semi-coated silicon carbide graphite parts, the significant difference in thermal expansion coefficients between silicon carbide and graphite leads to a mismatch in the thermal contraction / expansion rates between the silicon carbide coating and the graphite substrate, resulting in persistent internal stress at the interface. This internal stress cannot be released through existing conventional processes, and its long-term accumulation causes irreversible deformation of the graphite parts, failing to meet the requirements of precision equipment, severely affecting the assembly accuracy and service life of the products, and even causing malfunctions in core equipment. Summary of the Invention
[0004] To address the shortcomings of existing technologies, this invention provides a semi-coated silicon carbide graphite part and its preparation method. The semi-coated silicon carbide graphite part of this invention reduces stress generation at the coating-substrate interface and stress accumulation within the substrate, exhibiting high flatness and high stability.
[0005] To achieve the above objectives, the first aspect of the present invention provides a semi-coated silicon carbide graphite part, comprising a graphite substrate, wherein the surface of the graphite substrate is composed of a working surface and a non-working surface, wherein a composite gradient material layer and a silicon carbide layer are sequentially disposed on the working surface, the composite gradient material layer completely covers the working surface, and a stress relief groove is disposed on the non-working surface. The stress relief groove includes at least one of annular groove, radial groove, and spiral groove. The composite gradient material layer contains at least one of silicon carbide-graphite composite material, silicon carbide-alumina composite material, and silicon carbide-yttrium oxide composite material. The mass content of silicon carbide in the composite gradient material layer increases linearly from the graphite matrix side to the silicon carbide layer side.
[0006] The second aspect of this invention provides a method for preparing the semi-coated silicon carbide graphite part described in the first aspect of this invention, comprising the following steps: (1) Matrix pretreatment: The non-working surface of the graphite matrix is finely machined, and then stress relief grooves are machined on the non-working surface of the graphite matrix; (2) Preparation of composite gradient material layer: The components of the composite gradient material layer are mixed according to the mass fraction of each component to prepare a slurry. The slurry is sprayed onto the working surface of the graphite substrate, dried and sintered to obtain a graphite part with a composite gradient material layer. (3) Preparation of silicon carbide layer: A silicon carbide layer is deposited on the surface of the composite gradient material layer of the graphite part obtained in step (2), and then gradient cooling is performed to obtain a graphite part with silicon carbide coating. (4) Finishing treatment: Polish the surface of the silicon carbide coating of the graphite part obtained in step (3) to obtain a semi-coated silicon carbide graphite part.
[0007] Implementing the technical solution of the present invention has at least the following beneficial effects: (1) Solving stress problems from the root cause and making deformation control more stable: This invention eliminates the abrupt change in the thermal expansion coefficient of silicon carbide and graphite through a composite gradient material layer, and reduces the generation of internal stress from the source by combining the structural buffer of the stress relief groove; then, through a dedicated constant temperature stress relief process, the residual stress is completely released, avoiding secondary deformation caused by residual stress, and the stability is significantly improved.
[0008] (2) Higher flatness accuracy, no need for excessive machining: The flatness accuracy of semi-coated silicon carbide graphite parts produced by existing technology is low after machining and is easily affected by subsequent stress. Through the synergistic optimization of structure and process, the flatness of the finished product can be directly controlled within 0.02mm, requiring only slight polishing and no large amount of material removal, thus ensuring the integrity of the silicon carbide coating and the structural strength of the product.
[0009] (3) The process is simpler and the production cost is lower: The present invention does not require repeated adjustment of coating preparation parameters. The gradient buffer layer coating, pre-sintering and subsequent stress release processes can be connected with the existing coating deposition process. No new complex equipment is required. At the same time, the mechanical processing steps are reduced, production efficiency is improved and the overall production cost is reduced, making it suitable for large-scale production.
[0010] The endpoints and any values of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of the various ranges, the endpoint values of the various ranges and individual point values, and individual point values can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein. Attached Figure Description
[0011] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.
[0012] Figure 1This is a process flow diagram for preparing semi-coated silicon carbide graphite parts according to the present invention.
[0013] Figure 2 This is a top view of the non-working surface of the semi-coated silicon carbide graphite part prepared in Embodiment 1 of the present invention.
[0014] Figure 3 This is a top view of the working surface of the semi-coated silicon carbide graphite part prepared in Embodiment 1 of the present invention.
[0015] Figure 4 This is a cross-sectional view of the semi-coated silicon carbide graphite part prepared in Example 1 of the present invention.
[0016] Figure 5 for Figure 3 A partial cross-sectional view of the semi-coated silicon carbide graphite part prepared in Example 1 of the present invention.
[0017] Figure 6 This is a top view of the non-working surface of the semi-coated silicon carbide graphite part prepared in Embodiment 2 of the present invention.
[0018] The accompanying drawings have illustrated specific embodiments of the invention, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the invention in any way, but rather to illustrate the concept of the invention to those skilled in the art through reference to particular embodiments. Detailed Implementation
[0019] The present application will be further described below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the present application.
[0020] The endpoints and any values of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of the various ranges, the endpoint values of the various ranges or individual point values, and individual point values can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.
[0021] In the description of this application, "same chemical composition" should be interpreted broadly, that is, the main components of the two have the same chemical composition, or the two have substantially the same chemical composition, but may have errors or impurities within the acceptable range that can be understood by those skilled in the art.
[0022] In the description of this application, "A and / or B" can include any of the cases of A alone, B alone, or A and B, where A and B are merely examples and can be any technical feature connected by "and / or" in this application.
[0023] Unless otherwise specified, the terms "comprising" and "including" as used in this invention can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.
[0024] Unless otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions.
[0025] Unless otherwise specified, all technical features and optional technical features of this invention can be combined to form new technical solutions.
[0026] Unless otherwise specified, all steps of the present invention may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order; for example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.
[0027] The first aspect of this invention provides a semi-coated silicon carbide graphite part, such as Figures 2-6 As shown, it includes a graphite matrix, the surface of which is composed of a working surface (such as...). Figure 3 (as shown) and non-working surfaces (such as) Figure 2 As shown, the working surface is provided with a composite gradient material layer and a silicon carbide layer in sequence, the composite gradient material layer completely covers the working surface, and the non-working surface is provided with a stress relief groove; the silicon carbide layer is located on the surface of the composite gradient material layer.
[0028] The stress relief groove includes at least one of annular groove, radial groove, and spiral groove. The composite gradient material layer contains at least one of silicon carbide-graphite composite material, silicon carbide-alumina composite material, and silicon carbide-yttrium oxide composite material. The mass content of silicon carbide in the composite gradient material layer increases linearly from the graphite matrix side to the silicon carbide layer side.
[0029] When the graphite matrix of a semi-coated silicon carbide graphite part tends to deform due to internal stress, the stress relief groove absorbs the stress through micro-structural deformation, preventing stress accumulation within the matrix. Simultaneously, it provides a buffer space for stress transfer at the interface, preventing warping deformation caused by stress concentration. The semi-coated silicon carbide graphite part utilizes a gradient change in the mass content of silicon carbide in the composite gradient material layer, causing the coefficient of thermal expansion of the composite gradient material layer to gradually transition from a low value on the graphite matrix side to a high value on the silicon carbide layer side. This eliminates abrupt changes in the coefficient of thermal expansion between the two, fundamentally reducing thermal stress at the interface.
[0030] Specifically, the gradient change in silicon carbide mass content in the composite gradient material layer is as follows: in the thickness direction, the silicon carbide mass content continuously transitions from the graphite matrix to the silicon carbide layer, and increases linearly. The graphite matrix side is the portion of the composite gradient material layer close to the graphite matrix, ranging from 0 mm to 0.05 mm away from the graphite matrix, for example, within any two points of 0 mm, 0.01 mm, 0.03 mm, 0.05 mm, or more; wherein, the silicon carbide mass content at 0 mm from the graphite matrix is the silicon carbide mass content of the gradient material layer at the interface.
[0031] The silicon carbide layer side is the portion of the composite gradient material layer close to the silicon carbide layer, with a distance of 0mm to 0.05mm from the silicon carbide layer, for example, between any two points of 0mm, 0.01mm, 0.03mm, 0.05mm or above; wherein, the mass content of silicon carbide at 0mm from the silicon carbide layer is the mass content of silicon carbide in the gradient material layer at the interface.
[0032] In one specific embodiment, the width of the stress relief groove is 0.5mm to 2mm, for example, within the range of any two points between 0.5mm, 1mm, 1.5mm, 2mm or more, and the groove depth is 1 / 5 to 1 / 3 of the thickness of the graphite matrix, for example, within the range of any two points between 1 / 5, 1 / 4, 1 / 3 or more, and the groove depth of the stress relief groove is not less than 1mm.
[0033] If the width of the stress relief groove is less than 0.5 mm, the deformation space and stress buffering capacity it can provide are limited, and it cannot effectively absorb and dissipate internal stress, causing stress to accumulate inside the matrix and making it difficult to prevent overall warping. If the width of the stress relief groove is greater than 2 mm, it will significantly reduce the effective load-bearing cross-sectional area of the graphite matrix, resulting in a significant decrease in the overall mechanical strength and stiffness of the matrix. The stress concentration effect at the edge of the stress relief groove will be more significant, causing cracks to initiate and propagate directly from the edge of the groove, thus becoming the origin of structural failure.
[0034] If the depth of the stress relief groove is less than 1 / 5 of the thickness of the graphite matrix and less than 1 mm, it cannot effectively guide and contain the deep stress from the coating-matrix interface, resulting in incomplete stress relief and ultimately warping deformation. If the depth of the stress relief groove is greater than 1 / 3 of the thickness of the graphite matrix, it will significantly reduce the remaining effective load-bearing thickness of the matrix, causing its bending strength and overall structural stability to drop sharply. When the area of the stress relief groove is subjected to stress, cracks are very likely to initiate from the bottom of the groove and propagate rapidly, leading to through-fracture of the matrix.
[0035] In one specific embodiment, when the stress relief groove is a combination of the annular groove and the radial groove, such as... Figure 2 As shown, the stress relief groove includes at least one annular groove and several radial grooves. The annular groove and the radial grooves are concentrically arranged with the rotation center of the graphite matrix. The radial grooves radiate outward from the rotation center and are connected to the annular groove. The number of annular grooves is 1 to 3, for example, 1, 2, or 3, and the number of radial grooves is 4 to 8, for example, 4, 5, 6, 7, or 8.
[0036] The purpose of setting the stress relief groove as an annular groove is to interrupt the continuous stress ring generated in the tangential direction in the rotationally symmetrical matrix due to thermal expansion mismatch, thus preventing the unimpeded transmission and accumulation of stress within the entire range of the stress ring. Setting multiple concentric annular grooves divides the matrix radially into multiple concentric annular regions, decomposing the overall warpage risk of the silicon carbide graphite part into multiple local annular zones with more easily controlled micro-deformations, thereby achieving graded stress release. If the number of annular grooves exceeds three, it will weaken the integrity and mechanical strength of the matrix, and too many annular grooves do not show significant effects in stress segmentation and release.
[0037] The radial groove design of the stress relief grooves serves to address the issue that, under frequent high- and low-temperature cycling, a temperature gradient exists from the center to the edge of the silicon carbide graphite part as it cools from a high temperature. Furthermore, the constraint conditions on the coating and substrate differ at different radial locations, resulting in radial stress. The radial grooves provide a low-resistance path for releasing this radial stress, while multiple radial grooves ensure uniform stress release in all directions. If the number of radial grooves is less than four, uneven stress release will result due to a lack of directionality; if the number of radial grooves is more than eight, it will severely compromise the structural stiffness and overall load-bearing capacity of the silicon carbide graphite part substrate, without significantly improving the stress release effect.
[0038] If the annular groove and the radial groove are combined, the stress relief groove can simultaneously cope with complex stresses in the tangential, radial and shear directions, providing a clear pre-defined guide for the microscopic deformation of the matrix material under stress, ensuring that the deformation occurs in a predictable and localized manner near the groove structure, thereby protecting the flatness of the working surface.
[0039] In one specific embodiment, when the stress relief groove is a spiral groove, such as... Figure 6 As shown, the spiral groove extends outward from the rotation center of the graphite matrix. The purpose of setting the stress relief groove as a spiral groove is to provide a direct and efficient release channel for tangential and radial stresses within the matrix, achieving synchronous and continuous stress relief in different directions. It is particularly suitable for the balanced release of stress across the entire area of large-sized disc-ring workpieces, avoiding localized stress concentration.
[0040] In one specific embodiment, the thickness of the composite gradient material layer is 0.05 mm to 0.15 mm, for example, within any two of the following ranges: 0.05 mm, 0.07 mm, 0.1 mm, 0.12 mm, 0.15 mm, or more.
[0041] In one specific embodiment, the thickness of the silicon carbide layer is 0.1 mm to 0.5 mm, for example, within any two points of 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm or above.
[0042] In one specific embodiment, the silicon carbide-graphite composite material comprises silicon carbide, graphite, and a binder; based on the total mass of the composite gradient material layers, the silicon carbide mass content on the graphite matrix side is 10%~30% (e.g., within any two points of 10%, 15%, 20%, 25%, 30%, or higher), and the graphite mass content is 62%~87% (e.g., within any two points of 62%, 67%, 75%, 80%, 87%, or higher); the silicon carbide mass content on the silicon carbide layer side... The content percentage is 80%~90% (e.g., within any two points of 80%, 82%, 85%, 87%, 90% or above), and the mass percentage of graphite is 2%~17% (e.g., within any two points of 2%, 6%, 11%, 17% or above); the mass percentage of the binder in the composite gradient material layer is 3%~8% (e.g., within any two points of 3%, 5%, 7%, 8% or above); the binder includes at least one of phenolic resin, furan resin, and epoxy resin.
[0043] If the silicon carbide mass content on the graphite matrix side is less than 10%, the coefficient of thermal expansion of the material in this region is not effectively reduced, resulting in an overly steep transition in the coefficient of thermal expansion from the graphite matrix to the composite gradient material layer, which cannot act as a buffer. Stress will still be generated in large quantities at the interface between the matrix and the composite gradient material layer, and the adhesion between the composite gradient material layer and the graphite matrix is also insufficient. If the silicon carbide mass content on the graphite matrix side is greater than 30%, the coefficient of thermal expansion of the material in this region is significantly lower than that of the graphite matrix, which will cause high bonding stress and cracking risk at the interface between the composite gradient material layer and the matrix. Furthermore, the overall toughness of the composite gradient material layer is insufficient, resulting in a reduced ability of the resulting workpiece to withstand mechanical or thermal shock.
[0044] If the silicon carbide mass content on the silicon carbide layer side is less than 80%, the thermal expansion coefficient of the material in this area is still significantly different from that of the silicon carbide layer, failing to fully achieve the buffering effect of interfacial stress. The silicon carbide layer still has a high risk of peeling or cracking, and the high temperature resistance and oxidation resistance of this area cannot meet the requirements of the coating deposition process. If the silicon carbide mass content on the silicon carbide layer side is higher than 90%, the transition effect between the composite gradient material layer and the silicon carbide layer is poor. The excessively high silicon carbide content makes the toughness of this area insufficient, which can easily lead to the generation and propagation of cracks under stress.
[0045] In one specific embodiment, the silicon carbide-alumina composite material comprises silicon carbide, alumina, and a binder. Based on the total mass of the composite gradient material layer, the alumina content on the graphite matrix side is 10%~20% (e.g., within any two of 10%, 13%, 17%, 20%, or higher), and the silicon carbide content is 72%~87% (e.g., within any two of 72%, 78%, 83%, 87%, or higher). The alumina content on the silicon carbide layer side is 0%~5% (e.g., within any two of 0%, 3%, 5%, or higher), and the silicon carbide content is 87%~97% (e.g., within any two of 87%, 90%, 93%, 97%, or higher). The binder in the composite gradient material layer has a mass percentage of 3%~8% (e.g., within any two of 3%, 5%, 8%, or higher), and the binder includes at least one of phenolic resin, silicone resin, and borosilicate resin.
[0046] Aluminum oxide (A₂O₃) has a higher coefficient of thermal expansion than silicon carbide (SiC). Therefore, the coefficient of thermal expansion of the composite gradient material layer initially increases slightly and then decreases gradually. If the mass content of A₂O₃ on the graphite matrix side is less than 10%, the coefficient of thermal expansion of the composite gradient material layer cannot be effectively increased to a level higher than that of the graphite matrix, thus failing to achieve a transition effect. If the mass content of A₂O₃ on the graphite matrix side is greater than 20%, the difference in the coefficient of thermal expansion between the composite gradient material layer and the graphite matrix is too large. During cooling, the shrinkage in this region is much greater than that of the matrix, generating huge tensile stress at the interface between the composite gradient material layer and the matrix, leading to interfacial peeling or cracking of the composite gradient material layer itself. If the mass content of A₂O₃ on the SiC layer side is greater than 5%, the difference in the coefficient of thermal expansion between the composite gradient material layer and the SiC layer is too large, reintroducing interfacial stress and increasing the risk of coating peeling. In addition, unfavorable phases such as aluminosilicates formed at high temperatures by A₂O₃ and SiC layers also seriously affect the high-temperature strength and long-term stability of the interface.
[0047] The second aspect of this invention provides a method for preparing the semi-coated silicon carbide graphite part described in the first aspect of this invention, the process flow diagram of which is shown below. Figure 1 As shown, it includes the following steps: (1) Matrix pretreatment: The non-working surface of the graphite matrix is finely machined, and then stress relief grooves are machined on the non-working surface of the graphite matrix; (2) Preparation of composite gradient material layer: The components of the composite gradient material layer are mixed according to the mass fraction of each component to prepare a slurry. The slurry is sprayed onto the working surface of the graphite substrate, dried and sintered to obtain a graphite part with a composite gradient material layer. (3) Preparation of silicon carbide layer: A silicon carbide layer is deposited on the surface of the composite gradient material layer of the graphite part obtained in step (2), and then gradient cooling is performed to obtain a graphite part with silicon carbide coating. (4) Finishing treatment: Polish the surface of the silicon carbide coating of the graphite part obtained in step (3) to obtain a semi-coated silicon carbide graphite part.
[0048] In one specific embodiment, after the graphite substrate undergoes the finishing process, the initial flatness of the non-working surface is ≤0.01mm.
[0049] In one specific embodiment, after the graphite substrate is precision machined, it is subjected to ultrasonic cleaning and drying.
[0050] In one specific embodiment, during the preparation of the composite gradient material layer, the slurry preparation method of the composite gradient material layer is as follows: the components of the composite gradient material layer are prepared according to the linear gradient increase ratio of silicon carbide mass content, and composite gradient material layer powders of n gradient segments are prepared respectively, and mixed to obtain n parts of slurry, wherein the mass content of silicon carbide in the n parts of slurry increases linearly; wherein n takes a positive integer and n≥3.
[0051] In one specific embodiment, the n parts of slurry are sequentially sprayed onto the working surface of the graphite substrate in an increasing linear gradient order, and the slurry is dried at 120℃~180℃ for 2h~4h after spraying.
[0052] In one specific embodiment, the sintering process is as follows: under the protection of an inert gas, the temperature is raised to 800℃~1000℃ at a rate of 5℃ / min~10℃ / min, and held for 3h~5h.
[0053] In one specific embodiment, the process of depositing the silicon carbide layer adopts a chemical vapor deposition process or a physical vapor deposition process, and the deposition temperature is 1100℃~1300℃.
[0054] In one specific embodiment, the gradient cooling process is as follows: S1. Cool from the deposition temperature to 750℃~850℃ at a rate of 3℃ / min~5℃ / min, and hold for 1.5h~2.5h; S2. Cool to 450℃~550℃ at a rate of 2℃ / min~3℃ / min, and hold at that temperature for 3h~5h. The specific temperature can be any range between two points: 450℃, 500℃, 550℃, or higher. Alternatively, cool to 250℃~350℃ at a rate of 2℃ / min~3℃ / min, and hold for 7h~9h. The temperature can specifically be a range between any two points of 250°C, 300°C, 350°C or above. S3. Cool to room temperature at a rate of 5℃ / min to 8℃ / min.
[0055] During the fabrication of the silicon carbide layer, the difference in thermal expansion coefficients between graphite and silicon carbide leads to the accumulation of significant stress at their interface. When the temperature drops to 450℃~550℃, the stress reaches a level sufficient to effectively drive the microscopic relaxation process within the material, i.e., the temperature range required for stress activation. Holding at this temperature allows for the transformation of residual stress into permanent deformation through microscopic plastic deformation or viscous flow, thereby achieving full release of the stress. Temperatures above 550℃ will cause coating oxidation; temperatures below 450℃ will result in insufficient stress activation.
[0056] In one specific embodiment, the surface flatness of the polished silicon carbide coating is ≤0.02mm.
[0057] The present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.
[0058] Unless otherwise specified, the experimental methods used in the following examples are conventional methods; unless otherwise specified, the reagents and materials used in the following examples are commercially available.
[0059] Example 1 A method for preparing a semi-coated silicon carbide graphite part includes the following steps: (1) Matrix pretreatment: A graphite part with a thickness of 4mm is used as the graphite matrix. The upper surface of the graphite part is the working surface, and the lower surface and side surface are the non-working surfaces.
[0060] The non-working surfaces of the graphite substrate are precision machined to ensure that the initial flatness of both the working and non-working surfaces is ≤0.01mm. Then, stress relief grooves are machined on the lower surface of the graphite substrate. Specifically, two annular grooves are machined at 1 / 3 and 2 / 3 of the radius from the rotation center, and six evenly distributed radial grooves are machined on the lower surface. The radial grooves are connected to the annular grooves. The grooves are 1mm wide and 1.1mm deep (in this embodiment, the groove depth is 0.275 times the thickness of the graphite substrate). After machining, ultrasonic cleaning and drying are performed.
[0061] (2) Preparation of composite gradient material layer: The components of the composite gradient material layer are prepared according to the linear gradient ratio of the mass content of each component. Three gradient segments of composite gradient material layer powder are prepared, namely graphite matrix side, intermediate layer and silicon carbide layer side. Anhydrous ethanol is added to each gradient segment powder at a solid-liquid ratio of 1:0.5. The mixture is stirred at 3000r / min for 2h to obtain three uniformly dispersed slurries.
[0062] Based on the total mass of the composite gradient material layers, the specific mass content of the slurry is as follows (this embodiment is for n=3): Graphite matrix side: Slurry 1, silicon carbide content is 15% by mass, graphite content is 79% by mass, and phenolic resin content is 6% by mass; Intermediate layer: Slurry 2, with silicon carbide accounting for 50% by mass, graphite accounting for 44% by mass, and phenolic resin accounting for 6% by mass; Silicon carbide layer side: slurry 3, silicon carbide mass content is 85%, graphite mass content is 9%, phenolic resin is 6%.
[0063] The three slurries were sprayed onto the upper surface of the graphite substrate in a linear gradient increasing order, and then dried at 140°C for 3 hours. After drying, the temperature was raised to 900°C at a rate of 8°C / min under argon protection and held for 4 hours to obtain a graphite part with a composite gradient material layer. The thickness of the composite gradient material layer was 0.1 mm. (3) Preparation of silicon carbide layer: A silicon carbide layer is deposited on the surface of the composite gradient material layer of the graphite part obtained in step (2) by chemical vapor deposition process. The source gas is hydrogen and methyltrichlorosilane. The deposition temperature is 1200℃, the deposition pressure is 2500Pa, and the deposition time is 20h. A silicon carbide layer with a thickness of 0.3mm is obtained. Then, gradient cooling is performed to obtain a graphite part with silicon carbide coating.
[0064] The gradient cooling process is as follows: the temperature is reduced from the deposition temperature to 800℃ at a rate of 4℃ / min and held for 2 hours; the temperature is reduced to 500℃ at a rate of 2.5℃ / min and held for 4 hours; and the temperature is reduced to room temperature at a rate of 6℃ / min.
[0065] (4) Finishing treatment: Polish the surface of the silicon carbide coating of the graphite part obtained in step (3) to make the surface flatness of the silicon carbide coating ≤0.02mm, and obtain a semi-coated silicon carbide graphite part.
[0066] Example 2 Semi-coated silicon carbide graphite parts were obtained using the preparation method provided in Example 1, with the following differences: During the substrate pretreatment process, the stress relief groove processed on the lower surface of the non-working surface of the graphite substrate is a spiral groove. This spiral groove is an Archimedean spiral vortex groove, starting at a diameter of 20mm on the lower surface and ending at a diameter of 127.2mm. The spiral angle is 287.3°, the groove width is 2mm, and the groove depth is 1mm (in this embodiment, the groove depth is 1 / 4 of the graphite substrate thickness). A schematic diagram of the resulting non-working surface is shown below. Figure 6 As shown.
[0067] Example 3 Semi-coated silicon carbide graphite parts were obtained using the preparation method provided in Example 1, with the following differences: During the preparation of the composite gradient material layer, four gradient segments of composite gradient material layer powder are prepared (n=4 in this embodiment). Based on the total mass of the composite gradient material layer, the specific mass content of the slurry is as follows: Graphite matrix side: Slurry 1, silicon carbide content 75%, aluminum oxide content 20%, silicone resin 5%; Intermediate layer 1: Slurry 2, with silicon carbide accounting for 80% by mass, aluminum oxide accounting for 15% by mass, and phenolic resin accounting for 5% by mass; Intermediate layer 2: Slurry 3, with silicon carbide accounting for 85% by mass, aluminum oxide accounting for 10% by mass, and silicone resin accounting for 5% by mass; Silicon carbide layer side: slurry 4, silicon carbide mass content is 90%, aluminum oxide mass content is 5%, and silicone resin is 5%.
[0068] Example 4 Semi-coated silicon carbide graphite parts were obtained using the preparation method provided in Example 1, with the following differences: During the preparation of the silicon carbide layer, the gradient cooling process is as follows: the temperature is reduced from the deposition temperature to 800℃ at a rate of 4℃ / min and held for 2 hours; the temperature is reduced to 300℃ at a rate of 2.5℃ / min and held for 8 hours; and the temperature is reduced to room temperature at a rate of 6℃ / min.
[0069] Example 5 Semi-coated silicon carbide graphite parts were obtained using the preparation method provided in Example 1, with the following differences: During the matrix pretreatment process, the stress relief groove has a width of 2.2 mm and a depth of 1.5 mm (in this embodiment, the groove depth is 0.375 times the thickness of the graphite matrix).
[0070] Example 6 Semi-coated silicon carbide graphite parts were obtained using the preparation method provided in Example 1, with the following differences: In the preparation process of the composite gradient material layer, three gradient segments of composite gradient material layer powder are prepared. Based on the total mass of the composite gradient material layer, the specific mass content of the slurry is as follows: Graphite matrix side: Slurry 1, silicon carbide content is 8% by mass, graphite content is 86% by mass, and phenolic resin content is 6%; Intermediate layer 1: Slurry 2, with silicon carbide accounting for 50% by mass, graphite accounting for 44% by mass, and phenolic resin accounting for 6% by mass; Silicon carbide layer side: slurry 3, silicon carbide mass content is 92%, graphite mass content is 2%, phenolic resin is 6%.
[0071] Example 7 Semi-coated silicon carbide graphite parts were obtained using the preparation method provided in Example 1, with the following differences: During the preparation of the silicon carbide layer, the gradient cooling process is as follows: the temperature is reduced from the deposition temperature to 800℃ at a rate of 4℃ / min and held for 2 hours; the temperature is reduced to 445℃ at a rate of 2.5℃ / min and held for 4 hours; and the temperature is reduced to room temperature at a rate of 6℃ / min.
[0072] Comparative Example 1 Semi-coated silicon carbide graphite parts were obtained using the preparation method provided in Example 1, with the following differences: No stress relief groove is provided.
[0073] Comparative Example 2 Semi-coated silicon carbide graphite parts were obtained using the preparation method provided in Example 1, with the following differences: Only one composite material layer is provided between the graphite matrix and the silicon carbide layer. The mass content of the slurry is as follows, based on the total mass of the composite material layer: silicon carbide accounts for 50%, graphite accounts for 44%, and phenolic resin accounts for 6%.
[0074] Comparative Example 3 Semi-coated silicon carbide graphite parts were obtained using the preparation method provided in Example 1, with the following differences: During the preparation of the silicon carbide layer, after the silicon carbide layer is deposited, the temperature is cooled from the deposition temperature to room temperature at a rate of 4℃ / min.
[0075] Test case 1. Flatness test: The semi-coated silicon carbide graphite parts obtained in the examples and comparative examples, as well as the semi-coated silicon carbide graphite parts of the prior art, were placed in a high and low temperature cycling test chamber. The cycling range was 50℃ to 1000℃, with a heating rate of 10℃ / min and a cooling rate of 5℃ / min. Each cycle was held at the same temperature for 30 minutes, and this process was repeated 50 times. After the cycles were completed, a laser flatness measuring instrument was used to scan the entire working surface of the graphite parts under dust-free conditions, a room temperature of 25℃, and a humidity of 40% to 60%. The scanning point spacing was 0.5mm, and the height difference between the highest and lowest points of the working surface was recorded as the flatness.
[0076] The results of the initial flatness test of the examples, comparative examples, and existing semi-coated silicon carbide graphite parts, as well as the flatness test results after 50 high and low temperature cycles, are shown in Table 1 below.
[0077] Table 1 Flatness Test Data As shown in Table 1, the initial flatness of the semi-coated silicon carbide graphite part prepared using the method of this invention is ≤0.02mm, and the flatness after 50 consecutive high and low temperature cycles is ≤0.025mm. This invention, by setting a composite gradient material layer and a stress relief groove, combined with a constant temperature stress relief process, significantly reduces the internal stress level of the final product. The resulting semi-coated silicon carbide graphite part effectively ensures the overall dimensional stability and flatness accuracy of the workpiece.
[0078] 2. Coating integrity test: The semi-coated silicon carbide graphite parts obtained in the examples and comparative examples, as well as the semi-coated silicon carbide graphite parts of the prior art, were jointly inspected using an ultrasonic flaw detector combined with a metallographic microscope. The specific steps are as follows: (1) Place the workpiece to be tested in deionized water and use a 20kHz~40kHz ultrasonic probe to perform a full-area scan to observe whether there are any coating peeling, delamination, or cracking signals. (2) Cut the workpiece radially, and after inlaying, grinding and polishing, observe the coating interface and cross section with a metallographic microscope of 100x to 500x. Record the proportion of the effective area of the coating without cracks, peeling and pinholes to the total coating area, which is the coating integrity.
[0079] The coating integrity test results of the examples, comparative examples, and existing semi-coated silicon carbide graphite parts are shown in Table 2 below.
[0080] Table 2 Coating integrity test data As shown in Table 2, the coating integrity of the semi-coated silicon carbide graphite parts prepared using the scheme of this invention is ≥98%. This invention achieves a continuous and smooth transition in the coefficient of thermal expansion from the graphite substrate to the silicon carbide coating by setting a composite gradient material layer on the working surface. This significantly reduces the concentrated shear stress generated at the interface between the coating and the substrate due to abrupt changes in material properties, preventing cracking or peeling of the coating due to excessive interface stress. Simultaneously, the stress relief grooves pre-set on the non-working surface provide a stress relief channel for residual stress inevitably transmitted to the substrate during coating deposition and subsequent thermal cycling. This allows the substrate to dissipate energy through small, directional deformations, rather than completely transferring the deformation stress to the rigid coating, preventing brittle fracture of the coating due to excessive substrate warping strain.
[0081] Furthermore, in the semi-coated silicon carbide graphite part manufacturing process of the present invention, a gradient cooling process including a specific heat preservation stage further eliminates the accumulation of internal stress during the manufacturing process. The synergistic effect of the composite gradient material layer, the stress relief groove, and the manufacturing process ensures that the silicon carbide coating maintains its integrity and the structural strength of the product even after undergoing high-temperature preparation and harsh service conditions.
[0082] The embodiments described in this invention are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without inventive effort are within the scope of protection of this invention.
Claims
1. A semi-coated silicon carbide graphite part, characterized in that, The invention includes a graphite matrix, the surface of which is composed of a working surface and a non-working surface. The working surface is sequentially provided with a composite gradient material layer and a silicon carbide layer, the composite gradient material layer completely covering the working surface. The non-working surface is provided with a stress relief groove. The stress relief groove includes at least one of annular groove, radial groove, and spiral groove. The composite gradient material layer contains at least one of silicon carbide-graphite composite material, silicon carbide-alumina composite material, and silicon carbide-yttrium oxide composite material. The mass content of silicon carbide in the composite gradient material layer increases linearly from the graphite matrix side to the silicon carbide layer side.
2. The semi-coated silicon carbide graphite part according to claim 1, characterized in that, The stress relief groove has a groove width of 0.5mm to 2mm and a groove depth of 1 / 5 to 1 / 3 of the thickness of the graphite matrix, and the groove depth is not less than 1mm. And / or, the thickness of the composite gradient material layer is 0.05 mm to 0.15 mm; And / or, the thickness of the silicon carbide layer is 0.1 mm to 0.5 mm.
3. The semi-coated silicon carbide graphite part according to claim 1, characterized in that, When the stress relief groove is a combination of the annular groove and the radial groove, the stress relief groove includes at least one annular groove and several radial grooves. The annular groove and the radial grooves are concentrically arranged with the rotation center of the graphite matrix. The radial grooves radiate outward from the rotation center and communicate with the annular grooves. The number of annular grooves is 1 to 3, and the number of radial grooves is 4 to 8. And / or, when the stress relief groove is a spiral groove, the spiral groove extends outward from the rotation center of the graphite matrix.
4. The semi-coated silicon carbide graphite part according to claim 1, characterized in that, The silicon carbide-graphite composite material comprises silicon carbide, graphite, and a binder; based on the total mass of the composite gradient material layer, the silicon carbide mass content on the graphite matrix side is 10%~30%, and the graphite mass content is 62%~87%; the silicon carbide mass content on the silicon carbide layer side is 80%~90%, and the graphite mass content is 2%~17%; the binder mass content in the composite gradient material layer is 3%~8%, and the binder includes at least one of phenolic resin, furan resin, and epoxy resin; The silicon carbide-alumina composite material comprises silicon carbide, alumina, and a binder. Based on the total mass of the composite gradient material layer, the alumina content on the graphite matrix side is 10%~20%, and the silicon carbide content is 72%~87% by mass; the alumina content on the silicon carbide layer side is 0%~5%, and the silicon carbide content is 87%~97% by mass; the binder in the composite gradient material layer has a mass percentage of 3%~8%, and the binder includes at least one of phenolic resin, silicone resin, and borosilicate resin.
5. A method for preparing a semi-coated silicon carbide graphite part according to any one of claims 1-4, characterized in that, Includes the following steps: (1) Matrix pretreatment: The non-working surface of the graphite matrix is finely machined, and then stress relief grooves are machined on the non-working surface of the graphite matrix; (2) Preparation of composite gradient material layer: The components of the composite gradient material layer are mixed according to the mass fraction of each component to prepare a slurry. The slurry is sprayed onto the working surface of the graphite substrate, dried and sintered to obtain a graphite part with a composite gradient material layer. (3) Preparation of silicon carbide layer: A silicon carbide layer is deposited on the surface of the composite gradient material layer of the graphite part obtained in step (2), and then gradient cooling is performed to obtain a graphite part with silicon carbide coating. (4) Finishing treatment: Polish the surface of the silicon carbide coating of the graphite part obtained in step (3) to obtain a semi-coated silicon carbide graphite part.
6. The method for preparing a semi-coated silicon carbide graphite part according to claim 5, characterized in that, After the graphite substrate undergoes the finishing process, the initial flatness of the non-working surface is ≤0.01mm.
7. The method for preparing a semi-coated silicon carbide graphite part according to claim 5, characterized in that, In the process of preparing the composite gradient material layer, the slurry preparation method of the composite gradient material layer is as follows: the components of the composite gradient material layer are prepared according to the linear gradient increase ratio of silicon carbide mass content, and the composite gradient material layer powder of n gradient segments is prepared respectively, and mixed to obtain n parts of slurry, wherein the mass content of silicon carbide in the n parts of slurry increases linearly; wherein n takes a positive integer and n≥3; The n portions of slurry are sequentially sprayed onto the working surface of the graphite substrate in a linear gradient increasing order. After spraying, the slurry is dried at 120℃~180℃ for 2h~4h. The sintering process specifically involves heating to 800℃~1000℃ at a rate of 5℃ / min~10℃ / min under inert gas protection, and holding at that temperature for 3h~5h.
8. The method for preparing a semi-coated silicon carbide graphite part according to claim 5, characterized in that, The process of depositing the silicon carbide layer adopts chemical vapor deposition or physical vapor deposition, and the deposition temperature is 1100℃~1300℃.
9. The method for preparing a semi-coated silicon carbide graphite part according to claim 5, characterized in that, The gradient cooling process is specifically as follows: S1. Cool from the deposition temperature to 750℃~850℃ at a rate of 3℃ / min~5℃ / min, and hold for 1.5h~2.5h; S2. Cool to 450℃~550℃ at a rate of 2℃ / min~3℃ / min, and hold for 3h~5h. Alternatively, the temperature can be lowered to 250℃~350℃ at a rate of 2℃ / min~3℃ / min and held for 7h~9h; S3. Cool to room temperature at a rate of 5℃ / min to 8℃ / min.
10. The method for preparing a semi-coated silicon carbide graphite part according to claim 5, characterized in that, The flatness of the silicon carbide coating surface of the semi-coated silicon carbide graphite part after polishing is ≤0.02mm.