Forming die and preparation method of SiC / SiC composite material pin

Abstract

The present invention relates to a forming die and preparation method for SiC / SiC composite material pins. The forming die comprises a bottom die, a top die, and a positioning reference die. The bottom die, the top die, and the positioning reference die are each provided with an impregnation flow channel, and the top die and the positioning reference die are detachably mounted on one side of the bottom die. The forming die for SiC / SiC composite material pins of the present invention secures the relative positional relationship between the pin, the bottom die, and the positioning reference die while enabling impregnation by removing the top die without affecting impregnation efficiency. This facilitates seamless reclosure of the top die during cracking, avoiding the poor top die closure effect of conventional solutions, minimizing surface deformation of the pin blank during the later densification process, and ensuring the roundness and straightness of the pin blank. This facilitates the determination and unification of the pin blank's reference during processing, enables batch processing of multiple pins, reduces processing difficulty, saves labor time and costs, and improves the yield rate.

Description

Technical Field

[0001] The present invention relates to the technical field of composite material processing, and in particular to a forming die and a preparation method of a SiC / SiC composite material pin. Background Art

[0002] Compared to traditional high-temperature alloys, SiC / SiC composites have a density of only 1 / 3 to 1 / 4 that of high-temperature alloys. They possess excellent properties such as high strength, high modulus, and high-temperature oxidation resistance, making them internationally recognized as ideal materials for hot-end components in the aerospace industry. Pinning is convenient and simple, enabling single-sided connections of complex SiC / SiC composite structural parts. Furthermore, both the pins and connectors are SiC / SiC composites, eliminating the thermal mismatch between the metal and SiC / SiC composites due to mismatched thermal expansion coefficients. This material holds broad application prospects in the assembly and connection of SiC / SiC composite structural parts.

[0003] SiC / SiC composite pins prepared using traditional methods have the following drawbacks: In the traditional SiC / SiC composite pin preparation process, after multiple impregnation and cracking cycles and the initial pin body shape is achieved, the mold must be de-impregnated and then placed back into the mold to maintain its shape during high-temperature cracking. However, since the cylindrical pin body lacks a distinct surface for positioning, the pin body's position can easily deviate after demolding and re-molding. This reduces the mold's constraint on the pin body during high-temperature cracking, causing surface deformation, impacting the roundness and straightness of the SiC / SiC composite pin and easily causing deformation. The SiC / SiC composite pin's machining dimensions are difficult to control, resulting in large machining errors. Currently, there is no unified and clear machining benchmark for SiC / SiC composite pins, which increases the difficulty of machining, increases labor time and costs, and increases scrap rates.

[0004] Therefore, the present invention provides a forming die and a preparation method for a SiC / SiC composite material pin. Summary of the Invention

[0005] (1) Technical problems to be solved

[0006] The embodiments of the present invention provide a forming die and a preparation method for a SiC / SiC composite material pin, which solve the technical problems of difficult control of the processing size of the SiC / SiC composite material pin and large processing error.

[0007] (2) Technical solution

[0008] In order to solve the above technical problems, the present invention provides a first aspect of a SiC / SiC composite material pin forming die, comprising a bottom die, a top die and a positioning reference die;

[0009] The bottom mold, the top mold and the positioning reference mold are respectively provided with an impregnation flow channel, and the top mold and the positioning reference mold can be detachably mounted on one side of the bottom mold.

[0010] Optionally, connecting holes are respectively provided on the bottom mold, the top mold and the positioning reference mold, the connecting holes on the top mold and the connecting holes on the bottom mold are respectively connected by a first connecting member, and the connecting holes on the positioning reference mold and the connecting holes on the bottom mold are respectively connected by a second connecting member.

[0011] In a second aspect, the present invention further provides a method for preparing a SiC / SiC composite material pin, which is applied to a molding die for the above-mentioned SiC / SiC composite material pin, comprising:

[0012] Fixing the pin fiber preform in a forming mold for SiC / SiC composite pins, wherein the pin fiber preform is located between a bottom mold and a top mold, and between the bottom mold and the positioning reference mold;

[0013] forming an interface layer on the surface of the pin fiber preform;

[0014] Performing a preliminary densification treatment on the pin fiber preform, and removing the top mold to obtain a porous pin blank;

[0015] Closing the top mold on the bottom mold, further densifying the pin blank to obtain a dense pin blank;

[0016] The dense pin blank is processed into a pin.

[0017] Optionally, the interface layer is at least one of a PyC interface layer, a BN interface layer, a PyC / SiC composite interface layer, and a BN / SiC composite interface layer.

[0018] Optionally, the pin fiber preform is a two-dimensional braided structure.

[0019] Optionally, the preliminary densification treatment is performed on the pin fiber preform, and after removing the top mold, a porous pin blank is obtained, comprising:

[0020] vacuum impregnation the pin fiber preform with a ceramic precursor solution;

[0021] Heating the impregnated pin fiber preform to a temperature of a ceramic transition point of the precursor to perform high-temperature cracking;

[0022] The top mold is removed to obtain a porous pin blank.

[0023] Optionally, the pin fiber preform is vacuum impregnated with a ceramic precursor solution, the vacuum impregnation time is 24 hours to 48 hours, and the high-temperature pyrolysis time is 0.5 hours to 2 hours.

[0024] Optionally, the ceramic precursor solution is a polycarbosilane solution or liquid polycarbosilane.

[0025] Optionally, closing the top mold on the bottom mold and further densifying the pin blank to obtain a dense pin blank comprises:

[0026] vacuum impregnation the pin blank with a ceramic precursor solution;

[0027] closing the top mold on the bottom mold;

[0028] subjecting the pin blank with the forming die to high-temperature cracking;

[0029] The pin blank is weighed, and when the mass increase rate of the pin blank before and after high-temperature cracking is less than 1%, the dense pin blank is obtained.

[0030] Optionally, in the vacuum impregnation treatment of the pin blank with the ceramic precursor solution, the vacuum impregnation treatment time is 12 hours to 24 hours, and the high-temperature cracking time is 0.5 hours to 2 hours.

[0031] (3) Beneficial effects

[0032] In summary, when preparing SiC / SiC composite pins, the prepared pin fiber preform and standard specimen are placed in a bottom mold, and the positioning reference mold and top mold are respectively installed on the bottom mold. The positioning reference mold, top mold and bottom mold are fixedly connected using bolts. An interface layer is then formed on the surface of the pin fiber preform, and then the pin fiber preform is subjected to a preliminary densification treatment to obtain a pin blank. The pin blank is then further densified to obtain a dense pin blank, and finally the dense pin blank is processed into a pin. During the preliminary densification treatment, the top mold is removed, but at this time the bottom mold and the reference positioning mold can still limit and fix the pin fiber preform, so that the pin fiber preform will not be offset, each pin fiber preform is not easily deformed, and the roundness and straightness of the pin fiber preform can be basically consistent. During the further densification treatment, the top mold is closed on the bottom mold, and the pin obtained by the final processing has a small error and good consistency.

[0033] The molding die for the SiC / SiC composite material pin of the present invention fixes the relative positional relationship between the pin, the bottom mold, and the positioning reference mold while achieving impregnation without affecting the impregnation efficiency. This facilitates seamless closure of the top mold during cracking, avoids the problem of poor top mold closure in traditional solutions, minimizes surface deformation of the pin blank during the subsequent densification process, and ensures the roundness and straightness of the pin blank.

[0034] In addition, the molding die and positioning reference die of the SiC / SiC composite material pin of the present invention ensure that the position of the pin remains unchanged during the process, and at the same time assist in determining the reference during the processing, which is beneficial to the reference determination and unification of the pin during the processing process, and can realize batch processing of multiple pins, reduce processing difficulty, save labor time and cost, and improve the qualified product rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0036] Figure 1 1 is a schematic structural diagram of a molding die for a SiC / SiC composite material pin according to an embodiment of the present invention;

[0037] Figure 2 This is a diagram showing the connection relationship between the bottom mold, the pin fiber preform, and the standard test piece in one embodiment of the present invention;

[0038] Figure 3 This is a diagram showing the connection relationship between a forming die and a pin fiber preform of a SiC / SiC composite pin according to one embodiment of the present invention;

[0039] Figure 4 This is a diagram showing the connection relationship between the bottom mold, the positioning reference mold, the pin fiber preform and the standard test piece in one embodiment of the present invention.

[0040] In the figure: 1- bottom mold; 2- positioning reference mold; 3- top mold; 4- connection hole; 5- impregnation flow channel; 6- pin fiber preform; 7- standard test piece. DETAILED DESCRIPTION

[0041] The following detailed description of the embodiments of the present invention is provided in conjunction with the accompanying drawings and examples. The detailed description of the following embodiments and the accompanying drawings are intended to illustrate the principles of the present invention and are not intended to limit the scope of the present invention. That is, the present invention is not limited to the described embodiments and covers any modifications, replacements, and improvements to the parts, components, and connection methods without departing from the spirit of the present invention.

[0042] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments in this application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0043] It should be noted that the various embodiments in this specification are described in a progressive manner. References to the same or similar parts between the various embodiments are sufficient. Each embodiment focuses on the differences from the other embodiments. The present invention is not limited to the specific steps and structures described above and shown in the figures. Furthermore, for the sake of brevity, detailed descriptions of known methods and technologies are omitted here.

[0044] Please refer to Figures 1 to 4 A forming mold for a SiC / SiC composite material pin includes a bottom mold 1, a top mold 3 and a positioning reference mold 2; the bottom mold 1, the top mold 3 and the positioning reference mold 2 are respectively provided with an impregnation flow channel 5, and the top mold 3 and the positioning reference mold 2 can be detachably installed on one side of the bottom mold 1.

[0045] When preparing SiC / SiC composite material pins, the prepared pin fiber preform 6 and standard test piece 7 are placed in the bottom mold 1, and the positioning reference mold 2 and the top mold 3 are respectively installed on the bottom mold 1, and the positioning reference mold 2, the top mold 3 and the bottom mold 1 are fixedly connected using bolts. Then an interface layer is formed on the surface of the pin fiber preform 6, and then the pin fiber preform 6 is subjected to a preliminary densification process to obtain a pin blank. The pin blank is further densified to obtain a dense pin blank, and finally the dense pin blank is processed into a pin. During the preliminary densification process, the top mold 3 is removed, but at this time the bottom mold 1 and the reference positioning mold can still produce a limiting and fixing effect on the pin fiber preform 6, so that the pin fiber preform 6 will not be offset, and each pin fiber preform 6 is not easily deformed, and the roundness and straightness of the pin fiber preform 6 can be basically consistent. During further densification treatment, the top die 3 is closed on the bottom die 1, and the pins finally obtained by processing have small errors and good consistency.

[0046] The forming mold of the SiC / SiC composite material pin of this embodiment can fix the relative position relationship of the pin, the bottom mold 1 and the positioning reference mold 2 while realizing the removal of the top mold 3 for impregnation without affecting the impregnation efficiency, which is conducive to the seamless closure of the top mold 3 again during cracking, avoiding the problem of poor closing effect of the top mold 3 in the traditional solution, minimizing the surface deformation of the pin blank during the later densification process, and ensuring the roundness and straightness of the pin blank.

[0047] In addition, the forming mold of the SiC / SiC composite material pin of this embodiment and the positioning reference mold 2 ensure that the position of the pin remains unchanged during the process, and at the same time assist in determining the reference during the processing, which is beneficial to the reference determination and unification of the pin during the processing process, and can realize batch processing of multiple pins, reduce processing difficulty, save labor time and cost, and improve the qualified product rate.

[0048] Among them, the top mold 3 is a male mold, the bottom mold 1 and the positioning reference mold 2 are female molds, and the SiC matrix precursor is injected through the impregnation flow channel 5.

[0049] In one embodiment, the bottom mold 1, top mold 3, and positioning reference mold 2 are each provided with a connecting hole 4. The connecting holes 4 on the top mold 3 and the bottom mold 1 are each connected by a first connecting member, and the connecting holes 4 on the positioning reference mold 2 and the bottom mold 1 are each connected by a second connecting member. The top mold 3, bottom mold 1, and positioning reference mold 2 are connected via the connecting holes 4, and the connecting holes 4 are connected to each other via pins, bolts, or other structures. Specifically, the first and second connecting members are each pins or bolts, which facilitates assembly and disassembly and maintains a simple structure.

[0050] This embodiment also provides a method for preparing a SiC / SiC composite material pin, which is applied to the molding die of the SiC / SiC composite material pin, comprising:

[0051] Fixing the pin fiber preform 6 in the SiC / SiC composite material pin forming mold, the pin fiber preform 6 is located between the bottom mold 1 and the top mold 3, and the pin fiber preform 6 is located between the bottom mold 1 and the positioning reference mold 2;

[0052] forming an interface layer on the surface of the pin fiber preform 6;

[0053] The pin fiber preform 6 is subjected to a preliminary densification treatment, and after removing the top mold 3, a porous pin blank is obtained;

[0054] Closing the top mold 3 on the bottom mold 1, further densifying the pin blank to obtain a dense pin blank;

[0055] The dense pin blank is processed into a pin.

[0056] The method for preparing the SiC / SiC composite material pin of this embodiment also has the advantages of the above-mentioned forming mold of the SiC / SiC composite material pin, which will not be described in detail here.

[0057] In one embodiment, the interface layer is at least one of a PyC interface layer, a BN interface layer, a PyC / SiC composite interface layer, and a BN / SiC composite interface layer. Specifically, forming the interface layer on the surface of the pin fiber preform 6 includes placing the pin fiber preform 6 with a forming mold in an interface layer apparatus to perform chemical vapor deposition to form a PyC / SiC composite interface layer, wherein the PyC has a thickness of ∼200 nm and the SiC has a thickness of ∼200 nm.

[0058] In one embodiment, the pin fiber preform 6 is a two-dimensional braided structure.

[0059] In one embodiment, the pin fiber preform 6 is subjected to a preliminary densification treatment, and after removing the top mold 3, a porous pin blank is obtained, comprising:

[0060] The pin fiber preform 6 is vacuum impregnated with a ceramic precursor solution;

[0061] Heating the impregnated pin fiber preform 6 to the precursor ceramic transition point temperature for high-temperature cracking;

[0062] The top mold 3 is removed to obtain a porous pin blank.

[0063] Specifically, the pin fiber preform 6 and the standard specimen 7 with the mold prepared for the interface layer are placed in a vacuum impregnation device. The vacuum impregnation device is evacuated with a vacuum pump. When the pressure in the vacuum impregnation device is less than 100Pa, the ceramic precursor solution is introduced into the vacuum impregnation device through a stainless steel pipe, and finally the pin fiber preform 6 with the interface layer and the standard specimen 7 are completely submerged in the ceramic precursor solution. After the impregnation treatment for 48 hours, the pin fiber preform 6 and the standard specimen 7 with the forming mold are placed in a high-temperature cracking furnace for high-temperature cracking. The high-temperature cracking environment is either a vacuum environment or an atmospheric environment. The temperature is raised to the ceramic transition point of the precursor and then kept warm for 0.5 hours. After repeating the cycle 4 times, the top mold 3 is removed to obtain a porous pin blank with a bottom mold 1 and a positioning reference mold 2.

[0064] In one embodiment, the pin fiber preform 6 is vacuum impregnated with a ceramic precursor solution, the vacuum impregnation time is 24 hours to 48 hours, and the high temperature cracking time is 0.5 hours to 2 hours.

[0065] In one embodiment, the ceramic precursor solution is a polycarbosilane solution or liquid polycarbosilane.

[0066] In one embodiment, the top mold 3 is closed on the bottom mold 1, and the pin blank is further densified to obtain a dense pin blank, including:

[0067] vacuum impregnation the pin blank with a ceramic precursor solution;

[0068] Closing the top mold 3 on the bottom mold 1;

[0069] subjecting the pin blank with the forming die to high-temperature cracking;

[0070] The pin blank is weighed, and when the mass increase rate of the pin blank before and after high-temperature cracking is less than 1%, the dense pin blank is obtained.

[0071] Specifically, the standard specimen 7 and the pin fiber preform 6 are made of the same material. The standard specimen 7 is weighed, and the weight change of the standard specimen 7 reflects the weight change of the pin blank.

[0072] Specifically, a pin blank with a bottom mold 1 and a positioning reference mold 2 is placed in a vacuum impregnation device, and the vacuum impregnation device is evacuated with a vacuum pump. When the pressure in the inner cavity of the vacuum impregnation device is less than 100 Pa, a ceramic precursor solution is introduced into the inner cavity of the vacuum impregnation device through a stainless steel pipe, and finally the porous pin blank is submerged in the ceramic precursor solution and maintained for 12 hours. Then the top mold 3 is closed on the bottom mold 1, and then the pin blank with the forming mold is placed in a high-temperature cracking furnace for cracking. The high-temperature cracking environment is one of a vacuum environment or an atmospheric environment. After heating to the ceramic transition point temperature of the precursor, it is kept warm for 0.5 hours, demolded and weighed, and the impregnation-molding-high-temperature cracking-demolding process of this step is repeated. When the weight gain rate of the pin blank after impregnation and cracking is less than 1% of the mass before impregnation, the matrix densification process of the pin blank is completed to obtain a densified pin blank.

[0073] In one embodiment, the vacuum impregnation treatment of the pin blank with the ceramic precursor solution is performed for 12 hours to 24 hours, and the high-temperature pyrolysis time is 0.5 hours to 2 hours.

[0074] In one embodiment, processing the dense pin blank into a pin includes: processing the dense pin blank according to the drawing requirements to obtain a pin of net size, polishing it with 1200-grit water sandpaper, and then cleaning the polished area with anhydrous ethanol and drying it to complete the preparation of the pin.

[0075] The above are merely embodiments of the present application and are not intended to limit the present application. Various modifications and variations are possible for those skilled in the art without departing from the scope of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application should be included within the scope of the claims of the present application.

Claims

1. A method for preparing a SiC / SiC composite material pin, characterized in that: The molding die for SiC / SiC composite material pins includes a bottom die, a top die and a positioning reference die; The bottom mold, the top mold and the positioning reference mold are respectively provided with an impregnation flow channel, and the top mold and the positioning reference mold are detachably mounted on one side of the bottom mold; The preparation method of SiC / SiC composite material pins comprises the following steps: Fixing the pin fiber preform in a forming mold for SiC / SiC composite pins, wherein the pin fiber preform is located between a bottom mold and a top mold, and between the bottom mold and the positioning reference mold; forming an interface layer on the surface of the pin fiber preform; vacuum impregnation the pin fiber preform with a ceramic precursor solution; Heating the impregnated pin fiber preform to a temperature of a ceramic transition point of the precursor to perform high-temperature cracking; removing the top mold to obtain a porous pin blank; vacuum impregnation the pin blank with a ceramic precursor solution; closing the top mold on the bottom mold; subjecting the pin blank with the forming die to high-temperature cracking; Weighing the pin blank, and when the mass increase rate of the pin blank before and after high-temperature pyrolysis is less than 1%, a dense pin blank is obtained; The dense pin blank is processed into a pin.

2. The preparation method according to claim 1, characterized in that The bottom mold, the top mold and the positioning reference mold are respectively provided with connecting holes, the connecting holes on the top mold and the connecting holes on the bottom mold are respectively connected by a first connecting piece, and the connecting holes on the positioning reference mold and the connecting holes on the bottom mold are respectively connected by a second connecting piece.

3. The preparation method according to claim 1, characterized in that The interface layer is at least one of a PyC interface layer, a BN interface layer, a PyC / SiC composite interface layer, and a BN / SiC composite interface layer.

4. The preparation method according to claim 1, characterized in that The pin fiber preform is a two-dimensional braided structure.

5. The preparation method according to claim 1, characterized in that The pin fiber preform is vacuum impregnated with a ceramic precursor solution, wherein the vacuum impregnation treatment lasts for 24 hours to 48 hours, and the high-temperature cracking time is 0.5 hours to 2 hours.

6. The preparation method according to claim 1, characterized in that The ceramic precursor solution is a polycarbosilane solution or liquid polycarbosilane.

7. The preparation method according to claim 1, characterized in that In the vacuum impregnation treatment of the pin blank with the ceramic precursor solution, the vacuum impregnation treatment time is 12 hours to 24 hours, and the high-temperature cracking time is 0.5 hours to 2 hours.

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