Method of forming a narrow or closed cavity ceramic matrix composite part

Abstract

The application provides a forming method of a narrow-cavity or closed-cavity ceramic matrix composite part, and solves the problems that the solid structure graphite mold used in the forming process of the narrow-cavity ceramic matrix composite part affects the forming quality of the inner surface of the part, causes defects such as delamination and dust adhesion, and prolongs the preparation cycle of the part. The method comprises the following steps: step 1.1, manufacturing a forming tool, a graphite inner mold, a first outer mold and a second outer mold; step 1.2, winding and cutting multiple layers of carbon cloth on the graphite inner mold to obtain a C / SiC inner mold preform; step 1.3, combining the C / SiC inner mold preform with the punched forming tool to perform deposition; step 1.4, punching the first seam on the deposited C / SiC inner mold preform; step 1.5, obtaining a formed C / SiC inner mold; step 2, placing the C / SiC inner mold on the laminated carbon cloth on the first outer mold, and turning up the edges to obtain a part preform; step 3, combining the part preform, the first outer mold and the second outer mold; step 4, performing deposition on the combined part preform; and step 5, obtaining a formed part.

Description

Technical Field

[0001] This invention relates to a molding method for ceramic matrix composite parts, specifically to a molding method for narrow-cavity or closed-cavity ceramic matrix composite parts. Background Technology

[0002] In the fabrication of fiber-reinforced ceramic matrix composite (CMC) parts, molds are typically required to support the parts and achieve the desired shape. When using chemical vapor deposition (CVD) to fabricate CMC parts, the high fabrication temperature (approximately 900-1100℃) necessitates the use of high-temperature resistant graphite materials as the molding die. However, when fabricating narrow-cavity CMC parts, due to their small internal dimensions, graphite molds are usually designed as solid structures. This type of graphite mold can negatively impact the molding quality of the internal surfaces of the narrow-cavity CMC parts, leading to quality issues such as delamination and dust accumulation, and also prolonging the fabrication cycle. Summary of the Invention

[0003] The purpose of this invention is to solve the technical problem that the solid graphite mold used in the molding process of existing narrow-cavity or closed-cavity ceramic matrix composite parts will affect the molding quality of the inner surface of the parts, easily causing quality problems such as delamination and dust accumulation, and will prolong the part manufacturing cycle. The invention provides a molding method for narrow-cavity or closed-cavity ceramic matrix composite parts.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] A method for molding narrow-cavity or closed-cavity ceramic matrix composite parts, characterized by the following steps:

[0006] Step 1: Fabrication of C / SiC internal mold

[0007] Step 1.1: Fabricate a molding fixture and set ventilation holes on the molding fixture. The inner surface of the molding fixture is consistent with the outer surface of the C / SiC inner mold to be molded. Fabricate a graphite inner mold. The outer surface of the graphite inner mold is consistent with the shape of the narrow cavity or closed cavity of the part to be molded. Fabricate a first outer mold and a second outer mold. The inner surfaces of the first outer mold and the second outer mold are consistent with the outer surfaces of the part to be molded.

[0008] Step 1.2: Wrap multiple layers of carbon cloth around the two end faces and two opposite sides of the graphite inner mold without sewing. Trim the edges of the carbon cloth to be flush with the outer surface of the graphite inner mold to obtain a C / SiC inner mold preform with a graphite inner mold.

[0009] Step 1.3: After the C / SiC inner mold preform with graphite inner mold is assembled with the punched molding tool, carbon interface layer deposition and silicon carbide substrate deposition are performed in sequence.

[0010] Step 1.4: Remove the molding tooling, place the deposited C / SiC inner mold preform on the first outer mold, and drill the first slit hole;

[0011] Step 1.5: Remove the first outer mold and take out the graphite inner mold to obtain the formed C / SiC inner mold;

[0012] Step 2: Stack the carbon cloth required for the part to be formed on the first outer mold, place the obtained C / SiC inner mold on the stacked carbon cloth, and make the two ends of the C / SiC inner mold flush with the two ends of the first outer mold respectively. After flanging, the part preform is obtained; the inner surface of the part preform is consistent with the shape of the narrow cavity or closed cavity of the part to be formed.

[0013] Step 3: Sew the obtained prefabricated part through the first outer mold and then assemble it with the second outer mold;

[0014] Step 4: The preform of the molded part is subjected to carbon interface layer deposition and silicon carbide substrate deposition treatment in sequence using CVI process.

[0015] Step 5: Remove the first and second outer molds, machine the preform of the part after deposition treatment, and then perform silicon carbide substrate deposition treatment to obtain the final shaped part.

[0016] Furthermore, in step 1.1, the forming fixture is composed of N sub-forming fixtures; where N is an integer greater than or equal to 2;

[0017] Step 1.2 specifically involves the following steps: The graphite inner mold is composed of N sub-graphite inner molds. Multiple layers of carbon cloth are wound around the two end faces and two opposite sides of each of the N sub-graphite inner molds without sewing. The edges of the carbon cloth are trimmed to be flush with the outer surface of the sub-graphite inner molds, resulting in N sub-C / SiC inner mold preforms with sub-graphite inner molds. The inner surfaces of the N sub-C / SiC inner mold preforms are consistent with the outer surfaces of the N sub-graphite inner molds. The outer surfaces of the N sub-C / SiC inner mold preforms are consistent with the inner surfaces of the N sub-forming fixtures in Step 1.1.

[0018] In step 1.3, the N sub-C / SiC inner mold preforms with sub-graphite inner molds are respectively joined with the N sub-forming fixtures after drilling.

[0019] Step 1.4 specifically involves removing the sub-forming tooling, splicing the N sub-C / SiC inner mold preforms after deposition treatment onto the first outer mold, and drilling the first sewing hole;

[0020] Step 1.5 specifically involves removing the first outer mold, taking out each sub-graphite inner mold, and obtaining N formed sub-C / SiC inner molds;

[0021] In step 2, the N sub-C / SiC inner molds obtained in step 1.5 are spliced ​​and placed on the stacked carbon cloth.

[0022] Further, in step 2.1, based on the thickness and dimensions of the part to be formed, calculate the number and size of the carbon cloth layers required for the part to be formed, and stack them on the first outer mold.

[0023] Step 2.2: Place the N sub-C / SiC inner molds obtained in Step 1.5 onto the carbon cloth after being stacked in Step 2.1, with both ends flush with the two ends of the first outer mold;

[0024] Step 2.3: Place graphite shaping fixtures at the splicing positions of the N sub-C / SiC inner molds and at the center of each sub-C / SiC inner mold, then perform flanging to stagger the carbon cloth interface positions of adjacent layers. After flanging is completed, the part preform is obtained.

[0025] Step 5 specifically involves removing the first and second outer molds, taking out the graphite shaping fixture, machining the preform of the deposited part, and then performing silicon carbide substrate deposition treatment until the density is greater than 1.8 g / cm³. 3 This yields the final molded part.

[0026] Furthermore, in step 1.2, each sub-graphite inner mold is formed by splicing together multiple secondary sub-graphite inner molds.

[0027] Furthermore, a second sewing hole is provided on the side wall of the first outer mold for matching the first sewing hole and for through sewing.

[0028] Furthermore, the diameter of the vent is 4-5 mm, and the spacing between adjacent vents is 8-10 mm;

[0029] The diameter of the second sewing hole is 3-5mm, and the distance between adjacent second sewing holes is 10-12mm;

[0030] The diameter of the first sewing hole is 3-5mm, and the distance between adjacent first sewing holes is 10-12mm.

[0031] Further, in step 1.3, a carbon interface layer deposition process is first performed until the thickness of the carbon interface layer is 50-70 nm, followed by a silicon carbide substrate deposition process until the density is 1.3-1.5 g / cm³. 3 ;

[0032] In step 4, a carbon interface layer is first deposited until its thickness reaches 80-250 nm, followed by silicon carbide substrate deposition until the density reaches 1.4-1.6 g / cm³. 3 .

[0033] The beneficial effects of this invention are:

[0034] 1. This invention provides a molding method for narrow-cavity or closed-cavity ceramic matrix composite parts. In this method, the C / SiC inner mold and the ceramic matrix composite part to be molded are made of the same material. When used to mold the part, it does not need to be removed, which effectively solves the demolding problem caused by using solid graphite molds. It also effectively avoids abnormal phenomena such as part delamination, slow densification, and dust accumulation caused by solid graphite molds, and shortens the part preparation cycle.

[0035] 2. In this invention, staggering the carbon cloth interface positions of adjacent layers during the flanging process helps to ensure the strength of the parts at the interface positions.

[0036] 3. In this invention, each sub-graphite inner mold is formed by splicing together multiple secondary sub-graphite inner molds. The secondary sub-graphite molds are easy to remove and will not be damaged, so they can be reused, reducing costs. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the structure of one of the sub-forming tools after drilling in an embodiment of the present invention;

[0038] Figure 2 This is a schematic diagram of the structure of a C / SiC inner mold preform with a sub-graphite inner mold after being molded together with a sub-forming tooling, according to one embodiment of the present invention.

[0039] Figure 3 This is a schematic diagram of the installation of the sub-C / SiC inner mold preform with sub-graphite inner mold and the first outer mold in an embodiment of the present invention;

[0040] Figure 4 This is a schematic diagram of the installation of the sub-C / SiC inner mold, graphite shaping tooling, carbon cloth, and first outer mold in an embodiment of the present invention;

[0041] Figure 5 This is a schematic diagram of the structure of the part preform, graphite shaping tooling, and the first outer mold in an embodiment of the present invention; (the dotted line in the figure indicates the carbon cloth interface position).

[0042] Figure 6 This is a schematic diagram of the structure of the preformed part, the graphite shaping tooling, the first outer mold, and the second outer mold after they are joined together in an embodiment of the present invention.

[0043] Figure 7 This is a schematic diagram of the structure of the molded part obtained in the embodiment of the present invention.

[0044] Explanation of reference numerals in the attached figures:

[0045] 1-Ventilation hole, 2-First outer mold, 3-Part preform, 4-Second outer mold, 5-Sub-forming fixture, 6-Sub-C / SiC inner mold preform, 8-Graphite shaping fixture, 10-Second sewing hole, 11-First sewing hole. Detailed Implementation

[0046] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0047] A method for molding a narrow-cavity or closed-cavity ceramic matrix composite part includes the following steps:

[0048] Step 1: Fabricate 5 sub-C / SiC internal molds

[0049] Step 1.1: Fabricate 5 sub-forming fixtures 5, and set ventilation holes 1 on each of the 5 sub-forming fixtures 5. The inner surfaces of the 5 sub-forming fixtures are consistent with the outer surfaces of the 5 C / SiC inner molds to be formed. Fabricate 5 sub-graphite inner molds. The outer surface formed by splicing the 5 sub-graphite inner molds is consistent with the shape of the narrow cavity or closed cavity of the part to be formed. Fabricate the first outer mold 2 and the second outer mold 4. The inner surfaces of the first outer mold 2 and the second outer mold 4 are consistent with the outer surfaces of the part to be formed. The diameter of the ventilation holes 1 is 4-5mm, and the spacing between adjacent ventilation holes 1 is 8-10mm. See details below. Figure 1 ;

[0050] Step 1.2: Wrap multiple layers of carbon cloth around the two end faces and two opposite sides of each of the five sub-graphite inner molds without sewing. Trim the edges of the carbon cloth to be flush with the outer surface of the sub-graphite inner molds to obtain five sub-C / SiC inner mold preforms 6 with sub-graphite inner molds. The inner surfaces of the five sub-C / SiC inner mold preforms 6 are consistent with the outer surfaces of the five sub-graphite inner molds, and the outer surfaces of the five sub-C / SiC inner mold preforms 6 are consistent with the inner surfaces of the five sub-forming fixtures 5 in Step 1.1. In this embodiment, each sub-graphite inner mold is formed by splicing three secondary sub-graphite inner molds. See details... Figure 2 ;

[0051] Step 1.3, as follows Figure 2 As shown, after the five C / SiC inner mold preforms 6 with sub-graphite inner molds are respectively joined with the five perforated sub-forming fixtures 5 using an arc-shaped clamp, a carbon interface layer deposition process is first performed until the thickness of the carbon interface layer is 50-70 nm, and then a silicon carbide substrate deposition process is performed until the density is 1.3-1.5 g / cm³. 3 The deposition time was 150 hours.

[0052] Step 1.4, as follows Figure 3 As shown, after removing the sub-forming fixture 5, the five C / SiC inner mold preforms 6 after deposition treatment are spliced ​​onto the first outer mold 2, and the first sewing holes 11 are drilled. The diameter of the first sewing holes 11 is 3-5 mm, and the spacing between adjacent first sewing holes 11 is 10-12 mm. In this embodiment, the side wall of the first outer mold 2 is provided with second sewing holes 10 for drilling the first sewing holes 11 and for through sewing. The diameter of the second sewing holes 10 is 3-5 mm, and the spacing between adjacent second sewing holes 10 is 10-12 mm.

[0053] Step 1.5: Remove the first outer mold 2 and take out each of the secondary graphite inner molds to obtain 5 formed C / SiC inner molds;

[0054] Step 2.1, as follows Figure 4 As shown, based on the thickness and dimensions of the part to be formed, the number and size of the carbon cloth layers required for the part to be formed are calculated, and the layers are stacked on the first outer mold 2.

[0055] Step 2.2: Place the five sub-C / SiC inner molds obtained in Step 1.5 onto the carbon cloth after being stacked in Step 2.1, with both ends flush with the two ends of the first outer mold 2.

[0056] Step 2.3, as follows Figures 4-5 As shown, a graphite shaping fixture 8 is placed at the splicing position of the five sub-C / SiC inner molds and at the center of each sub-C / SiC inner mold. The graphite shaping fixture 8 serves as a support. Then, the edges are turned over to stagger the carbon cloth interface positions of adjacent layers. After the edges are turned over, the part preform 3 is obtained. The inner surface of the part preform 3 is consistent with the shape of the narrow cavity or closed cavity of the part to be formed.

[0057] Step 3, as follows Figure 6 As shown, the obtained prefabricated part 3 is sewn together with the first outer mold 2 and then joined with the second outer mold 4.

[0058] Step 4: Using the CVI process, first deposit a carbon interface layer on the molded part preform 3 until the thickness of the carbon interface layer is 80-250 nm, then deposit a silicon carbide substrate until the density is 1.4-1.6 g / cm³. 3 The deposition time was 240 hours.

[0059] Step 5, as follows Figure 7 As shown, the first outer mold 2 and the second outer mold 4 are removed, and the graphite shaping fixture 8 is taken out. The preform 3 of the part after deposition treatment is first machined, and then silicon carbide substrate deposition treatment is performed until the density is greater than 1.8 g / cm³. 3 This yields the final molded part.

[0060] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions within the technical scope disclosed in the present invention should be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for molding narrow-cavity or closed-cavity ceramic matrix composite parts, characterized in that, Includes the following steps: Step 1: Fabrication of C / SiC internal mold Step 1.1: Make a molding fixture and set a vent hole (1) on the molding fixture. The inner surface of the molding fixture is consistent with the outer surface of the C / SiC inner mold to be formed. Make a graphite inner mold. The outer surface of the graphite inner mold is consistent with the shape of the narrow cavity or closed cavity of the part to be formed. Make a first outer mold (2) and a second outer mold (4). The inner surfaces of the first outer mold (2) and the second outer mold (4) are consistent with the outer surface of the part to be formed. Step 1.2: Wrap multiple layers of carbon cloth around the two end faces and two opposite sides of the graphite inner mold without sewing. Trim the edges of the carbon cloth to be flush with the outer surface of the graphite inner mold to obtain a C / SiC inner mold preform with a graphite inner mold. Step 1.3: After the C / SiC inner mold preform with graphite inner mold is assembled with the punched molding tool, carbon interface layer deposition and silicon carbide substrate deposition are performed in sequence. Step 1.4: Remove the molding tooling, place the deposited C / SiC inner mold preform on the first outer mold (2), and drill the first sewing hole (11). Step 1.5: Remove the first outer mold (2), take out the graphite inner mold, and obtain the formed C / SiC inner mold; Step 2: Stack the carbon cloth required for the part to be formed on the first outer mold (2), place the obtained C / SiC inner mold on the stacked carbon cloth, and make the two ends of the C / SiC inner mold flush with the two ends of the first outer mold (2). After flanging, the part preform (3) is obtained; the inner surface of the part preform (3) is consistent with the shape of the narrow cavity or closed cavity of the part to be formed. Step 3: After sewing the obtained prefabricated part (3) through the first outer mold (2), assemble it with the second outer mold (4); Step 4: The preform of the molded part (3) is subjected to carbon interface layer deposition and silicon carbide substrate deposition treatment in sequence using CVI process; Step 5: Remove the first outer mold (2) and the second outer mold (4), and perform machining on the preform (3) after deposition treatment, and then perform silicon carbide substrate deposition treatment to obtain the final molded part.

2. The molding method for the narrow-cavity or closed-cavity ceramic matrix composite part according to claim 1, characterized in that: In step 1.1, the forming fixture is composed of N sub-forming fixtures (5); where N is an integer greater than or equal to 2; Step 1.2 specifically involves the following: the graphite inner mold is composed of N sub-graphite inner molds. Multiple layers of carbon cloth are wound around the two end faces and two opposite sides of the N sub-graphite inner molds without sewing. The edges of the carbon cloth are cut to be flush with the outer surface of the sub-graphite inner molds to obtain N sub-C / SiC inner mold preforms (6) with sub-graphite inner molds. The inner surfaces of the N sub-C / SiC inner mold preforms (6) are consistent with the outer surfaces of the N sub-graphite inner molds. The outer surfaces of the N sub-C / SiC inner mold preforms (6) are consistent with the inner surfaces of the N sub-forming fixtures (5) in step 1.

1. In step 1.3, the N sub-C / SiC inner mold preforms (6) with sub-graphite inner molds are respectively molded with the N sub-forming fixtures (5) after drilling; Step 1.4 specifically involves removing the sub-forming tooling (5), splicing the N sub-C / SiC inner mold preforms (6) after deposition treatment onto the first outer mold (2), and drilling the first sewing hole (11). Step 1.5 specifically involves removing the first outer mold (2), taking out each sub-graphite inner mold, and obtaining N formed sub-C / SiC inner molds; In step 2, the N sub-C / SiC inner molds obtained in step 1.5 are spliced ​​and placed on the stacked carbon cloth.

3. The molding method for narrow-cavity or closed-cavity ceramic matrix composite parts according to claim 2, characterized in that, Step 2 specifically includes the following sub-steps: Step 2.1: Calculate the number and size of carbon cloth layers required for the part to be formed based on the thickness and external dimensions of the part to be formed, and stack them on the first outer mold (2); Step 2.2: Place the N sub-C / SiC inner molds obtained in step 1.5 on the carbon cloth after stacking in step 2.1, with both ends flush with the two ends of the first outer mold (2); Step 2.3: Place graphite shaping fixtures (8) at the splicing positions of the N sub-C / SiC inner molds and at the center of each sub-C / SiC inner mold, and then perform flanging to stagger the carbon cloth interface positions of adjacent layers. After the flanging is completed, the part preform (3) is obtained. Step 5 specifically involves removing the first outer mold (2) and the second outer mold (4), taking out the graphite shaping fixture (8), machining the preform (3) after deposition treatment, and then performing silicon carbide substrate deposition treatment until the density is greater than 1.8 g / cm³. 3 This yields the final molded part.

4. The molding method for the narrow-cavity or closed-cavity ceramic matrix composite part according to claim 3, characterized in that: In step 1.2, each sub-graphite inner mold is formed by splicing together multiple secondary sub-graphite inner molds.

5. The molding method for narrow-cavity or closed-cavity ceramic matrix composite parts according to any one of claims 1-4, characterized in that: The first outer mold (2) has a second sewing hole (10) on its side wall for matching the first sewing hole (11) and for through sewing.

6. The molding method for the narrow-cavity or closed-cavity ceramic matrix composite part according to claim 5, characterized in that: The diameter of the vent (1) is 4-5 mm, and the spacing between adjacent vents (1) is 8-10 mm. The diameter of the second sewing hole (10) is 3-5mm, and the distance between adjacent second sewing holes (10) is 10-12mm; The diameter of the first sewing hole (11) is 3-5mm, and the distance between adjacent first sewing holes (11) is 10-12mm.

7. The molding method for the narrow-cavity or closed-cavity ceramic matrix composite part according to claim 6, characterized in that: In step 1.3, a carbon interface layer is first deposited until its thickness reaches 50-70 nm, followed by silicon carbide substrate deposition until the density reaches 1.3-1.5 g / cm³. 3 ; In step 4, a carbon interface layer is first deposited until its thickness reaches 80-250 nm, followed by silicon carbide substrate deposition until the density reaches 1.4-1.6 g / cm³. 3 .

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