Preparation method of ceramic matrix composite hollow inner cone for aero-engine

Abstract

The invention relates to a manufacturing method of aero-engine structural parts, in particular to a preparation method of a ceramic matrix composite hollow inner cone for an aero-engine. In order to overcome the defects that a high-temperature coating sprayed on the outer side of an existing ceramic-based composite material inner cone is prone to falling off, and the wave absorbing performance is affected, in the preparation method of the ceramic-based composite material hollow inner cone for the aero-engine, the hollow inner cone comprises a cone head, a cone head mounting nut, a cone face, a connecting ring, a mounting flange and other parts; the preparation method comprises the following steps: respectively preparing the parts, mounting the conical head mounting nut and the conical head, respectively connecting the connecting ring with the conical surface and the mounting flange in a rivet welding manner, depositing the Si3N4 matrix, independently splitting the conical head, and preparing the conical head by adopting Si3N4 ceramic, so that the size and profile design of the conical head are effectively ensured.

Description

Technical Field

[0001] This invention relates to a method for manufacturing structural components of aero-engines, specifically a method for preparing hollow inner cones of ceramic matrix composite materials for aero-engines. Background Technology

[0002] With the continuous development of aviation technology, the requirements for radar absorption performance of aircraft are becoming increasingly stringent. As a crucial system of aircraft, the aero-engine plays a decisive role in the radar absorption performance of the aircraft. Therefore, engine components also need to possess high radar absorption performance. As the power system of aircraft, the aero-engine operates at temperatures reaching thousands of degrees Celsius. Traditional high-temperature alloys can no longer meet the high-temperature requirements of aero-engines. Due to their excellent high-temperature resistance, ceramic matrix composites are gradually replacing high-temperature alloys as the preferred material for hot-end components of aero-engines. The inner cone, as a hot-end component at the tail of the aero-engine, needs to simultaneously meet the requirements of high-temperature resistance and radar absorption. Existing ceramic matrix composite inner cones typically use SiC / SiC composite materials with a high-temperature coating sprayed on the outside to achieve the radar absorption performance requirements. However, this coating is prone to peeling off, affecting the radar absorption performance. Summary of the Invention

[0003] The purpose of this invention is to address the shortcomings of existing ceramic matrix composite inner cones where the high-temperature coating sprayed on the outer side is prone to peeling off, affecting the microwave absorption performance, and to provide a method for preparing a hollow inner cone of ceramic matrix composite material for aero-engines.

[0004] To achieve the above objectives, the technical solution provided by this invention is as follows: A method for preparing a hollow inner cone made of ceramic matrix composite material for aero-engines, characterized by the following steps: Step 1: Prepare the parts for the cone head, cone head mounting nut, cone surface, connecting ring, and mounting flange respectively; The cone has a small hole at its apex for mounting a cone head; the cone head includes a ball head and a screw structure. Step 2, install the cone head mounting nut and cone head; The cone head is located at the apex of the cone surface, and the screw structure passes through a small hole at the apex and is threadedly connected to the cone head mounting nut. Step 3: Use pins to rivet and weld the connecting ring to the conical surface and the mounting flange respectively to obtain the hollow inner cone preform; The connecting ring is located on the inner side of the large end of the cone surface. Its outer surface shape matches the inner surface shape of the cone surface and abuts against the inner surface of the cone surface. It is connected by riveting and welding, and the bottom surface of the connecting ring is flush with the large end of the cone surface. The mounting flange is located at the large end of the conical surface and is riveted and welded to the bottom surface of the connecting ring; Step 4: Deposit Si3N4 substrate on the surface and internal voids of the hollow inner cone preform to fill the gap between the pin and the pin hole, thus completing the preparation of the hollow inner cone.

[0005] Furthermore, in step 1, the cross-section of the connecting ring is triangular, and the connecting ring is prepared by C-shaped layup to fill the fitting gap between the conical surface and the mounting flange.

[0006] Furthermore, in step 1, the cone head and the cone head mounting nut are formed by hot pressing and sintering of Si3N4 powder. The conical surface and mounting flange are both made of SiC / SiBCN composite material; The connecting ring is made of SiC / SiC composite material; Step 1 also includes sealing the connecting ring with the mating surfaces of the conical surface and the mounting flange.

[0007] Furthermore, in step 1, the conical mounting nut has four through slots evenly distributed around its circumference for installation.

[0008] Furthermore, in step 1, the large end of the conical surface extends radially outward to form a mounting boss, and the bottom surface of the connecting ring is flush with the bottom surface of the mounting boss. The mounting flange is provided with an inner conical mounting hole, the outer periphery of which fits against the mounting boss.

[0009] Furthermore, in step 1, the conical surface, connecting ring, and mounting flange are all formed by piercing through layers of two-dimensional plain-weave SiC fiber cloth.

[0010] The beneficial effects of this invention are: 1. In this invention, due to the large curvature change of the cone head surface and the large elastic modulus of the SiC fiber preform, if the cone head and the cone surface are formed with SiC fiber preform, the preform at the cone head will be broken, making it difficult to ensure the smoothness of the cone head's rounded corners. Therefore, the cone head is separated and made of Si3N4 ceramic, which effectively ensures the cone head's size and surface design.

[0011] 2. This invention divides the hollow inner cone into multiple parts. Materials that meet the performance requirements are selected. Parts exposed on the outer surface of the inner cone have the requirement of microwave absorption performance, so microwave absorbing materials are required. Parts encased inside the inner cone do not require microwave absorption performance, so high-temperature resistant ceramic matrix composites with excellent mechanical properties that do not absorb microwaves can be selected. Parts on the outer surface of the inner cone with load-bearing requirements are made of SiC fiber reinforced SiBCN ceramic matrix composites (SiC / SiBCN composites). Parts without load-bearing requirements are made of Si3N4 ceramic material with lower mechanical properties, which is hot-pressed and sintered. By selecting different preparation materials according to the requirements of mechanical properties and microwave absorption performance, the requirements of stability and microwave absorption performance can be taken into account at the same time.

[0012] 3. This invention uses SiC / SiBCN composite material with wave-absorbing properties as the material for the conical surface of the outer part of the hollow inner cone and the mounting flange. As a structural functional material, SiC / SiBCN composite material has multiple functions of load-bearing and wave absorption, eliminating the need for high-temperature coating on the outside and avoiding the problem of coating peeling off. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the hollow inner cone of ceramic matrix composite material in an embodiment of the present invention; Figure 2 This is an exploded view of the hollow inner cone of ceramic matrix composite material in an embodiment of the present invention; Figure 3 This is a cross-sectional view of the hollow inner cone of ceramic matrix composite material in an embodiment of the present invention; Figure 4 This is a schematic diagram of the cone head mounting structure in an embodiment of the present invention; Figure 5 This is a schematic diagram of the prefabricated layer structure in an embodiment of the present invention; Figure 6 This is a schematic diagram of the riveting and welding connection structure in an embodiment of the present invention.

[0014] Explanation of reference numerals in the attached figures: 1-Conical head, 2-Conical head mounting nut, 3-Conical surface, 4-Connecting ring, 5-Mounting flange, 6-Pin. Detailed Implementation

[0015] Figure 1 This is a schematic diagram of the external structure of a hollow inner cone made of ceramic matrix composite material. Based on the characteristics of composite material molding process, in order to facilitate the molding of the inner cone, the inner cone is disassembled into multiple parts and then assembled to form an integral structure.

[0016] like Figure 2 As shown, the inner cone of the ceramic matrix composite material includes a cone head 1, a cone head mounting nut 2, a cone surface 3, a connecting ring 4, and a mounting flange 5. The structure after assembly is as follows. Figure 3 As shown, the cone head 1, cone surface 3, and mounting flange 5 are the external structures of the hollow inner cone, which need to have wave absorption properties. The materials used for preparation are selected to have wave absorption properties. The cone surface 3 and the mounting flange 5 are thin-walled structures with equal wall thickness. SiC / SiBCN composite material is selected. A small hole is opened at the apex of the cone surface 3, and the large end of the cone surface 3 extends outward along the radial direction to form a mounting boss.

[0017] The cone head 1 includes a ball head and a screw structure. Due to the small size of the ball head, it is not conducive to the layup of composite preforms. Therefore, pure ceramic material Si3N4 is chosen as the material for preparing the cone head 1. The preparation method is simple, and Si3N4 material also possesses high temperature resistance and wave absorption properties. The cone head 1 is located at the apex of the inner cone, smoothly transitioning to the cone surface 3. The screw structure of the cone head 1 extends into a small hole at the apex of the cone surface 3 and is threadedly connected to the cone head mounting nut 2. The side of the cone head mounting nut 2 abuts against the inner wall of the cone surface 3. Figure 4 As shown, the cone-shaped mounting nut 2 has four through slots evenly distributed around its circumference to facilitate the installation of the cone-shaped mounting nut 2.

[0018] The connecting ring 4 is located inside the large end of the conical surface 3, abutting against the inner surface of the conical surface 3. Its outer surface shape matches the inner surface shape of the conical surface 3, and the bottom surface of the connecting ring 4 is flush with the bottom surface of the mounting boss at the large end of the conical surface 3. Since the connecting ring 4 is located inside the inner cone, it does not need to have wave-absorbing properties; therefore, its manufacturing material is selected as SiC / SiC composite material, which only needs to meet the high-temperature resistance requirement.

[0019] Figure 5 The diagram shows the connection between the connecting ring 4 and the mounting flange 5. The mounting flange 5 serves as the interface for connecting the inner cone to the aero-engine. It has mounting holes for the inner cone located at the large end of the cone surface 3, and its outer circumference fits against the mounting boss of the cone surface 3. To facilitate the forming of the inner cone, this invention treats the cone surface 3 and the mounting flange 5 as two separate parts, connected by the connecting ring 4 to improve structural stability. Therefore, the cone surface 3 and the connecting ring 4 are respectively provided with pin holes, and the connecting ring 4 and the mounting flange 5 are respectively provided with pin holes. They are connected by pins 6 installed in the pin holes. To facilitate the installation of the pins 6, an installation window is provided on the inner side of the connecting ring 4. Figure 6 The conical surface 3, connecting ring 4, and mounting flange 5 are connected together by online riveting and welding using SiC / SiBCN composite material pins 6. The conical surface 3, connecting ring 4, and mounting flange 5 are each formed by piercing layers of two-dimensional plain-weave SiC fiber cloth. Figure 5 The fine lines in the cross section show the fiber cloth direction of each part. The cross section of the connecting ring 4 is triangular. In order to fill the fitting gap between the conical surface 3 and the mounting flange 5, the connecting ring 4 is prepared by C-shaped plying. The prefabricated body is tightly sewn at the fitting surfaces of the connecting ring 4 with the conical surface 3 and the mounting flange 5 respectively to ensure the stability of the connection between the conical surface 3, the connecting ring 4 and the mounting flange 5.

[0020] The method for preparing hollow inner cones of ceramic matrix composite materials for aero engines according to the present invention includes the following steps: Step 1: Prepare the parts for cone head 1, cone head mounting nut 2, cone surface 3, connecting ring 4, and mounting flange 5 respectively, and seal the connecting ring 4 with the mating surfaces of cone surface 3 and mounting flange 5 respectively.

[0021] To facilitate fabrication and meet design specifications, the cone head 1 and the cone head mounting nut 2 are directly formed by hot pressing and sintering of Si3N4 powder.

[0022] The conical surface 3 and the mounting flange 5 are made of SiC / SiBCN composite material. In the SiC / SiBCN composite material, the SiBCN matrix is ​​prepared by a precursor impregnation pyrolysis process.

[0023] The connecting ring 4 is made of SiC / SiC composite material, in which the SiC matrix is ​​prepared by chemical vapor deposition.

[0024] Step 2: Install the cone mounting nut 2 and the cone 1 onto the cone surface 3.

[0025] Step 3: Use pins 6 with wave-absorbing properties to connect the conical surface 3, the connecting ring 4, and the mounting flange 5 together. First, connect the conical surface 3 to the inner wall of the connecting ring 4 with pins 6, and then connect the mounting flange 5 to the bottom surface of the connecting ring 4 with pins 6.

[0026] Step 4: Assemble all parts together through the above steps to obtain a hollow inner cone preform. Then, use chemical vapor deposition to deposit Si3N4 substrate on the surface and internal voids of the hollow inner cone preform to fill the gap between pin 6 and pin hole, improve the reliability of pin 6 connection, and complete the preparation of hollow inner cone.

Claims

1. A method for preparing a hollow inner cone made of ceramic matrix composite material for aero-engines, characterized in that, Includes the following steps: Step 1: Prepare the following parts respectively: cone head (1), cone head mounting nut (2), cone surface (3), connecting ring (4), and mounting flange (5); Among them, a small hole is opened at the apex of the cone surface (3) for setting the cone head (1); the cone head (1) includes a ball head and a screw structure; Step 2, install the cone mounting nut (2) and the cone (1); The cone (1) is located at the apex of the cone surface (3), and the screw structure passes through the small hole opened at the apex and is threadedly connected to the cone mounting nut (2); Step 3: Use pins (6) to rivet and weld the connecting ring (4) to the conical surface (3) and the mounting flange (5) respectively to obtain the hollow inner cone preform; The connecting ring (4) is located on the inner side of the large end of the cone (3). Its outer surface shape is adapted to the inner surface shape of the cone (3) and abuts against the inner surface of the cone (3). It is connected by riveting and welding. The bottom surface of the connecting ring (4) is flush with the large end of the cone (3). The mounting flange (5) is located at the large end of the conical surface (3) and is riveted to the bottom surface of the connecting ring (4); Step 4: Deposit Si3N4 substrate on the surface and internal voids of the hollow inner cone preform to fill the gap between the pin (6) and the pin hole, thus completing the preparation of the hollow inner cone.

2. The method for preparing a hollow inner cone of ceramic matrix composite material for aero-engines according to claim 1, characterized in that: In step 1, the cross section of the connecting ring (4) is triangular, and the connecting ring (4) is prepared by C-shaped plying to fill the fitting gap between the conical surface (3) and the mounting flange (5).

3. The method for preparing a hollow inner cone of ceramic matrix composite material for aero-engines according to claim 2, characterized in that: In step 1, the cone head (1) and the cone head mounting nut (2) are formed by hot pressing and sintering of Si3N4 powder; The conical surface (3) and the mounting flange (5) are both made of SiC / SiBCN composite material; The connecting ring (4) is made of SiC / SiC composite material; Step 1 also includes sealing the connecting ring (4) with the mating surfaces of the conical surface (3) and the mounting flange (5).

4. The method for preparing a hollow inner cone of ceramic matrix composite material for aero-engines according to any one of claims 1-3, characterized in that: In step 1, the cone-shaped mounting nut (2) has four through slots evenly distributed around its circumference for installation.

5. The method for preparing a hollow inner cone of ceramic matrix composite material for aero-engines according to claim 4, characterized in that: In step 1, the large end of the conical surface (3) extends radially outward to form a mounting boss, and the bottom surface of the connecting ring (4) is flush with the bottom surface of the mounting boss; The mounting flange (5) is provided with an inner cone mounting hole, the outer periphery of which fits against the mounting boss.

6. The method for preparing a hollow inner cone of ceramic matrix composite material for aero-engines according to claim 1, characterized in that: In step 1, the conical surface (3), the connecting ring (4), and the mounting flange (5) are all formed by piercing two-dimensional plain weave SiC fiber cloth.

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