Method for achieving C / C composite material connection through refractory metal powder sintering

Abstract

According to the method for achieving C / C composite material connection through sintering of the refractory metal powder, through spark plasma sintering of the refractory metal powder, ultra-high-temperature carbide ceramic is synthesized in situ in a connector, and therefore reliable connection of the C / C composite materials is achieved; the problems that an existing brazing / diffusion welding technology is complex in operation procedure, the high-temperature mechanical property of brazing filler metal is insufficient, and the joint application temperature is limited are solved. According to the method, the service performance of the C / C composite material joint in the ultra-high-temperature environment is greatly improved, pre-pressing and sintering are directly completed in the discharge plasma sintering furnace, operation is easy and convenient, sintering forming of the C / C composite material joint can be achieved under the low-temperature and rapid condition, production energy consumption is reduced, and connecting efficiency is improved.

Description

Technical Field

[0001] The present invention relates to the field of C / C composite material connection, and specifically is a method for realizing C / C composite material connection by sintering refractory metal powder in a spark plasma sintering furnace and synthesizing ultra-high temperature carbide ceramics in situ in a joint. The present invention can improve the connection quality and high temperature performance of the joint, and provide a reference for the connection and preparation of large and complex components of C / C composite materials. Background Art

[0002] With the rapid development of aerospace technology, higher requirements are put forward for rocket propulsion technology. As a key component of the thrust chamber of a rocket engine, the material used for the nozzle must have the characteristics of light weight, high strength, high temperature resistance, and ablation resistance. Carbon fiber reinforced carbon-based composite materials (C / C composite materials) are high-performance materials that have been rapidly developed and applied in the aerospace field in recent years. They have the characteristics of light specific gravity, strong thermal conductivity, excellent thermal shock resistance, friction and wear resistance, and good high temperature performance. They can still be used reliably and stably at a high temperature of 2000℃. Therefore, C / C composite materials are one of the best choices for the production and preparation of aerospace engine nozzle materials. However, it is still difficult to directly prepare large and complex components of C / C composite materials using preform weaving technology and chemical vapor infiltration process. Therefore, the development of high-performance connection technology of C / C composite materials is of great significance to promote the research and development and manufacturing of high thrust-to-weight ratio rocket engines.

[0003] The main connection methods for C / C composite materials are mechanical connection, bonding and welding. Mechanical connection will increase the weight of the components, while bonded components are difficult to serve in high temperature environments. In the welding method, since the melting point of C / C composite materials is above 3500℃ and oxidation will occur above 350℃, it is impossible to use traditional fusion welding techniques such as arc welding to achieve connection. Brazing and diffusion welding technologies are currently widely used methods for connecting C / C composite materials, but the brazing material used in brazing has a low melting point, which limits the high-temperature application of C / C composite joints; while diffusion welding has high requirements on the quality of the connection surface and requires long-term heating at high temperature, which can easily cause thermal damage to the C / C composite material.

[0004] Chinese patent CN 113182632 A discloses a method for brazing C / C composite materials using high entropy alloys. The method uses AlCoCrFeNi2.1 high entropy alloy brazing foil, and realizes vacuum brazing connection of C / C composite materials under the conditions of brazing temperature of 1410-1440°C and insulation for 8-15 minutes. The method is simple to operate, and retains high entropy structure in the weld, which ensures the stability of high temperature strength of the joint to a certain extent. However, since the melting point of AlCoCrFeNi2.1 high entropy alloy itself is between 1330°C and 1360°C, and contains Al elements with low melting point, the brazed joint formed is difficult to be used in high temperature fields above 1000°C, and the service temperature of the joint is limited.

[0005] Chinese patent CN 106747553 B discloses a method for connecting C / C composite materials, which first pre-oxidizes the C / C composite material to obtain a porous surface and a complete internal structure, then prepares Ti-Ni-Si intermediate layer powder by ball milling, mixes it with anhydrous ethanol to make an intermediate layer slurry, and then applies it to the connection surface of two C / C composite materials, places the entire pre-connector in a high-temperature furnace, heats it to 1500-2000℃, keeps it warm for 1-4h, and protects it with argon gas throughout the process, uses high temperature to transform the ceramic intermediate layer into a liquid phase to diffuse and penetrate into the connection matrix and react with it to produce chemical bonding, and realizes the connection between C / C composite materials under pressureless conditions, with a connection strength of 4.71-6.87MPa. Although this method solves the connection problem of C / C composite materials under traditional hot pressing conditions, the processing procedure is complicated, the equipment has a long insulation time at high temperature, the energy consumption is large, and the final joint connection strength is low, which is difficult to be applied in practice. Summary of the invention

[0006] In order to overcome the shortcomings of the prior art, the present invention provides a method for connecting C / C composite materials by sintering refractory metal powder. The purpose of the present invention is to provide a novel method for connecting C / C composite materials, which synthesizes ultra-high temperature carbide ceramics (melting point above 3000°C) in situ in the joint through spark plasma sintering of refractory metal powder, thereby realizing reliable connection of C / C composite materials and solving the problems of complex operation procedures of existing brazing / diffusion welding technology, insufficient high temperature mechanical properties of brazing materials, and limited application temperature of joints.

[0007] The main innovation of the present invention is to realize the connection of C / C composite materials by means of powder spark plasma sintering; the powder used is refractory metal powder of strong carbide forming elements; and the sintering method used is spark plasma sintering.

[0008] The technical solution adopted by the present invention to solve the technical problem comprises the following steps:

[0009] 1) The weight ratio of the C / C composite material to the refractory metal powder is 10:1, and the required weight of the refractory metal powder is weighed;

[0010] 2) spreading the refractory metal powder evenly on the C / C composite material, covering it with another C / C composite material, and assembling it in a "sandwich" structure to obtain an assembly;

[0011] 3) placing the assembly obtained in step 2) into a graphite mold, and placing the graphite mold in a spark plasma sintering furnace for pre-pressing;

[0012] 4) After pre-pressing, heating, heat preservation and cooling are carried out in a spark plasma sintering furnace to complete the sintering of refractory metal powder and the connection of C / C composite materials;

[0013] 5) Surface treatment, cleaning and drying of the C / C composite material connector obtained in step 4) are performed to obtain a C / C composite material.

[0014] Further, in step 1), the refractory metal powder is sieved with a screen having a mesh size of 200 to 400, and then the C / C composite material and the refractory metal powder are weighed in a weight ratio of 10:1, and the required weight of the refractory metal powder is weighed with an electronic balance;

[0015] Further, in step 2), the refractory metal powder is evenly spread on the C / C composite material with a specification of 10 mm×10 mm×3 mm, the powder is evenly flattened with a medicine spoon, and another piece of C / C composite material with a specification of 10 mm×10 mm×3 mm is covered on the flattened powder to complete the "sandwich" structure assembly to obtain an assembly;

[0016] Further, in step 3), the graphite mold has a specification of Φ20-50 mm and is pre-pressed in a spark plasma sintering furnace with a pre-pressing pressure of 5-10 kN for 10-20 min at room temperature;

[0017] Furthermore, the specific steps of step 4) are:

[0018] In a spark plasma sintering furnace, powder sintering and C / C composite material connection are simultaneously realized, the pressure is set to 5-10 kN, the heating rate is 50-100°C / min, the heating temperature is set to be 50-100°C lower than the melting point of the refractory metal, the holding time is 0.5-1h, and the cooling rate is 50-100°C / min to obtain a C / C composite material connector;

[0019] Further, in step 5), the particles and powder impurities overflowing near the weld of the C / C composite connector are polished and removed using sandpaper with a mesh number of 200#, ultrasonically cleaned in 10 mL of acetone or alcohol solution for 10 minutes, placed in a drying oven, and kept warm at 200°C for 10 minutes.

[0020] The refractory metal powder described in the present invention includes one of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, and W, or a mixture of two or more of the above and then subjected to spark plasma sintering.

[0021] At the same time, the present invention also provides a C / C composite material connector realized by sintering refractory metal powder, which is manufactured by the above method.

[0022] The beneficial effects of the present invention are:

[0023] 1. AlCoCrFeNi is used in the background technology 2.1 High entropy alloy brazing foil brazes C / C composite materials, and the high entropy structure is retained in the joint; compared with the welding method in the background art, the joint of the present invention finally forms ultra-high temperature carbide ceramics, which has a melting point much higher than AlCoCrFeNi 2.1 High entropy alloys can greatly improve the service performance of C / C composite joints in ultra-high temperature environments.

[0024] 2. In the background technology, the C / C composite material is pre-oxidized before welding, and the Ti-Ni-Si intermediate layer powder is prepared by ball milling, and it needs to be mixed with anhydrous ethanol and stirred to form an intermediate layer slurry before brushing, and then the welding is completed in a high-temperature furnace; compared with the welding method in the background technology, the present invention adopts a spark plasma sintering method, and there is no need to treat the C / C composite material before welding. Refractory metal powder is directly used, and there is no need for ball milling, slurry preparation and other processes. After spreading and assembling, pre-pressing and sintering are completed directly in a spark plasma sintering furnace, and the operation is simple and convenient.

[0025] 3. The present invention adopts a spark plasma sintering process, which can achieve sintering at a temperature lower than the melting point of the refractory metal, and the insulation time is only 0.5h. It can achieve the sintering molding of C / C composite material joints under low temperature and fast conditions, reduce production energy consumption, and improve connection efficiency.

[0026] 4. Under the process window of the present invention, and under the condition that the size of the internal furnace chamber of the spark plasma sintering equipment allows, large-sized C / C composite material butt joint structures or special-shaped parts can be quickly connected, and ultra-high temperature carbide ceramics can be synthesized in situ in the joint to obtain a connection structure that can be used at high temperatures. In addition, this method is also of reference significance for the connection of C / C composite materials and metals. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 A schematic diagram of the assembly of a C / C composite material butt-jointed structure graphite mold made by the present invention;

[0028] Figure 2 is the spark plasma sintering process curve in Example 1;

[0029] Figure 3 This is a backscattered electron image of the C / C composite material connection joint made in Example 1 under a scanning electron microscope;

[0030] Figure 4 The EDS element analysis results of the C / C composite material joint made in Example 1 are as follows: (a) the overall structure of the joint and the point analysis position, (b) the Zr element surface scanning diagram, (c) the C element surface scanning diagram, (d) the surface scanning spectrum and the point analysis results;

[0031] Figure 5 This is the EDS line scanning analysis result of the C / C composite material connection joint made in Example 1;

[0032] Figure 6 is the spark plasma sintering process curve in Example 2;

[0033] Figure 7 This is a backscattered electron image of the C / C composite material connection joint made in Example 2 under a scanning electron microscope;

[0034] Figure 8 The EDS element analysis results of the C / C composite material joint made in Example 2 are as follows: (a) the overall structure of the joint and the point analysis position, (b) the Ti element surface scanning diagram, (c) the C element surface scanning diagram, (d) the surface scanning spectrum and the point analysis results;

[0035] Fig. 9 This is the EDS line scanning analysis result of the C / C composite material connection joint produced in Example 2. DETAILED DESCRIPTION

[0036] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0037] A method for connecting C / C composite materials by sintering refractory metal powders comprises the following steps:

[0038] 1) First, a batch of 200-400 mesh refractory metal powder is screened, and then the required weight of refractory metal powder is weighed with an electronic balance according to the weight ratio of C / C composite material to refractory metal powder being 10:1;

[0039] 2) Spread the refractory metal powder evenly on the C / C composite material with a specification of 10 mm×10 mm×3 mm, flatten the powder evenly with a spatula, and then cover the flattened powder with another C / C composite material with a specification of 10 mm×10 mm×3 mm to complete the "sandwich" structure assembly and obtain an assembly;

[0040] 3) placing the assembly obtained in step 2) into a graphite mold with a specification of Φ20-50 mm, placing the graphite mold in a spark plasma sintering furnace for pre-pressing, the pre-pressing pressure is 5-10 kN, the time is 10-20 min, and the process is carried out at room temperature;

[0041] 4) After pre-pressing, powder sintering and C / C composite material connection are simultaneously realized in a spark plasma sintering furnace, the pressure is set to 5-10 kN, the heating rate is 50-100 ° C / min, the heating temperature is set to be 50-100 ° C lower than the melting point of the refractory metal, the holding time is 0.5-1 h, and the cooling rate is 50-100 ° C / min to obtain a C / C composite material connector;

[0042] 5) The C / C composite material connector obtained in step 4) is polished and removed with 200# sandpaper to remove impurities such as particles and powder overflowing near the C / C composite material weld, ultrasonically cleaned in 10 mL of acetone or alcohol solution for 10 min, placed in a drying oven, and kept warm at 200° C. for 10 min.

[0043] In order to test the joint quality of the C / C composite butt joint components manufactured by the method of the present invention, the C / C composite butt joint components manufactured above were cut in a direction perpendicular to the connection interface to prepare metallographic specimens. Under a scanning electron microscope, it was observed that the joint had obvious ultra-high temperature carbide ceramic structure, and the joint was continuous and dense without pores or cracks. The element distribution of the joint structure was characterized by EDS, and the mechanical properties of the C / C composite connector were characterized by testing the shear strength.

[0044] The method of the present invention can not only be used to batch produce C / C composite material butt joint components, expand the molding size of C / C composite materials, and extend their application in high temperature environments, but also serve as a reference for the connection of heterogeneous composite components composed of C / C composite materials and metals, thereby achieving high-quality connection of C / C composite material heterogeneous composite components.

[0045] The specific embodiments are as follows:

[0046] Example 1

[0047] This embodiment takes Zr powder as an example to further illustrate the method of in-situ synthesis of ultra-high temperature carbide ceramics to connect C / C composite materials, including the following steps:

[0048] 1) First, sieve a batch of Zr powder with a mesh size of 200, and then weigh 0.4 g of Zr powder from it;

[0049] 2) Spread the Zr powder evenly on the C / C composite material with a size of 10 mm × 10 mm × 3 mm, flatten the powder evenly with a spatula, and then cover the flattened powder with another piece of C / C composite material with a size of 10 mm × 10 mm × 3 mm to complete the "sandwich" structure assembly;

[0050] 3) placing the assembly obtained in 2) into a graphite mold with a specification of Φ20 mm, placing the graphite mold in a spark plasma sintering furnace for pre-pressing, the pre-pressing pressure is 5 kN, the time is 10 min, and the pre-pressing is performed at room temperature;

[0051] 4) After pre-pressing, powder sintering and C / C composite material connection are realized simultaneously in a spark plasma sintering furnace, with a heating rate of 100℃ / min, a heating temperature of 1800℃ (lower than the melting point of Zr 1852℃), a holding time of 0.5h, a cooling rate of 100℃ / min, and after sintering, the C / C composite material connection sample is taken out. The process curve of the entire spark plasma sintering process is shown in Figure 2 As shown;

[0052] 5) The C / C composite material connector obtained in step 4) is polished and removed with 200# sandpaper to remove impurities such as particles and powder overflowing near the C / C composite material weld, ultrasonically cleaned in 10 mL of acetone or alcohol solution for 10 min, placed in a drying oven, and kept warm at 200° C. for 10 min.

[0053] Figure 3 The backscattered electron image of the C / C composite material joint interface obtained in Example 1 under a scanning electron microscope is shown in FIG. Figure 3 It can be seen that the interface of the C / C composite joint is well bonded, and the joint is composed of ZrC ceramic structures of different components after carbonization of Zr powder; Figure 4 The element surface distribution and point analysis results of the C / C composite material joint prepared in Example 1 are as follows: Figure 5 The element line scan results of the C / C composite material joint prepared in Example 1 show that the Zr element content in the middle area of ​​the joint is slightly higher than that on both sides. The shear strength of the C / C composite material joint obtained in this example is 16.56±1.14MPa.

[0054] Example 2

[0055] The difference between this embodiment and embodiment 1 is that the powder weighed in step 1) is Ti powder; the heating temperature in step 4) is different, and the heating temperature in this embodiment is 1600°C (lower than the melting point of Ti 1675°C), and the other sintering process parameters are the same as those in embodiment 1. The process curve of the entire spark plasma sintering process is shown in FIG. Figure 6 As shown; Figure 7 The backscattered electron image of the C / C composite material joint interface prepared in Example 2 under a scanning electron microscope shows that the C / C composite material joint interface is well bonded without defects such as cracks and pores, and the joint is formed by carbonizing Ti powder to form TiC ceramic structures of different components; Figure 8 The element surface distribution and point analysis results of the C / C composite material joint prepared in Example 2 are as follows: Fig. 9 The element line scan results of the C / C composite material joint prepared in Example 2 show that the Ti element content in the middle area of ​​the joint is higher than that on both sides. The shear strength of the C / C composite material joint obtained in this example is 17.78±1.23MPa.

[0056] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can easily think of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should be included in the protection scope of the present invention.

Claims

1. A method for connecting C / C composite materials by sintering refractory metal powder, characterized in that The steps include: 1) The weight ratio of the C / C composite material to the refractory metal powder is 10:1, and the required weight of the refractory metal powder is weighed; 2) Spreading the refractory metal powder evenly on the C / C composite material, covering it with another C / C composite material, and assembling it in a "sandwich" structure to obtain an assembly; 3) placing the assembly obtained in step 2) into a graphite mold, and placing the graphite mold in a spark plasma sintering furnace for pre-pressing; 4) After pre-pressing, heating, heat preservation and cooling are carried out in a spark plasma sintering furnace to complete the sintering of refractory metal powder and the connection of C / C composite materials; 5) Surface treatment, cleaning and drying of the C / C composite material connector obtained in step 4) are performed to obtain a C / C composite material.

2. The method for connecting C / C composite materials by sintering refractory metal powder according to claim 1, characterized in that: In step 1), the refractory metal powder is sieved with a screen of 200-400 meshes, and then the C / C composite material and the refractory metal powder are weighed according to a weight ratio of 10:1, and the required weight of the refractory metal powder is weighed with an electronic balance.

3. The method for connecting C / C composite materials by sintering refractory metal powder according to claim 1, characterized in that: In step 2), the refractory metal powder is evenly spread on the C / C composite material with a specification of 10 mm×10 mm×3 mm, the powder is evenly flattened with a spatula, and then another piece of C / C composite material with a specification of 10 mm×10 mm×3 mm is covered on the flattened powder to complete the "sandwich" structure assembly to obtain an assembly.

4. The method for connecting C / C composite materials by sintering refractory metal powder according to claim 1, characterized in that: In step 3), the graphite mold has a specification of Φ20-50 mm and is pre-pressed in a spark plasma sintering furnace with a pre-pressing pressure of 5-10 kN for 10-20 min at room temperature.

5. The method for connecting C / C composite materials by sintering refractory metal powder according to claim 1, characterized in that: Step 4) The specific steps are: Powder sintering and C / C composite material joining are realized simultaneously in a spark plasma sintering furnace, with a pressure of 5-10 kN, a heating rate of 50-100 °C / min, and a heating temperature of 50-100 °C below the melting point of the refractory metal. 100°C, the holding time is 0.5-1h, the cooling rate is 50-100°C / min, and a C / C composite material connector is obtained.

6. The method for connecting C / C composite materials by sintering refractory metal powder according to claim 1, characterized in that: In step 5), the particles and powder impurities overflowing near the weld of the C / C composite connector are polished and removed using 200# sandpaper, ultrasonically cleaned in 10 mL of acetone or alcohol solution for 10 min, placed in a drying oven, and kept at 200° C. for 10 min.

7. A C / C composite material connector manufactured by the method of claim 1, characterized in that: The C / C composite material connector is realized by sintering refractory metal powder and is manufactured by the method of claims 1-6.

8. The C / C composite material connector according to claim 7, characterized in that: The refractory metal powder includes one of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, and W, or a mixture of two or more of the above and then subjected to spark plasma sintering.

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