A max phase brazing joint for ceramic matrix composite homogenous welding and a preparation method thereof

Abstract

The application provides a MAX phase brazing joint for ceramic matrix composite homogenous welding and a preparation method thereof, and relates to the technical field of welding. f S1. TiH2 powder, SiC powder, C powder and TiSi eutectic powder are mixed according to a mass ratio of (4.5-6):1:(2.5-3.5):(2-2.5) to obtain mixed powder; S2. The mixed powder is mixed with terpineol to obtain slurry; S3. The SiC f / SiC composite material to be welded is coated with the slurry to obtain a to-be-welded part; S4. The slurry on two to-be-welded parts is attached to obtain a to-be-welded assembly; S5. The to-be-welded assembly is subjected to ultrasonic-assisted brazing under vacuum conditions, heated to a preset temperature under a preset pressure, and set with ultrasonic power, ultrasonic time and a preset holding time to obtain a MAX phase brazing joint. The application can prepare a MAX phase brazing joint with high strength at ≤1400 DEG C.

Description

Technical Field

[0001] This invention relates to the field of welding technology, and more specifically to a MAX phase brazing head for homogeneous welding of ceramic matrix composites and its preparation method. Background Technology

[0002] Aero engines are facing a critical transition period, focusing on expanding applications to extreme high-temperature service environments and improving thrust-to-weight ratio performance. SiC f SiC composite materials, due to their low density, excellent high-temperature mechanical properties, oxidation resistance, and damage tolerance, far surpass conventional high-temperature alloys and ceramic materials, have become the preferred material for improving the high-temperature resistance and lightweight performance of hot-end components in aero-engines.

[0003] Brazing is a method for achieving SiC f The main technology for homogeneous welding of SiC composite materials. However, due to SiC... f SiC composite materials have a stable coordination structure, making diffusion and reaction with conventional bonding interlayer systems difficult. Furthermore, conventional active brazing methods are limited by their melting points and cannot meet the increasing demands of high-temperature service. Currently, SiC… f Homogeneous bonding of SiC composite materials faces challenges such as poor joint temperature resistance, high residual stress, and difficulty in coordinating and controlling the joint's microstructure and properties, significantly reducing the joint's service reliability. Therefore, the development of SiC... f High-performance brazed joints for homogeneous welding of SiC composite materials are an important prerequisite for effective connections.

[0004] Ternary transition metal carbides (nitrides) are collectively referred to as MAX phase materials, where M is a transition metal element, A is a group III or V element, X is carbon or nitrogen, and n is 1-6. The octahedral structure of the MAX phase is similar to the MX structure of binary carbides, thus it possesses some properties of binary carbides (such as SiC and TiC), such as good high-temperature resistance, wear resistance, and oxidation resistance. Under high-temperature conditions, A-layer atoms undergo outward diffusion, generating a large amount of oxides that can fill their own microcracks, preventing further oxidation. This results in excellent corrosion resistance, oxidation resistance, wear resistance, and oxidation-induced self-healing ability, and is considered a potential precursor to SiC. f One of the key materials for welding SiC composite materials.

[0005] Ti3SiC2 possesses a crystal structure with strongly covalently bonded Ti-C and Si layers stacked alternately, giving it the excellent properties of both metals and ceramics, namely high strength and high elastic modulus. Its melting point is 3000℃, and its decomposition temperature is above 1800℃. It has a matching lattice structure and coefficient of thermal expansion with SiC, exhibiting both high-temperature stability and plasticity, which can promote thermal stress relaxation in welded joints. Therefore, many studies have targeted Ti3SiC2 as a bonding agent for SiC and its composites.

[0006] Currently, there are two main pathways for preparing Ti3SiC2 brazed joints: MAX phase decomposition and in-situ synthesis. MAX phase decomposition requires high temperature and high pressure conditions (above 1500℃), which are demanding processes with long holding times and can easily exceed the temperature resistance of the fiber. In-situ synthesis can generate dense Ti3SiC2 and other MAX phases at the interface through reaction and diffusion. However, conventional brazing methods (such as adding Ti foil, Si powder, TiC, TiSi2, etc.) make it difficult to prepare brazed joints with a high-temperature shear strength ≥75MPa at brazing temperatures ≤1400℃. Summary of the Invention

[0007] In view of this, embodiments of this application provide a MAX phase brazing joint for homogeneous welding of ceramic matrix composites and its preparation method, to solve the problems of existing SiC... f The drawback of homogeneous welding of SiC composite materials is that it is difficult to prepare welded joints with a high-temperature shear strength ≥75MPa at brazing temperatures below 1400℃.

[0008] This application provides the following technical solution: a method for preparing a MAX phase brazing joint for homogeneous welding of ceramic matrix composites, comprising the following steps:

[0009] Step S1. Mix TiH2 powder, SiC powder, C powder, and TiSi eutectic powder in a mass ratio of (4.5-6):1:(2.5-3.5):(2-2.5) to obtain a mixed powder. Step S2. Mix the powder with terpineol at a preset mass ratio to obtain a slurry; Step S3. In SiC f The slurry is applied to the surface of the SiC composite material to be welded to obtain the workpiece to be welded. Step S4. Adhere the slurry on the two surfaces of the two parts to be welded together to obtain the assembly to be welded; Step S5. Under vacuum conditions, the components to be welded are subjected to ultrasonic-assisted brazing. The components are heated to a preset temperature under a preset pressure, and the ultrasonic power and ultrasonic time are set. After a preset holding time, the MAX phase brazed joint is obtained.

[0010] According to one embodiment of the present invention, in step S1, the TiSi eutectic powder is Si-14Ti by atomic percentage.

[0011] According to one embodiment of the present invention, step S1 further includes: adding CaF2 sintering aid to the mixed powder, wherein the amount of CaF2 sintering aid added is 3% to 5% of the total mass of the mixed powder.

[0012] According to one embodiment of the present invention, in step S2, the preset mass ratio is (7-8):1.

[0013] According to one embodiment of the present invention, in step S4, the thickness of the slurry in the component to be welded is 50-150 μm.

[0014] According to one embodiment of the present invention, in step S5, the preset pressure is 5-20 MPa.

[0015] According to one embodiment of the present invention, in step S5, the preset temperature is 1300-1400℃, the ultrasonic power is 300-600W, the ultrasonic time is 5-25s, and the heat preservation time is 45-75min.

[0016] The present invention also provides a MAX phase brazing head for homogeneous welding of ceramic matrix composites, which is prepared by the above method.

[0017] Compared with the prior art, the beneficial effects achieved by at least one of the above-mentioned technical solutions adopted in the embodiments of this specification include at least the following: The embodiments of this invention use TiH2+SiC+C as the basic reaction system, utilizing the thermal decomposition characteristics of TiH2 to provide a new titanium source for the joint; the addition of TiSi eutectic powder, using low-melting-point Ti-Si eutectic as a liquid phase aid and densification driving force, reduces the temperature and pressure required for welding; the addition of CaF2 sintering aid disrupts the Ti-C bond bonding, inhibits the formation of impurity phases such as TiC, and improves the MAX phase content distribution in the joint; the use of intense ultrasonic flow and stirring accelerates dissolution and element diffusion, overcoming the limitations of traditional brazing methods that require highly active brazing filler metals and high vacuum environments, improving the density of the welded joint, and thus enhancing its strength. In summary, by employing the in-situ synthesis joint preparation method of this invention, precisely controlling the Ti / Si / C stoichiometric ratio, thermodynamically driving the reaction towards the formation of Ti3SiC2, and kinetically utilizing liquid-phase accelerated diffusion and atomic exchange, a high-strength MAX phase (Ti3SiC2) brazed joint can be prepared at ≤1400℃. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic flowchart of the MAX phase brazing joint preparation method according to an embodiment of the present invention; Figure 2 This is a scanning electron microscope image of the MAX brazing head obtained in Embodiment 1 of the present invention. Detailed Implementation

[0020] The embodiments of this application will now be described in detail with reference to the accompanying drawings.

[0021] The following specific examples illustrate the implementation of this application. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. This application can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this application. It should be noted that, in the absence of conflict, the following embodiments and features in the embodiments can be combined with each other. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0022] like Figure 1 As shown, this invention provides a method for preparing MAX phase (Ti3SiC2) brazed joints for homogeneous welding of ceramic matrix composites. This method is a SiC... f The in-situ brazing synthesis method for SiC composite materials specifically includes the following steps: Step S1. Mix TiH2 powder, SiC powder, C powder, and TiSi eutectic powder in a mass ratio of (4.5-6):1:(2.5-3.5):(2-2.5) to obtain a mixed powder. The mixed powder is used to generate the MAX phase (Ti3SiC2) in situ in the brazing seam. Since the selected TiSi eutectic powder is in a Si-rich state, the ratio of Ti and C elements is appropriately increased. Step S2. Mix the powder with terpineol at a preset mass ratio to obtain a slurry; Step S3. In SiC f The slurry is applied to the surface of the SiC composite material to be welded to obtain the workpiece to be welded. Step S4. Adhere the slurry on the welding surfaces of the two parts to be welded to obtain the assembly to be welded; wherein the assembly to be welded is a sandwich structure of "base material-slurry-base material"; Step S5. Under vacuum conditions, the components to be welded are subjected to ultrasonic-assisted brazing. The components are heated to a preset temperature under a preset pressure, and the ultrasonic power and ultrasonic time are set. After a preset holding time, the MAX phase brazed joint is obtained.

[0023] This invention uses TiH2+SiC+C as the basic reaction system, utilizing the thermal decomposition of TiH2 to provide a new titanium source for the joint. TiSi eutectic powder is added, using the low-melting-point Ti-Si eutectic as a liquid-phase aid and densification driving force, reducing the temperature and pressure required for welding. CaF2 sintering aid is added to break the Ti-C bond, inhibiting the formation of impurity phases such as TiC, and improving the MAX phase content distribution in the joint. The intense ultrasonic flow and stirring action accelerate dissolution and element diffusion, overcoming the limitations of traditional brazing methods that require highly active filler metals and high-vacuum environments, thus increasing the density of the welded joint and improving its strength. In summary, the in-situ synthesis joint preparation method of this invention, by precisely controlling the Ti / Si / C stoichiometric ratio, thermodynamically drives the reaction towards the formation of Ti3SiC2, and kinetically utilizes liquid-phase accelerated diffusion and atomic exchange, enabling the preparation of high-strength MAX phase (Ti3SiC2) brazed joints at ≤1400℃.

[0024] In some embodiments of the present invention, in step S1, the TiSi eutectic powder is Si-14Ti (at.%); and further includes: adding CaF2 sintering aid to the mixed powder, wherein the amount of CaF2 sintering aid added is 3% to 5% of the total mass of the mixed powder.

[0025] In some embodiments of the present invention, in step S2, the preset mass ratio is (7-8):1.

[0026] In some embodiments of the present invention, in step S4, the thickness of the slurry in the component to be welded is 50-150 μm.

[0027] In some embodiments of the present invention, in step S5, the preset pressure is 5-20 MPa; the preset temperature is 1300-1400℃; the ultrasonic power is 300-600 W; the ultrasonic time is 5-25 s; and the heat preservation time is 45-75 min.

[0028] The present invention will be further described below with reference to specific embodiments.

[0029] Example 1 The preparation method of this embodiment includes the following steps: A1. Mix TiH2 powder, SiC powder, C powder, and TiSi eutectic powder in a mass ratio of 4.5:1:2.5:2 to obtain a mixed powder; add 3% CaF2 sintering aid by mass of the mixed powder.

[0030] A2. The mixed powder and terpineol are mixed at a preset mass ratio to obtain a slurry; the preset mass ratio is 7.5:1.

[0031] A3, in SiCf The slurry is applied to the surface of the SiC composite material to be welded, resulting in a workpiece to be welded; SiC f The thickness of the SiC composite material is 10 mm.

[0032] A4. The slurry on the two parts to be welded is bonded together to obtain a "base material-slurry-base material" sandwich structure assembly to be welded, wherein the thickness of the slurry in the assembly to be welded is 100μm.

[0033] A5. Under vacuum conditions, the component to be soldered is heated to a preset temperature under a preset pressure. After the solder melts, ultrasound is applied, with the end of the ultrasonic amplitude transformer acting on one side of the SiC. f An ultrasonic treatment is applied to the SiC composite material, and a welded joint is obtained after a preset heat preservation time; wherein the preset pressure is 10MPa, the preset temperature is 1350℃, the ultrasonic power is 600W, the ultrasonic time is 15s, and the heat preservation time is 60min.

[0034] Example 2 The preparation method of this embodiment includes the following steps: A1. Mix TiH2 powder, SiC powder, C powder, and TiSi eutectic powder in a mass ratio of 5:1:3:2 to obtain a mixed powder; add 4% CaF2 sintering aid by mass of the total mixed powder.

[0035] A2. The mixed powder and terpineol are mixed at a preset mass ratio to obtain a slurry; the preset mass ratio is 8:1.

[0036] A3, in SiC f The slurry is applied to the surface of the SiC composite material to be welded, resulting in a workpiece to be welded; SiC f The thickness of the SiC composite material is 10 mm.

[0037] A4. The slurry on the two parts to be welded is bonded together to obtain a "base material-slurry-base material" sandwich structure assembly to be welded, wherein the thickness of the slurry in the assembly to be welded is 125μm.

[0038] A5. Under vacuum conditions, the component to be soldered is heated to a preset temperature under a preset pressure. After the solder melts, ultrasound is applied, with the end of the ultrasonic amplitude transformer acting on one side of the SiC. f An ultrasonic treatment is applied to the SiC composite material, and a welded joint is obtained after a preset heat preservation time; wherein the preset pressure is 15MPa, the preset temperature is 1400℃, the ultrasonic power is 600W, the ultrasonic time is 25s, and the heat preservation time is 75min.

[0039] Example 3 The preparation method of this embodiment includes the following steps: A1. Mix TiH2 powder, SiC powder, C powder, and TiSi eutectic powder in a mass ratio of 6:1:3.5:2.5 to obtain a mixed powder; add 5% of the total mass of CaF2 sintering aid to the mixed powder.

[0040] A2. The mixed powder and terpineol are mixed at a preset mass ratio to obtain a slurry; the preset mass ratio is 7:1.

[0041] A3, in SiC f The slurry is applied to the surface of the SiC composite material to be welded, resulting in a workpiece to be welded; SiC f The thickness of the SiC composite material is 10 mm.

[0042] A4. The slurry on the two parts to be welded is bonded together to obtain a "base material-slurry-base material" sandwich structure assembly to be welded, wherein the thickness of the slurry in the assembly to be welded is 75μm.

[0043] A5. Under vacuum conditions, the component to be soldered is heated to a preset temperature under a preset pressure. After the solder melts, ultrasound is applied, with the end of the ultrasonic amplitude transformer acting on one side of the SiC. f An ultrasonic treatment is applied to the SiC composite material, and a welded joint is obtained after a preset heat preservation time; wherein the preset pressure is 5MPa, the preset temperature is 1300℃, the ultrasonic power is 300W, the ultrasonic time is 5s, and the heat preservation time is 45min.

[0044] Comparative Example 1 The preparation method of this comparative example includes the following steps: A1. Mix TiH2 powder, SiC powder, and C powder in a mass ratio of 4.5:1:2.5 to obtain a mixed powder.

[0045] A2. The mixed powder and terpineol are mixed at a preset mass ratio to obtain a slurry; the preset mass ratio is 7.5:1.

[0046] A3, in SiC f The slurry is applied to the surface of the SiC composite material to be welded, resulting in a workpiece to be welded; SiC f The thickness of the SiC composite material is 10 mm.

[0047] A4. The slurry on the two parts to be welded is bonded together to obtain a "base material-slurry-base material" sandwich structure assembly to be welded, wherein the thickness of the slurry in the assembly to be welded is 100μm.

[0048] A5. Under vacuum conditions, the component to be soldered is heated to a preset temperature under a preset pressure. After the solder melts, ultrasound is applied, with the end of the ultrasonic amplitude transformer acting on one side of the SiC. fAn ultrasonic treatment is applied to the SiC composite material, and a welded joint is obtained after a preset heat preservation time; wherein the preset pressure is 10MPa, the preset temperature is 1350℃, the ultrasonic power is 600W, the ultrasonic time is 15s, and the heat preservation time is 60min.

[0049] Comparative Example 2 The preparation method of this comparative example includes the following steps: A1. Mix TiH2 powder, SiC powder, C powder, and TiSi eutectic powder in a mass ratio of 4.5:1:2.5:2 to obtain a mixed powder.

[0050] A2. The mixed powder and terpineol are mixed at a preset mass ratio to obtain a slurry; the preset mass ratio is 7.5:1.

[0051] A3, in SiC f The slurry is applied to the surface of the SiC composite material to be welded, resulting in a workpiece to be welded; SiC f The thickness of the SiC composite material is 10 mm.

[0052] A4. The slurry on the two parts to be welded is bonded together to obtain a "base material-slurry-base material" sandwich structure assembly to be welded, wherein the thickness of the slurry in the assembly to be welded is 100μm.

[0053] A5. Under vacuum conditions, the components to be welded are heated to a preset temperature under a preset pressure and held for a preset time to obtain a welded joint; wherein, the preset pressure is 10MPa, the preset temperature is 1350℃, and the holding time is 60min.

[0054] The welded joint prepared in Example 1 was analyzed by scanning electron microscopy, and the results are as follows: Figure 2 As shown. From Figure 2 It can be seen that SiC f A MAX phase (Ti3SiC2) is formed between the SiC base material and the SiC matrix. The room temperature shear strength and high temperature shear strength of the welded joints prepared in Examples 1 to 3 and Comparative Examples 1 to 2 were tested, and the results are shown in Table 1. As can be seen from Table 1, compared with Comparative Examples 1 to 2, welded joints with a high temperature shear strength ≥75MPa were prepared in Examples 1 to 3 at a brazing temperature ≤1400℃.

[0055] Table 1 Shear Strength Comparison Table

[0056] The high-temperature shear strength in Table 1 refers to the shear strength at 1000℃.

[0057] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for preparing a MAX phase brazing joint for homogeneous welding of ceramic matrix composites, characterized in that, Includes the following steps: Step S1. Mix TiH2 powder, SiC powder, C powder, and TiSi eutectic powder in a mass ratio of (4.5-6):1:(2.5-3.5):(2-2.5) to obtain a mixed powder. Step S2. Mix the powder with terpineol at a preset mass ratio to obtain a slurry; Step S3. In SiC f The slurry is applied to the surface of the SiC composite material to be welded to obtain the workpiece to be welded. Step S4. Adhere the slurry on the two surfaces of the two parts to be welded together to obtain the assembly to be welded; Step S5. Under vacuum conditions, the components to be welded are subjected to ultrasonic-assisted brazing. The components are heated to a preset temperature under a preset pressure, and the ultrasonic power and ultrasonic time are set. After a preset holding time, the MAX phase brazed joint is obtained. In step S1, the TiSi eutectic powder is Si-14Ti by atomic percentage. In step S2, the preset mass ratio is (7-8):1; In step S4, the thickness of the slurry in the component to be welded is 50-150 μm; In step S5, the preset pressure is 5-20 MPa; In step S5, the preset temperature is 1300-1400℃, the ultrasonic power is 300-600W, the ultrasonic time is 5-25s, and the heat preservation time is 45-75min.

2. The preparation method according to claim 1, characterized in that, Step S1 further includes: adding CaF2 sintering aid to the mixed powder, wherein the amount of CaF2 sintering aid added is 3% to 5% of the total mass of the mixed powder.

3. A MAX phase brazing joint for homogeneous welding of ceramic matrix composites, characterized in that, It is prepared by the method described in claim 1.

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