A control SiC f Method for strengthening toughness of heterogeneous brazing joints of SiC composite materials

Abstract

The present invention discloses a method for regulating SiC f The invention relates to a method for strengthening the toughness of heterogeneous brazing joints of SiC composite materials, which belongs to the field of brazing technology and adopts the structure of high entropy brazing material-metal foam-high entropy brazing material to strengthen the toughness of SiC composite materials. f / SiC composite heterogeneous joints are brazed; wherein the high-entropy brazing filler metal is composed of Co, V, Pd, Ta, and Cr, with the mass percentage of each element being 18-25%. By introducing a buffer metal foam and a dedicated high-entropy brazing filler metal to work synergistically, the present invention achieves a microstructure gradient effect based on secondary high-entropy treatment. The metal foam's inherent 3D structure exhibits a long-lasting mechanism throughout the entire welding process. The combination of the dedicated high-entropy brazing filler metal and the buffer metal foam results in a brazed joint with excellent microstructure, low residual stress, high strength, and good toughness, suitable for high-temperature service.

Description

Technical Field

[0001] The present invention relates to the field of brazing technology, in particular to a method for regulating SiC f Method to improve the strength and toughness of heterogeneous brazing joints of / SiC composite materials. Background Art

[0002] In recent years, as the main combat equipment in the aerospace field, the high efficiency and high reliability of the new generation of aircraft engines are in urgent need of realization. f / SiC composite material is a new material obtained by compounding SiC fiber with SiC matrix. It has excellent chemical and physical compatibility. Its outstanding advantages are high specific modulus, high specific strength, low linear expansion coefficient, high temperature resistance, oxidation resistance and corrosion resistance. It is the preferred material for the hot end components of aircraft engines. In practical applications, it is usually brazed with high-temperature alloys to prepare lightweight, high-temperature resistant and high-strength hot end structural parts.

[0003] At present, there are many studies on the brazing connection of ceramic matrix composites and high temperature alloys in aircraft engines, but there is no research on SiC f There are few studies on the brazing connection of C / C composites and high temperature alloys. Most of them are studies on the brazing connection of C / C composites, C / SiC composites and high temperature alloys, such as CN103408317A and CN109047963B. Compared with SiC f / SiC composites, C / C composites, and C / SiC composites have different matrix phases and reinforcement methods, and the resulting brazed joints have poor toughness and cannot achieve high-temperature service; while SiC f In the brazing connection of SiC composite materials and high-temperature alloys, although the high-entropy brazing filler metal used in CN115229382A can achieve the connection, the toughness of the joint cannot be guaranteed and the high residual stress cannot be effectively relieved.

[0004] At the same time, in the study of SiC f Although high entropy brazing materials have been used in brazing of heterogeneous materials such as SiC / SiC composites, they have not been focused on f / SiC composite materials are designed and developed special brazing filler metals; in terms of organizational performance optimization, there have been related reports on the introduction of intermediate layers such as metal foam to alleviate residual stress (such as CN106493443B, CN105397224A, CN104690385A). Although the interface organization can be regulated, only the impact on stress and performance is studied in a single way, and the long-term action mechanism of the metal foam skeleton has not been deeply studied, and the toughness has not been improved on the basis of high strength.

[0005] Therefore, how to provide a method to obtain SiC fA method for achieving excellent microstructure, low residual stress, high strength and good toughness in heterogeneous brazing joints of / SiC composite materials is an urgent problem to be solved by those skilled in the art. Summary of the Invention

[0006] The present invention aims to propose a method for regulating SiC f A method for strengthening the toughness of heterogeneous brazing joints of / SiC composite materials is provided. The present invention introduces a buffer metal foam and a special high-entropy brazing filler metal to achieve a synergistic effect, thereby obtaining a tissue gradient effect on the basis of achieving secondary high-entropy. The 3D structure of the metal foam itself presents a long-term action mechanism throughout the entire welding process. At the same time, the combination of the special high-entropy brazing filler metal and the buffer metal foam will obtain a brazing joint with excellent tissue structure, low residual stress, high strength and good toughness that can meet the requirements of high-temperature service.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] A control SiC f / SiC composite material heterogeneous brazing joint toughness method, using high entropy brazing filler metal foam-high entropy brazing filler structure to strengthen SiC f Brazing of heterogeneous joints of / SiC composite materials;

[0009] The high entropy solder consists of Co, V, Pd, Ta and Cr, and the mass percentage of each element is 18-25%.

[0010] Preferably, the high entropy solder is a foil with a thickness of 50-100 μm.

[0011] Preferably, the high entropy solder is a foil with a thickness of 50 μm.

[0012] Preferably, the SiC f The SiC / SiC composite material is composed of a continuous silicon carbide fiber reinforced silicon carbide matrix, and its structure is any one of 2D, 2.5D and 3D weaving.

[0013] Preferably, the metal foam is a metal matrix foam with a three-dimensional structure.

[0014] Preferably, the metal foam is based on Ti or Mo.

[0015] Preferably, the thickness of the metal foam is no more than 1 mm, and the porosity is no less than 90%.

[0016] Preferably, the brazing conditions are: vacuum degree is 3-6×10 -3 Pa, brazing temperature is 1100-1200℃, and holding time is 20min.

[0017] Preferably, the specific steps of the method are:

[0018] SiC f / SiC composite materials, high temperature alloys, high entropy brazing filler metals and metal foams are cleaned from top to bottom according to the SiC f The / SiC composite material, high entropy brazing filler metal, metal foam, high entropy brazing filler metal and high temperature alloy are assembled in sequence and brazed.

[0019] Preferably, the SiC f The surfaces to be welded of the SiC / SiC composite material and the high-temperature alloy need to be flattened.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The present invention proposes a method for regulating the strength and toughness of SiCf / SiC composite heterogeneous brazing joints. The present invention uses a special high entropy brazing filler metal and a metal buffer foam in combination to achieve secondary high entropy on the basis of optimizing the organizational structure, and simultaneously obtains a gradient of organizational stress. The high residual stress inside the heterogeneous joint is effectively released, and a high-strength and high-toughness brazing joint is obtained. The special high entropy brazing filler metal can achieve SiC f / Connection of SiC composite materials with various high-temperature alloys; This invention will accurately locate and diversify the solution of SiC f The problems of high stress, poor performance and difficulty in meeting high temperature service in heterogeneous brazed joints of / SiC composite materials are discussed. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. The drawings in this description are merely embodiments of the present invention.

[0023] Figure 1 This is a structural diagram of the product assembly according to an embodiment of the present invention;

[0024] Figure 2 This is a diagram of the high entropy alloy structure in an embodiment of the present invention;

[0025] Figure 3 This is a flow chart of heterogeneous brazing of SiCf / SiC composite materials in an embodiment of the present invention;

[0026] Figure 4 This is a comparison diagram of the microstructure of the brazed joints of the products prepared in Example 1 and Comparative Example 1 of the present invention;

[0027] Figure 5 This is the microstructure diagram of the brazed joint of the product prepared in Example 2 of the present invention;

[0028] Figure 6The stress-displacement curves of the brazed joints of the products prepared in Examples 1-2 and Comparative Example 1 of the present invention are shown;

[0029] Figure 7 This is a comparison of the microstructures of the brazed joints of the products prepared in Example 3 and Comparative Example 2 of the present invention;

[0030] Figure 8 The stress-displacement curves of the brazed joints of the products prepared in Example 3 and Comparative Example 2 of the present invention are shown;

[0031] Figure 9 This is the microstructure diagram of the brazed joint of the product prepared in Example 4 of the present invention;

[0032] Figure 10 This is the microstructure diagram of the brazed joint of the product prepared in Example 5 of the present invention;

[0033] Among them, 1-SiC f / SiC composite materials, 2-high entropy brazing filler metal, 3-metal foam, 4-high temperature alloy. DETAILED DESCRIPTION

[0034] The following describes embodiments of the present invention, examples of which are shown in the accompanying drawings. The embodiments described with reference to the accompanying drawings are exemplary and intended to be used to explain the present invention, but are not to be construed as limiting the present invention.

[0035] Example 1

[0036] like Figure 3 The present invention provides a method for regulating SiC f A method for strengthening the toughness of a heterogeneous brazing joint of a SiC composite material comprises the following steps:

[0037] (1) Design and smelt high entropy solder with a composition of 22% Co-20% V-21% Pd-19% Ta-18% Cr and prepare it into a foil with a thickness of 50 μm ( Figure 2 High entropy alloy organization diagram), spare;

[0038] (2) SiC f / SiC composite materials, nickel-based high-temperature alloys, high-entropy brazing filler metals and metal foam Mo were ultrasonically cleaned in alcohol for 15 minutes. f The surfaces of the SiC composite material and the high-temperature alloy to be welded are flattened by using 80#, 400#, 800#, 1500#, and 2000# SiC sandpaper to grind them in sequence until the brazing interface is clean, smooth, and free of contamination. They are then polished until the sample surface is smooth and mirror-like. The thickness of the metal foam is 1mm, and the porosity is not less than 90%.

[0039] (3) The material obtained in step (2) is placed in the order of SiCf / SiC composite material, high entropy brazing filler metal, metal foam, high entropy brazing filler metal and nickel-based high temperature alloy are stacked and assembled in a "hamburger-like" order (structure as shown in FIG. Figure 1 ), the assembled samples were moved into a vacuum brazing furnace for brazing. The vacuum degree was maintained at 1×10 -2 Pa, the brazing temperature is 1100-1200℃, and the holding time is 20min; the microstructure, shear strength and toughness of the product are evaluated.

[0040] Comparative Example 1

[0041] The difference from Example 1 is that: from top to bottom, the SiC f The / SiC composite material, high entropy solder and high-temperature alloy are stacked and assembled in sequence, and the remaining steps and parameters are the same as those in Example 1.

[0042] like Figure 4 This is a comparison diagram of the microstructures of the brazed joints of the products prepared in Example 1 and Comparative Example 1, where a is the product of Comparative Example 1 and b is the product of Example 1. It can be seen from the figure that the weld microstructure uniformity of the joint using only high-entropy alloy is poor, especially the brittle phase concentrated band area appears on the high-temperature alloy side, which will deteriorate the joint microstructure; after introducing metal foam and high-entropy alloy composite brazing, the weld microstructure is uniform and penetrates into the composite fiber on the composite material side, which will improve the welding effect.

[0043] Example 2

[0044] The difference from Example 1 is that the high entropy solder is prepared as a foil with a thickness of 100 μm, and the remaining steps and parameters are the same as Example 1.

[0045] like Figure 5 This is the microstructure diagram of the brazed joint of the product prepared in Example 2. It can be seen from the figure that thickening the high-entropy brazing material layer will prevent the atoms in the brazing seam from reacting uniformly, resulting in the existence of unweldable areas on the composite material side.

[0046] like Figure 6 The stress-displacement curves of the brazed joints of the products prepared in Examples 1-2 and Comparative Example 1 are shown. As can be seen from the figure, the strength and toughness of the joints are significantly improved through the synergistic effect of the metal foam and the high-entropy brazing filler metal.

[0047] Example 3

[0048] The difference from Example 1 is that the composition of the high entropy solder is 20% Co-20% V-20% Pd-20% Ta-20% Cr, and the remaining steps and parameters are the same as Example 1.

[0049] Comparative Example 2

[0050] The difference from Example 2 is that: from top to bottom, the SiCf The / SiC composite material, high entropy solder and high-temperature alloy are stacked and assembled in sequence, and the remaining steps and parameters are the same as those in Example 2.

[0051] like Figure 7 The following is a comparison of the microstructures of the brazed joints of the products prepared in Example 3 and Comparative Example 2, where a is the product of Comparative Example 2 and b is the product of Example 3. As can be seen from the figure, the joint without the addition of metal foam Mo has an unwelded area close to the composite material side, and the phase structure in the weld is "aggregated", which worsens the stress level inside the weld; after adding metal foam Mo, a large amount of blocky solid solution appears in the weld and is effectively connected to the composite material.

[0052] like Figure 8 The stress-displacement curves of the brazed joints of the products prepared in Example 3 and Comparative Example 2 show that the strength and toughness of the joints are significantly improved through the synergistic effect of the metal foam and the high-entropy brazing filler metal.

[0053] Example 4

[0054] The difference from Example 1 is that metal foam Ti is used, and the remaining steps and parameters are the same as Example 1.

[0055] like Figure 9 This is the microstructure diagram of the brazed joint of the product prepared in Example 4. It can be seen from the figure that adding metal foam Ti can also obtain a brazed joint with excellent microstructure.

[0056] Example 5

[0057] The difference from Example 1 is that a niobium-based high-temperature alloy is used, and the remaining steps and parameters are the same as Example 1.

[0058] like Figure 10 This is the microstructure diagram of the brazed joint of the product prepared in Example 5. It can be seen from the figure that the synergistic effect of high entropy brazing filler metal and metal foam can also achieve the effect of niobium-based high-temperature alloy and SiC f Brazing connection of SiC composite materials.

[0059] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for regulating SiC f The method for strengthening the toughness of a heterogeneous brazing joint of a SiC composite material is characterized in that: The structure of high entropy brazing filler metal foam and high entropy brazing filler metal foam is used to braze SiC f Brazing of heterogeneous joints of / SiC composite materials; The high entropy solder is composed of Co, V, Pd, Ta and Cr, wherein the mass percentage of each element is 18-25%; The metal foam is a metal matrix foam with a three-dimensional structure, and the metal foam is based on Ti or Mo.

2. A method for regulating SiC according to claim 1 f The method for strengthening the toughness of a heterogeneous brazing joint of a SiC composite material is characterized in that: The high entropy solder is a foil with a thickness of 50-100 μm.

3. A method of regulating SiC according to claim 2 f The method for strengthening the toughness of a heterogeneous brazing joint of a SiC composite material is characterized in that: The high entropy solder is a foil with a thickness of 50 μm.

4. A method of regulating SiC according to claim 1 f The method for strengthening the toughness of a heterogeneous brazing joint of a SiC composite material is characterized in that: The SiC f The SiC / SiC composite material is composed of a continuous silicon carbide fiber reinforced silicon carbide matrix, and its structure is any one of 2D, 2.5D and 3D weaving.

5. A method for regulating SiC according to claim 1 f The method for strengthening the toughness of a heterogeneous brazing joint of a SiC composite material is characterized in that: The thickness of the metal foam is no more than 1 mm, and the porosity is no less than 90%.

6. A method for regulating SiC according to claim 1 f The method for strengthening the toughness of a heterogeneous brazing joint of a SiC composite material is characterized in that: The brazing conditions are: vacuum degree of 3-6×10 -3 Pa, brazing temperature is 1100-1200℃, and holding time is 20min.

7. A method for regulating SiC according to claim 1 f The method for strengthening the toughness of a heterogeneous brazing joint of a SiC composite material is characterized in that: The specific steps of the method are: SiC f / SiC composite materials, high temperature alloys, high entropy brazing filler metals and metal foams are cleaned from top to bottom according to the SiC f The / SiC composite material, high entropy brazing filler metal, metal foam, high entropy brazing filler metal and high temperature alloy are assembled in sequence and brazed.

8. A method for regulating SiC according to claim 7 f The method for strengthening the toughness of a heterogeneous brazing joint of a SiC composite material is characterized in that: The SiC f The surfaces to be welded of the SiC / SiC composite material and the high-temperature alloy need to be flattened.

Images