CMASZ-SiC composite glass brazing filler metal as well as preparation method and application thereof

Abstract

The invention relates to the technical field of non-oxide ceramic connection, in particular to CMASZ-SiC composite glass brazing filler metal and a preparation method and application thereof. The CMASZ-SiC composite glass brazing filler metal is prepared from the following components in percentage by mass: 85 percent to 95 percent of Ca-Mg-Al-Si-Zr-O glass powder and the balance of SiC particles. According to the composite glass brazing filler metal, the problem of joint quality caused by brittle phases generated on a brazing interface and mismatching of thermal expansion coefficients of the brazing filler metal and a base material in the process of connecting silicon carbide ceramics through traditional brazing filler metal is solved, and the SiC particles are added into the composite glass brazing filler metal to serve as a strengthening phase, so that the connecting strength of a silicon carbide ceramic brazed joint is further improved. The CMASZ-SiC composite glass brazing filler metal used in the invention has the advantages of good compatibility with silicon carbide ceramic, low joint defect rate and excellent connection quality, and can be applied to the high-temperature-resistant fields of aerospace, nuclear industry, equipment manufacturing industry and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of non-oxide ceramic joining, and particularly to a CMASZ-SiC composite glass solder and a preparation method and application thereof. Background Art

[0002] Silicon carbide (SiC) is widely used in extreme environments such as high temperature, high pressure, and strong irradiation in petrochemical industry, nuclear reactors, aerospace, etc. due to its excellent high-temperature mechanical properties, oxidation resistance, wear and corrosion resistance, and radiation resistance. However, due to the high hardness, high elastic modulus, and large brittleness of silicon carbide ceramics, it is difficult to directly process and form complex-shaped or large-sized silicon carbide components. Therefore, a joining technology suitable for silicon carbide ceramics is required to achieve the manufacture of complex structures.

[0003] Currently, the joining methods of SiC ceramics mainly include mechanical joining, diffusion welding, brazing, precursor joining, C-Si reaction joining, and MAX phase joining, etc. Mechanical joining has a simple design, but has problems such as poor sealing, low reliability, and large passive mass, and it is difficult to meet the requirements of harsh environments. Diffusion welding realizes joining through atomic layer diffusion and can obtain high-strength joints, but it requires extremely high temperatures (usually exceeding 1800 °C), pressures, and long holding times, and it is difficult to be applied to the joining of complex structures. Although precursor joining and C-Si reaction joining can obtain a SiC joining layer with a thermal expansion coefficient matching that of the base material, pores are easily generated during the joining process, resulting in poor joint densification, reduced strength and sealing performance. MAX phase materials (such as Ti 3 SiC 2 ) have a thermal expansion coefficient similar to that of SiC and excellent high-temperature properties, but their joining process usually requires high temperature and high pressure, and pores are easily formed, making it difficult to be applied to the joining of complex structures. Brazing does not need to be carried out under pressure conditions and has simple process conditions, and it is currently a widely used joining method.

[0004] In the brazing of silicon carbide ceramics, mainly metal solders (such as Ag-Cu-Ti) are widely used. However, at high temperatures, metal solders are prone to chemical reactions with silicon carbide to form brittle phases, reducing the high-temperature tissue stability and mechanical properties of the joints. In addition, the thermal expansion coefficient difference between metal solders and silicon carbide is relatively large, which easily generates large residual stresses, resulting in joint cracking. At the same time, the high-temperature activity of metal solders requires the brazing environment to be a vacuum or inert gas atmosphere, which limits the size and structure of the joined parts. Summary of the Invention

[0005] When traditional solders are used for brazing silicon carbide ceramics, there are significant differences in the coefficient of thermal expansion, which easily form interface defects. Therefore, the present invention provides a CMASZ-SiC composite glass solder for brazing silicon carbide ceramics, aiming to improve the compatibility and connectivity between silicon carbide ceramics and the solder during the connection process, and enhance the performance of the brazed joint of silicon carbide ceramic materials.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] One of the technical solutions of the present invention is a CMASZ-SiC composite glass solder, which, by mass percentage, includes 85% - 95% of Ca-Mg-Al-Si-Zr-O glass powder and the balance of SiC particles;

[0008] By mass percentage, the Ca-Mg-Al-Si-Zr-O glass powder is obtained by mixing 20% - 30% of CaO, 10% - 20% of MgO, 10% - 20% of Al 2 O 3 , 45% - 55% of SiO 2 and 5% - 15% of ZrO 2 , followed by ball milling, calcination, and water quenching.

[0009] Another technical solution of the present invention is a preparation method of the above CMASZ-SiC composite glass solder, which mixes the Ca-Mg-Al-Si-Zr-O glass powder and SiC particles by mass percentage and performs ball milling to obtain the CMASZ-SiC composite glass solder.

[0010] A further technical solution of the present invention is the application of the above CMASZ-SiC composite glass solder in brazing silicon carbide ceramics.

[0011] Yet another technical solution of the present invention is a brazing method for silicon carbide ceramics, which includes the following steps:

[0012] Pretreat the surface of the silicon carbide ceramic, and then coat the above CMASZ-SiC composite glass solder on the pretreated surface; bring the silicon carbide ceramic coated with the CMASZ-SiC composite glass solder into contact and assemble it with the silicon carbide ceramic whose surface has been pretreated, and then perform vacuum brazing to obtain a brazed joint.

[0013] The present invention discloses the following technical effects:

[0014] The composite glass solder of the present invention has good wettability on the surface of silicon carbide ceramics, melts to form a liquid phase at the connection temperature, and has good chemical compatibility with silicon carbide ceramics. The composite glass solder of the present invention spreads in the liquid phase state and uniformly fills the connection area, and the good diffusion occurring between the composite glass solder and silicon carbide ceramics helps to form a high-quality connection joint.

[0015] The composite glass solder of the present invention has a similar coefficient of thermal expansion to that of silicon carbide ceramics, avoiding the failure at the brazed joint caused by a large difference in the coefficient of thermal expansion. The SiC particles added to the composite glass solder further improve the coefficient of thermal expansion while diffusing and connecting with the silicon carbide ceramic substrate, enhancing the mechanical properties of the brazed joint.

[0016] Compared with metal solders, the composite glass solder of the present invention has more stable chemical properties, strong antioxidant performance, the weight gain of the joint after welding is less than 0.5%, and it has a longer service life, having the value of further popularization and application. Description of the Drawings

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0018] Figure 1 It is a schematic assembly diagram of the silicon carbide ceramic brazed joint of the present invention.

[0019] Figure 2 It is a physical diagram of the silicon carbide ceramic brazed joint in Embodiment 1 of the present invention.

[0020] Figure 3 It is the SEM morphology of the CMASZ-SiC composite glass solder obtained in Embodiment 1 of the present invention.

[0021] Figure 4 It is the SEM morphology of the silicon carbide ceramic brazed joint obtained in Embodiment 1 of the present invention. Detailed Embodiments

[0022] Now, various exemplary embodiments of the present invention will be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, characteristics, and implementation schemes of the present invention.

[0023] It should be understood that the terms described in the present invention are only for describing specific embodiments and are not used to limit the present invention. In addition, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded from the range.

[0024] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Although this invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of this invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0025] Without departing from the scope or spirit of this invention, various modifications and variations can be made to the specific embodiments of the description of this invention, which are obvious to those skilled in the art. Other embodiments obtained from the description of this invention are obvious to those skilled in the art. The description of this invention and the examples are merely exemplary.

[0026] Regarding "comprising", "including", "having", "containing", etc. used herein, they are all open-ended terms, meaning including but not limited to.

[0027] The first aspect of this invention provides a CMASZ-SiC composite glass solder, which, by mass percentage, comprises 85% - 95% of Ca-Mg-Al-Si-Zr-O glass powder and the balance of SiC particles;

[0028] By mass percentage, the Ca-Mg-Al-Si-Zr-O glass powder is obtained by mixing 20% - 30% of CaO, 10% - 20% of MgO, 10% - 20% of Al 2 O 3 , 45% - 55% of SiO 2 and 5% - 15% of ZrO 2 , followed by ball milling, calcination, and water quenching.

[0029] The particle sizes of the CaO, MgO, Al 2 O 3 , SiO 2 , ZrO 2 are all 10 - 30 μm.

[0030] In a preferred embodiment of this invention, the temperature of the calcination is 1400 - 1500 °C and the time is 4 - 6 h.

[0031] The rotation speed of the ball milling is 300 - 500 r / min, the ball-to-material ratio is 5 - 10:1, and the time is 8 - 10 h.

[0032] Before the calcination, it further includes the step of drying the powder obtained by ball milling.

[0033] The water quenching is carried out using deionized water; after the water quenching, the steps also include crushing and ball milling the glass blocks obtained by water quenching.

[0034] In the second aspect of the present invention, a method for preparing the above-mentioned CMASZ-SiC composite glass filler metal is provided. The Ca-Mg-Al-Si-Zr-O glass powder and SiC particles are mixed and ball milled by mass percentage to obtain the CMASZ-SiC composite glass filler metal.

[0035] In a preferred embodiment of the present invention, the particle size of the Ca-Mg-Al-Si-Zr-O glass powder is 10 - 30 μm; the particle size of the SiC particles is 10 - 30 μm; the particle size of the CMASZ-SiC composite glass filler metal is 10 - 30 μm.

[0036] In a preferred embodiment of the present invention, the medium for ball milling is corundum, the solvent is absolute ethanol, the ball-to-material ratio is 5:1, the rotation speed is 250 - 400 r / min, and the ball milling time is 3 - 6 h.

[0037] In a specific embodiment of the present invention, during ball milling, the solid-liquid ratio (i.e., Ca-Mg-Al-Si-Zr-O glass powder + SiC particles: solvent) is 1 g:1 mL.

[0038] In the third aspect of the present invention, the application of the above-mentioned CMASZ-SiC composite glass filler metal in the brazing of silicon carbide ceramics is provided.

[0039] In the fourth aspect of the present invention, a brazing method for silicon carbide ceramics is provided, including the following steps:

[0040] The surface of the silicon carbide ceramic is pretreated, and then the above-mentioned CMASZ-SiC composite glass filler metal is coated on the pretreated surface; the silicon carbide ceramic coated with the CMASZ-SiC composite glass filler metal is brought into contact and assembled with the silicon carbide ceramic whose surface has been pretreated, and then vacuum brazing is carried out to obtain a brazed joint.

[0041] In a preferred embodiment of the present invention, the conditions of the vacuum brazing are set as follows: the vacuum degree is 1×10 -4 ~1×10 -2 Pa, heated at a rate of 10 °C / min to 1250 - 1400 °C and held for 1 - 2 h, then cooled at a rate of 5 °C / min to 500 °C, and then cooled with the furnace.

[0042] In a preferred embodiment of the present invention, the pretreatment is specifically carried out by polishing successively with 400-mesh, 600-mesh, 800-mesh, 1000-mesh, and 1500-mesh sandpapers, and then using 3-μm and 1.5-μm diamond suspensions for polishing treatment.

[0043] The intermediate layer of the brazed joint prepared by the method of the present invention has no crack defects. The silicon carbide particles and the silicon carbide ceramic diffuse into each other and are partially connected, improving the connection quality, and its shear strength can reach 90 - 110 MPa.

[0044] Calculated according to the volume fraction of the intermediate layer of the brazed joint prepared by the method of the present invention being 100%, the intermediate layer contains 60% - 70% glass phase matrix, 15% - 25% silicon carbide particles, and 10% - 20% crystal phase; within this proportion range, it is beneficial to maintain the joint strength.

[0045] The present invention provides a novel composite glass filler metal to achieve the brazing connection of silicon carbide ceramics. The filler metal has a thermal expansion coefficient close to that of silicon carbide material, good wettability, and good interfacial compatibility with silicon carbide. The obtained silicon carbide brazed joint has small residual stress and high connection quality.

[0046] The composite glass filler metal of the present invention solves the joint quality problems caused by the generation of brittle phases at the brazing interface and the mismatch between the thermal expansion coefficients of the filler metal and the base material during the connection of silicon carbide ceramics by traditional filler metals. The addition of SiC particles in the composite glass filler metal as a strengthening phase further improves the connection strength of the silicon carbide ceramic brazed joint. The CMASZ - SiC composite glass filler metal used in the present invention has good compatibility with silicon carbide ceramics, a low joint defect rate, and excellent connection quality, and can be applied to high - temperature fields such as aerospace, nuclear industry, and equipment manufacturing.

[0047] Unless otherwise specified, the technical means used in the embodiments of the present invention are conventional means well known to those skilled in the art. Unless otherwise stated, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in the art.

[0048] The particle size of SiC used in the embodiments of the present invention is 10 - 30 μm.

[0049] The test method involved in the present invention is the shear mechanical property test, and the reference standard is GJB 10311 - 2021.

[0050] The technical solutions provided by the present invention will be described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0051] Example 1

[0052] CaO with a mass percentage ratio of 20%, MgO with a mass percentage ratio of 10%, Al 2 O 3 with a mass percentage ratio of 20%, SiO 2 with a mass percentage ratio of 45%, ZrO 2Ball milling and mixing were carried out in a planetary ball mill for 8 h at a rotational speed of 300 r / min. The ball milling medium was corundum, the solvent was absolute ethanol, and the ball-to-material ratio was 10:1. After ball milling, it was dried in a forced-air drying oven at 70 °C for 2 h. The dried mixed powder was placed in an alumina crucible and put into a muffle furnace. Under the conditions of an air atmosphere and a temperature of 1400 °C, it was held for 4 h, taken out and poured into deionized water to obtain a transparent and colorless glass block; the obtained glass block was crushed and ball milled, and after sieving, Ca-Mg-Al-Si-Zr-O glass powder (abbreviation: CMASZ glass) with a particle size of 10 - 30 μm was obtained.

[0053] 90 wt% of CMASZ glass and 10 wt% of SiC were placed in a planetary ball mill for ball milling and mixing for 4 h at a rotational speed of 250 r / min. The ball milling medium was corundum, the solvent was absolute ethanol, the solid-to-liquid ratio was 1 g:1 mL, and the ball-to-material ratio was 5:1. After ball milling, it was taken out to obtain a filler metal suspension. A part of the filler metal suspension was dried, and the thermal expansion coefficient of the CMASZ-SiC composite glass filler metal was measured to be 5.2×10 -6 / °C. The SEM morphology of the dried powder of CMASZ-SiC composite glass filler metal is as Figure 3 shown, and it can be seen from Figure 3 that the components in the powder are evenly mixed.

[0054] The size of the silicon carbide ceramic was 15 mm × 15 mm × 3 mm, and the surface to be treated was 15 mm × 15 mm. After being polished with 400-mesh, 600-mesh, 800-mesh, 1000-mesh, and 1500-mesh sandpapers, it was polished with 3-μm and 1.5-μm diamond suspensions. The filler metal suspension was evenly coated on the pretreated surface of the silicon carbide ceramic. After it was dried, it was coated again and dried. The coating amount each time was 1 mL to ensure that the filler metal was evenly distributed on the surface of the silicon carbide ceramic. Then, the silicon carbide ceramic coated with CMASZ-SiC composite glass filler metal was assembled in contact with the silicon carbide ceramic whose surface had been pretreated.

[0055] The assembled workpiece to be welded was put into a vacuum tube furnace for vacuum brazing. The specific process of vacuum brazing was that the vacuum degree in the vacuum furnace was 1×10 -3 Pa. No additional pressure was applied during the welding process. It was heated to 1350 °C at a rate of 10 °C / min and held for 1 h, then cooled to 500 °C at a rate of 5 °C / min, and then cooled with the furnace to obtain a brazed joint (the assembly schematic diagram is as Figure 1 shown). The physical diagram of the brazed joint of this silicon carbide ceramic is as Figure 2 shown, and it can be seen from Figure 2 that the wetting and spreading performance of the filler metal on the contact surface is good, the overall thickness of the joint is uniform, and the appearance is flat and defect-free; the SEM morphology of this brazed joint is asFigure 4 As shown by Figure 4 it can be seen that the connection at the joint interface is good, the filler metal diffuses moderately into the SiC matrix, and the crystal phase and silicon carbide phase in the joint intermediate layer are evenly distributed.

[0056] Taking the volume fraction of the intermediate layer of the brazed joint as 100%, glass phase: silicon carbide particles: crystal phase = 69.3:17.5:13.2. The strength of the brazed joint is 96.45 MPa.

[0057] Example 2

[0058] CaO with a mass percentage ratio of 25%, MgO with 10%, Al 2 O 3 , SiO with 45% 2 , and ZrO with 5% 2 were placed in a planetary ball mill for ball milling and mixing. The ball milling time was 8 h, the rotational speed of the ball mill was 500 r / min, the ball milling medium was corundum, the solvent was absolute ethanol, and the ball-to-material ratio was 10:1. After ball milling, it was dried in a blast drying oven at 70 °C for 2 h. The dried mixed powder was placed in an alumina crucible and put into a muffle furnace. Under the conditions of air atmosphere and a temperature of 1500 °C, it was held for 4 h, taken out and poured into deionized water to obtain a transparent and colorless glass block; the obtained glass block was crushed and ball milled, and after sieving, Ca-Mg-Al-Si-Zr-O glass powder was obtained.

[0059] 95% of CMASZ glass and 5% of SiC by mass percentage were placed in a planetary ball mill for ball milling and mixing. The ball milling time was 4 h, the rotational speed of the ball mill was 250 r / min, the ball milling medium was corundum, the solvent was absolute ethanol, the solid-liquid ratio was 1 g:1 mL, and the ball-to-material ratio was 5:1. After mixing evenly, it was taken out to obtain a filler metal suspension. After drying a part of the filler metal suspension, the thermal expansion coefficient of the CMASZ-SiC composite glass filler metal was measured to be 5.4×10 -6 / °C.

[0060] The size of the silicon carbide ceramic was 15 mm×15 mm×3 mm, and the surface to be treated was 15 mm×15 mm. After being polished with 400-mesh, 600-mesh, 800-mesh, 1000-mesh, and 1500-mesh sandpapers, it was polished with 3-μm and 1.5-μm diamond suspensions. The filler metal suspension was evenly coated on the pretreated surface of the silicon carbide ceramic. After drying, it was coated again and dried. The coating amount each time was 1 mL to ensure that the filler metal was evenly distributed on the surface of the silicon carbide ceramic. Then, the silicon carbide ceramic coated with the CMASZ-SiC composite glass filler metal was contacted and assembled with the silicon carbide ceramic whose surface had been pretreated.

[0061] Put the assembled workpiece to be welded into a vacuum tube furnace for vacuum brazing. The specific process of vacuum brazing is as follows: the vacuum degree in the vacuum furnace is 1×10 -3 Pa, no additional pressure is applied during the welding process, the temperature is raised to 1250 °C at a rate of 10 °C / min and held for 2 h, then cooled to 500 °C at a rate of 5 °C / min, and then cooled with the furnace to obtain a brazed joint.

[0062] In the middle layer of the brazed joint, taking the volume fraction as 100%, the glass phase: silicon carbide particles: crystal phase = 63.1:22.8:14.1. The strength of the brazed joint is 95.30 MPa.

[0063] Example 3

[0064] Put CaO with a mass percentage ratio of 30%, MgO with 10%, Al 2 O 3 , SiO with 45% 2 , and ZrO with 5% 2 into a planetary ball mill for ball milling and mixing. The ball milling time is 8 h, the rotation speed of the ball mill is 500 r / min, the ball milling medium is corundum, the solvent is anhydrous ethanol, and the ball-to-material ratio is 10:1. After ball milling, dry in a blast drying oven at 70 °C for 2 h. Put the dried mixed powder into an alumina crucible and place it in a muffle furnace. Under the conditions of air atmosphere and a temperature of 1400 °C, hold for 6 h, take out and pour into deionized water to obtain a transparent and colorless glass block; crush and ball mill the obtained glass block, and sieve to obtain Ca-Mg-Al-Si-Zr-O glass powder.

[0065] Put CMASZ glass with a mass percentage of 85% and 15% of SiC into a planetary ball mill for ball milling and mixing. The ball milling time is 4 h, the rotation speed of the ball mill is 250 r / min, the ball milling medium is corundum, the solvent is anhydrous ethanol, the solid-liquid ratio is 1 g:1 mL, and the ball-to-material ratio is 5:1. After mixing evenly, take out to obtain a solder suspension. Take a part of the solder suspension and dry it, and the thermal expansion coefficient of the CMASZ-SiC composite glass solder is measured to be 5.0×10 -6 / °C.

[0066] The size of the silicon carbide ceramic is 15 mm×15 mm×3 mm, and the surface to be treated is 15 mm×15 mm. After being polished with 400-mesh, 600-mesh, 800-mesh, 1000-mesh, and 1500-mesh sandpapers, it is polished with 3-μm and 1.5-μm diamond suspensions. Evenly coat the solder suspension on the pretreated surface of the silicon carbide ceramic. After drying, repeat the coating once and dry. The coating amount each time is 1 mL to ensure that the solder is evenly distributed on the surface of the silicon carbide ceramic. Then, contact and assemble the silicon carbide ceramic coated with CMASZ-SiC composite glass solder with the silicon carbide ceramic whose surface has been pretreated.

[0067] Place the assembled parts to be welded into a vacuum tube furnace for vacuum brazing. The specific process of vacuum brazing is as follows: the vacuum degree in the vacuum furnace is 1×10 -2 Pa, no additional pressure is applied during the welding process, heat up to 1250°C at a rate of 10°C / min and hold for 2 h, then cool down to 500°C at a rate of 5°C / min, and then cool with the furnace to obtain a brazed joint.

[0068] Regarding the intermediate layer of the brazed joint by volume fraction of 100%, glass phase: silicon carbide particles: crystal phase = 61.4:21.6:17.0. The strength of the brazed joint is 91.02 MPa.

[0069] Example 4

[0070] Put CaO with a mass percentage ratio of 20%, MgO with 10%, Al 2 O 3 , SiO with 50% 2 , and ZrO with 10% 2 in a planetary ball mill for ball milling and mixing. The ball milling time is 8 h, the rotational speed of the ball mill is 400 r / min, the ball milling medium is corundum, the solvent is absolute ethanol, and the ball-to-material ratio is 10:1. After ball milling, dry at 70°C for 2 h in a blast drying oven. Place the dried mixed powder in an alumina crucible and put it into a muffle furnace. Under the conditions of air atmosphere and a temperature of 1500°C, hold for 4 h, take out and pour it into deionized water to obtain a transparent and colorless glass block; crush and ball mill the obtained glass block, and obtain Ca-Mg-Al-Si-Zr-O glass powder after sieving.

[0071] Put CMASZ glass with a mass percentage of 90% and SiC with 10% in a planetary ball mill for ball milling and mixing. The ball milling time is 3 h, the rotational speed of the ball mill is 300 r / min, the ball milling medium is corundum, the solvent is absolute ethanol, the solid-liquid ratio is 1 g:1 mL, and the ball-to-material ratio is 5:1. After mixing evenly, take it out to obtain a solder suspension. Take a part of the solder suspension and dry it, and measure that the thermal expansion coefficient of the CMASZ-SiC composite glass solder is 4.9×10 -6 / °C.

[0072] The size of the silicon carbide ceramic is 15 mm × 15 mm × 3 mm, and the surface to be treated is 15 mm × 15 mm. After being polished with 400-mesh, 600-mesh, 800-mesh, 1000-mesh, and 1500-mesh sandpapers, it is polished with 3-μm and 1.5-μm diamond suspensions. The solder suspension is evenly coated on the pretreated surface of the silicon carbide ceramic. After it dries, it is coated again and dried. The coating amount each time is 1 mL to ensure that the solder is evenly distributed on the surface of the silicon carbide ceramic. Then, the silicon carbide ceramic coated with the CMASZ-SiC composite glass solder is contacted and assembled with the silicon carbide ceramic whose surface has been pretreated.

[0073] The assembled workpiece to be welded is placed in a vacuum tube furnace for vacuum brazing. The specific process of vacuum brazing is that the vacuum degree in the vacuum furnace is 1×10 -2 Pa. No additional pressure is applied during the welding process. It is heated to 1400 °C at a rate of 10 °C / min and held for 1 h, then cooled to 500 °C at a rate of 5 °C / min, and then cooled with the furnace to obtain a brazed joint.

[0074] Regarding the intermediate layer of the brazed joint, calculated by volume fraction of 100%, glass phase: silicon carbide particles: crystal phase = 66.7:15.4:17.9. The strength of the brazed joint is 98.19 MPa.

[0075] Example 5

[0076] 20% CaO, 10% MgO, 10% Al2O3, 55% SiO2, and 5% ZrO2 by mass percentage are placed in a planetary ball mill for ball milling and mixing. The ball milling time is 8 h, the rotational speed of the ball mill is 500 r / min, the ball milling medium is corundum, the solvent is anhydrous ethanol, and the ball-to-material ratio is 10:1. After ball milling, it is dried in a blast drying oven at 70 °C for 2 h. The dried mixed powder is placed in an alumina crucible and put into a muffle furnace. Under the conditions of air atmosphere and a temperature of 1500 °C, it is held for 6 h, taken out and poured into deionized water to obtain a transparent and colorless glass block; the obtained glass block is broken and ball milled, and after sieving, Ca-Mg-Al-Si-Zr-O glass powder is obtained.

[0077] 95% CMASZ glass and 5% SiC by mass percentage are placed in a planetary ball mill for ball milling and mixing. The ball milling time is 3 h, the rotational speed of the ball mill is 300 r / min, the ball milling medium is corundum, the solvent is anhydrous ethanol, the solid-liquid ratio is 1 g:1 mL, and the ball-to-material ratio is 10:1. After mixing evenly, it is taken out to obtain a solder suspension. After drying a part of the solder suspension, the thermal expansion coefficient of the CMASZ-SiC composite glass solder is measured to be 4.7×10 -6 / °C.

[0078] The size of the silicon carbide ceramic is 15 mm × 15 mm × 3 mm, and the surface to be treated is 15 mm × 15 mm. After being polished with 400-mesh, 600-mesh, 800-mesh, 1000-mesh, and 1500-mesh sandpapers, it is polished with 3-μm and 1.5-μm diamond suspensions. The solder suspension is evenly coated on the pretreated surface of the silicon carbide ceramic. After it dries, it is coated again and dried. The coating amount each time is 1 mL to ensure that the solder is evenly distributed on the surface of the silicon carbide ceramic. Then, the silicon carbide ceramic coated with the CMASZ-SiC composite glass solder is contacted and assembled with the silicon carbide ceramic whose surface has been pretreated.

[0079] The assembled workpiece to be welded is placed in a vacuum tube furnace for vacuum brazing. The specific process of vacuum brazing is that the vacuum degree in the vacuum furnace is 1×10 -3 Pa. No additional pressure is applied during the welding process. It is heated to 1350 °C at a rate of 10 °C / min and held for 1.5 h, then cooled to 500 °C at a rate of 5 °C / min, and then cooled with the furnace to obtain a brazed joint.

[0080] In the intermediate layer of the brazed joint, calculated by volume fraction of 100%, glass phase: silicon carbide particles: crystal phase = 67.3:18.1:14.6. The strength of the brazed joint is 97.33 MPa.

[0081] Comparative Example 1

[0082] The difference from Example 1 is only that ZrO 2 is replaced with TiO of the same mass percentage 2 ; the remaining steps and parameters are the same as those in Example 1.

[0083] The results show that the strength of the brazed joint obtained in Comparative Example 1 is 44.21 MPa.

[0084] The above-described embodiments are only descriptions of the preferred embodiments of the present invention and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A CMASZ-SiC composite glass solder, characterized in that: Calculated by mass percentage, it includes 85% to 95% of Ca-Mg-Al-Si-Zr-O glass powder and the remainder of SiC particles; Calculated by mass percentage, the Ca-Mg-Al-Si-Zr-O glass powder is prepared by mixing 20% ​​to 30% CaO, 10% to 20% MgO, 10% to 20% Al2O3, 45% to 55% SiO2 and 5% to 15% ZrO2, ball milling the mixture, and then calcining and water quenching.

2. The CMASZ-SiC composite glass solder according to claim 1, characterized in that: The calcination temperature is 1400-1500° C. and the calcination time is 4-6 hours.

3. A method for preparing the CMASZ-SiC composite glass solder according to claim 1, characterized in that: The Ca-Mg-Al-Si-Zr-O glass powder and SiC particles are mixed and ball-milled according to mass percentage to obtain the CMASZ-SiC composite glass solder.

4. The method for preparing the CMASZ-SiC composite glass solder according to claim 3, characterized in that: The particle size of the Ca-Mg-Al-Si-Zr-O glass powder is 10 to 30 μm; the particle size of the SiC particles is 10 to 30 μm; and the particle size of the CMASZ-SiC composite glass solder is 10 to 30 μm.

5. The method for preparing the CMASZ-SiC composite glass solder according to claim 3, characterized in that: The medium of the ball mill is corundum, and the solvent is anhydrous ethanol.

6. Use of the CMASZ-SiC composite glass solder as claimed in claim 1 or 2 in brazing of silicon carbide ceramics.

7. A method for brazing silicon carbide ceramics, characterized in that: The following steps are involved: The surface of the silicon carbide ceramic is pretreated, and then the CMASZ-SiC composite glass brazing material according to claim 1 or 2 is coated on the pretreated surface; the silicon carbide ceramic surface coated with the CMASZ-SiC composite glass brazing material is contacted and assembled with the silicon carbide ceramic surface whose surface has been pretreated, and then vacuum brazing is performed to obtain a brazed joint.

8. The brazing method of silicon carbide ceramics according to claim 7, characterized in that: The vacuum brazing conditions are set as follows: the vacuum degree is 1×10 -4 ~1×10 -2 Pa, heat up to 1250-1400℃ at a rate of 10℃ / min and keep it for 1-2h, then cool down to 500℃ at a rate of 5℃ / min, and then cool with the furnace.

9. The method for brazing silicon carbide ceramics according to claim 7, characterized in that: The pretreatment specifically includes grinding with 400 mesh, 600 mesh, 800 mesh, 1000 mesh and 1500 mesh sandpaper in sequence, and then polishing with 3 μm and 1.5 μm diamond suspension.

10. The method for brazing silicon carbide ceramics according to claim 7, characterized in that: Calculated by volume percentage, the intermediate layer of the brazed joint comprises 60% to 70% of glass phase, 15% to 25% of silicon carbide, and 10% to 20% of crystal phase.

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