A method of brazing silicon carbide ceramic to nickel-based superalloy
By using a layered structure and a high-entropy alloy solder with specific composition and an intermediate layer design, a high-temperature reliable connection between SiC ceramics and nickel-based superalloys is achieved, solving the problem of mismatch between wettability and thermal expansion coefficient, improving connection strength and reliability, and making it suitable for multiple engineering applications.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- BEIJING UNIV OF TECH
- Filing Date
- 2023-05-23
- Publication Date
- 2026-07-21
AI Technical Summary
The reliable bonding of SiC ceramics and nickel-based superalloys at high temperatures is difficult, mainly due to problems such as poor wettability, mismatch in thermal expansion coefficients, and easy formation of intermetallic compounds at the interface, which leads to bonding difficulties.
A layered structure material is adopted, using CoCrNi medium-entropy alloy as a hard intermediate layer and pure Ni as a soft intermediate layer, combined with a high-entropy alloy solder with a specific composition. By controlling the element content, a Ni-free solder is designed, the interface reaction is controlled, and the multi-layer structure is subjected to high-temperature treatment in a vacuum brazing furnace.
A high-strength connection between SiC ceramics and nickel-based superalloys has been achieved, with a shear strength of 90 MPa at room temperature and 33.2 MPa at 400℃. This solves the problem of connection reliability at high temperatures and is suitable for aerospace, nuclear energy, machinery, petroleum, optics, integrated circuit and other fields.
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Abstract
Description
Technical Field
[0001] This invention relates to a brazing method for SiC ceramics and nickel-based high-temperature alloys and a high-entropy alloy brazing filler metal, belonging to the field of high-temperature brazing of dissimilar materials. Background Technology
[0002] Silicon carbide (SiC) ceramics possess excellent properties such as high high-temperature strength, good wear resistance, excellent thermal stability, low coefficient of thermal expansion (CTE), high hardness, and superior thermal shock resistance. The brazing joints of SiC components with metals or metal-based composite materials are widely used in aerospace, nuclear energy, machinery, petroleum, optics, and integrated circuit fields. However, due to the difficulty in wetting the surface of SiC ceramics with brazing filler metal, significant differences in physical properties compared to metals, mismatched coefficients of thermal expansion, and the tendency for the formation of numerous intermetallic compounds at the interface, achieving reliable bonding between SiC and nickel-based superalloys at high temperatures is extremely difficult. Therefore, designing a high-temperature brazing method and material that can effectively wet the ceramic interface at 1100-1200℃ without causing severe reactions is of great significance for promoting its engineering applications in aerospace and other related fields. Summary of the Invention:
[0003] This invention provides a method for brazing silicon carbide ceramics to high-temperature alloys and the materials used for intermediate brazing. Different layered structural materials are used, based on the first transition element in the fourth period of the periodic table, with the addition of active elements such as Ti. CoCrNi medium-entropy alloy and pure Ni are selected as hard and soft intermediate layers to relieve residual stress, respectively, and added to the high-entropy alloy brazing filler metal.
[0004] A brazing method for silicon carbide ceramics and high-temperature alloys includes the following steps:
[0005] Step 1: Prepare foils from the materials used for intermediate brazing: high-entropy alloy brazing filler metal, pure Ni, and CoCrNi medium-entropy alloy; grind the surfaces of silicon carbide ceramic and nickel-based high-temperature alloy. Since SiC ceramic has a very high hardness, use the rollers of a rolling mill to grind the surface. Then, ultrasonically clean the sheet-like high-entropy alloy brazing filler metal, pure Ni sheet, and sheet-like CoCrNi medium-entropy alloy.
[0006] Step 2: Bond the sheet-like high-entropy alloy solder, pure Ni sheet, and sheet-like CoCrNi medium-entropy alloy between the silicon carbide ceramic and the nickel-based superalloy using an adhesive. The final order is as follows: nickel-based superalloy, sheet-like high-entropy alloy solder, pure Ni sheet, sheet-like high-entropy alloy solder, sheet-like CoCrNi medium-entropy alloy, sheet-like high-entropy alloy solder, silicon carbide ceramic.
[0007] Step 3: Place the above multi-layer structure in a high-temperature brazing furnace. To prevent the brazing filler metal from evaporating during high-temperature brazing and to ensure the atmosphere, use two Al2O3 ceramic vessels to encase the multi-layer structure. Seal the contact gap between the vessels by embedding Al2O3 ceramic particles with a diameter of 0.5mm-1mm.
[0008] Step 4: Heat in a vacuum brazing furnace, first to 400℃ and hold for 10-20 minutes, with a heating rate of 4.5℃-6℃ / min; then continue heating to 800℃ and hold at 800℃ for 20-30 minutes, with a heating rate of 4.5℃-6℃ / min; then continue heating to 1120℃ and hold for 23-37 minutes, with a heating rate of 4.5℃-6℃ / min; then cool down to 400℃, with a cooling rate of 4.5℃-6℃ / min, and then allow the furnace to cool naturally; after brazing, the high-entropy alloy filler metal, pure Ni, and CoCrNi medium-entropy alloy still maintain their original layered structure.
[0009] Each layer of high-entropy alloy solder sheet has a thickness of 0.08-0.1 mm and a composition of: 27-35 at% Cu, 27-35 at% Mn, 8-12 at% Cr, 9-12 at% Co, 6-11 at% Fe, and 3-7 at% Ti; the sheet-like CoCrNi medium-entropy alloy has a thickness of 0.15-0.2 mm and a composition of: 34-35 at% Co, 33-35 at% Ni, and 30-33 at% Cr; the pure Ni sheet has a thickness of 0.15-0.2 mm and a Ni purity greater than 99.9%.
[0010] Layered materials used in brazing have certain application potential in the field of brazing material design due to their high disorder, which can suppress the formation of intermetallic compounds, and the retarded diffusion effect of their random solid solutions. Currently, they are being studied extensively by scholars at home and abroad. However, high-entropy alloys with first transition metal elements such as Co, Cr, Fe, Mn, and Cu as basic components generally have excessively high solid-liquid phase lines. Their complete liquidus temperature is often above 1250℃, and can even reach 1400℃. At this high temperature, problems such as excessive growth of brittle reaction layer compounds in the joint area, large-scale volatilization of high-temperature elements in the alloy base material, coarse metal grains, and decreased mechanical properties due to the dissolution of strengthening phases often occur. Moreover, this brazing temperature has exceeded the normal operating temperature of most conventional brazing furnaces on the market, which undoubtedly limits the application of high-temperature brazing filler metals and the selection range of high-temperature alloy base materials. However, by increasing the content of low melting phases and preparing nanoscale powder brazing filler metals, the melting point of the brazing filler metal can be reduced, and the mixing degree and structural entropy of the brazing filler metal can be removed from the high-entropy range. At this time, scholars at home and abroad have tried to lower the melting point of the solder by introducing additional low-melting-point reducing elements or by adding Ni as one of the main components of the high-entropy alloy. Considering that the dissolution-driven wetting and reactive wetting of Ni on the SiC surface at high temperatures can easily damage SiC and lead to the formation of a large amount of NiSi compounds, this invention, from the perspective of thermodynamics and solidification and crystallization kinetics, has successfully designed a high-entropy alloy solder with a melting point of around 1100℃ that does not contain Ni, without introducing new reducing elements, by reasonably controlling the element content. It contains active elements such as Ti and can effectively achieve the brazing connection between silicon carbide ceramics and nickel-based superalloys. Since this solder does not contain Ni, it is not easy to cause excessive interfacial reaction, and the solder still has good thermal stability at high temperatures.
[0011] Furthermore, the thermal expansion coefficients of nickel-based superalloys and silicon carbide ceramics differ significantly, resulting in severe residual stress during high-temperature thermal cycling. Since ceramics are resistant to compression but not tension, and there are very few movable dislocations in ceramic crystals, dislocation movement is very difficult. Once the yield strength is reached, the ceramics will fracture. At the same time, unlike metals, ceramic crystals have inherent microcracks, and severe stress concentration will occur at the crack tips. Under tension, once the crack reaches the critical size, it will become unstable and propagate, leading to fracture. Therefore, the silicon carbide ceramic matrix has extremely poor tensile stress resistance, and it is impossible to alleviate the residual stress by reducing the size of the nickel-based superalloy base material. Currently, soft or hard materials are generally used as interlayers to absorb some of the strain and alleviate residual stress. This patent proposes using a CoCrNi medium-entropy alloy with a low coefficient of thermal expansion and a high elastic modulus as a hard interlayer and pure Ni as a soft interlayer, forming a double-layer structure. Since the coefficient of thermal expansion of the CoCrNi medium-entropy alloy is between that of silicon carbide ceramics and nickel-based superalloys, and it also has a high elastic modulus, placing the CoCrNi medium-entropy alloy into the brazing filler metal can transfer the residual stress that was originally formed near the surface of the silicon carbide ceramic to the CoCrNi medium-entropy alloy. Meanwhile, the pure Ni on top has already absorbed some of the residual stress through its own plastic deformation. In this way, the residual stress level in the ceramic matrix can be reduced to a relatively low level after brazing.
[0012] Shear tests were conducted on the butt joints of SiC ceramics and high-temperature metals using a universal material testing machine. The shear strength reached 90 MPa at room temperature and 33.2 MPa at 400 degrees Celsius. The joint strength obtained in this application is high, and the interfacial bonding strength between the high-entropy alloy brazing filler and the SiC ceramic matrix is also high. The base material for the connection can be SiC ceramics and nickel-based high-temperature alloys. This application can meet the requirement of brazing SiC ceramics and nickel-based high-temperature alloys at 1100℃. The nickel-based high-temperature alloy can be Inconel alloy, Hastelloy alloy, or Monel alloy. This patent can be used for dissimilar connections of SiC ceramics and nickel-based high-temperature alloys in the energy, petroleum, chemical, aerospace, and aviation fields. Attached image description:
[0013] Figure 1 Stress-strain curves of nickel-based superalloys, high-entropy alloy solders, and pure Ni: (a) Nickel-based superalloys, example: Inconel 718 (b) Pure Ni (c) HEA high-entropy solder
[0014] Figure 2 Schematic diagram of the assembly of base material, brazing filler metal and intermediate layer
[0015] Figure 3 DTA curve of high-entropy solder. Detailed Implementation
[0016] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings, but the present invention is not limited to the following embodiments.
[0017] Example 1
[0018] Step 1: Grind the surface of the base material and the sample. Since SiC ceramics are very hard, use the rollers of the rolling mill to grind the surface. Then, ultrasonically clean the base material, the brazing filler metal and the intermediate layer foil.
[0019] Step 2: Bond the high-entropy alloy solder, pure Ni, and CoCrNi medium-entropy alloy to the ceramic and metal layers respectively using an adhesive. The high-entropy alloy solder, pure Ni, and CoCrNi medium-entropy alloy are all in foil form. The order of placement from the ceramic side to the metal side is as follows: first, add the high-entropy alloy solder sheet to the ceramic surface, then add the CoCrNi medium-entropy alloy, then add the pure Ni intermediate foil layer, and finally add the high-entropy alloy solder. The high-entropy alloy solder composition is: 35 at% Cu, 35 at% Mn, 10 at% Cr, 10 at% Co, 8 at% Fe, 2 at% Ti; the thickness of each high-entropy alloy solder sheet is 0.1 mm; the purity of Ni is 99.99%, and the corresponding thickness is 0.2 mm; the composition of the CoCrNi medium-entropy alloy is: 33.3 at% Co, 33.3 at% Cr, 33.3 at% Ni, with a corresponding thickness of 0.2 mm.
[0020] Step 3: Place the sample in a high-temperature brazing furnace. To prevent the brazing filler metal from evaporating during high-temperature brazing and to ensure the atmosphere, use two Al2O3 ceramic vessels to cover the sample from top to bottom. Seal the contact gap between the vessels by embedding Al2O3 ceramic particles with a diameter of 0.5mm.
[0021] Step 4: Heat in a vacuum brazing furnace. First, heat to 400℃ at a heating rate of 4.5℃ / min, hold for 20 minutes, then continue heating at the same rate, hold at 800℃ for 20 minutes, then continue heating at the same rate to 1120℃ and hold for 27 minutes. Then cool down at a rate of 4.5℃ / min to 400℃, and then furnace cool. After brazing, the high-entropy alloy filler metal, pure Ni, and CoCrNi medium-entropy alloy still exist, maintaining the structure of Step 2.
[0022] A shear test was conducted on a SiC ceramic and Inconel 718 nickel-based superalloy joint brazed by butt joint using a universal testing machine. During the application of load to the joint, the moving speed of the universal testing machine indenter was 0.5 mm / min. The shear strength at room temperature was 92.6 MPa, and the shear strength at 400 degrees Celsius was 29.3 MPa.
[0023] Example 2
[0024] Step 1: Grind the surface of the base material and the sample. Since SiC ceramics are very hard, use the rollers of the rolling mill to grind the surface. Then, ultrasonically clean the base material, the brazing filler metal and the intermediate layer foil.
[0025] Step 2: Bond the high-entropy alloy solder, pure Ni, and CoCrNi medium-entropy alloy to the ceramic and metal layers respectively using an adhesive. The high-entropy alloy solder, pure Ni, and CoCrNi medium-entropy alloy are all in foil form. The order of placement from the ceramic side to the metal side is as follows: first, add the high-entropy alloy solder sheet to the ceramic surface, then add the CoCrNi medium-entropy alloy, then add the pure Ni intermediate foil layer, and finally add the high-entropy alloy solder. The high-entropy alloy solder composition is: 30 at% Cu, 30 at% Mn, 12 at% Cr, 12 at% Co, 10 at% Fe, and 6 at% Ti. The thickness of each high-entropy alloy solder sheet is 0.1 mm. The purity of Ni is 99.99%, and the corresponding thickness is 0.2 mm. The CoCrNi medium-entropy alloy composition is: 33.3 at% Co, 33.3 at% Cr, and 33.3 at% Ni, with a corresponding thickness of 0.2 mm.
[0026] Step 3: Place the sample in a high-temperature brazing furnace. To prevent the brazing filler metal from evaporating during high-temperature brazing and to ensure the atmosphere, use two Al2O3 ceramic vessels to cover the sample from top to bottom. Seal the contact gap between the vessels by embedding Al2O3 ceramic particles with a diameter of 0.5mm.
[0027] Step 4: Heat in a vacuum brazing furnace. First, heat to 400℃ at a heating rate of 4.5℃ / min, hold for 20 minutes, then continue heating at the same rate, hold at 800℃ for 20 minutes, then continue heating at the same rate to 1120℃ and hold for 27 minutes. Then cool down at a rate of 4.5℃ / min to 400℃, and then furnace cool. After brazing, the high-entropy alloy filler metal, pure Ni, and CoCrNi medium-entropy alloy still exist, maintaining the structure of Step 2.
[0028] A shear test was conducted on a SiC ceramic and Inconel 718 nickel-based superalloy joint brazed by butt joint using a universal testing machine. During the application of load to the joint, the moving speed of the universal testing machine indenter was 0.5 mm / min. The shear strength was 90.6 MPa at room temperature and 33.2 MPa at 400 degrees Celsius.
Claims
1. A brazing method for silicon carbide ceramics and high-temperature alloys, characterized in that, The steps include the following: Step 1: Prepare foils from high-entropy alloy brazing filler metal, pure Ni, and CoCrNi medium-entropy alloy; polish the surfaces of silicon carbide ceramic and nickel-based high-temperature alloy. Since SiC ceramic has a very high hardness, use the rollers of a rolling mill to polish the surface. Then, ultrasonically clean the sheet-like high-entropy alloy brazing filler metal, pure Ni sheet, and sheet-like CoCrNi medium-entropy alloy. Step 2: Bond the sheet-like high-entropy alloy solder, pure Ni sheet, and sheet-like CoCrNi medium-entropy alloy between the silicon carbide ceramic and the nickel-based superalloy using an adhesive. The final order is as follows: nickel-based superalloy, sheet-like high-entropy alloy solder, pure Ni sheet, sheet-like high-entropy alloy solder, sheet-like CoCrNi medium-entropy alloy, sheet-like high-entropy alloy solder, silicon carbide ceramic. Step 3: Place the above multi-layer structure in a high-temperature brazing furnace. To prevent the brazing filler metal from evaporating during high-temperature brazing and to ensure the atmosphere, use two Al2O3 ceramic vessels to encase the multi-layer structure. Seal the contact gap between the vessels by embedding Al2O3 ceramic particles with a diameter of 0.5mm-1mm. Step 4: Heat in a vacuum brazing furnace, first to 400℃ and hold for 10-20 minutes, with a heating rate of 4.5℃ / min - 6℃ / min; then continue heating to 800℃ and hold at 800℃ for 20-30 minutes, with a heating rate of 4.5℃ / min - 6℃ / min; then continue heating to 1120℃ and hold for 23-37 minutes, with a heating rate of 4.5℃ / min - 6℃ / min; subsequently cool down to 400℃, with a cooling rate of 4.5℃ / min - 6℃ / min, and then allow the furnace to cool naturally; after brazing, the high-entropy alloy filler metal, pure Ni, and CoCrNi medium-entropy alloy still maintain their original layered structure; Each layer of high-entropy alloy solder sheet has a thickness of 0.08-0.1 mm and a composition of: 27-35 at% Cu, 27-35 at% Mn, 8-12 at% Cr, 9-12 at% Co, 6-11 at% Fe, and 3-7 at% Ti; the sheet-like CoCrNi medium-entropy alloy has a thickness of 0.15-0.2 mm and a composition of: 34-35 at% Co, 33-35 at% Ni, and 30-33 at% Cr; the pure Ni sheet has a thickness of 0.15-0.2 mm and a Ni purity greater than 99.9%.
2. The silicon carbide ceramic-high temperature alloy brazed heterojunction prepared according to the method of claim 1.