A brazing connection method of GH3535 superalloy and CVI-SiCf / SiC composite material

Abstract

The application discloses a brazing connection method of GH3535 high-temperature alloy and CVI-SiCf / SiC composite material, and belongs to the technical field of high-temperature alloy and ceramic matrix composite material connection. The application aims at solving the technical problem that the existing nickel-based filler metal is difficult to consider the melting, spreading and interface reaction when being used for connecting the GH3535 high-temperature alloy and the SiC composite material. The GH3535 high-temperature alloy, the Ni-Zr filler metal and the SiC composite material are sequentially arranged to form a sandwich type to-be-welded assembly. In the brazing process, the Ni-Zr14 filler metal is melted at 1150-1220 DEG C and forms a brazing seam area between the two base materials; through controlling the heating, holding and cooling processes, the melting and spreading of the filler metal can be realized, and the adverse effects of the thermal cycle on the joint structure and the interface bonding can be reduced.

Description

Technical Field

[0001] This invention belongs to the field of high-temperature alloy and ceramic matrix composite material joining technology, specifically, it relates to a brazing joining method of GH3535 high-temperature alloy and CVI-SiCf / SiC composite material. Background Technology

[0002] GH3535 alloy is a Ni-Mo-Cr based nickel-based superalloy with good high-temperature strength, corrosion resistance, and structural stability, making it suitable for complex service environments such as high-temperature molten salt. SiC composite materials possess advantages such as low density, high specific strength, high temperature resistance, and corrosion resistance. Joining GH3535 alloy with SiC composite materials leverages the respective performance advantages of both materials, showing promise for applications in nuclear power equipment and high-temperature structural components.

[0003] However, the physical and chemical properties of GH3535 alloy and SiC composite materials differ significantly. Their coefficients of thermal expansion and elastic moduli are mismatched, making it easy for brazed joints to generate large residual stresses during cooling. Furthermore, the surface chemical properties of SiC composite materials are stable, and ordinary metal brazing filler metals have poor wettability, making it difficult to directly form a reliable connection. Therefore, the composition of the brazing filler metal, the brazing temperature, and the holding time have a significant impact on the joint interface microstructure and connection performance.

[0004] Currently, the joining of SiC composite materials with nickel-based superalloys mostly employs brazing filler metal systems such as Au-Ni and Cu-Ni. While these filler metals can achieve joining under certain conditions, the range of brazing process parameters is relatively narrow. At low brazing temperatures, insufficient melting and flow of the filler metal makes it difficult to fully fill the joint gap; at excessively high brazing temperatures or prolonged holding times, the reaction between Ni and SiC composite materials intensifies, easily forming Ni-Si and other reaction products near the interface. An excessively thick or discontinuous interfacial reaction layer reduces the joint's plasticity and increases the risk of joint cracking.

[0005] To lower the melting temperature of nickel-based brazing filler metals, conventional methods typically involve adding melting-reducing elements such as boron (B) and silicon (Si). While B and Si can improve the melting and flow properties of the filler metal, they may form brittle phases such as borides and silicides during brazing, adversely affecting the brazed joint microstructure and joint performance. For the heterogeneous joining system of GH3535 alloy and SiC composite material, achieving sufficient melting and spreading of the filler metal at a relatively low brazing temperature, while controlling the interfacial reaction, is crucial for obtaining a reliable brazed joint.

[0006] Therefore, it is necessary to develop a brazing filler metal and brazing method suitable for joining GH3535 alloy and SiC composite materials, which can reduce the formation of brittle reaction products and improve the bonding state of the joint interface while ensuring that the brazing filler metal has a suitable melting temperature and spreading ability. Summary of the Invention

[0007] The technical problem solved by this invention is that when existing nickel-based brazing filler metals are used to join GH3535 high-temperature alloy and SiC composite materials, it is usually necessary to add melting-reducing elements such as boron (B) and silicon (Si) to lower the melting temperature of the filler metal. During brazing, brittle reactive phases are easily generated, and it is difficult to simultaneously control the melting, spreading, and interfacial reactions of the filler metal, thus affecting the reliability of the joint connection. To solve the above technical problems, this invention provides a brazing connection method for GH3535 high-temperature alloy and SiC composite materials.

[0008] To address the aforementioned technical problems, the present invention adopts the following technical solution: The purpose of this invention is to provide a brazing connection method for GH3535 high-temperature alloy and CVI-SiCf / SiC composite material, comprising the following steps: Step 1: Grind, ultrasonically clean, and dry the surfaces of the GH3535 high-temperature alloy and the SiC composite material to be joined, respectively. Step 2: Place the Ni-Zr solder sheet between the surfaces to be joined of the GH3535 high-temperature alloy and the SiC composite material, assemble them into a sandwich structure, and obtain the component to be soldered. Step 3: Then, brazing is performed under vacuum to obtain a brazed joint of GH3535 high-temperature alloy and SiC composite material.

[0009] Furthermore, the mass fraction of Zr in the Ni-Zr solder sheet is 10%-15%.

[0010] Further specified, the thickness of the Ni-Zr brazing filler sheet is 0.3mm-0.6mm; it is made by melting nickel and zirconium as raw materials to obtain Ni-Zr brazing filler ingots, the melting is carried out in a vacuum arc melting furnace, the current during the melting process is 200A and the voltage is 30V, and the melted ingot is processed into brazing filler sheets by wire cutting.

[0011] Further specifying, use 240 grit, 400 grit, 800 grit, and 1200 grit sandpaper to polish the surfaces to be joined.

[0012] Further specified, ultrasonic cleaning was performed using anhydrous ethanol.

[0013] Further specifying, the vacuum level reaches 2.7 × 10⁻⁶. -5 Pa.

[0014] Further defining the brazing process, it includes: heating from room temperature to 300℃ at a rate of 5-10℃ / min and holding at that temperature for 10-20 min; heating from 300℃ to 1100℃ at a rate of 5-10℃ / min; heating from 1100℃ to 1150-1220℃ at a rate of 5-10℃ / min and holding at 1200℃ for 5-15 min; after holding at that temperature, cooling from 1200℃ to 800℃ at a rate of 5-10℃ / min, and then cooling from 800℃ to 130℃ at a rate of 5-10℃ / min, followed by furnace cooling to room temperature.

[0015] Based on the specific implementation method, the present invention provides a brazing connection method for GH3535 high-temperature alloy and SiC composite material, which is carried out according to the following steps: Step S1: Prepare GH3535 high-temperature alloy, SiC composite material and Ni-Zr14 solder; the Ni-Zr14 solder is a Ni-Zr binary solder, wherein the mass fraction of Zr is 14% and the balance is Ni.

[0016] Step S2: Surface treatment is performed on the surfaces to be joined of the GH3535 high-temperature alloy and the SiC composite material. Specifically, the surfaces to be joined are polished sequentially using 240-grit, 400-grit, 800-grit, and 1200-grit sandpaper; then, the GH3535 high-temperature alloy, SiC composite material, and Ni-Zr14 brazing filler metal are ultrasonically cleaned in anhydrous ethanol for 20 minutes and dried for later use.

[0017] Step S3: Place the Ni-Zr14 solder sheet between the GH3535 high-temperature alloy and the SiC composite material to obtain the component to be soldered. The component to be soldered is a sandwich structure of SiC composite material / Ni-Zr14 solder / GH3535 high-temperature alloy.

[0018] Step S4: Place the component to be soldered in a vacuum brazing furnace. When the vacuum level inside the furnace reaches 2.7 × 10⁻⁶... -5 Brazing was performed after Pa. The brazing process included: heating from room temperature to 300℃ at 10℃ / min and holding for 20 min; heating from 300℃ to 1100℃ at 10℃ / min; heating from 1100℃ to 1200℃ at 5℃ / min and holding at 1200℃ for 15 min; after holding, cooling from 1200℃ to 800℃ at 5℃ / min, and then cooling from 800℃ to 130℃ at 7.5℃ / min, followed by furnace cooling to room temperature, to obtain the brazed joint of GH3535 high-temperature alloy and SiC composite material.

[0019] This invention uses Ni-Zr brazing filler metal as the intermediate filler metal. The Ni-Zr filler metal is designed based on the Ni-Zr eutectic system. By adding Zr, the melting temperature of the nickel-based filler metal is lowered, allowing it to melt, spread, and fill the gap between the GH3535 high-temperature alloy and the SiC composite material at 1150-1220℃. Compared to conventional nickel-based filler metals that lower the melting point by adding more B and Si, this invention does not add additional B or Si, which helps reduce the risk of B and Si-related brittle phase formation. In this invention, the GH3535 high-temperature alloy, Ni-Zr filler metal, and SiC composite material sequentially constitute a sandwich-type assembly to be brazed. During brazing, the Ni-Zr filler metal melts at 1150-1220℃ and forms a brazing seam zone between the two base materials. By controlling the heating, holding, and cooling processes, the melting and spreading of the filler metal can be achieved while reducing the adverse effects of thermal cycling on the joint microstructure and interfacial bonding.

[0020] Another objective of this invention is to provide a brazed joint of GH3535 high-temperature alloy and SiC composite material, which is prepared by any of the methods described above.

[0021] In addition, a brazing filler metal sheet for connecting GH3535 high-temperature alloy and SiC composite material is provided. The Ni-Zr brazing filler metal sheet material is a Ni-Zr binary brazing filler metal, wherein the mass fraction of Zr is 10%-15% and the balance is Ni.

[0022] Compared with the prior art, the present invention has the following beneficial effects: This invention uses Ni-Zr binary solder as the intermediate solder and utilizes the Ni-Zr eutectic system to reduce the melting temperature of nickel-based solder, enabling the solder to melt and spread at 1150-1220℃. This solves the problem that conventional nickel-based solders have high melting temperatures and are difficult to complete connections at suitable temperatures.

[0023] This invention does not add commonly used melting-reducing elements such as B and Si, but achieves melting reduction of the solder through the Ni-Zr system, which helps to reduce the possibility of B, Si and other elements forming brittle reaction phases in the solder seam.

[0024] This invention adopts a sandwich-type assembly structure of GH3535 high-temperature alloy / Ni-Zr brazing filler metal / SiC composite material. The size of the brazing filler metal sheet matches the size of the SiC composite material to be joined, which allows the brazing filler metal to cover the joining area and facilitates the melting, spreading and filling of the brazing filler metal at the interface.

[0025] This invention controls the heating, holding, and cooling processes during brazing. Specifically, it holds the temperature at 300℃ for 20 minutes and uses a relatively low heating rate of 5-10℃ / min during the staged heating process. After brazing, it employs a segmented cooling method, which helps to reduce the adverse effects of sudden temperature changes on the joint during thermal cycling.

[0026] Based on the elemental distribution results of the joint cross section, Si and C elements are mainly distributed on the SiC composite material side, Mo and Cr elements are mainly distributed on the GH3535 high-temperature alloy side, and Zr elements are enriched near the interface, indicating that under the brazing process conditions, Ni-Zr brazing filler metal participates in the connection process between GH3535 high-temperature alloy and SiC composite material.

[0027] For a deeper understanding of the features and technical content of this invention, please refer to the accompanying detailed description and drawings. It should be noted that the drawings are provided for illustrative purposes only and are not intended to limit the scope of the invention. Attached Figure Description

[0028] Figure 1 SEM characterization of the brazed joint of GH3535 high-temperature alloy and SiC composite material; Figure 2 This is the result of the elemental surface scan distribution of the brazed joint; Figure 3 It is an elemental distribution curve of the brazed joint. Detailed Implementation

[0029] The present invention will be described in detail below with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but should not be considered as limiting the present invention. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0030] Example 1: This example uses Ni-Zr14 solder to connect GH3535 high-temperature alloy and SiC composite material. The SiC composite material is prepared by the CVI method; the Ni-Zr14 solder is a Ni-Zr binary solder with a Zr mass fraction of 14% and the balance being Ni. The Ni-Zr14 solder sheet thickness is 0.5 mm. The Ni-Zr solder ingot is obtained by melting nickel and zirconium in a vacuum arc melting furnace at a current of 200 A and a voltage of 30 V. The melted ingot is then processed into solder sheets using wire cutting.

[0031] The brazing connection method between GH3535 high-temperature alloy and SiC composite material provided in this embodiment is carried out according to the following steps: Step 1: Sample preparation.

[0032] The GH3535 high-temperature alloy was machined into block specimens with dimensions of 10 mm × 10 mm × 5 mm; the SiC composite material was machined into block specimens with dimensions of 5 mm × 5 mm × 3 mm; and the Ni-Zr14 solder was machined into sheet-shaped solder with dimensions of 5 mm × 5 mm × 0.5 mm. The size of the GH3535 high-temperature alloy specimen was larger than that of the SiC composite specimen, and the area of ​​the Ni-Zr14 solder sheet corresponded to the area of ​​the SiC composite specimen to be joined, thus enabling the solder sheet to cover the entire area of ​​the SiC composite to be joined.

[0033] Step 2, surface treatment.

[0034] The surfaces to be joined on the GH3535 high-temperature alloy sample and the SiC composite material sample were ground and polished respectively. During grinding, 240 grit, 400 grit, 800 grit and 1200 grit sandpaper were used in sequence to grind the surfaces to be joined, so as to make the surfaces flat and remove the oxide layer, processing damage layer and attached impurities.

[0035] The polished GH3535 high-temperature alloy sample, SiC composite material sample, and Ni-Zr14 brazing filler metal sheet were ultrasonically cleaned in anhydrous ethanol for 20 min. After ultrasonic cleaning, each sample was removed and dried for later use.

[0036] Step 3: Sample assembly.

[0037] SiC composite material sample, Ni-Zr14 brazing filler metal sheet and GH3535 high-temperature alloy sample are stacked in sequence, with the Ni-Zr14 brazing filler metal sheet sandwiched between the SiC composite material sample and the GH3535 high-temperature alloy sample, forming a sandwich-type assembly to be welded of SiC composite material / Ni-Zr14 brazing filler metal / GH3535 high-temperature alloy.

[0038] During assembly, ensure that the Ni-Zr14 solder sheet corresponds perfectly to the 5 mm × 5 mm surface of the SiC composite material to be joined, and maintain relative positioning between the SiC composite material, the solder sheet, and the GH3535 high-temperature alloy.

[0039] Step 4: Vacuum brazing.

[0040] The components to be soldered are placed in a vacuum brazing furnace, and a vacuum is drawn until the vacuum level inside the furnace reaches 2.7 × 10⁻⁶. -5 Brazing is performed after Pa. The brazing thermal cycle process is as follows: The temperature was increased from room temperature to 300℃ at a rate of 10℃ / min and held at 300℃ for 20 min; then the temperature was increased from 300℃ to 1100℃ at a rate of 10℃ / min; then the temperature was increased from 1100℃ to 1200℃ at a rate of 5℃ / min and held at 1200℃ for 15 min.

[0041] After the heat preservation was completed, the temperature was reduced from 1200℃ to 800℃ at a rate of 5℃ / min; then it was reduced from 800℃ to 130℃ at a rate of 7.5℃ / min; when the furnace temperature dropped to 130℃, the programmed temperature control was stopped, and the sample was cooled to room temperature with the furnace to obtain the brazed joint of GH3535 high temperature alloy and SiC composite material.

[0042] The cross-sectional microstructure and EDS elemental distribution of the obtained brazed joint were analyzed. (See attached figures.) Figure 1 SEM characterization of the brazed joint of GH3535 high-temperature alloy and SiC composite material. Figure 2 The attached figure shows the elemental surface scan distribution of the brazed joint. As can be seen from the figure, Si and C elements are mainly distributed in... Figure 1 The left side of the image shows the SiC composite material; Mo and Cr elements are mainly distributed in the right side, which is the GH3535 high-temperature alloy. Ni element is distributed in the brazing seam area and adjacent areas on both sides, while Zr element is mainly enriched near the connection interface close to the SiC composite material side, indicating that Ni-Zr14 brazing filler metal participated in the brazing connection process between the GH3535 high-temperature alloy and the SiC composite material.

[0043] Elemental line scan results of brazed joints are as follows Figure 3 As shown in the figure, the region to the left of the scan line has a higher content of C and Si elements, which corresponds to the CVI-SiCf / SiC composite material side; the region to the right has a higher content of Ni elements, accompanied by Mo and Cr elements, which corresponds to the GH3535 high-temperature alloy side. In the transition region between the two base materials, the contents of Ni, Zr, and Si change. Ni extends from the GH3535 side towards the brazing seam, while Zr is mainly distributed near the interface close to the SiC composite material side. These results indicate that the Ni-Zr14 brazing filler metal melts during brazing and participates in the interfacial bonding between the GH3535 high-temperature alloy and the CVI-SiCf / SiC composite material.

[0044] The specific embodiments of the present invention have been described in detail above. It should be noted that the present invention is not limited to the specific embodiments described above. Various modifications or alterations can be made by those skilled in the art without departing from the scope of protection defined by the claims, and all such modifications or alterations fall within the scope of the present invention.

Claims

1. A brazing method for joining GH3535 high-temperature alloy and CVI-SiCf / SiC composite material, characterized in that, Includes the following steps: Step 1: Grind, ultrasonically clean, and dry the surfaces of the GH3535 high-temperature alloy and the SiC composite material to be joined, respectively. Step 2: Place the Ni-Zr solder sheet between the surfaces to be joined of the GH3535 high-temperature alloy and the SiC composite material, assemble them into a sandwich structure, and obtain the component to be soldered. Step 3: Then, brazing is performed under vacuum to obtain a brazed joint of GH3535 high-temperature alloy and SiC composite material.

2. The method according to claim 1, characterized in that, The mass fraction of Zr in Ni-Zr solder is 10%-15%.

3. The method according to claim 1, characterized in that, Use 240-grit, 400-grit, 800-grit, and 1200-grit sandpaper to polish the surfaces to be joined.

4. The method according to claim 1, characterized in that, Ultrasonic cleaning with anhydrous ethanol, acetone, or plasma water.

5. The method according to claim 1, characterized in that, The thickness of the brazing filler metal sheet is 0.3mm-0.6mm.

6. The method according to claim 1, characterized in that, The vacuum level reached 2.7 × 10⁻⁶. -5 Pa.

7. The method according to claim 1, characterized in that, The brazing process includes: heating from room temperature to 300℃ at a rate of 5-10℃ / min and holding for 10-20 min; heating from 300℃ to 1100℃ at a rate of 5-10℃ / min; heating from 1100℃ to 1150-1220℃ at a rate of 5-10℃ / min and holding at 1200℃ for 5-15 min; after holding, cooling from 1200℃ to 800℃ at a rate of 5-10℃ / min, then cooling from 800℃ to 130℃ at a rate of 5-10℃ / min, and then cooling to room temperature with the furnace.

8. The method according to claim 1, characterized in that, The brazing process includes: heating from room temperature to 300℃ at 10℃ / min and holding at that temperature for 20 min; heating from 300℃ to 1100℃ at 10℃ / min; heating from 1100℃ to 1200℃ at 5℃ / min and holding at 1200℃ for 15 min; after holding at that temperature, cooling from 1200℃ to 800℃ at 5℃ / min, and then cooling from 800℃ to 130℃ at 7.5℃ / min, followed by furnace cooling to room temperature.

9. A brazed joint of GH3535 high-temperature alloy and SiC composite material, characterized in that, It is prepared by any one of claims 1 to 8.

10. A brazing filler metal sheet for connecting GH3535 high-temperature alloy and SiC composite material, characterized in that, The Ni-Zr solder sheet material is a Ni-Zr binary solder, wherein the mass fraction of Zr is 10%-15%, and the balance is Ni.

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