Medium-entropy brazing filler metal for Ni-based high-temperature alloy brazing

Abstract

The invention relates to the technical field of Ni-based high-temperature alloy welding, in particular to medium-entropy brazing filler metal for Ni-based high-temperature alloy brazing. The medium-entropy brazing filler metal for brazing the Ni-based high-temperature alloy, provided by the invention, comprises the following components in percentage by weight: 5.0 to 15.0 percent of Cr, 5.0 to 10.0 percent of Co, 4.0 to 9.0 percent of W, 5.0 to 10.0 percent of Ta, 5.0 to 8.0 percent of Al, 1.0 to 4.0 percent of B and the balance of Ni. According to the medium-entropy brazing filler metal for Ni-based high-temperature alloy brazing, the entropy value range of the structure ranges from 0.69 R to 1.61 R, precipitation of brittle compounds can be restrained, the performance of a connector is improved, and the stability of the connector is guaranteed. According to the medium-entropy brazing filler metal for Ni-based high-temperature alloy brazing, a proper amount of B element is added, addition of Si element is avoided, the content of brittle compounds can be further reduced on the premise that the alloy melting point is effectively reduced, and the joint performance is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of Ni-based superalloy welding, and particularly to a medium-entropy filler metal for brazing Ni-based superalloys. Background Art

[0002] Ni-based superalloys have excellent high-temperature properties and oxidation resistance, and are the main materials for manufacturing high-temperature components of aeroengines. During the manufacturing process of high-temperature components, welding problems will inevitably arise. Due to the complex internal structure and harsh service environment of aeroengines, achieving highly reliable welding of their high-temperature components is crucial for the safe use of aeroengines.

[0003] Due to the usually complex structural characteristics and extremely high welding precision requirements of high-temperature components, brazing is one of the most suitable welding techniques for high-temperature components, and the core of this technique is the design of filler metal composition. To obtain a lower melting point, the design concept of high-temperature alloy filler metal composition is usually to add more melting-point-lowering elements (such as Si, B, etc.) to Ni-based or Ni-Cr-based alloys, which will result in a large amount of silicides and borides remaining in the brazed joint, significantly reducing the high-temperature performance of the joint. Usually, the high-temperature strength of the joint can only reach 60-70% of the performance of the base material, and its plasticity is even less than 10% of the performance of the base material. Therefore, it is necessary to develop a new type of Ni-based superalloy filler metal to improve the high-temperature performance of the brazed joint.

[0004] Medium / high-entropy alloys (entropy value > 0.69R) break through the single-principal-element composition design concept of traditional alloys. The relatively high mixing entropy of their alloy systems can inhibit the appearance of intermetallic compounds, which is beneficial to improving the stability of the alloy. Applying its composition design concept to high-temperature alloy filler metals can effectively improve the problem of compound residue in the joint and enhance the high-temperature performance of the joint. Compared with high-entropy alloys (entropy value > 1.61R), medium-entropy alloys (0.69R < entropy value ≤ 1.61R) have lower costs, better controllability of composition and performance, and are more suitable for large-scale production and application. However, the melting points of conventional medium-entropy alloys are generally relatively high (higher than 1300°C). If conventional medium-entropy alloys are used for brazing, the performance of the base material to be welded will inevitably be significantly reduced.

[0005] Therefore, it is necessary to develop a medium-entropy alloy filler metal with a lower melting point to obtain joints with good high-temperature performance and meet the service requirements of high-temperature components of aeroengines. Summary of the Invention

[0006] (I) Technical Problems to be Solved

[0007] The technical problem to be solved by the present invention is to overcome the problem that it is difficult for medium-entropy alloy filler metals to coexist with low melting points and good high-temperature performance.

[0008] (II) Technical Solutions

[0009] To solve the above technical problems, the present invention provides a medium-entropy filler metal for brazing Ni-based superalloys. The weight percentages of the alloy components of the medium-entropy filler metal are as follows: Cr 5.0-15.0%, Co 5.0-10.0%, W 4.0-9.0%, Ta 5.0-10.0%, Al 5.0-8.0%, B 1.0-4.0%, and the balance is Ni.

[0010] As a preferred embodiment of the present invention, the weight percentages of the alloy components of the medium-entropy filler metal are as follows: Cr 8.0-10.0%, Co 8.0-9.0%, W 5.0-8.0%, Ta 6.0-9.0%, Al 6.0-7.0%, B 1.0-4.0%, and the balance is Ni.

[0011] As a preferred embodiment of the present invention, the medium-entropy filler metal is an amorphous alloy foil strip with a thickness of 20-50 μm.

[0012] The present invention also provides a method for welding using the medium-entropy filler metal for brazing Ni-based superalloys, including the following steps:

[0013] S1. Pretreatment of the base material;

[0014] S2. Preparing the filler metal: Place the amorphous alloy foil strip made of the medium-entropy filler metal for brazing Ni-based superalloys between the surfaces to be welded of the two base materials.

[0015] S3. Brazing to weld the two base materials.

[0016] As a preferred embodiment of the present invention, in step S3, the brazing is carried out using a vacuum brazing furnace, with a heating rate of 10-15 °C / min, a brazing temperature of 1000-1200 °C, and after holding for 10-240 min, the furnace is cooled.

[0017] As a preferred embodiment of the present invention, in step S3, during the brazing process, the vacuum degree in the vacuum brazing furnace is higher than 1×10 -2 Pa.

[0018] The present invention also provides an application of the medium-entropy filler metal for brazing Ni-based superalloys in the welding of aeroengines.

[0019] (III) Beneficial effects

[0020] The above technical solutions of the present invention have the following advantages:

[0021] 1. The configurational entropy value range of the filler metal alloy of the present invention is between 0.69R - 1.61R (R is the gas constant), which can inhibit the precipitation of brittle compounds, improve the joint performance, and ensure the stability of the joint.

[0022] 2. The alloy of the present invention has a low content of precious metal elements, low cost, good controllability of composition and performance, and is suitable for large-scale production and application.

[0023] 3. The solder alloy of the present invention adds an appropriate amount of B element and avoids adding Si element, which can further reduce the content of brittle compounds and improve joint performance while effectively lowering the melting point of the alloy.

[0024] 4. The solder alloy components of the present invention are all common elements in high-temperature alloys, which is conducive to obtaining a joint with a structure and performance similar to that of the parent material. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a microstructure diagram of the GH3536 joint in Example 2 of the present invention;

[0026] Figure 2 This is a microstructure diagram of the GH3536 joint in Example 4 of the present invention. DETAILED DESCRIPTION

[0027] The following embodiments of the present invention are described in further detail with reference to the accompanying drawings and examples. The following examples are used to illustrate the present invention but are not intended to limit the scope of the present invention.

[0028] Example 1

[0029] This embodiment provides a medium-entropy brazing filler metal for brazing Ni-based high-temperature alloys. The alloy composition of the medium-entropy filler metal is as follows: 10.0% Cr, 8.2% Co, 6.4% W, 8.0% Ta, 6.2% Al, 2.0% B, with the balance being Ni. The alloy configuration entropy of the medium-entropy filler metal is 0.91R.

[0030] The medium entropy solder provided in this embodiment is made into an amorphous alloy foil with a thickness of 50 μm for use.

[0031] Example 2

[0032] This embodiment uses the amorphous alloy foil provided in Example 1 to braze the GH3536 alloy, and the process includes the following steps:

[0033] (1) Pretreatment of base material: Use sandpaper to grind the surface of the base material to be welded to ensure that there is no oxide layer and impurities on the surface to be welded; place the ground base material in alcohol for ultrasonic cleaning for 10 minutes; after cleaning, dry the base material for later use.

[0034] (2) Pre-setting solder: Place a layer of amorphous alloy foil between the two sides of the base material to be welded.

[0035] (3) Brazing: A vacuum brazing furnace is used for brazing. The heating rate is 12 °C / min, the brazing temperature is 1160 °C, and after holding for 60 min, the furnace is cooled. During the whole process, the vacuum degree in the furnace is ensured to be higher than 1×10 -2 Pa.

[0036] The microstructure of the GH3536 joint obtained by welding in this example is as Figure 1 shown. Its high-temperature tensile strength and elongation at 900 °C are 229 MPa and 52% respectively, reaching 83.3% and 46.8% of the base metal respectively.

[0037] Example 3

[0038] This example provides a medium-entropy filler metal for brazing Ni-based superalloys. The weight percentages of the alloying elements of the medium-entropy filler metal are as follows: Cr 8.0%, Co 9.0%, W 7.6%, Ta 6.2%, Al 6.7%, B 1.5%, and the balance is Ni. The configurational entropy of the medium-entropy filler metal is 0.91R.

[0039] The medium-entropy filler metal provided in this example is made into an amorphous alloy foil strip with a thickness of 50 μm for use.

[0040] Example 4

[0041] In this example, the amorphous alloy foil strip provided in Example 3 is used for brazing the GH3536 alloy, and its process includes the following steps:

[0042] (1) Pretreatment of the base metal: The surface of the base metal to be welded is polished with sandpaper to ensure that there is no oxide layer and impurities on the surface to be welded; the polished base metal is placed in alcohol and ultrasonically cleaned for 10 min; after cleaning, the base metal is dried for standby.

[0043] (2) Filler metal pre-placement: One layer of amorphous alloy foil strip is placed between the surfaces to be welded of the two base metals.

[0044] (3) Brazing: A vacuum brazing furnace is used for brazing. The heating rate is 12 °C / min, the brazing temperature is 1120 °C, and after holding for 30 min, the furnace is cooled. During the whole process, the vacuum degree in the furnace is ensured to be higher than 1×10 -2 Pa.

[0045] The microstructure of the obtained GH3536 joint is as Figure 2 shown. Its high-temperature tensile strength and elongation at 900 °C are 226 MPa and 56% respectively, reaching 82.2% and 50.5% of the base metal respectively.

[0046] It should be clear that the various embodiments in this specification are described in a progressive manner. For the same or similar parts among the various embodiments, reference can be made to each other. Each embodiment focuses on the differences from other embodiments. For the method embodiments, relevant parts can refer to the partial description of the device embodiments (adopted according to the writing situation). The present invention is not limited to the specific steps and structures described above and shown in the figures. And, for the sake of brevity, the detailed description of known method technologies is omitted here.

[0047] The above is only the preferred embodiment of the present invention. It should be noted that for those of ordinary skill in the art in this technical field, without departing from the technical principle of the present invention, several improvements and modifications can still be made, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A medium-entropy filler metal for brazing Ni-based superalloys, characterized in that, The weight percentages of the components of the medium-entropy filler metal alloy are as follows: Cr 5.0 to 15.0%, Co 5.0 to 10.0%, W 4.0 to 9.0%, Ta 5.0 to 10.0%, Al 5.0 to 8.0%, B 1.0 to 4.0%, and the balance is Ni.

2. The medium-entropy filler metal according to claim 1, wherein, The weight percentages of the components of the medium-entropy filler metal alloy are as follows: Cr 8.0 to 10.0%, Co 8.0 to 9.0%, W 5.0 to 8.0%, Ta 6.0 to 9.0%, Al 6.0 to 7.0%, B 1.0 to 4.0%, and the balance is Ni.

3. The medium-entropy filler metal according to claim 1, wherein The medium-entropy filler metal is an amorphous alloy foil strip with a thickness of 20 to 50 μm.

4. A welding method using the medium-entropy filler metal for brazing Ni-based superalloys according to any one of claims 1-3, characterized in that, It includes the following steps: S1. Pretreatment of the base metal; S2. Pre-placing the filler metal: Place the amorphous alloy foil strip made of the medium-entropy filler metal for Ni-based superalloy brazing between the welding surfaces of the two base metals on both sides. S3. Weld the two base metals on both sides by brazing.

5. The method according to claim 4, characterized in that, In step S3, the brazing is carried out using a vacuum brazing furnace, with a heating rate of 10 to 15 °C / min, a brazing temperature of 1000 to 1200 °C, and after holding for 10 to 240 min, the furnace is cooled.

6. The method according to claim 4, wherein In step S3, during the brazing process, the vacuum degree in the vacuum brazing furnace is higher than 1×10 -2 Pa.

7. Application of the medium-entropy filler metal for Ni-based superalloy brazing according to any one of claims 1-3 in the welding of aeroengines.

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