Method for diffusion bonding of nickel-based superalloy and niobium-based alloy through high-entropy alloy interlayer

Abstract

The invention discloses a method for diffusion bonding of a nickel-based superalloy and a niobium-based alloy through a high-entropy alloy interlayer, which comprises the following steps: step 1, selecting the nickel-based superalloy or the niobium-based alloy as a substrate, and carrying out diffusion bonding on the nickel-based superalloy and the niobium-based alloy as base materials; depositing a high-entropy alloy intermediate layer on a to-be-welded surface of the substrate by adopting a physical vapor deposition method, and then assembling according to a sequence of nickel-based high-temperature alloy, the high-entropy alloy intermediate layer and niobium-based alloy to obtain a to-be-connected piece; and 2, performing vacuum diffusion bonding on the to-be-bonded piece obtained in the step 1. According to the method, the nanocrystalline high-entropy alloy is introduced through physical vapor deposition, the roughness of the to-be-welded face can be remarkably reduced, and the diffusion bonding efficiency is improved; and meanwhile, the high-entropy alloy has a hysteresis diffusion effect, the thickness of an interface intermetallic compound layer can be remarkably reduced, the mechanical strength and plasticity of the joint are improved, and the method is suitable for the fields of aerospace, nuclear reactors and the like.

Description

Technical Field

[0001] This invention belongs to the field of joining heterogeneous refractory metal materials, and in particular relates to a method for diffusion joining of nickel-based superalloys and niobium-based alloys in a high-entropy alloy interlayer. Background Technology

[0002] Niobium and its alloys, refractory metals, are widely used in rocket engines, aerospace, and nuclear reactors due to their high melting point, excellent high-temperature mechanical properties, corrosion resistance, good room-temperature workability, and thermal conductivity. Nickel-based superalloys, with their excellent room-temperature strength and ductility, good creep resistance, and weldability, are also ideal materials for components in aerospace engines and nuclear reactor heat exchangers. Considering the varying requirements for material temperature resistance and high-temperature performance in different components, as well as cost control needs for engine and reactor components, practical applications often involve the welding of niobium alloys with nickel-based superalloys. Examples include connecting the flame tubes made of Nb521 alloy to the reinforcing rings made of nickel-based superalloys in aero-engines; welding nickel-based superalloys to Nb alloys in the outermost metal honeycomb sandwich structure of the thermal protection system of hypersonic vehicles; and the use of nickel-based superalloys and niobium-based alloys in the connection of alkali metal side and gas-cooled side components of nuclear reactor heat exchangers.

[0003] Researchers have conducted extensive studies on nickel-based superalloys and niobium-based alloys using methods such as vacuum electron beam welding, laser welding, vacuum brazing, and diffusion bonding. However, due to the metallurgical immiscibility between Ni and Nb, brittle intermetallic compounds such as Ni3Nb, Ni6Nb7, and Ni8Nb are easily formed at the joint, deteriorating the joint performance. Joints prepared using fusion welding methods such as electron beam welding / laser welding have a maximum room temperature tensile strength of 328 MPa and an elongation of only about 3% (Gang Zhao, Jie Ning, Linjie Zhang, et al, Adding Ta-based interlayer improve the performance of GH3128-Nb521 dissimilar material laser butt welded joints. Journal of Materials Research and Technology. 2025, 36:6316-6329). Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for diffusion bonding of nickel-based superalloys and niobium-based alloys using a high-entropy alloy interlayer. This method introduces a nanocrystalline high-entropy alloy through physical vapor deposition, which can significantly reduce the roughness of the surfaces to be welded and improve diffusion bonding efficiency. Simultaneously, the hysteresis diffusion effect of the high-entropy alloy can significantly reduce the thickness of the intermetallic compound layer at the interface, improving the mechanical strength and plasticity of the joint, thus solving the problem of poor plasticity in nickel-niobium joints prepared by existing technologies.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is: a method for diffusion bonding of nickel-based superalloys and niobium-based alloys in a high-entropy alloy interlayer, characterized in that the method includes the following steps: Step 1: The base materials are nickel-based superalloys and niobium-based alloys. Select a nickel-based superalloy or niobium-based alloy as the substrate, and use physical vapor deposition to deposit a high-entropy alloy intermediate layer on the surface to be welded on the substrate. Then assemble them in the order of nickel-based superalloy / high-entropy alloy intermediate layer / niobium-based alloy to obtain the parts to be connected. Step 2: Perform vacuum diffusion bonding on the components to be connected obtained in Step 1.

[0006] The above-mentioned method for diffusion bonding of nickel-based superalloys and niobium-based alloys with a high-entropy alloy interlayer is characterized in that the method for depositing the high-entropy alloy interlayer in step one is as follows: the high-entropy alloy ingot is vacuum induction arc melted multiple times, machined into a sputtering target, and then magnetron sputtered on the substrate to be welded to form a high-entropy alloy interlayer.

[0007] The vacuum induction arc melting process of this invention involves more than two cycles.

[0008] The above-mentioned method for diffusion bonding of nickel-based superalloy and niobium-based alloy in a high-entropy alloy interlayer is characterized in that the magnetron sputtering process is as follows: pre-sputtering for 15 min to 30 min, followed by deposition for 2 h to 5 h at a sample stage rotation speed of 15 rpm to 25 rpm. The parameters for the magnetron sputtering are: the background vacuum level of the sputtering chamber is no greater than 8 × 10⁻⁶. -5 Pa, argon flow rate 20sccm~30sccm, working pressure 0.6Pa~1Pa, sputtering power 100W~150W.

[0009] This invention removes impurities and oxide layers from the target surface through pre-sputtering; ensures the uniformity of the intermediate layer film composition by controlling the rotation speed of the sample stage; and controls the thickness of the high-entropy alloy intermediate layer from 5μm to 30μm by adjusting the deposition time to 2h to 5h.

[0010] The above-mentioned method for diffusion bonding of nickel-based superalloys and niobium-based alloys using a high-entropy alloy interlayer is characterized in that the material of the high-entropy alloy interlayer in step one is one of CoCrFeNiNb1.5, TiZrHfNbAl0.5, and NiCrCoFeAl.

[0011] The above-mentioned method for diffusion bonding of nickel-based superalloys and niobium-based alloys using a high-entropy alloy interlayer is characterized in that the materials of the high-entropy alloy interlayer and the substrate correspond, with CoCrFeNiNb1.5 and TiZrHfNbAl0.5 corresponding to niobium-based alloys and NiCrCoFeAl corresponding to nickel-based superalloys.

[0012] This invention avoids cracking of the film and substrate caused by interface mismatch and residual stress by matching the material of the high-entropy alloy intermediate layer with that of the substrate.

[0013] The above-mentioned method for diffusion bonding of a high-entropy alloy interlayer between a nickel-based superalloy and a niobium-based alloy is characterized in that, in step one, the mass content of Ni element in the nickel-based superalloy is ≥50%, and the mass content of Nb element in the niobium-based alloy is ≥50%.

[0014] The above-mentioned method for diffusion bonding of nickel-based superalloy and niobium-based alloy in a high-entropy alloy interlayer is characterized in that, in step one, the surfaces of the base materials to be welded are all pretreated, and then a base material is selected as a substrate for deposition; the specific method of the pretreatment is as follows: mechanical polishing and chemical polishing are performed sequentially until Ra≤1.5μm, and ultrasonic cleaning is performed sequentially using ethanol, acetone and deionized water as media.

[0015] The above-mentioned method for diffusion bonding of nickel-based superalloys and niobium-based alloys in a high-entropy alloy interlayer is characterized in that the base material in step one is a cylinder formed by slow wire EDM, and the welding surface of the base material is the end face of the cylinder.

[0016] This invention improves the connection quality by processing the base material into a cylinder, which ensures uniform stress on the axially pressurized sample.

[0017] The above-mentioned method for diffusion bonding of nickel-based superalloys and niobium-based alloys using a high-entropy alloy interlayer is characterized in that the thickness of the high-entropy alloy interlayer in step one is 5μm~30μm.

[0018] The above-described method for diffusion bonding of a nickel-based superalloy and a niobium-based alloy in a high-entropy alloy interlayer is characterized in that the vacuum diffusion parameters in step two are: vacuum degree 5 × 10⁻⁶. -2 Below MPa, temperature 900℃~1200℃, pressure 5MPa~50MPa, duration 2h~5h, heating rate ≤5℃ / min, cooling rate ≤5℃ / min.

[0019] Compared with the prior art, the present invention has the following advantages: 1. This invention employs magnetron sputtering to introduce a high-entropy alloy interlayer. An interlayer with a nanocrystalline structure is introduced onto the substrate surface to be welded. The nanocrystalline structure can reduce the roughness of the surface to be welded and improve the diffusion bonding efficiency. At the same time, the high volume fraction of grain boundaries and nanoscale grains of the nanocrystalline structure can further enhance the mechanical properties of the interlayer. The high-entropy alloy interlayer has a hysteresis diffusion effect and good room temperature and high temperature performance, which gives it unique advantages in diffusion bonding of nickel-based superalloys and niobium-based alloys.

[0020] 2. By selecting a high-entropy alloy with specific composition and proportion system, this invention can effectively hinder atomic diffusion and reaction between the base materials to be welded. At the same time, the alloy system has excellent room temperature and high temperature strength and ductility, which can ensure the performance of the joint.

[0021] 3. This invention strictly controls the heating / cooling rate of diffusion bonding to avoid film cracking caused by excessive difference in thermal expansion coefficients; at the same time, it strictly controls the vacuum degree, bonding temperature, bonding time and bonding pressure during the diffusion bonding process to reduce interface pores and inclusions, thereby obtaining a diffusion bonding component with a tight interface.

[0022] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the process of diffusion bonding between nickel-based superalloy and niobium-based alloy in the high-entropy alloy intermediate layer of the present invention.

[0024] Figure 2 These are microscopic morphology images of the cross-section of the high-entropy alloy intermediate layer in Examples 1-3 of this invention.

[0025] Figure 3 These are microscopic morphology diagrams of the cross-sections of the diffusion connectors in Embodiments 1-3 of the present invention. Detailed Implementation

[0026] Example 1 like Figure 1 As shown, the method in this embodiment includes the following steps: Step 1: Both Nb521 niobium-based alloy and GH3230 nickel-based alloy are machined into φ15mm×5mm cylinders using slow wire EDM. The upper and lower surfaces of the two cylinders are mechanically polished and chemically polished to Ra=1.5μm, respectively. Then, they are ultrasonically cleaned with ethanol, acetone, and deionized water in sequence. The raw materials are prepared according to the element atomic ratio Ti:Zr:Hf:Nb:Al=1:1:1:1:0.5. The materials are repeatedly melted in a vacuum induction arc furnace for 7 times to produce an ingot weighing 400g. Then, the ingot is machined into a φ60mm×5mm TiZrHfNbAl0.5 high-entropy alloy. Using a cylindrical substrate made of Nb521 niobium-based alloy as the substrate and a TiZrHfNbAl0.5 high-entropy alloy as the sputtering target, magnetron sputtering is performed on the substrate end face; the magnetron sputtering is performed in a sputtering chamber with a background vacuum of 5×10⁻⁶. -5 The process was carried out under the conditions of Pa, argon flow rate of 20 sccm, working pressure of 0.7 Pa, and sputtering power of 150 W. First, pre-sputtering was performed for 30 min, then the sample stage was started to rotate at 15 rpm, the substrate baffle was opened, and a TiZrHfNbAl0.5 high-entropy alloy intermediate layer with a thickness of 5 μm was prepared after 2 h of deposition. The components to be connected are assembled sequentially in the following order: GH3230 nickel-based superalloy / TiZrHfNbAl0.5 high-entropy alloy intermediate layer / Nb521 niobium-based alloy. Step 2: Place the component to be connected obtained in Step 1 into a vacuum diffusion furnace for vacuum diffusion, followed by furnace cooling to obtain the diffused connector; the parameters for the vacuum diffusion are: vacuum degree 5×10 -2 MPa, temperature 900℃, pressure 50MPa, connection time 4h, heating / cooling rate 5℃ / min.

[0027] Microscopic analysis was performed on the cross-sectional microstructure of the TiZrHfNbAl0.5 high-entropy alloy intermediate layer prepared in step one of this embodiment, such as... Figure 2 As shown in (a), the TiZrHfNbAl0.5 high-entropy alloy intermediate layer exhibits a typical columnar crystal structure with high density, good bonding with the substrate, and no obvious cracking. Microscopic analysis of the cross-section of the diffusion connector obtained in step two is shown in... Figure 3 As shown in (a), the TiZrHfNbAl0.5 high-entropy alloy intermediate layer has good diffusion bonding between the nickel-based superalloy and the niobium-based alloy interface, with no obvious pores or inclusions.

[0028] Example 2 like Figure 1 As shown, the method in this embodiment includes the following steps: Step 1: Both Nb-1Zr niobium-based alloy and GH3218 nickel-based alloy are machined into φ15mm×5mm cylinders using slow wire EDM. The upper and lower surfaces of the two cylinders are mechanically polished and chemically polished to Ra=0.7μm, respectively. Then, they are ultrasonically cleaned with ethanol, acetone, and deionized water in sequence. The raw materials are prepared according to the element atomic ratio Co:Cr:Fe:Ni:Nb=1:1:1:1:1.5. The materials are repeatedly melted in a vacuum induction arc furnace for 7 times to produce an ingot weighing 400g. Then, the ingot is machined into a φ60mm×5mm CoCrFeNiNb1.5 high-entropy alloy. Using a cylindrical substrate made of Nb-1Zr niobium-based alloy as the substrate and a CoCrFeNiNb1.5 high-entropy alloy as the sputtering target, magnetron sputtering is performed on the substrate end face; the magnetron sputtering is performed in a sputtering chamber with a base vacuum of 6×10⁻⁶. -5 The process was carried out under the conditions of Pa, argon flow rate of 30 sccm, working pressure of 1 Pa, and sputtering power of 100 W. First, pre-sputtering was performed for 20 min, then the sample stage was started to rotate at 25 rpm, the substrate baffle was opened, and a 30 μm thick CoCrFeNiNb1.5 high-entropy alloy intermediate layer was prepared after 5 h of deposition. The components to be connected are assembled sequentially in the following order: GH3218 nickel-based superalloy / CoCrFeNiNb1.5 high-entropy alloy intermediate layer / Nb-1Zr niobium-based alloy. Step 2: Place the component to be connected obtained in Step 1 into a vacuum diffusion furnace for vacuum diffusion, followed by furnace cooling to obtain the diffused connector; the parameters for the vacuum diffusion are: vacuum degree 5×10 -2 MPa, temperature 1200℃, pressure 5MPa, connection time 2h, heating / cooling rate 5℃ / min.

[0029] Microscopic analysis was performed on the cross-sectional microstructure of the CoCrFeNiNb high-entropy alloy intermediate layer prepared in step one of this embodiment, such as... Figure 2 As shown in (b), the intermediate layer of the CoCrFeNiNb high-entropy alloy exhibits a typical columnar crystal structure with high density, good adhesion to the substrate, and no obvious cracking. Microscopic analysis of the cross-section of the diffusion connector obtained in step two is shown in... Figure 3 As shown in (b), the CoCrFeNiNb high-entropy alloy intermediate layer has good diffusion bonding between the nickel-based superalloy and the niobium-based alloy interface, with no obvious pores or inclusions.

[0030] Example 3 like Figure 1 As shown, the method in this embodiment includes the following steps: Step 1: Both Nb521 niobium-based alloy and GH3230 nickel-based alloy are machined into φ15mm×5mm cylinders using slow wire EDM. The upper and lower surfaces of the two cylinders are mechanically polished and chemically polished to Ra=1.0μm, respectively. Then, they are ultrasonically cleaned with ethanol, acetone, and deionized water in sequence. The raw materials are prepared according to the atomic ratio of Ni:Cr:Co:Fe:Al=1:1:1:1:1 and repeatedly melted in a vacuum induction arc furnace 7 times to produce an ingot weighing 400g. Then, it is machined into a φ60mm×5mm NiCrCoFeAl high-entropy alloy. Using a cylindrical substrate made of GH3230 nickel-based alloy as the substrate and a NiCrCoFeAl high-entropy alloy as the sputtering target, magnetron sputtering is performed on the substrate end face; the magnetron sputtering is performed in a sputtering chamber with a background vacuum of 8×10⁻⁶. -5 The process was carried out under the conditions of Pa, argon flow rate of 25 sccm, working pressure of 0.6 Pa, and sputtering power of 130 W. First, pre-sputtering was performed for 15 min, then the sample stage was started to rotate at 20 rpm, the substrate baffle was opened, and a NiCrCoFeAl high-entropy alloy intermediate layer with a thickness of 5 μm was prepared after 2.5 h of deposition. The components to be connected are assembled in the following order: GH3230 nickel-based superalloy / NiCrCoFeAl high-entropy alloy intermediate layer / Nb521 niobium-based alloy. Step 2: Place the component to be connected obtained in Step 1 into a vacuum diffusion furnace for vacuum diffusion, followed by furnace cooling to obtain the diffused connector; the parameters for the vacuum diffusion are: vacuum degree 5×10 -2 MPa, temperature 1000℃, pressure 20MPa, connection time 5h, heating / cooling rate 5℃ / min.

[0031] Microscopic analysis was performed on the cross-sectional microstructure of the NiCrCoFeAl high-entropy alloy intermediate layer prepared in step one of this embodiment, such as... Figure 2 As shown in (c), the NiCrCoFeAl high-entropy alloy intermediate layer exhibits a typical columnar crystal structure with high density, good adhesion to the substrate, and no obvious cracking. Microscopic analysis of the cross-section of the diffusion connector obtained in step two is performed, as shown... Figure 3 As shown in (c), the NiCrCoFeAl high-entropy alloy intermediate layer has good diffusion bonding between the nickel-based superalloy and the niobium-based alloy interface, with no obvious pores or inclusions.

[0032] The above description is merely a preferred embodiment of the present invention and does not constitute any limitation on the present invention. Any simple modifications, alterations, or equivalent structural transformations made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for diffusion bonding of a nickel-based superalloy and a niobium-based alloy in a high-entropy alloy interlayer, characterized in that, The method includes the following steps: Step 1: The base materials are nickel-based superalloys and niobium-based alloys. Select a nickel-based superalloy or niobium-based alloy as the substrate, and use physical vapor deposition to deposit a high-entropy alloy intermediate layer on the surface to be welded on the substrate. Then assemble them in the order of nickel-based superalloy / high-entropy alloy intermediate layer / niobium-based alloy to obtain the parts to be connected. Step 2: Perform vacuum diffusion bonding on the components to be connected obtained in Step 1.

2. The method for diffusion bonding of nickel-based superalloys and niobium-based alloys in a high-entropy alloy interlayer according to claim 1, characterized in that, The method for depositing the high-entropy alloy intermediate layer in step one is as follows: the high-entropy alloy ingot is vacuum induction arc melted multiple times, machined into a sputtering target, and then magnetron sputtered on the substrate to be welded to form the high-entropy alloy intermediate layer.

3. The method for diffusion bonding of nickel-based superalloys and niobium-based alloys in a high-entropy alloy interlayer according to claim 2, characterized in that, The magnetron sputtering process is as follows: pre-sputtering for 15 min to 30 min, followed by deposition for 2 h to 5 h at a stage rotation speed of 15 rpm to 25 rpm; The parameters for the magnetron sputtering are: the background vacuum level of the sputtering chamber is no greater than 8 × 10⁻⁶. -5 Pa, argon flow rate 20sccm~30sccm, working pressure 0.6Pa~1Pa, sputtering power 100W~150W.

4. The method for diffusion bonding of nickel-based superalloys and niobium-based alloys in a high-entropy alloy interlayer according to claim 1, characterized in that, The high-entropy alloy intermediate layer mentioned in step one is made of one of the following materials: CoCrFeNiNb1.5, TiZrHfNbAl0.5, and NiCrCoFeAl.

5. The method for diffusion bonding of nickel-based superalloys and niobium-based alloys in a high-entropy alloy interlayer according to claim 4, characterized in that, The materials of the high-entropy alloy intermediate layer correspond to those of the substrate: CoCrFeNiNb1.5 and TiZrHfNbAl0.5 correspond to niobium-based alloys, and NiCrCoFeAl corresponds to nickel-based high-temperature alloys.

6. The method for diffusion bonding of nickel-based superalloys and niobium-based alloys in a high-entropy alloy interlayer according to claim 1, characterized in that, In step one, the mass content of Ni in the nickel-based superalloy is ≥50%, and the mass content of Nb in the niobium-based alloy is ≥50%.

7. The method for diffusion bonding of nickel-based superalloys and niobium-based alloys in a high-entropy alloy interlayer according to claim 1, characterized in that, In step one, the surfaces of the base materials to be welded are all pretreated, and then a base material is selected as the substrate for deposition. The specific method of pretreatment is as follows: mechanical polishing and chemical polishing are performed sequentially until Ra≤1.5μm, and ultrasonic cleaning is performed sequentially using ethanol, acetone and deionized water as media.

8. The method for diffusion bonding of nickel-based superalloys and niobium-based alloys in a high-entropy alloy interlayer according to claim 1, characterized in that, In step one, the base material is a cylinder processed by slow wire EDM, and the surface of the base material to be welded is the end face of the cylinder.

9. The method for diffusion bonding of nickel-based superalloys and niobium-based alloys in a high-entropy alloy interlayer according to claim 1, characterized in that, The thickness of the high-entropy alloy intermediate layer mentioned in step one is 5μm~30μm.

10. The method for diffusion bonding of nickel-based superalloys and niobium-based alloys in a high-entropy alloy interlayer according to claim 1, characterized in that, The parameters for vacuum diffusion in step two are: vacuum degree 5 × 10⁻⁶. -2 Below MPa, temperature 900℃~1200℃, pressure 5MPa~50MPa, duration 2h~5h, heating rate ≤5℃ / min, cooling rate ≤5℃ / min.

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