Vacuum diffusion bonding method for nickel-based superalloy and niobium alloy

Abstract

The invention relates to a vacuum diffusion bonding method for nickel-based superalloy and niobium alloy, and aims to solve the problems that the existing nickel-based superalloy and niobium alloy are difficult to bond and a brittle phase is easy to generate. The vacuum diffusion method comprises the steps that firstly, the surfaces of the nickel-based high-temperature alloy and the niobium alloy to be welded are polished and ultrasonically cleaned; preparing a Ti-Mo-Cr intermediate layer or a V-Cr intermediate layer, and placing the intermediate layer between the cleaned surfaces to be subjected to diffusion bonding of the nickel-based superalloy and the niobium alloy to obtain an accessory to be welded; thirdly, the to-be-welded part is placed in a high-temperature vacuum diffusion furnace to be vacuumized; and 4, applying working pressure, and controlling the bonding temperature to be 900-1300 DEG C for diffusion bonding. According to the present invention, the compound components of the joint can be changed through the intermediate layer, the generation of the brittle phase is limited, the bonding between atoms can be achieved, the reliable connection is formed, and the relatively high joint strength can be obtained.

Description

Technical Field

[0001] The invention belongs to the technical field of metal welding, and in particular relates to a vacuum diffusion connection method for a nickel-based high-temperature alloy and a niobium alloy. Background Art

[0002] Due to the comprehensive strengthening of elements such as Cr, Co, W, and Ti, nickel-based high-temperature alloys have high thermal strength and can be used for a long time at temperatures below 900°C. They are often used to manufacture hot end parts of aerospace engines and gas turbines, such as combustion chambers, turbine blades and other parts. As a new generation of aerospace materials, niobium alloys have excellent high-temperature strength and plasticity, and the maximum use temperature can reach 1800°C. The alloy can also be used for a short time at 2000°C. The application range is extended from binary liquid rocket engines to various rocket engine throats and diffusers, parts for flight performance aircraft, aerospace rivets, valves, automatic control engines for lunar exploration projects, and can also be used for gas generator valve components, high-temperature resistant pipe fittings and valves. However, the welding compatibility of these two materials is poor, and traditional welding methods are prone to joint performance degradation, such as embrittlement, cracks and other problems. Therefore, it is of great practical significance to develop a welding technology that can effectively connect these two materials and maintain their performance. Therefore, achieving high-quality connection between nickel-based high-temperature alloys and niobium alloys is of great significance to the development of the aviation and aerospace industries.

[0003] Some scholars have used the refractory metal Nb+Ni intermediate layer to diffusely bond the nickel-based high-temperature alloy GH4169 and Ti2AlNb. The weld structure can be regarded as Nb+Ni diffusion bonding with GH4169 and Ti2AlNb separately. Through the analysis of the joint structure, it was found that Fe-Ni-Cr solid solution, Ni3Nb and Ni6Nb7 were generated near GH4169. In the shear test, it was found that the joint fracture mainly broke along the Ni6Nb7 layer between Ni3Nb and Ni layer. (Qian Jinwen, Li Jinglong, Hou Jinbao, etc. Influence of Nb+Ni intermediate layer on the structure and performance of diffusion bonded joints of Ti2AlNb and GH4169. Journal of Aeronautical Materials, 2009, 29(01):57-62.). When Li Haixin et al. used a Ti / Nb composite intermediate layer to diffusely bond TiAl and GH4099 alloy (Li Haixin, Wei Hongmei, He Peng et al. Interface structure and joint strength of TiAl / Ti / Nb / GH99 diffusion bonded joints. Journal of Welding, 2012, 33(9): 9-12, 113.), they found that when the connection temperature was greater than 900°C, a Ni6Nb7 reaction layer was generated at the interface, which had an adverse effect on the joint strength. When the thickness of the Ni6Nb7 reaction layer was large, cracks would be generated under the action of stress in the connection joint. At the same time, joint fracture also occurred in the Ni6Nb7 reaction layer during the shear test.

[0004] In summary, there are few publicly reported methods for connecting nickel-based high-temperature alloys and niobium alloys, but the idea of ​​connecting niobium alloys using an intermediate layer is feasible. The high melting point, low thermal conductivity and complex composition of niobium alloys, as well as the good high-temperature strength of nickel-based alloys, make it difficult for them to undergo plastic deformation during diffusion welding, which greatly hinders their diffusion connection. In addition, brittle intermetallic compounds Ni6Nb7 are prone to appear in the diffusion zone, which seriously restricts the mechanical properties of the joints and even causes cracks along the brittle layer after welding, making it impossible to obtain a strong joint, and the strength is low both at room temperature and at high temperature. Therefore, it is urgent to develop a new connection method to achieve high-quality connection between nickel-based high-temperature alloys and niobium alloy welded joints with sufficient strength to meet service requirements. Summary of the invention

[0005] In order to solve the problems of difficulty in connecting the existing nickel-based high-temperature alloy and the niobium alloy and easy generation of brittle phase, the present invention provides a new idea of ​​using an intermediate layer, which can achieve efficient combination of the nickel-based high-temperature alloy and the niobium alloy at the microscopic level, form a solid solution joint during the diffusion connection process, avoid the generation of a large amount of Ni6Nb7 brittle phase during the element diffusion process, ensure the mechanical properties of the welded joint, and provide a method for vacuum diffusion connection of the nickel-based high-temperature alloy and the niobium alloy.

[0006] The vacuum diffusion bonding method of the nickel-based high-temperature alloy and the niobium alloy of the present invention is implemented according to the following steps:

[0007] 1. Grinding the surfaces of the nickel-based high-temperature alloy and niobium alloy to be welded, and then ultrasonically cleaning them to obtain the cleaned nickel-based high-temperature alloy and niobium alloy;

[0008] 2. Prepare a Ti-Mo-Cr intermediate layer or a V-Cr intermediate layer, and place the intermediate layer between the cleaned nickel-based high-temperature alloy and the surface to be diffused and bonded of the niobium alloy. When the Ti-Mo-Cr intermediate layer is used, the Ti metal (foil) of the intermediate layer contacts the surface to be diffused and bonded of the niobium alloy, and the Cr metal (foil) of the intermediate layer contacts the surface to be diffused and bonded of the nickel-based high-temperature alloy;

[0009] When a V-Cr intermediate layer is used, the V metal (foil) of the intermediate layer contacts the surface of the niobium alloy to be diffused and bonded, and the Cr metal (foil) of the intermediate layer contacts the surface of the nickel-based high-temperature alloy to be diffused and bonded;

[0010] Applying clamping pressure to the nickel-based high-temperature alloy, the intermediate layer and the niobium alloy to be welded to obtain an assembly to be welded;

[0011] 3. Place the parts to be welded in a high-temperature vacuum diffusion furnace and evacuate to the working vacuum degree;

[0012] 4. Heat up, apply working pressure, control the connection temperature to 900-1300°C for diffusion connection, keep warm and then cool to room temperature to complete vacuum diffusion connection of nickel-based high-temperature alloy and niobium alloy.

[0013] The present invention proposes a method for diffusion bonding of a nickel-based high-temperature alloy and a niobium alloy, using Ti-Mo-Cr or V-Cr as an intermediate layer. Taking the Ti-Mo-Cr intermediate layer as an example, in the high-temperature bonding diffusion process, elements such as Ni, Cr, and Nb diffuse under a concentration gradient. The presence of the intermediate layer changes the compound composition of the joint, avoids the formation of intermetallic compounds between the niobium alloy and the nickel-based alloy, and achieves a good combination between the two through a solid solution structure. During the reaction process, Ni and Cr, Cr and Mo, Mo and Ti, and Ti and Nb can achieve a large solid solution, form a solid solution connection interface under a certain temperature, time and pressure, and obtain a strong metallurgical bond by optimizing the diffusion bonding process. The Ti-Mo-Cr intermediate layer can block the diffusion of high-temperature alloy elements, limit the generation of brittle phases, and can achieve bonding between atoms to form a reliable connection. The residual stress generated during the connection process is reduced, so that a relatively high joint strength can be obtained, and the mechanical properties of the joint are guaranteed.

[0014] The vacuum diffusion connection method of the nickel-based high-temperature alloy and the niobium alloy of the present invention is simple and easy to operate, enriches the types of connection technologies of the nickel-based high-temperature alloy and the niobium alloy, and has broad application prospects and great practical value. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a low-magnification backscattered electron photograph of the interface structure of the GH4099 alloy / Nb521 alloy joint obtained under the conditions of 1200°C / 120min / 30MPa using a Ti-Mo-Cr intermediate layer with a total thickness of 460μm in Example 1;

[0016] Figure 2 This is a high-magnification backscattered electron photograph of the interface structure of the GH4099 alloy / Nb521 alloy joint near the Nb521 alloy side obtained under the conditions of 1200°C / 120min / 30MPa using a Ti-Mo-Cr intermediate layer with a total thickness of 460μm in Example 1;

[0017] Figure 3 The backscattered electron photo and energy spectrum scanning photo of the GH4099 alloy / Nb521 alloy joint near the Nb521 alloy side obtained under the conditions of 1200°C / 120min / 30MPa using a Ti-Mo-Cr intermediate layer with a total thickness of 460μm in Example 1;

[0018] Figure 4This is a backscattered electron photograph of the connection joint close to the Nb521 alloy side obtained by the V-Cr intermediate layer in Example 2 under the conditions of 1150°C-120min-30MPa;

[0019] Figure 5 This is the EDS analysis spectrum of the connection joint close to the Nb521 alloy side obtained by the V-Cr intermediate layer in Example 2 under the conditions of 1150°C-120min-30MPa;

[0020] Figure 6 This is a backscattered electron photograph of the connection joint obtained by the V-Cr intermediate layer in Example 2 under the conditions of 1150°C-120min-30MPa. DETAILED DESCRIPTION

[0021] Specific implementation method 1: The vacuum diffusion bonding method of nickel-based high-temperature alloy and niobium alloy in this implementation method is implemented according to the following steps:

[0022] 1. Grinding the surfaces of the nickel-based high-temperature alloy and niobium alloy to be welded, and then ultrasonically cleaning them to obtain the cleaned nickel-based high-temperature alloy and niobium alloy;

[0023] 2. Prepare a Ti-Mo-Cr intermediate layer or a V-Cr intermediate layer, and place the intermediate layer between the cleaned nickel-based high-temperature alloy and the surface to be diffused and bonded of the niobium alloy. When the Ti-Mo-Cr intermediate layer is used, the Ti metal (foil) of the intermediate layer contacts the surface to be diffused and bonded of the niobium alloy, and the Cr metal (foil) of the intermediate layer contacts the surface to be diffused and bonded of the nickel-based high-temperature alloy;

[0024] When a V-Cr intermediate layer is used, the V metal (foil) of the intermediate layer contacts the surface of the niobium alloy to be diffused and bonded, and the Cr metal (foil) of the intermediate layer contacts the surface of the nickel-based high-temperature alloy to be diffused and bonded;

[0025] Applying clamping pressure to the nickel-based high-temperature alloy, the intermediate layer and the niobium alloy to be welded to obtain an assembly to be welded;

[0026] 3. Place the parts to be welded in a high-temperature vacuum diffusion furnace and evacuate to the working vacuum degree;

[0027] 4. Heating, applying working pressure, controlling the connection temperature to 900-1300°C for diffusion bonding, cooling to room temperature after insulation, and completing vacuum diffusion bonding of the nickel-based high-temperature alloy and the niobium alloy.

[0028] In step 2 of this embodiment, the intermediate layer is placed between the surfaces of the two nickel-based high-temperature alloys and niobium alloys to be diffusely connected, and the layers are stacked in the order of niobium alloy-Ti-Mo-Cr-nickel-based high-temperature alloy, and a certain pressure is applied.

[0029] This embodiment adopts a method of vacuum diffusion bonding of nickel-based high-temperature alloy and niobium alloy by Ti-Mo-Cr intermediate layer, and vacuum diffusion bonding of nickel-based high-temperature alloy and niobium alloy is performed by adding an intermediate layer between the alloy base materials. This embodiment designs a Ti-Mo-Cr solid solution joint. During the diffusion bonding process, elements such as Ni, Cr, and Nb diffuse under a concentration gradient. The presence of the intermediate layer changes the compound composition of the joint, limits the generation of brittle phases, and can achieve bonding between atoms to form a reliable connection. The residual stress generated during the connection process is reduced, and a relatively high joint strength can be obtained to ensure the mechanical properties of the joint.

[0030] Specific implementation method 2: The difference between this implementation method and specific implementation method 1 is that the nickel-based high-temperature alloy described in step 1 is GH nickel-based high-temperature alloy, K nickel-based casting high-temperature alloy, powder metallurgy nickel-based high-temperature alloy, Inconel alloy or Monel alloy.

[0031] Specific implementation method three: This implementation method is different from specific implementation methods one or two in that the niobium alloy described in step one is Nb521 alloy, Nb-33Ta-0.75Zr alloy, C-103 alloy, Scb-291 alloy, Nb-0.75Zr alloy, Nb-10Ti alloy or pure niobium.

[0032] Specific implementation method 4: This implementation method is different from specific implementation methods 1 to 3 in that in step 1, 400#, 800#, 1200#, 1500#, 2000# and 3000# silicon carbide water-abrasive papers are used in sequence to grind the surfaces of the nickel-based high-temperature alloy and niobium alloy to be welded.

[0033] Specific embodiment 5: This embodiment is different from any one of specific embodiments 1 to 4 in that in step 2, Ti metal foil, Mo metal foil and Cr metal foil are stacked in sequence to prepare a Ti-Mo-Cr intermediate layer, or Ti metal foil, Mo metal foil and Cr metal foil are stacked in sequence and then vacuum diffused at a temperature of 1000° C. to 1400° C. to prepare a Ti-Mo-Cr intermediate layer;

[0034] The V-Cr intermediate layer is prepared by stacking a V metal foil and a Cr metal foil in sequence, or by stacking a V metal foil and a Cr metal foil in sequence and then performing vacuum diffusion at a temperature of 1000°C to 1400°C to prepare the V-Cr intermediate layer.

[0035] In this embodiment, the purity of the Ti metal foil, the Mo metal foil, the V metal foil and the Cr metal foil are all greater than 99.99%.

[0036] In this embodiment, the Ti-Mo-Cr intermediate layer can be directly stacked, or stacked and then vacuum diffused. The V-Cr intermediate layer can also be directly stacked, or stacked and then vacuum diffused.

[0037] Specific implementation method 6: The difference between this implementation method and any one of specific implementation methods 1 to 5 is that the thickness of the Ti—Mo—Cr intermediate layer or the V—Cr intermediate layer described in step 2 is 50 to 500 μm.

[0038] Specific implementation method 7: The difference between this implementation method and any one of specific implementation methods 1 to 6 is that the working pressure applied in step 4 is 5 to 50 MPa.

[0039] Specific implementation eight: This implementation is different from any one of specific implementations one to seven in that the heating rate in step four is 5°C / min to 15°C / min.

[0040] Specific embodiment 9: The difference between this embodiment and any one of specific embodiments 1 to 8 is that in step 4, the connection temperature is 900-1300° C. and the temperature is kept for 30-180 minutes for diffusion connection.

[0041] Specific implementation method ten: The difference between this implementation method and any one of specific implementation methods one to nine is that the cooling rate in step four is controlled to be 2° C. / min to 10° C. / min.

[0042] Embodiment 1: The vacuum diffusion bonding method of nickel-based high-temperature alloy and niobium alloy in this embodiment is implemented according to the following steps:

[0043] 1. Mechanically grinding and polishing the surfaces of the GH4099 alloy and Nb521 alloy to be welded, respectively. The mechanical grinding is performed with 400#, 800#, 1500#, 2000# and 3000# SiC water-abrasive sandpaper in sequence. The welded parts after grinding are ultrasonically cleaned in anhydrous ethanol for 5 minutes to obtain the cleaned GH4099 alloy and Nb521 alloy to be welded.

[0044] 2. A Ti metal foil with a thickness of 30 μm, a Mo metal foil with a thickness of 30 μm, and a Cr metal foil with a thickness of 400 μm are stacked in sequence as an intermediate layer, and the intermediate layer is placed between the surfaces to be diffusely connected of two GH4099 high-temperature alloys and Nb521 alloys to be welded, and they are stacked in the order of Nb521 alloy-Ti-Mo-Cr-GH4099 high-temperature alloy, and clamping pressure is applied to obtain an assembly to be welded;

[0045] 3. Place the welded parts in the fixture of the high-temperature vacuum diffusion furnace and evacuate to a vacuum degree better than 5×10 -3 MPa;

[0046] 4. Control the heating rate to 10℃ / min, apply a working pressure of 30MPa, keep the temperature at 1200℃ for 120min, control the cooling rate to 5℃ / min to cool to room temperature, and complete the vacuum diffusion bonding of the nickel-based high-temperature alloy and the niobium alloy.

[0047] In this embodiment, the low-magnification and high-magnification backscattered electron photographs of the interface structure of the GH4099 high-temperature alloy / Nb521 alloy joint obtained under the conditions of 1200°C / 120min / 30MPa using a Ti-Mo-Cr intermediate layer with a total thickness of 460μm are shown in Figure 1. Figure 1 and Figure 2 shown.

[0048] Figure 3 This is the EDS spectrum analysis spectrum of the GH4099 high-temperature alloy / Nb521 alloy joint. It can be seen that the elements diffused with each other during the connection process, forming a good metallurgical bond. The Ti-Mo-Cr intermediate layer forms a solid solution joint, which effectively solves the problem of brittle phase when connecting niobium alloy and nickel-based high-temperature alloy, and avoids the problem of joint cracking directly along the brittle phase due to welding internal stress. In this embodiment, the intermediate layer is well connected to the parent material, and no obvious cracks and holes are found, so the joint quality and strength are relatively high.

[0049] Embodiment 2: The vacuum diffusion bonding method of nickel-based high-temperature alloy and niobium alloy in this embodiment is implemented according to the following steps:

[0050] 1. Mechanically grinding and polishing the surfaces of the GH4099 alloy and Nb521 alloy to be welded, respectively. The mechanical grinding is performed with 400#, 800#, 1500#, 2000# and 3000# SiC water-abrasive sandpaper in sequence. The welded parts after grinding are ultrasonically cleaned in anhydrous ethanol for 5 minutes to obtain the cleaned GH4099 alloy and Nb521 alloy to be welded.

[0051] 2. Stacking a 50 μm thick V metal foil and a 400 μm thick Cr metal foil in sequence as an intermediate layer, placing the intermediate layer between the two surfaces of the GH4099 high-temperature alloy and the Nb521 alloy to be diffusely connected, stacking them in the order of Nb521 alloy-V-Cr-GH4099 high-temperature alloy, applying clamping pressure, and obtaining an assembly to be welded;

[0052] 3. Place the welded parts in the fixture of the high-temperature vacuum diffusion furnace and evacuate to a vacuum degree better than 5×10 -3 MPa;

[0053] 4. Control the heating rate to 10℃ / min, apply a working pressure of 30MPa, keep the temperature at 1150℃ for 120min, control the cooling rate to 5℃ / min to cool to room temperature, and complete the vacuum diffusion bonding of the nickel-based high-temperature alloy and the niobium alloy.

[0054] Figure 4 In order to connect the backscattered electron phase of the joint close to the Nb521 alloy side using a V-Cr intermediate layer at 1150℃-120min-30MPa, the connection effect on this side of the joint is good.

[0055] In order to analyze the microstructure of the solid solution joint, EDS analysis was carried out on the side of the joint close to the Nb521 alloy. The analysis results are shown in Figure 5 The V metal foil has a complete shape, a straight interface, and good contact with the Cr metal interface. The elements in the joint diffuse significantly, and no obvious cracks, holes, or other defects are found at the interface.

[0056] Figure 6 This is the backscattered electron phase of the V-Cr joint close to the GH4099 alloy side at 1150℃-120min-30MPa.

Claims

1. A vacuum diffusion bonding method for nickel-based high-temperature alloys and niobium alloys, characterized in that The vacuum diffusion connection method is implemented according to the following steps:

1. Grinding the surfaces of the nickel-based high-temperature alloy and niobium alloy to be welded, and then ultrasonically cleaning them to obtain the cleaned nickel-based high-temperature alloy and niobium alloy; 2. Prepare a Ti-Mo-Cr intermediate layer or a V-Cr intermediate layer, and place the intermediate layer between the cleaned nickel-based high-temperature alloy and the surface to be diffused and bonded of the niobium alloy. When a Ti-Mo-Cr intermediate layer is used, the Ti metal of the intermediate layer contacts the surface to be diffused and bonded of the niobium alloy, and the Cr metal of the intermediate layer contacts the surface to be diffused and bonded of the nickel-based high-temperature alloy. When a V-Cr intermediate layer is used, the V metal of the intermediate layer contacts the surface of the niobium alloy to be diffused and bonded, and the Cr metal of the intermediate layer contacts the surface of the nickel-based high-temperature alloy to be diffused and bonded; Applying clamping pressure to the nickel-based high-temperature alloy, the intermediate layer and the niobium alloy to be welded to obtain an assembly to be welded; 3. Place the parts to be welded in a high-temperature vacuum diffusion furnace and evacuate to the working vacuum degree; 4. Heating, applying working pressure, controlling the connection temperature to 900-1300°C for diffusion bonding, cooling to room temperature after insulation, and completing vacuum diffusion bonding of the nickel-based high-temperature alloy and the niobium alloy.

2. The vacuum diffusion bonding method of nickel-based high-temperature alloy and niobium alloy according to claim 1, characterized in that The nickel-based high-temperature alloy described in step 1 is GH nickel-based high-temperature alloy, K nickel-based casting high-temperature alloy, powder metallurgy nickel-based high-temperature alloy, Inconel alloy or Monel alloy.

3. The vacuum diffusion bonding method of nickel-based high-temperature alloy and niobium alloy according to claim 1, characterized in that The niobium alloy described in step 1 is Nb521 alloy, Nb-33Ta-0.75Zr alloy, C-103 alloy, Scb-291 alloy, Nb-0.75Zr alloy, Nb-10Ti alloy or pure niobium.

4. The vacuum diffusion bonding method of nickel-based high-temperature alloy and niobium alloy according to claim 1, characterized in that In step 1, 400#, 800#, 1200#, 1500#, 2000# and 3000# silicon carbide water-abrasive paper is used in sequence to grind the surfaces of the nickel-based high-temperature alloy and niobium alloy to be welded.

5. The vacuum diffusion bonding method of nickel-based high-temperature alloy and niobium alloy according to claim 1, characterized in that In step 2, Ti metal foil, Mo metal foil and Cr metal foil are stacked in sequence to prepare a Ti-Mo-Cr intermediate layer, or Ti metal foil, Mo metal foil and Cr metal foil are stacked in sequence and then vacuum diffused at a temperature of 1000° C. to 1400° C. to prepare a Ti-Mo-Cr intermediate layer; The V-Cr intermediate layer is prepared by stacking a V metal foil and a Cr metal foil in sequence, or by stacking a V metal foil and a Cr metal foil in sequence and then performing vacuum diffusion at a temperature of 1000°C to 1400°C to prepare the V-Cr intermediate layer.

6. The vacuum diffusion bonding method of nickel-based high-temperature alloy and niobium alloy according to claim 1, characterized in that The thickness of the Ti-Mo-Cr intermediate layer or the V-Cr intermediate layer in step 2 is 50 to 500 μm.

7. The vacuum diffusion bonding method of nickel-based high-temperature alloy and niobium alloy according to claim 1, characterized in that The working pressure applied in step 4 is 5 to 50 MPa.

8. The vacuum diffusion bonding method of nickel-based high-temperature alloy and niobium alloy according to claim 1, characterized in that The heating rate in step 4 is 5°C / min to 15°C / min.

9. The vacuum diffusion bonding method of nickel-based high-temperature alloy and niobium alloy according to claim 1, characterized in that In step 4, the connection temperature is 900-1300° C., and the temperature is kept for 30-180 minutes for diffusion connection.

10. The vacuum diffusion bonding method of nickel-based high-temperature alloy and niobium alloy according to claim 1, characterized in that In step 4, the cooling rate is controlled to be 2°C / min to 10°C / min.

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