Method for brazing titanium alloy and nickel-based superalloy by using composite interlayer

Abstract

The invention relates to a method for brazing titanium alloy and nickel-based superalloy, in particular to a method for brazing titanium alloy and nickel-based superalloy through a composite interlayer. The method aims at solving the technical problem that a large number of intermetallic compounds can be generated in the brazing process of titanium alloy and nickel alloy at present, and consequently the mechanical property is poor. According to the invention, Nb and Cu simple substances which are immiscible with each other are adopted, the Nb / Cu composite metal intermediate layer is obtained through a thermoplastic deformation connection method, Nb and Cu have no solubility in a phase diagram, and no intermetallic compound is generated; the prepared composite metal interlayer is clamped between two brazing filler metals to prevent interaction of elements so as to reduce generation of intermetallic compounds, no intermetallic compound is generated in a finally obtained joint, and the room-temperature shear strength of the joint can reach 272.3 MPa when heat preservation is conducted for 20 min under the brazing temperature condition of 960 DEG C.

Description

Technical Field

[0001] The invention relates to a method for brazing a titanium alloy and a nickel-based high-temperature alloy. Background Art

[0002] With the rapid development of the aviation industry, the design of hypersonic vehicles has further increased the performance requirements for aircraft engines. The thrust-to-weight ratio (thrust generated per unit of gravity) of an aircraft engine is a key indicator of its technical level and operational capabilities. It directly affects flight performance, including maximum speed, rate of climb, and lift limit. A significant improvement in the thrust-to-weight ratio of an aircraft engine often leads to the emergence of a new generation of hypersonic vehicles. In addition to advanced design technologies, improvements in the thrust-to-weight ratio of aircraft engines are strongly dependent on the development of advanced materials and manufacturing technologies. New materials with high-temperature resistance, high specific strength, high specific modulus, oxidation resistance, and flame retardancy are urgently needed for engine structural components. In recent years, titanium alloys, as a lightweight structural material widely used in the aerospace industry, have the advantages of low density, high specific strength, and excellent corrosion resistance. However, their maximum operating temperature is limited to approximately 600°C. As operating temperatures rise further, the thermal strength and thermal stability of titanium alloys become increasingly difficult to balance, and their oxidation resistance decreases dramatically, limiting their use in high-temperature aircraft engine components. Compared to titanium alloys, nickel-based superalloys have a large number of strengthening elements added to them, and have excellent high-temperature strength, stiffness, oxidation resistance, and good fatigue resistance. They are widely used in heat-resistant parts of various rocket engines, space shuttles, and other aircraft, and are now a commonly used structural material in high-temperature engine components. However, the high density of nickel-based superalloys limits the improvement of the engine's thrust-to-weight ratio. If titanium alloys and nickel-based superalloys can be connected, their shortcomings such as the difficulty of forming and processing can be overcome, and the respective advantages of the two materials can be brought into play, and their application range will be broader. Therefore, achieving a reliable connection between titanium alloys and nickel-based superalloys is of great engineering significance.

[0003] Currently, active brazing is the preferred method for joining ceramics and metals due to its simple operation process and wide adaptability to joint sizes and shapes. However, there are fewer reports on the brazing of titanium alloys and nickel alloys. This is mainly due to the large amount of intermetallic compounds generated during the brazing of dissimilar metals, which leads to high brittleness, easy fracture, poor impact resistance, and poor mechanical properties of the joints. Therefore, it is necessary to study and solve the problem of intermetallic compound generation during the brazing process. Summary of the Invention

[0004] The present invention aims to solve the technical problem that a large amount of intermetallic compounds are generated during the brazing process of titanium alloy and nickel alloy, resulting in poor mechanical properties, and provides a method for brazing titanium alloy and nickel-based high-temperature alloy using a composite intermediate layer.

[0005] The method of brazing titanium alloy and nickel-based high-temperature alloy using a composite intermediate layer of the present invention is carried out according to the following steps:

[0006] 1. Preparation of Nb / Cu composite intermediate layer:

[0007] ①. Grind the surfaces of the Nb sheet and Cu sheet with 600#, 1000#, 2000#, 3000#, and 5000# grit sandpaper to remove the surface oxide layer until the surface is bright;

[0008] ② Immerse the polished Nb and Cu sheets in acetone for ultrasonic cleaning, then rinse with anhydrous ethanol and blow dry.

[0009] ③. Lay the dried Nb sheet and Cu sheet together and place them in a thermal simulation tester at 600℃~1000℃ and a strain rate of 0.1s. -1 ~10s -1 High temperature compression was performed under the conditions of , with the pressing amount being 60% to 90%, and then air-cooled to room temperature to obtain a Nb / Cu composite intermediate layer;

[0010] 2. Polish the surfaces to be welded of the parent material titanium alloy and the parent material nickel-based high-temperature alloy with 200#, 400#, 600# and 800# metallographic sandpaper in sequence until the surface is bright; immerse the polished titanium alloy and nickel-based high-temperature alloy in acetone for ultrasonic cleaning, and then rinse with anhydrous ethanol and blow dry;

[0011] 3. Stack and assemble the two treated base materials, TiZrCuNi powder solder, Au-Ni solder and Nb / Cu composite intermediate layer in the form of titanium alloy-TiZrCuNi-Nb / Cu composite intermediate layer-AuNi-nickel-based high-temperature alloy, with the Nb in the composite intermediate layer located on the side of the TiZrCuNi powder solder;

[0012] 4. Place the above-mentioned brazing assembly in a vacuum brazing furnace with the titanium alloy at the top, and place a pressing block on the titanium alloy to ensure close contact between the base material and the brazing filler metal during the brazing process. Then evacuate the furnace, heat it to 300°C~310°C and keep it warm for 10min~15min, then heat it to 800°C~810°C, then heat it to the connection temperature of 960°C~980°C and keep it warm for 5min~20min, then cool it to 300°C~310°C, and finally turn off the power and cool it to room temperature with the furnace. The brazing of the titanium alloy and the nickel-based high-temperature alloy is completed.

[0013] The present invention uses mutually immiscible Nb and Cu elements to obtain a Nb / Cu composite metal interlayer through a thermoplastic deformation connection method. Nb and Cu have no solubility in the phase diagram, and no intermetallic compounds are produced. The prepared composite metal interlayer is sandwiched between two solders to block the interaction between the elements and reduce the production of intermetallic compounds. Finally, no intermetallic compounds are produced in the joint obtained. When the joint is kept at a brazing temperature of 960°C for 20 minutes, the room temperature shear strength of the joint can reach 272.3 MPa. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a schematic diagram of the assembly of the sample to be welded in step 3 of test 1;

[0015] Figure 2 The microstructure images of the joint were obtained for experiment three;

[0016] Figure 3 The fracture morphology of the joint obtained for experiment three. DETAILED DESCRIPTION

[0017] Specific embodiment 1: This embodiment is a method for brazing titanium alloy and nickel-based high-temperature alloy using a composite intermediate layer, which is specifically carried out in the following steps:

[0018] 1. Preparation of Nb / Cu composite intermediate layer:

[0019] ①. Grind the surfaces of the Nb sheet and Cu sheet with 600#, 1000#, 2000#, 3000#, and 5000# grit sandpaper to remove the surface oxide layer until the surface is bright;

[0020] ② Immerse the polished Nb and Cu sheets in acetone for ultrasonic cleaning, then rinse with anhydrous ethanol and blow dry.

[0021] ③. Lay the dried Nb sheet and Cu sheet together and place them in a thermal simulation tester at 600℃~1000℃ and a strain rate of 0.1s. -1 ~10s -1 High temperature compression was performed under the conditions of , with the pressing amount being 60% to 90%, and then air-cooled to room temperature to obtain a Nb / Cu composite intermediate layer;

[0022] 2. Polish the surfaces to be welded of the parent material titanium alloy and the parent material nickel-based high-temperature alloy with 200#, 400#, 600# and 800# metallographic sandpaper in sequence until the surface is bright; immerse the polished titanium alloy and nickel-based high-temperature alloy in acetone for ultrasonic cleaning, and then rinse with anhydrous ethanol and blow dry;

[0023] 3. Stack and assemble the two treated base materials, TiZrCuNi powder solder, Au-Ni solder and Nb / Cu composite intermediate layer in the form of titanium alloy-TiZrCuNi-Nb / Cu composite intermediate layer-AuNi-nickel-based high-temperature alloy, with the Nb in the composite intermediate layer located on the side of the TiZrCuNi powder solder;

[0024] 4. Place the above-mentioned brazing assembly in a vacuum brazing furnace with the titanium alloy at the top, and place a pressing block on the titanium alloy to ensure close contact between the base material and the brazing filler metal during the brazing process. Then evacuate the furnace, heat it to 300°C~310°C and keep it warm for 10min~15min, then heat it to 800°C~810°C, then heat it to the connection temperature of 960°C~980°C and keep it warm for 5min~20min, then cool it to 300°C~310°C, and finally turn off the power and cool it to room temperature with the furnace. The brazing of the titanium alloy and the nickel-based high-temperature alloy is completed.

[0025] Specific embodiment 2: This embodiment differs from specific embodiment 1 in that the thickness of the Nb sheet in step 1 is 0.3 mm, and the thickness of the Cu sheet is 1 mm. Other aspects are the same as those of specific embodiment 1.

[0026] Specific embodiment 3: This embodiment differs from specific embodiment 1 or 2 in that: in step 1②, the polished Nb sheet and Cu sheet are immersed in acetone for ultrasonic cleaning for 15 minutes. Other steps are the same as specific embodiment 1 or 2.

[0027] Specific embodiment 4: This embodiment differs from the specific embodiments 1 to 3 in that: in step 1 ③, the dried Nb sheet and the Cu sheet are bonded together and then placed in a thermal simulation test machine at 800°C and a strain rate of 5s -1 The Nb / Cu composite intermediate layer is obtained by high temperature compression under the conditions of 70% compression, followed by air cooling to room temperature. The rest is the same as the first to third embodiments.

[0028] Specific embodiment 5: This embodiment differs from specific embodiment 4 in that the base material titanium alloy in step 2 is TA15. Other aspects are the same as specific embodiment 4.

[0029] Specific embodiment 6: This embodiment differs from specific embodiment 5 in that the parent nickel-based high-temperature alloy in step 2 is K4648. Other aspects are the same as specific embodiment 5.

[0030] Specific embodiment 7: This embodiment differs from specific embodiment 6 in that in step 2, the polished titanium alloy and nickel-based high-temperature alloy are immersed in acetone for ultrasonic cleaning for 15 minutes, and then rinsed with anhydrous ethanol and blown dry. Other aspects are the same as specific embodiment 6.

[0031] Specific embodiment eight: This embodiment differs from specific embodiment seven in that the pressure provided by the pressing block in step four is 1×10 3 Pa. Other aspects are the same as those of the seventh embodiment.

[0032] Specific embodiment 9: This embodiment differs from specific embodiment 8 in that: in step 4, vacuum is drawn to 1.0×10 -3 Pa. Other aspects are the same as those in the eighth embodiment.

[0033] Specific embodiment 10: This embodiment differs from specific embodiment 9 in that in step 4, the temperature is raised to 300°C and held for 10 minutes, then raised to 800°C, and then raised to the connection temperature of 960°C and held for 20 minutes, and then lowered to 300°C. Finally, the power is turned off and the furnace is cooled to room temperature, completing the brazing of the titanium alloy and the nickel-based high-temperature alloy. The rest of the process is the same as specific embodiment 9.

[0034] The present invention is verified by the following test:

[0035] Test 1: This test is a method for brazing titanium alloy and nickel-based high-temperature alloy using a composite intermediate layer. The specific steps are as follows:

[0036] 1. Preparation of Nb / Cu composite intermediate layer:

[0037] ①. Grind the surfaces of the Nb sheet and the Cu sheet with 600#, 1000#, 2000#, 3000#, and 5000# grit sandpaper to remove the surface oxide layer until the surface is bright; the thickness of the Nb sheet is 0.3mm, and the thickness of the Cu sheet is 1mm;

[0038] ② Immerse the polished Nb and Cu sheets in acetone and ultrasonically clean them for 15 minutes, then rinse them with anhydrous ethanol and blow dry them.

[0039] ③. The dried Nb sheet and Cu sheet were bonded together and then placed in a Gleeble 1500 thermal simulation tester at 800°C and a strain rate of 5s. -1 The Nb / Cu composite intermediate layer was obtained by high temperature compression under the conditions of 70% compression and then air cooling to room temperature.

[0040] Second, the welding surfaces of the parent material titanium alloy TA15 and the parent material nickel-based high-temperature alloy K4648 were polished with 200#, 400#, 600# and 800# metallographic sandpaper in sequence until the surface was bright; the polished titanium alloy and nickel-based high-temperature alloy were immersed in acetone for ultrasonic cleaning for 15 minutes, and then rinsed with anhydrous ethanol and blown dry;

[0041] 3. The two treated base materials, TiZrCuNi powder solder, Au-Ni solder and Nb / Cu composite intermediate layer are stacked and assembled in the form of TA15-TiZrCuNi-Nb / Cu composite intermediate layer-AuNi-K4648 (as shown in FIG. Figure 1 As shown in the figure), Nb in the composite intermediate layer is located on the side of the TiZrCuNi powder solder;

[0042] 4. Place the above-mentioned brazing assembly in a vacuum brazing furnace with the titanium alloy at the top and place a pressing block on top of the titanium alloy to ensure close contact between the base material and the brazing filler metal during the brazing process. The pressure provided by the pressing block is 1×10 3 Pa, and then evacuated to 1.0×10 -3 Pa, then heat it to 300℃ at a heating rate of 10℃ / min and keep it for 10min, then heat it to 800℃ at a heating rate of 10℃ / min, then heat it to the connection temperature of 960℃ at a heating rate of 5℃ / min and keep it for 5min, then cool it to 300℃ at a cooling rate of 5℃ / min, finally turn off the power and cool it to room temperature with the furnace, thus completing the brazing of titanium alloy and nickel-based high-temperature alloy.

[0043] Experiment 2: This experiment differs from Experiment 1 in that in step 4, the temperature was raised to the connection temperature of 960°C at a rate of 5°C / min and held at that temperature for 10 minutes. Other steps were the same as Experiment 1.

[0044] Experiment 3: This experiment differs from Experiment 1 in that in step 4, the temperature was raised to the connection temperature of 960°C at a rate of 5°C / min and held at that temperature for 20 minutes. Other steps were the same as Experiment 1.

[0045] The mechanical properties of the joint were evaluated by tensile shear strength. The joint strengths obtained under different brazing temperatures, brazing filler metal compositions and holding times are shown in Table 1. When the joint was held at a brazing temperature of 960°C for 20 minutes (Test 3), the room temperature shear strength reached 272.3 MPa.

[0046] Table 1 Room temperature shear strength of joints

[0047]

[0048] Figure 2Microstructure images of the joint obtained for Test 3: Figure (a) shows the overall joint morphology, Figure (b) shows the weld morphology on the TA15 side, and Figure (c) shows the weld morphology on the K4648 side. As shown in Figure (a), the joint is dense and free of defects such as pores or cracks. Figure (b) shows that the weld on the TA15 side is primarily composed of black acicular phase A and dark gray phase B. Figure (c) shows that the weld on the K4648 side is primarily composed of gray phase C, a eutectic structure formed by black phase D and white phase E, and dark gray phase F.

[0049] right Figure 2 EDS tests were performed on each point in (b) and (c), and the analysis results are shown in Table 2. Figure 2 The black phase A in (b) has a higher content of Ti and Al elements, so it is speculated that this phase is an α-Ti phase; the dark gray phase B has a higher content of Zr and Nb elements than phase A. Since Zr and Nb elements are both β-Ti stabilizing elements, it is speculated that this phase is a β-Ti phase. Figure 2 Analysis of the elemental composition at each point in (c) confirms that phase C is an (Au, Cu, Ni) solid solution phase, the black phase D in the eutectic is a Ni-rich solid solution phase, and the white phase E is an Au-rich solid solution phase. The interface layer F near the K4648 side is confirmed to be a (Ni, Cr) solid solution phase, containing small amounts of Au and Cu. Therefore, the entire joint structure is determined to be TA15 / α-Ti / β-Ti / Nb-Cu / (Au, Cu, Ni) solid solution / (Ni, Cr) solid solution / K4648, with no intermetallic compounds formed within the joint.

[0050] Table 2 Figure 2 Energy spectrum analysis results of each point in the middle (at.%)

[0051]

[0052] Figure 3 The fracture morphology of the joint was obtained for the third experiment. The results showed that the TA15 titanium alloy and the K4648 nickel-based high-temperature alloy were successfully connected by using the Nb / Cu composite metal intermediate layer of the present invention.

Claims

1. A method for brazing titanium alloy and nickel-based high-temperature alloy using a composite intermediate layer, characterized in that The method for brazing titanium alloy and nickel-based high-temperature alloy using a composite intermediate layer is carried out in the following steps:

1. Preparation of Nb / Cu composite intermediate layer: ①. Grind the surfaces of the Nb sheet and Cu sheet with 600#, 1000#, 2000#, 3000#, and 5000# grit sandpaper to remove the surface oxide layer until the surface is bright; ② Immerse the polished Nb and Cu sheets in acetone for ultrasonic cleaning, then rinse with anhydrous ethanol and blow dry. ③. Lay the dried Nb sheet and Cu sheet together and place them in a thermal simulation tester at 600℃~1000℃ and a strain rate of 0.1s. -1 ~10s -1 High temperature compression was performed under the conditions of , with the pressing amount being 60% to 90%, and then air-cooled to room temperature to obtain a Nb / Cu composite intermediate layer; 2. Polish the surfaces to be welded of the parent material titanium alloy and the parent material nickel-based high-temperature alloy with 200#, 400#, 600# and 800# metallographic sandpaper in sequence until the surface is bright; immerse the polished titanium alloy and nickel-based high-temperature alloy in acetone for ultrasonic cleaning, and then rinse with anhydrous ethanol and blow dry; 3. Stack and assemble the two treated base materials, TiZrCuNi powder solder, Au-Ni solder and Nb / Cu composite intermediate layer in the form of titanium alloy-TiZrCuNi-Nb / Cu composite intermediate layer-AuNi-nickel-based high-temperature alloy, with the Nb in the composite intermediate layer located on the side of the TiZrCuNi powder solder; 4. Place the above-mentioned brazing assembly in a vacuum brazing furnace with the titanium alloy at the top, and place a pressing block on the titanium alloy to ensure close contact between the base material and the brazing filler metal during the brazing process. Then evacuate the furnace, heat it to 300°C~310°C and keep it warm for 10min~15min, then heat it to 800°C~810°C, then heat it to the connection temperature of 960°C~980°C and keep it warm for 5min~20min, then cool it to 300°C~310°C, and finally turn off the power and cool it to room temperature with the furnace. The brazing of the titanium alloy and the nickel-based high-temperature alloy is completed.

2. The method for brazing titanium alloy and nickel-based high-temperature alloy using a composite intermediate layer according to claim 1, characterized in that The thickness of the Nb sheet described in step 1 is 0.3 mm, and the thickness of the Cu sheet is 1 mm.

3. The method for brazing titanium alloy and nickel-based high-temperature alloy using a composite intermediate layer according to claim 1, characterized in that In step 1②, the polished Nb sheet and Cu sheet are immersed in acetone and ultrasonically cleaned for 15 minutes.

4. The method for brazing titanium alloy and nickel-based high-temperature alloy using a composite intermediate layer according to claim 1, characterized in that In step 1③, the dried Nb sheet and Cu sheet are bonded together and then placed in a thermal simulation test machine at 800℃ and a strain rate of 5s. -1 The Nb / Cu composite intermediate layer was obtained by high temperature compression under the conditions of 100 ℃ and 200 ℃, with the pressing amount of 70% and then air cooling to room temperature.

5. The method for brazing titanium alloy and nickel-based high-temperature alloy using a composite intermediate layer according to claim 1, characterized in that The base material titanium alloy described in step 2 is TA15.

6. The method for brazing titanium alloy and nickel-based high-temperature alloy using a composite intermediate layer according to claim 1, characterized in that The parent material nickel-based high-temperature alloy described in step 2 is K4648.

7. The method for brazing titanium alloy and nickel-based high-temperature alloy using a composite intermediate layer according to claim 1, characterized in that In step 2, the polished titanium alloy and nickel-based high-temperature alloy are immersed in acetone for ultrasonic cleaning for 15 minutes, and then rinsed with anhydrous ethanol and blown dry.

8. The method for brazing titanium alloy and nickel-based high-temperature alloy using a composite intermediate layer according to claim 1, characterized in that The pressure provided by the pressing block in step 4 is 1×10 3 Pa.

9. The method for brazing titanium alloy and nickel-based high-temperature alloy using a composite intermediate layer according to claim 1, characterized in that In step 4, vacuum is applied to 1.0×10 -3 Pa.

10. The method for brazing titanium alloy and nickel-based high-temperature alloy using a composite intermediate layer according to claim 1, characterized in that In step 4, the temperature is raised to 300°C and kept at this temperature for 10 minutes, then raised to 800°C, and then raised to the connection temperature of 960°C and kept at this temperature for 20 minutes, then cooled to 300°C, and finally the power is turned off and the furnace is cooled to room temperature, thus completing the brazing of the titanium alloy and the nickel-based high-temperature alloy.

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