CN109014549B - Diffusion welding connection method adopting Cu foil and Ti foil as composite intermediate layer - Google Patents

Abstract

The invention discloses a diffusion welding connection method by adopting a Cu foil and a Ti foil as a composite intermediate layer, and relates to connection of a nickel-based superalloy and Ti₂AlNb alloy or Ti₃Al-based alloy. The method comprises the following steps: mixing nickel-base superalloy and Ti₂AlNb alloy or Ti₃Processing the Al-based alloy into a required size, and grinding and polishing; removing oxide films of the copper foil and the Ti foil, and putting the copper foil and the Ti foil together with a welded base material into acetone for ultrasonic cleaning; contacting copper foil with nickel-based superalloy, and contacting titanium foil with Ti₂AlNb alloy or Ti₃Al-based alloy contact to obtain a Ti-based alloy₂AlNb alloy or Ti₃A welded test piece of Al-based alloy/titanium foil/copper foil/nickel-based superalloy is welded by placing the welded workpiece in a vacuum heating furnace, applying pressure, and completing welding after heating, heat preservation and cooling thermal cycle. The invention can reduce welding temperature, control the formation of brittle phase in the joint and improve the performance of the joint. The shear strength of the obtained joint at room temperature reaches 240-310 MPa.

Description

A kind of diffusion welding connection method using Cu foil and Ti foil as composite intermediate layer

technical field

The invention relates to a diffusion welding connection method using Cu foil and Ti foil as a composite intermediate layer, and belongs to the technical field of welding.

Background technique

Titanium-aluminum intermetallic compounds have the advantages of low density, high specific strength, specific stiffness, good oxidation resistance, creep resistance and fatigue resistance, and are one of the most promising aerospace lightweight high-temperature structural materials in the future. one. Among titanium-aluminum intermetallic compounds, the research on Ti ₂ AlNb alloy or Ti ₃ Al-based alloy has been paid much attention, and its working temperature can reach 700℃. Compared with ordinary titanium alloys, Ti ₂ AlNb alloys or Ti ₃ Al-based alloys can be serviced at higher temperatures; compared with nickel-based superalloys, they have a lower density, which is about half that of nickel-based superalloys. In the automotive industry, the characteristics of low density and high strength of Ti ₂ AlNb alloy or Ti ₃ Al-based alloy can be used to realize the lightweight design and manufacture of parts; in the aerospace field, the use of Ti ₂ AlNb alloy or Ti ₃ Al-based alloy part Replacing nickel-based superalloys can reduce the weight of components by about 40%, which is of great significance for improving the thrust-to-weight ratio of aero-engines and the effective range and effective launch load of aerospace vehicles.

In order to realize partial substitution of Ni-based superalloy by Ti ₂ AlNb alloy or Ti ₃ Al-based alloy, and to promote its engineering application in aerospace field, the dissimilarity of Ti ₂ AlNb alloy or Ti ₃ Al-based alloy and Ni-based superalloy must be solved first. connection problem. However, the physical properties and chemical compositions of these two types of materials are quite different, and the difference in the chemical composition of the base metals makes it difficult to find solders that have good compatibility with both base metals, and it is difficult to avoid the formation of brittle compounds in the joints; the two base metals There is a big difference in the thermal expansion coefficient of the joints, and it is easy to generate a certain residual thermal stress in the joint, which will form cracks and lead to the deterioration of joint performance; the element Ti and Ni have a strong affinity, and it is easy to react to form Ti ₂ Ni, TiNi , Ti ₃ Ni and other Ti-Ni intermetallic compounds, these brittle phases will seriously deteriorate the mechanical properties of the joint. It is very difficult to realize the dissimilar connection of Ti ₂ AlNb alloy or Ti ₃ Al-based alloy and nickel-based superalloy, and it is difficult to realize the connection by conventional fusion welding method.

Some researchers used NiCuNbCr alloy, Ti _37~39 -Nb alloy, Ti _{- 7.3~9.3} Nb _-51.5~54.5 Ni(wt.%) alloy as solder to study the argon effect of Ti3Al-based alloy and GH4169 nickel-based superalloy. Arc welding connection, but many Ni-Ti series and Al-(Ni,Cu)-Ti series brittle compounds are formed in the joint, and microcracks are found in the joint, and the tensile strength of the joint at room temperature is only 200MPa (Chen Bingqing, Xiong Huaping , Guo Shaoqing, et al. Microstructure and properties of NiCuNbCr solder Ti ₃ Al/GH4169 alloy argon arc welded joints [J]. Materials Engineering, 2014, 4: 13-18.). Chen Bo et al. brazed Ti ₃ Al-based alloy and GH536 nickel-based superalloy with Ti-13Zr-21Cu-9Ni (wt.%) solder, and more brittle compounds such as Ti-Ni and Ti-Fe were formed in the joint. This leads to the formation of longitudinal cracks in the brazing seam near the base side of GH536, which seriously deteriorates the performance of the joint. The shear strength of the joint is only 86MPa under the specification of 960℃/5min (Chen Bo, Xiong Huaping, Mao Wei, etc. Using Ti-Zr-Cu Microstructure and properties of Ti ₃ Al/Ti ₃ Al and Ti ₃ Al/GH536 joints by Ni vacuum brazing [J]. Journal of Aeronautical Materials, 2010, 30(5): 35-38.).

When Mo foil is used as the intermediate layer to diffusely connect Ti ₂ AlNb alloy and GH4169 superalloy, a complete joint cannot be obtained. When Ta and Nb are used as intermediate layers, a complete joint can be formed, but cracks appear at the interface of GH4169 (Qian Jinwen, Hou Jinbao, Li Jinglong, et al. Preliminary study on vacuum diffusion bonding of Ti ₂ AlNb/GH4169 [J]. Hot Working Technology, 2008, 37(13): 90-92); Ren Haihui et al. used Ni foil and Ti-Ni-Nb alloy Diffusion welding of Ti ₃ Al-based alloy and GH536 nickel-based superalloy was studied for the intermediate layer. The shear strength of the joint obtained at 980℃/20min/20MPa is about 210MPa, and the joint strength needs to be improved (HSRen, X.Wu, B. Chen, et al. Microstructures and mechanical properties of Ti ₃ Al/Ni-based superalloy joints diffusion bonded with Ni and TiNiNb foils, Welding in the World, 2017, 61:375-381). The patent (CN101352772A) invented a method for diffusion connecting TiAl/Nb-based alloy and Ni-based superalloy. In the method described in the patent, the welding temperature reaches 1100°C, the maximum pressure is 30MPa, and the holding time is 60-120min. Since the solution treatment temperature of Ti ₂ AlNb alloy or Ti ₃ Al-based alloy is in the range of about 980℃～1020℃, such high welding temperature and holding time in this patent are likely to damage Ti ₂ AlNb alloy or Ti ₃ The microstructure and properties of the Al-based alloy base metal, and the acquisition of good joint performance cannot be at the expense of the performance of the base metal.

The above is the main research progress on the connection of nickel-based superalloys and Ti ₂ AlNb alloys or Ti ₃ Al-based alloys. At present, the research reports on this field at home and abroad are still relatively limited. As mentioned above, due to the great difference in composition and properties of the two base metals, internal stress is easily induced in the joint and brittle compounds are formed. If the base metal to be welded can be kept at a relatively low temperature for a short time, the formation and growth of intermetallic compounds can be suppressed to a certain extent, thereby reducing the brittleness of the joint. In addition, the lower welding temperature can also reduce the internal stress caused by the difference in the thermal expansion coefficient of the base metal, so as to achieve a good connection of the two materials and obtain a high connection strength. And reduce the influence of welding thermal cycle on the microstructure and properties of base metal, especially Ti ₂ AlNb alloy or Ti ₃ Al based alloy.

SUMMARY OF THE INVENTION

The present invention is designed to address the above-mentioned problems in the prior art and provides a diffusion welding connection method using Cu foil and Ti foil as a composite intermediate layer. Under the condition of 30 minutes, the nickel-based superalloy and Ti ₂ AlNb alloy or Ti ₃ Al-based alloy can be well connected, and the shear strength of the joint exceeds 300MPa, while avoiding the welding thermal cycle to the base metal of Ti ₂ AlNb alloy or Ti ₃ Al-based alloy. adversely affect the organization and performance.

The purpose of this invention is to realize through the following technical solutions:

This kind adopts Cu foil and Ti foil as the diffusion welding connection method of composite intermediate layer, and the steps of this method are as follows:

Step 1. Use wire cutting to process the nickel-based superalloy and Ti ₂ AlNb alloy or Ti ₃ Al-based alloy into the required size, grind the to-be-welded surface of the base metal to be welded with sandpaper, and then perform polishing to obtain the base to be welded. material;

Step 2, performing oxide film removal treatment on copper foil with a thickness of 10-30 μm, and removing oxide film on titanium foil with a thickness of 30-50 μm to obtain an intermediate layer for diffusion welding;

Step 3: Put the treated base metal, copper foil and Ti foil into acetone for ultrasonic cleaning for 3-10 minutes;

Step 4. Coating the copper foil on the to-be-welded surface of the nickel-based superalloy, and affixed the titanium foil on the to-be-welded surface of the Ti ₂ AlNb alloy or Ti ₃ Al-based alloy to obtain a structure of Ti ₂ AlNb alloy or Ti ₃ Welded workpieces of Al-based alloy/titanium foil/copper foil/nickel-based superalloy;

Step 5. Put the workpiece to be welded in the vacuum heating furnace, and apply a pressure of 5 to 15 MPa. When the vacuum degree in the vacuum heating furnace reaches 9×10 ^-2 to 1×10 ^-3 Pa, the electric heating is started, and the heating rate is The temperature is 5～15℃/min. When heated to 850℃～1000℃, the temperature is kept for 10～30min, and then cooled to 400℃～500℃ at the speed of 5～10℃/min, and then the furnace is cooled to room temperature, that is, Complete the dissimilar joining of nickel-based superalloys and Ti ₂ AlNb alloys or Ti ₃ Al-based alloys.

Further, the copper foil is treated with HNO ₃ and H ₂ O solution with a volume ratio of 1:9 to remove the oxide film, and the etching time is 30-60 s.

Further, the titanium foil is treated with HF, HNO ₃ , and H ₂ O in a volume ratio of 1:3:21 to remove the oxide film, and the etching time is 30-60s.

Further, the thickness of the copper foil used in the second step is 20 μm and the thickness of the titanium foil is 30 μm.

Further, in step five, a pressure of 10 MPa is applied.

Further, in the fifth step, when the degree of vacuum in the vacuum heating furnace reaches 1×10 ^-3 Pa, the heating by electricity is started.

Further, the heating rate in step 5 is 10°C/min.

Further, in step 5, the heat preservation is started when heated to 900° C., and the heat preservation time is 20 minutes.

Further, in step 5, it is cooled at a speed of 6°C/min, cooled to 400°C, and then cooled to room temperature with the furnace.

The technical scheme of the present invention has the following advantages:

(1) The previous test results show that the element Ti easily reacts with the nickel-based superalloy to form a complex multi-component phase, which has an adverse effect on the joint performance. The technical scheme of the present invention is that the titanium foil is placed on the side of the Ti ₂ AlNb alloy or Ti ₃ Al-based alloy, the titanium foil is separated from the nickel-based superalloy by copper foil, and "Ti ₂ AlNb alloy or Ti ₃ Al-based alloy is used. /titanium foil/copper foil/nickel-based superalloy" joint structure, which can avoid the formation of complex multi-component phases. In addition, the main element in Ti ₂ AlNb alloy or Ti ₃ Al-based alloy is Ti, which is fully miscible with titanium foil; the element Cu and Ni are fully miscible, so copper foil can form a good connection with nickel-based superalloy. The selection of the Cu/Ti composite intermediate layer in the present invention fully considers the characteristics of the two base metals and the compatibility between the elements.

(2) As described above, when connecting a nickel-based superalloy with a Ti ₂ AlNb alloy or a Ti ₃ Al-based alloy, residual thermal stress and brittle compounds are likely to be formed in the joint. The invention proposes to use the Cu/Ti composite intermediate layer to carry out the diffusion connection of the two materials, and compatibility occurs between the copper foil and the nickel-based superalloy, and between the titanium foil and the Ti ₂ AlNb alloy or the Ti ₃ Al-based alloy. The reaction can significantly reduce the formation tendency of the compound, which is beneficial to obtain a good connection; at the same time, the reaction between the copper foil and the titanium foil is also easy to occur. Therefore, the requirements for welding specifications are reduced, and the two base metals can be held at a relatively low temperature (not more than 1000°C) for a short time (not more than 30min) to achieve a good connection. In addition, the solution treatment temperature of Ti ₂ AlNb alloy or Ti ₃ Al-based alloy is about 980℃～1020℃. Relatively low welding temperature can avoid or reduce the adverse effects of welding thermal cycle on the structure and properties of the base metal.

(3) Both copper foil and titanium foil used in the present invention are relatively thin (10-50 μm), which can ensure that they can fully participate in the reaction during the connection process, and there is no residual copper foil or titanium foil after welding, which can prevent the pure metal layer from damaging the joint performance;

(4) In the technical scheme of the present invention, by further adjusting and controlling the degree of reaction between copper foil and titanium foil, copper foil and nickel-based superalloy, the two metal foils can fully participate in the reaction, while suppressing or avoiding titanium foil, Ti ₂ The direct reaction of AlNb alloy or Ti ₃ Al-based alloy and nickel-based superalloy controls the existence of hard and brittle phases in the joint to obtain better joint structure. The present invention obtains nickel-based superalloy and Ti ₂ AlNb alloy or Ti ₃ The room temperature tensile strength of dissimilar joints of Al-based alloys reaches 240-310MPa.

(5) Since the oxide film on the surface of the copper foil and the titanium foil will adversely affect the welding interface, in the technical solution of the present invention, the volume ratio of HNO ₃ and H ₂ O solution is 1:9 and the volume ratio is 1:3. : 21 HF, HNO ₃ , H ₂ O solutions can effectively remove the oxide film on the surface of copper foil and titanium foil respectively, while avoiding damage to very thin copper foil and titanium foil;

When the vacuum degree in the vacuum heating furnace reaches 1×10 ^-3 Pa, electric heating is started, which can effectively avoid the re-oxidation of copper foil and titanium foil during the heating process;

Due to the large difference in the thermal expansion coefficients of the two base metals to be welded, the faster cooling rate after welding will generate a large internal stress in the joint, which will lead to the initiation of micro-cracks. In the technical method of the present invention, after the heat preservation is completed, Controlling the cooling rate, when the joint is cooled at a cooling rate of 6°C/min, it can effectively reduce the internal stress in the joint, which is beneficial to ensure the performance of the joint.

Detailed ways

Embodiment 1, using copper foil and titanium foil as the composite intermediate layer to carry out diffusion welding of nickel-based superalloy and Ti ₃ Al-based alloy, the welding process is as follows:

Step 1, using wire cutting to process the nickel-based superalloy and the Ti ₃ Al-based alloy into the required size, grinding the to-be-welded surface of the base metal to be welded with sandpaper, and then polishing to obtain the base metal to be welded;

Step 2: Use HNO ₃ , H ₂ O solution with a volume ratio of 1: 9 to remove the oxide film on the copper foil with a thickness of 30 μm, the etching time is 30 s, and use HF, HNO 3 , HNO ₃ , The titanium foil with a thickness of 40 μm was treated with H ₂ O solution to remove the oxide film, and the etching time was 50 s to obtain the intermediate layer for diffusion welding;

Step 3. Put the treated base metal, copper foil and Ti foil into acetone for ultrasonic cleaning for 10min;

Step 4. Coating the copper foil on the to-be-welded surface of the nickel-based superalloy, and affixed the titanium foil on the to _- be-welded surface of the Ti3Al-based alloy to obtain a structure _of Ti3Al-based alloy/titanium foil/copper foil / Welded workpieces of nickel-based superalloys;

Step 5. Put the workpiece to be welded in the vacuum heating furnace, and apply a pressure of 10 MPa. When the vacuum degree in the vacuum heating furnace reaches 1 × 10 ^-3 Pa, start heating with electricity, and the heating rate is 10 °C/min. At 900°C, the temperature is kept for 20min, then cooled to 500°C at a rate of 5°C/min, and then furnace cooled to room temperature to complete the dissimilar connection between the nickel-based superalloy and the Ti ₃ Al-based alloy.

The obtained microstructure photos of Ti ₃ Al/GH536 nickel-based superalloy diffusion welded joints show that the connection interface forms a good metallurgical bond without any defects, and the microstructure of the Ti ₃ Al-based alloy base metal is not affected by welding thermal cycles.

In the second embodiment, the nickel-based superalloy and the Ti ₃ Al-based alloy were diffusion welded with copper foil and titanium foil as the composite intermediate layer, and the welding process was as follows:

Step 1, using wire cutting to process the nickel-based superalloy and the Ti ₃ Al-based alloy into the required size, grinding the to-be-welded surface of the base metal to be welded with sandpaper, and then polishing to obtain the base metal to be welded;

Step 2: Use HNO ₃ and H ₂ O solutions with a volume ratio of 1:9 to remove the oxide film on the copper foil with a thickness of 20 μm. The etching time is 20s, and the volume ratio is 1:3: ₂₁ . The titanium foil with a thickness of 30 μm was treated with H ₂ O solution to remove the oxide film, and the etching time was 30 s to obtain the intermediate layer for diffusion welding;

Step 3. Put the treated base metal, copper foil and Ti foil into acetone for ultrasonic cleaning for 10min;

Step 4. Coating the copper foil on the to-be-welded surface of the nickel-based superalloy, and affixed the titanium foil on the to _- be-welded surface of the Ti3Al-based alloy to obtain a structure _of Ti3Al-based alloy/titanium foil/copper foil / Welded workpieces of nickel-based superalloys;

Step 5. Put the workpiece to be welded in the vacuum heating furnace, and apply a pressure of 8 MPa. When the vacuum degree in the vacuum heating furnace reaches 1 × 10 ^-3 Pa, start heating with electricity, and the heating rate is 10 °C/min. At 900°C, the temperature was kept for 10min, then cooled to 400°C at a rate of 5°C/min, and then cooled to room temperature in the furnace to complete the dissimilar connection of the nickel-based superalloy and the Ti ₃ Al-based alloy.

Embodiment 3, using copper foil and titanium foil as composite intermediate layer to carry out diffusion welding of nickel-based superalloy and Ti ₂ AlNb alloy, the welding process is as follows:

Step 1, using wire cutting to process the nickel-based superalloy and the Ti ₂ AlNb alloy into the required size, grinding the to-be-welded surface of the base metal to be welded with sandpaper, and then polishing to obtain the base metal to be welded;

Step 2: Use HNO ₃ and H ₂ O solutions with a volume ratio of 1:9 to remove the oxide film on the copper foil with a thickness of 20 μm. The etching time is 20s, and the volume ratio is 1:3: ₂₁ . The titanium foil with a thickness of 30 μm was treated with H ₂ O solution to remove the oxide film, and the etching time was 30 s to obtain the intermediate layer for diffusion welding;

Step 3. Put the treated base metal, copper foil and Ti foil into acetone for ultrasonic cleaning for 10min;

Step 4. Coating the copper foil on the to-be-welded surface of the nickel-based superalloy, and affixed the titanium foil on the to-be-welded surface of the Ti ₂ AlNb alloy to obtain a structure of Ti ₂ AlNb alloy/titanium foil/copper foil/nickel Welded workpieces based on superalloys;

Step 5. Put the workpiece to be welded in the vacuum heating furnace, and apply a pressure of 8 MPa. When the vacuum degree in the vacuum heating furnace reaches 1 × 10 ^-3 Pa, start heating with electricity, and the heating rate is 10 °C/min. At 900°C, the temperature was kept for 10min, then cooled to 400°C at a rate of 5°C/min, and then cooled to room temperature in the furnace to complete the dissimilar connection between the nickel-based superalloy and the Ti ₂ AlNb alloy.

In the fourth embodiment, the nickel-based superalloy and the Ti ₂ AlNb alloy were diffusion welded with copper foil and titanium foil as the composite intermediate layer, and the welding process was as follows:

Step 1, using wire cutting to process the nickel-based superalloy and the Ti ₂ AlNb alloy into the required size, grinding the to-be-welded surface of the base metal to be welded with sandpaper, and then polishing to obtain the base metal to be welded;

Step 2: Use HNO ₃ , H ₂ O solution with a volume ratio of 1: 9 to remove the oxide film on the copper foil with a thickness of 30 μm, the etching time is 30 s, and use HF, HNO 3 , HNO ₃ , The titanium foil with a thickness of 40 μm was treated with H ₂ O solution to remove the oxide film, and the etching time was 40 s to obtain the intermediate layer for diffusion welding;

Step 3. Put the treated base metal, copper foil and Ti foil into acetone for ultrasonic cleaning for 10min;

Step 4. Coating the copper foil on the to-be-welded surface of the nickel-based superalloy, and affixed the titanium foil on the to-be-welded surface of the Ti ₂ AlNb alloy to obtain a structure of Ti ₂ AlNb alloy/titanium foil/copper foil/nickel Welded workpieces based on superalloys;

Step 5. Put the workpiece to be welded in the vacuum heating furnace, and apply a pressure of 15MPa. When the vacuum degree in the vacuum heating furnace reaches 1×10 ^-3 Pa, start heating with electricity, and the heating rate is 10℃/min. At 980°C, the temperature is kept for 10min, then cooled to 500°C at a rate of 8°C/min, and then cooled to room temperature in the furnace to complete the dissimilar connection between the nickel-based superalloy and the Ti ₂ AlNb alloy.

Claims (6)

1. a diffusion welding connection method that adopts Cu foil and Ti foil to make a composite intermediate layer, the steps of the method are as follows: Step 1. Use wire cutting to process the nickel-based superalloy and Ti ₂ AlNb alloy or Ti ₃ Al-based alloy into the required size, grind the to-be-welded surface of the base metal to be welded with sandpaper, and then perform polishing to obtain the base to be welded. material; Step 2, performing oxide film removal treatment on copper foil with a thickness of 10-30 μm, and removing oxide film on titanium foil with a thickness of 30-50 μm to obtain an intermediate layer for diffusion welding; Use HNO ₃ and H ₂ O solution with a volume ratio of 1:9 to remove the oxide film on the copper foil, and the etching time is 30-60s; The titanium foil is treated with HF, HNO ₃ , H ₂ O solution with a volume ratio of 1:3:21 to remove the oxide film, and the etching time is 30-60s; Step 3: Put the treated base metal, copper foil and Ti foil into acetone for ultrasonic cleaning for 3-10 minutes; Step 4. Coating the copper foil on the to-be-welded surface of the nickel-based superalloy, and affixed the titanium foil on the to-be-welded surface of the Ti ₂ AlNb alloy or Ti ₃ Al-based alloy to obtain a structure of Ti ₂ AlNb alloy or Ti ₃ Welded workpieces of Al-based alloy/titanium foil/copper foil/nickel-based superalloy; Step 5. Put the workpiece to be welded in the vacuum heating furnace, and apply a pressure of 5 to 15 MPa. When the vacuum degree in the vacuum heating furnace reaches 9×10 ^-2 to 1×10 ^-3 Pa, the electric heating is started, and the heating rate is The temperature is 5～15℃/min, when heated to 850℃～1000℃, keep at this temperature for 10～30min, then cool to 400℃ at a speed of 6℃/min, and then furnace cool to room temperature, that is, the nickel-based superalloy is completed. Dissimilar bonding with Ti ₂ AlNb alloys or Ti ₃ Al based alloys. 2 . The diffusion welding method using Cu foil and Ti foil as composite intermediate layer according to claim 1 , wherein the thickness of the copper foil used in the second step is 20 μm and the thickness of the Ti foil is 30 μm. 3 . 3 . The diffusion welding method for using Cu foil and Ti foil as composite intermediate layer according to claim 1 , wherein a pressure of 10 MPa is applied in step 5. 4 . 4. the diffusion welding connection method that adopts Cu foil and Ti foil as composite intermediate layer according to claim 1, it is characterized in that: in step 5, when the vacuum degree in the vacuum heating furnace reaches 1 × 10 ^-3 Pa, start Electric heating. 5 . The diffusion welding method for using Cu foil and Ti foil as composite intermediate layer according to claim 1 , wherein the heating rate in step 5 is 10° C./min. 6 . 6. The diffusion welding connection method of adopting Cu foil and Ti foil as composite intermediate layer according to claim 1, characterized in that: in step 5, heat preservation is started when heated to 900 DEG C, and the heat preservation time is 20min.