Method for improving vacuum electron beam welded joint of tantalum-nickel dissimilar alloy by adding Cu interlayer

Abstract

The present application belongs to the field of aero-engine fuel chamber, and aims to solve the problem of the existence of a thick reaction layer containing brittle compounds on the Ta side of the tantalum-nickel dissimilar alloy vacuum electron beam welded joint. The electron beam welding is carried out by adding a Cu intermediate layer to reduce the thickness of the reaction layer containing brittle compounds. The vacuum electron beam welding is carried out by using Ta plate, GH4169 plate and Cu foil. The main steps are as follows: 1. pretreating the plate 2. fixing the plate and copper foil on the electron beam welding special fixture 3. determining the process parameters and then carrying out vacuum electron beam welding.

Description

Technical Field

[0001] This application belongs to the field of aero-engines, and in particular relates to a method for improving electron beam welding joints of tantalum-nickel dissimilar alloys by adding a Cu interlayer. Background Technology

[0002] Tantalum is a refractory metal with a melting point as high as 2996°C. Due to its excellent wear resistance, corrosion resistance, weldability, and high-temperature performance, it is widely used in various fields, including aerospace, electronics, and chemical processing, for aircraft engines, capacitors, and corrosion-resistant components. GH4169 wrought superalloy is a typical Fe-Ni-Cr type superalloy. With its excellent high-temperature strength and strong resistance to strain-aging cracking, it is already one of the most widely used high-temperature alloy materials in the aerospace and nuclear energy fields. The high-temperature alloys used in aircraft engine combustors are mainly wrought superalloys, with GH4169 and GH141 being the main domestic materials. Components such as aircraft engine combustor bushings are subjected to long-term high-temperature and alternating load environments of 600-1200°C. Traditional nickel-based alloys lack sufficient corrosion resistance, and pure tantalum is difficult and costly to process. Using Ta2.5W and GH4169 nickel-based alloys for engine combustor bushings can reduce costs and weight, while possessing the corrosion resistance of tantalum and the structural strength of nickel-based alloys.

[0003] Tantalum alloys are highly sensitive to nitrogen, hydrogen, and oxygen at high temperatures. Even small amounts of these elements can significantly reduce the overall properties of tantalum. Therefore, commonly used welding methods, including MAG welding, TIG welding, brazing, and diffusion welding, are difficult to achieve effective welding. Vacuum electron beam welding, on the other hand, offers advantages such as concentrated energy, controllable heat input, virtually no pollution, and a small heat-affected zone. Therefore, electron beam welding was chosen for welding Ta2.5W and GH4169.

[0004] Currently, there is limited research on electron beam welding joints between tantalum-tungsten alloys and GH4169. Notably, most studies indicate the formation of a hard and brittle reaction layer on the tantalum side during electron beam welding. Tensile fracture occurs within this reaction layer during mechanical property testing, and the layer exhibits high hardness. Brittle Ni-Ta intermetallic compounds are also observed near the reaction layer. In dissimilar metal welding, due to significant differences in the physical and chemical properties of the two materials, adding an intermediate layer is typically employed to improve the weld joint's performance. Therefore, using an intermediate layer in tantalum-nickel electron beam welding is highly recommended.

[0005] Therefore, a new intermediate layer needs to be developed to improve electron beam welding joints of tantalum-nickel dissimilar alloys. Summary of the Invention

[0006] The purpose of this application is to provide a method for improving electron beam welding joints of tantalum-nickel dissimilar alloys by adding a Cu interlayer, thereby reducing the thickness of brittle intermetallic compounds in the tantalum-nickel dissimilar alloy welding joint.

[0007] To meet the above requirements, this application provides the following technical solution, with the following steps:

[0008] Step 1: Cut the required tantalum-nickel plates to the required size using a wire cutting machine, and cut the copper foil to the required size. After ultrasonic cleaning for 5 minutes, blow dry the copper foil and then place it in a vacuum drying oven to wait for welding.

[0009] Step 2: After fixing the tantalum-nickel plate and copper foil in the electron beam welding fixture, place them into the electron beam welding chamber;

[0010] Step 3: Put the electron beam welding machine into vacuum mode. After the vacuum mode is completed, apply high pressure. Adjust the required electron beam welding process parameters, and then perform electron beam welding.

[0011] Step 4: After electron beam welding is completed, remove the sample after it has cooled down.

[0012] Furthermore, the tantalum plate uses Ta2.5W, the nickel plate uses GH4169, and the copper foil uses pure copper.

[0013] Furthermore, in step 1, the ultrasonic cleaning solution is anhydrous ethanol solution, and the ultrasonic time is 10 minutes.

[0014] Furthermore, in step 2, a specific electron beam welding fixture is used, as shown in the figure.

[0015] Furthermore, in step 3, the welding method used is to offset the electron beam 0.2 mm toward the tantalum side.

[0016] Furthermore, in step 3, the vacuum level needs to reach 1.0 × 10⁻⁶. -3

[0017] Furthermore, in step 3, the welding process parameters are: accelerating voltage of 150KV, current of 0.3mA, welding speed of 500mm / min, and SW value is the value measured each time.

[0018] Furthermore, in step 4, the cooling time after welding is generally 5 minutes, and the cooling temperature is room temperature.

[0019] The beneficial effects of this invention are:

[0020] A method for improving electron beam welded joints of tantalum-nickel dissimilar alloys by adding a Cu interlayer is provided. This method aims to address the problem of a thick reaction layer containing brittle compounds on the Ta-side of the vacuum electron beam welded joint of tantalum-nickel dissimilar alloys. By adding a Cu interlayer during electron beam welding, the thickness of the reaction layer containing brittle compounds is reduced, thereby significantly improving the quality of the welded joint. The following points should be noted regarding the above steps:

[0021] 1) Firstly, in this invention, the purpose of adding Cu is to prevent the thermal expansion coefficients between Ta and GH4169 from differing too much, which would lead to compositional supercooling and the formation of a continuous network dendritic structure. The addition of Cu is because the linear expansion coefficients between Cu and GH4169 are not significantly different, thus significantly increasing the G / R ratio and promoting the transformation of the continuous network dendritic structure into a cellular dendritic structure.

[0022] 2) Adding a Cu interlayer significantly alters the weld volume, resulting in a noticeably smaller weld zone in electron beam welded joints. In welded joints without a Cu interlayer, the poor thermal conductivity of Ni causes heat to concentrate in the weld zone, leading to a wider molten pool on the Ni-based side. The Cu interlayer, with its superior thermal conductivity, reduces heat concentration in the weld zone, resulting in a narrower molten pool in the Ni-based alloy.

[0023] 3) Mechanical property tests on the electron beam welded joint after adding a Cu interlayer revealed a significant improvement in mechanical properties. This demonstrates that adding a Cu interlayer effectively improves the performance of the Ta / GH4169 alloy electron beam welded joint. Attached Figure Description

[0024] Figure 1 This indicates the position of the three metal plates before welding.

[0025] Figure 2 Macroscopic morphology diagram after electron beam welding

[0026] Figure 3 A dimensional drawing showing the dimensions of a stretched sample.

[0027] Figure 4 This refers to the microstructure near the reaction layer of weld joints with and without an intermediate layer.

[0028] Figure 5 This refers to images showing the fracture location of a sample after mechanical property testing.

[0029] Figure 6 This refers to the stress-strain curve diagram from a tensile test. Detailed Implementation

[0030] The present invention will be further described below with reference to specific embodiments.

[0031] Step 1: Cut the required tantalum and nickel plates to the required size using a wire cutting machine, and cut the copper foil to the required size. Then, polish the plates with sandpaper, perform ultrasonic cleaning for 5 minutes, blow dry, and then put them into a vacuum drying oven to wait for welding.

[0032] The purpose of grinding and polishing the sample is to remove oil and impurities from the surface of the material, and to make the sample smoother, thus allowing for better alignment during welding. Ultrasonic cleaning removes any remaining impurities after grinding and polishing. Vacuum drying is necessary because the sample is prone to oxidation; therefore, after pre-treatment, it should be stored in a vacuum drying oven.

[0033] Step 2: After fixing the tantalum-nickel plate and copper foil in the electron beam welding fixture, place them into the electron beam welding chamber;

[0034] The three metals are placed into the fixture in sequence, as shown in the diagram. Figure 1 As shown.

[0035] Step 3: Put the electron beam welding machine into vacuum mode. After the vacuum mode is completed, apply high pressure. Adjust the required electron beam welding process parameters, and then perform electron beam welding.

[0036] Because the melting points of Ta and GH4169 differ significantly, we considered offset electron beam welding with an offset of 0.2 mm towards the Ta side. The welding process parameters were: accelerating voltage of 150 kV, current of 0.3 mA, welding speed of 500 mm / min, and SW value as measured in each test.

[0037] Step 4: After electron beam welding is completed, remove the sample after it has cooled down.

[0038] After cooling for 5 minutes, remove the sample from the fixture and observe its main macroscopic morphology to check for any adverse results such as cracks. The macroscopic morphology of the weld is shown in the image below. Figure 2 As shown.

[0039] The welded samples undergo post-weld processing. The welded plates are cut into the required sample sizes, and tensile specimens are prepared. The specific dimensions are as follows: Figure 3 As shown.

[0040] After grinding and polishing the welded sample, microstructure testing was performed. It was observed that the microstructure of the weld joint with the Cu interlayer was mainly composed of cellular dendrites, specifically as follows: Figure 4 As shown.

[0041] By conducting a tensile test on the tensile specimen, the location of the tensile fracture can be determined, such as... Figure 5 As shown. And the stretching curve can be obtained simultaneously.

Claims

1. A method for improving vacuum electron beam welding joints of tantalum-nickel dissimilar alloys by adding a Cu interlayer, characterized in that, The main steps are as follows: Step 1: Cut the required tantalum-nickel plates to the required size using a wire cutting machine, and cut the copper foil to the required size. After ultrasonic cleaning for 5 minutes, blow dry the copper foil and then place it in a vacuum drying oven to wait for welding. Step 2: After fixing the tantalum-nickel plate and copper foil in the electron beam welding fixture, place them into the electron beam welding chamber; Step 3: Put the electron beam welding machine into vacuum mode. After the vacuum mode is completed, apply high pressure, adjust the required electron beam welding process parameters, and then perform electron beam welding. Step 4: After electron beam welding is completed, remove the sample after it has cooled down.

2. The method for improving the vacuum electron beam welding joint of tantalum-nickel dissimilar alloys by adding a Cu interlayer according to claim 1, characterized in that, In step 1, the tantalum plate used is Ta2.5W, the nickel plate is GH4169, and the copper foil is pure copper.

3. The method for improving the vacuum electron beam welding joint of tantalum-nickel dissimilar alloys by adding a Cu interlayer according to claim 1, characterized in that, In step 1, the tantalum-nickel plate used for welding is 70mm long, 50mm wide, and 1mm thick, and the copper foil is 70mm long, 0.05mm wide, and 1mm thick.

4. The method for improving the vacuum electron beam welding joint of tantalum-nickel dissimilar alloys by adding a Cu interlayer according to claim 1, characterized in that, In step 1, the ultrasonic cleaning solution is anhydrous ethanol solution, and the ultrasonic time is 10 minutes.

5. The method for improving the vacuum electron beam welding joint of tantalum-nickel dissimilar alloys by adding a Cu interlayer according to claim 1, characterized in that, In step 2, a specific electron beam welding fixture is used, as shown in the figure.

6. The method for improving the vacuum electron beam welding joint of tantalum-nickel dissimilar alloys by adding a Cu interlayer according to claim 1, characterized in that, In step 3, the welding method used is to offset the electron beam 0.2 mm toward the tantalum side.

7. The method for improving the vacuum electron beam welding joint of tantalum-nickel dissimilar alloys by adding a Cu interlayer according to claim 1, characterized in that, In step 3, the vacuum level needs to reach 1.0 × 10⁻⁶. -3 .

8. The method for improving the vacuum electron beam welding joint of tantalum-nickel dissimilar alloys by adding a Cu interlayer according to claim 1, characterized in that, In step 3, the welding process parameters are: accelerating voltage of 150KV, current of 0.3mA, welding speed of 500mm / min, and SW value is the value measured each time.

9. The method for improving the vacuum electron beam welding joint of tantalum-nickel dissimilar alloys by adding a Cu interlayer according to claim 1, characterized in that, In step 4, the cooling time after welding is generally 5 minutes, and the cooling temperature is room temperature.

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