Method for rapid diffusion bonding of discharge plasma after ultrasonic impact surface treatment

Abstract

The invention discloses a method for improving the metal diffusion bonding speed and quality through ultrasonic impact surface treatment, and belongs to the technical field of solid welding. The method comprises the steps that firstly, a blank piece is prepared through cutting, and surface grinding and ultrasonic impact grain refining treatment are conducted on the blank piece; secondly, the surface of the blank is subjected to accurate grinding and polishing treatment; thirdly, local machining is conducted on the blank; and fourthly, the blanks are combined and assembled, and rapid diffusion bonding preparation of the parts is conducted according to optimized technological parameters. Ultrasonic impact can refine surface grains, form a nano-grain layer and activate the atomic activity of the diffusion bonding surface, and by means of the characteristics of rapid heating and cooling of the discharge plasma diffusion furnace, atomic diffusion promotion and the like, the diffusion bonding temperature is reduced, the diffusion bonding time is shortened, the grain growth degree is controlled, and a high-quality diffusion bonding joint is obtained. The method is especially suitable for batch manufacturing of parts such as micro-channel radiators, waveguide structures and hollow multilayer structures.

Description

Technical Field

[0001] This invention relates to a method for improving the speed and quality of metal diffusion bonding by using ultrasonic impact surface treatment, belonging to the field of solid-state welding technology. Background Art

[0002] For a long time, diffusion bonding technology has been successfully applied in the manufacturing of complex parts. The principle of diffusion bonding is that the surfaces of materials in contact approach each other under the influence of temperature and pressure, and the atoms at the welding interface diffuse into each other to achieve a reliable connection. It is an effective method for complex structural components such as microchannel heat sinks, waveguide structures, multilayer hollow structures, and dissimilar materials, offering advantages such as high product precision and stable product quality. However, during the heating process in a vacuum diffusion bonding furnace, prolonged heating reduces production efficiency, and the prolonged high-temperature environment causes significant grain growth in the workpiece, reducing the overall performance of the diffusion-bonded joint and the workpiece. Therefore, improving the heating and holding time and reducing the diffusion bonding temperature are of great significance for improving the production efficiency of complex parts, enhancing the overall performance and service life of the workpiece.

[0003] Existing technologies propose a technique for preparing a nanolayer between titanium alloys and titanium-aluminum alloys to accelerate and promote the diffusion bonding process. Regarding workpiece diffusion surface treatment, existing technologies propose a method for obtaining high-performance alloy diffusion bonding joints by shot peening nano-activation of TC17 and TC4 titanium alloy surfaces; and also propose a method for low-temperature diffusion bonding of tungsten alloy and stainless steel surfaces through ultrasonic shot peening nano-activation treatment and the addition of a third material interlayer.

[0004] In the aforementioned diffusion bonding method, ultrasonic shot peening is used before diffusion to refine the surface grains, thereby increasing the diffusion activation energy and alloying process on the metal surface and improving the strength of the diffusion-bonded joint. This highlights the realization and principle verification of the diffusion bonding process for metal sample-level joints. However, during the slow heating process of the diffusion bonding equipment, the fine surface grains after ultrasonic shot peening rapidly deteriorate under thermal effects, resulting in abnormal grain growth. This significantly reduces the beneficial effect of surface fine grains on promoting diffusion bonding. In particular, for hollow and complex structural parts such as microchannel heat sinks, waveguide structures, and multilayer hollow structures, there is still no effective, efficient, high-quality, and high-performance preparation method for low-temperature diffusion bonding. Summary of the Invention

[0005] This invention addresses the above-mentioned problems by proposing a rapid diffusion bonding method combining ultrasonic impact pretreatment and spark plasma diffusion. This method is applicable to the mass production of complex parts such as microchannel heat sinks, waveguide structures, and multi-layer hollow structures made of materials like titanium alloys, stainless steel, aluminum alloys, and high-temperature alloys. Ultrasonic impact increases the effective contact area of ​​the workpiece surface and refines the surface grains. The rapid heating and cooling characteristics of the spark plasma diffusion furnace suppress grain growth defects caused by prolonged heating during the diffusion bonding process. Since the diffusion activation energy is reduced after grain refinement following ultrasonic impact, high-quality diffusion-bonded joints can be obtained through diffusion bonding.

[0006] The technical solution of this invention is as follows:

[0007] 1. Cut and prepare blanks, and perform surface grinding and ultrasonic impact fine graining treatment on the blanks; 2. Perform fine grinding and polishing treatment on the surface of the blanks; 3. Perform local machining on the blanks; 4. Assemble the blanks and prepare the parts by rapid diffusion connection according to the selected process parameters.

[0008] The specific steps of the combined fast and high-quality diffusion connection method are as follows:

[0009] Step 1: Cut and prepare the blank, and perform surface grinding and ultrasonic impact fine grain treatment on the blank;

[0010] 1.1 Cut the blank according to the design drawings of the parts and components, remove burrs, and grind to remove the oxide film on the surface to be diffused and connected;

[0011] 1.2 Use sandpaper, a grinder, or similar tools to polish the surface of the workpiece to be subjected to ultrasonic impact treatment, and then clean it;

[0012] 1.3 Following the designed impact movement path, ultrasonic impact is applied to the area on the surface of the part that requires diffusion connection, thereby preparing a nanocrystalline layer of a preset thickness on the surface of the blank.

[0013] Step 2: Polish the uneven surface after impact to remove the thin layer of the surface nano-layer to achieve a mirror effect, ensuring a smooth surface while retaining most of the nano-layer.

[0014] Step 3: Perform localized machining on the ultrasonically impacted and polished blank according to the part structure, and prepare it for diffusion connection.

[0015] Step 4: Assemble the blanks and prepare the parts through rapid diffusion bonding according to the optimized process parameters, specifically including:

[0016] 4.1 Assemble the ultrasonically impacted parts and components, place them in the tooling according to the set process, and put the parts and tooling together into the discharge plasma diffusion furnace. After vacuuming, start heating after reaching the set value, and perform high-temperature diffusion bonding according to the predetermined rapid diffusion bonding process parameters. After the diffusion bonding is completed, unload the pressure.

[0017] 4.2 Cool to room temperature, remove the diffusion connection parts and tooling, and obtain qualified products.

[0018] The beneficial effects of the present invention are:

[0019] This invention employs an ultrasonic impact surface treatment process, which can obtain a nanocrystalline layer of 10-100 μm on the diffusion bonding surface, refine the grain size, increase the atomic diffusion channels on the material surface, and reduce the diffusion activation energy. This can reduce the diffusion temperature, reduce the degree of grain growth caused by high-temperature heating during diffusion bonding, and optimize the performance of the diffusion bonding joint.

[0020] This invention uses a discharge plasma diffusion furnace to generate discharge plasma. Under the action of pulsed current, the discharge plasma heats the diffusion parts, and the assembly can be heated quickly. Discharge plasma heating can shorten the heating history and avoid excessive grain growth. The pulsed current promotes atomic diffusion at the diffusion interface and affects the performance of the diffusion connection joint. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the process of a rapid diffusion bonding method for discharge plasma after ultrasonic impact surface treatment according to the present invention.

[0022] Figure 2 This is a schematic diagram of the ultrasonic impact surface treatment device of the present invention.

[0023] Figure 3 This is a schematic diagram of the ultrasonic impact path and region of the present invention.

[0024] Figure 4 This is a schematic diagram illustrating the microstructural changes of discharge plasma diffusion connections refined by ultrasonic impact.

[0025] Figure 5 A hollow microchannel heat sink fabricated using a discharge plasma diffusion bonding process refined by ultrasonic shock.

[0026] Figure 6 Hollow-structure aircraft skin components prepared using a discharge plasma diffusion bonding process refined by ultrasonic shock. DETAILED DESCRIPTION

[0027] To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the following examples provide a more detailed description of the invention. It should be noted that the specific embodiments described herein are merely illustrative and not intended to limit the scope of the invention.

[0028] like Figure 1 The diagram shows a flow chart of a method for improving the speed and quality of metal diffusion bonding through ultrasonic impact surface treatment according to the present invention. The method of the present invention is as follows: Step 1: Cutting and preparing a blank, and performing surface grinding and ultrasonic impact fine grain treatment on the blank; Step 2: Fine grinding and polishing treatment on the surface of the blank; Step 3: Performing local machining on the blank; Step 4: Assembling the blank and preparing the parts for rapid diffusion bonding according to the preferred process parameters.

[0029] like Figure 2 As shown, the ultrasonic impact surface treatment device of the present invention is the equipment used in the ultrasonic impact surface treatment process of the present invention. Figure 3 This is a schematic diagram of the ultrasonic impact path and region of the present invention. Figure 4 This is a schematic diagram illustrating the changes in the microstructure of the material during the ultrasonic impact refinement and discharge plasma diffusion bonding processes of the present invention.

[0030] The following specific data examples illustrate the present invention.

[0031] Example 1

[0032] The metal material is 316L stainless steel, and the manufactured part is a microchannel heat sink for petrochemical applications prepared by diffusion bonding method, as shown in the schematic diagram. Figure 5 In this embodiment, a high-quality diffusion connection method for a 316L stainless steel microchannel heat sink is as follows:

[0033] (1) Cut the microchannel heat sink diffusion connection blank according to the design drawings of the part. Use 400#, 800#, 1500# and 2000# silicon carbide sandpaper to polish the surface burrs and oxide film on the surface to be diffused and connected in sequence. Clean with alcohol for 25 minutes to remove surface oil and powder dust. After cleaning, blow dry with cold air.

[0034] (2) According to the designed impact movement path, ultrasonic impact is performed on the area of ​​the part surface that needs to be diffused and connected to prepare a 60 μm thick nanocrystalline layer on the surface of the blank. The impact treatment process parameters are as follows: ultrasonic amplitude is 30-50 μm, impact needle diameter is 3-4 mm, angle between impact needle and blank is 40-45°, impact speed is 100-120 mm / min, impact needle length is 15-20 mm, and the impact needle arrangement is a single needle;

[0035] (3) Use 5000# sandpaper to sand the surface of the blank after ultrasonic impact, and then mechanically polish it to a mirror finish;

[0036] (4) The blank after ultrasonic impact is machined into a diffusion connection part with a microchannel heat sink structure for later use.

[0037] (5) Assemble the machined parts with the mold, and place the whole assembly into a discharge plasma diffusion furnace with a vacuum degree of 6.7 × 10⁻⁶. -2 When the temperature reaches 930-950℃, heating begins at a rate of 100℃ / min. Pressure of 10-50MPa is applied along the path. When the temperature reaches 930-950℃, the holding time is 100min. After the holding time is completed, the pressure is released.

[0038] (6) Remove the microchannel heat sink after it has been diffused and connected to the furnace and cooled down.

[0039] Example 2

[0040] The metal material is TC4 titanium alloy, and the manufactured part is a two-layer hollow aircraft skin prepared by superplastic forming / diffusion bonding method, as shown in the schematic diagram. Figure 6 In this embodiment, a high-quality diffusion bonding method for a hollow aircraft skin component made of TC4 titanium alloy is as follows:

[0041] (1) Cut the blank of the two-layer hollow aircraft skin according to the design drawings of the parts. Use 400#, 800#, 1500# and 2000# silicon carbide sandpaper to polish the surface burrs and oxide film on the surface to be diffused and connected in sequence. Clean with alcohol for 30 minutes to remove surface oil and powder dust. After cleaning, blow dry with cold air.

[0042] (2) Design a corresponding impact movement path and perform ultrasonic impact on the area of ​​the part surface that needs to be diffused and connected to prepare a 100 μm thick nanocrystalline layer on the surface of the blank. The impact treatment process parameters are as follows: ultrasonic amplitude is 30-40 μm, impact needle diameter is 3-4 mm, angle between impact needle and blank is 40-50°, impact speed is 60-80 mm / min, impact needle length is 18-24 mm, and the impact needle arrangement is a single row of multiple needles;

[0043] (3) Use 5000# sandpaper to sand the surface of the blank after ultrasonic impact, and then mechanically polish it to a mirror finish;

[0044] (4) The blank after ultrasonic impact is machined into diffusion connection parts for the skin of a two-layer hollow aircraft for later use.

[0045] (5) Assemble the machined parts with the mold, and place the whole assembly into a discharge plasma diffusion furnace with a vacuum degree of 6×10⁻⁶. -3When Pa, start heating at a heating rate of 80℃ / min, apply pressure of 2-30MPa along the path, and when the temperature reaches 850-870℃, hold for 60min. After the holding time is over, unload the pressure.

[0046] (6) The two-layer hollow aircraft skin part prepared by superplastic forming / diffusion bonding method is taken out after being cooled in the furnace.

[0047] Example 3

[0048] The metal material is 5083 aluminum alloy, and the manufactured part is a waveguide antenna prepared by a diffusion bonding method, as shown in the schematic diagram. Figure 5 In this embodiment, a high-quality diffusion connection method for a 5083 aluminum alloy waveguide antenna is as follows:

[0049] (1) Cut the waveguide antenna blank according to the design drawings of the part. Use 400#, 800#, 1500# and 2000# silicon carbide sandpaper to polish the surface burrs and oxide film on the surface to be diffused and connected in sequence. Clean with alcohol for 30 minutes to remove surface oil and powder dust. After cleaning, blow dry with cold air.

[0050] (2) Design a corresponding impact movement path and perform ultrasonic impact on the area of ​​the part surface that needs to be diffused and connected to prepare a nanocrystalline layer with a thickness of 80 μm on the surface of the blank. The impact treatment process parameters are as follows: ultrasonic amplitude is 10-20 μm, impact pin diameter is 5-6 mm, angle between impact pin and blank is 40-50°, impact speed is 60-80 mm / min, impact pin length is 18-24 mm, and the impact pin arrangement is an array of pins;

[0051] (3) Use 5000# sandpaper to sand the ultrasonic impact surface of the blank, and then mechanically polish it to a mirror finish;

[0052] (4) The blank after ultrasonic impact is machined into a diffusion connection part for waveguide antenna for later use.

[0053] (5) Assemble the machined parts with the mold, and place the whole assembly into a discharge plasma diffusion furnace with a vacuum degree of 6.7 × 10⁻⁶. -3 When Pa, start heating at a heating rate of 80℃ / min, apply pressure of 1~10MPa along the path, and when the temperature reaches 460~480℃, hold for 120min. After the holding time is over, unload the pressure.

[0054] (6) Remove the waveguide antenna after it has been diffused and connected and cooled in the furnace.

[0055] Example 4

[0056] The metallic material is GH4169 high-temperature alloy, and the manufactured parts are high-temperature heat exchangers for nuclear power plants prepared by diffusion bonding method, as shown in the schematic diagram. Figure 5 In this embodiment, a high-quality diffusion bonding method for a high-temperature heat exchanger made of GH4169 high-temperature alloy is as follows:

[0057] (1) Cut the high-temperature heat exchanger blank according to the design drawings of the part. Use 400#, 800#, 1500# and 2000# silicon carbide sandpaper to polish the surface burrs and oxide film on the surface to be diffused and connected in sequence. Clean with alcohol for 30 minutes to remove surface oil and powder dust. After cleaning, blow dry with cold air.

[0058] (2) Design a corresponding impact movement path and perform ultrasonic impact on the area of ​​the part surface that needs to be diffused and connected to prepare a nanocrystalline layer with a thickness of 130 μm on the surface of the blank. The impact treatment process parameters are as follows: ultrasonic amplitude is 40-50 μm, impact pin diameter is 4-5 mm, angle between impact pin and blank is 60-70°, impact speed is 200-220 mm / min, impact pin length is 18-24 mm, and the impact pin arrangement is an array of pins;

[0059] (3) Use 5000# sandpaper to sand the surface of the blank after ultrasonic impact, and then mechanically polish it to a mirror finish;

[0060] (4) The blank after ultrasonic impact is machined into a two-layer plate part with superplastic forming / diffusion bonding for later use.

[0061] (5) Assemble the machined parts with the mold, and place the whole assembly into a discharge plasma diffusion furnace with a vacuum degree of 6.7 × 10⁻⁶. -2 When the temperature reaches 1000-1050℃, start heating at a rate of 100℃ / min, apply pressure of 5-20MPa along the path, and hold for 60 minutes when the temperature reaches 1000-1050℃. After the holding time is over, unload the pressure.

[0062] (6) Remove the high-temperature heat exchanger parts after they have cooled with the furnace.

[0063] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements can be made without departing from the principle of the present invention, and these improvements should also be considered within the scope of protection of the present invention.

Claims

1. A method for improving the speed and quality of metal diffusion bonding using ultrasonic impact surface treatment, characterized in that, The method is as follows: Step 1: Cut and prepare the blank, and perform surface grinding and ultrasonic impact fine grain treatment on the blank; Step 2: Fine grinding and polishing of the surface of the blank; Step 3: Perform partial machining on the blank part; Step 4: Assemble the blanks and prepare the parts by rapid diffusion connection according to the selected process parameters.

2. The method for improving the speed and quality of metal diffusion bonding using ultrasonic impact surface treatment according to claim 1, characterized in that, The first step is as follows: 1.1 Cut the blank according to the design drawings of the parts and components, remove burrs, and grind to remove the oxide film on the surface to be diffused and connected; 1.2 Use sandpaper and a grinder to polish the surface of the blank to be subjected to ultrasonic impact treatment, and then clean it; 1.3 Following the designed impact movement path, ultrasonic impact is applied to the area on the surface of the part that requires diffusion connection, thereby preparing a nanocrystalline layer of a preset thickness on the surface of the blank.

3. The method for improving the speed and quality of metal diffusion bonding by ultrasonic impact surface treatment according to claim 1, characterized in that, Step two is to polish the uneven surface after impact, remove the thin layer of the surface nano-layer to achieve a mirror effect, ensure the surface is flat, and retain most of the nano-layer; Step three is to perform local machining on the blank after ultrasonic impact and polishing according to the part structure, and then prepare it for diffusion connection.

4. The method for improving the speed and quality of metal diffusion bonding by ultrasonic impact surface treatment according to claim 1, characterized in that, The fourth step is as follows: 4.1 Assemble the ultrasonically impacted parts and components, place them in the tooling according to the set process, and put the parts and tooling together into the discharge plasma diffusion furnace. After vacuuming, start heating after reaching the set value, and perform high-temperature diffusion bonding according to the predetermined rapid diffusion bonding process parameters. After the diffusion bonding is completed, unload the pressure. 4.2 Cool to room temperature, remove the diffusion connection parts and tooling, and obtain qualified products.

5. A method for improving the speed and quality of metal diffusion bonding using ultrasonic impact surface treatment according to claim 2, characterized in that, In step 1.2: the surface of the blank to be ultrasonically impacted is polished with sandpaper and a grinder, and then dried with cold air after cleaning.

6. A method for improving the speed and quality of metal diffusion bonding using ultrasonic impact surface treatment according to claim 2, characterized in that, In step 1.3, the ultrasonic impact treatment process parameters are as follows: ultrasonic amplitude is 10-50 μm, impact needle diameter is 3-6 mm, the angle between the impact needle and the blank is 40-80°, the impact speed is 50-300 mm / min, the impact needle length does not exceed 10 times the diameter, and the impact needle arrangement includes a single needle, a single row of multiple needles, and an array of needles; In step 1.3, the nanocrystal size obtained by ultrasonic impact is 10-100 nm, and the nanolayer thickness is 10-100 μm.

7. A method for improving the speed and quality of metal diffusion bonding using ultrasonic impact surface treatment according to claim 4, characterized in that, When the metallic material is TC4 titanium alloy, in step 4.1: the vacuum degree is 6.7 × 10⁻⁶. -3 When the pressure reaches 850-870℃, start heating at a rate of 20-100℃ / min. Apply varying pressure of 2-30MPa along the path. After the temperature reaches 850-870℃, maintain the temperature for 60 minutes. After the temperature maintenance is completed, unload the pressure.

8. A method for improving the speed and quality of metal diffusion bonding using ultrasonic impact surface treatment according to claim 4, characterized in that, When the metal material is 316L stainless steel, in step 4.1: the vacuum degree is 6.7 × 10⁻⁶. -2 When the pressure reaches 930-950℃, start heating at a rate of 20-100℃ / min. Apply pressure varying from 10 to 50 MPa along the path. After the temperature reaches 930-950℃, hold for 100 minutes. After the holding period, unload the pressure.

9. A method for improving the speed and quality of metal diffusion bonding using ultrasonic impact surface treatment according to claim 4, characterized in that, When the metal material is 5083 aluminum alloy, in step 4.1: the vacuum degree is 6.7 × 10⁻⁶. -3 When the pressure reaches 460-480℃, heating begins at a rate of 20-100℃ / min. Pressure is applied at varying rates of 1-10MPa along the path. After the temperature reaches 460-480℃, the temperature is maintained for 120 minutes. After the temperature maintenance is completed, the pressure is released.

10. A method for improving the speed and quality of metal diffusion bonding using ultrasonic impact surface treatment according to claim 4, characterized in that, When the metallic material is the high-temperature alloy GH4169, in step 4.1: the vacuum degree is 6.7 × 10⁻⁶. - 2 When the pressure reaches 1000-1050℃, start heating at a rate of 20-100℃ / min. Apply varying pressure of 5-20MPa along the path. After the temperature reaches 1000-1050℃, maintain the temperature for 60 minutes. After the temperature maintenance is completed, unload the pressure.

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