Method for manufacturing copper alloy-stainless steel heterogeneous material through hollow annular laser additive

Abstract

The invention discloses a hollow annular laser additive manufacturing method for a copper alloy-stainless steel heterogeneous material, which adopts a hollow annular laser additive manufacturing technology to realize defect-free forming of the copper alloy-stainless steel heterogeneous material, and realizes gradient change of interlayer energy density by adjusting laser power. And the prepared copper alloy-stainless steel heterogeneous material is good in interface and free of cracks and gap defects.

Description

Technical Field

[0001] The invention relates to the technical field of additive manufacturing of metal materials, and in particular to a method for manufacturing a copper alloy-stainless steel heterogeneous material through a hollow annular laser additive manufacturing method. Background Art

[0002] Additive manufacturing technology, as a cutting-edge digital manufacturing technology, is also known as 3D printing technology. Its core concept is to realize the direct forming of three-dimensional objects through the discrete-stacking principle. Compared with traditional manufacturing methods, additive manufacturing technology can directly manufacture parts with complex structures without specific molds, thereby significantly improving production efficiency and reducing production costs.

[0003] In the field of materials science, copper alloys and stainless steel are two important metal materials, each with unique physical and chemical properties. Copper alloys have good electrical and thermal conductivity, but relatively low strength and insufficient corrosion resistance; stainless steel, on the other hand, has excellent corrosion resistance and high strength, but relatively poor thermal and electrical conductivity. In order to fully utilize the advantages of these two materials, researchers have developed copper alloy-stainless steel heterogeneous materials. This bimetallic heterogeneous composite material combines the high electrical conductivity and high heat load of copper with the high strength and wear resistance of steel. Therefore, it has broad application prospects in many fields such as electrical and electronics, aerospace, equipment manufacturing, nuclear industry, and defense industry.

[0004] However, in the preparation process of copper alloy-stainless steel heterogeneous materials, the interface bonding strength directly affects the overall performance of heterogeneous composite materials. Laser additive manufacturing technology, with its high production efficiency and good metallurgical bonding between the substrate and the cladding layer, has shown great potential in the production of copper alloy-stainless steel heterogeneous metal composites. However, in practical applications, laser additive manufacturing technology also faces some challenges. Gaussian light source, as a commonly used light source type in laser additive manufacturing technology, has significant non-uniformity in its beam energy distribution. The energy of the Gaussian beam is mainly concentrated in the center of the beam, while the energy at the edge of the spot is relatively low. This localized energy input method leads to unbalanced heat input. In the welding process of copper alloy and stainless steel, this unbalanced heat input often leads to serious interface mixing and more crack and void defects, which seriously affects the interface quality and overall performance of the composite material.

[0005] Therefore, how to overcome the shortcomings of Gaussian light source laser additive manufacturing technology in the connection of copper alloy-stainless steel heterogeneous materials, improve the interface bonding strength, and reduce cracks and void defects has become a technical problem that needs to be solved urgently. Summary of the invention

[0006] To solve the above technical problems, the object of the present invention is to provide a method for manufacturing a copper alloy-stainless steel heterogeneous material by means of hollow annular laser additive manufacturing. Using the hollow annular laser additive manufacturing technology, through the gradient change of the energy density between layers, a copper alloy-stainless steel heterogeneous material with good interfaces, no cracks, and no void defects is prepared.

[0007] The above object of the present invention is achieved by the following technical solutions:

[0008] The present invention provides a method for manufacturing a copper alloy-stainless steel heterogeneous material by means of hollow annular laser additive manufacturing, comprising the following steps:

[0009] (1) Put the copper alloy powder into the powder feeder; fix the stainless steel substrate on the workbench of the inert gas protection box;

[0010] (2) Fill the inert gas protection box with inert gas. After the oxygen content is lower than 1000 ppm, turn on the powder feeder and perform single-pass multi-layer hollow annular laser additive manufacturing on the stainless steel substrate to deposit the copper alloy. The duty cycle of the laser spot of the hollow annular laser is 0.5-0.8. During the deposition process, gradually increase the laser power to obtain a copper alloy-stainless steel heterogeneous material.

[0011] The present invention adopts the method of gradient change of energy input between layers during hollow annular laser additive manufacturing to achieve defect-free manufacturing of heterogeneous materials. The hollow annular laser additive manufacturing technology uses a hollow annular laser different from the Gaussian light source. Based on the new idea of "hollow beam, centered powder tube, and powder feeding inside the light", through optical conversion, the Gaussian light is converted into annular hollow light, realizing the balance of the spot energy. The annular light reduces the problem of unbalanced heat distribution during metal melting and reduces the strong heat convection during the metal solidification process.

[0012] Further, in step (1), the particle size of the copper alloy powder is 45-153 microns.

[0013] Further, in step (1), the copper alloy powder is put into the powder feeder after being dried.

[0014] Further, the temperature of the drying treatment is 180-220 °C.

[0015] Further, in step (2), the inert gas is argon.

[0016] Further, in step (2), the surface of the stainless steel substrate is cleaned with acetone and / or alcohol.

[0017] Further, in step (2), the laser power for additive manufacturing deposition of the copper alloy is 900-1400 W.

[0018] Further, in step (2), the scanning speed of the additive manufacturing deposition of the copper alloy is 2 - 4 mm / s.

[0019] Further, in step (2), the lifting amount (i.e., the scanning layer thickness) of the additive manufacturing deposition of the copper alloy is 0.4 - 0.5 mm.

[0020] Further, in step (2), the powder feeding amount of the additive manufacturing deposition of the copper alloy is 1 - 2 g / min.

[0021] Further, in step (2), the specific method for gradually increasing the laser power during the deposition process is as follows: the laser power of the first layer is 800 - 1000 W, the laser power of the second layer is 1000 - 1200 W, and the laser power of the third layer and above is 1300 - 1400 W.

[0022] In the specific implementation manner, the method for additive manufacturing of a copper alloy - stainless steel heterogeneous material by a hollow annular laser includes the following steps:

[0023] (1) Dry the copper alloy powder and put the treated powder into a powder feeder; polish and clean the stainless steel substrate, and fix the treated stainless steel substrate on the workbench of an inert gas protection box.

[0024] (2) Fill the inert gas protection box with an inert gas. After the oxygen content is lower than 1000 ppm, turn on the powder feeder and perform single - pass multi - layer hollow annular laser additive manufacturing deposition of the copper alloy on the stainless steel substrate. Adjust the key deposition parameters in the laser additive manufacturing process, such as laser power, scanning speed, lifting amount, powder feeding amount, and duty cycle. Gradually increase the laser power during the deposition process to adjust the energy density of the annular light spot, and obtain a copper alloy - stainless steel heterogeneous material.

[0025] After the deposition is completed, wait for the copper alloy - stainless steel heterogeneous material to cool to room temperature and then take it out. Make a metallographic specimen, and the microstructure of the interface of the copper alloy - stainless steel heterogeneous metal deposited by the hollow annular laser additive manufacturing can be observed under an optical microscope.

[0026] The beneficial effects of the present invention:

[0027] The present invention uses the hollow annular laser additive manufacturing technology to connect heterogeneous metals. By utilizing the characteristic of the balanced distribution of the deposition energy of the hollow annular light spot, the imbalance of the heat distribution in the molten pool is reduced, the strong thermal convection and Marangoni convection in the molten pool are reduced, and further the mixing of interface elements is reduced, realizing the optimization of the interface quality between the copper alloy and the stainless steel. Considering the problem of the low laser absorption rate of the copper alloy and in order to ensure the interface quality, during the printing process, the energy density of the annular light spot is gradually increased, and finally, a copper alloy - stainless steel heterogeneous material connection with excellent interface quality, no cracks, and no voids is realized. Brief Description of the Drawings

[0028] Figure 1 It is the interface metallographic diagram of the solid and hollow ring laser additive manufacturing copper chromium zirconium alloy - 316L stainless steel heterogeneous material; among them, (a) is solid laser additive manufacturing, and (b) is the hollow ring laser additive manufacturing of Example 1.

[0029] Figure 2 It is the physical diagram of the copper chromium zirconium alloy - 316L stainless steel heterogeneous material prepared in Example 1 and Comparative Examples 1 - 3; among them, (a) is Comparative Example 1, (b) is Comparative Example 2, (c) is Comparative Example 3, and (d) is Example 1.

[0030] Figure 3 It is the optical microscope image of the cross-section of the copper chromium zirconium alloy - 316L stainless steel heterogeneous material prepared in Example 1; among them, (a) is the overall view, (b) is the partial enlarged view of the interface, and (c) is the corrosion diagram of the interface. Detailed Description of the Embodiments

[0031] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which this invention belongs. The terms used in the description of this invention herein are for the purpose of describing specific embodiments only and are not intended to limit the invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0032] The present invention will be further described below in conjunction with the drawings and specific embodiments, so that those skilled in the art can better understand the present invention and be able to implement it, but the examples given are not intended to limit the present invention.

[0033] Unless otherwise specified, the experimental methods used in the following examples are all conventional methods, and the materials, reagents, etc. used, unless otherwise specified, can be obtained from commercial channels.

[0034] Example 1

[0035] A method for manufacturing a hollow ring laser additive manufacturing copper chromium zirconium alloy - 316L stainless steel heterogeneous material, comprising the following steps:

[0036] (1) Dry the copper chromium zirconium alloy powder, and put the treated powder into a powder feeder; clean the surface of the 316L stainless steel substrate with acetone and perform sandblasting treatment, and fix the treated 316L stainless steel substrate on the workbench of an inert gas protection box.

[0037] (2) Fill the inert gas protection chamber with argon. After the oxygen content is lower than 1000 ppm, turn on the powder feeder and perform single-pass multi-layered hollow-ring laser additive manufacturing to deposit copper-chromium-zirconium alloy on a 316L stainless steel substrate. Set the scanning speed to 3 mm / s, the powder feeding rate to 1.5 g / min, the laser spot duty cycle to 0.68, the lift amount to 0.45 mm, and gradually increase the laser power: the laser power for the first layer deposition is 900 W, the laser power for the second layer deposition is 1100 W, and the laser power for the deposition starting from the third layer remains at 1300 W. After depositing 30 multi-layered thin walls, wait for the sample to cool to room temperature in the inert gas protection chamber to obtain a copper-chromium-zirconium alloy-316L stainless steel heterogeneous material.

[0038] Make the copper-chromium-zirconium alloy-316L stainless steel heterogeneous material prepared in Example 1 into a metallographic sample and observe the interface forming morphology under an optical microscope. As Figure 1 shown in (b), it can be seen that there is a connection of copper-chromium-zirconium-316L stainless steel dissimilar materials with excellent interface quality, no cracks, and no voids. Figure 1 In (a) is the interface microstructure morphology obtained under traditional solid spot deposition (laser power is 485 W, scanning speed is 533.5 mm / s, scanning pitch is 120 μm, and the reference is Martendal C, Esteves P, Deillon L, et al. Effects of beam shaping on copper-steel interfaces in multi-material laser beam powder bed fusion[J]. Journal of Materials Processing Tech., 2024, 327: 118344-.). It can be seen from the figure that the interface microstructure of the sample formed under the traditional solid spot is severely mixed, with many voids and crack defects, and the interface quality is poor.

[0039] Comparative Example 1

[0040] A method for manufacturing a copper-chromium-zirconium alloy-316L stainless steel heterogeneous material by hollow-ring laser additive manufacturing, comprising the following steps:

[0041] (1) Dry the copper-chromium-zirconium alloy powder and put the treated powder into the powder feeder; clean the surface of the 316L stainless steel substrate with acetone and perform sandblasting treatment, and fix the treated 316L stainless steel substrate on the workbench of the inert gas protection chamber.

[0042] (2) Fill the inert gas protection chamber with argon. After the oxygen content is lower than 1000 ppm, turn on the powder feeder and perform single-pass multi-layered hollow ring laser additive manufacturing to deposit copper-chromium-zirconium alloy on a 316L stainless steel substrate. Set the scanning speed to 3 mm / s, the powder feeding rate to 1.5 g / min, the laser spot duty cycle to 0.68, the lift amount to 0.45 mm, and keep the laser power unchanged at 900 W. After depositing 20 multi-layered thin walls, wait for the sample to cool to room temperature in the inert gas protection chamber to obtain a copper-chromium-zirconium alloy - 316L stainless steel heterogeneous material.

[0043] Comparative Example 2

[0044] A method for manufacturing a copper-chromium-zirconium alloy - 316L stainless steel heterogeneous material by hollow ring laser additive manufacturing is basically the same as that of Comparative Example 1, except that in step (2), the laser power is kept unchanged at 1100 W.

[0045] Comparative Example 3

[0046] A method for manufacturing a copper-chromium-zirconium alloy - 316L stainless steel heterogeneous material by hollow ring laser additive manufacturing is basically the same as that of Example 1, except that in step (2), the laser spot duty cycle of the hollow ring laser is 0.82.

[0047] The physical diagrams of the copper-chromium-zirconium alloy - 316L stainless steel heterogeneous materials prepared in Example 1 and Comparative Examples 1 - 3 are as Figure 2 shown. From Figure 2 (a), it can be found that for the thin wall sample formed under the condition of a constant power of 900 W in Comparative Example 1, with the increase of the deposition layer number, the forming quality deteriorates, and the hump phenomenon appears. With the increase of the deposition layer number, the hump phenomenon becomes more obvious and it is difficult to form. From Figure 2 (b), it can be found that in Comparative Example 2, with the increase of the deposition layer number, the hump phenomenon also appears significantly and it is difficult to form. From Figure 2 (c), it can be found that in Comparative Example 3, with the increase of the deposition layer number, unfused defects appear in both the middle and the edge of the thin wall, and it is difficult to form. From Figure 2 (d), it can be seen that the quality of the thin wall sample deposited and formed under the condition of gradually increasing the laser power in Example 1 is better.

[0048] Cut the copper-chromium-zirconium alloy - 316L stainless steel heterogeneous material prepared in Example 1 along the interface, and observe the interface bonding situation and the forming quality of the copper alloy under an optical microscope, as Figure 3 shown. Figure 3 (b) and (c) in Figure 3 are respectively the partial enlarged view and the corrosion diagram of the interface shown by the wireframe in 3(Cl), the etching solution obtained by mixing 15 mL of hydrochloric acid and 100 mL of water was added dropwise to the interface, and after 10 s, characterization was carried out to obtain an etching diagram. It can be found that the interface bonding quality is good, and no defects such as cracks and voids are found. Moreover, the microstructure of the formed part of the copper alloy is good. Except for a small number of micron-sized voids, no obvious defects are found. The microstructure morphology of Example 1 shows that the hollow ring laser additive manufacturing technology can achieve good interface and forming quality through the change of the energy density gradient between layers.

[0049] By comprehensively comparing the deposition experiments of Example 1 and Comparative Examples 1-3, it can be seen that the differences between Comparative Examples 1-3 and Example 1 are that no energy density gradient change between layers is carried out and a large-duty-cycle light spot is used. However, the forming quality of the samples in Example 1 is significantly better than that of Comparative Example 1 and Comparative Examples 2-3. Thus, it can be seen that under the condition of a suitable duty cycle (0.5-0.8), the present invention can achieve good forming quality through the adjustment of the energy density gradient change between layers.

[0050] This is because the traditional laser additive manufacturing technology uses a Gaussian beam as the energy input heat source. The laser energy of the Gaussian beam is mainly concentrated in the center of the beam, which is a localized energy input. The energy distribution between the edge and the center of the light spot is extremely uneven. The unbalanced heat input leads to a reduction in the quality of the dissimilar metal interface. Especially when connecting copper alloy-stainless steel dissimilar materials, problems such as serious interface mixing, cracks, and many void defects are likely to occur, making it difficult to meet the actual needs.

[0051] The hollow ring laser additive manufacturing technology avoids the problems existing in the Gaussian light source. Through optical conversion, the Gaussian light source is converted into a ring-shaped hollow light, achieving the balance of the light spot energy. The ring-shaped light reduces the problem of unbalanced heat distribution during metal melting, as well as reduces the strong thermal convection and Marangoni convection during the metal solidification process, and reduces the interface element mixing. Therefore, defect-free forming manufacturing of copper alloy-stainless steel can be successfully achieved. In addition, due to the change of the energy density gradient between layers in the present invention, some substrate elements diffuse, resulting in a decrease in the laser absorption rate of the molten pool between layers along the deposition direction. The change of the energy density gradient realizes the energy balance between layers, and finally defect-free copper alloy forming is achieved.

[0052] Copper has a relatively low laser absorption rate. The absorption rate of copper for a 1064 nm infrared pulsed laser is about 20%. Therefore, a relatively high laser power is required for laser additive manufacturing of copper alloys. However, when depositing the first layer of copper alloy on stainless steel, due to the presence of the stainless steel substrate, some stainless steel elements mix into the molten pool, resulting in a higher laser absorption rate of the molten pool elements. Therefore, too high a laser volume energy density is not required. An excessively high laser volume energy density will cause a large amount of mixing of interface elements and affect the interface quality. The laser power for the first layer deposition can be controlled at about 900 W. When depositing the second layer, it is deposited on the basis of the first layer. At this time, the deposited substrate becomes a copper alloy with a relatively low laser absorption rate. The first layer of copper alloy contains some substrate elements, and the laser absorption rate increases relatively. Considering comprehensively, when depositing the second layer, the laser power is controlled at about 1100 W. When depositing the third layer and above, the deposited substrate basically does not contain stainless steel elements. At this time, it is equivalent to depositing copper alloy on copper alloy, and the laser absorption rate of copper alloy is relatively low. Therefore, the laser power needs to be controlled at about 1300 W.

[0053] Obviously, the above embodiments of the present invention are only examples for clearly explaining the present invention, and are not intended to limit the implementation manners of the present invention. Those skilled in the art should understand that other different forms of changes or variations can be made on the basis of the above description. It is not necessary and impossible to enumerate all implementation manners here. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the claims of the present invention.

Claims

1. A method for hollow ring laser additive manufacturing of copper alloy-stainless steel heterogeneous materials, characterized in that: The following steps are involved: (1) Place copper alloy powder into a powder feeder; fix a stainless steel substrate on a workbench in an inert atmosphere protection box; (2) Inert gas is filled into the inert atmosphere protection box. When the oxygen content is lower than 1000 ppm, the powder feeder is turned on to perform single-pass multi-layer hollow ring laser additive manufacturing to deposit copper alloy on the stainless steel substrate. The laser spot duty ratio of the hollow ring laser is 0.5-0.

8. The laser power is gradually increased during the deposition process to obtain a copper alloy-stainless steel heterogeneous material.

2. The method according to claim 1, characterized in that In step (1), the particle size of the copper alloy powder is 45-153 microns.

3. The method according to claim 1, characterized in that In step (1), the copper alloy powder is placed in a powder feeder after being dried.

4. The method according to claim 3, characterized in that The temperature of the drying process is 180-220°C.

5. The method according to claim 1, characterized in that In step (2), the inert gas is argon.

6. The method according to claim 1, characterized in that In step (2), the laser power for the additive manufacturing of deposited copper alloy is 900-1400W.

7. The method according to claim 1, characterized in that In step (2), the scanning speed of the additive manufacturing deposited copper alloy is 2-4 mm / s.

8. The method according to claim 1, characterized in that In step (2), the lifting amount of the deposited copper alloy in additive manufacturing is 0.4-0.5 mm.

9. The method according to claim 1, characterized in that: In step (2), the powder feeding rate of the additively manufactured deposited copper alloy is 1-2 g / min.

10. The method according to claim 1, characterized in that In step (2), the specific method of gradually increasing the laser power during the deposition process is: the laser power of the first layer is 800-1000W, the laser power of the second layer is 1000-1200W, and the laser power of the third layer and above is 1300-1400W.

Images