Efficient laser cladding preparation method for nickel-based superalloy on surface of copper alloy

Abstract

The invention relates to the technical field of metallurgy preparation of heterogeneous materials, in particular to an efficient laser cladding preparation method of nickel-based superalloy on the surface of copper alloy, which comprises the following steps: increasing the absorptivity of the copper alloy to infrared laser through preheating, and carrying out laser cladding on GH3625 alloy on the surface of Cu-Cr-Zr alloy through regulating and controlling the components of a copper alloy / nickel alloy intermediate layer, so as to prepare the nickel-based superalloy on the surface of Cu-Cr-Zr alloy. And formation of a microstructure in the non-equilibrium solidification process is controlled, the process is optimized, and the mechanical property of the material is improved. According to the method, the intermediate layer is utilized to perform non-equilibrium state metallurgy preparation of the GH3625 alloy on the surface of the Cu-Cr-Zr base material, compared with the method without adding the intermediate layer, after the intermediate layer is added, the content of the copper element in a molten pool is increased, liquid-phase separation is promoted, a large-range Ni-Cr core shell is formed to serve as a low-energy nucleation site, crystal grains are refined, and the performance of the Cu-Cr-Zr alloy is improved. Further, a fine grain strengthening effect is achieved; the thickness of the element diffusion layer is also increased by adding the middle layer, the element uniformity is promoted, the dependence on Malangori is reduced, the heat input is reduced, the optimization of process parameters is realized, and the mechanical property of the heterogeneous material is further improved.

Description

Technical Field

[0001] This invention relates to the field of heterogeneous material metallurgical preparation technology, and proposes a method for preparing nickel-based high-temperature alloys on the surface of copper alloys by efficient laser cladding, specifically involving a non-equilibrium metallurgical preparation method of Cu-Cr-Zr alloys by laser GH3625 dissimilar metal. Background Technology

[0002] Heterogeneous materials, with their diverse compositions, structures, and other properties, combine the superior physical and mechanical properties of individual components into a single material, making them ideal for applications in industries such as nuclear power and aerospace. Copper and its alloys possess excellent thermal conductivity and mechanical properties, while nickel and its alloys exhibit superior strength, oxidation resistance, and high-temperature creep resistance. By joining and integrating copper and nickel alloys, their reliability and stability in extreme environments can be optimized. Copper / nickel alloy heterostructures are widely used in aerospace materials, including large heterometallic coupled rocket nozzles, rocket engine components, copper / nickel bimetallic heat exchangers, and rocket combustion chamber scaling components. Traditional manufacturing methods for these large components typically involve subtractive manufacturing—casting, machining, and assembly—which is inefficient, wasteful of materials, and costly.

[0003] Other commonly used methods for preparing heterogeneous materials include physical vapor deposition, thermal spraying, plasma spraying, and diffusion welding. However, these methods have limitations, such as low interfacial bonding strength, strict requirements for the preparation environment, poor material properties, and thin interfacial diffusion layers. Additive manufacturing (AM) offers many advantages in heterogeneous material fabrication, including high precision, high efficiency, and low waste. Its layer-by-layer, bottom-up processing characteristics allow for flexible transformation of material composition within the same part, providing a new method for preparing heterogeneous materials. Laser cladding has been widely used in the field of joining dissimilar alloys, enabling integrated design of materials, structures, and properties. There are two common types of laser additive manufacturing: selective laser melting (SLM) and direct energy deposition (DED). Although SLM is more precise, its production efficiency is lower compared to traditional machining. Directed energy deposition (DED) technology utilizes coaxial powder delivery in tandem with a laser to achieve rapid additive manufacturing, making it more suitable for manufacturing large parts, such as the fabrication of large copper / nickel alloy dissimilar metal couplings in the aerospace field, and is highly favored in the aerospace industry. DED employs multiple powder bins for coaxial powder delivery, allowing for the mixing of different materials and greatly expanding the flexibility in material composition design, making it more suitable for the fabrication of dissimilar materials. However, due to the significant differences in physical properties between dissimilar materials and the high thermal conductivity and high infrared laser reflectivity of copper alloys, some challenges remain when using directed energy deposition methods to fabricate copper / nickel alloy dissimilar materials.

[0004] To address the challenges of fabricating heteromaterials using laser-induced electro-optical fusion (DED) on copper alloy substrates, numerous studies have been conducted, including the use of shorter wavelength blue lasers, preheating, and the introduction of intermediate layers. Copper exhibits varying reflectivity to different laser wavelengths, with a reflectivity as high as 96% for infrared lasers (900-1100 nm) and only 34% for blue lasers (450 nm). CN 116791082 B solved the problem of high laser reflectivity on copper alloy surfaces by altering the laser wavelength during the cladding process, first emitting a short-wavelength laser beam followed by an infrared laser beam. However, the limited power, low production volume, high cost, and low efficiency of short-wavelength lasers restrict large-scale industrial applications. Since the laser reflectivity of copper alloys decreases with increasing temperature, preheating the copper alloy before cladding can increase its laser absorption rate during the cladding process. CN 112430811 A designed a heat preservation and preheating device to heat copper alloys to increase their laser absorption rate, achieving a good connection. However, this method requires a specific heat preservation and preheating device, making the process complex and costly, unsuitable for large-scale industrial production. Due to differences in solubility, crystal structure, thermal conductivity, and coefficient of thermal expansion, direct joining of dissimilar materials generates high residual stress, leading to cracking failure. Introducing an intermediate layer with different material or compositional gradients can alleviate the differences in physical properties between dissimilar materials, reduce residual stress, and thus improve the process and performance. CN 103805990 B prepared a high-wear-resistant coating by pre-forming cladding powder into a paste with an adhesive, coating it onto a copper alloy substrate, and then performing laser cladding. However, this method is cumbersome and does not demonstrate the advantages of additive manufacturing, such as high efficiency and fast forming speed. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a method for preparing nickel-based high-temperature alloys by high-efficiency laser cladding on copper alloy surfaces.

[0006] The specific technical solution is as follows: A high-efficiency laser cladding method for nickel-based superalloys on copper alloy surfaces is proposed. This method increases the absorption rate of the copper alloy to infrared lasers through preheating and controls the composition of the copper / nickel alloy interlayer. GH3625 alloy is then laser-clad onto the surface of a Cu-Cr-Zr alloy, controlling the formation of microstructures during non-equilibrium solidification. The specific steps are as follows: (1) The Cu-Cr-Zr substrate was sanded and pretreated by laser heating; First, the Cu-Cr-Zr substrate is sanded with 60-400 grit sandpaper to remove oxides, impurities and oil stains from the surface. Then, the sanded Cu-Cr-Zr substrate is preheated by laser scanning. (2) Weigh Cu-Cr-Zr powder and GH3625 powder, prepare intermediate layer powder according to a certain mass fraction percentage, place the prepared powder in a ball mill mixer at a certain speed for a period of time with a ball-to-material ratio of 1:2, dry the powder after ball milling, and store it under vacuum. (3) Polish the Cu-Cr-Zr substrate with 60-80 grit sandpaper to remove oxides, impurities and oil stains from the surface; (4) After sanding the Cu-Cr-Zr substrate with sandpaper, a laser scanning preheating treatment is performed; (5) Use appropriate parameters for the cladding of the intermediate layer; The ball-milled intermediate layer powder and GH3625 powder are placed in a powder feeding hopper, and the ball-milled intermediate layer powder is transported for the first layer deposition. (6) Use appropriate parameters to perform GH3625 cladding and transport GH3625 powder for subsequent deposition.

[0007] The raw materials used in step (1) are composed of the following components by mass percentage: Cr 1.00%, Zr 0.122%, with the balance consisting of copper and unavoidable impurities; the size of the Cu-Cr-Zr substrate is 100mm*100mm*15mm.

[0008] In step (1), the laser scanning head is tilted at 15°-30° to preheat the target area of ​​the Cu-Cr-Zr substrate. The laser spot is 3mm, the working distance is 17-20mm, the laser power is 1000-2000W, the scanning speed is 5-10mm / s, the horizontal overlap is 50-80%, the offset is 0.9-2.3mm, and the scanning is repeated 1-3 times after a single layer is completed, for a total of 2-4 times.

[0009] The Cu-Cr-Zr powder used in step (2) consists of the following components by mass percentage: Cr 0.91%, Zr 0.17%, with the balance being copper and unavoidable impurities; the particle size distribution of the Cu-Cr-Zr powder is: 53μm-150μm, D10=50.48μm, D50=83.38μm, D90=123.5μm; the GH3625 powder used in step (2) consists of the following components by mass percentage: Cr 20.69%, Mo 8.47%, Nb 3.64%, Co 0.18%, Si 0.16%, Ti 0.065%, Cu 0.061%, Zr 0.03%, Al 0.024%, with the balance consisting of nickel and unavoidable impurities; the particle size distribution of GH3625 powder is: 53μm-150μm, D10=78.3μm, D50=107.6μm, D90=146.7μm; the mass fraction percentages of Cu-Cr-Zr powder and GH3625 powder mentioned in step (2) are 60%-80% for GH3625 and 20%-40% for Cu-Cr-Zr. The rotation speed of the ball mill mixer in step (2) is 200-230 r / min, and the mixing time is 60 min-180 min.

[0010] The drying temperature of the intermediate layer powder after ball milling in step (2) is 60-80℃, and the drying time is 2-4h.

[0011] In step (4), the laser head is tilted at 15°-30° to preheat the Cu-Cr-Zr substrate by scanning the target area with a laser. The laser spot is 3 mm, the working distance is 17-20 mm, the laser power is 1000-2000 W, the scanning speed is 5-10 mm / s, and the horizontal overlap is 50-80% (offset 0.9-2.3 mm). After scanning a single layer, the process is repeated 1-3 times, for a total of 2-4 times.

[0012] In step (5), the first layer deposition is performed with a laser spot size of 3 mm, a working distance of 17-20 mm, a laser power of 2500-4000 W, a scanning speed of 5-10 mm / s, a horizontal overlap rate of 50-80%, an offset of 0.9-2.3 mm, a powder feeding rate of 0.4-1.0 r / min, and 1-2 layers of cladding. After cladding is completed, the laser is turned off and the laser is allowed to cool for 1-5 minutes.

[0013] In step (6), the subsequent deposition process involves a laser spot size of 3 mm, a working distance of 17-20 mm, a laser power of 600-1500 W, a scanning speed of 5-10 mm / s, a horizontal overlap rate of 50-80%, an offset of 0.9-2.3 mm, a powder feeding rate of 0.4-1.0 r / min, and after each layer of cladding is completed, the laser is turned off and the process is allowed to cool for 1-5 minutes before proceeding to the next layer of cladding.

[0014] Compared with the prior art, the present invention has the following beneficial technical effects: Existing processes for preparing heterogeneous materials using laser cladding on copper alloy surfaces mostly require additional equipment, such as blue lasers and specialized heat preservation and preheating devices. These processes are lengthy and costly, limiting their practical production applications. This invention utilizes an intermediate layer to perform non-equilibrium metallurgical preparation of GH3625 alloy on a Cu-Cr-Zr substrate. Compared to the process without an intermediate layer, the addition of the intermediate layer increases the copper content in the molten pool, promotes liquid-phase separation, and forms a large-scale Ni-Cr core-shell as low-energy nucleation sites, refining the grains and resulting in a grain-refining strengthening effect. The intermediate layer also increases the thickness of the element diffusion layer, promoting elemental uniformity and reducing dependence on Marangoni alloys. This reduces overall heat input while altering the non-equilibrium solidification process in the molten pool, leading to an overall improvement in the performance of the copper / nickel alloy heterogeneous material.

[0015] This invention utilizes a non-equilibrium solidification method for preparing GH3625 alloy by laser cladding an intermediate layer onto the surface of a Cu-Cr-Zr alloy. By improving preheating and intermediate layer processes and controlling microstructure and mechanical properties using only a common red laser, it achieves non-equilibrium metallurgical preparation of copper / nickel alloys, which is of great significance for the widespread application of heterogeneous material preparation. Employing a coaxial powder feeding laser additive manufacturing method, it is possible to prepare heterogeneous materials with excellent metallurgical bonding at low cost and high efficiency. The intermediate layer powder is directly obtained through ball milling and mixing, eliminating the need for binders. Preheating of the copper alloy substrate is also achieved directly via laser, requiring no other equipment. The preparation process is simple, efficient, and cost-effective. This invention fills a gap in copper / nickel heterogeneous material preparation technology in the field of laser additive manufacturing research, proposes an integrated solution for process control in laser additive manufacturing technology, and lays the foundation for research in the non-equilibrium metallurgical preparation of heterogeneous materials. This invention solves the problems of high reflectivity and significant differences in physical properties between the substrate and the cladding layer in laser additive manufacturing of copper alloy surfaces by employing a process design of laser preheating and ball milling powder mixing, thus simplifying the experimental procedure. Compared to laser preheating and high-power laser cladding methods without an intermediate layer, the introduction of an intermediate layer reduces the cladding power by 25% and improves tensile properties by 10.6%, shear properties by 21.4%, and hardness by 31.8%. Attached Figure Description

[0016] Figure 1 SEM microstructure of the intermediate layer heterogeneous material prepared by non-equilibrium metallurgy in Example 1; Figure 2 The elemental distribution of the intermediate layer heterogeneous material prepared by non-equilibrium metallurgy in Example 1 is shown. Figure 3 EBSD microstructure of the intermediate layer heterogeneous material prepared by non-equilibrium metallurgy in Example 1; Figure 4 The tensile test results for heterogeneous materials without an intermediate layer and with an intermediate layer prepared by non-equilibrium metallurgy in Example 1 are shown. Figure 5 The results of shear tests for heterogeneous materials without and with intermediate layers prepared by non-equilibrium metallurgy in Example 1 are shown. Figure 6 The surface hardness distribution of the intermediate layer heterogeneous material prepared by non-equilibrium metallurgy in Example 1; Figure 7 SEM microstructure of the intermediate layer heterogeneous material prepared by non-equilibrium metallurgy in Example 2; Figure 8 The OM microstructure of Case 1, a failure of non-equilibrium metallurgical preparation of intermediate layer heterostructure material, is shown in Comparative Example 1. Figure 9 To prepare the OM microstructure of the heteromaterial without intermediate layer using non-equilibrium metallurgy in Comparative Example 2; Figure 10 The elemental distribution of heteromaterials without intermediate layers prepared by non-equilibrium metallurgy in Comparative Example 2; Figure 11 EBSD microstructure of heteromaterial without intermediate layer was prepared by non-equilibrium metallurgy for Comparative Example 2; Figure 12 The surface hardness distribution of heterogeneous materials without intermediate layers was prepared using non-equilibrium metallurgy as a comparative example 2. Figure 13 The OM microstructure of the failed case of non-equilibrium metallurgical preparation of intermediate layer heterostructure in Comparative Example 3; Figure 14 The OM microstructure of the failed case of non-equilibrium metallurgical preparation of intermediate layer heterostructure in Comparative Example 4; Figure 15 The OM microstructure of the failed case of non-equilibrium metallurgical preparation of intermediate layer heterostructure in Comparative Example 5; Detailed Implementation

[0017] The present invention will now be described in detail with reference to specific embodiments and accompanying drawings, but the scope of protection of the present invention is not limited to the specific embodiments and accompanying drawings. Example

[0018] A high-efficiency laser cladding method for nickel-based superalloys on copper alloy surfaces is proposed. This method increases the absorption rate of the copper alloy to infrared lasers through preheating and controls the composition of the copper / nickel alloy interlayer. GH3625 alloy is then laser-clad onto the surface of a Cu-Cr-Zr alloy, controlling the formation of microstructures during non-equilibrium solidification. The specific steps are as follows: (1) The Cu-Cr-Zr substrate was sanded and pretreated by laser heating; First, the Cu-Cr-Zr substrate is polished with 60-grit sandpaper to remove oxides, impurities, and oil stains from the surface. Coarser sandpaper increases the cleaning efficiency and produces deeper scratches, which is more conducive to increasing the surface area and thus improving interface bonding. Sanding also increases the surface roughness of the Cu-Cr-Zr substrate, increasing the surface area and allowing the cladding material to better bond with the substrate surface during the non-equilibrium metallurgical process. The raw materials used in the Cu-Cr-Zr substrate consist of the following components by mass percentage: Cr 1.00%, Zr 0.122%, with the balance consisting of copper and unavoidable impurities. The dimensions of the Cu-Cr-Zr substrate are 100mm*100mm*15mm. The substrate should be thick enough to avoid thermal deformation during the non-equilibrium metallurgical process.

[0019] The Cu-Cr-Zr substrate, after being sanded with sandpaper, is then preheated using laser scanning. Laser scanning eliminates the need for additional equipment, reducing process complexity and preventing interface cracking caused by heat accumulation due to poor heat dissipation on the hot plate. The laser scanning head is tilted at 15°-30° to preheat the target area of ​​the Cu-Cr-Zr substrate. The laser spot size is 3mm, the working distance is 18mm, the laser power is 2000W, the scanning speed is 10mm / s, the horizontal overlap is 66%, and the offset is 1.6mm. The scan is repeated once after each layer is completed, for a total of 2 scans.

[0020] (2) Weigh Cu-Cr-Zr powder and GH3625 powder, and prepare intermediate layer powder according to a certain mass fraction percentage. With a ball-to-powder ratio of 1:2, place the prepared powder in a ball mill mixer and mix at a speed of 230 r / min for 120 min. Since Cu has low hardness, excessively high speed will aggravate the impact and extrusion force between the grinding balls and the powder, thereby producing a cold welding phenomenon and affecting the powder flowability. After ball milling, dry the powder at 80℃ for 2 h and store it under vacuum. The raw materials used in the Cu-Cr-Zr powder consist of the following components by mass percentage: Cr 0.91%, Zr 0.17%, with the balance being copper and unavoidable impurities; the particle size distribution of the Cu-Cr-Zr powder is: 53μm-150μm, D10=50.48μm, D50=83.38μm, D90=123.5μm; The raw materials used in the GH3625 powder are composed of the following components by mass percentage: Cr 20.69%, Mo 8.47%, Nb 3.64%, Co 0.18%, Si 0.16%, Ti 0.065%, Cu 0.061%, Zr 0.03%, Al 0.024%, with the balance consisting of nickel and unavoidable impurities; the particle size distribution of the GH3625 powder is: 53μm-150μm, D10=78.3μm, D50=107.6μm, D90=146.7μm; The mass fraction percentages of the Cu-Cr-Zr powder and GH3625 powder are 70% GH3625 and 30% Cu-Cr-Zr. (3) Polish the Cu-Cr-Zr substrate with 60-mesh sandpaper to remove oxides, impurities and oil stains on the surface. Sandpaper polishing can increase the roughness of the Cu-Cr-Zr substrate surface and increase the surface area, so that the cladding material can better interlock with the substrate surface during the non-equilibrium metallurgical process. (4) After sanding the Cu-Cr-Zr substrate with sandpaper, laser scanning is used for preheating treatment. Laser scanning can reduce the complexity of the process without the need for additional equipment, and can also avoid interface cracking caused by heat accumulation due to poor heat dissipation of the hot table. In the preheating treatment, the laser head is tilted at 15°-30° to preheat the Cu-Cr-Zr substrate by laser scanning the target area. The laser spot is 3 mm, the working distance is 18 mm, the laser power is 2000 W, the scanning speed is 10 mm / s, the horizontal overlap is 66%, the offset is 1.6 mm, and the single-layer scanning is repeated once, for a total of 2 times.

[0021] (5) Use appropriate parameters for the cladding of the intermediate layer; The ball-milled intermediate layer powder and GH3625 powder are placed in a powder feeding hopper. The ball-milled intermediate layer powder is then fed for the first layer deposition. The first layer deposition is performed with a laser spot size of 3 mm, a working distance of 18 mm, a laser power of 3000 W, a scanning speed of 10 mm / s, a horizontal overlap rate of 66%, an offset of 1.6 mm, and a powder feeding rate of 0.5 r / min. One layer is clad to obtain an intermediate layer with a thickness of 0.6 mm. After the intermediate layer cladding is completed, the laser is turned off, and 2 minutes are allowed for heat release to avoid heat accumulation and cracking.

[0022] (6) GH3625 is clad with appropriate parameters. GH3625 powder is then fed for subsequent deposition. The subsequent deposition parameters are: laser spot size 3 mm, working distance 18 mm, laser power 800 W, scanning speed 10 mm / s, horizontal overlap rate 66%, offset 1.6 mm, and powder feed rate 0.5 r / min, to obtain a single layer of GH3625 with a thickness of 0.6 mm. After each cladding layer is completed, the laser is turned off and the heat is allowed to dissipate for 2 minutes to prevent heat accumulation and cracking. Then, the next cladding layer is performed.

[0023] The interface organization obtained in Example 1 is as follows Figure 1 As shown, the interface between the Cu-Cr-Zr substrate and the intermediate layer shows no obvious pores or cracks, indicating good interfacial bonding. The intermediate layer consists of fine equiaxed grains of 30.3 μm. Figure 3 The substructure consists of a nickel- and chromium-rich core-shell structure and a copper-rich mesh distributed around it. Figure 2 The tensile strength is 344.5 MPa. Figure 4 The shear strength is 237.9 MPa. Figure 5 The hardness of the intermediate layer is 234.4 HV (). Figure 6 ). Example

[0024] The difference from Example 1 is that in step (1), the Cu-Cr-Zr substrate is preheated by scanning the target area with a laser. The working distance is 17mm, the laser power is 1000W, the scanning speed is 5mm / s, the horizontal overlap is 50%, the offset is 0.9mm, and the scanning is repeated twice after a single layer is completed, for a total of 3 times.

[0025] In step (2), the powder is mixed at a speed of 230 r / min for 120 min in a ball mill. After ball milling, the powder is dried at 80°C for 2 h. In step (4), the working distance is 18 mm, the laser power is 1000W, the scanning speed is 5 mm / s, the horizontal overlap is 50%, the offset is 0.9 mm, and the single-layer scanning is repeated twice, for a total of 3 times.

[0026] In step (5), the working distance for the first layer deposition is 17mm, the laser power is 2500W, the scanning speed is 5mm / s, the horizontal overlap rate is 50%, the offset is 0.9mm, the powder feeding rate is 0.4r / min, one layer is clad, and after cladding is completed, the laser is turned off and waits for 1 minute for it to cool down.

[0027] In step (6), the working distance for subsequent deposition is 17 mm, the laser power is 600 W, the scanning speed is 5 mm / s, the horizontal overlap rate is 50%, the offset is 0.9 mm, the powder feeding rate is 0.4 r / min, the laser is turned off after each layer is clad, and it is allowed to cool down for 1 minute before the next layer is clad.

[0028] The interface organization obtained in Example 2 is as follows Figure 7 As shown, the interface between the Cu-Cr-Zr substrate and the intermediate layer has no obvious pores or cracks, and the interface bonding is good. The microstructure of the intermediate layer consists of a distribution of coarse island-like structures and fine spherical structures. Example

[0029] The difference from Example 1 is that in step (1), the Cu-Cr-Zr substrate is preheated by scanning the target area with a laser. The working distance is 20mm, the laser power is 2000W, the scanning speed is 8mm / s, the horizontal overlap is 80%, the offset is 2.3mm, and the scan is repeated 3 times after a single layer is completed, for a total of 4 times.

[0030] In step (2), the powder is mixed at a speed of 200 r / min for 180 min in a ball mill. After ball milling, the powder is dried at 80°C for 4 h and then stored under vacuum. The mass fraction percentages of the Cu-Cr-Zr powder and GH3625 powder are 80% GH3625 and 20% Cu-Cr-Zr. In step (4), the preheating process is performed at a working distance of 20 mm, a laser power of 2000 W, a scanning speed of 10 mm / s, a horizontal overlap of 80%, an offset of 2.3 mm, and is repeated twice after a single layer is scanned, for a total of 4 times.

[0031] In step (5), the first layer deposition has a working distance of 17 mm, a laser power of 2500 W, a scanning speed of 5 mm / s, a horizontal overlap rate of 50%, an offset of 0.9 mm, a powder feeding rate of 0.4 r / min, and cladding of 1 layer. After cladding is completed, the laser is turned off and waits for 1 minute for it to cool down.

[0032] The subsequent deposition in step (6) has a working distance of 20 mm, a laser power of 1500 W, a scanning speed of 10 mm / s, a horizontal overlap rate of 80%, an offset of 2.3 mm, a powder feeding rate of 1.0 r / min, and after each layer of cladding is completed, the laser is turned off and waited for 5 minutes to cool down before proceeding with the next layer of cladding.

[0033] Comparative example: To illustrate the effectiveness of the method of the present invention, the following comparative example was conducted. The specific implementation process was as follows: five variables were set: preheating method, presence or absence of intermediate layer, intermediate layer composition, GH3625 power, and waiting time. A control group was set up, and the interface morphology was used as the result to judge the bonding effect of dissimilar metals.

[0034] Comparative Example 1: (1) Select GH3625 and Cu-Cr-Zr spherical powders with a particle size range of 53-150 μm, weigh out powders with a mass fraction of 70% GH3625 and 30% Cu-Cr-Zr, place them in a ball mill mixer and mix at a speed of 230 r / min for 120 min (actual working time), and then dry at 80 ℃ for 2 h for storage.

[0035] (2) For the surface treatment of Cu-Cr-Zr substrate, 60-grit sandpaper is used for polishing, followed by rinsing with alcohol to remove oil and oxide layer from the surface and increase laser refractive index.

[0036] (3) The Cu-Cr-Zr substrate is preheated using a hot table. The hot table temperature is set to 200 ℃. After reaching the target temperature, it is kept at the temperature for 5 min. Then the hot table is turned off to carry out the subsequent intermediate layer cladding work.

[0037] (4) The ball-milled powder was then fed to the intermediate layer for cladding. The laser spot size was 3 mm, the working distance was 18 mm, the power was 3000 W, the scanning speed was 10 mm / s, the horizontal overlap rate was 66% (offset 1.6 mm), the powder feeding rate was 0.5 r / min, and one layer was clad to obtain an intermediate layer with a thickness of 0.6 mm. After the intermediate layer cladding was completed, the laser was turned off and waited for 2 min.

[0038] (5) GH3625 powder was then fed for subsequent cladding. The laser spot size was 3 mm, the working distance was 18 mm, the power was 1000 W, the scanning speed was 10 mm / s, the horizontal overlap rate was 66% (offset 1.6 mm), and the powder feeding rate was 0.5 r / min, resulting in a single layer of GH3625 with a thickness of 0.6 mm. After each layer was clad, the laser was turned off and waited for 2 minutes before proceeding with the next layer.

[0039] The interface organization obtained in Comparative Example 1 is as follows Figure 8 As shown, there are obvious defects at the interface between the Cu-Cr-Zr substrate and the intermediate layer, and there are also large longitudinal cracks in the fusion zone. Due to the fact that the hot stage is not conducive to the subsequent heat release, the generated thermal stress is large, resulting in cracks and poor interface bonding. Comparative Example 2 (1) For the surface treatment of Cu-Cr-Zr substrate, 60-grit sandpaper is used for polishing, followed by rinsing with alcohol to remove oil and oxide layer from the surface and increase laser refractive index.

[0040] (2) The Cu-Cr-Zr substrate was preheated by laser scanning. The laser spot used for preheating was 3 mm, the working distance was 18 mm, the power was 2000 W, the scanning speed was 10 mm / s, the horizontal overlap rate was 66% (offset 1.6 mm), and the single-layer scanning was repeated twice, for a total of 3 times.

[0041] (3) Directly feed GH3625 powder for subsequent cladding. The laser spot size is 3mm, the working distance is 18mm, the power is 4000W for cladding one layer, then 2000W for cladding two layers, and 800W for the remaining layers. The scanning speed is 10 mm / s, the horizontal overlap rate is 66% (offset 1.6mm), and the powder feeding rate is 0.5r / min.

[0042] The interface organization obtained in Comparative Example 2 is as follows Figure 9 As shown, without the addition of an intermediate layer, after process adjustments, the interface between the Cu-Cr-Zr substrate and the intermediate layer also showed no obvious defects, but the microstructure differed significantly from that of the intermediate layer, with the fusion zone consisting of coarse columnar crystals of 111.5 μm. Figure 11 The substructure consists of alternating long lamellae rich in nickel and chromium and long lamellae rich in copper, with the copper-rich lamellae also containing a core-shell structure rich in nickel and chromium. Figure 10 The tensile strength is 311.9 MPa. Figure 4 The shear strength is 196.1 MPa. Figure 5 The hardness of the fusion zone is 177.8 HV ( Figure 12 ).

[0043] Comparative Example 3 (1) Select GH3625 and Cu-Cr-Zr spherical powders with a particle size range of 53-150μm, weigh out powders with a mass fraction of 70% GH3625 and 30% Cu-Cr-Zr, place them in a ball mill mixer and mix at a speed of 230 r / min for 120 min (actual working time), and then dry at 80 ℃ for 2 h for storage.

[0044] (2) Select GH3625 and Cu-Cr-Zr spherical powders with a particle size range of 53-150 μm, weigh out powders with a mass fraction of 90% GH3625 and 10% Cu-Cr-Zr, place them in a ball mill and mix at a speed of 230 r / min for 120 min (actual working time), and then dry at 80℃ for 2 h for storage.

[0045] (3) For the surface treatment of Cu-Cr-Zr substrate, 60-grit sandpaper is used for polishing, followed by rinsing with alcohol to remove oil and oxide layer from the surface and increase laser refractive index.

[0046] (4) The Cu-Cr-Zr substrate was preheated by laser scanning. The laser spot used for preheating was 3mm, the working distance was 18mm, the power was 2000W, the scanning speed was 10mm / s, the horizontal overlap rate was 66% (offset 1.6mm), and the single-layer scanning was repeated twice, for a total of 3 times.

[0047] (5) Subsequently, GH3625:Cu-Cr-Zr=7:3 (mass%) ball-milled powder was fed for intermediate layer cladding. The laser spot size was 3 mm, the working distance was 18 mm, the power was 3000 W, the scanning speed was 10 mm / s, the horizontal overlap rate was 66% (offset 1.6 mm), the powder feeding rate was 0.5 r / min, and one layer was clad to obtain an intermediate layer with a thickness of 0.6 mm. After the intermediate layer cladding was completed, the laser was turned off and waited for 2 min.

[0048] (6) Subsequently, the ball-milled powder of GH3625:Cu-Cr-Zr=9:1 (mass%) was fed to perform intermediate layer cladding. The laser spot size was 3mm, the working distance was 18mm, the power was 3000W, the scanning speed was 10mm / s, the horizontal overlap rate was 66% (offset 1.6mm), the powder feeding rate was 0.5r / min, and one layer was clad to obtain an intermediate layer with a thickness of 0.6mm. After the intermediate layer cladding was completed, the laser was turned off and waited for 2 minutes.

[0049] (7) GH3625 powder was then fed for subsequent cladding. The laser spot size was 3 mm, the working distance was 18 mm, the power was 1500 W, the scanning speed was 10 mm / s, the horizontal overlap rate was 66% (offset 1.6 mm), and the powder feeding rate was 0.5 r / min, resulting in a single layer of GH3625 with a thickness of 0.6 mm. After each layer was clad, the laser was turned off and waited for 2 minutes before proceeding with the next layer.

[0050] The interface organization obtained in Comparative Example 3 is as follows Figure 13 As shown, there are also obvious defects and large longitudinal cracks in the fusion zone. Higher power will generate greater heat accumulation, resulting in greater thermal stress and cracks. The interface bonding is also poor.

[0051] Comparative Example 4 (1) Select GH3625 and Cu-Cr-Zr spherical powders with a particle size range of 53-150μm, weigh out powders with a mass fraction of 70% GH3625 and 30% Cu-Cr-Zr, place them in a ball mill mixer and mix at a speed of 230r / min for 120min (actual working time), then dry at 80℃ for 2h and store.

[0052] (2) For the surface treatment of Cu-Cr-Zr substrate, 60-grit sandpaper is used for polishing, followed by rinsing with alcohol to remove oil and oxide layer from the surface and increase laser refractive index.

[0053] (3) The Cu-Cr-Zr substrate was preheated by laser scanning. The laser spot used for preheating was 3mm, the working distance was 18mm, the power was 2000W, the scanning speed was 10mm / s, the horizontal overlap rate was 66% (offset 1.6mm), and the single-layer scanning was repeated twice, for a total of 3 times.

[0054] (4) The ball-milled powder was then fed to the intermediate layer for cladding. The laser spot size was 3 mm, the working distance was 18 mm, the power was 3000 W, the scanning speed was 10 mm / s, the horizontal overlap rate was 66% (offset 1.6 mm), the powder feeding rate was 0.5 r / min, and one layer was clad to obtain an intermediate layer with a thickness of 0.6 mm. After the intermediate layer cladding was completed, the laser was turned off and waited for 2 minutes.

[0055] (5) GH3625 powder was then fed for subsequent cladding. The laser spot size was 3 mm, the working distance was 18 mm, the power was 1500 W, the scanning speed was 10 mm / s, the horizontal overlap rate was 66% (offset 1.6 mm), and the powder feeding rate was 0.5 r / min, resulting in a single layer of GH3625 with a thickness of 0.6 mm. After each layer was clad, the laser was turned off and waited for 2 minutes before proceeding with the next layer.

[0056] The interface organization obtained in Comparative Example 4 is as follows Figure 14 As shown, there are also obvious defects and large longitudinal cracks in the fusion zone. Higher power will generate greater heat accumulation, resulting in greater thermal stress and cracks. The interface bonding is also poor.

[0057] Comparative Example 5 (1) Select GH3625 and Cu-Cr-Zr spherical powders with a particle size range of 53-150μm, weigh powders with a mass fraction of 70% GH3625 and 30% Cu-Cr-Zr, place them in a ball mill mixer and mix at a speed of 230r / min for 120min (actual working time), then dry at 80℃ for 2h and store.

[0058] (2) For the surface treatment of Cu-Cr-Zr substrate, 60-grit sandpaper is used for polishing, followed by rinsing with alcohol to remove oil and oxide layer from the surface and increase laser refractive index.

[0059] (3) The Cu-Cr-Zr substrate was preheated by laser scanning. The laser spot used for preheating was 3mm, the working distance was 18mm, the power was 2000W, the scanning speed was 10mm / s, the horizontal overlap rate was 66% (offset 1.6mm), and the single-layer scanning was repeated twice, for a total of 3 times.

[0060] (4) The ball-milled powder is then fed in for intermediate layer cladding. The laser spot size is 3 mm, the working distance is 18 mm, the power is 3000 W, the scanning speed is 10 mm / s, the horizontal overlap rate is 66% (offset 1.6 mm), the powder feeding rate is 0.5 r / min, and one layer is clad to obtain an intermediate layer with a thickness of 0.6 mm. After the intermediate layer is clad, there is no waiting time, and the next layer is clad directly.

[0061] (5) GH3625 powder was then fed for subsequent cladding. The laser spot size was 3 mm, the working distance was 18 mm, the power was 1000 W, the scanning speed was 10 mm / s, the horizontal overlap rate was 66% (offset 1.6 mm), and the powder feeding rate was 0.5 r / min, resulting in a single layer of GH3625 with a thickness of 0.6 mm. After each layer of cladding was completed, there was no waiting period before proceeding directly to the next layer.

[0062] The interface organization obtained in Comparative Example 5 is as follows Figure 15 As shown, there are obvious defects at the interface between the Cu-Cr-Zr substrate and the intermediate layer, as well as obvious defects and large longitudinal cracks in the fusion zone. Without adding a waiting time, heat release is not conducive, resulting in large thermal stress and cracks. The interface bonding is poor.

[0063] In the process of laser cladding GH3625 dissimilar metal onto the surface of a Cu-Cr-Zr alloy using DED, due to the high reflectivity of the copper alloy to infrared lasers, sandpaper polishing and laser preheating are employed to increase the surface roughness of the copper alloy substrate and reduce its reflectivity. This allows the copper alloy to melt together with GH3625 during the subsequent first-layer deposition process, followed by solidification to form a fusion zone and achieve a good metallurgical bond. Because Zr has a high growth limiting factor, preheating also enriches Zr at the interface, producing a compositional supercooling effect, increasing the nucleation rate, promoting grain refinement, producing a fine-grain strengthening effect, and enhancing the strength of the interface bond. Since the strength of the metallurgical bond between dissimilar materials depends on the thickness and uniformity of the element diffusion zone, and Marangoni convection influenced by the temperature gradient is the main driving force for element migration and homogenization within the molten pool, and laser energy affects both the temperature gradient and the molten pool depth, thus affecting Marangoni convection, sufficient laser energy is crucial in the laser cladding of GH3625 onto the Cu-Cr-Zr surface.

[0064] Without adding an intermediate layer, Cu-Cr-Zr and GH3625 dissimilar metals can be metallurgically bonded by substrate preheating and high-laser power cladding alone, forming a crack-free copper / nickel alloy dissimilar material. Figure 9 However, its high power results in a large heat input, which reduces the mechanical properties of the Cu-Cr-Zr substrate. Figure 4 , Figure 5 The structure formed along the deposition direction is Cu-Cr-Zr—fusion zone—GH3625. Appropriate process parameters are needed to form a metallurgical bond while avoiding excessive heat accumulation and hot cracking. Comparative Example 1 shows that the microstructure of the fusion zone is a lath + core-shell structure. The core-shell structure is due to the formation of a Cu-Cr eccentric alloy between liquid copper and liquid chromium, which undergoes liquid phase separation (LPS) during cooling. During solidification, liquid copper preferentially solidifies, resulting in a core-shell structure with copper on the inner side and chromium on the outer side. However, since the copper content in the molten pool comes only from the Cu-Cr-Zr substrate, the copper content is limited. During solidification, it can only undergo liquid phase separation with a portion of the chromium in GH3625 to form a core-shell structure, while the remaining chromium solidifies together with nickel, forming large columnar crystals of 111.5 μm. Figure 11 This ultimately resulted in an uneven lath + core-shell structure, which had a limited impact on performance.

[0065] By adding an intermediate layer, a compositional gradient was created between the Cu-Cr-Zr substrate and GH3625, mitigating stress concentration at the interface caused by differences in thermal expansion coefficients and thermal conductivity. Using a homogeneously mixed powder as the first-layer deposition material also increased the probability of contact and reaction between the two materials during deposition, promoting elemental homogeneity in the molten pool and reducing the dependence of element migration on Marangoni convection. This resulted in lower first-layer power and reduced heat input to the Cu-Cr-Zr substrate, thereby improving the performance of the copper / nickel alloy heterostructure; tensile properties improved by 10.6%, and shear properties improved by 21.4%. Figure 4 , Figure 5 The addition of the intermediate layer also increased the copper content in the molten pool, causing extensive liquid-phase separation during solidification and forming numerous core-shell structures. These core-shell structures, while hindering the further growth of primary columnar crystals, also served as low-energy nucleation sites, increasing the nucleation rate and refining the grain size to 72.8% of its original size, resulting in equiaxed crystals with a size of 30.3 μm. Figure 3 This also increased the hardness by 31.8%. Figure 6 , Figure 12 ).

[0066] In summary, microstructure: OM, SEM-EDS, and SEM-EBSD revealed that the fusion zone of the sample without the intermediate layer consisted of coarse columnar crystals of 111.5 μm in diameter. Figure 11 The substructure consists of alternating long lamellae rich in nickel and chromium and long lamellae rich in copper, with the copper-rich lamellae also containing a core-shell structure rich in nickel and chromium. Figure 10 The sample with the added intermediate layer consists of fine equiaxed crystals of 30.3 μm. Figure 3 The substructure consists of a nickel- and chromium-rich core-shell structure and a copper-rich mesh distributed around it. Figure 2 ).

[0067] Mechanical properties: The addition of the interlayer increases the uniformity of elements in the molten pool, reduces dependence on Marangoni convection, and lowers the heat input to the substrate. This improves the tensile and shear properties of the copper / nickel alloy from 311.9 MPa and 196.1 MPa (without the interlayer) to 344.5 MPa and 237.9 MPa (within the interlayer). Figure 4 , Figure 5 The addition of the intermediate layer also increased the copper content in the molten pool, promoted liquid-phase separation, and formed a uniform nickel-chromium core-shell structure, refining the grain size to 72.8% of the sample without the intermediate layer. Figure 3 , Figure 11 The resulting fine-grain strengthening effect also increased the hardness from 177.8 HV in the sample without an intermediate layer to 234.4 HV. Figure 6 , Figure 12 ).

Claims

1. A method for high-efficiency laser cladding of a copper alloy surface with a nickel-based superalloy, characterized in that, By preheating to increase the absorption of copper alloy to infrared laser, by the composition regulation of copper alloy / nickel alloy interlayer, laser cladding GH3625 alloy on the surface of Cu-Cr-Zr alloy, control the formation of microstructure in non-equilibrium solidification process, the specific steps are as follows: (1) the Cu-Cr-Zr substrate is polished with sandpaper and laser preheating pretreatment; First, the Cu-Cr-Zr substrate is polished with 60-400 mesh sandpaper to remove surface oxides, impurities and oil stains, then the sandpaper polished Cu-Cr-Zr substrate is preheated using laser scanning; (2) weigh the Cu-Cr-Zr powder and GH3625 powder, configure the interlayer powder according to a certain mass fraction percentage, with a ball to powder ratio of 1:2, place the configured powder in the ball mill mixer for a period of time, after ball milling, dry the powder and store it in vacuum; (3) the Cu-Cr-Zr substrate is polished with 60-80 mesh sandpaper to remove surface oxides, impurities and oil stains; (4) the Cu-Cr-Zr substrate is preheated using laser scanning after sandpaper polishing; (5) appropriate parameters are used for interlayer cladding; Place the ball-mixed interlayer powder and GH3625 powder in the powder feeding barrel, and transport the ball-mixed interlayer powder for the first layer deposition; (6) appropriate parameters are used for GH3625 cladding, and GH3625 powder is transported for subsequent deposition.

2. The method of claim 1, wherein the copper alloy surface is a nickel-based superalloy. The Cu-Cr-Zr substrate used in step (1) consists of the following components by mass percentage: Cr 1.00%, Zr 0.122%, the balance being copper and unavoidable impurities; the size of the Cu-Cr-Zr substrate is 100mm*100mm*15mm.

3. The method of claim 1, wherein the copper alloy surface is a nickel-based superalloy. The laser scanning in step (1) is inclined at an angle of 15°-30°, and the Cu-Cr-Zr substrate is preheated using laser scanning on the target area, the laser spot is 3mm, the working distance is 17-20mm, the laser power is 1000-2000W, the scanning speed is 5-10mm / s, the horizontal direction overlap is 50-80%, the offset is 0.9-2.3mm, after single layer scanning, repeat 1-3 times, a total of 2-4 times.

4. The method of claim 1, wherein the copper alloy surface is a nickel-based superalloy. The raw material mass percentage of the Cu-Cr-Zr powder used in step (2) consists of the following components: Cr 0.91%, Zr 0.17%, and the balance consisting of copper and inevitable impurities; the particle size distribution of the Cu-Cr-Zr powder consists of: 53 μm-150 μm, D10=50.48 μm, D50=83.38 μm, and D90=123.5 μm; the raw material mass percentage of the GH3625 powder used in step (2) consists of the following components: Cr 20.69%, Mo 8.47%, Nb 3.64%, Co 0.18%, Si 0.16%, Ti 0.065%, Cu 0.061%, Zr 0.03%, Al 0.024%, and the balance consisting of nickel and inevitable impurities; the particle size distribution of the GH3625 powder consists of: 53 μm-150 μm, D10=78.3 μm, D50=107.6 μm, and D90=146.7 μm; the mass percentage of the Cu-Cr-Zr powder and the GH3625 powder in step (2) is GH3625 60%-80% and Cu-Cr-Zr 20%-40%.

5. The method of claim 1, wherein the copper alloy surface is a nickel-based superalloy. The rotation speed of the ball mill mixer in step (2) is 200-230 r / min, and the mixing time is 60 min-180 min.

6. The method of claim 1, wherein the copper alloy surface is a nickel-based superalloy. The drying temperature of the intermediate layer powder after ball milling in step (2) is 60-80°C, and the drying time is 2-4 h.

7. The method of claim 1, wherein the copper alloy surface is a nickel-based superalloy. In the preheating treatment in step (4), the laser head is inclined by 15°-30°, the Cu-Cr-Zr substrate is preheated by using laser scanning on the target area, the laser spot is 3 mm, the working distance is 17-20 mm, the laser power is 1000-2000 W, the scanning speed is 5-10 mm / s, the horizontal direction overlap is 50-80% (offset 0.9-2.3 mm), and after the single-layer scanning is completed, it is repeated 1-3 times, a total of 2-4 times.

8. The method of claim 1, wherein the copper alloy surface is a nickel-based superalloy. In the first layer deposition in step (5), the laser spot is 3 mm, the working distance is 17-20 mm, the laser power is 2500-4000 W, the scanning speed is 5-10 mm / s, the horizontal direction overlap is 50-80%, the offset is 0.9-2.3 mm, the powder feeding rate is 0.4-1.0 r / min, 1-2 layers are cladded, and after the cladding is completed, the laser is turned off and cooled for 1-5 min.

9. The method of claim 1, wherein the copper alloy surface is a nickel-based superalloy. In the subsequent deposition in step (6), the laser spot is 3 mm, the working distance is 17-20 mm, the laser power is 600-1500 W, the scanning speed is 5-10 mm / s, the horizontal direction overlap is 50-80%, the offset is 0.9-2.3 mm, the powder feeding rate is 0.4-1.0 r / min, the laser is turned off after each layer is cladded, and cooled for 1-5 min, and then the cladding of the next layer is performed.

Images