A double-beam wire-feeding laser cladding method for copper surface

Abstract

The present invention provides a copper surface dual-beam wire-feeding laser cladding method, comprising the following steps: preparing an absorption layer on the surface of a copper substrate to promote the copper substrate to absorb laser energy; applying a first laser beam to a wire material, inducing an evaporation front at the end of the wire material, and absorbing laser energy in a deep melting mode to heat and melt the wire material, wherein the wire material melts to form metal droplets that transition to the surface of the copper substrate to form a molten pool, and as the first laser beam moves, the molten pool solidifies to form a continuous cladding layer; applying a second laser beam to the surface of the copper substrate, whereby the absorption layer can absorb the energy of the second laser beam, and locally preheat the copper substrate in a thermal conductivity mode. The present invention can significantly improve the deposition efficiency of the material, and can also effectively avoid the formation of defects such as poor fusion, poor wettability, cracks, and pores.

Description

Technical Field

[0001] The invention relates to a copper surface double-beam wire-feeding laser cladding method, belonging to the field of advanced manufacturing technology. Background Art

[0002] Copper is a material with excellent electrical and thermal conductivity, and is widely used in important fields such as electronics, machinery manufacturing, metallurgy, and defense industry. However, copper and its alloys have poor wear resistance and insufficient corrosion resistance under certain harsh working conditions. For example, copper crystallizers need to withstand high temperatures exceeding 300°C during service. At the same time, elements such as S and F in molten steel are prone to electrochemical corrosion on the copper surface. After the molten steel gradually solidifies to form an ingot, the copper crystallizer pushes the ingot out by vibration. During this process, the surface needs to withstand certain wear. Therefore, it is necessary to prepare a suitable high-temperature wear-resistant and corrosion-resistant coating on the surface of copper and its alloys to improve their service life. At present, steel companies mainly use electroplating to prepare a coating with a thickness of about 0.5 to 2.5 mm on the surface of copper alloys, and a few use thermal spraying to prepare ultra-high temperature resistant and wear-resistant coatings on their surfaces. The coatings prepared by both methods are mainly mechanically bonded to the substrate, and are prone to cracks under thermal stress under thermal cycle conditions. In severe cases, the coating will peel off, causing the continuous casting crystallizer to be offline for maintenance or even directly scrapped in advance, resulting in economic losses of up to tens of billions of yuan per year.

[0003] Laser cladding technology is an advanced surface coating preparation technology with the following main advantages: (1) The coating and the substrate are completely metallurgically bonded and have high bonding strength; (2) The coating is dense, has fine structure, and has excellent mechanical properties; (3) The heat-affected zone is small, the workpiece deformation is small, and the processing accuracy is high; (4) The noise is low, the pollution is low, and the working environment is comfortable; (5) The processing is flexible and easy to automate.

[0004] Laser cladding technology can be divided into preset laser cladding and synchronous laser cladding according to the material feeding method. Preset laser cladding generally refers to powder preset laser cladding, and synchronous laser cladding can be divided into synchronous powder feeding laser cladding and synchronous wire feeding laser cladding according to the type of cladding material.

[0005] Powder pre-coating laser cladding is generally carried out by mixing powder and organic binder evenly and then brushing them evenly on the surface of the substrate with a certain thickness, and then curing the organic binder by heating so that the powder pre-coating layer can be firmly bonded to the substrate. In addition, the pre-coating layer can be dried by heating and the substrate can be preheated to a certain extent. After the powder pre-coating is completed, the laser is applied to the surface of the substrate coated with the pre-coating layer. As the laser scans, the pre-coating layer melts and solidifies to form a surface coating that is metallurgically bonded to the substrate. However, this method has certain limitations: (1) There are many steps, a long process cycle, and high time cost; (2) The organic binder decomposes under the action of the laser to form gas. If the gas cannot escape from the molten pool in time, pores will be formed. Therefore, in order to facilitate the escape of pores, the thickness of the pre-coating layer is controlled at about 0.5 mm, which is not conducive to the one-time preparation of thick coatings; (3) The coating surface is usually very rough and the processing accuracy is low.

[0006] Synchronous laser cladding forms a molten pool by applying laser to the surface of the substrate. Powder is continuously injected into the molten pool, melted in the molten pool and solidified to form a cladding layer. However, this method also has the following problems when preparing coatings on copper surfaces: (1) Copper has insufficient laser absorption rate and low energy utilization rate; (2) Powder cannot completely enter the molten pool and material utilization rate is low; (3) Powder recovery is difficult and easily causes environmental pollution; (4) Powder materials are expensive.

[0007] Wire feeding laser cladding is a laser cladding method with high material utilization rate (close to 100%) and low processing cost. However, the traditional wire feeding laser cladding process directly acts on the substrate surface to form a liquid molten pool. By continuously feeding the cold wire / hot wire into the molten pool, the wire material melts and solidifies to form a continuous cladding layer. As a highly reflective and highly thermally conductive material, copper is currently used in industrial applications. Almost all high-power lasers work in the infrared band (about 970-1070nm). The absorption rate of copper to infrared lasers is less than 5%. It is difficult to form a continuous and stable molten pool by directly applying the laser to the substrate surface. Therefore, it is difficult to prepare a continuous and stable laser cladding layer. Although copper has a high energy absorption rate for green light in the 515nm band and blue light in the 450nm band, the commercial products of high-power blue and green lasers are not yet mature, making it difficult to achieve large-scale industrial applications, and the electro-optical conversion efficiency is low, so both the equipment cost and energy consumption cost are high.

[0008] In order to improve a series of problems caused by the high thermal conductivity of copper itself, the method of preheating the substrate is generally used to reduce the heat dissipation rate during laser cladding. However, the overall preheating of the copper substrate material consumes a lot of energy, and a special large heating furnace is required for large components. Therefore, the overall preheating method is not economical. At present, some scholars have used the method of synchronous high-frequency induction heating to locally preheat the copper surface, and used the synchronous powder feeding method to prepare a silicide coating on the copper surface. Compared with the general synchronous powder feeding laser cladding process, the deposition efficiency is greatly improved ([1] Yin J, Wang DZ, Meng L, et al. High-temperature slide wear of Ni-Cr-Si metal silicide based composite coatings on copper substrate by laser-induction hybrid cladding [J]. Surface & Coatings Technology, 2017, 325: 120-126.). However, the laser-induction composite cladding method based on high-frequency induction heating to preheat the substrate still has problems such as low processing flexibility and poor process adaptability. In summary, it is very difficult to efficiently prepare large-area defect-free coatings on copper surfaces using any current laser cladding process. The most prominent problems are high energy consumption, low deposition efficiency, low material utilization, and high processing costs.

[0009] In view of the problems of high energy consumption, low deposition efficiency, low material utilization, high processing cost and low processing flexibility in the preparation of laser cladding coating on copper surface, the inventors have previously invented a wire feeding additive manufacturing method based on dual beam synchronous preheating (CN202011281588.4), wherein there are three relative position arrangements of the wire and the laser beam: (1) two laser beams are arranged on both sides of the normal line of the substrate, the wire is arranged between the two laser beams and forms a certain angle with the two laser beams; (2) two laser beams are arranged in front of the wire, and the three are at a certain angle to each other; (3) two laser beams are arranged behind the wire, and the three are at a certain angle to each other, which is equivalent to only adjusting the incident angle and action position of laser beam 3 compared with scheme (1). Regardless of the relative position arrangement of the laser beam and the wire, synchronous preheating can be achieved during the laser cladding process, and the temperature field can be quantitatively controlled by adjusting the spot size, power and action position of the laser beam, which provides an excellent solution for the efficient preparation of large-area defect-free coatings on various substrate materials. However, the invention does not fully consider the problem of insufficient absorption rate of infrared laser by "high-reflective" substrate materials (less than 5%). When laser cladding is performed on the surface of high-reflective materials such as copper and its alloys, if laser is used to act on the substrate surface for preheating, special consideration should be given to the problem of excessive reflectivity of copper and its alloys to infrared lasers. On the one hand, "high reflection" brings about problems such as insufficient absorption rate of laser by the substrate and low energy utilization, which results in unstable cladding process and poor quality of cladding layer; on the other hand, "high reflection" may bring safety hazards to equipment and working environment. Summary of the invention

[0010] The object of the present invention is to provide a laser cladding process for efficiently preparing a large-area coating on the surface of high-reflection, high-thermal-conductivity copper and its alloy materials.

[0011] The technical solution of the present invention is as follows.

[0012] A copper surface double-beam wire feeding laser cladding method comprises the following steps:

[0013] Preparing an absorption layer on the surface of the copper substrate to promote the copper substrate to absorb laser energy;

[0014] Applying a first laser beam to a wire material, inducing an evaporation front at an end of the wire material, and absorbing laser energy to heat and melt the wire material in a deep melting mode, wherein the wire material is melted to form metal droplets that transition to the surface of the copper substrate to form a molten pool, and as the first laser beam moves, the molten pool solidifies to form a continuous cladding layer;

[0015] The second laser beam is applied to the surface of the copper substrate, so that the absorption layer can absorb the energy of the second laser beam and locally preheat the copper substrate in a thermal conduction mode.

[0016] Preferably, the absorption layer has a thickness of 50-200 μm.

[0017] Preferably, the material of the absorption layer has a higher absorption rate to infrared laser than the copper substrate.

[0018] Preferably, the material of the absorption layer is metal powder having metallurgical compatibility with the copper matrix and the wire material.

[0019] Preferably, the material of the absorption layer is pure Ni powder, Ni-based alloy powder or a mixed powder composed of multiple pure metal powders.

[0020] Preferably, the wire material is Ni-based high-temperature alloy welding wire.

[0021] Preferably, the angle between the wire and the normal direction of the copper substrate is -45° to +45°.

[0022] Preferably, the angle between the first laser beam and the normal direction of the copper substrate is 15° to 45°.

[0023] Preferably, the height of the position where the first laser beam acts on the wire is 1 to 3 mm from the surface of the copper substrate.

[0024] Preferably, the distance between the center of the spot of the second laser beam acting on the surface of the copper substrate and the center of the wire is 0-5 mm.

[0025] Through the above technical scheme, the present invention can achieve the following beneficial effects.

[0026] The present invention uses a laser beam to heat and melt the wire in a deep melting mode, thereby greatly improving the melting efficiency of the wire and significantly improving the deposition efficiency of the material.

[0027] At the same time, the present invention uses another laser beam to preheat the workpiece, which is convenient for regulating the cladding temperature field and the morphology of the cladding layer, thereby effectively avoiding the formation of defects such as poor fusion, poor wettability, cracks, and pores. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a schematic diagram of the first dual-beam based efficient laser cladding solution for copper surfaces.

[0029] Figure 2 This is a schematic diagram of the second dual-beam based efficient laser cladding solution for copper surfaces.

[0030] Figure 3 This is a schematic diagram of the third dual-beam based efficient laser cladding solution for copper surfaces.

[0031] The meanings of the marks in the figure are: 1. Wire, 2. First laser beam, 3. Second laser beam, 4. Evaporation front, 5. Molten pool, 6. Cladding layer, 7. Substrate, 8. Absorption layer. DETAILED DESCRIPTION

[0032] The present invention is further described in detail below in conjunction with specific technical solutions.

[0033] Example 1

[0034] like Figure 1 As shown, the first laser beam 2 and the second laser beam 3 are arranged at a certain angle on both sides of the wire 1. The second laser beam 3 acts on the surface of the substrate 7, and the substrate's absorption rate of the laser is increased by the pre-set absorption layer. After the pre-set layer absorbs the laser energy, it preheats the copper or its alloy substrate in a thermal conductivity mode. The first laser beam 2 acts on the wire 1 to form a deep melting hole and a corresponding evaporation front 4, so that the wire 1 absorbs the energy of the first laser beam 2 in a deep melting mode and transitions to the substrate 7 to form a molten pool 5 and a cladding layer 6.

[0035] The substrate 7 is a copper substrate, that is, the surface of the workpiece to be laser clad, and the material may be pure copper or its alloy.

[0036] The wire 1 can be made of a material compatible with the material of the substrate 7. Generally, a Ni-based high-temperature alloy welding wire with good high-temperature wear resistance and corrosion resistance is selected. Ni and Cu are infinitely miscible, and Ni and Cu have similar thermal expansion coefficients, which is conducive to forming a good metallurgical bond between the cladding layer and the substrate.

[0037] The absorption layer 8 is made of a material that is compatible with the substrate 7 and the cladding material, and can be pure Ni powder, Ni-based alloy powder, or a mixed powder composed of multiple pure metal powders. It is necessary to ensure its metallurgical compatibility with the substrate and the wire. After laser cladding, the absorption layer can be used completely, partially, or not as a cladding layer filling material. In a preferred embodiment, the preset absorption layer thickness is 50 to 200 μm.

[0038] The first laser beam 2 and the second laser beam 3 can be generated by any suitable laser and focused at a set position by an optical focusing system. The first laser beam 2 and the second laser beam 3 can be lasers of the same wavelength or lasers of different wavelengths.

[0039] In this embodiment, the wire 1 is arranged in a front wire feeding manner, that is, the wire 1 is arranged in front of the normal line of the substrate along the system scanning direction, and the angle between the wire 1 and the normal line of the substrate 7 is set to a positive value.

[0040] In a preferred embodiment, the angle between the wire 1 and the normal line of the substrate is 0° to 30°; the angle between the first laser beam 2 and the wire 1 is 15° to 60°. The distance between the spot position of the first laser beam 2 acting on the wire and the surface of the substrate 7 is 1 to 3 mm; the second laser beam 3 acts on the surface of the substrate 7 at any appropriate angle, and the relative distance between the center of the spot and the center of the wire 1 on the substrate 7 is 0 to 5 mm.

[0041] The "thermal conduction mode" described here means that the laser preheats the substrate surface locally at a relatively low power density, and after the substrate surface absorbs the laser energy, only the absorption layer is melted, and the copper substrate only undergoes solid-state heating.

[0042] The "deep melting mode" described here means that the laser heats the wire at a high power density, and the wire absorbs the laser energy and melts deeply and evaporates, thereby forming a deep melting hole and a corresponding evaporation front on the wire.

[0043] Example 2

[0044] like Figure 2 As shown, the first laser beam 2 and the second laser beam 3 are arranged in front of the wire 1 at a certain angle. The second laser beam 3 acts on the surface of the substrate 7 to preheat the workpiece in a thermal conduction mode. The first laser beam 2 acts on the wire 1 to form an evaporation front 4, whereby the wire 1 absorbs the energy of the first laser beam 2 in a deep melting mode and transitions to the substrate 7 to form a molten pool 5 and a cladding layer 6.

[0045] The substrate 7 is a copper substrate, that is, the surface of the workpiece to be laser clad, and the material may be pure copper or its alloy.

[0046] The wire 1 can be made of a material compatible with the material of the substrate 7. Generally, a Ni-based high-temperature alloy welding wire with good high-temperature wear resistance and corrosion resistance is selected. Ni and Cu are infinitely miscible, and Ni and Cu have similar thermal expansion coefficients, which is conducive to forming a good metallurgical bond between the cladding layer and the substrate.

[0047] The absorption layer 8 is made of a material that is compatible with both the substrate and the cladding material, and can be pure Ni powder, Ni-based alloy powder, or a mixed powder composed of multiple pure metal powders. It is necessary to ensure its metallurgical compatibility with the substrate and the wire material. The absorption layer can be used completely, partially, or not as a cladding layer filling material after laser cladding. In a preferred embodiment, the preset absorption layer thickness is 50 to 200 μm.

[0048] The first laser beam 2 and the second laser beam 3 can be generated by any suitable laser and focused at a set position by an optical focusing system. The first laser beam 2 and the second laser beam 3 can be lasers of the same wavelength or lasers of different wavelengths.

[0049] In this embodiment, the wire 1 is arranged in a post-wire feeding manner, that is, the wire 1 is arranged behind the normal line of the substrate along the system scanning direction, and the angle between the wire 1 and the normal line of the substrate is set to a negative value.

[0050] In a preferred embodiment, the angle between the wire 1 and the normal of the substrate 7 is -15° to -45°; the angle between the first laser beam 2 and the wire 1 is 15° to 60°. The distance between the spot position of the first laser beam 2 acting on the wire 1 and the surface of the substrate 7 is 1 to 3 mm; the second laser beam 3 acts on the surface of the substrate 7 at any appropriate angle, and the relative distance between the second laser beam 3 and the wire on the substrate 7 is 0 to 5 mm.

[0051] The "thermal conduction mode" described here means that the laser preheats the substrate surface locally at a relatively low power density, and after the substrate surface absorbs the laser energy, only the absorption layer is melted, and the copper substrate only undergoes solid-state heating.

[0052] The "deep melting mode" described here means that the laser heats the wire at a high power density, and the wire absorbs the laser energy and melts deeply and evaporates, thereby forming a deep melting hole and a corresponding evaporation front on the wire.

[0053] Example 3

[0054] like Figure 3 As shown, the first laser beam 2 and the second laser beam 3 are arranged at a certain angle behind the wire 1. The second laser beam 3 acts on the surface of the substrate 7 to preheat the workpiece in a thermal conduction mode. The first laser beam 2 acts on the wire 1 to form a deep melting hole and a corresponding evaporation front 4, whereby the wire 1 absorbs the energy of the first laser beam 2 in a deep melting mode and transitions to the substrate 7 to form a molten pool 5 and a cladding layer 6.

[0055] The substrate 7 is a copper substrate, that is, the surface of the workpiece to be laser clad, and the material may be pure copper or its alloy.

[0056] The wire 1 can be made of a material compatible with the material of the substrate 7. Generally, a Ni-based high-temperature alloy welding wire with good high-temperature wear resistance and corrosion resistance is selected. Ni and Cu are infinitely miscible, and Ni and Cu have similar thermal expansion coefficients, which is conducive to forming a good metallurgical bond between the cladding layer and the substrate.

[0057] The absorption layer 8 is made of a material that is compatible with both the substrate and the cladding material, and can be pure Ni powder, Ni-based alloy powder, or a mixed powder composed of multiple pure metal powders. It is necessary to ensure its metallurgical compatibility with the substrate and the wire material. The absorption layer can be used completely, partially, or not as a cladding layer filling material after laser cladding. In a preferred embodiment, the preset absorption layer thickness is 50 to 200 μm.

[0058] The first laser beam 2 and the second laser beam 3 can be generated by any suitable laser and focused at a set position by an optical focusing system. The first laser beam 2 and the second laser beam 3 can be lasers of the same wavelength or lasers of different wavelengths.

[0059] In this embodiment, the wire 1 is arranged in a front wire feeding manner, that is, the wire 1 is arranged in front of the normal line of the substrate along the scanning direction of the system, and the angle between the wire 1 and the normal line of the substrate is set to a positive value.

[0060] Preferably, the angle between the wire 1 and the normal of the substrate is 15° to 45°; the angle between the first laser beam 2 and the wire 1 is 30° to 90°; the spot position of the first laser beam 2 acting on the wire 1 is 1 to 3 mm away from the substrate; the second laser beam 3 acts on the surface of the substrate at any suitable angle, and its relative distance from the wire on the substrate is 1 to 5 mm.

[0061] The "thermal conduction mode" described here means that the laser preheats the substrate surface locally at a relatively low power density, and after the substrate surface absorbs the laser energy, only the absorption layer is melted, and the copper substrate only undergoes solid-state heating.

[0062] The "deep melting mode" described here means that the laser heats the wire at a high power density, and the wire absorbs the laser energy and melts deeply and evaporates, thereby forming a deep melting hole and a corresponding evaporation front on the wire.

[0063] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A copper surface double-beam wire feeding laser cladding method, characterized in that: The steps include: Preparing a pre-deposited absorption layer on the surface of the copper substrate to promote the copper substrate to absorb laser energy; Applying a first laser beam to a wire material, inducing an evaporation front at an end of the wire material, and absorbing laser energy to heat and melt the wire material in a deep melting mode, wherein the wire material is melted to form metal droplets that transition to the surface of the copper substrate to form a molten pool, and as the first laser beam moves, the molten pool solidifies to form a continuous cladding layer; Applying a second laser beam to the surface of the copper substrate, so that the pre-set absorption layer can absorb the energy of the second laser beam, locally preheating the copper substrate in a thermal conductivity mode, and regulating the cladding temperature field and the cladding layer morphology; after the copper substrate surface absorbs the laser energy, only the pre-set absorption layer is melted, and the copper substrate only undergoes solid-state heating; The thickness of the pre-deposited absorption layer is 50 to 200 μm; The material of the pre-set absorption layer has a higher absorption rate to infrared band laser than the copper substrate; The pre-set absorption layer is completely, partially or not used as a filling material of the cladding layer after laser cladding; The material of the pre-set absorption layer is a metal powder having metallurgical compatibility with the copper matrix and the wire material; The material of the pre-deposited absorption layer is pure Ni powder, Ni-based alloy powder or a mixed powder composed of multiple pure metal powders; The wire material is Ni-based high-temperature alloy welding wire.

2. A copper surface dual-beam wire feeding laser cladding method according to claim 1, characterized in that: The angle between the wire and the normal direction of the copper substrate is -45° to +45°.

3. A copper surface dual-beam wire feeding laser cladding method according to claim 1, characterized in that: The angle between the first laser beam and the normal direction of the copper substrate is 15° to 45°.

4. A copper surface dual-beam wire feeding laser cladding method according to claim 1, characterized in that: The position where the first laser beam acts on the wire is 1 to 3 mm from the surface of the copper substrate.

5. A copper surface dual-beam wire feeding laser cladding method according to claim 1, characterized in that: The distance between the center of the spot of the second laser beam acting on the surface of the copper substrate and the center of the wire is 0 to 5 mm.

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