CN114752934A

CN114752934A - Double-beam wire feeding type laser cladding method for copper surface

Info

Publication number: CN114752934A
Application number: CN202210380699.3A
Authority: CN
Inventors: 黄婷; 罗鹏; 肖荣诗
Original assignee: Beijing University of Technology
Current assignee: Beijing University of Technology
Priority date: 2022-04-12
Filing date: 2022-04-12
Publication date: 2022-07-15

Abstract

The invention provides a double-beam wire feeding type laser cladding method for a copper surface, which comprises the following steps: preparing an absorption layer on the surface of a copper matrix to promote the absorption of laser energy by the copper matrix; applying a first laser beam to a wire, inducing an evaporation front at the end of the wire, and absorbing laser energy in a deep melting mode to heat and melt the wire, wherein the wire is melted to form a metal drop, the metal drop is transited to the surface of the copper substrate to form a molten pool, and the molten pool is solidified to form a continuous cladding layer along with the movement of the first laser beam; and applying a second laser beam to the surface of the copper matrix, whereby the absorbing layer is capable of absorbing the energy of the second laser beam to locally preheat the copper matrix in a thermal conduction mode. The invention can obviously improve the deposition efficiency of the material and can effectively avoid the formation of defects such as poor fusion, poor wettability, cracks, air holes and the like.

Description

Double-beam wire feeding type laser cladding method for copper surface

Technical Field

The invention relates to a double-beam wire feeding type laser cladding method for a copper surface, and belongs to the technical field of advanced manufacturing.

Background

Copper is a material with excellent electric and thermal conductivity, and is widely applied to the important fields of electronic and electric appliances, mechanical manufacturing, metallurgy, national defense industry and the like. However, copper and its alloy have the problems of poor wear resistance, insufficient corrosion resistance and the like under certain severe working conditions. For example, a copper crystallizer needs to bear a high-temperature environment of more than 300 ℃ in the service process, elements such as S, F in molten steel easily generate electrochemical corrosion on the surface of copper, the copper crystallizer pushes out a cast ingot through vibration after the molten steel is gradually solidified to form the cast ingot, and the surface needs to bear certain abrasion in the process. Therefore, it is necessary to prepare suitable high-temperature wear-resistant and corrosion-resistant coatings on the surface of copper and its alloys to improve the service life thereof. At present, iron and steel enterprises mainly adopt an electroplating method to prepare a coating with the thickness of about 0.5-2.5 mm on the surface of a copper alloy, and a few adopt a thermal spraying method to prepare a super-high-temperature-resistant and wear-resistant coating on the surface of the copper alloy. The coatings prepared by the two methods are mainly mechanically combined with a matrix, cracks are easily generated under the action of thermal stress under the condition of thermal cycle, and the coatings are peeled off seriously, so that the continuous casting crystallizer is offline for overhaul in advance and even is directly scrapped, and the economic loss caused by the peeling can reach billions of yuan per year.

The laser cladding technology is an advanced surface coating preparation technology and has the following main advantages: (1) the coating and the matrix are completely metallurgically bonded, and the bonding strength is high; (2) the coating is compact, the tissue is fine, and the mechanical property is excellent; (3) the heat affected zone is small, the deformation of the workpiece is small, and the processing precision is high; (4) the noise is small, the pollution is low, and the working environment is comfortable; (5) the processing flexibility is good, and the automation is easy to realize.

The laser cladding technology can be divided into preset laser cladding and synchronous laser cladding according to the feeding mode of materials. The preset laser cladding generally refers to powder preset laser cladding, and the synchronous laser cladding can be divided into synchronous powder feeding laser cladding and synchronous wire feeding laser cladding according to the type of cladding materials.

Powder pre-arranged laser cladding is generally performed by uniformly mixing powder and an organic binder, then uniformly coating the mixture on the surface of a substrate in a certain thickness, and then heating to cure the organic binder so that a powder pre-arranged layer can be firmly combined with the substrate. In addition, the pre-deposited layer may also be dried by heating and the substrate may be preheated to some extent. After the powder is preset, laser is acted on the surface of the base body coated with the preset layer, and the preset layer is melted and solidified along with laser scanning to form a surface coating which is in metallurgical bonding with the base body. However, this method has certain limitations: (1) the process is more, the process cycle is long, and the time cost is high; (2) the organic binder is decomposed under the action of laser to form gas, and if the gas cannot escape from the molten pool in time, pores are formed. Therefore, in order to facilitate the escape of air holes, the thickness of the preset layer is controlled to be about 0.5mm, which is not beneficial to the one-time preparation of thick coatings; (3) the coating surface is usually very rough and has low machining precision.

The synchronous laser cladding method has the following problems that the molten pool is formed by applying laser to the surface of a substrate, powder is continuously injected into the molten pool, and is melted in the molten pool and forms a cladding layer along with the solidification of the molten pool, and the method is adopted to carry out the coating preparation on the copper surface: (1) the laser absorption rate of copper is insufficient, and the energy utilization rate is low; (2) powder can not completely enter a molten pool, and the material utilization rate is low; (3) the powder is difficult to recover, and environmental pollution is easy to cause; (4) the powder material is expensive.

Wire-feeding laser cladding is a laser cladding method with high material utilization rate (close to 100%) and low processing cost, but the traditional wire-feeding laser cladding process directly acts on the surface of a substrate to form a liquid molten pool, and a cold wire/hot wire is continuously fed into the molten pool, so that the wire is melted and solidified to form a continuous cladding layer. Copper is used as a high-reflection and high-heat-conduction material, a high-power laser applied to the industry at present almost works in an infrared band (about 970-1070 nm), the absorption rate of copper to laser in the infrared band is less than 5%, and laser directly acts on the surface of a substrate to hardly form a continuous and stable molten pool, so that a continuous and stable laser cladding layer is difficult to prepare. Although copper has higher energy absorption rate to green light of 515nm wave band and blue light of 450nm wave band, the current commercialized products of high-power blue light and green light laser are not mature, large-scale industrial application is difficult to realize, and the electro-optical conversion efficiency is low, so that the equipment cost and the energy consumption cost are both higher.

In order to solve a series of problems caused by high thermal conductivity of copper, a method of preheating a substrate is generally adopted to reduce the heat dissipation rate in the laser cladding process. However, the energy consumption for the overall preheating of the copper base material is high, and a special large heating furnace is required for a large member, so that the overall preheating method is not economical. The deposition efficiency is greatly improved compared with the common synchronous powder feeding laser cladding process by locally preheating the copper Surface by adopting a synchronous high-frequency induction heating method and preparing a silicide coating on the copper Surface by adopting a synchronous powder feeding method (1 Yin J, Wang D Z, Meng L, et al. high-temperature slide side of Ni-Cr-Si metal substrate composite coating on copper substrate side laser-index hybrid coating J. Surface & Coatings Technology,2017,325: 120-126.). However, the laser-induction hybrid cladding method based on high-frequency induction heating to preheat the substrate still has the problems of low processing flexibility, poor process adaptability and the like. In conclusion, it is difficult to efficiently prepare defect-free large-area coatings on copper surfaces by any laser cladding process, and the most prominent problems are high energy consumption, low deposition efficiency, low material utilization rate and high processing cost.

Aiming at the problems of high energy consumption, low deposition efficiency, low material utilization rate, high processing cost, low processing flexibility and the like in the preparation of the laser cladding coating on the surface of the copper at present, the inventor previously invented a wire-feeding type additive manufacturing method (CN202011281588.4) based on double-beam synchronous preheating, wherein the relative position arrangement modes of a wire and a laser beam are three: (1) two beams of laser are arranged on two sides of the normal line of the substrate, and the wire is arranged between the two beams of laser and forms a certain angle with the two beams of laser; (2) two beams of laser are arranged in front of the wire material, and the three beams of laser form a certain angle with each other; (3) two bundles of laser are arranged behind the wire, and the three mutually form a certain angle, which is equivalent to only adjusting the incident angle and the acting position of the laser beam 3 compared with the scheme (1). No matter what kind of laser beam and wire material relative position is arranged, synchronous preheating can be realized in the laser cladding process, the temperature field can be quantitatively regulated and controlled by adjusting the spot size, power and action position of the laser beam, and an excellent solution is provided for efficiently preparing large-area defect-free coatings on various base materials. However, the invention does not fully take into account the problem of insufficient absorption (< 5%) of the "high-reflective" matrix material for the laser light in the infrared band. When the surface of a high-reflectivity material such as copper and copper alloy is subjected to laser cladding, if laser is adopted to act on the surface of a matrix for preheating, the problem that the reflectivity of the copper and copper alloy to infrared band laser is too high needs to be considered. On one hand, the high reflection causes the problems of insufficient laser absorption rate, low energy utilization rate and the like of a matrix, so that the cladding process is unstable and the cladding layer has poor quality; on the other hand, "high-reverse" may bring potential safety hazards to equipment and working environment.

Disclosure of Invention

The invention aims to provide a laser cladding process for efficiently preparing a large-area coating on the surface of high-reflection and high-thermal-conductivity copper and alloy materials thereof.

The technical scheme of the invention is as follows.

A double-beam wire feeding type laser cladding method for a copper surface comprises the following steps:

preparing an absorption layer on the surface of a copper matrix to promote the absorption of laser energy by the copper matrix;

the method comprises the steps that a first laser beam acts on a wire, an evaporation front is induced to generate at the end of the wire, laser energy is absorbed in a deep melting mode to heat and melt the wire, the wire is melted to form metal drops, the metal drops are transited to the surface of a copper matrix to form a molten pool, and the molten pool is solidified along with the movement of the first laser beam to form a continuous cladding layer;

and applying a second laser beam to the surface of the copper matrix, whereby the absorbing layer is capable of absorbing the energy of the second laser beam to locally preheat the copper matrix in a thermal conduction mode.

Preferably, the thickness of the absorption layer is 50-200 μm.

Preferably, the material of the absorption layer has a higher absorption rate for infrared band laser light than the copper matrix.

Preferably, the material of the absorption layer is a metal powder that is metallurgically compatible with the copper matrix and the wire.

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

Preferably, the wire is a Ni-based superalloy wire.

Preferably, the included angle between the wire and the normal direction of the copper substrate is-45 degrees to +45 degrees.

Preferably, the angle between the first laser beam and the normal direction of the copper substrate is 15-45 °.

Preferably, the first laser beam is applied to the wire at a position 1-3 mm away from the surface of the copper substrate.

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

Through the technical scheme, the invention can obtain the following beneficial effects.

The invention adopts a beam of laser to heat and melt the wire material in a deep melting mode, thereby greatly improving the melting efficiency of the wire material and obviously improving the deposition efficiency of the material.

Meanwhile, the other beam of laser is adopted to preheat the workpiece, so that the cladding temperature field and the morphology of the cladding layer are conveniently regulated and controlled, and the defects of poor fusion, poor wettability, cracks, air holes and the like are effectively avoided.

Drawings

Fig. 1 is a schematic diagram of a first two-beam-based copper surface efficient laser cladding scheme.

Fig. 2 is a schematic diagram of a second two-beam-based copper surface efficient laser cladding scheme.

Fig. 3 is a schematic diagram of a third two-beam-based copper surface high-efficiency laser cladding scheme.

The meaning of the labels in the figures: 1. the laser processing method comprises the following steps of (1) wire, 2. first laser beam, 3. second laser beam, 4. evaporation front, 5. molten pool, 6. cladding layer, 7. substrate and 8. absorption layer.

Detailed Description

The present invention is described in further detail below with reference to specific embodiments.

Example 1

As shown in FIG. 1, a first laser beam 2 and a second laser beam 3 are arranged at an angle on both sides of a wire 1. The second laser beam 3 acts on the surface of the substrate 7, the primary laser absorption rate of the substrate is improved through the preset absorption layer, and the preset layer preheats the copper or the copper alloy substrate in a thermal conduction mode after absorbing laser energy. The first laser beam 2 acts on the wire 1 to form a deep-melt keyhole and a corresponding evaporation front 4, whereby the wire 1 absorbs the energy of the laser beam 2 in a deep-melt mode and transitions to a molten pool 5 and a cladding layer 6 on a substrate 7.

The substrate 7 is a copper substrate, i.e. the surface of a workpiece subjected to laser cladding, and the material can be pure copper or an alloy thereof.

The wire 1 can be made of a material which is suitable for 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 can be dissolved in each other infinitely, and the thermal expansion coefficients of Ni and Cu are close, so that good metallurgical bonding can be formed between the cladding layer and the substrate.

The absorption layer 8 is made of a material which is compatible with the matrix 7 and the cladding material, and can be pure Ni powder, Ni-based alloy powder or mixed powder consisting of multiple pure metal powders, and the metallurgical compatibility of the absorption layer with the matrix and the wire material needs to be ensured. The absorption layer may be used as a cladding layer filler material, partially or not, after laser cladding. In a preferred embodiment, the thickness of the predetermined absorption layer is 50 to 200 μm.

The first laser beam 2 and the second laser beam 3 may be generated by any suitable laser and focused at set positions by an optical focusing system. The first laser beam 2 and the second laser beam 3 may be the same wavelength laser or different wavelength lasers.

In this embodiment, the wire 1 is arranged in a front-end feeding manner, i.e., the wire 1 is arranged forward of the substrate normal line along the system scanning direction, and the angle between the wire 1 and the normal line of the substrate 7 is defined to be positive.

In a preferred embodiment, the included angle between the wire 1 and the normal of the matrix is 0-30 degrees; the included angle between the laser beam 2 and the wire material 1 is 15-60 degrees. The distance between the spot position of the first laser beam 2 acting on the wire material and the surface of the substrate 7 is 1-3 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 light spot and the center of the wire material 1 on the substrate 7 is 0-5 mm.

The thermal conduction mode is that laser preheats the surface of the substrate locally with lower power density, only the absorption layer is melted after the surface of the substrate absorbs the laser energy, and the copper substrate is only heated in a solid state.

The 'deep melting mode' refers to that laser heats a wire material at a higher power density, and the wire material absorbs laser energy and then is deeply melted and evaporated, so that a deep melting small hole and a corresponding evaporation front are formed in the wire material.

Example 2

As shown in FIG. 2, a first laser beam 2 and a second laser beam 3 are arranged at an angle in front of a wire 1. The second laser beam 3 is applied to the surface of the substrate 7 to preheat the workpiece in a thermally conductive 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 laser beam 2 in a deep melting mode and transitions to a molten pool 5 and a cladding layer 6 on a substrate 7.

The wire 1 can be made of a material which is suitable for the material of the substrate 1, and generally a Ni-based high-temperature alloy welding wire with good high-temperature wear resistance and corrosion resistance is selected, wherein Ni and Cu can be infinitely mutually dissolved, and the thermal expansion coefficients of Ni and Cu are close, so that good metallurgical bonding can be formed between the cladding layer and the substrate.

The absorbing layer 8 is made of a material which is compatible with the matrix and the cladding material, and can be pure Ni powder, Ni-based alloy powder or mixed powder consisting of a plurality of pure metal powders, and the metallurgical compatibility of the absorbing layer with the matrix and the wire material needs to be ensured. The absorbing layer may be used as, partially, or not as a cladding layer filler material after laser cladding. In a preferred embodiment, the thickness of the predetermined absorption layer is 50 to 200 μm.

In this embodiment, the welding wire 1 is arranged in a rear feeding manner, i.e. the wire 1 is arranged behind the substrate normal in the scanning direction of the system, where the angle between the wire 1 and the substrate normal is specified to be negative.

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

Example 3

As shown in FIG. 3, a first laser beam 2 and a second laser beam 3 are arranged at an angle behind a wire 1. The laser beam 3 is applied to the surface of the substrate 7 to preheat the workpiece in a thermally conductive mode. The laser beam 2 acts on the wire 1 to form a deep-melt keyhole and a corresponding evaporation front 4, whereby the wire 1 absorbs the energy of the laser beam 2 in a deep-melt mode and transitions to a molten pool 5 and a cladding layer 6 on a substrate 7.

The substrate 7 is a copper substrate, namely the surface of a workpiece subjected to laser cladding, and the material can be pure copper or an alloy thereof.

The

laser beams

2 and 3 can be generated by any suitable laser and focused at set positions by an optical focusing system. The first laser beam 2 and the second laser beam 3 may be the same wavelength laser or different wavelength lasers.

In this embodiment, the wire 1 is arranged in a front-end feeding manner, i.e., the wire 1 is arranged in front of the substrate normal line along the system scanning direction, where the angle between the wire 1 and the substrate normal line is specified to be positive.

Preferably, the included angle between the wire 1 and the normal of the substrate is 15-45 degrees; the included angle between the laser beam 2 and the wire material 1 is 30-90 degrees; the distance between the laser beam 2 and the base plate at the spot position acted on the welding wire is 1-3 mm; the laser beam 3 acts on the surface of the substrate at any proper angle, and the relative distance between the laser beam and the wire material on the substrate is 1-5 mm.

The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the present invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention.

Claims

1. A double-beam wire feeding type laser cladding method for a copper surface is characterized by comprising the following steps:

applying a first laser beam to a wire, inducing an evaporation front at the end of the wire, and absorbing laser energy in a deep melting mode to heat and melt the wire, wherein the wire is melted to form a metal drop, the metal drop is transited to the surface of the copper substrate to form a molten pool, and the molten pool is solidified to form a continuous cladding layer along with the movement of the first laser beam;

2. The method for double-beam wire feeding type laser cladding of the copper surface according to claim 1, wherein the thickness of the absorption layer is 50-200 μm.

3. The method for double-beam wire feeding type laser cladding of the copper surface according to claim 1, wherein the material of the absorption layer has higher absorptivity to infrared band laser than the copper substrate.

4. The method for double-beam wire feeding type laser cladding of the copper surface according to claim 3, wherein the material of the absorption layer is metal powder which has metallurgical compatibility with the copper substrate and the wire.

5. The method for double-beam wire feeding type laser cladding of the copper surface according to claim 4, wherein the material of the absorption layer is pure Ni powder, Ni-based alloy powder or mixed powder consisting of a plurality of pure metal powders.

6. The method for double-beam wire feeding type laser cladding of the copper surface as claimed in claim 4, wherein the wire is a Ni-based high temperature alloy welding wire.

7. The method for double-beam wire feeding type laser cladding of the copper surface according to claim 1, wherein the included angle between the wire and the normal direction of the copper substrate is-45 degrees to +45 degrees.

8. The method for double-beam wire feeding type laser cladding of the copper surface according to claim 1, wherein an included angle between the first laser beam and a normal direction of the copper substrate is 15-45 °.

9. The method for double-beam wire feeding type laser cladding of the copper surface according to claim 1, wherein the first laser beam is applied to the wire at a position 1-3 mm away from the surface of the copper substrate.

10. The method for double-beam wire feeding type laser cladding of the copper surface according to claim 1, wherein the distance between the center of a light spot of the second laser beam acting on the surface of the copper substrate and the center of the wire is 0-5 mm.