CN110344056B

CN110344056B - Process for preparing cladding layer on surface of copper matrix by high-speed laser cladding technology

Info

Publication number: CN110344056B
Application number: CN201910762858.4A
Authority: CN
Inventors: 王菊花; 李建平
Original assignee: Tangshan Zhongke Quantum Laser Technology Co Ltd
Current assignee: Tangshan Zhongke quantum laser technology Co., Ltd
Priority date: 2019-08-19
Filing date: 2019-08-19
Publication date: 2021-11-02
Anticipated expiration: 2039-08-19
Also published as: CN110344056A

Abstract

The invention discloses a process for preparing a cladding layer on the surface of a copper matrix by utilizing a high-speed laser cladding technology, which comprises the following steps of feeding a cladding alloy material into the surface of the copper matrix by using a laser coaxial powder feeder, and simultaneously carrying out layer-by-layer high-speed laser cladding by using a fiber laser or a fiber coupled semiconductor laser, wherein the process parameters of the laser in the cladding operation process are as follows: the focal length of the focusing lens is 250-300 mm, the cladding power is 2000-8000W, the diameter of a light spot is 0.3-1.2 mm, the cladding scanning speed is 100-400 mm/s, and the overlapping rate is 65%. The process for preparing the cladding layer is characterized in that a laser with a high-speed scanning rate is used, specific cladding alloy powder is matched, process parameters of the high-speed laser are determined, the cladding layer with compact structure, no cracks, no air holes and extremely low dilution rate can be formed on the surface of the copper matrix on the premise of not needing subsequent other treatment, and good metallurgical bonding can be formed between the cladding layer and the surface of the copper matrix.

Description

Process for preparing cladding layer on surface of copper matrix by high-speed laser cladding technology

Technical Field

The invention relates to the technical field of laser cladding, in particular to a process for preparing a cladding layer on the surface of a copper matrix by utilizing a high-speed laser cladding technology.

Background

The laser cladding is a process method which is used for placing cladding layer materials on the surface of a clad matrix in different material adding modes, melting a thin layer of the cladding layer materials on the surface of the matrix simultaneously through laser irradiation, and forming a surface cladding layer which has low dilution degree and is metallurgically combined with the matrix after rapid solidification, thereby obviously improving the wear-resisting, corrosion-resisting, heat-resisting, oxidation-resisting and electrical characteristics of the surface of a base layer, achieving the purpose of surface modification or repair, meeting the requirements on the specific properties of the surface of the material and saving a large amount of precious elements.

Currently, researchers have utilized a carbon dioxide laser or a YAG laser to perform laser cladding of a crystallizer copper plate. The cladding layer and the substrate obtained by the carbon dioxide laser cladding technology have high dilution rate and large heat affected zone, so that the physical properties of the cladding layer are reduced, the substrate has high thermal deformation rate and micro-voids and pores are formed; the dilution rate of the cladding layer and the substrate obtained by the YAG laser cladding technology is lower than that of the cladding layer of carbon dioxide laser, but the efficiency is low.

The problem analysis of the laser cladding process of the carbon dioxide laser and the YAG laser is as follows:

dilution rate: the dilution rate of the laser cladding layer is too high and generally exceeds more than 10 percent, so that the characteristic performance of the cladding material is obviously reduced;

heat-affected zone: the heat affected zone of the laser cladding linear velocity is large and generally exceeds 0.5mm, and the heat affected zone with large dimension has very obvious 'soft zone' phenomenon, so that the application occasions of the laser cladding technology under the complex stress environment condition are limited;

tempering the lap joint area: the laser cladding lapping area has poor material performance due to tempering phenomenon, so that the surface performance of a cladding layer is uneven;

surface smoothness and machining allowance: the laser cladding layer has higher surface roughness, larger laser processing allowance, larger workload of grinding processing and higher cost;

in a word, the existing technology for cladding on the surface of the crystallizer copper plate has many problems, and the industrial production requirement cannot be well met.

The high-speed laser cladding technology utilizes the ultra-conventional and ultra-high laser scanning speed to overcome the problems of the traditional cladding technology. In the current development stage, with the reduction of light spots and the remarkable improvement of light beam quality, the scanning speed reaches more than 100m/min, and the laser cladding efficiency is more than or equal to 1.3m²The work efficiency is obviously improved, the surface roughness Ra of the product is less than or equal to 10 mu m, and the laser cladding comprehensive technology with high efficiency, low cost and unique characteristics is formed.

The high-speed laser cladding speed is 100-250 times faster than that of the traditional laser cladding, the heat influence of laser on a substrate is minimum, the preparation of a cladding layer of a heat-sensitive material part can be realized, and the preparation of the cladding layer on the heat-sensitive material part cannot be realized due to the fact that the heat output is too high in the traditional method; in addition, the new process can be used for preparing brand new material combinations, such as non-ferrous metal or ferrous metal cladding layers. The finished cladding layer has high metallurgical quality, low dilution rate, small deformation and high surface smoothness, belongs to an advanced environment-friendly remanufacturing technology, can greatly reduce the subsequent machining cost of enterprises in the field of industrial remanufacturing, can effectively prolong the service life of products, and saves a large amount of later maintenance cost for the enterprises.

However, the high-speed laser cladding technology on the surface of the copper alloy has the following difficulties: the copper alloy has good heat-conducting property, small specific heat capacity, poor wetting property, hard oxide film on the surface and larger reflectivity to light spots, so that heat generated by laser is not easy to stay on the surface, higher power density is not easy to form, and a molten pool cannot be formed; secondly, the performance difference between the material systems of the copper alloy substrate and the cladding layer is large, and the failure problem in the cladding process is serious; thirdly, the toughness in the cladding layer is insufficient, and the defects of heat crack, stress and the like exist.

Disclosure of Invention

In order to solve the defects of the prior art, the invention provides a process for preparing a cladding layer on the surface of a copper matrix by utilizing a high-speed laser cladding technology, and the formed cladding layer has compact structure, no cracks, no pores, extremely low dilution rate and good metallurgical bonding with the surface of the copper matrix.

In order to achieve the purpose, the invention provides a process for preparing a cladding layer on the surface of a copper matrix by utilizing a high-speed laser cladding technology, wherein a laser coaxial powder feeder is used for feeding a cladding alloy material into the surface of the copper matrix, and a laser is used for carrying out layer-by-layer high-speed laser cladding;

the laser is selected from a fiber laser or a fiber coupling semiconductor laser;

the technological parameters of the laser in the cladding operation process are as follows: the focal length of the focusing lens is 250-300 mm, the cladding power is 2000-8000W, the diameter of a light spot is 0.3-1.2 mm, the cladding scanning speed is 100-400 mm/s, and the overlapping rate is 65%.

As a limitation to the above technical solution, the cladding alloy material comprises the following components: ni: 15% -20%; cr: 5% -10%; fe: 15% -28%; c: 6-9%; co: 9-20%; b: 2-4%; si: 3.0-5.0%; 2 percent of P; w3% -4%.

As a limitation on the technical scheme, the particle size of the cladding alloy material is 200-800 meshes.

As a limitation to the above technical solution, the process for preparing a cladding layer on the surface of a copper substrate by using a high-speed laser cladding technology comprises the following steps:

a. adjusting the focal length of a focusing lens of the laser: measuring the actual light-emitting focal position of the laser, determining the defocusing amount of the laser by measuring the focal position of the indicated red light, and further selecting the focal range of the focusing lens;

b. determining other process parameters of the laser: selecting laser cladding power, spot diameter, cladding scanning rate and lapping rate according to the matching relation of the laser scanning rate, the laser spot size and the laser power;

c. determining the technological parameters of the powder feeder: selecting the powder feeding amount according to the relationship between the powder feeding amount and the width and thickness of a single channel by adopting a rotating disc type double-cylinder powder feeder; a coaxial annular nozzle special for high-speed cladding is adopted, the height of the powder coke to the edge of the nozzle is adjusted, and the light spot of a laser is controlled to be slightly larger than the powder spot of a powder feeder;

d. and a, after regulating and controlling various process parameters in a limited range through the steps a to c, operating a laser coaxial powder feeder to feed the cladding alloy material into the surface of the copper matrix, and operating a laser to carry out layer-by-layer high-speed laser cladding while spraying powder to obtain a cladding layer.

The defocusing amount of the low-speed cladding laser has small influence range on the performance of a cladding layer, but the defocusing amount in the high-speed cladding process directly influences the cladding effect and the quality of the cladding layer, so that the focal length of a focusing mirror is selected on the basis of determining the defocusing amount of the laser in the high-speed cladding process; in addition, the matching requirement of powder feeding and laser cladding in high-speed cladding is very high, and the invention determines the cladding process condition of the fiber laser or the fiber coupling semiconductor laser aiming at the characteristic of high-speed cladding, and can prepare the cladding layer with extremely low dilution rate and good performance on the premise of not needing any subsequent treatment.

As a limitation to the technical scheme, before powder spraying and cladding operation, the surface of a copper matrix needs to be polished and decontaminated; polishing by using polishing equipment to ensure that the surface of the copper matrix is smooth and bright; and cleaning by using a stain remover to remove oil stains and other pollutants on the surface of the copper matrix.

As a limitation to the technical scheme, the thickness of the obtained cladding layer is between 80 and 1200 mu m.

In summary, according to the process for preparing the cladding layer on the surface of the copper substrate provided by the invention, by using the laser with the high-speed scanning rate and determining the process parameters of the high-speed laser according to the high-speed cladding process, and then matching with the specific cladding alloy powder, the cladding layer with compact structure, no crack, no pore and extremely low dilution rate can be formed on the surface of the copper substrate on the premise of not needing subsequent other treatment, and good metallurgical bonding can be formed with the surface of the copper substrate.

In order to ensure the quality of a cladding layer under high-speed laser, a fiber laser or a fiber coupled semiconductor laser is selected, the focal length of a focusing mirror is selected on the basis of determining the defocusing amount of the fiber laser or the fiber coupled semiconductor laser, and the technological parameters of the laser are determined according to the matching relation of the laser scanning rate, the laser spot size and the laser power, so that a molten pool can be formed instantly, a smaller heat affected zone is generated, a substrate to be cladded only generates micro deformation, and a cladding layer with extremely high density, higher wear resistance, extremely low dilution rate, good surface modification performance and high cladding efficiency is formed;

in addition, in the aspect of the composition of the cladding alloy powder, a cladding layer on the surface of a copper matrix is formed by taking nickel, iron, carbon, cobalt, boron and silicon as the basis and combining chromium, phosphorus and tungsten; the hard and malleable property and the corrosion resistance of the nickel are utilized, so that the alloy can be highly polished, is corrosion resistant and improves the mechanical strength; the wear resistance and magnetism of iron and the effective combination of element iron and chromium are utilized to ensure that the alloy forms a strong austenite structure and has the performances of high-temperature stability and hot corrosion resistance; the importance of carbon on alloy structure and performance is utilized, and the carbon is matched with iron elements to obtain an alloy with proper strength, good toughness and weldability; the characteristics of boron element that the melting point can be reduced and the fluidity can be increased are utilized, and the affinity of boron and oxygen is greater than that of metal components and oxygen, so that boron oxide is generated with oxygen when the boron is melted, the boron oxide floats on the surface of a cladding layer after being melted, and a nonporous cladding layer is formed after cooling; silicon is utilized to enhance the tensile strength, elasticity, acid resistance, heat resistance and corrosion resistance of the alloy, so that the resistivity of the alloy is increased; phosphorus is utilized to cause the matrix lattice to generate distortion and achieve solid solution strengthening, and the high-strength alloying capacity of alloys such as nickel, chromium and the like is fully exerted; tungsten is also utilized to obtain high-hardness carbide to form a dispersion strengthening phase, so that the wear resistance of the cladding layer is further improved; the alloy powder of the invention endows each raw material component with the specificity to the high-speed laser cladding process through matching and screening each raw material component.

Drawings

FIG. 1 is a schematic diagram of the present invention for determining the focal point and working spot of a laser;

FIG. 2 is a schematic diagram of the present invention for measuring the defocus of the laser;

FIG. 3 is a schematic view of a cladding layer for measuring a scan rate according to the present invention;

FIG. 4 is a schematic view of a cladding layer in measuring a powder feeding amount according to the present invention;

FIG. 5 is a graph showing the variation of the width of a single pass and the thickness of a cladding layer with the amount of powder fed in the present invention;

FIG. 6 is a schematic diagram of the thickness and surface efficiency of the cladding layer when the overlap ratio is measured according to the present invention;

FIG. 7 is a schematic diagram of the thickness of the cladding layer when measuring the laser power according to the present invention;

FIG. 8 is a cross-sectional metallographic image and an SEM image of a cladding layer in example 2 of the present invention;

FIG. 9 is a graph showing a microhardness profile of a cladding layer in example 2 of the present invention;

FIG. 10 is a graph showing the change in the coefficient of friction of the cladding layer and the substrate with time in example 2 of the present invention;

FIG. 11 is a histogram showing the cross-sectional morphology and volume of wear scars of the cladding layer and the substrate in example 2 of the present invention;

FIG. 12 is a graph showing the friction factor with temperature change in the case of the embodiment 2 of the present invention in which the cladding layer and the copper substrate are paired;

FIG. 13 is a scanning electron micrograph of a cladding junction and a metallographic micrograph of a cladding using different lasers according to a first embodiment of the present invention;

FIG. 14 is a metallographic micrograph of a clad joint according to comparative example II of the present invention.

Detailed Description

The technical solutions of the present invention will be described clearly and completely with reference to the following embodiments, and it should be understood that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Example one

The embodiment relates to a process for preparing a cladding layer on the surface of a copper matrix by using a high-speed laser cladding technology.

A cladding layer is prepared on the surface of a copper matrix by utilizing a high-speed laser cladding technology, and the cladding alloy material comprises the following raw material components in percentage by mass: ni: 15% -20%; cr: 5% -10%; fe: 15% -28%; c: 6-9%; co: 9-20%; b: 2-4%; si: 3.0-5.0%; p:2 percent; w: 3% -4%; wherein the particle size of the cladding alloy material is 200-800 meshes.

The raw material formula of the alloy material in each example is shown in the following table:

	example 1.1	Example 1.2	Example 1.3
				Ni	12g	16.44g	20g
Cr	5.2g	8g	10g
				Fe	16.8g	23g	28g
C	5.4g	7.4g	9g
				Co	12g	16.5g	19.96g
B	2g	3g	4g
				Si	3g	4g	5g
P	1.2g	1.66g	2.04g
				W	2.4g	3g	4g

Preparing a cladding layer on the surface of a crystallizer copper plate by using the alloy material of each embodiment in the table above through a high-speed laser cladding technology, wherein the preparation process of the cladding layer comprises the following steps:

A. polishing: polishing the surface of the crystallizer copper plate by using sand paper or a polishing machine to ensure that the surface of the crystallizer copper plate is smooth and bright;

B. decontamination: cleaning the surface of the crystallizer copper plate by using a stain remover acetone to remove oil stains and other contaminants on the surface of the crystallizer copper plate;

C. high-speed laser cladding: before the high-speed laser cladding of the fiber laser, firstly adjusting the technological parameters of the fiber laser in the cladding operation process;

c1, laser focus, working spot determination

Measuring the actual light-emitting focus of laser by using the fiber laser, determining the defocusing amount of the laser by measuring the position of the red light focus, and further selecting the focal range of the focusing lens;

laser power 6000W in the fiber laser, light-emitting time 0.05s, its mode of hitting is for using the laser head focus lens lower extreme as the reference surface, every time hits a point, the laser head descends 2mm, analogizes with this, hits 6 points altogether, does two sets of experiments altogether, and the facula diameter takes its mean value.

The size of each point is measured by using a body microscope, and as shown in fig. 1, it can be seen that the actual light-emitting focal position of the laser is approximately in the middle of the 260mm position and the 240mm position, that is, the 252mm position.

Through the measurement of the indicated red light focal position, as shown in fig. 2, it is found that there is a deviation of about 5mm between the red light focal position and the actual light-emitting position, that is, the red light focal position is located at a position about 5mm above the actual light-emitting focal position.

The red light focus position is the laser head indication distance, namely the focal length of the focusing lens, the actual light-emitting focus position can be determined in a way that the laser is out-of-focus, the out-of-focus amount during working is calculated according to the actual light-emitting focus position, and then the focal length range of the focusing lens is selected.

C2 determination of Coke breeze

The coaxial annular nozzle special for high-speed cladding is adopted, the coaxial annular nozzle supports high-power and long-time high-speed work, red copper materials with high heat dissipation performance are used, powder is discharged finely, and a compact cladding layer is easy to form; the performance parameters are as follows: cooling mode, water cooling; the size of the powder spot is 0.6 mm; powder flow shape, annular; the powder feeding flow is 1-60 g/min; the powder granularity is 20-150 mu m; size, 100 × 114.5 × 49; mass, 0.62 kg.

Coke breeze to nozzle edge height

As can be seen from the above table, the powder feeding system for ultra-high-speed laser cladding is significantly different from the conventional cladding powder feeding system in gas pressure, flow rate, powder feeding efficiency, powder particle size and the like, and simultaneously overcomes the problems of powder blockage and static electricity in fine powder transportation. The high-speed laser cladding head has a high convergence characteristic, can realize long-distance conveying of powder with the powder granularity of 200-800 meshes, improves the powder utilization rate to the maximum extent by controlling the matching of the powder spot size and the light spot size, is not easy to generate defects such as air holes, fluctuation and direction difference, has a self-adaptive deposition thickness control function, and avoids non-uniform cladding thickness.

C3, measurement of scanning Rate

Under the condition that the laser power, the spot diameter, the powder spot and the powder feeding amount are consistent, the single-channel cladding effect is measured under the condition of different scanning rates; wherein the laser power is 6000W, the laser defocusing amount is 5mm, the spot diameter is 1.0mm, the powder coke height is 2mm, the powder feeding air flow is 9LPM, the powder feeding air flow pressure is 0.4MPa, the protective air flow is 13LPM, the protective air flow pressure is 0.5MPa, the powder feeding amount is 22g/min, the measurement scanning rates respectively achieve the cladding effect under 50mm/s, 100mm/s, 200mm/s, 300mm/s and 400mm/s, and a single-pass metallographic graph of the cladding layer shown in the figure 3 is obtained;

and calculating the laser cladding dilution rate at each scanning speed through the initial height H of the cladding layer, the depth H of the molten pool and related physical parameters of the cladding layer and the matrix detected by a metallographic method.

From the above table, in the test error range, under the condition of certain laser parameters, the dilution rate of the laser cladding layer is reduced along with the increase of the scanning rate; in addition, as can be seen from the above table and fig. 3, the dilution ratio of the laser cladding layer is very low, the single-pass experiment with the scanning rate of 100mm/s has the best effect under the coordination of various laser parameters, and the size of the light spot of the visible laser is slightly larger than that of the powder feeder.

C4, powder feeding amount measurement

The rotary disc type double-cylinder powder feeder is adopted, the rotary disc type double-cylinder powder feeder realizes powder feeding kinetic energy by adopting an advanced gas dynamics principle, the required ranges of gas flow, powder disc rotation and preheating temperature are accurately controlled, the powder feeding efficiency and the particle size are changed by replacing different powder feeding discs, the powder feeding interval and the particle size range are further expanded, the powder feeding interval is 0.4-300 g/min, and the particle size range is 20-250 mu m.

Under the conditions that the powder feeding gas is 9LPM/Mpa, the protective gas is 0.5LPM/Mpa, the laser defocusing amount is 5mm, the powder spot height is 2mm, the spot diameter is 1.0mm, the laser power is 6000W, the scanning speed is 100mm/s and other relevant parameters are not changed, the powder feeding amount is increased, and the single-channel width and the single-channel thickness are measured.

Serial number	Powder delivery amount (r/min)	Thickness (μm)	Width of metallographic phase (mum)	Body type width (mum)
					1	4	80	1673	1141
2	5	105	1392	1016
					3	6	135	1223	827

As can be seen from the above table, under the condition that the laser power, the scanning rate and other related parameters are not changed, the powder feeding amount is increased, the thickness of a single channel is increased, the width is reduced, as shown in fig. 4, the surface molten pool is narrowed, and the amount of powder agglomerated on the two sides of the cladding single channel in a semi-melting state is increased; the center of each single channel is provided with fine cracks approximately along the cladding single channel direction, and the reason of causing the microcracks is mostly that low-melting-point metal compounds appear in the final solidification center of a molten pool, the toughness and plasticity are poor, and when the molten pool is solidified and cooled, the cracks are caused by transverse tensile stress from two sides of the cladding channel.

As shown in FIG. 5, under the condition that the laser power, the scanning rate and other relevant parameters are not changed, the powder feeding amount has a certain proportional relationship with the single-channel width and the cladding layer thickness, and the graph shows that the cladding layer well combined with the base material can be obtained under the power of 6000W at the powder feeding amount of 6r/min, namely 60 g/min.

C5, determination of the overlap ratio

Under the condition that relevant parameters such as laser power, scanning speed, powder feeding amount and the like are not changed, the thickness and the surface efficiency of the cladding layer under different lap joint rates are measured.

As the bulk forming efficiency per unit time is one layer thickness, the bulk forming efficiency is higher when the lap ratio is 65% in combination with the above table and as can be seen from fig. 6, since good metallurgical bonding can be obtained.

C6 laser Power measurement

And (3) determining the thickness of the cladding layer under different powers without changing relevant parameters such as scanning speed, powder feeding amount, lap joint rate and the like.

As can be seen from fig. 7 and the above table, the thickness of the cladding layer increases with the increase of the laser power without changing the related parameters such as the scanning rate, the powder feeding amount, and the overlapping ratio.

After being regulated and controlled by C1-C6, the technological parameters of the fiber laser are regulated as follows: the focal length of the focusing lens is 250-300 mm, the cladding power is 2000-6000W, the diameter of a light spot is 0.3-1.2 mm, the cladding scanning speed is 100-400 mm/s, and the lap joint rate is 65%; feeding cladding alloy materials with the granularity of 200-800 meshes to the surface of the crystallizer copper plate by using a laser coaxial powder feeder, and simultaneously carrying out layer-by-layer high-speed laser cladding by using a fiber laser, wherein the thickness of a single layer of a formed cladding layer is 0.08-1.2 mm.

Example two

This example relates to the testing of the properties of the cladding layer prepared in example one.

The cladding alloy materials in the mixture ratio of the embodiment 1.1-1.3 are prepared into a sample under the process of the invention.

(1) Detection of phase Performance

Randomly extracting a plurality of samples from the prepared samples to be used as samples, and carrying out object image analysis on the high-speed laser cladding layer of each sample by utilizing a DX-2700X photographic diffractometer to obtain a cladding layer cross section metallographic image shown in figure 8 (a); as can be seen from fig. 8(a), the upper portion is a cladding layer, the lower portion is a mold copper plate, and the cladding layer and the mold copper plate have a distinct interface. At the interface, the substrate and the cladding layer are metallurgically bonded, the thickness of the cladding layer is about 0.4mm, no air holes or cracks exist in the cladding layer, and the internal quality of the cladding layer is good.

FIG. 8(b) is an SEM image of the cladding layer showing the bonding of the cladding layer to the interface of the mold copper plate, wherein the vertical lines show the position and direction of the line scanning. As can be seen from fig. 8(b), the elements are uniformly distributed throughout the entire cladding layer.

(2) Measurement of hardness Properties

The Vickers hardness of the cladding layer of the sample is measured by an HVS-1000 type digital microhardness meter, the loading load is 200g, the loading time is 10s, and the average value is taken after 5 times of measurement. The measurement is performed every 0.1mm from the surface of the high-speed laser cladding layer vertically downward, three points are measured transversely on the same vertical distance, the intervals of the three points are all 0.2mm, then the average value of the three points is taken as the Vickers hardness value on the vertical distance, and the Vickers hardness curve of the sample cladding layer along the thickness direction as shown in FIG. 9 is obtained.

As can be seen from fig. 9, the highest hardness appears in the subsurface layer as seen from the microhardness curve, the highest hardness is 786HV, the average hardness of the cladding layer is 567HV, and the hardness of the mold copper plate is only 145 HV. Compared with a crystallizer copper plate, the hardness of the cladding layer is improved by 4-5 times, which means that the local resistance of the cladding layer prepared by the method to the invasion of an external object is stronger.

(3) Detection of wear resistance

A plurality of samples with cladding layers are randomly extracted from the prepared samples, and a plurality of crystallizer copper plates without cladding layers are selected as comparison samples.

1. Comparison of coefficients of friction

FIG. 10 is a graph showing the change of the friction coefficient with time of the cladding layer and the mold copper plate. As can be seen from the curves, the maximum friction coefficient of the copper plate of the crystallizer is 0.43, and the average friction coefficient is 0.4; the maximum friction coefficient of the cladding layer is 0.807, the average friction coefficient is 0.614, the friction running of the cladding layer is relatively smooth in the whole friction process, and the final friction coefficient fluctuates around 0.6.

2. Comparison of wear amounts

And (3) testing the surface wear resistance of the test article with the cladding layer and the test article without the cladding layer by adopting an MFT-R4000 high-speed reciprocating friction wear testing machine, cleaning the test article with acetone after the test is finished, and testing the friction quantity after drying.

The frictional wear amount is measured by a NanoMap500LS scanning three-dimensional surface profiler, and the principle is that a cross section of a grinding trace of a test sample is scanned by a scanning probe and then analyzed by SPIP5.13 software. Scanning each sample for 5 times, so as to measure the average cross-sectional area of the grinding crack, and multiplying the average cross-sectional area by the length of the grinding crack to obtain the volume of the grinding crack; wherein, fig. 11(a) is the cross-sectional morphology of the wear scar of the cladding layer and the copper plate matrix, and fig. 11(b) is the volume histogram of the wear scar of the cladding layer and the copper plate matrix.

As shown in FIG. 11(a), the mold copper plate sample had a wear scar depth of about 70 μm and a width of about 1600 μm; the depth of the wear mark of the cladding layer is about 30 μm, and the width is about 1200 μm. Under the same test conditions, the grinding mark and the grinding width of the cladding layer are both smaller than those of the crystallizer copper plate of the crystallizer.

As can be seen from fig. 11(b), the wear scar volume of the cladding layer is significantly smaller than that of the mold copper plate. The high-speed laser cladding of the surface of the crystallizer copper plate by using the high-speed laser cladding process is beneficial to improving the wear resistance of the product and prolonging the service life of the product.

(4) Detection of high temperature resistance

FIG. 12 is a variation curve of friction factor at different temperatures for a melt-coated layer sample and a mold copper plate without a melt-coated layer as a matched pair under the same friction condition. As can be seen from fig. 12, 1, numerically, the friction factor of the cladding layer sample is always smaller than that of the crystallizer copper plate without the cladding layer, and the difference amplitude is large; 2. in the trend, with the rise of the test temperature, the friction factor of the crystallizer copper plate without the cladding layer rises firstly and then falls, and the fluctuation amplitude is large; the friction factor of the cladding layer test sample is gradually reduced, but the fluctuation range is small. In a word, the friction factor of the cladding layer test sample is not greatly influenced by temperature change, and the high temperature resistance of the cladding layer test sample is far better than that of a crystallizer copper plate.

Comparative example 1

The comparative example relates to the effect of other lasers on the cladding layer on the surface of a copper substrate.

Selecting DL-HL-T10000 type CO₂The laser selects the best laser mode (low-order mode) by an organic glass spot burning method to obtain a stable plasma arc state, and calculates the defocusing amount by using a red light indicating point, wherein the process parameters of the laser are as follows: the focal length f of the focusing mirror is 200mm, the cladding power P is 6000W, the diameter D of a light spot is 2mm, the cladding scanning speed V is 6m/min, and the overlapping rate is 50%; preheating the copper base material at the speed of 600mm/min by using a laser, measuring by using an infrared thermometer, and quickly cladding the nickel-based alloy when the preheating temperature reaches 400-500 ℃.

As shown in fig. 13(a) which is a metallographic micrograph after cladding by using a carbon dioxide laser, and fig. 13(b) which is a scanning electron micrograph of a junction of the cladding layer and the copper substrate, it can be observed from the micrograph that the cladding layer is an obvious layered structure, is loose between layers, has obvious holes, and has holes and clear boundaries between the cladding layer and the copper substrate, and the cladding layer is easy to fall off and is not wear-resistant due to gaps observed by the scanning electron micrograph.

Selecting a 6000W optical fiber laser, adopting a rotating disc type double-cylinder powder feeder and a special coaxial annular nozzle for high-speed cladding, operating the laser coaxial powder feeder to feed cladding alloy materials into the surface of a copper matrix, and operating the laser to carry out high-speed laser cladding layer by layer while spraying powder to obtain a cladding layer. Measuring the actual light-emitting focal position to calculate the laser defocusing amount, and measuring and indicating the red light focal position to further determine the laser defocusing amount, wherein the specific process parameters of the fiber laser are as follows: the laser power is 6000W, the laser defocusing amount is 5mm, the spot diameter is 1.0mm, the coke breeze height is 2mm, the powder feeding air flow is 9LPM, the powder feeding air flow pressure is 0.4MPa, the protective air flow pressure is 0.5MPa, and the powder feeding amount is 22 g/min.

Fig. 13(c) and 13(d) are OM photographs and SEM photographs of the junction of the cladding layer and the copper substrate after high-speed cladding, and it can be seen that the microstructure is dense after laser cladding, and the cladding layer and the copper substrate are in good metallurgical bonding.

Comparative example No. two

The comparative example relates to the influence of alloy powder with different raw material components on the surface cladding layer of the copper matrix.

The nickel-based self-fluxing alloy powder with the similar composition to the copper base material in the example 1.1 is selected, and the main components are as follows: 0.018g, Si: 1.2g, B: 0.66g, Fe: 0.3g, Cu: 12g, Ni: 45.822 g;

selecting a 6000W optical fiber laser, adopting a rotating disc type double-cylinder powder feeder and a special coaxial annular nozzle for high-speed cladding, operating the laser coaxial powder feeder to feed cladding alloy materials into the surface of a copper matrix, and operating the laser to carry out high-speed laser cladding layer by layer while spraying powder to obtain a cladding layer. The specific process parameters of the fiber laser are as follows: the laser power is 6000W, the laser defocusing amount is 5mm, the spot diameter is 1.0mm, the coke breeze height is 2mm, the powder feeding air flow is 9LPM, the powder feeding air flow pressure is 0.4MPa, the protective air flow pressure is 0.5MPa, and the powder feeding amount is 22 g/min.

As shown in FIG. 14, it was found that the copper substrate was diluted significantly, the cladding layer had many holes, which caused defects and microcracks, stress concentration, and the cladding layer was easily peeled off and was not wear-resistant.

In conclusion, aiming at the characteristics of high-speed cladding, the invention determines the cladding process conditions of the laser, and is matched with special high-speed cladding alloy powder, so that a cladding layer with compact structure, no cracks, no air holes and extremely low dilution rate can be formed instantly on the premise of not needing any subsequent treatment, and good metallurgical bonding can be formed with the surface of the copper matrix; in addition, the matrix to be clad only generates slight deformation.

Claims

1. A process for preparing a cladding layer on the surface of a copper matrix by utilizing a high-speed laser cladding technology is characterized by comprising the following steps of: feeding the cladding alloy material to the surface of the copper matrix by using a laser coaxial powder feeder, and simultaneously carrying out layer-by-layer high-speed laser cladding by using a laser;

the technological parameters of the laser in the cladding operation process are as follows: the focal length of the focusing lens is 250-300 mm, the cladding power is 2000-8000W, the diameter of a light spot is 0.3-1.2 mm, the cladding scanning speed is 100-400 mm/s, and the lap joint rate is 65%;

the cladding alloy material comprises the following raw material components in percentage by mass:

Ni：15％～20％；Cr：5％～10％；Fe：15％～28％；C：6～9％；Co：9～20％；B：2～4％；Si：3.0～5.0％；P:2％；W3％～4％。

2. the process for preparing a cladding layer on the surface of a copper matrix by using a high-speed laser cladding technology according to claim 1, wherein the process comprises the following steps: the particle size of the cladding alloy material is 200-800 meshes.

3. The process for preparing a cladding layer on the surface of a copper matrix by using a high-speed laser cladding technology according to claim 1 or 2, which is characterized by comprising the following steps:

4. The process for preparing a cladding layer on the surface of a copper matrix by using a high-speed laser cladding technology according to claim 3, wherein the process comprises the following steps: before powder spraying cladding operation, polishing and decontamination treatment are carried out on the surface of a copper matrix; polishing by using polishing equipment to ensure that the surface of the copper matrix is smooth and bright; and cleaning by using a stain remover to remove oil stains and other pollutants on the surface of the copper matrix.

5. The process for preparing a cladding layer on the surface of a copper matrix by using a high-speed laser cladding technology according to claim 3, wherein the process comprises the following steps: the thickness of the obtained single layer of the cladding layer is between 80 and 1200 mu m.