Method for preparing high bonding strength tin bronze coating based on high energy laser / supersonic particle composite

Abstract

The present invention discloses a method for preparing a high-bonding-strength tin bronze coating based on a high-energy laser / supersonic particle composite. The method comprises the following steps: synchronously introducing a high-energy laser beam during the high-speed flight deposition of supersonic particles, adjusting the overlap ratio and position of the high-energy laser spot and the high-speed deposition powder spot, changing the action position of the laser and the heat distribution inside the coating during the particle deposition process; the coating prepared by this process has a good interface bonding state and exhibits different characteristics at different locations; the outer side of the coating, which is mainly subjected to particle plastic deformation, has higher dislocations and density, and has a work hardening effect, so that the deposited coating has good friction and wear resistance; the inner side of the coating, which is mainly subjected to particle recrystallization, has fewer internal grain defects and good ductility, which is conducive to improving mechanical properties; the gradient of the internal and external functions of the coating prolongs the service life of the coating.

Description

Technical Field

[0001] The present invention belongs to the field of laser composite manufacturing, and in particular relates to a method for preparing a high-bonding-strength tin bronze coating based on high-energy laser / supersonic particle composite. Background Art

[0002] Copper and copper alloys have excellent electrical and thermal conductivity, along with good ductility, and are widely used in daily life and production. Tin bronze, due to its excellent corrosion and wear resistance and good processing properties in sliding and frictional working environments, is often used in the manufacture of components such as bushings, bearings, and gears. However, long-term use of tin bronze in high-intensity friction environments can easily cause wear on contact surfaces and deformation of components, leading to reduced electrical and thermal conductivity, thus affecting machine operation. When components are damaged, two common methods are surface strengthening or targeted repair of the failed part surface.

[0003] Surface coating technology is currently a key research area in mechanical manufacturing. It can quickly repair surface defects and alloy components, strengthening the surface while saving materials and preventing environmental pollution. Currently, the main surface coating technologies used by researchers at home and abroad to prepare copper and copper alloy coatings include physical vapor deposition, chemical vapor deposition, laser cladding, thermal spraying, and cold spraying. The physical vapor deposition coating has a weak bond with the substrate and poor wear resistance. The chemical vapor deposition technology has high requirements for system sealing. The laser cladding forming is poor and the cladding layer has many defects such as pores and cracks. The high temperature of the thermal spray process will cause the coating to undergo phase change, oxidation and cracking. Cold spraying uses low-heat and high-speed solid particles to impact the substrate to produce violent deformation and thus deposit to form a coating. Compared with some high-heat input processing technologies, cold spraying does not change the organizational structure and physical and chemical properties of the original powder. Oxidation, composition segregation and other problems basically do not occur during the deposition process. It has outstanding advantages in applications such as part surface repair. However, the bonding between coating particles is mainly mechanical, resulting in a larger porosity and lower bonding strength, and it is not suitable for depositing high-hardness materials such as tin bronze.

[0004] Supersonic laser deposition (SLD) is an advanced material deposition technique that combines laser and cold spray technology. This technique uses a laser as a heat source, simultaneously irradiating the substrate as high-speed cold-sprayed particles impact the substrate. This softens the powder and substrate, reduces the critical deposition velocity required for particle deposition, eliminates large-scale metallurgical phase transitions, and expands the range of materials that can be deposited, such as tin bronze. However, SLD coatings still primarily bond mechanically, resulting in relatively low bond strength. The severe deformation of particles also significantly reduces ductility. Summary of the Invention

[0005] In response to the problems of poor bonding strength, high porosity and low ductility in the coatings obtained by depositing tin bronze materials using the above-mentioned supersonic laser deposition technology, the present invention provides a method for preparing high-bonding-strength tin bronze coatings based on a high-energy laser / supersonic particle composite. By adjusting the offset ratio and direction of the deposited powder spot and the laser spot, the heat distribution of the laser in the coating during the particle deposition process is changed, thereby preventing the substrate from absorbing too much heat and melting, and strengthening the metallurgical bonding between the particles in the coating, reducing its porosity, and improving the bonding ability and ductility of the coating.

[0006] The technical solutions of the present invention are as follows:

[0007] A method for preparing a high-bonding-strength tin-bronze coating based on a high-energy laser / supersonic particle composite comprises the following steps:

[0008] (1) Pre-treating the substrate and then fixing it on a workbench;

[0009] The substrate is preferably made of 45# steel. The specific pretreatment method is as follows: first, the substrate is sandblasted with 22# quartz sand. Sandblasting can remove stains on the substrate surface and increase the surface roughness, which is conducive to the combination of powder and particles; the sandblasted substrate is immersed in anhydrous ethanol for ultrasonic cleaning; finally, the substrate is taken out, wiped with anhydrous ethanol, and dried with a hair dryer;

[0010] (2) drying the tin bronze material powder in a vacuum drying oven and then placing it in a scraper-type pressure powder feeder;

[0011] The drying conditions are: 90-120°C, 2 hours;

[0012] (3) Setting the spraying conditions: powder particles are fed into the supersonic laser deposition nozzle through a powder feeder, nitrogen is selected as the carrier gas, the carrier gas pressure is 1.5-2.5 MPa, the carrier gas preheating temperature is 600℃-800℃, the spraying distance is 10-25 mm, the powder feeding speed is 0.5-1 r / min, and the scanning speed is 3-9 mm / s;

[0013] (4) Setting the power parameters of the high-energy laser beam on the laser control panel;

[0014] The laser is a fiber-coupled semiconductor laser, and the laser power is controlled at 1.7 to 2 kW;

[0015] (5) Assemble and fix the supersonic laser deposition nozzle and laser processing head on the fixture of the robotic arm, calibrate the angles of the nozzle and laser head relative to the substrate, adjust the laser focus position to offset the laser spot and the deposited powder spot, and plan the spray scanning path;

[0016] Specifically, the supersonic laser deposition nozzle is kept substantially perpendicular to the substrate surface, and the angle between the laser head and the nozzle normal is 30° to 60°; the laser spot and the deposited powder spot offset ratio is 25% to 50%, and the laser spot and the deposited powder spot offset ratio refers to the ratio of the area of ​​the laser spot offset powder spot to the total area of ​​the powder spot. At the same time, relative to the spraying direction, the powder spot is in front and the laser spot is in the back;

[0017] (6) Turn on the powder accelerated supersonic laser deposition nozzle and laser to output high energy laser and supersonic powder particles, and realize the deposition of high hardness material under the condition of laser spot and deposition powder spot offset.

[0018] The device for implementing the method of the present invention comprises: a scraper-type pressure powder feeder, a supersonic laser deposition nozzle and its control system, a laser device, a robotic arm mobile device and a nitrogen supply pipeline system.

[0019] The technical principle of the present invention is:

[0020] By changing the process of high-energy laser / supersonic particle composite technology, that is, adjusting the relative positions of the laser spot and the deposited powder spot, changing the heat distribution of the laser in the coating during spraying, and adopting a low scanning speed and high power process strategy, the substrate is prevented from absorbing too much heat and melting, while the metallurgical bonding between the coating particles is enhanced, thereby improving the bonding ability and comprehensive mechanical properties of the tin bronze coating.

[0021] The present invention uses a circular laser ( Figure 1 ), laser heating is more uniform. High-power laser radiation of 1.7-2kW produces a denser tin-bronze coating. The circular laser spot is positioned backward relative to the deposited powder spot, and their partial overlap prevents the substrate from absorbing excessive heat and melting. This also allows for greater heat accumulation in the coating, leading to metallurgical bonding and recrystallization, improving the overall coating performance.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. The method provided by the present invention for preparing a high-bonding-strength tin-bronze coating based on a high-energy laser / supersonic particle composite is an environmentally friendly surface coating repair technology. It can repair damaged surfaces of parts, such as damaged surfaces of tin-bronze bearings that have been in service in sliding friction environments for a long time, by performing raw material repair and surface strengthening on new products, thereby greatly extending the service life of the product, avoiding waste, saving materials, and complying with the concept of green development.

[0024] 2. The present invention provides a method for preparing a high-bonding-strength tin-bronze coating based on a high-energy laser / supersonic particle composite. Compared with pure cold-sprayed tin-bronze coatings that are brittle and have weak inter-particle bonding, this method uses a laser spot and deposition powder spot offset process to change the laser action area and energy distribution during the tin-bronze powder deposition process to regulate the interface bonding between the coating particles, further improving the density of the tin-bronze coating structure and significantly improving its wear resistance / tensile properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Schematic diagram of the spraying principle of a method for preparing a high-bonding-strength tin bronze coating based on a high-energy laser / supersonic particle composite provided by the present invention; wherein 1-deposited particles, 2-supersonic airflow, 3-laser irradiation, 4-substrate, 5-corresponding Figure 2 Middle A area, 6-corresponding Figure 2 Middle B area, 7-corresponding Figure 2 Middle C area.

[0026] Figure 2 This is the cross-sectional morphology of the tin bronze coating prepared in Example 1 of the present invention with a laser spot and a deposited powder spot offset ratio of 25% (photographed with a scanning electron microscope, a magnification of 100 times).

[0027] Figure 3 This is the interface between the tin bronze coating and the substrate prepared in Example 1 of the present invention with a laser spot and a deposited powder spot offset ratio of 25% (photographed with a scanning electron microscope, a magnification of 1,000 times).

[0028] Figures 4-6 The enlarged images of any one of the A, B, and C regions of the tin bronze coating prepared in Example 1 of the present invention under the condition of a 25% offset ratio between the laser spot and the deposited powder spot (photographed by a scanning electron microscope, with a magnification of 5,000 times); the A, B, and C regions and Figure 2 The corresponding markings. DETAILED DESCRIPTION

[0029] The present invention is further described below through specific embodiments in conjunction with the accompanying drawings, but the protection scope of the present invention is not limited thereto.

[0030] The schematic diagram of the principle of the method for preparing a high-bonding-strength tin bronze coating based on high-energy laser / supersonic particle composite of the present invention is as follows: Figure 1 As shown in FIG. 1 , solid particles 1 gain sufficient kinetic energy in the supersonic airflow 2 to be accelerated, and then are emitted vertically to the substrate 4 .

[0031] In the first stage, when the deposited particles are deposited in the powder spot area without laser action, the coating structure has the deposition characteristics of a single cold spray coating, with small particle deformation and many pores;

[0032] In the second stage, when the deposited particles are deposited in the overlapping area of ​​the laser spot and the deposited powder spot, the laser directly acts on the deposited coating and particles, softening their surface and generating high temperature, so that the coating recrystallizes and the grains grow, and the elements diffuse between the particles to form a metallurgical bond. At the same time, the heat conduction effect of the laser on the deposited coating in this area and the impact of subsequent particles make the coating formed in the first stage more dense and recrystallized.

[0033] In the third stage, at the end of the previous two stages, the subsequent offset part of the laser directly scans the deposited coating, heating it, making the bonding between the particles more dense and uniform, and the coating surface remelting.

[0034] Example 1

[0035] Select 100mm×60mm×10mm No. 45 steel as the substrate, sandblast it with 22# quartz sand, and then immerse the No. 45 steel plate in anhydrous ethanol and ultrasonically clean it for 15 minutes. After cleaning, take it out and wipe it with anhydrous ethanol and dry it with a hair dryer, and then fix it on the workbench.

[0036] Spherical CuSn10 powder with a particle size range of 15 μm to 53 μm is placed in a vacuum drying oven for drying (drying at 90° C. to 120° C. for 2 hours) to remove moisture, and then placed in a powder feeder.

[0037] On the supersonic laser deposition nozzle control panel, the carrier gas (nitrogen) pressure was set to 2.5 MPa, the carrier gas preheating temperature was set to 700°C, the spraying distance was set to 25 mm, the powder feeding speed was set to 0.8 r / min, the scanning speed was set to 3 mm / s, and the laser power was set to 1.8 kW. The relative positions of the supersonic laser deposition nozzle and the laser head were adjusted so that the offset ratio of the deposited powder spot and the laser spot was 25%. At the same time, the nozzle was ensured to be perpendicular to the substrate surface, the normal angle between the laser head and the substrate surface was set to 30°, the scanning path was planned to set the overlap rate to 50%, and the sprayed samples were subjected to metallographic mounting, grinding, polishing and corrosion. Finally, the microstructure inside the coating was observed by scanning electron microscopy.

[0038] The cross-sectional morphology of the CuSn10 tin bronze laser spot and the deposited powder spot offset coating was observed at a magnification of 100 times using a scanning electron microscope (SEM, model: Zeiss EV018). Figure 2 As shown, the particles inside the coating are densely bonded and no obvious pores are found.

[0039] The interface between the coating and the substrate was observed using SEM at a magnification of 1k times. Figure 3 As shown in the figure, the effective impact of particles on the substrate causes the material surface to lose its shear strength, making it more likely to undergo a large degree of tangential deformation, which gives the coating and the substrate better mechanical bite ability.

[0040] The coating was observed using SEM at a magnification of 5k times. Figure 2 A magnified image of any part of the marked A, B, or C areas, such as Figures 4-6 As shown, Figure 4 This is an enlarged view of an optional part of area A. The particles are mechanically interlocked and the strain is large. Figure 5 This is an enlarged view of an optional part of area B. The degree of recrystallization of the particles is greater than that of area C, and the bonding interface between the particles disappears. Figure 6 This is a magnified image of a selected area in region C. Numerous fine equiaxed crystals appear within the particles, while interparticle bonding occurs at the particle interfaces, creating numerous circular pores. Regions B and C exhibit excellent ductility due to recrystallization. The overall coating density and interfacial bonding strength are high.

[0041] The contents described in the embodiments of this specification are merely an enumeration of the implementation forms of the inventive concept. The scope of protection of the present invention should not be regarded as limited to the specific forms described in the embodiments. The scope of protection of the present invention also includes equivalent technical means that can be thought of by those skilled in the art based on the inventive concept.

Claims

1. A method for preparing a high-bonding-strength tin-bronze coating based on high-energy laser / supersonic particle composite, characterized in that: The following steps are involved: (1) Pre-treating the substrate and then fixing it on a workbench; (2) drying the tin bronze material powder in a vacuum drying oven and then placing it in a scraper-type pressure powder feeder; (3) Setting the spraying conditions: powder particles are fed into the supersonic laser deposition nozzle through a powder feeder, nitrogen is selected as the carrier gas, the carrier gas pressure is 1.5-2.5 MPa, the carrier gas preheating temperature is 600℃-800℃, the spraying distance is 10-25 mm, the powder feeding speed is 0.5-1 r / min, and the scanning speed is 3-9 mm / s; (4) Set the power parameters of the high-energy laser beam on the laser control panel, and control the laser power at 1.7 to 2 kW; (5) Assemble and fix the supersonic laser deposition nozzle and laser processing head on the fixture of the robotic arm, calibrate the angles of the nozzle and laser head relative to the substrate, adjust the laser focus position to offset the laser spot and the deposited powder spot, and plan the spray scanning path; The supersonic laser deposition nozzle is kept perpendicular to the substrate surface, and the angle between the laser head and the nozzle normal is 30° to 60°; The laser spot and the deposited powder spot offset ratio is 25% to 50%. The laser spot and the deposited powder spot offset ratio refers to the ratio of the area of ​​the laser spot offset powder spot to the total area of ​​the powder spot. In addition, the powder spot is in front and the laser spot is in the back relative to the spraying direction. (6) Turn on the powder accelerated supersonic laser deposition nozzle and laser to output high energy laser and supersonic powder particles, and realize the deposition of high hardness material under the condition of laser spot and deposition powder spot offset.

2. The method for preparing a high-bonding-strength tin-bronze coating based on high-energy laser / supersonic particle composite according to claim 1, characterized in that: In step (1), the substrate is made of 45# steel.

3. The method for preparing a high-bonding-strength tin-bronze coating based on high-energy laser / supersonic particle composite according to claim 1, characterized in that: In step (1), the substrate pretreatment method is: first, the substrate is sandblasted with 22# quartz sand, then the sandblasted substrate is immersed in anhydrous ethanol for ultrasonic cleaning, and finally, the substrate is taken out, wiped with anhydrous ethanol and dried with a hair dryer.

4. The method for preparing a high-bonding-strength tin-bronze coating based on high-energy laser / supersonic particle composite according to claim 1, characterized in that: In step (4), the laser is a fiber-coupled semiconductor laser.

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