Method for preparing F431 coating by adopting laser thermal spraying technology

Abstract

The invention belongs to the technical field of laser additive manufacturing, laser cladding and thermal spraying, and relates to a method for preparing an F431 coating by adopting a laser thermal spraying technology. The method comprises the following steps that after the laser thermal spraying gun is assembled, a base body is arranged below the spraying gun, power sources of all devices are turned on, shielding gas is turned on, and a laser light path is calibrated; spraying parameters are set, the spraying distance ranges from 50 mm to 120 mm, the spraying distance is the distance between the bottommost end of a spraying gun and a base body, the laser power ranges from 2.4 kw to 4 kw, the air knife flow ranges from 20 L / min to 40 L / min, the scanning rate ranges from 100 mm / s to 120 mm / s, and the powder feeding amount ranges from 2.0 r / min to 3.0 r / min; and spraying, wherein the scanning frequency is controlled, so that the thickness of the coating is within the range of 500-800 mm. According to the technology, the spraying distance of the spraying gun is adjustable, the working angle of the spraying gun is adjustable, and the technology is suitable for the steam turbine blade water erosion protection and repair limited space environment; the method has the advantages of wider application scene, higher coating manufacturing efficiency and simpler operation, and is suitable for various working environments.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of laser additive manufacturing, laser cladding and thermal spraying technology, and relates to a method for preparing an F431 coating by using laser thermal spraying technology. BACKGROUND

[0002] Surface modification technology refers to a kind of technology that introduces specific structures, components or properties on the surface of materials through physical, chemical or biological methods, so as to improve the wear resistance, corrosion resistance, biocompatibility, optical performance and the like of the surface of the materials. Common surface modification technologies include thermal spraying, electroplating, laser cladding and the like.

[0003] Thermal spraying technology is simple to operate, has a high deposition speed and is strong in material adaptability, but the coating prepared by thermal spraying is mechanically combined with the substrate, the coating has a low bonding strength, and voids and other defects are easily formed in the coating. In harsh working conditions, the service life may be difficult to meet the demand.

[0004] Electroplating is a technology for attaching a metal or alloy plating layer on the surface of a substrate (such as metal, plastic, ceramic or the like) by using the principle of oxidation and reduction. Electroplating can improve the wear resistance and corrosion resistance of the material, but the coating thickness is generally only a few micrometers thick, and like thermal spraying, the coating is prone to failure in a complex working environment.

[0005] Laser cladding is a technology for forming a coating by heating and melting powder and combining the powder with a substrate by using a laser as a heat source. In the conventional laser cladding process, the working distance of the cladding head is too short, generally only a few millimeters to tens of millimeters, and the laser heat input is too large, which easily leads to a large deformation of the workpiece. Moreover, the reachability of the laser head is poor, and when a small deformation is required, strengthening or remanufacturing is needed, and it is difficult to achieve the desired use effect.

[0006] Therefore, the present application selects the newly invented laser thermal spraying technology. This technology theoretically combines the advantages of thermal spraying and laser cladding technology, but because it is a newly born technology, there is a lack of technical research in actual application. Therefore, it is urgent to research and explore the process of laser thermal spraying technology and develop this new technology with excellent application prospects. SUMMARY

[0007] In order to solve the problems in the prior art, the present application uses a new laser thermal spraying gun to research a process for preparing an F431 coating. The gun can combine the advantages of laser cladding technology and thermal spraying technology, but there is still a lack of specific research on the process in actual use. The present application uses the laser thermal spraying gun to prepare an iron-based coating on the surface of 304 stainless steel by using F431 powder, and studies the performance of the coating.

[0008] The laser thermal spraying technology adopted in the application belongs to one of surface modification technologies. In order to explore the process of the laser thermal spraying technology, the application selects 304 stainless steel as the substrate, and studies the process method for preparing F431 coating on the surface of the substrate by using the laser thermal spraying technology. By using the process, a coating with certain thickness and hardness can be prepared on the surface of the 304 stainless steel, and the thickness and the microstructure of the coating can be adjusted according to the requirement.

[0009] The technical solution adopted by the application to solve the technical problem is: A method for preparing F431 coating by using laser thermal spraying technology, the F431 coating is prepared by using the novel laser thermal spraying gun in the patent with the application number CN202510827464.8, and the method specifically comprises the following steps: (1) Assemble the laser thermal spraying gun, connect the laser, and connect the six-axis robot through the adapter plate; turn on the cooling system of the laser, and turn on the power supply of the laser; the laser used in the experiment is MFSC-6000 type produced by Chuangxin Laser; turn on the protective gas, and calibrate the laser light path through the gun; (2) Set the spraying parameters, set the spraying distance to 50-120mm, the spraying distance is the distance from the bottom end of the gun to the substrate, the laser power is 2.4-4kw, the air knife flow is 20-40L / min, the scanning speed is 100-120mm / s, and the powder feeding amount is 2.0-3.0r / min, and the above process parameters are optimized to obtain a formed coating with research value; (3) Place the substrate under the laser thermal spraying gun according to the set spraying distance, start spraying, and control the scanning times so that the thickness of the coating is in the range of 500-800mm. For example Figure 1 The working schematic diagram of the laser thermal spraying gun is shown in the figure, wherein the orange yellow part simulates the laser path; the F431 powder is fed into the laser beam through the powder feeding channel in the middle, the high-pressure gas fed from the top can form an air knife, which can prevent dust pollution and protect the laser lens; under the action of high-temperature and high-pressure gas flow, the powder passes through the laffer nozzle and fully contacts with the laser heat source, is heated and melted, and forms supersonic liquid droplets which are sprayed out of the nozzle. The gun reciprocates in the horizontal direction to deposit the coating on the surface of the substrate. The process is optimized, and the morphology, hardness and bonding strength of the coating are tested, and the influence of parameter changes on the coating is observed.

[0010] Preferably, the composition of the F431 powder is: C: 0.02%; Mn: 0.28%; Si: 1.09%; Cr: 19.12%; Ni: 1.96%; Fe: balance.

[0011] Preferably, the spraying distance is 100mm.

[0012] Preferably, the laser power is 2.4kW.

[0013] Preferably, the laser power is 3kW or 4kW.

[0014] Preferably, the scanning rate is 100 mm / s.

[0015] Preferably, the scanning rate is 120 mm / s.

[0016] Preferably, the air knife flow rate is 30 L / min.

[0017] Preferably, the air knife flow rate is 40 L / min.

[0018] Preferably, the powder feeding rate is 2.0 r / min, 2.5 r / min, or 3.0 r / min.

[0019] Compared with the prior art, the present invention has the following beneficial effects: This invention integrates thermal spraying and laser cladding technologies into a novel laser thermal spraying technology, which has not yet been extensively researched worldwide. In conventional laser cladding, the working distance between the laser cladding head and the workpiece is short, and coatings cannot be successfully applied to confined areas such as turbine rotors and blade roots. In contrast, the technology described in this invention features an adjustable spraying distance of 20-200mm and a wide-range adjustable spraying angle, allowing for bottom-up spraying, making it suitable for the confined spaces required for water erosion protection and repair of turbine blades. Compared to traditional additive manufacturing technologies, this invention offers a wider range of applications, faster coating production efficiency, simpler operation, and suitability for various working environments.

[0020] This invention explores and studies the process of laser thermal spraying technology, verifying its feasibility. Using a basic stainless steel alloy as the substrate and iron-based powder as the cladding material, fundamental research was conducted on the laser thermal spraying process, providing experimental basis for the subsequent optimization and development of laser thermal spraying technology. Attached Figure Description

[0021] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention. Figure 1 This is a schematic diagram illustrating the operation of the laser thermal spraying technology of the present invention; Figure 2 These are coating morphology diagrams for embodiments 1-8 of the present invention; Figure 3The images are SEM images of the tissue morphology of the fourth coating in the embodiments of the present invention, (a) SEM-200x, (b) SEM-2000x; Figure 4 These are coating morphology diagrams for comparative examples 1-4 of the present invention.

[0022] Among them, 1. spray gun movement direction; 2. protective gas; 3. powder path; 4. laser path; 5. substrate. Detailed Implementation

[0023] The present invention will be further described below with reference to specific embodiments, and the advantages and features of the present invention will become clearer with the description. However, the embodiments are merely exemplary and do not constitute any limitation on the scope of the present invention. Those skilled in the art should understand that modifications or substitutions can be made to the details and form of the technical solutions of the present invention without departing from the spirit and scope of the present invention, but all such modifications and substitutions fall within the protection scope of the present invention.

[0024] Example A method for preparing an F431 coating using laser thermal spraying technology, employing a novel laser thermal spraying gun as described in patent application number CN202510827464.8, wherein the F431 powder composition is as follows: C: 0.02%; Mn: 0.28%; Si: 1.09%; Cr: 19.12%; Ni: 1.96%; Fe: balance.

[0025] Process flow as follows Figure 1 As shown, the steps include: An F431 coating was prepared on a 10mm thick 304 stainless steel substrate using laser thermal spraying technology. The equipment used included an MFSC-6000 laser, a six-axis robot, an RC-PGD-2 powder feeder, and a robot controller. Multiple parallel control experiments (numbered 1-8) were conducted at a distance of approximately 100mm from the nozzle, preparing single-pass coatings approximately 20mm wide. The number of scans was controlled to maintain a coating thickness within the range of 500-800mm. Specific process parameters are shown in Table 1. The morphology of the coating is as follows. Figure 2 As shown.

[0026] Table 1. Coating preparation process parameters (100mm)

[0027] The fourth item with the better coating morphology in the examples was selected for morphology and performance testing.

[0028] On a stainless steel substrate with a diameter of 25.4 mm, the number of scans was controlled at 15, with other parameters the same as in item 4, and the coating thickness between 200-300 mm. The coating adhesion strength was tested using a universal testing machine according to the national standard GB / T 8642-2002.

[0029] Coating morphology The prepared coating was cut to obtain its cross-section, and its morphology was observed under a scanning electron microscope. The results are as follows: Figure 3 As shown, (a) is SEM-200x and (b) is SEM-2000x.

[0030] The prepared coating exhibits obvious characteristics of thermal spraying, with layered deposition and mechanical bonding between the interfaces.

[0031] Coating performance The substrate and the coating prepared by laser thermal spraying were tested using a micro Vickers hardness tester, and the results are shown in Table 2.

[0032] Table 2. Comparison of hardness between the substrate and the coating prepared by laser thermal spraying

[0033] Tests revealed that the hardness of the sample was significantly improved after coating preparation compared to the substrate.

[0034] Tensile tests were performed on the prepared samples, and the bond strength of the samples is shown in Table 3. The tests revealed that the coating exhibited high bond strength.

[0035] Table 3. Coating Bond Strength

[0036] Comparative Example Table 4 shows the process parameters set after increasing the spraying distance to 150mm.

[0037] Table 4. Process parameters for a comparative example with a spraying distance of 150mm.

[0038] Figure 4 The coating morphology was shown after increasing the spraying distance to 150 mm. At this spraying distance, the coating deposition efficiency was low, and the coating thickness was only about one-third of that at the same number of spray passes.

Claims

1. A method for preparing an F431 coating using laser thermal spraying technology, characterized in that, Includes the following steps: (1) Assemble the laser thermal spray gun, connect it to the laser, and connect it to the six-axis robot through the adapter plate; turn on the cooling system of the laser and turn on the power of the laser; the laser used in the experiment is the MFSC-6000 model produced by Chuangxin Laser; turn on the protective gas and calibrate the laser beam path through the spray gun. (2) Set the spraying parameters. Set the process parameters that affect the morphology and performance of the coating. Set the spraying distance to 50-120mm, where the spraying distance is the distance between the bottom of the spray gun and the substrate. Set the laser power to 2.4-4kw, the air knife flow rate to 20-40L / min, the scanning rate to 100-120mm / s, and the powder feed rate to 2.0-3.0r / min. (3) Place the substrate under the laser thermal spray gun at the set spraying distance, start spraying, and control the number of scans to keep the coating thickness within the range of 500-800mm.

2. The method according to claim 1, characterized in that, The powder used in the F431 coating comprises the following components by mass fraction: C: 0.02%; Mn: 0.28%; Si: 1.09%; Cr: 19.12%; Ni: 1.96%; Fe: balance.

3. The method according to claim 1, characterized in that, The spraying distance is 100mm.

4. The method according to claim 1, characterized in that, The laser power is 2.4kW.

5. The method according to claim 1, characterized in that, The laser power is 3kW or 4kW.

6. The method according to claim 1, characterized in that, The scanning rate is 100 mm / s.

7. The method according to claim 1, characterized in that, The scanning rate is 120 mm / s.

8. The method according to claim 1, characterized in that, The air knife flow rate is 30 L / min.

9. The method according to claim 1, characterized in that, The air knife flow rate is 40 L / min.

10. The method according to claim 1, characterized in that, The powder feeding rate is 2.0 r / min, 2.5 r / min, or 3.0 r / min.

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