A method for preparing surface / interface microstructure coating by dual-beam laser synchronization assisted plasma spraying

Abstract

A method for preparing a surface / interface structured coating using dual-beam laser synchronously assisted plasma spraying is disclosed. This invention aims to address the problems of weak bonding strength at heterogeneous interfaces and poor protective effect in thermally sprayed coatings. The method for preparing the surface / interface structured coating involves: 1. Grinding and sandblasting the substrate; 2. Loading ceramic powder into a powder feeding tank; 3. Adding a continuous laser and a pulsed laser. The continuous laser emits a continuous wave laser to preheat the pretreated substrate, followed by thermal spraying using a plasma spraying gun. The pulsed laser emits a pulsed laser for pulsed strengthening, thus preparing the surface / interface structured coating. This invention combines the pretreatment laser treatment of the substrate surface with the pulsed strengthening laser treatment of the sprayed coating surface, achieving simultaneous preheating of the substrate and pulse strengthening treatment of the sprayed coating during plasma spraying, resulting in a high-performance coating with high bonding strength and high density.

Description

Technical Field

[0001] This invention belongs to the field of laser processing and thermal spraying composite technology, specifically relating to a method for preparing surface / interface microstructure coatings by dual-beam laser synchronously assisted plasma spraying. Background Technology

[0002] In the industrial sector, metal components often face harsh service environments such as high temperatures, high pressures, and strong corrosion, resulting in severe surface wear. This not only significantly reduces component performance and leads to component failure but also increases production costs, causing substantial economic losses. Thermal spraying technology, a commonly used surface strengthening and repair technique, effectively solves these surface protection challenges. Its core principle involves melting coating materials with a heat source, atomizing and accelerating them with a high-speed airflow, and then depositing high-performance metal or ceramic materials layer by layer onto the substrate surface. This achieves surface performance enhancement, meeting the corrosion resistance and high-temperature resistance requirements of metal components. Simultaneously, it can repair worn and corroded components, extending their service life, reducing resource consumption, and providing technical support for high-end equipment maintenance and green manufacturing.

[0003] Although thermal spraying technology is widely used in surface protection, two major problems remain. First, insufficient powder melting leads to a porous structure inside and on the surface of the coating. This porous structure severely affects the protective effect of the coating, significantly reducing its wear resistance, corrosion resistance, and ablation resistance. Second, because the interface between the sprayed coating and the substrate is formed by the impact of high-speed particles, it suffers from low bonding strength, high porosity, and significant thermal deformation of the substrate. The mechanical bonding strength between the substrate and the coating is typically only 20MPa to 60MPa, far lower than that of laser cladding (≥300MPa), welding (300MPa to 700MPa), and plasma cladding (350MPa to 500MPa). Under thermal cycling, thermal shock, or alternating loads, plasma-sprayed coatings are prone to peeling and failure due to insufficient adhesion and mismatch in thermal expansion coefficients, thus losing their protective function against the substrate. As mentioned above, coatings prepared by laser cladding, welding, and plasma cladding technologies not only have a dense surface structure but also exhibit good metallurgical bonding with the substrate, mainly due to the metallurgical bonding characteristics of their interfaces. However, laser cladding, welding, and plasma cladding technologies involve extremely high heat input to the substrate during coating preparation, which can easily lead to a decline in the substrate's properties, thus negating the purpose of surface protection.

[0004] Based on the above analysis, while thermal spraying technology boasts advantages such as high efficiency and convenience, it still has certain shortcomings. Laser cladding technology, although able to overcome these shortcomings, suffers from substrate thermal damage. Therefore, in order to efficiently obtain high-performance remanufactured surfaces, it is necessary to adopt certain composite processes based on equipment design. Summary of the Invention

[0005] The present invention aims to solve the problems of weak bonding force at heterogeneous interfaces in thermal spray coatings and poor protective effect caused by porous surface morphology of coatings, and provides a method for preparing surface / interface structure coatings by dual-beam laser synchronous assisted plasma spraying.

[0006] The method for preparing surface / interface microstructure coatings by dual-beam laser synchronous assisted plasma spraying of the present invention is implemented according to the following steps:

[0007] 1. The substrate is ground, ultrasonically cleaned, and then sandblasted to obtain a pretreated substrate;

[0008] 2. Load the ceramic powder into the powder feeding tank of the plasma spraying device;

[0009] 3. A continuous laser and a pulsed laser are installed on the plasma spraying gun, with the plasma spraying gun positioned between the continuous laser and the pulsed laser. The plasma spraying gun, the continuous laser, and the pulsed laser are turned on simultaneously. The continuous laser emits a continuous wave laser to preheat the pretreated substrate. The plasma spraying gun sprays molten (or semi-molten) ceramic powder onto the surface of the pretreated substrate for thermal spraying. The pulsed laser emits a pulsed laser for pulse enhancement, realizing a dual-beam laser synchronously assisted plasma spraying process to prepare a surface / interface microstructure coating.

[0010] In step three, the single-pulse energy of the pulsed laser is controlled to be 20~30J, and the pulse width is 0.5~10ms.

[0011] This invention combines a dual-beam laser device with a plasma spraying device, adding two laser beams that work synchronously with the plasma spraying particle beam. This overcomes the problems of insufficient bonding strength between the coating and the substrate and low production efficiency caused by traditional plasma spraying and subsequent laser remelting post-treatment methods. It combines the preheating treatment, plasma spraying, and laser pulse strengthening processes to achieve integrated operation of dual-beam laser composite plasma spraying.

[0012] Compared with traditional thermal spraying equipment and processes, the method of preparing surface / interface microstructure coatings by dual-beam laser synchronous assisted plasma spraying of the present invention has the following technical advantages:

[0013] (1) The dual-beam laser synchronous assisted plasma spraying coating surface / interface microstructure optimization method of the present invention simultaneously completes the preheating treatment of the substrate surface and the laser pulse strengthening treatment of the sprayed coating while preparing the coating by plasma spraying, which simplifies the process flow, reduces costs and improves production efficiency.

[0014] This invention relates to a method for optimizing the surface / interface microstructure of a dual-beam laser-assisted plasma spraying coating. A continuous laser precisely preheats the surface of the substrate to be sprayed, melting the surface layer and removing the passivation layer, thereby improving the metallurgical bonding between the sprayed particles and the substrate surface. This avoids the problems of uneven heating, component damage, and low cladding efficiency that can occur with traditional heating methods such as flame heating.

[0015] The present invention discloses a method for preparing surface / interface microstructure coatings by dual-beam laser synchronous assisted plasma spraying. The method utilizes a pulsed laser to perform laser pulse strengthening treatment on the surface of the sprayed coating. At the instant the particle beam spraying is completed, a laser pulse strengthening treatment is applied to the surface of the sprayed coating by a laser remelting post-treatment pulsed laser, causing the surface of the sprayed coating to undergo controllable rapid melting and solidification. This laser pulse strengthening treatment significantly improves the microstructure and overall service performance of the sprayed coating.

[0016] (2) This invention achieves precise local heating of the workpiece using a high-energy laser beam, eliminating the need for overall workpiece heating. It offers significant advantages in temperature control accuracy, substrate protection, and coating quality stability, making it particularly suitable for high-precision, high-performance coating preparation. The laser beam can be precisely focused on the critical service area of ​​the workpiece, achieving localized strengthening while maintaining the original substrate state in non-critical areas. This avoids substrate deformation or performance degradation caused by overall remelting, making it especially suitable for coating preparation of irregularly shaped and precision parts, without strict limitations on the shape and size of the workpiece.

[0017] (3) The present invention uses high-energy laser beam heating. Unlike flame remelting and arc remelting, the laser beam does not require gas or electrodes. No smoke or harmful gases are generated during the process, which meets the process requirements of green manufacturing. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of a method for optimizing the surface / interface microstructure of a coating using a dual-beam laser synchronously assisted plasma spraying system, as per the present invention. In the diagram: 1—substrate; 2—plasma spraying / dual-beam laser composite device; 3—preheating continuous laser; 4—high-energy continuous laser beam; 5—plasma spraying gun; 6—particle beam; 7—laser remelting post-treatment pulsed laser; 8—pulsed laser beam; 9—sprayed coating layer; 10—preheating hot spot; 11—laser pulse strengthening point; 12—cooled coating layer.

[0019] Figure 2 This is a schematic diagram of the morphology of the coating obtained by optimizing the surface / interface microstructure of the coating through a dual-beam laser synchronously assisted plasma spraying method. Detailed Implementation

[0020] Specific Implementation Method 1: This implementation method for preparing surface / interface microstructure coatings using dual-beam laser synchronous assisted plasma spraying is carried out according to the following steps:

[0021] 1. The substrate is ground, ultrasonically cleaned, and then sandblasted to obtain a pretreated substrate;

[0022] 2. Load the ceramic powder into the powder feeding tank of the plasma spraying device;

[0023] 3. A continuous laser and a pulsed laser are installed on the plasma spraying gun, with the plasma spraying gun positioned between the continuous laser and the pulsed laser. The plasma spraying gun, the continuous laser, and the pulsed laser are turned on simultaneously. The continuous laser emits a continuous wave laser to preheat the pretreated substrate. The plasma spraying gun sprays molten (or semi-molten) ceramic powder onto the surface of the pretreated substrate for thermal spraying. The pulsed laser emits a pulsed laser for pulse enhancement, realizing a dual-beam laser synchronously assisted plasma spraying process to prepare a surface / interface microstructure coating.

[0024] In step three, the single-pulse energy of the pulsed laser is controlled to be 20~30J, and the pulse width is 0.5~10ms.

[0025] The pulsed laser described in step three of this embodiment is a quasi-continuous long-pulse fiber laser, which emits millisecond-level quasi-continuous laser; the average output power is adjustable from 1000 W to 3000 W, and the single pulse energy is 20 J to 30 J; the pulse width of the quasi-continuous long-pulse fiber laser is adjustable from 0.5 ms to 10 ms, and the laser repetition frequency is adjustable from 50 Hz to 100 Hz.

[0026] The method for preparing a surface / interface microstructure coating by dual-beam laser synchronous assisted plasma spraying as described in this embodiment includes a preheating laser beam system located directly above the substrate (base) and used to preheat the surface of the substrate to be sprayed; a remelting laser beam system used to perform laser pulse enhancement treatment on the sprayed coating; and a plasma spraying gun system. The preheating laser beam system includes a preheating continuous laser for preheating the substrate surface with a high-energy laser beam; the remelting laser beam system includes a laser remelting post-treatment pulsed laser for performing laser pulse enhancement treatment on the sprayed coating with a pulsed laser beam.

[0027] The preheating continuous laser, the plasma spraying gun system, and the laser remelting post-treatment pulsed laser are arranged in parallel along the equipment running direction at a preset interval and a preset angle, and move together at the same speed along the running direction; the substrate to be sprayed is fixed on the machine tool by a clamping device.

[0028] The preheating continuous laser is used to emit a continuous laser beam onto the substrate surface. The continuous laser beam irradiates the substrate surface before plasma spraying particle beam deposition. The high-energy laser beam melts a certain thickness of the substrate surface layer, removes the passivation layer within the preheating hot spot range of the substrate surface, and enhances the metallurgical bonding effect between the sprayed particles and the substrate surface by melting the substrate surface layer.

[0029] The plasma spraying gun device is used to generate a spraying particle beam required for spraying and depositing a coating. The spraying particle beam is in a molten or semi-molten state and is sprayed onto the substrate surface via the spray gun.

[0030] The laser remelting post-processing pulsed laser is used to perform laser pulse strengthening treatment on the surface of the sprayed coating. At the instant that the particle beam spraying is completed, the surface of the sprayed coating is strengthened by the pulsed laser beam, so that the surface of the sprayed coating undergoes controllable rapid melting and solidification. This laser pulse strengthening treatment significantly improves the microstructure and overall service performance of the sprayed coating.

[0031] In this embodiment of the method for preparing surface / interface microstructure coatings using dual-beam laser synchronous assisted plasma spraying, the preheating laser beam system melts a substrate surface layer of a certain thickness using a high-energy laser beam. The continuous-wave laser emitted by the continuous laser is controlled to preheat the substrate at a temperature 10-20°C higher than the substrate's melting point, removing the passivation layer within the preheating hotspot area on the substrate surface. Melting the substrate surface layer enhances the metallurgical bonding between the sprayed particles and the substrate surface. The remelting laser beam system uses a pulsed laser beam to perform laser pulse strengthening on the sprayed coating surface, significantly improving the microstructure and overall service performance of the coating. This invention combines the pretreatment laser treatment of the substrate surface to be sprayed with the pulsed strengthening laser treatment of the post-sprayed coating surface, achieving simultaneous preheating of the substrate and pulse strengthening treatment of the sprayed coating during plasma spraying, resulting in a high-performance coating with high bonding strength and high density.

[0032] This embodiment describes a method for preparing surface / interface microstructure coatings using dual-beam laser synchronous assisted plasma spraying, used to obtain thermally sprayed coatings with well-bonded interparticles. The equipment is highly versatile and adaptable to various thermal spraying processes and laser sources of different power, enabling precise control of the coating microstructure. By synchronously controlling the preheating treatment of the substrate surface, thermal spraying deposition, and laser pulse enhancement of the sprayed coating, the interfacial bonding state is effectively improved, pore density is reduced, and the coating density and bonding quality are enhanced.

[0033] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that the material of the substrate in step one is a nickel-based high-temperature alloy, aluminum alloy, zirconium oxide, or chromium oxide.

[0034] Specific Implementation Method 3: This implementation method differs from Specific Implementation Method 1 or 2 in that anhydrous ethanol is used to ultrasonically clean the substrate in step 1.

[0035] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that the ceramic powder material in step two is one or more of the following ceramic powders: Al2O3 ceramic powder, ZrB2 ceramic powder, silicon carbide ceramic powder, and AlN ceramic powder.

[0036] Specific Implementation Method 5: This implementation method differs from Specific Implementation Methods 1 to 4 in that the particle size of the ceramic powder in step 2 is 20 μm ~ 100 μm.

[0037] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in that the ceramic powder in step two is pre-dried.

[0038] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods One to Six in that the spot diameter of the continuous wave laser in step three is controlled to be 3 mm to 6 mm, and the spot diameter of the pulsed laser is controlled to be 3 mm to 10 mm.

[0039] The output beam of the quasi-continuous long-pulse fiber laser after laser remelting in this embodiment is a flat-top beam after beam shaping, and the output spot is circular with an adjustable diameter.

[0040] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Methods One to Seven in that the average output power of the continuous wave laser is controlled to be 500W ~ 3000W in step three.

[0041] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Methods One to Eight in that, in step three, the distance between the continuous wave laser and the plasma spray gun is controlled to be 150 mm to 300 mm, and the distance between the pulsed laser and the plasma spray gun is controlled to be 100 mm to 400 mm.

[0042] Specific Implementation Method 10: This implementation method differs from Specific Implementation Methods 1 to 9 in that the thickness of the surface / interface structure coating obtained in step 3 is 0.2 mm to 0.6 mm.

[0043] Example: This example describes a method for preparing a surface / interface microstructure coating using dual-beam laser synchronous assisted plasma spraying, implemented according to the following steps:

[0044] 1. Grind the aluminum alloy substrate with #300 sandpaper for 5 minutes, then immerse it in anhydrous ethanol and ultrasonically clean it with a power of 150W for 10 minutes. After sandblasting, the pretreated substrate is obtained.

[0045] 2. The ceramic powder is dried at 80℃ and sieved to obtain zirconium boride-silicon carbide ceramic composite powder with a particle size of 45 μm ~ 70 μm, which is then loaded into the powder feeding tank of the plasma spraying device.

[0046] 3. A continuous laser and a pulsed laser are installed on the plasma spraying gun, with the plasma spraying gun positioned between the continuous laser and the pulsed laser. The plasma spraying gun, the continuous laser, and the pulsed laser are turned on simultaneously. Under the protection of local argon gas, the continuous laser emits a continuous wave laser to preheat the substrate. The preheating temperature is 10 °C higher than the melting point of the aluminum alloy substrate. The plasma spraying gun sprays molten ceramic powder onto the pretreated substrate for thermal spraying. The pulsed laser emits a pulsed laser for pulse enhancement. The single pulse energy of the pulsed laser is controlled to be 30 J and the pulse width is 2 ms, realizing a dual-beam laser synchronously assisted plasma spraying process to prepare a surface / interface microstructure coating.

[0047] In step two of this embodiment, the ceramic powder is a mixture of ZrB2 ultrafine powder and SiC ultrafine powder in a mass ratio of 7:3.

[0048] In this embodiment, the substrate 1 is fixed to the substrate clamping device, and the plasma spraying / dual-beam laser composite device 2 is fixed to the robotic arm. The position of the plasma spraying / dual-beam laser composite device 2 is adjusted by the robotic arm to make it parallel to the substrate surface, ensuring that the plasma spraying gun 5, the preheating continuous laser 3, and the laser remelting post-treatment pulsed laser 7 face the substrate surface and run along a path parallel to the substrate surface, maintaining a constant spacing to achieve uniform coating deposition. The continuous laser 3 emits a high-energy continuous laser beam 4, and the pulsed laser 7 emits a pulsed laser beam 8. The preset spacing, preset angle, and distance between the plasma spraying gun 5, the preheating continuous laser 3, and the laser remelting post-treatment pulsed laser 7 and the substrate 1 surface are adjusted. The preset spacing includes the distance between the laser and the plasma spraying gun; the preset angle includes the angle between the laser and the plasma spraying gun. The adjustment of the preset spacing and preset angle should meet the following requirements: the spacing between the preheating laser preheating point 10, the spraying point, and the laser pulse strengthening point 11 should be appropriate; the spacing between the laser pulse strengthening point on the sprayed coating surface of the high-energy laser beam 8 emitted by the laser remelting post-treatment pulse laser 7 and the spraying point on the substrate surface of the particle beam 6 emitted by the plasma spraying gun 5 should be appropriate. This will prevent the rapid decay of the substrate surface temperature after preheating, which could lead to new oxidation and contamination, and ensure that the substrate surface is in an activated state, thereby improving the metallurgical bonding strength between the coating and the substrate surface. At the same time, the coating surface after deposition should be immediately subjected to laser pulse strengthening before it is completely cooled, making full use of the residual heat from deposition, reducing external energy input, and obtaining a high-quality coating with uniform structure, high density, and few defects.

[0049] After the surface / interface microstructure coating of this embodiment was prepared, its hardness was measured using a Vickers hardness tester, and the bonding strength of the coating was further tested using a tensile testing machine. Table 1 shows the test results of the microhardness and bonding strength of the prepared ZrB2-SiC coating.

[0050] Table 1

[0051]

[0052] Figure 2 This is a schematic diagram of the coating morphology prepared by a dual-beam laser-assisted plasma spraying method for optimizing the surface / interface microstructure. The bottom green area represents the molybdenum alloy substrate, the upper blue main body represents the ZrB2-SiC coating structure, the gradient region between the coating structure and the substrate represents the metallurgical bonding region after surface laser pretreatment, and the coating surface layer is a dense protective layer after pulse strengthening.

[0053] As shown in the figure, the interface between the coating and the substrate exhibits a continuous, crack-free, and tightly bonded state with no penetrating gaps, indicating excellent bonding reliability between the coating and the substrate. The top of the coating is flat, without obvious unmelted particles or a loose layer. The interior of the coating contains only a small number of diffusely distributed micropores, with no interconnected macropores. This indicates that laser pulse strengthening significantly eliminates the porous defects of the sprayed surface, forming a dense modified layer and achieving uniform strengthening of the entire coating, thus solving the problem of poor protective effect caused by surface porosity in traditional coatings. As shown in Table 1, the ZrB2-SiC coating prepared by the dual-beam laser synchronous assisted plasma spraying coating surface / interface microstructure optimization method exhibits excellent microhardness and bonding strength, reaching 30 GPa and 44 MPa, which are far higher than the microhardness (≤18 GPa) and bonding strength (≤20 MPa) of ZrB2-SiC coatings prepared by traditional thermal spraying methods.

[0054] In summary, this invention provides a method for optimizing the surface / interface microstructure of a dual-beam laser-assisted plasma spraying coating, aiming to solve the problems of unreliable mechanical bonding interfaces and poor protective effects caused by porous surface morphology in thermal spraying coatings. By combining a dual-beam laser device and a plasma spraying device, this invention achieves simultaneous preheating of the substrate and pulse strengthening treatment of the sprayed coating during plasma spraying. This invention enables the efficient preparation of high-performance coatings with high bonding strength and high density, effectively solving the problems of insufficient bonding strength, low production efficiency, and easy failure inherent in traditional thermal spraying coatings. Simultaneously, it avoids the drawback of excessive heat input to the substrate in laser cladding technology, and efficiently prepares high-performance surface protective coatings through a composite process, meeting the high-end demands of industrial sectors for surface protection of metal components.

Claims

1. A method for preparing a surface / interface microstructure coating by dual-beam laser synchronous assisted plasma spraying, characterized in that... The method for preparing surface / interface microstructure coatings by dual-beam laser synchronous assisted plasma spraying is implemented according to the following steps:

1. The substrate is ground, ultrasonically cleaned, and then sandblasted to obtain a pretreated substrate; 2. Load the ceramic powder into the powder feeding tank of the plasma spraying device; 3. A continuous laser and a pulsed laser are installed on the plasma spraying gun, with the plasma spraying gun positioned between the continuous laser and the pulsed laser. The plasma spraying gun, the continuous laser, and the pulsed laser are turned on simultaneously. The continuous laser emits a continuous wave laser to preheat the pretreated substrate. The plasma spraying gun sprays molten ceramic powder onto the surface of the pretreated substrate for thermal spraying. The pulsed laser emits a pulsed laser for pulse enhancement, realizing a dual-beam laser synchronously assisted plasma spraying process to prepare a surface / interface microstructure coating. In step three, the single-pulse energy of the pulsed laser is controlled to be 20~30J, and the pulse width is 0.5~10ms.

2. The method for preparing a surface / interface microstructure coating by dual-beam laser synchronous assisted plasma spraying according to claim 1, characterized in that... The substrate material in step one is a nickel-based superalloy, aluminum alloy, zirconium oxide, or chromium oxide.

3. The method for preparing a surface / interface microstructure coating by dual-beam laser synchronous assisted plasma spraying according to claim 1, characterized in that... In step one, the substrate is ultrasonically cleaned using anhydrous ethanol.

4. The method for preparing a surface / interface microstructure coating by dual-beam laser synchronous assisted plasma spraying according to claim 1, characterized in that... In step two, the ceramic powder material is one or a mixture of multiple types of ceramic powder, including Al2O3 ceramic powder, ZrB2 ceramic powder, silicon carbide ceramic powder, and AlN ceramic powder.

5. The method for preparing a surface / interface microstructure coating by dual-beam laser synchronous assisted plasma spraying according to claim 1, characterized in that... In step two, the particle size of the ceramic powder is 20 μm ~ 100 μm.

6. The method for preparing a surface / interface microstructure coating by dual-beam laser synchronous assisted plasma spraying according to claim 1, characterized in that... In step two, the ceramic powder is pre-dried.

7. The method for preparing a surface / interface microstructure coating by dual-beam laser synchronous assisted plasma spraying according to claim 1, characterized in that... In step three, the spot diameter of the continuous wave laser is controlled to be 3 mm to 6 mm, and the spot diameter of the pulsed laser is controlled to be 3 mm to 10 mm.

8. The method for preparing a surface / interface microstructure coating by dual-beam laser synchronous assisted plasma spraying according to claim 1, characterized in that... In step three, the average output power of the continuous wave laser is controlled to be 500W ~ 3000W.

9. The method for preparing a surface / interface microstructure coating by dual-beam laser synchronous assisted plasma spraying according to claim 1, characterized in that... In step three, the distance between the continuous wave laser and the plasma spray gun is controlled to be 150 mm to 300 mm, and the distance between the pulsed laser and the plasma spray gun is controlled to be 100 mm to 400 mm.

10. The method for preparing a surface / interface microstructure coating by dual-beam laser synchronous assisted plasma spraying according to claim 1, characterized in that... The thickness of the surface / interface microstructure coating obtained in step three is 0.2 mm to 0.6 mm.

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