A laser thermal spray gun

Abstract

This invention discloses a laser thermal spraying gun, belonging to the field of laser additive manufacturing technology. It includes a connecting base, an air knife assembly, an inner nozzle, an outer nozzle, a cooling jacket cover, and a cooling jacket tube. The outer nozzle includes a powder feeding body and a Laval tube. The Laval tube has diffusion holes inside. The Laval nozzle accelerates the airflow through a tapered-expanding structure, forming a high-speed, high-temperature jet environment. This ensures the powder is fully preheated and uniformly dispersed before reaching the substrate. Combining the Laval tube with laser spraying combines the advantages of laser cladding and thermal spraying technologies. The accelerated effect of the Laval airflow, under high temperature and high pressure, allows the powder to fully contact the laser heat source over a sufficiently long flight distance through the Laval nozzle. This enables the powder to form a metallurgical bond with the substrate in a molten state, achieving a bonding strength 2-3 times that of traditional thermal spraying. This method is suitable for confined spaces used in the protection and repair of turbine blades from water erosion.

Description

Technical Field

[0001] This invention relates to the fields of laser additive manufacturing, laser cladding and laser thermal spraying, and particularly to a laser thermal spraying gun. Background Technology

[0002] A steam turbine, also known as a steam engine, is a rotary steam power unit. High-temperature, high-pressure steam passes through a fixed nozzle, becomes an accelerated airflow, and is then injected onto the blades, causing the rotor, which is equipped with rows of blades, to rotate and perform work. Steam turbines are the main equipment in modern thermal power plants and are also used in the metallurgical industry, chemical industry, and ship propulsion systems. Electric and nuclear power steam turbines contain a large amount of wet steam. This wet steam flows in two phases, and the presence of condensed moisture not only affects aerodynamic efficiency but also leads to blade corrosion. Corrosion damage causes material loss and changes in blade shape, resulting in decreased stage efficiency. In severe cases, it can even lead to blade breakage and major operational accidents. To address the corrosion and failure problems of steam turbines, surface modification technology is a very effective method.

[0003] Surface modification technology is widely used in the manufacturing industry. It employs various methods, such as surface treatment, surface coatings or films, and surface modification techniques, to endow the surface of materials or workpieces with specific properties, achieving an optimal combination between the surface and core materials. This technology can economically and effectively improve product quality and extend service life. Common surface modification technologies include thermal spraying and laser cladding. However, in actual production processes, the application of these technologies still faces some challenges.

[0004] Thermal spraying technology is simple to operate, has a fast deposition rate, and is highly adaptable to materials. However, the coating prepared by thermal spraying is mechanically bonded to the substrate, resulting in low coating strength and the formation of defects such as voids within the coating. Under harsh operating conditions, its service life may not meet requirements.

[0005] In traditional laser cladding processes, the distance between the lower end face of the cladding head and the workpiece surface (referred to as the working distance) is too short (generally only a few millimeters to tens of millimeters), resulting in excessive laser heat input and easily causing significant workpiece deformation. When operating in confined spaces such as the roots of thin-walled components like turbine blades, high-temperature aero-engines, and gas turbine blades, the reachability of the laser head is poor. When minimal deformation is required, and strengthening or remanufacturing is necessary, traditional laser cladding technology (including high-speed laser cladding technology) is almost powerless. Summary of the Invention

[0006] This invention provides a laser thermal spraying gun, aiming to solve the problems of the short working distance between the laser cladding head and the workpiece in ordinary laser cladding, and the large physical size of the laser cladding head itself, which makes it impossible to successfully prepare coatings in narrow areas such as turbine rotors and blade roots. By combining laser cladding technology with thermal spraying technology, it integrates the advantages of thermal spraying technology, such as long working distance and high accessibility to narrow areas, while taking into account the advantages of laser cladding technology, which can form a metallurgical bond between the prepared coating and the substrate, resulting in a coating with high bonding strength and resistance to peeling.

[0007] The specific technical solution provided by this invention is as follows:

[0008] This invention provides a laser thermal spraying gun, comprising a connecting base, an air knife assembly fixed to the connecting base, an inner nozzle fixed to the air knife assembly, an outer nozzle fixed to the inner nozzle, a cooling jacket cover plate fixed to the lower end of the outer nozzle, and a cooling sleeve fixed to the outer nozzle. A powder feeding channel is formed between the outer nozzle and the inner nozzle. The inner nozzle contains a laser beam cavity with an inverted conical structure. The outer nozzle includes a powder feeding body that cooperates with the inner nozzle to form the powder feeding channel, and a Laval tube located below the powder feeding body. A diffusion hole is provided inside the Laval tube, communicating with both the powder feeding channel and the laser beam cavity. The convergence point of the center line of the powder feeding channel and the center line of the laser beam cavity is located inside the diffusion hole, with the smaller diameter end of the diffusion hole close to the powder feeding body.

[0009] Optionally, the diameter of the larger end of the diffusion hole is 1.5 to 3 times the diameter of the smaller end of the diffusion hole, and the length of the diffusion hole is 20 mm to 200 mm.

[0010] Optionally, the diameter of the larger end of the diffusion hole is twice the diameter of the smaller end of the diffusion hole, and the length of the diffusion hole is 130mm~160mm.

[0011] Optionally, the center line of the powder feeding channel and the center line of the laser beam cavity converge at the same point on the central axis of the diffuser hole, and the laser beam cavity and the diffuser hole are coaxially arranged.

[0012] Optionally, the laser beam cavity has an inverted conical structure with a taper of 50:88 to 65:88, and the powder feeding channels are evenly distributed around the annular periphery of the laser beam cavity.

[0013] Optionally, the annular space formed by splicing the cooling sleeve and the Laval tube is a cooling channel, and the powder feeding body and the Laval tube are integrally formed.

[0014] Optionally, the air knife assembly includes an upper air knife and a lower air knife that are spliced ​​together, and the air knife assembly is located above the laser beam cavity.

[0015] Optionally, the powder feeding channel is a slit-type powder feeding channel, and the convergence point of the longitudinal section centerline of the slit-type powder feeding channel and the longitudinal section centerline of the laser beam cavity is both on the central axis of the diffuser hole.

[0016] Optionally, the angle between the center line of the longitudinal section of the slit-type powder feeding channel and the center line of the longitudinal section of the laser beam cavity is 32°~40°.

[0017] Optionally, the small end diameter of the laser beam cavity is 6~8mm, and the small end diameter of the diffusion hole is 8~10mm.

[0018] The beneficial effects of this invention are as follows:

[0019] This invention provides a laser thermal spraying gun comprising a connecting base, an air knife assembly fixed to the connecting base, an inner nozzle fixed to the air knife assembly, an outer nozzle fixed to the inner nozzle, a cooling jacket cover plate fixed to the lower end of the outer nozzle, and a cooling sleeve fixed to the outer nozzle. The outer nozzle includes a powder feeding body that cooperates with the inner nozzle to form the powder feeding channel, and a Laval tube located below the powder feeding body. The Laval tube has a diffusion hole inside, which communicates with the powder feeding channel and the laser beam cavity. The convergence point of the center line of the powder feeding channel and the center line of the laser beam cavity is located inside the diffusion hole. The smaller diameter end of the diffusion hole is near... The Laval nozzle, near the powder delivery body, accelerates the airflow through a tapered-expanding structure, creating a high-speed, high-temperature jet environment. This ensures the powder is fully preheated and uniformly dispersed before reaching the substrate. Combining the Laval tube with laser spraying combines the advantages of laser cladding and thermal spraying technologies. Laser cladding has high energy density, which, combined with the acceleration effect of the Laval airflow, allows the powder to fully contact the laser heat source over a sufficiently long flight distance under high temperature and high pressure. This enables the powder to form a metallurgical bond with the substrate in a molten state, achieving a bonding strength 2 to 3 times that of traditional thermal spraying. This method is suitable for confined spaces used in the protection and repair of turbine blades from water erosion. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1This is a schematic diagram of the structure of a laser thermal spray gun according to an embodiment of the present invention;

[0022] Figure 2 This is a schematic diagram of the equiaxed side structure of a laser thermal spray gun according to an embodiment of the present invention;

[0023] Figure 3 This is a schematic diagram of the structure of an upper air knife according to an embodiment of the present invention. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0025] The following will combine Figures 1-3 A laser thermal spray gun according to an embodiment of the present invention will be described in detail.

[0026] refer to Figure 1 , Figure 2 and Figure 3 As shown, an embodiment of the present invention provides a laser thermal spraying gun including a connecting seat 1, an air knife assembly 2 fixed on the connecting seat 1, an inner nozzle 3 fixed on the air knife assembly 2, an outer nozzle 4 fixed on the inner nozzle 3, a cooling sleeve cover plate 5 fixed at the lower end of the outer nozzle 4, and a cooling sleeve 6 fixed on the outer nozzle 4. The connecting seat 1 is used to fix the laser thermal spraying gun of the present invention to other components. For example, the laser thermal spraying gun of the present invention is fixed to a laser cladding device or a laser spraying device through the connecting seat 1.

[0027] refer to Figure 1 , Figure 2 and Figure 3As shown, a powder feeding channel 7 is formed between the outer nozzle 4 and the inner nozzle 3. Specifically, the powder feeding channel 7 is located at the junction of the outer nozzle 4 and the inner nozzle 3. The powder feeding channel 7 is a slit-type channel. The convergence point of the center line of the longitudinal section of the slit-type powder feeding channel and the center line of the longitudinal section of the laser beam cavity 8 is both on the central axis of the diffuser hole 9. Using a slit-type powder feeding channel ensures that the powder ejected through the channel converges in the direction of the laser beam cavity 8, thereby forming a coating with uniform thickness and excellent surface quality on the substrate surface. The inner nozzle 3 contains a laser beam cavity 8 with an inverted conical structure. The laser beam cavity 8 has an inverted conical cylinder structure with a taper of 50:88 to 65:88. The powder feeding channel 7 is evenly distributed around the circumference of the laser beam cavity 8. The centerline of the cross-section of the powder feeding channel 7 and the centerline of the cross-section of the laser beam cavity 8 converge at the same point on the central axis of the diffuser hole 9. The laser beam cavity 8 and the diffuser hole 9 are coaxially arranged, that is, the intersection of the central axis of all powder feeding channels 7 and the central axis of the laser beam cavity forms a disc-shaped structure in the same horizontal plane. This allows the powder to be coated at the convergence point of the laser beam in the laser beam cavity. The powder disc formed at the outlet of the powder feeding cavity has a certain diameter, which allows it to converge with the laser beam above the diffuser hole 9. This ensures that the laser beam contacts the powder disc before reaching the diffuser hole 9, guaranteeing that most of the energy of the laser beam entering the diffuser hole is used to heat and melt and accelerate the powder particles in flight. This avoids the substrate being overheated, which would significantly reduce the dilution rate. It also reduces the substrate deformation and dilution rate, which can greatly improve powder utilization and processing efficiency. This ensures that the effective components of the coating are not affected by the substrate material, thereby improving the corrosion resistance and wear resistance of the coating.

[0028] refer to Figure 1 , Figure 2 and Figure 3 As shown, the outer nozzle 4 includes a powder feeding body 41 that cooperates with the inner nozzle 3 to form a powder feeding channel 7, and a Laval tube 42 located below the powder feeding body 41. The interior of the Laval tube 42 is configured as a diffusion hole 9, which is connected to the powder feeding channel 7 and the laser beam cavity 8. The convergence point of the cross-sectional center line of the powder feeding channel 7 and the cross-sectional center line of the laser beam cavity 8 is located inside the diffusion hole 9. Furthermore, the cross-sectional center line of the powder feeding channel 7 and the cross-sectional center line of the laser beam cavity 8 converge at the same point on the central axis of the diffusion hole 9. That is, the cross-sectional center line of the powder feeding channel 7 and the cross-sectional center line of the laser beam cavity 8 converge on the central axis of the diffusion hole 9. Thus, most of the energy of the laser beam entering the diffusion hole is used to heat and melt and accelerate the powder particles in flight, avoiding the substrate from being overheated and significantly reducing the dilution rate. This reduces the substrate deformation and dilution rate, which can greatly improve the powder utilization rate and processing efficiency, and ensure that the effective components of the coating are not affected by the substrate material, thereby improving the corrosion resistance and wear resistance of the coating.

[0029] refer to Figure 1 , Figure 2 and Figure 3 As shown, the smaller diameter end of the diffuser hole 9 is close to the powder feeding body 41, ensuring that the powder particles entering through the powder feeding channel are fully mixed with the laser beam inside the diffuser hole before entering the Laval tube. The larger diameter of the diffuser hole 9 is 1.5 to 3 times the smaller diameter, and the length of the diffuser hole 9 is 20 mm to 200 mm. The powder particles entering the diffuser hole 9 form a Venturi effect inside the diffuser hole, accelerating the airflow and uniformly dispersing the powder, thereby improving the coating coverage efficiency.

[0030] In this embodiment of the invention, powder particles are fed into the laser beam through the central powder feeding channel 7, superimposed with high-pressure gas fed from the left (forming an air knife to prevent dust and other contaminants from polluting the laser protective lens). Under the action of high temperature and high pressure airflow, the powder particles pass through a Laval nozzle (diffuser hole 9) and make full contact with the laser heat source over a sufficiently long flight distance. This combines laser and thermal spraying technologies. Under the action of the Laval tube, the powder particles are further accelerated to form supersonic droplets that are ejected from the nozzle, gradually accumulating to form a coating on the workpiece surface 20-200 mm from the exit. By optimizing process parameters such as different laser power and scanning speed, the substrate can be partially melted, thereby flexibly controlling the metallurgical bond between the coating and the substrate. By controlling the heat input, the deformation of the substrate can be controlled within a reasonable range. This combines the advantages of laser cladding technology and thermal spraying technology, and can be widely used in the coating preparation of complex structural components such as turbine blades.

[0031] Furthermore, in this embodiment of the invention, the large end diameter of the diffuser hole 9 is twice the small end diameter, and the length of the diffuser hole 9 is 130mm~160mm. This setting ensures that the diffuser hole 9 forms a good Venturi effect, and then the powder is fed into the laser beam through the central powder feeding channel 7. The high-pressure gas fed from the left is superimposed (forming an air knife to prevent dust and other contaminants from contaminating the laser protective lens). Under the action of high temperature and high pressure airflow, the powder particles are further accelerated by the Venturi effect of the diffuser hole 9, and fully contact the laser heat source at a sufficiently long flight distance. The laser and thermal spraying technology are combined. Under the action of the Venturi effect of the Laval tube, the powder particles are further accelerated to form supersonic droplets that are ejected from the nozzle. A uniform and reliable metallurgical bonding coating is gradually accumulated on the workpiece surface 20-200 mm away from the exit.

[0032] refer to Figure 1 , Figure 2 and Figure 3As shown, the annular space formed by the interlocking of the cooling sleeve 6 and the Laval tube 42 is the cooling channel 10. The powder feeding body 41 and the Laval tube 42 are integrally formed. The cooling channel 10 is filled with a low-temperature coolant (such as a water-glycol mixture) to remove the heat generated by the reaction between the high-temperature laser and the powder particles, preventing the nozzle and Laval tube 42 from being ablated due to excessive temperature. The air knife assembly 2 includes an upper air knife and a lower air knife that are interlocked. The air knife assembly 2 is located above the laser beam cavity 8. It forms a laminar airflow by compressing air to stabilize the powder delivery path and prevent powder entering the powder feeding channel from forming dust and contaminating the laser protective lens, such as... Figure 3 As shown, the upper and lower air knives have the same structure. When the upper and lower air knives are used together, the resulting laminar airflow is more stable and reliable, and has a better blocking effect on the dust formed by the powder entering the powder feeding channel. This can better prevent the powder entering the powder feeding channel from forming dust and other contaminants that pollute the laser protective lens.

[0033] refer to Figure 1 , Figure 2 , Figure 3 As shown, the angle between the centerline of the longitudinal section of the slit-type powder feeding channel and the centerline of the longitudinal section of the laser beam cavity is 32°~40°. The small end diameter of the laser beam cavity is 6~8mm, and the small end diameter of the diffuser hole is 8~10mm. Under this angle, the interaction time between the laser beam and the powder cake is the longest, the powder utilization rate is the highest, the laser utilization rate is the highest, and the metallurgical bonding strength of the coating is the highest. Moreover, combined with the Venturi effect of the Laval tube below, it can fully contact the laser heat source over a sufficiently long flight distance. Under the premise of balancing laser cladding and particle powder acceleration, it can fully realize the acceleration of powder particles and the melting to form supersonic droplets that are ejected from the nozzle. On the workpiece surface 20-200 mm away from the exit, a uniform and reliable metallurgical bonding coating is gradually accumulated.

[0034] This invention provides a laser thermal spraying gun comprising a connecting base, an air knife assembly fixed to the connecting base, an inner nozzle fixed to the air knife assembly, an outer nozzle fixed to the inner nozzle, a cooling jacket cover plate fixed to the lower end of the outer nozzle, and a cooling sleeve fixed to the outer nozzle. The outer nozzle includes a powder feeding body that cooperates with the inner nozzle to form the powder feeding channel, and a Laval tube located below the powder feeding body. The Laval tube has a diffusion hole inside, which communicates with the powder feeding channel and the laser beam cavity. The convergence point of the center line of the powder feeding channel and the center line of the laser beam cavity is located inside the diffusion hole. The smaller diameter end of the diffusion hole is near... The Laval nozzle, near the powder delivery body, accelerates the airflow through a tapered-expanding structure, creating a high-speed, high-temperature jet environment. This ensures the powder is fully preheated and uniformly dispersed before reaching the substrate. Combining the Laval tube with laser spraying combines the advantages of laser cladding and thermal spraying technologies. Laser cladding has high energy density, which, combined with the acceleration effect of the Laval airflow, allows the powder to fully contact the laser heat source over a sufficiently long flight distance under high temperature and high pressure. This enables the powder to form a metallurgical bond with the substrate in a molten state, achieving a bonding strength 2 to 3 times that of traditional thermal spraying. This method is suitable for confined spaces used in the protection and repair of turbine blades from water erosion.

[0035] Obviously, those skilled in the art can make various modifications and variations to the embodiments of the present invention without departing from the spirit and scope of the embodiments of the present invention. Thus, if these modifications and variations to the embodiments of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention also intends to include these modifications and variations.

Claims

1. A laser thermal spraying gun, characterized in that, The laser thermal spray gun includes a connecting base, an air knife assembly fixed on the connecting base, an inner nozzle fixed on the air knife assembly, an outer nozzle fixed on the inner nozzle, a cooling jacket cover plate fixed at the lower end of the outer nozzle, and a cooling sleeve fixed on the outer nozzle. A powder feeding channel is formed between the outer nozzle and the inner nozzle. The inner nozzle contains a laser beam cavity with an inverted conical structure. The outer nozzle includes a powder feeding body that cooperates with the inner nozzle to form the powder feeding channel, and a Laval tube located below the powder feeding body. A diffusion hole is provided inside the Laval tube, communicating with both the powder feeding channel and the laser beam cavity. The convergence point of the center line of the powder feeding channel and the center line of the laser beam cavity is located inside the diffusion hole. The smaller diameter end of the diffusion hole is close to the powder feeding body. The distance from the convergence point of the center line of the powder feeding channel and the center line of the laser beam cavity to the larger end face of the diffusion hole is greater than the distance to the smaller end face of the diffusion hole. The diameter of the larger end of the diffusion hole is 1.5 to 3 times the diameter of the smaller end of the diffusion hole, and the length of the diffusion hole is 20 mm to 200 mm. The centerline of the cross-section of the powder feeding channel and the centerline of the cross-section of the laser beam cavity converge at the same point on the central axis of the diffuser hole. The laser beam cavity and the diffuser hole are coaxially arranged. The powder feeding channel is a slit-type powder feeding channel. The convergence point of the centerline of the longitudinal section of the slit-type powder feeding channel and the centerline of the longitudinal section of the laser beam cavity is both on the central axis of the diffuser hole.

2. The laser thermal spray gun according to claim 1, characterized in that, The diameter of the larger end of the diffusion hole is twice the diameter of the smaller end of the diffusion hole, and the length of the diffusion hole is 130mm~160mm.

3. The laser thermal spray gun according to claim 1, characterized in that, The laser beam cavity has an inverted conical structure with a taper of 50:88 to 65:

88. The powder feeding channels are evenly distributed around the annular periphery of the laser beam cavity.

4. The laser thermal spray gun according to claim 1, characterized in that, The annular space formed by the splicing of the cooling sleeve and the Laval tube is a cooling channel, and the powder feeding body and the Laval tube are integrally formed.

5. The laser thermal spray gun according to claim 1, characterized in that, The air knife assembly includes an upper air knife and a lower air knife that are spliced ​​together, and the air knife assembly is located above the laser beam cavity.

6. The laser thermal spray gun according to claim 5, characterized in that, The angle between the center line of the longitudinal section of the slit-type powder feeding channel and the center line of the longitudinal section of the laser beam cavity is 32°~40°.

7. The laser thermal spray gun according to claim 5, characterized in that, The small end diameter of the laser beam cavity is 6-8 mm, and the small end diameter of the diffusion hole is 8-10 mm.

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