Cooling gas nozzle module of plasma spray gun

Abstract

The invention discloses a plasma spray gun cooling gas nozzle module which comprises a plasma spray gun, a group of independent nozzle bodies distributed in an annular array are arranged at the spray end of the plasma spray gun, the number of the independent nozzle bodies is 3-8, and the gas flow of each independent nozzle body can be independently adjusted. A spiral flow deflector is arranged in the air inlet section of the independent nozzle main body; a porous diffusion structure is arranged on the wall of the outlet section of the independent nozzle main body; a miniature thermocouple and a cooling flow channel are arranged in the wall of the independent nozzle body, and a liquid cooling medium is introduced into the cooling flow channel. The cooling gas nozzles can synchronously move along with the spray gun, the plasma spraying device is suitable for various plasma spraying scenes, the multiple cooling nozzles are adopted, cooling gas is evenly covered, and uniform cooling and overheating (the temperature difference gt and 200 DEG C) are conducted on the local part of a workpiece; the arrangement of the porous diffusion structure enables the nozzle not to deform even if the nozzle is radiated by plasma for a long time.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of plasma spraying equipment, in particular to a cooling gas nozzle module of a plasma torch. BACKGROUND

[0002] Plasma spraying is to heat the introduced spraying powder to a molten or semi-molten state by using a plasma flame (non-transferred plasma arc), and under the action of the plasma flame, the powder is high-speed impacted on the surface of the treated substrate, then spreaded, and finally formed a coating with a laminated structure The patent document with the publication number CN102443754B discloses a dust removal, dust prevention and cooling device for inner hole plasma spraying, which comprises an air extraction dust separation cylinder, an air extractor, a cooling gas nozzle, a cooling gas ring I and a support. A cylinder arranged on one side of the upper part of the air extraction dust separation cylinder is connected with the air extractor through an aluminum foil hose. The inner hole torch and the air extraction dust separation cylinder are driven by a lifting mechanism to make vertical up-down movement, and the inner wall of the inner hole workpiece fixed on the rotating mechanism is sprayed. The cooling gas nozzle fixed on the cylinder externally sprays the jet spot on the inner wall of the inner hole workpiece to locally cool it. The cooling gas is blown into the gap through the openings on the cooling gas ring I to cool and prevent dust of the inner hole workpiece. The device can effectively reduce the temperature of the inner hole torch and the inner hole workpiece during the inner hole spraying process. The existing cooling nozzle of the plasma torch is mostly a simple straight hole structure.

[0003] The above patent document and prior art have the following defects: 1. Small application scope: the cooling gas nozzle of the above patent cannot move synchronously with the torch, and is only suitable for inner hole plasma spraying. 2. Concentrated gas flow: the existing cooling nozzle of the plasma torch adopts a single outlet, which leads to uneven coverage of the cooling gas, and local overheating of the workpiece (temperature difference > 200°C). 3. Damage risk: the nozzle is easily deformed by long-term plasma radiation (actual service life < 500 hours). 4. Unable to fine-tune: the traditional fixed nozzle is difficult to adapt to the cooling needs of different coating materials.

[0004] Therefore, it is necessary to provide a cooling gas nozzle module of a plasma torch to solve the above technical problems. SUMMARY

[0005] The purpose of the present application is to solve the defects in the prior art and provide a cooling gas nozzle module of a plasma torch.

[0006] The present application achieves the purpose of the invention by adopting the following technical solutions: The application discloses a cooling gas nozzle module of a plasma torch, comprising a plasma torch, wherein a group of annular array distributed independent nozzle bodies are arranged at the spraying end of the plasma torch, the independent nozzle bodies are arranged with 3-8, the gas flow of each independent nozzle body can be individually adjusted, and a spiral guide vane is arranged in the gas inlet section of the independent nozzle body; a porous diffusion structure is arranged on the wall of the outlet section of the independent nozzle body; a micro thermocouple and a cooling flow channel are arranged in the wall of the independent nozzle body, and a liquid cooling medium is introduced into the cooling flow channel.

[0007] As a further limitation of the technical solution, the spiral angle of the spiral guide vane is 15°-60°, which is used for generating a spiral flow of the cooling gas.

[0008] As a further limitation of the technical solution, the pore diameter of the porous diffusion structure is 0.05-0.3 mm, and the pore density is 50-200 pores / cm², which is used for dispersing the cooling gas into fine and dense gas flow and improving the contact area of the cooling gas and the molten coating.

[0009] As a further limitation of the technical solution, the pore channel of the porous diffusion structure is tapered from the inner wall of the independent nozzle body to the outer wall, the inlet diameter of the pore channel is larger than the outlet diameter of the pore channel, the gas is accelerated to be sprayed out, and the impact cooling effect is enhanced, and the micro-porous structure of the porous diffusion structure is processed by laser drilling and electrolytic polishing.

[0010] As a further limitation of the technical solution, the geometric shape of the outlet section of the nozzle body is a multi-section composite outlet structure, the multi-section composite outlet structure comprises a proximal section, a middle section and a distal section, the proximal section is a cylindrical channel with a length of 3-8 mm; the middle section is a gradually expanding tapered channel with a taper angle of 5°-15°; and the distal section is an arc-shaped tapered channel with a curvature radius R=1-5 mm.

[0011] As a further limitation of the technical solution, the outlet edge of the distal section is processed with a circumferentially equidistantly arranged micro-tooth structure, the micro-tooth height is 0.1-0.5 mm, the tooth spacing is 2-5 times of the tooth height, and the micro-tooth structure is used for inducing the vortex of the gas shear layer.

[0012] As a further limitation of the technical solution, the surface of the micro-tooth structure is provided with a nano-level aluminum oxide coating, and the surface roughness Ra is less than or equal to 0.2 μm, so that the flow resistance is reduced.

[0013] As a further limitation of the technical solution, the axes of the adjacent independent nozzle bodies intersect at a distance of 20-100 mm from the outlet of the plasma torch, and the distance between the intersection point and the center of the plasma jet emitted by the plasma torch is not more than 1 / 2 of the jet diameter.

[0014] Compared with the related art, the present application has the following beneficial effects: 1) Cooling uniformity is improved: the porous structure disperses the airflow into a fine air curtain, so that the airflow coverage is more than 95%, and the coating temperature difference is less than or equal to 50°C; 2) The swirling flow enhances the cooling: the helical guide vane makes the cooling gas produce controllable swirling flow, prolongs the air curtain maintenance time, makes the peripheral temperature distribution of the plasma jet more uniform, and reduces the coating cracks; 3) The micro-tooth structure induces turbulence: the periodic micro-tooth at the nozzle outlet enhances the disturbance of the gas shear layer, improves the heat exchange efficiency of the cooling gas and the plasma, and the cooling effect is improved by 30%-40%.

[0015] 4) Precise intersection control: the cooling gas intersects at a distance of 20-100mm from the nozzle outlet, ensures that the air curtain and the plasma jet interact at the best position, and reduces the coating porosity (actually reduced by 15%-20%). BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 is a sectional view of the gas nozzle body 1 of the present application.

[0017] In the figure: 1e, porous diffusion structure; 2a, proximal segment, 2b, middle segment, 2c, distal segment, 2, micro-thermocouple, 3, cooling flow channel, 3e, micro-tooth structure, 13, helical guide vane. DETAILED DESCRIPTION

[0018] The present application will be further described below in conjunction with the drawings and embodiments.

[0019] A cooling gas nozzle module of a plasma torch, comprising a plasma torch, a group of annular array distributed independent nozzle bodies are arranged at the jetting end of the plasma torch, the independent nozzle bodies are arranged with 3-8, the gas flow of each independent nozzle body can be adjusted individually, a helical guide vane 13 is arranged inside the gas inlet segment of the independent nozzle body; a porous diffusion structure 1e is arranged on the wall of the outlet segment of the independent nozzle body; a micro-thermocouple 2 and a cooling flow channel 3 are arranged in the wall of the independent nozzle body, and a liquid cooling medium is introduced into the cooling flow channel 3.

[0020] The helical angle of the helical guide vane 13 is 15°-60°, which is used to make the cooling gas produce swirling motion.

[0021] The pore diameter of the porous diffusion structure 1e is 0.05-0.3mm, and the pore density is 50-200 pores / cm², which is used to disperse the cooling gas into fine airflow and improve the contact area of the cooling gas and the molten coating. The porous diffusion structure 1e disperses the airflow into a fine air curtain, so that the airflow coverage is more than 95%, and the coating temperature difference is less than or equal to 50°C.

[0022] The helical guide vane 13 makes the cooling gas produce controllable swirl, prolongs the gas curtain maintaining time, makes the peripheral temperature distribution of the plasma jet more uniform, and reduces the coating cracks.

[0023] The hole of the porous diffusion structure 1e is tapered from the inner wall to the outer wall of the independent nozzle body, the inlet aperture of the hole is larger than the outlet aperture of the hole, the gas is accelerated to be sprayed out, and the impact cooling effect is enhanced, the micro-hole structure of the porous diffusion structure 1e is processed by laser drilling and electrolytic polishing.

[0024] The geometric shape of the outlet section of the nozzle body is a multi-section composite outlet structure, the multi-section composite outlet structure includes a proximal section 2a, a middle section 2b and a distal section 2c, the proximal section 2a is a cylindrical channel with a length of 3-8 mm; the middle section 2b is a diverging conical channel with a taper angle of 5°-15°; the distal section 2c is an arc-shaped tapered channel with a curvature radius R=1-5 mm.

[0025] The outlet edge of the distal section 2c is processed with a circumferentially equidistantly arranged micro-tooth structure 3e, the micro-tooth height is 0.1-0.5 mm, and the tooth spacing is 2-5 times of the tooth height, which is used to induce the vortex of the gas shear layer.

[0026] The micro-tooth structure 3e enhances the disturbance of the gas shear layer, improves the heat exchange efficiency of the cooling gas and the plasma, and the cooling effect is improved by 30%-40%.

[0027] The surface of the micro-tooth structure 3e is provided with a nano-scale aluminum oxide coating, and the surface roughness Ra is less than or equal to 0.2 μm, which is used to reduce the flow resistance.

[0028] The axes of the adjacent independent nozzle bodies intersect at a distance of 20-100 mm from the outlet of the plasma torch, and the distance between the intersection point and the center of the plasma jet emitted by the plasma torch is not more than 1 / 2 of the jet diameter. The cooling gas intersects at a distance of 20-100 mm from the outlet of the plasma torch, which ensures that the gas curtain and the plasma jet interact at the best position, and reduces the porosity of the coating (actually reduced by 15%-20%).

[0029] The gas inlet end of the independent nozzle body is connected to the externally provided flow control valve and the externally provided cooling gas source through pipelines in sequence, the flow control valve can accurately control the gas flow; the micro-thermocouple 2 is electrically connected to the controller; the liquid inlet end of the cooling flow channel 3 is connected to the externally provided flow pump and the externally provided liquid cooling medium storage tank through pipelines in sequence, which can realize the circulating supply and accurate regulation and control of the liquid cooling medium in the cooling flow channel 3. The design ensures that the cooling medium can stably and continuously flow into the cooling flow channel 3, when the micro-thermocouple 2 senses that the temperature is higher than the preset value, the micro-thermocouple 2 feeds back to the controller, the controller controls the flow pump to quickly enter the liquid cooling medium into the cooling flow channel 3, and the purpose of cooling is achieved.

[0030] Example 1: 1) Processing method of the holes in the porous diffusion structure 1e: Picosecond laser equipment is used to create conical microholes on nickel-based alloys with a wavelength of 532nm and a pulse energy of 0.8mJ. The inlet diameter Φ0.25mm gradually changes to the outlet diameter Φ0.1mm. Then, an electropolishing device was used with 30% vol nitric acid electrolyte, a current density of 15 A / dm², and a time of 90 s to electropolish the hole surface, reducing the surface roughness from Ra 1.2 μm to 0.05 μm.

[0031] 2) Machining method of micro tooth structure 3e: A set of teeth with a tooth height of 0.3 mm and a tooth pitch of 0.9 mm are machined at the exit edge of the distal section 2c using an electrical discharge machining (EDM) machine. After EDM machining, an aluminum oxide coating with a thickness of 200 nm is deposited on the surface of micro tooth structure 3e using chemical deposition.

[0032] Experimental results of the synergistic effect of porous structure and micro-tooth structure:

[0033] Example 2: Repairing the coating of an aero-engine turbine blade using this application 1. Cooling gas nozzle module system configuration of plasma spray gun: There are 6 independent nozzle bodies, which are arranged circumferentially at equal intervals at the spray end of plasma spray gun. The spiral guide plate 13 has a spiral angle of 30°. The porous diffusion structure 1e has a pore density of 150 pores / cm². The inlet diameter of each hole is 0.2mm and the outlet diameter is 0.1mm.

[0034] 2. Operation process: 1) Dynamic cooling control: The nozzle flow rate is adjusted according to the blade curvature. In the high curvature region (curvature > 0.8 mm⁻¹), the cooling gas flow rates of the six nozzles are 1.2 L / min, 0.9 L / min, 0.9 L / min, 1.2 L / min, 0.8 L / min, and 0.8 L / min, respectively. In other curvature regions, the cooling gas flow rate of the six nozzles is 1.0 L / min.

[0035] 2) The miniature thermocouple 2 provides real-time feedback and maintains the nozzle wall temperature between 20-40℃ by adjusting the flow rate of the liquid cooling medium in the cooling channel 3.

[0036] 3. Coating performance test results:

[0037] Example 3: Preparation of thermal barrier coating 1. The cooling gas nozzle module system configuration of the plasma spray gun provided by the present invention: There are 4 independent nozzle bodies. The included angles between the lines connecting two adjacent independent nozzle bodies and the center of the plasma spray gun are 60°, 120°, 60°, and 120° respectively. The proximal section 2a of the multi-segment composite outlet structure is a cylindrical channel with a length of 5mm, the middle section 2b is a gradually expanding conical channel with a cone angle of 10°, the distal section 2c is an arc-shaped tapered channel with a radius of curvature of 3mm, and the height of the teeth of the micro-tooth structure 3e is 0.3mm.

[0038] 2. Process control: 1) Micro-tooth vortex effect: generates periodic vortices with a frequency of ≈8kHz. 2) Applying an alumina coating with a thickness of approximately 500 nm reduces the pressure generated by gas flow by 12%.

[0039] 3. Technological effects: Coatings prepared using conventional cooling nozzles contain unmelted particles, while coatings prepared using the cooling nozzles of this invention exhibit a uniform and dense structure.

[0040] Example 4: Ultra-thin coating for precision molds (coating thickness: 100μm) 1. The configuration of the cooling gas nozzle module system of the plasma spray gun provided by the present invention is as follows: the independent nozzle body is provided with 8 holes, the aperture tolerance of the holes of the porous diffusion structure 1e is ±0.005mm, and the surface roughness Ra=0.15μm.

[0041] 2. Control of operating process parameters: 1) Cooling gas convergence point control: The axes of adjacent independent nozzle bodies converge at a distance of 50mm from the plasma spray gun outlet, and the deviation between the convergence point and the center of the plasma jet is <2mm (jet diameter ≈5mm). 2) The liquid cooling medium is an ethylene glycol solution at a temperature of -10℃, with a flow rate of 6L / min (keeping the nozzle body temperature <80℃).

[0042] 3. Technological effects: 1) Coating thickness consistency: ±1.5μm 2) Surface roughness: Ra 0.8—0.35μm Example 5: Local reinforcement treatment of irregularly shaped parts 1. The cooling gas nozzle module system configuration of the plasma spray gun provided by this invention: There are 3 independent nozzle bodies, which are circumferentially and equally spaced at the spray end of the plasma spray gun (120° interval). Special flow ratio: dynamically adjusted according to infrared thermal imager data; the spiral guide plate adopts a variable angle design, specifically the spiral angle at the inlet is 20° and the spiral angle at the outlet is 45°, and the swirl number Sn=0.6; the porous diffusion structure 1e has regional density variation of pores, with the pore density in the middle being 200 pores / cm² and gradually decreasing to 50 pores / cm² at both ends.

[0043] 2. Technological benefits: 1) Processing efficiency increased by 2.3 times (cooling time per unit area); 2) Deformation is reduced by 62% (compared to uniform cooling).

[0044] Example 6: Spraying of high reflectivity materials 1. The cooling gas nozzle module system configuration of the plasma spray gun provided by the present invention: There are 7 independent nozzle bodies, which are arranged circumferentially at equal intervals at the spray end of the plasma spray gun (51.4° interval); the composite structure works synergistically: the spiral guide generates swirling flow (circumferential speed ≥ axial speed 60%), the micro-tooth structure 3e breaks up the gas boundary layer, and the cone-shaped micropores of the porous diffusion structure 1e accelerate the airflow (exit speed reaches Mach number 0.8).

[0045] 2. Quality Control: Real-time Monitoring System 3. Technological effects:

[0046] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A cooling gas nozzle module for a plasma spray gun, comprising a plasma spray gun, characterized in that, The plasma spray gun has a set of independent nozzle bodies arranged in a ring array at the spray end. There are 3 to 8 independent nozzle bodies. The gas flow rate of each independent nozzle body is individually adjustable. The air inlet section of the independent nozzle body is provided with a spiral guide vane (13). The wall of the outlet section of the independent nozzle body is provided with a porous diffusion structure (1e). The wall of the independent nozzle body is provided with a miniature thermocouple (2) and a cooling channel (3). Liquid cooling medium is introduced into the cooling channel (3).

2. The cooling gas nozzle module of the plasma spray gun according to claim 1, characterized in that: The spiral guide vane (13) has a spiral angle of 15°–60° and is used to generate swirling motion of the cooling gas.

3. The cooling gas nozzle module of the plasma spray gun according to claim 1, characterized in that: The porous diffusion structure (1e) has a pore size of 0.05-0.3 mm and a pore density of 50-200 pores / cm², and is used to disperse the cooling gas into a fine airflow to increase the contact area between the cooling gas and the molten coating.

4. The cooling gas nozzle module of the plasma spray gun according to claim 3, characterized in that: The porous diffusion structure (1e) has a channel that tapers from the inner wall to the outer wall of the independent nozzle body. The inlet diameter of the channel is larger than the outlet diameter of the channel, which accelerates the gas ejection and enhances the impact cooling effect. The microporous structure of the porous diffusion structure (1e) is processed by laser drilling and electrolytic polishing.

5. The cooling gas nozzle module of the plasma spray gun according to claim 1, characterized in that: The nozzle body has a multi-segment composite outlet structure, which includes a proximal segment (2a), a middle segment (2b), and a distal segment (2c). The proximal segment (2a) is a cylindrical channel with a length of 3-8 mm; the middle segment (2b) is a gradually expanding conical channel with a cone angle of 5°-15°; and the distal segment (2c) is an arc-shaped gradually contracting channel with a radius of curvature R=1-5 mm.

6. The cooling gas nozzle module of the plasma spray gun according to claim 5, characterized in that: The distal segment (2c) has a circumferentially equidistant micro-tooth structure (3e) processed at its outlet edge. The micro-tooth height is 0.1-0.5 mm and the tooth spacing is 2-5 times the tooth height, which is used to induce the gas shear layer to generate vortices.

7. The cooling gas nozzle module of the plasma spray gun according to claim 6, characterized in that: The surface of the micro-tooth structure (3e) is coated with a nano-scale alumina coating with a surface roughness Ra≤0.2μm, which is used to reduce flow resistance.

8. The cooling gas nozzle module of the plasma spray gun according to claim 1, characterized in that: The axes of adjacent independent nozzle bodies intersect at a distance of 20-100 mm from the plasma spray gun outlet, and the distance between the intersection point and the center of the plasma jet emitted by the plasma spray gun does not exceed 1 / 2 of the jet diameter.

9. The cooling gas nozzle module of the plasma spray gun according to any one of claims 2-8, characterized in that: The independent nozzle body is provided with 6 nozzles, which are arranged circumferentially at equal intervals at the spray end of the plasma spray gun. The spiral guide plate (13) has a spiral angle of 30°. The porous diffusion structure (1e) has a pore density of 150 pores / cm², and the inlet diameter of each pore is 0.2 mm and the outlet diameter is 0.1 mm.

10. The cooling gas nozzle module of the plasma spray gun according to any one of claims 2-8, characterized in that: The independent nozzle body (1) is provided with 4, and the included angle between the line connecting each two adjacent independent nozzle bodies (1) and the center of the plasma spray gun is 60°, 120°, 60° and 120° respectively. The proximal section (2a) of the multi-segment composite outlet structure is a cylindrical channel with a length of 5mm, the middle section (2b) is a gradually expanding conical channel with a cone angle of 10°, the distal section (2c) is an arc-shaped tapered channel with a radius of curvature of 3mm, and the height of the teeth of the micro-tooth structure (3e) is 0.3mm.

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