A method and device for laser drilling of a metal with a thermal barrier coating and efficient electrolytic post-processing of the inner wall

Abstract

The application discloses a kind of with thermal barrier coating metal laser punching and inner wall efficient electrolysis post-processing processing device and method, belong to special processing field.The present application realizes efficient drilling by laser;Micro-hole is drilled through, and capillary force makes electrolyte fill micro-hole, and overflow on upper surface part;Deep cold environment is introduced above, realize that electrolyte containing carbon nanotube in micro-hole is frozen instantly, and the shape of conductive ice column is perfectly fitted with hole inner wall;Then, with the reticular electrode on thermal barrier coating as cathode, with thermal barrier coating metal workpiece as anode, the current generated makes ice column gradually melt, and begins electrolysis to inner wall;Low-pressure environment introduced below makes electrolyte begin to flow inside hole, and further electrolysis treatment is carried out to inner wall, and carry away processing product.This method makes that hole inner wall thermal damage place is isolated with maximum oxygen and accurate electrolysis treatment, simultaneously, melted electrolyte can carry out secondary electrolysis treatment to thermal damage place and carry away product, so that high-quality gas film hole wall can be obtained.

Description

Technical Field

[0001] This invention relates to the field of special processing technology, and in particular to a processing apparatus and method for laser drilling and high-efficiency electrolytic post-processing of metals with thermal barrier coatings. Background Technology

[0002] Improving the high-temperature resistance of turbine blades is key to advancing aero-engine technology, and the current mainstream methods are film cooling and thermal barrier coating (TBC) technology. TBCs have low thermal conductivity, reducing the temperature of the blade substrate and providing thermal protection. Simultaneously, by injecting cool air into the high-temperature airflow, a lower-temperature cooling film is formed on the blade surface, further reducing the blade's surface temperature.

[0003] The film cooling pores on blades are characterized by small diameter, large number, high aspect ratio, complex spatial angles, and extremely high quality requirements. Currently, they are mainly processed using methods such as electrical discharge machining (EDM), long-pulse laser, and electrohydraulic beam machining. Since the thermal barrier coating is non-conductive, EDM cannot be used for this purpose. Traditional long-pulse lasers can cause defects such as coating surface peeling, cracking, and edge chipping. Electrohydraulic beam machining has low efficiency, difficulty in controlling the hole shape, and the electrolyte is corrosive, making it difficult to process irregularly shaped holes. Composite machining methods such as electrohydraulic beam-electrochemical and laser-EDM can achieve secondary processing, but the consistency of the holes is limited.

[0004] Chinese patent CN112171184A discloses a composite processing method for film pores on blades. First, the required film pores are drilled in a thermal barrier coated alloy substrate using a laser. Then, a high-speed rotating drill bit is used as the cathode and the blade as the anode. The drill bit moves up and down to perform online electrolytic post-treatment on the film pores in the metal substrate to eliminate defects such as residual stress and heat-affected zones during the drilling process. At the same time, tiny abrasive particles are suspended in the electrolyte. Driven by the high-speed rotating drill bit, they perform micro-impact scratching on the hole wall, producing a grinding and polishing effect. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a processing apparatus and method for laser drilling and high-efficiency electrolytic post-processing of metals with thermal barrier coatings, thereby solving the problems of difficult drilling and significant thermal damage in metals with thermal barrier coatings.

[0006] The present invention achieves the above-mentioned technical objectives through the following technical means.

[0007] A method for laser drilling and high-efficiency electrolytic post-processing of thermal barrier coated metals includes the following steps: laser drilling micro-holes in the thermal barrier coated metal workpiece, filling the micro-holes with electrolyte, freezing the electrolyte in the micro-holes to form micro-ice columns; using the thermal barrier coated metal workpiece as the anode and the mesh electrode as the cathode to electrochemically process the inner wall of the micro-holes, thereby eliminating or reducing the thermal damage to the inner wall caused by laser processing of the micro-holes.

[0008] In the above scheme, a laser is used to drill micro-holes in a metal workpiece with a thermal barrier coating. The bottom of the workpiece is in contact with an electrolyte. As the laser drills through the hole, the electrolyte fills the micro-hole under the influence of capillary force and changes in optical breakdown pressure, and overflows onto the surface of the workpiece, forming droplet protrusions near the micro-hole inlet. A cryogenic environment is introduced above the workpiece to instantly freeze the electrolyte inside the micro-hole. After the laser drilling is completed, an electrolyte ice column is formed inside the drilled micro-hole, and the shape of the ice column fits the inner wall of the micro-hole, forming a micro-protrusion at the micro-hole inlet.

[0009] In the above scheme, the electrolyte contains carbon nanotubes, which can form a conductive network after freezing, giving the ice column conductivity.

[0010] In the above scheme, a mesh electrode is used as the cathode, which is attached to the upper surface of the metal workpiece with thermal barrier coating and connected to each micro ice column through micro protrusions at the micropore entrance; the metal workpiece with thermal barrier coating is used as the anode, and an external DC pulse power supply is connected to generate current, which heats up at the interface between the ice column and the inner wall of the micropore, and the ice column gradually melts, while the inner wall of the hole begins to electrolyze.

[0011] In the above scheme, a low-pressure environment is introduced below the metal workpiece with thermal barrier coating. After the micro-ice columns completely melt, under the action of the pressure difference between the top and bottom, the electrolyte begins to flow autonomously from top to bottom through the micropores, further electrolyzing the inner wall of the pores, while carrying away the processing products.

[0012] In the above scheme, a low-pressure environment is provided by stirring the electrolyte with a stirring device.

[0013] In the above scheme, the metal workpiece with thermal barrier coating is a DD6 nickel-based single crystal high-temperature alloy blade.

[0014] A processing apparatus for laser drilling and high-efficiency electrolytic post-processing of thermal barrier coated metals includes an optical path system, an electrolytic processing system, a cooling system, and a stirring system. The optical path system includes a laser, an optical fiber, and a focusing lens. The laser and optical fiber are connected, and the focusing lens irradiates the thermal barrier coated metal workpiece. The upper end of the thermal barrier coated metal workpiece is placed within the cooling system. The electrolytic processing system includes a DC pulse power supply, a voltmeter, an ammeter, and a mesh electrode. The positive terminal of the DC pulse power supply is connected to the thermal barrier coated metal workpiece, and the negative terminal is connected to the mesh electrode. The electrolysis reaction is observed and adjusted using voltmeters and ammeters. The cooling system includes a pressure supply device, a cylindrical cryogenic sealing device, a vaporization nozzle, and a liquid nitrogen storage tank. Liquid nitrogen in the storage tank is pressurized by the pressure supply device, transported through pipelines to the flow hole of the cylindrical cryogenic sealing device, and finally sprayed onto the metal workpiece with thermal barrier coating through the vaporization nozzle, forming a cryogenic environment. The stirring system includes an anchor-type stirring device. The anchor-type stirring device is located in the center of the processing tank. When the blades rotate at high speed, a swirling phenomenon is generated, creating a low-pressure environment below the metal workpiece with thermal barrier coating.

[0015] In the above scheme, the electrolyte used is sodium nitrate or sodium chloride, with a mass fraction of 10%-30%.

[0016] In the above scheme, the laser is a nanosecond or picosecond laser.

[0017] Beneficial effects:

[0018] (1) This invention utilizes capillary force and a cryogenic environment during laser drilling to cause the electrolyte containing carbon nanotubes to freeze inside the gas film pores, thereby performing electrolytic treatment. This effectively isolates oxygen and allows the ice column to precisely adhere to the inner wall of the pore, reducing thermal damage.

[0019] (2) Due to the heating of the pore wall interface and the low-pressure environment, the ice melts and flows down to perform secondary electrolysis on the pore wall, which produces a polishing effect and further improves the quality of the inner wall of the gas film pore; at the same time, the melted electrolyte will efficiently carry away the products.

[0020] (3) The method of the present invention is efficient and precise. Laser processing solves the problem that conventional electrical discharge machining methods cannot process thermal barrier coatings; the efficient and accurate electrolytic treatment of conductive ice solves the problems of low efficiency and thermal damage in laser processing of alloys.

[0021] (4) The method of the present invention enables the heat-damaged area of ​​the pore wall to be isolated from oxygen to the maximum extent and to be precisely electrolyzed. At the same time, the melted electrolyte can perform secondary electrolysis on the heat-damaged area and remove the products, thereby obtaining a high-quality gas film pore wall. Attached Figure Description

[0022] Figure 1The diagram shows the laser drilling and high-efficiency electrolytic post-processing of the inner wall of the metal with thermal barrier coating involved in the embodiments of the present invention.

[0023] Figure 2 In order to be in Figure 1 A schematic diagram showing the addition of a DC pulse power supply and mesh electrodes to the existing structure;

[0024] Figure 3 for Figure 1 The diagram shows the structure of the cylindrical cryogenic sealing device involved.

[0025] Figure label:

[0026] 1-Laser; 2-Fiber optic cable; 3-Focusing lens; 4-Pressure supply device; 5-Cylindrical cryogenic sealing device; 6-Vaporization nozzle; 7-Liquid nitrogen storage tank; 8-Metal workpiece with thermal barrier coating; 9-Machining groove; 10-Clamp; 11-Anchor-type stirring device; 12-DC pulse power supply; 13-Voltmeter; 14-Ammeter; 15-Mesh electrode; 16-Flow hole; 17-Outer cylinder; 18-Insulating sealant; 19-Inner cylinder. Detailed Implementation

[0027] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0028] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "axial," "radial," "vertical," "horizontal," "inner," and "outer," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0029] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0030] A method for laser drilling and high-efficiency electrolytic post-processing of air film holes with thermal barrier coating includes the following steps:

[0031] Step 1: High-efficiency drilling of thermally barrier coated metal workpieces is achieved using lasers, with adjustable hole diameter, tilt angle, and drilling position. The workpiece 8 is in contact with an electrolyte solution. Simultaneously with laser drilling, the electrolyte fills the micropores due to capillary force and changes in optical breakdown pressure, overflowing from the surface of the workpiece and forming droplet protrusions near the micropore entrance. A cryogenic environment is introduced above the workpiece 8, instantly freezing the electrolyte within the micropores. After laser drilling, an electrolyte ice column forms inside the drilled hole, perfectly conforming to the inner wall of the hole and forming a micro-protrusion at the hole entrance. The electrolyte used is a special electrolyte containing carbon nanotubes; after freezing, the carbon nanotubes also form a conductive network, giving the ice column conductivity.

[0032] Step 2: A mesh electrode 15 is used as the cathode and is attached to the metal workpiece 8 with a thermal barrier coating. Each ice column is connected through a micro-protrusion at the hole entrance. The metal workpiece 8 with a thermal barrier coating acts as the anode. An external DC pulse power supply 12 is connected to generate current, which heats up at the interface between the ice column and the inner wall of the hole. The micro-ice columns gradually melt, and the inner wall begins to electrolyze, eliminating or reducing the thermal damage to the inner wall caused by laser processing. At the same time, the upper part of the metal workpiece 8 with a thermal barrier coating is the electrolyte, and a low-pressure environment is introduced below. After the micro-ice columns have completely melted, under the action of the pressure difference between the upper and lower parts, the electrolyte begins to flow autonomously from top to bottom through the micro-hole array, further electrolyzing the inner wall. At the same time, the processed products can be efficiently carried away.

[0033] In this invention, while the laser drills through the hole, the electrolyte fills the cavity. The laser breaks through the electrolyte in a narrow area inside the hole, and the resulting mechanical force efficiently peels off the laser-softened material from the inner wall of the hole. The resulting blade air film hole has a small taper and a high depth-to-diameter ratio. At the same time, by utilizing the cryogenic environment, after the laser finishes drilling at a certain point, the electrolyte inside the hole quickly forms micro-ice columns, which isolate oxygen to the greatest extent, prevent sidewall oxidation, and further reduce thermal damage.

[0034] The presence of carbon nanotubes in the electrolyte allows the electrolyte to form a highly conductive network after freezing.

[0035] By utilizing the micro-conductive ice columns generated in the air film pores and the micro-protrusion connectors at the inlet, the micro-ice columns can be connected by flexible mesh electrodes to form a cathode array, and the shape, size, angle, and position of the cathode array are perfectly matched with the air film pore array.

[0036] The metal workpiece 8 with thermal barrier coating is a DD6 nickel-based single crystal high-temperature alloy blade. By controlling the electrolytic machining parameters, the heating at the interface between the micro-ice column and the inner wall of the film gas hole can be controlled, and the ice column can be controlled to gradually melt from the outside to the inside, forming the electrolyte flow and post-electrolytic treatment; by controlling the pressure difference between the upper and lower parts of the blade, the flow rate of the electrolyte above the blade along the film gas hole can be controlled, and the inner wall of the hole can be subjected to secondary electrolytic treatment and repeated grinding and polishing of the inner wall surface.

[0037] A laser drilling and high-efficiency electrolytic post-processing device for thermally barrier coated film-film holes includes an optical path system, an electrolytic processing system, a cooling system, and a stirring system. The optical path system includes a laser 1, an optical fiber 2, and a focusing lens 3. The laser 1 and the optical fiber 2 are connected, and the laser is directed onto a thermally barrier coated metal workpiece 8 through the focusing lens 3. The upper end of the thermally barrier coated metal workpiece 8 is placed inside an inner cylinder 19. The electrolytic processing system includes a DC pulse power supply 12, a voltmeter 13, an ammeter 14, and a mesh electrode 15. The positive terminal of the DC pulse power supply 12 is connected to the thermally barrier coated metal workpiece 8, and the negative terminal is connected to the mesh electrode. The electrolysis reaction is observed and adjusted via voltmeter 13 and ammeter 14. The cooling system includes a pressure supply device 4, a cylindrical cryogenic sealing device 5, a vaporization nozzle 6, and a liquid nitrogen storage tank 7. Liquid nitrogen in the liquid nitrogen storage tank 7 is pressurized by the pressure supply device 4, transported through pipelines to the flow hole 16 of the cylindrical cryogenic sealing device 5, and finally sprayed onto the metal workpiece 8 with a thermal barrier coating through the vaporization nozzle 6, forming a cryogenic environment. The stirring system includes an anchor stirring device 11. The anchor stirring device 11 is located in the center of the processing tank. When the blades rotate at high speed, a swirling phenomenon is generated, creating a low-pressure environment below the processed sample 8. The laser 1 is a nanosecond or picosecond laser. The electrolyte used is a neutral electrolyte, preferably sodium nitrate or sodium chloride, with a mass fraction of 10%-30%.

[0038] In this invention, the cylindrical cryogenic sealing device 5 includes an outer cylinder 17 and an inner cylinder 19. The outer cylinder 17 and the inner cylinder 19 are sealed by an insulating sealant 18. A flow hole 16 is provided on the side wall of the inner cylinder 19. The flow hole 16 is connected to the output end of the pressure supply device 4. Liquid nitrogen at a certain pressure enters the vaporization nozzle 6 through the flow hole 16 and is then sprayed into the inner cylinder 19 to freeze the electrolyte in the micropores of the thermal barrier coated metal workpiece 8.

[0039] In this invention, the voltage of the DC pulse power supply 12 is selected as 3-5V, the laser power of the laser 1 is selected as 16W, the pulse repetition frequency is selected as 0.2MHz, and the scanning speed is selected as 200mm / s.

[0040] Example

[0041] In this embodiment, the metal with the thermal barrier coating is selected as DD6 nickel-based single-crystal superalloy blade. First, the DD6 nickel-based single-crystal superalloy blade is irradiated by laser 1 to obtain micropores, the diameter of which is 100-600 μm. Under the action of liquid nitrogen storage tank 8, pressure supply device 4, and vaporization nozzle 6, a cryogenic environment is created. At the same time, the cylindrical cryogenic sealing device 5 ensures that the cryogenic environment is tightly attached to the upper surface of the DD6 nickel-based single-crystal superalloy blade and does not leak out. Under the action of capillary force and the cryogenic environment above, the carbon nanotube-containing electrolyte forms conductive ice columns that adhere to the walls of the micropores. Next, a mesh electrode 15 is applied to the upper surface of the DD6 nickel-based single-crystal superalloy blade. Using the mesh electrode 15 as the cathode and the DD6 nickel-based single-crystal superalloy blade as the anode, an external DC pulse power supply 12 is connected for electrolytic treatment to gradually eliminate the thermal damage caused by laser processing. Simultaneously with the electrochemical processing, an anchor-type stirring device 11 is activated. Because it is located in the center of the processing tank and rotates at a high speed (between 1000 and 1500 r / min), a swirling phenomenon occurs, creating a low-pressure environment below the DD6 nickel-based single-crystal superalloy blade. Under the influence of interfacial heating and the pressure difference, the ice column melts, and the thermal damage is treated a second time through electrolytic treatment, achieving a polishing effect and obtaining high-quality gas film pores. Finally, the electrolyte efficiently removes the processing products.

[0042] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0043] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention.

Claims

1. A method for laser drilling and high-efficiency electrolytic post-processing of metals with thermal barrier coatings, characterized in that, The process includes the following steps: laser drilling micro-holes in a metal workpiece with a thermal barrier coating, filling the micro-holes with electrolyte, and freezing the electrolyte inside the micro-holes to form micro-ice columns. A metal workpiece with a thermal barrier coating is used as the anode, and a mesh electrode is used as the cathode to electrochemically process the inner wall of the micropore, thereby eliminating or reducing the thermal damage to the inner wall caused by laser processing of the micropore. A low-pressure environment is introduced below the metal workpiece with the thermal barrier coating. After the micro-ice column completely melts, the electrolyte begins to flow autonomously from top to bottom through the micropore under the action of the pressure difference, further electrolyzing the inner wall of the pore, while carrying away the processing products. The low-pressure environment is provided by stirring the electrolyte with a stirring device.

2. The method for laser drilling and high-efficiency electrolytic post-processing of metals with thermal barrier coatings according to claim 1, characterized in that, Laser drilling is used to create microholes in metal workpieces with thermal barrier coatings. The workpiece is in contact with an electrolyte. As the laser drills through the hole, the electrolyte fills the microhole under the influence of capillary force and changes in optical breakdown pressure. The electrolyte overflows onto the surface of the workpiece and forms droplet protrusions near the microhole inlet. A cryogenic environment is introduced above the metal workpiece with a thermal barrier coating to instantly freeze the electrolyte inside the micropore. After laser drilling is completed, an electrolyte ice column is formed inside the drilled micropore, and the shape of the ice column fits the inner wall of the micropore, forming a micro-protrusion at the entrance of the micropore.

3. The method for laser drilling and high-efficiency electrolytic post-processing of metals with thermal barrier coatings according to claim 2, characterized in that, The electrolyte contains carbon nanotubes, which can form a conductive network after freezing, giving the ice column conductivity.

4. The method for laser drilling and high-efficiency electrolytic post-processing of metals with thermal barrier coatings according to claim 1, characterized in that, A mesh electrode is used as the cathode, which is attached to the upper surface of the metal workpiece with thermal barrier coating and connected to each micro ice column through micro protrusions at the micropore entrance. A metal workpiece with a thermal barrier coating is used as the anode. When an external DC pulse power supply is connected, current is generated, which heats up at the interface between the ice column and the inner wall of the micropore. The ice column gradually melts, and at the same time, the inner wall of the pore begins to electrolyze.

5. The method for laser drilling and high-efficiency electrolytic post-processing of metals with thermal barrier coatings according to claim 1, characterized in that, The metal workpiece with thermal barrier coating is a DD6 nickel-based single crystal high-temperature alloy blade.

6. The processing apparatus for laser drilling and high-efficiency electrolytic post-processing of metals with thermal barrier coatings according to any one of claims 1 to 5, characterized in that, The system comprises an optical path system, an electrolytic machining system, a cooling system, and a stirring system. The optical path system includes a laser, an optical fiber, and a focusing lens. The laser and optical fiber are connected, and the focusing lens irradiates the workpiece with a thermal barrier coating. The upper end of the workpiece is placed within the cooling system. The electrolytic machining system includes a DC pulse power supply, a voltmeter, an ammeter, and a mesh electrode. The positive terminal of the DC pulse power supply is connected to the workpiece, and the negative terminal is connected to the mesh electrode. The electrolytic reaction is observed and adjusted using the voltmeter and ammeter. The cooling system includes a pressure supply device, a cylindrical cryogenic sealing device, a vaporization nozzle, and a liquid nitrogen storage tank. Liquid nitrogen in the storage tank is pressurized by the pressure supply device, transported through a pipeline to the flow hole of the cylindrical cryogenic sealing device, and finally sprayed onto the workpiece above the thermal barrier coating through the vaporization nozzle, creating a cryogenic environment. The stirring system includes an anchor-type stirring device. The anchor-type stirring device is located in the center of the machining tank. When the blades rotate at high speed, a swirling phenomenon is generated, creating a low-pressure environment below the workpiece.

7. The processing apparatus according to claim 6, characterized in that, The electrolyte used is sodium nitrate or sodium chloride, with a mass fraction of 10%-30%.

8. The processing apparatus according to claim 6, characterized in that, The laser is a nanosecond or picosecond laser.

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