A method and apparatus for additive manufacturing of a metal component with complex electrochemical polishing

Abstract

The application provides a composite electrochemical polishing method and device for additive manufacturing metal parts. The method uses dissolution and polishing to quickly remove powder adhesion and spheroidization on the inner and outer surfaces of the printed metal parts, efficiently realizes material surface leveling and brightening, and significantly reduces the number of acidic electrolyte replenishment. The composite electrochemical polishing device mainly comprises a dissolution tank, a polishing tank, a water bath tank, a control drive, a power supply, an electrode and a dissolution solution and a polishing solution. When working, the additive manufacturing metal parts to be polished are first placed in the dissolution tank to level the rough surface, then placed in the polishing tank for further smoothing and brightening, and the uniform anodic dissolution of the metal parts is realized under the control of the drive. Using the composite electrochemical polishing method and device, the surface roughness of the printed metal parts can be effectively reduced, the surface finish can be improved, and the electrochemical polishing cost can be reduced.

Description

Technical Field

[0001] This invention relates to the field of additive manufacturing technology, and more specifically to a composite electrochemical polishing method and apparatus for additively manufactured metal parts. Background Technology

[0002] Additive manufacturing, commonly known as 3D printing, facilitates the rapid fabrication of dense, robust 3D metal parts with virtually unlimited geometry and complexity. This technology is currently widely used in the aerospace, automotive, and medical implant industries. However, one of the biggest challenges in applying additive manufacturing to metals is the high surface roughness caused by unavoidable stair-stepping effects, balling, partially melted raw material powder, spatter, and incomplete melting during the manufacturing process. While optimizing laser parameters and scanning strategies can improve surface finish to some extent, achieving submicron finishes on difficult-to-machine areas of metal parts, such as sides and inner surfaces, requires appropriate post-processing techniques.

[0003] Traditional surface finishing methods for additively manufactured metal parts, such as machining, sandblasting, and abrasive flow polishing, cannot simultaneously achieve high efficiency and high surface quality. Electrochemical polishing methods, however, are a promising post-processing technology due to their non-contact nature, absence of consumable electrodes, independence from workpiece strength and hardness, absence of surface damage, and absence of process-induced residual stress. Furthermore, the invasive nature of electrolytes enables the polishing of complex internal surfaces. Traditional electrochemical polishing of additively manufactured metal parts, based on a single electrochemical process, often results in low-selectivity polishing areas and is prone to uneven polishing and low efficiency. The complex structures of additively manufactured metal parts exacerbate these problems. Therefore, there is an urgent need to research a polishing device and method that can achieve uniform and high-efficiency polishing. Summary of the Invention

[0004] The purpose of this invention is to provide a composite electrochemical polishing method and apparatus for additively manufactured metal parts. This is a two-step electrochemical polishing method that reduces the surface roughness of the inner and outer surfaces of additively manufactured metal parts while reducing the number of polishing slurry replacements, thereby improving the efficiency and uniformity of electrochemical polishing. Furthermore, this apparatus and method are applicable to the surface polishing of various additively manufactured metal parts.

[0005] The objective of this invention can be achieved through the following methods:

[0006] In a first aspect, the present invention provides a composite electrochemical polishing device for additive manufacturing of metal parts, the polishing device comprising a polishing assembly (15), a polishing liquid circulation device (16), and a power supply (1);

[0007] The polishing assembly (15) includes a dissolution tank (3), a first metal cathode (4), a first metal anode to be processed (5), a water bath (6), a heating table (7), a second metal cathode (12), a polishing tank (13), a drive control (14), and a second metal anode to be processed (17); the dissolution tank (3) and the polishing tank (13) are arranged side by side above the heating table (7); the polishing tank (13) includes an inner layer and an outer layer, the inner layer being a liquid tank (18) and the outer layer being a water bath (6); the first metal cathode (4) is located in the dissolution tank (3) and is connected by a drive control device. The wire (2) is connected to the negative terminal of the power supply (1); the second metal cathode (12) is the wall of the liquid tank and is connected to the negative terminal of the power supply (1) through the wire (2); the first metal anode to be processed (5) is located in the dissolution tank (3) and is connected to the positive terminal of the power supply (1) through the wire (2); the second metal anode to be processed (17) is located in the polishing tank (13) and is connected to the positive terminal of the power supply (1) through the wire (2) via the drive control (14); the dissolution tank (3) contains dissolving liquid and the liquid tank (18) in the polishing tank (13) contains polishing liquid;

[0008] The polishing fluid circulation device (16) is connected to the polishing tank (13).

[0009] As one embodiment of the present invention, the polishing liquid circulation device (16) includes a circulation pipe (8), a filter (9), a circulation pump (10), and a flow valve (11); one end of the circulation pump (10) is connected to the outlet (19) of the polishing tank (13) through the filter (9) via the circulation pipe (8); the other end of the circulation pump (10) is connected to the inlet (20) of the polishing tank (13) through the flow valve (11) via the circulation pipe (8).

[0010] Furthermore, the polishing slurry flows back to the polishing tank (13) sequentially through the circulation pipe (8), filter (9), circulation pump (10), and flow valve (11), ensuring rapid flow and renewal of the polishing slurry. This makes the exchange of current and ions more uniform and sufficient, ensuring uniform polishing of the metal surface. The filter can filter out reaction products in the polishing slurry, and the flow valve can adjust the circulation rate of the polishing slurry.

[0011] In one embodiment of the present invention, the dissolving solution includes a NaNO3 solution.

[0012] In one embodiment of the present invention, the mass fraction of the solution is 0.5-20 wt.%.

[0013] As one embodiment of the present invention, the dissolving pool is a reaction vessel for the part to be processed during the roughing process. Its material can be metal, ceramic or plastic that does not react with the polishing liquid, and it can withstand the temperature generated during the dissolving process.

[0014] As one embodiment of the present invention, the material of the dissolving tank (3) includes at least one of stainless steel, fiberglass and polytetrafluoroethylene.

[0015] In one embodiment of the present invention, a stirring device is placed inside the dissolving tank. The stirring device is used to accelerate the flow and turnover of the dissolving liquid, ensuring that the temperature is uniform throughout the dissolving tank and that the components dissolve evenly.

[0016] As one embodiment of the present invention, the material of the first metal cathode (4) includes at least one of stainless steel, titanium alloy, and brass. The first metal cathode also includes other metallic materials that do not react with the solution.

[0017] In this invention, the first metal cathode (4) is plate-shaped.

[0018] As one embodiment of the present invention, the first metal anode to be processed (5) includes an unprocessed printed metal part obtained by additive manufacturing methods such as selective laser melting and directional energy deposition.

[0019] In this invention, the metal component includes at least one of aluminum alloy, titanium alloy, and nickel-based high-temperature alloy.

[0020] As one embodiment of the present invention, the polishing tank is a reaction vessel for the workpiece during the finishing process. Its material can be metal, ceramic or plastic that does not react with the polishing liquid, and it can withstand the temperature generated during the polishing process.

[0021] As one embodiment of the present invention, the polishing pool (13) is made of at least one of stainless steel, fiberglass and polytetrafluoroethylene.

[0022] As one embodiment of the present invention, the water bath (6) and the polishing liquid circulation device (16) are used to ensure the rapid flow and renewal of the polishing liquid and the uniform temperature distribution; the polishing pool includes a heating platform (7), which can heat the polishing liquid according to the polishing temperature requirements of different metal parts, so that the temperature in the polishing pool matches the metal parts to be polished.

[0023] As one embodiment of the present invention, the polishing fluid is a polishing fluid corresponding to the metal material of the part to be processed.

[0024] As one embodiment of the present invention, the polishing liquid includes at least one of sulfuric acid-phosphoric acid system polishing liquid, nitric acid system polishing liquid, and sodium hydroxide system polishing liquid.

[0025] Furthermore, the sulfuric acid-phosphoric acid polishing solution comprises 10-50% sulfuric acid (98% by mass), 10-50% phosphoric acid (85% by mass), and the balance being additives; the nitric acid polishing solution comprises 10-35 g / L fluoroboric acid, 5-25 g / L nitric acid, and 2-10 g / L boric acid; the sodium hydroxide polishing solution comprises 50-80 g / L sodium hydroxide and 10-40 g / L sodium fluoride; and the additives include at least one of water, ethylene glycol, hydrofluoric acid, glycerol, and oxalic acid.

[0026] In one embodiment of the present invention, the second metal cathode (12) is used to provide a uniform electric field, and the material of the second metal cathode includes at least one of stainless steel, titanium alloy, and brass. The material of the second metal cathode also includes a metal material that does not react with the polishing liquid.

[0027] In this invention, the second metal cathode (12) is cylindrical.

[0028] As one embodiment of the present invention, the second metal anode to be processed (17) is the first metal anode to be processed after surface dissolution.

[0029] As one embodiment of the present invention, the second metal anode (17) to be processed in the polishing tank is connected to the drive control (14), which can make the part to be processed rotate and move up and down during the polishing process, promoting the flow and renewal of the polishing liquid inside the part.

[0030] Secondly, the present invention provides a composite electrochemical polishing method for additively manufactured metal parts, wherein the composite electrochemical polishing method uses the polishing apparatus and is completed sequentially through the following steps:

[0031] S1. Take the additive manufacturing metal part to be processed as the first metal anode (5), place the first metal anode (5) and the first metal cathode (4) in the dissolution pool (3), set the dissolution voltage, start the power supply (1) and keep it for a period of time (turn off the power supply and remove the metal anode), and the additive manufacturing metal part after surface dissolution can be obtained.

[0032] S2. The additively manufactured metal part after surface dissolution is used as the second metal anode to be processed (17). It is placed in the polishing tank (13), the heating stage (7) is started until the temperature reaches the polishing temperature, the circulation pump (10) and drive control (14) are started, the power is turned on and maintained for a period of time (then the device is turned off and the metal anode part is removed) to obtain the additively manufactured metal part after composite electrochemical polishing.

[0033] As one embodiment of the present invention, in step S1, the additive manufacturing metal part to be processed is a metal part that has undergone surface cleaning pretreatment; the cleaning pretreatment includes: using alcohol to perform ultrasonic cleaning on the additive manufacturing metal part to be processed to remove powder from the inner and outer surfaces.

[0034] As one embodiment of the present invention, in step S1, a first metal cathode (4) of the corresponding size is selected according to the size of the additive manufacturing metal part to be processed.

[0035] In one embodiment of the present invention, in step S1, the dissolution voltage is 10-30V, and the holding time is 30-60s. Within the set time, the particles adhering to the metal anode surface and the irregular structure caused by spheroidization, etc., are gradually leveled.

[0036] As one embodiment of the present invention, step S1 further includes cleaning the obtained additively manufactured metal part after surface dissolution with alcohol.

[0037] In one embodiment of the present invention, in step S2, the polishing temperature is 40-60℃; the power supply voltage is 5-25V; and the time is 15-60s. Within the set time, the surface of the metal anode is further smoothed and brightened under the action of electrochemical polishing. In practical applications, appropriate polishing liquid, polishing temperature, and flow valve adjustment are selected according to the metal to be processed and the material of the metal cathode.

[0038] As one embodiment of the present invention, step S2 further includes cleaning the obtained composite electrochemically polished additive manufacturing metal part with alcohol.

[0039] In this invention, the composite electrochemical polishing method includes: roughing the printed metal component in a dissolution tank. At the start of dissolution, both the metal anode and the metal plate cathode should be immersed in the dissolution solution and placed vertically. The required voltage, time, and electrode spacing are set according to the characteristics of the metal anode material to control the degree of dissolution of protruding areas on the surface of the printed metal component and gradually smooth it out; finely polishing the printed metal component in a polishing tank. At the start of polishing, both the metal anode and the second metal cathode should be immersed in the polishing solution, with their axes collinear and both placed vertically. Under the action of a circulating pump and drive control, the surface of the printed metal component gradually becomes smooth and bright under the set time and voltage. The actual size of the metal cathode needs to be adjusted accordingly based on the size of the metal anode.

[0040] The composite electrochemical polishing method of this invention utilizes dissolution and polishing to rapidly remove powder adhesion and spheroidization from the inner and outer surfaces of printed metal parts, efficiently achieving surface smoothing and brightness while significantly reducing the frequency of acidic electrolyte replenishment. The composite electrochemical polishing apparatus mainly includes a dissolution tank, a polishing tank, a water bath, a control drive, a power supply, electrodes, and dissolution and polishing solutions. During operation, the additively manufactured metal part to be polished is first placed in the dissolution tank for rough surface smoothing, and then placed in the polishing tank for further smoothing and brightening. Uniform anodic dissolution of the metal part is achieved under controlled drive. Using this composite electrochemical polishing method and apparatus, the surface roughness of printed metal parts can be effectively reduced while improving surface finish and lowering electrochemical polishing costs.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] (1) The method for reducing the surface roughness of additively manufactured metal parts provided by the present invention is to first dissolve and then polish. Compared with single electrochemical polishing, this composite electrochemical polishing method increases the number of times the acidic polishing solution in the polishing pool can be used, and further reduces the surface roughness of the metal parts.

[0043] (2) In the process of dissolving metal parts provided by the present invention, the first solution used is environmentally friendly neutral NaNO3. Compared with the existing electrochemical polishing technology, the polishing efficiency is improved, the amount of strong acid used in the subsequent polishing process, energy consumption and processing time are reduced, and the surface roughness is more uniform.

[0044] (3) The device for reducing the surface roughness of additively manufactured metal parts provided by the present invention is a combination of a dissolution pool and a polishing pool, which divides the reduction of the surface roughness of the metal parts into two steps. The combination of heating and circulation devices ensures the uniformity and efficiency of the dissolution process and the polishing process.

[0045] (4) The method of the present invention is simple and easy to operate. It is applicable to the polishing of printed additive manufacturing metal parts. The total processing time is less than 3 minutes (far lower than the traditional electrochemical polishing processing time) and the final polishing roughness is less than 1.1 μm. Compared with non-electrochemical polishing technology, it reduces polishing steps, has low cost and high efficiency, and is conducive to large-scale production. Attached Figure Description

[0046] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0047] Figure 1 This is a schematic diagram of the composite electrochemical polishing device of the present invention;

[0048] Figure 2The images are scanning electron microscope (SEM) images of the sample alloy before and after treatment in Example 2; where (a) is before treatment and (b) is after treatment.

[0049] Figure 3 This is a polishing effect diagram of the alloy sample in Comparative Example 1;

[0050] Explanation of reference numerals in the attached drawings: 1. Power supply; 2. Wire; 3. Dissolving tank; 4. First metal cathode; 5. First metal anode to be processed; 6. Water bath; 7. Heating platform; 8. Circulation pipe; 9. Filter; 10. Circulation pump; 11. Flow valve; 12. Second metal cathode; 13. Polishing tank; 14. Drive control; 15. Polishing assembly; 16. Polishing fluid circulation device; 17. Second metal anode to be processed; 18. Liquid tank; 19. Water outlet; 20. Water inlet. Detailed Implementation

[0051] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. The following examples are implemented under the premise of the technical solution of the present invention, providing detailed implementation methods and specific operating procedures, which will help those skilled in the art to further understand the present invention. It should be noted that the scope of protection of the present invention is not limited to the following embodiments; any adjustments and improvements made under the concept of the present invention are all within the scope of protection of the present invention.

[0052] This application discloses a composite electrochemical polishing apparatus for additively manufactured metal parts. (Refer to...) Figure 1 The composite electrochemical polishing device includes a polishing component 15, a polishing liquid circulation device 16, and a power supply 1.

[0053] The polishing assembly 15 includes a dissolution tank 3, a first metal cathode 4, a first metal anode to be processed 5, a water bath 6, a heating platform 7, a second metal cathode 12, a polishing tank 13, a drive control 14, and a second metal anode to be processed 17. The dissolution tank 3 and the polishing tank 13 are arranged side by side above the heating platform 7. The polishing tank 13 includes an inner layer and an outer layer, the inner layer being a liquid tank 18 and the outer layer being a water bath 6. The first metal cathode 4 is located in the dissolution tank 3 and is connected to the negative terminal of the power supply 1 via a wire 2. The second metal cathode 12 is the wall of the liquid tank and is connected to the negative terminal of the power supply via a wire. The first metal anode to be processed 5 is located in the dissolution tank 3 and is connected to the positive terminal of the power supply via a wire. The second metal anode to be processed 17 is located in the polishing tank 13 and is connected to the positive terminal of the power supply via a wire through the drive control 14. The dissolution tank 3 contains a dissolving liquid, and the liquid tank 18 in the polishing tank 13 contains a polishing liquid.

[0054] The polishing fluid circulation device 16 is connected to the polishing tank 13;

[0055] The polishing liquid circulation device 16 includes a circulation pipe 8, a filter 9, a circulation pump 10, and a flow valve 11; one end of the circulation pump 10 is connected to the outlet 19 of the polishing tank 13 through the filter 9 via the circulation pipe 8; the other end of the circulation pump 10 is connected to the inlet 20 of the polishing tank 13 through the flow valve 11 via the circulation pipe 8.

[0056] The dissolution pool 3 is rectangular in shape and is used to store the dissolution solution. The first metal cathode 4 and the first metal anode to be processed 5 are immersed in the dissolution solution.

[0057] Reference Figure 1 The polishing tank 13 is rectangular in shape and is used to store the polishing solution. The second metal cathode 12 and the first metal anode 5 to be processed are immersed in the polishing solution. The polishing tank 13 is located in the water bath 6 and placed on the heating platform 7 to ensure that the temperature of the polishing solution reaches the optimal polishing temperature. The polishing solution flows back to the polishing tank 13 through the circulation pipe 8, filter 9, circulation pump 10, and flow valve 11 in sequence, thereby making the exchange of current and ions more uniform and sufficient, ensuring that the metal surface is polished evenly. The metal anode 5 to be processed in the polishing tank 13 is connected to the drive control 14 to control the up-and-down movement and rotation of the metal anode in the polishing tank, improving its applicability.

[0058] It should be noted that in the following examples and comparative examples, the material of the dissolving pool (3) is polytetrafluoroethylene, the material of the first metal cathode (4) is stainless steel, the material of the polishing pool (13) is polytetrafluoroethylene, the material of the second metal cathode (12) is stainless steel, and the polishing liquid is a sulfuric acid-phosphoric acid system, the components of which include 45% sulfuric acid with a mass concentration of 98%, 45% phosphoric acid with a mass concentration of 85%, 5% ethylene glycol, and 5% water.

[0059] Example 1

[0060] In this embodiment, the above-mentioned polishing device is used to polish an additively manufactured AlSi10Mg hollow spherical sample with a size of Φ20mm. The operation steps are as follows:

[0061] (1) A hollow spherical sample with a size of Φ20mm AlSi10Mg was printed using laser selective melting technology. The sample was ultrasonically cleaned with alcohol to remove powder from the inner and outer surfaces.

[0062] (2) Connect the AlSi10Mg hollow spherical sample (as the first metal anode 5 to be processed) and the stainless steel plate (as the first metal cathode 4) to the positive and negative terminals of the power supply respectively, and immerse them in a 20wt.% NaNO3 dissolution pool. Set the DC voltage to 15V, and after dissolving for 40s, take out the sample and clean it.

[0063] (3) Place the dissolved sample (as the second metal anode 17 to be processed) in the polishing tank, start the heating table, and when the polishing liquid temperature reaches 55°C, start the circulation pump and drive control, set the polishing voltage to 16V, and after polishing for 30s, take out the sample and clean it to obtain the AlSi10Mg hollow spherical sample after composite electrochemical polishing with a roughness of 1.1um.

[0064] Example 2

[0065] In this embodiment, the aforementioned polishing apparatus is used to polish the inner channel of an additively manufactured Hastelloy X hollow cylindrical sample with dimensions of Φ5mm x 20mm. The operation steps are as follows:

[0066] (1) A Hastelloy X hollow cylindrical sample with a size of Φ5mm x 20mm was printed using laser selective melting technology. The sample was ultrasonically cleaned with alcohol to remove powder from the inner and outer surfaces.

[0067] (2) Connect the additively manufactured Hastelloy X hollow cylindrical sample (as the first metal anode 5 to be processed) and the stainless steel barrel (as the first metal cathode 4) to the positive and negative terminals of the power supply, respectively, and immerse them in a 15wt.% NaNO3 dissolution pool. Set the DC voltage to 25V, and after dissolving for 30s, take out the sample and clean it.

[0068] (3) The dissolved sample (as the second metal anode 17 to be processed) was placed in the polishing tank, the heating stage was started, and when the polishing liquid temperature reached 50℃, the circulation pump and drive control were started. The polishing voltage was set to 8V. After polishing for 1 minute, the sample was taken out and cleaned, and the additive manufacturing Hastelloy X hollow cylindrical sample after composite electrochemical polishing was obtained. The inner surface roughness was 0.45um, and the polishing effect was as follows: Figure 2 .

[0069] Comparative Example 1

[0070] The polishing method of this comparative example is basically the same as that of Example 2, except that the NaNO3 solution in step (2) is replaced with nitric acid solution. After polishing for 5 minutes, the inner surface roughness of the sample is close to 1 μm and the polishing is uneven. The polishing effect is as follows: Figure 3 .

[0071] It is evident that this invention innovatively uses environmentally friendly neutral NaNO3 solution as the solvent, based on its dissolving effect on additively manufactured metal parts, which can improve subsequent polishing efficiency, greatly reduce the total processing time, and improve polishing efficiency. Furthermore, the composite electrochemical polishing method using NaNO3 solution as the solvent for dissolution followed by polishing can improve the uniformity of polishing.

[0072] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A composite electrochemical polishing method for additively manufactured metal parts, characterized in that, The composite electrochemical polishing method uses a polishing device and is completed through the following steps: S1. Take the additive manufacturing metal part to be processed as the first metal anode (5), place the first metal anode (5) and the first metal cathode (4) in the dissolution pool (3), set the dissolution voltage, start the power supply (1) and keep it for a period of time to obtain the additive manufacturing metal part after surface dissolution. S2. The additively manufactured metal part after surface dissolution is used as the second metal anode to be processed (17), and placed in the polishing tank (13). The heating table (7) is started until the temperature reaches the polishing temperature. Then the circulation pump (10) and drive control (14) are started. The power is turned on and held for a period of time to obtain the additively manufactured metal part after composite electrochemical polishing. The polishing device includes a polishing assembly (15), a polishing fluid circulation device (16), and a power supply (1). The polishing assembly (15) includes a dissolution tank (3), a first metal cathode (4), a first metal anode to be processed (5), a water bath (6), a heating platform (7), a second metal cathode (12), a polishing tank (13), a drive control (14), and a second metal anode to be processed (17). The dissolution tank (3) and the polishing tank (13) are arranged side by side above the heating platform (7). The polishing tank (13) includes an inner layer and an outer layer, the inner layer being a liquid tank (18) and the outer layer being a water bath (6). The first metal cathode (4) is located in the dissolution tank (3) and is connected to the negative terminal of the power supply (1) through a wire (2). The second metal cathode (12) is... The liquid tank wall is connected to the negative terminal of the power supply (1) via a wire (2); the first metal anode (5) to be processed is located in the dissolution tank (3) and connected to the positive terminal of the power supply (1) via a wire (2); the second metal anode (17) to be processed is located in the polishing tank (13) and connected to the positive terminal of the power supply (1) via a wire (2) through a drive control (14); the dissolution tank (3) contains a dissolving liquid, and the liquid tank (18) in the polishing tank (13) contains a polishing liquid; the dissolving liquid includes NaNO3 solution; the polishing liquid includes at least one of sulfuric acid-phosphoric acid system polishing liquid, nitric acid system polishing liquid, and sodium hydroxide system polishing liquid; The polishing fluid circulation device (16) is connected to the polishing tank (13).

2. The composite electrochemical polishing method according to claim 1, characterized in that, The polishing liquid circulation device (16) includes a circulation pipe (8), a filter (9), a circulation pump (10), and a flow valve (11); one end of the circulation pump (10) is connected to the outlet (19) of the polishing tank (13) through the filter (9) via the circulation pipe (8); the other end of the circulation pump (10) is connected to the inlet (20) of the polishing tank (13) through the flow valve (11) via the circulation pipe (8).

3. The composite electrochemical polishing method according to claim 1, characterized in that, The mass fraction of the solution is 0.5-20 wt.%.

4. The composite electrochemical polishing method according to claim 1, characterized in that, The material of the dissolving tank (3) includes at least one of stainless steel, fiberglass, and polytetrafluoroethylene.

5. The composite electrochemical polishing method according to claim 1, characterized in that, The material of the first metal cathode (4) includes at least one of stainless steel, titanium alloy, and brass.

6. The composite electrochemical polishing method according to claim 1, characterized in that, The polishing pool (13) is made of at least one of stainless steel, fiberglass and polytetrafluoroethylene.

7. The composite electrochemical polishing method according to claim 1, characterized in that, In step S1, the dissolution voltage is 10-30V, and the holding time is 30-60s.

8. The composite electrochemical polishing method according to claim 1, characterized in that, In step S2, the polishing temperature is 40-60℃; the power supply voltage is 5-25V; and the time is 15-60s.

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