Mobile micro-arc oxidation processing equipment and preparation method thereof

Abstract

The invention belongs to the technical field of micro-arc oxidation, and particularly relates to movable micro-arc oxidation processing equipment and a preparation method thereof. Comprising a mechanical arm, a front spray head and a rear spray head which are parallel to each other are arranged at the moving end of the mechanical arm, and the front spray head and the rear spray head are connected through a liquid guide pipe and an electrolyte tank; the working table is located below the mechanical arm, and the working table is used for placing a sample; an anode of the power supply is connected with the sample through a wire, and a cathode of the power supply is connected with the front spray head and the rear spray head; and the driving device is used for driving the electrolyte in the electrolyte tank to enter the front spray head and the rear spray head. By constructing a coaxial serial double-nozzle structure and introducing a semi-dry conductive hydrogel bottom layer and a modified electrolyte, staged growth of a film layer, continuous coverage of the electrolyte and thermal stress buffering are realized, and the uniformity of micro-arc discharge, the compactness of the film layer and the overall process stability are effectively improved.

Description

Technical Field

[0001] This invention belongs to the technical field of micro-arc oxidation, and specifically relates to a mobile micro-arc oxidation processing device and its preparation method. Background Technology

[0002] Micro-arc oxidation (MAO), as a highly efficient surface modification technology, can prepare ceramic films with high hardness, corrosion resistance, and wear resistance on the surfaces of aluminum, magnesium, titanium, and their alloys. Traditional tank-type MAO equipment usually relies on large-volume electrolytic cells and fixed electrodes to realize the process, but it has many limitations in the treatment of large-sized components and local repairs. For example, large-sized components cannot be placed in the electrolytic cell, and it is not possible to treat samples locally.

[0003] To overcome the limitations of tank-type processes, "mobile" micro-arc oxidation equipment has been proposed in recent years, which achieves localized treatment by moving the spray electrode relative to the sample surface. This method improves the adaptability to large-area components and complex curved surfaces to some extent, and also reduces the overall equipment size and energy consumption. However, most existing mobile micro-arc oxidation systems use a single-nozzle structure, with limited control over current density and fluid flow rate, making it difficult to simultaneously meet the phased requirements of "rapid formation - gradual densification" of the film layer. As a result, the initial film formation rate is insufficient, and later, unstable discharge or high film porosity is prone to occur. Furthermore, since the electrolyte is mostly a low-viscosity water-based system, the fluid residence time during spraying is limited, and localized areas may still experience electrolyte drying or uneven supply, thus inducing localized overheating and film defects.

[0004] Therefore, in mobile micro-arc oxidation processes, there is an urgent need to develop a new type of equipment and method that can achieve segmented current and flow rate coordinated control, improve the local residence and coverage characteristics of electrolyte, and further enhance the discharge uniformity and film structure integrity, so as to solve the problems existing in traditional tank-type and single-nozzle mobile processes. Summary of the Invention

[0005] To address the problems of poor adaptability to mobile micro-arc oxidation, uneven film quality, unstable nozzle liquid supply, and limited current density control in existing technologies, a mobile micro-arc oxidation processing device and its preparation method are proposed. By constructing a coaxial tandem dual-nozzle structure, introducing a semi-dry conductive hydrogel underlayer, and modifying the electrolyte, staged film growth, continuous electrolyte coverage, and thermal stress buffering are achieved, effectively improving the uniformity of micro-arc discharge, film density, and overall process stability.

[0006] To achieve the above objectives, the technical solution adopted is:

[0007] In a first aspect, the present invention provides a mobile micro-arc oxidation processing device, comprising a robotic arm, wherein the moving end of the robotic arm is provided with a front nozzle and a rear nozzle that are parallel to each other, the front nozzle and the rear nozzle being connected to an electrolyte tank via a liquid guide pipe; a worktable located below the robotic arm, the worktable being used to place a sample; a power supply, the anode of the power supply being connected to the sample via a wire, the cathode of the power supply being connected to the front nozzle and the rear nozzle; and a driving device, the driving device being used to drive the electrolyte in the electrolyte tank into the front nozzle and the rear nozzle.

[0008] Furthermore, in the working state, the center distance between the front nozzle and the rear nozzle is 20~35mm, and the gap distance between the front nozzle and the sample is 1.0~2.0mm.

[0009] Furthermore, the angle between the front nozzle and the sample normal is 30°~60°, and the linear velocity of the front nozzle is 3~5mm / s.

[0010] Furthermore, the current density of the front nozzle is 8~16A / dm³. 2 The electrolyte spray volumetric flow rate of the pre-nozzle is 5.0~6.5 mL / min.

[0011] Furthermore, the current density of the rear nozzle is 3~6 A / dm³. 2 The electrolyte spray volumetric flow rate of the rear nozzle is 4.5~5.5 mL / min.

[0012] Furthermore, the power supply adopts a bipolar pulse mode with a frequency of 400Hz, an anode duty cycle of 25%, a cathode duty cycle of 10%, and a voltage limit of 480V.

[0013] Secondly, the present invention also provides a mobile micro-arc oxidation processing method, comprising the following steps:

[0014] S1. Sample pretreatment: The sample is subjected to ultrasonic cleaning, alkaline washing, acid washing and drying in sequence;

[0015] S2. Sample surface treatment: A conductive hydrogel underlayer is coated on the sample surface. The conductive hydrogel underlayer material includes carbon nanotubes, sodium polyacrylate, sodium alginate, Na2SiO3·9H2O and KOH.

[0016] S3. Preparation of electrolyte: The raw materials of the electrolyte include Na2SiO3·9H2O, Na3PO4, NaAlO2, KOH, HPMC and xanthan gum;

[0017] S4. Micro-arc oxidation: The sample is fixed on the worktable, and the robotic arm, in conjunction with the driving device, drives the electrolyte to be sprayed onto the sample surface for micro-arc oxidation processing.

[0018] Further, the preparation steps of the conductive hydrogel bottom layer include: adding 0.5 parts Na2SiO3·9H2O, 0.2 parts KOH, 0.5 parts sodium polyacrylate, and 0.15 parts sodium alginate sequentially to 100 parts deionized water, stirring magnetically for 30 min, then adding 0.05 g of carbon nanotube slurry with a solid content of 5~15wt%, and continuing to stir for 30~50 min to obtain a gel solution; uniformly coating the gel solution onto the sample surface to obtain a wet film, and allowing it to stand at room temperature for 90~120 s to obtain the conductive hydrogel bottom layer.

[0019] Furthermore, the thickness of the wet film is 80~100μm, and the conductive hydrogel bottom layer is in a semi-dry state.

[0020] Further, in step S3, the electrolyte is prepared by sequentially adding 10 parts Na2SiO3·9H2O, 7 parts Na3PO4, 4 parts NaAlO2, and 2 parts KOH, stirring for 20-30 minutes, adding 0.03 parts hydroxypropyl methylcellulose and 0.005 parts xanthan gum, stirring for 1-2 hours, and allowing to stand to degas.

[0021] The beneficial effects achieved by adopting the above technical solution are:

[0022] ① This invention introduces a conductive hydrogel underlayer on the sample surface, which effectively improves the discharge uniformity and stability of the micro-arc oxidation process. The conductive network of carbon nanotubes in the gel reduces the local resistance of the sample surface, making the discharge distribution more uniform; sodium polyacrylate and sodium alginate provide good film-forming properties and adhesion, prolonging the residence time of the electrolyte on the surface and avoiding the formation of local dry areas; inorganic components such as Na2SiO3 and KOH serve as active components, providing a silicon source and alkaline environment for film formation, promoting the growth of the micro-arc oxidation film. The presence of the semi-dry conductive hydrogel underlayer also acts as a buffer during discharge, reducing the damage of thermal stress to the film adhesion. At the same time, the semi-dry conductive hydrogel underlayer gradually participates in and dissolves in the electrolyte system during the subsequent micro-arc oxidation process, without leaving residues or interfering with the normal formation of the film, thereby ensuring process continuity and film integrity.

[0023] ② In this invention, the introduction of hydroxypropyl methylcellulose (HPMC) and xanthan gum into the electrolyte significantly improves the rheological properties of the solution, giving it certain thixotropic and shear-thinning characteristics. Under spraying and shearing conditions, the electrolyte viscosity decreases rapidly, ensuring good fluidity and replenishment. Furthermore, in the localized low-shear environment of the "nozzle-sample surface," the electrolyte maintains a high viscosity, prolonging its residence time on the sample surface and enhancing wetting and covering effects. This characteristic not only improves the stability of the electrolyte around the discharge channel, preventing localized drying and arc instability, but also promotes the uniformity of the film-forming reaction, thereby contributing to obtaining a denser, continuous, and stable micro-arc oxidation film.

[0024] ③ In this invention, two coaxial tandem moving nozzles are used as cathode spray electrodes, enabling segmented current and flow rate coordinated control during micro-arc oxidation. The front nozzle operates with a higher current density and spray flow rate to rapidly initiate micro-arc discharge and promote initial film growth, while the rear nozzle follows with a lower current density and flow rate, stabilizing the discharge and densifying the film, thus forming a gradient growth mode of "rapid generation - gradual densification". Simultaneously, the dual-nozzle design ensures continuous coverage and replenishment of the electrolyte in the treatment zone. The front nozzle provides rinsing and initial cooling, while the rear nozzle replenishes the electrolyte to maintain stable composition and temperature, avoiding localized electrolyte shortages or overheating. By rationally setting the center-to-center distance between the front and rear nozzles, the spray zones overlap while avoiding excessive overlap, further improving the uniformity and stability of the discharge, effectively reducing edge effects and localized overheating, ultimately ensuring that the formed micro-arc oxidation film has superior structural integrity and process controllability. Attached Figure Description

[0025] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings of the embodiments of the present invention will be briefly described below. The drawings are merely illustrative of some embodiments of the present invention and are not intended to limit the scope of the present invention to all embodiments.

[0026] Figure 1 This is a schematic diagram of the structure of a mobile micro-arc oxidation processing device according to the present invention;

[0027] Figure 2 This is a schematic diagram showing the positions of the front nozzle, the rear nozzle, and the sample in this invention.

[0028] The numbers in the diagram represent the following meanings:

[0029] 1. Robotic arm, 21. Front dispensing tube, 22. Rear dispensing tube, 3. Front nozzle, 4. Rear nozzle, 5. Worktable, 6. Sample, 7. Wire. Detailed Implementation

[0030] The exemplary solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Unless otherwise defined, the technical or scientific terms used in this invention should have the ordinary meaning understood by one of ordinary skill in the art.

[0031] Firstly, such as Figure 1 As shown, the present invention provides a robotic arm 1, wherein the moving end of the robotic arm 1 is provided with a front nozzle 3 and a rear nozzle 4 that are parallel to each other, and the front nozzle 3 and the rear nozzle 4 are connected to an electrolyte tank (not shown in the figure) through a liquid guide pipe.

[0032] Workbench 5, located below robotic arm 1, is used to place sample 6;

[0033] A power supply (not shown in the figure) has its anode connected to the sample 6 via a wire 7 and a clamp, and its cathode connected to the front nozzle 3 and the rear nozzle 4.

[0034] And a driving device (not shown in the figure), which is used to drive the electrolyte in the electrolyte tank into the front nozzle and the rear nozzle.

[0035] It should be understood that the front nozzle 3 and the rear nozzle 4 are driven by different driving devices and liquid guide pipes to drive the electrolyte in the electrolyte tank into their respective nozzles. For example, the electrolyte in the electrolyte tank is driven into the front nozzle 3 through the front distribution pipe 21 and the front driving device, and the electrolyte in the electrolyte tank is driven into the rear nozzle 4 through the rear distribution pipe 22 and the rear driving device, thereby controlling the electrolyte spray volume flow rate of the front nozzle 3 and the rear nozzle 4 respectively.

[0036] It should be understood that the front nozzle 3 and the rear nozzle 4 are connected to different cathodes of the power supply (not shown in the figure) to control the current density of the front nozzle 3 and the rear nozzle 4 respectively.

[0037] In this invention, two coaxial tandem moving nozzles are used as cathode spray electrodes, enabling segmented coordinated control of current and flow rate during micro-arc oxidation. The front nozzle operates with a higher current density and spray flow rate to rapidly initiate micro-arc discharge and promote initial film growth, while the rear nozzle follows with a lower current density and flow rate, stabilizing the discharge and densifying the film, thus forming a gradient growth mode of "rapid generation - gradual densification". Simultaneously, the dual-nozzle design ensures continuous coverage and replenishment of the electrolyte in the treatment zone. The front nozzle provides rinsing and initial cooling, while the rear nozzle replenishes the electrolyte to maintain stable composition and temperature, avoiding localized electrolyte shortages or overheating. By rationally setting the center-to-center distance between the front and rear nozzles, the spray zones overlap while avoiding excessive overlap, further improving the uniformity and stability of the discharge, effectively reducing edge effects and localized overheating, ultimately ensuring that the formed micro-arc oxidation film has superior structural integrity and process controllability.

[0038] In some embodiments, during operation, the center-to-center distance between the front nozzle 3 and the rear nozzle 4 is 20-35 mm, and the gap between the front nozzle 3 and the sample 6 is 1.0-2.0 mm.

[0039] It should be understood that the working state is the state in which the micro-arc oxidation process is performed.

[0040] It should be understood that the gap between the rear nozzle 4 and the sample 6 is also 1.0~2.0mm.

[0041] By controlling the center distance between the front nozzle 3 and the rear nozzle 4 to 20~35mm, and the gap distance between the front nozzle 3 (and the rear nozzle 4) and the sample 6 to 1.0~2.0mm, the present invention can ensure uniform electrolyte spray coverage, avoid local overheating or drying of the sample, thereby improving discharge stability and film density.

[0042] like Figure 2 As shown, in some embodiments, the angle α between the front nozzle and the sample normal is 30°~60°, and the linear velocity of the front nozzle is 3~5 mm / s. It should be understood that the angle between the rear nozzle 4 and the sample normal is also 30°~60°, and the linear velocity of the front nozzle is also 3~5 mm / s.

[0043] In this invention, the angle between the front nozzle and the sample normal is set to 30°~60°, and the linear velocity of the front nozzle 3 (and the rear nozzle 4) is controlled at 3~5 mm / s. This ensures that the sprayed electrolyte impacts the sample surface at a suitable angle, avoiding excessive local arc caused by vertical scouring, and also allows the electrolyte to form a uniform covering layer on the surface, which is beneficial for the uniform distribution of the discharge channel.

[0044] In some embodiments, the current density of the front nozzle is 8~16 A / dm³. 2 The electrolyte spray volumetric flow rate of the pre-nozzle is 5.0~6.5 mL / min.

[0045] In some embodiments, the current density of the rear nozzle is 3~6 A / dm³. 2 The electrolyte spray volumetric flow rate of the rear nozzle is 4.5~5.5 mL / min.

[0046] In this invention, the front nozzle 3 employs a relatively high current density (8~16A / dm³). 2 The high flow rate (5.0~6.5 mL / min) enables rapid initiation of micro-arc discharge in the early stages of membrane formation and ensures timely replenishment of electrolyte, thereby achieving rapid nucleation and initial growth of the membrane. The rear nozzle 4 uses a lower current density (3~6 A / dm³). 2 With a suitable flow rate (4.5~5.5 mL / min), stable discharge can be maintained in the later stage of membrane growth, and a continuous electrolyte supply can be provided, so that the membrane gradually becomes denser during the growth process.

[0047] In some embodiments, the power supply adopts a bipolar pulse mode with a frequency of 400Hz, an anode duty cycle of 25%, a cathode duty cycle of 10%, and a voltage limit of 480V.

[0048] Secondly, the present invention provides a mobile micro-arc oxidation processing method, comprising the following steps:

[0049] S1. Sample pretreatment: The sample is subjected to ultrasonic cleaning, alkaline washing, acid washing and drying in sequence;

[0050] S2. Sample surface treatment: A conductive hydrogel underlayer is coated on the sample surface. The conductive hydrogel underlayer material includes carbon nanotubes, sodium polyacrylate, sodium alginate, Na2SiO3·9H2O and KOH.

[0051] S3. Preparation of electrolyte: The raw materials of the electrolyte include Na2SiO3·9H2O, Na3PO4, NaAlO2, KOH, HPMC and xanthan gum;

[0052] S4. Micro-arc oxidation: The sample is fixed on the worktable, and the robotic arm, in conjunction with the driving device, drives the electrolyte to be sprayed onto the sample surface for micro-arc oxidation processing.

[0053] This invention introduces a conductive hydrogel underlayer on the sample surface, which effectively improves the discharge uniformity and stability of the micro-arc oxidation process. The conductive network of carbon nanotubes in the gel reduces the local resistance of the sample surface, resulting in a more uniform discharge distribution. Sodium polyacrylate and sodium alginate provide good film-forming properties and adhesion, prolonging the residence time of the electrolyte on the surface and avoiding the formation of local dry areas. Inorganic components such as Na2SiO3 and KOH act as active components, providing a silicon source and alkaline environment for film formation, promoting the growth of the micro-arc oxidation film. The presence of the semi-dry conductive hydrogel underlayer also acts as a buffer during discharge, reducing the damage to film adhesion caused by thermal stress. At the same time, this semi-dry conductive hydrogel underlayer gradually participates in and dissolves in the electrolyte system during subsequent micro-arc oxidation, without leaving residues or interfering with the normal formation of the film, thus ensuring process continuity and film integrity.

[0054] In this invention, the introduction of hydroxypropyl methylcellulose (HPMC) and xanthan gum into the electrolyte significantly improves the rheological properties of the solution, giving it certain thixotropic and shear-thinning characteristics. Under spraying and shearing conditions, the electrolyte viscosity decreases rapidly, ensuring good fluidity and replenishment. Furthermore, in the localized low-shear environment of the "nozzle-sample surface," the electrolyte maintains a higher viscosity, prolonging its residence time on the sample surface and enhancing wetting and coverage. This characteristic not only improves the stability of the electrolyte around the discharge channel, preventing localized drying and arc instability, but also promotes the uniformity of the film-forming reaction, thereby contributing to the acquisition of a denser, continuous, and stable micro-arc oxidation film.

[0055] Further, in step S2, the preparation steps of the conductive hydrogel bottom layer include: adding 0.5 parts Na2SiO3·9H2O, 0.2 parts KOH, 0.5 parts sodium polyacrylate, and 0.15 parts sodium alginate sequentially to 100 parts deionized water, stirring magnetically for 30 min, then adding 0.05 g of carbon nanotube slurry with a solid content of 5~15wt%, and continuing to stir for 30~50 min to obtain a gel solution; uniformly coating the gel solution onto the sample surface to obtain a wet film, and allowing it to stand at room temperature for 90~120 s to obtain the conductive hydrogel bottom layer.

[0056] Furthermore, the thickness of the wet film is 80~100μm, and the conductive hydrogel bottom layer is in a semi-dry state.

[0057] This invention controls the wet film thickness of the conductive hydrogel substrate to 80~100μm, which can form a uniform and continuous conductive coating layer on the sample surface. This ensures sufficient conductive channels while avoiding excessively thick wet films that may affect electrolyte penetration and subsequent dissolution. In addition, keeping the conductive hydrogel substrate in a semi-dry state can act as a buffer during micro-arc discharge, reducing the damage of thermal shock to the bonding force between the substrate and the film layer. At the same time, it prolongs the residence time of the electrolyte on the surface and avoids local drying, thereby contributing to the improvement of discharge uniformity and film structure integrity.

[0058] Furthermore, the temperature of the electrolyte is in the range of 25±2℃.

[0059] Further, in step S3, the electrolyte is prepared by sequentially adding 10 parts Na2SiO3·9H2O, 7 parts Na3PO4, 4 parts NaAlO2, and 2 parts KOH, stirring for 20-30 minutes, adding 0.03 parts hydroxypropyl methylcellulose and 0.005 parts xanthan gum, stirring for 1-2 hours, and allowing to stand to degas.

[0060] The present invention will be further illustrated by the following examples.

[0061] Example 1

[0062] S1. Sample pretreatment: Al-Mg-Si aluminum alloy plates with dimensions of 500mm*500mm*5mm were selected as samples. The samples were ultrasonically cleaned in acetone and deionized water for 10 minutes each. Then, they were placed in 10wt% NaOH solution for alkaline washing for 30 seconds and rinsed with deionized water. Next, they were immersed in 5wt% HNO3 solution for acid washing for 20 seconds. Finally, they were rinsed with deionized water and dried for later use.

[0063] S2. Sample surface treatment: Add 0.5g Na2SiO3·9H2O, 0.2g KOH, 0.5g sodium polyacrylate (Na-PAA), and 0.15g sodium alginate sequentially to 100mL of deionized water. Stir magnetically for 30min at room temperature until completely dissolved. Then add 0.05g carbon nanotube slurry with a solid content of 15wt% and continue stirring for 50min to obtain a gel solution. Coat the gel solution evenly onto the sample surface to obtain a wet film with a thickness of 80μm. Let stand at room temperature for 120s to obtain a semi-dry conductive hydrogel bottom layer.

[0064] S3. Prepare the electrolyte: Dissolve 10g Na2SiO3·9H2O, 7g Na3PO4, 4g NaAlO2 and 2g KOH in 1L of deionized water in sequence, stir for 20min to obtain a clear solution, then add 0.03g hydroxypropyl methylcellulose (HPMC) and 0.005g xanthan gum, continue stirring for 2h until fully swollen, let stand to remove bubbles, and obtain the electrolyte.

[0065] S4. Micro-arc oxidation: Connect sample 6 to the anode of the power supply via wire 7 and fixture and place it on the worktable 6. Control the gap between the front nozzle 3 (and the rear nozzle 4) and the surface of sample 6 to be 1.0 mm. The angle between the nozzle and the surface normal is within the range of 30°. The two nozzles move at a constant speed along the surface of sample 6 with a linear velocity of 3 mm / s.

[0066] The jet flow rate and current parameters of the two nozzles are set separately. Front nozzle: current density 8A / dm³ 2 Spray volumetric flow rate: 5.0 mL / min; Rear nozzle: Current density: 3 A / dm³ 2 The injection volumetric flow rate is 5.5 mL / min.

[0067] The power supply adopts a bipolar pulse mode with a frequency of 400Hz, an anode duty cycle of 25%, a cathode duty cycle of 10%, a voltage limit of 480V, and an electrolyte temperature maintained at 25℃.

[0068] Example 2

[0069] S1. Sample pretreatment: Al-Mg-Si aluminum alloy plates with dimensions of 500mm*500mm*5mm were selected as samples. The samples were ultrasonically cleaned in acetone and deionized water for 10 minutes each. Then, they were placed in 10wt% NaOH solution for alkaline washing for 30 seconds and rinsed with deionized water. Next, they were immersed in 5wt% HNO3 solution for acid washing for 20 seconds. Finally, they were rinsed with deionized water and dried for later use.

[0070] S2. Sample surface treatment: Add 0.5g Na2SiO3·9H2O, 0.2g KOH, 0.5g sodium polyacrylate (Na-PAA), and 0.15g sodium alginate sequentially to 100mL of deionized water. Stir magnetically for 40min at room temperature until completely dissolved. Then add 0.05g carbon nanotube slurry with a solid content of 10wt% and continue stirring for 35min to obtain a gel solution. Coat the gel solution evenly onto the sample surface to obtain a wet film with a thickness of 90μm. Let stand at room temperature for 100s to obtain a semi-dry conductive hydrogel bottom layer.

[0071] S3. Prepare the electrolyte: Dissolve 10g Na2SiO3·9H2O, 7g Na3PO4, 4g NaAlO2, and 2g KOH in 1L of deionized water in sequence. Stir for 25min to obtain a clear solution. Then add 0.03g hydroxypropyl methylcellulose (HPMC) and 0.005g xanthan gum. Continue stirring for 1.5h until fully swollen. Let stand to remove bubbles to obtain the electrolyte.

[0072] S4. Micro-arc oxidation: The sample 6 is connected to the anode of the power supply through the wire 7 and the fixture and placed on the worktable 6. The gap distance between the front nozzle 3 (and the rear nozzle 4) and the surface of the sample 6 is controlled at 2.0 mm. The angle between the nozzle and the surface normal is within the range of 45°. The two nozzles move at a constant speed along the surface of the sample 6 with a linear velocity of 4 mm / s.

[0073] The jet flow rate and current parameters of the two nozzles are set separately. Front nozzle: current density 12A / dm³ 2 The jet volumetric flow rate is 6.5 mL / min; the rear nozzle has a current density of 6 A / dm³. 2 The injection volumetric flow rate is 4.5 mL / min.

[0074] The power supply adopts a bipolar pulse mode with a frequency of 400Hz, an anode duty cycle of 25%, a cathode duty cycle of 10%, a voltage limit of 480V, and an electrolyte temperature maintained at 25℃.

[0075] Example 3

[0076] S1. Sample pretreatment: Al-Mg-Si aluminum alloy plates with dimensions of 500mm*500mm*5mm were selected as samples. The samples were ultrasonically cleaned in acetone and deionized water for 10 minutes each. Then, they were placed in 10wt% NaOH solution for alkaline washing for 30 seconds and rinsed with deionized water. Next, they were immersed in 5wt% HNO3 solution for acid washing for 20 seconds. Finally, they were rinsed with deionized water and dried for later use.

[0077] S2. Sample surface treatment: Add 0.5g Na2SiO3·9H2O, 0.2g KOH, 0.5g sodium polyacrylate (Na-PAA), and 0.15g sodium alginate sequentially to 100mL of deionized water. Stir magnetically for 30min at room temperature until completely dissolved. Then add 0.05g carbon nanotube slurry with a solid content of 15wt% and continue stirring for 50min to obtain a gel solution. Coat the gel solution evenly onto the sample surface to obtain a wet film with a thickness of 80μm. Let stand at room temperature for 110s to obtain a semi-dry conductive hydrogel bottom layer.

[0078] S3. Prepare the electrolyte: Dissolve 10g Na2SiO3·9H2O, 7g Na3PO4, 4g NaAlO2 and 2g KOH in 1L of deionized water in sequence, stir for 25min to obtain a clear solution, then add 0.03g hydroxypropyl methylcellulose (HPMC) and 0.005g xanthan gum, continue stirring for 2h until fully swollen, let stand to remove bubbles, and obtain the electrolyte.

[0079] S4. Micro-arc oxidation: Connect sample 6 to the anode of the power supply via wire 7 and fixture and place it on the worktable 6. Control the gap between the front nozzle 3 (and the rear nozzle 4) and the surface of sample 6 to be 1.5 mm. The angle between the nozzle and the surface normal is 60°. The two nozzles move at a constant speed along the surface of sample 6 with a linear velocity of 5 mm / s.

[0080] The jet flow rate and current parameters of the two nozzles are set separately. Front nozzle: current density 10A / dm³ 2 The spray volumetric flow rate is 6.5 mL / min; the rear nozzle has a current density of 4 A / dm³. 2 The injection volumetric flow rate is 4.5 mL / min.

[0081] The power supply adopts a bipolar pulse mode with a frequency of 400Hz, an anode duty cycle of 25%, a cathode duty cycle of 10%, a voltage limit of 480V, and an electrolyte temperature maintained at 25℃.

[0082] Comparative Example 1

[0083] The only difference from Example 1 is that carbon nanotube slurry was not introduced into the electrolyte; the other components and preparation steps are completely the same, and a micro-arc oxidation film layer is obtained on an aluminum alloy plate.

[0084] Comparative Example 2

[0085] The only difference from Example 2 is that hydroxypropyl methylcellulose and xanthan gum were not introduced into the electrolyte. All other components and preparation steps were completely the same, and a micro-arc oxidation film was obtained on the aluminum alloy plate.

[0086] Comparative Example 3

[0087] The only difference from Example 3 is that the sample surface was not treated, that is, no conductive hydrogel underlayer was introduced on the surface. The other components and preparation steps are completely the same, and a micro-arc oxidation film layer is obtained on the aluminum alloy plate.

[0088] Examples 1-3 all used a semi-dry conductive hydrogel bottom layer containing carbon nanotubes, introduced HPMC and xanthan gum into the electrolyte, and combined with dual-nozzle segmented current and flow control to form a continuous, dense micro-arc oxide film layer on the aluminum alloy surface with uniform surface color. The film quality of the three examples was similar, demonstrating the stability and repeatability of the process of the present invention.

[0089] Compared to Example 1, no carbon nanotubes were introduced into the conductive gel in Comparative Example 1. The sample surface lacked a continuous conductive network, the discharge distribution was uneven, and there were local areas with excessively strong arcs and weak discharge areas, resulting in ablation spots on the film surface.

[0090] Compared to Example 2, the electrolyte in Comparative Example 2 did not contain HPMC and xanthan gum, resulting in poor rheological properties. The residence time during spraying was insufficient, and local areas were prone to drying out, leading to a rough film surface with pores and cracks. The density and uniformity were significantly inferior to those of the Example.

[0091] Compared to Example 3, the sample in Comparative Example 3 did not introduce a conductive hydrogel underlayer on its surface and directly performed micro-arc oxidation on the metal surface, resulting in unstable initial discharge, concentrated local discharge, insufficient adhesion between the film and the substrate, easy peeling off at the edge area, and poor overall structural integrity.

[0092] It should be noted that when one element is described as "connected," "coupled," or "connected" to another element, it can mean that they are directly connected, coupled, or connected. However, it should be understood that there may be intermediate elements between them; that is, it covers both direct and indirect connection positions.

[0093] It should be noted that the use of words such as "one" or "a" does not necessarily indicate a quantity limitation. Words such as "including" or "contains" mean that the element or object preceding the word covers the element or object listed after the word and its equivalents, without excluding other elements or objects.

[0094] It should be noted that terms such as "up," "down," "left," and "right," which indicate orientation or positional relationship, are only used to express relative positional relationship. They are used for the convenience of describing the present invention and do not mean that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation. When the absolute position of the object being described changes, the relative positional relationship may also change accordingly.

[0095] The preferred embodiments for implementing the present invention have been described in detail above. However, it should be understood that these embodiments are merely illustrative and not intended to limit the scope, application, or construction of the invention in any way. The scope of protection of the present invention is defined by the appended claims and their equivalents. Those skilled in the art can make numerous modifications to the foregoing embodiments under the teachings of this invention, and all such modifications fall within the scope of protection of this invention.

Claims

1. A mobile micro-arc oxidation processing equipment, characterized in that, It includes a robotic arm, the moving end of which is equipped with a front nozzle and a rear nozzle that are parallel to each other, and the front nozzle and the rear nozzle are connected to an electrolyte tank through a liquid guide pipe; A worktable, located below the robotic arm, is used to place samples. A power supply, wherein the anode of the power supply is connected to the sample via a wire, and the cathode of the power supply is connected to the front nozzle and the rear nozzle; And a driving device, which is used to drive the electrolyte in the electrolyte tank into the front nozzle and the rear nozzle.

2. The mobile micro-arc oxidation processing equipment according to claim 1, characterized in that, In operation, the center-to-center distance between the front and rear nozzles is 20-35 mm, and the gap between the front nozzle and the sample is 1.0-2.0 mm.

3. The mobile micro-arc oxidation processing equipment according to claim 1, characterized in that, The angle between the front nozzle and the sample normal is 30°~60°, and the linear velocity of the front nozzle is 3~5mm / s.

4. The mobile micro-arc oxidation processing equipment according to claim 1, characterized in that, The current density of the pre-spray nozzle is 8~16A / dm³. 2 The electrolyte spray volumetric flow rate of the pre-nozzle is 5.0~6.5 mL / min.

5. A mobile micro-arc oxidation processing equipment according to claim 1, characterized in that, The current density of the rear nozzle is 3~6A / dm³. 2 The electrolyte spray volumetric flow rate of the rear nozzle is 4.5~5.5 mL / min.

6. The mobile micro-arc oxidation processing equipment according to claim 1, characterized in that, The power supply adopts a bipolar pulse mode with a frequency of 400Hz, an anode duty cycle of 25%, a cathode duty cycle of 10%, and a voltage limit of 480V.

7. A mobile micro-arc oxidation processing method, implemented according to a mobile micro-arc oxidation processing equipment as described in any one of claims 1 to 6, characterized in that, Includes the following steps: S1. Sample pretreatment: The sample is subjected to ultrasonic cleaning, alkaline washing, acid washing and drying in sequence; S2. Sample surface treatment: A conductive hydrogel underlayer is coated on the sample surface. The conductive hydrogel underlayer material includes carbon nanotubes, sodium polyacrylate, sodium alginate, Na2SiO3·9H2O and KOH. S3. Preparation of electrolyte: The raw materials of the electrolyte include Na2SiO3·9H2O, Na3PO4, NaAlO2, KOH, HPMC and xanthan gum; S4. Micro-arc oxidation: The sample is fixed on the worktable, and the robotic arm, in conjunction with the driving device, drives the electrolyte to be sprayed onto the sample surface for micro-arc oxidation processing.

8. The mobile micro-arc oxidation processing method according to claim 7, characterized in that, In step S2, the preparation steps of the conductive hydrogel bottom layer include: adding 0.5 parts Na2SiO3·9H2O, 0.2 parts KOH, 0.5 parts sodium polyacrylate, and 0.15 parts sodium alginate sequentially to 100 parts deionized water, stirring magnetically for 30 min, then adding 0.05 g of carbon nanotube slurry with a solid content of 5~15wt%, and continuing to stir for 30~50 min to obtain a gel solution; uniformly coating the gel solution onto the sample surface to obtain a wet film, and allowing it to stand at room temperature for 90~120 s to obtain the conductive hydrogel bottom layer.

9. The mobile micro-arc oxidation processing method according to claim 8, characterized in that, The thickness of the wet film is 80~100μm, and the conductive hydrogel bottom layer is in a semi-dry state.

10. The mobile micro-arc oxidation processing method according to claim 7, characterized in that, In step S3, the electrolyte is prepared by sequentially adding 10 parts Na2SiO3·9H2O, 7 parts Na3PO4, 4 parts NaAlO2, and 2 parts KOH, stirring for 20-30 minutes, then adding 0.03 parts hydroxypropyl methylcellulose and 0.005 parts xanthan gum, stirring for 1-2 hours, and allowing to stand to remove bubbles.

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