Ultrasonic-assisted cathode plasma electrolytic deposition coating and surface treatment method and device

Abstract

A method and apparatus for ultrasonic-assisted cathode plasma electrolytic deposition of coatings and surface treatment, belonging to the field of material surface treatment. First, an inorganic acid is diluted in an appropriate amount of distilled water, and then a metal salt and a water-soluble polymer are added to prepare an electrolyte. A metal substrate is then used as the cathode and an inert electrode as the anode. The horizontal distance between the cathode and the anode is adjusted, and the cathode is immersed in the electrolyte at a controlled speed through a pulling device. A direct current or pulse voltage is then applied between the cathode and the anode, and ultrasonic waves are simultaneously applied to perform coating deposition or surface treatment. The treated sample is removed, cleaned, and dried, completing the ultrasonic-assisted cathode plasma electrolytic deposition of coatings or surface treatment process. By coupling the liquid-phase discharge plasma field with the ultrasonic field, the present invention can effectively stabilize the plasma discharge process, reduce energy consumption, and reduce coarse particles formed by uneven plasma discharge deposition, making the coating surface smoother and more uniform, reducing surface roughness, and effectively removing metal surface contaminants and oxides.

Description

Technical Field

[0001] The present invention belongs to the technical field of material surface, and in particular relates to a coating and surface treatment method and device based on ultrasound-assisted cathode plasma electrolytic deposition. Background Art

[0002] Liquid plasma electrolytic deposition technology is a new concept developed in the past decade. Because the discharge process simultaneously generates strong electric fields, strong oxidative free radicals, ultraviolet rays and shock waves, it has expanded to many application fields, such as material surface cleaning, etching, film deposition, heat treatment, synthesis and welding, as well as environmental governance, biological sterilization and medical treatment.

[0003] Cathodic plasma electrolytic deposition (CPED) is a cathode process based on liquid-phase plasma electrolytic deposition (LPED). It boasts simple equipment and efficient processes, and has attracted significant attention in recent years in the fields of coating preparation and surface treatment. Its principle involves applying a voltage between two electrodes, the cathode and the anode. When the voltage exceeds a critical value, the high field strength can break down the gas film at the interface near the electrodes. The discharge phenomenon occurring at these electrodes is the CPED process. The electrolytic plasma leads to the regular formation and collapse of bubbles, generating a strong shock wave accompanied by localized melting of thin layers on the material surface. Under the action of the plasma shock wave, the material surface can be cleaned, oxides, organic matter, and nanostructured. Furthermore, the localized surface melting and subsequent quenching result in the formation of ultrafine grains and a rough surface profile, providing an excellent adhesion surface for subsequent coating treatments. Compared with traditional electrodeposition, physical or chemical vapor deposition methods, cathode plasma treatment technology can deposit metallurgically bonded metal or alloy coatings on metal surfaces with higher efficiency due to the participation of high-energy ion bombardment, so as to improve the surface properties of the base material, such as corrosion resistance and wear resistance, and achieve the purpose of surface modification.

[0004] Cathodic plasma electrolytic deposition technology has the following characteristics:

[0005] (1) Under the action of strong electrochemistry and high-energy plasma, the deposition rate is much higher than that of traditional electroplating.

[0006] (2) Due to the local high temperature generated by plasma discharge, a good diffusion bonding layer can be formed between the deposited metal coating and the substrate, which is a metallurgical bonding.

[0007] (3) The surface of the metal coating deposited by the cathode plasma electrolysis method has a layer of ultrafine nanocrystalline structure, which has excellent corrosion resistance, wear resistance and other properties compared with ordinary coatings.

[0008] (4) Under the action of high-energy plasma bombardment, surface treatment processes such as rapid cleaning of metal surfaces, descaling, and removal of organic and inorganic pollutants can be achieved in a neutral solution medium.

[0009] Cathodic plasma electrolysis technology can deposit various metal and alloy coatings or perform surface treatments. The deposited coatings and surface treatments are not limited by the base metal and can be used to prepare different coatings and surface treatments on substrates such as carbon steel, stainless steel, aluminum alloys, titanium alloys, and magnesium alloys. Although cathodic plasma electrolytic deposition technology has achieved the preparation of a variety of coatings and surface treatment applications, it still faces the following key issues that need to be resolved: First, due to the uneven discharge of the gas film during the deposition process, it is difficult to obtain a uniform and dense metal coating; second, cathodic plasma bombardment can remove general pollutants on the metal surface, but the removal efficiency of strongly bonded oxides or attachments needs to be improved; in addition, since the cathode gas film discharge process is difficult to effectively control during the electrolysis process, the current density is high and the energy consumption is high. Summary of the Invention

[0010] To address the issues with the aforementioned methods, the present invention addresses the preparation process and develops an ultrasound-assisted cathode plasma electrolytic deposition coating and surface treatment method. By introducing an ultrasonic field into the cathode plasma electrolytic deposition system, the cavitation effect of ultrasound is used to constrain the gas film discharge and stabilize the plasma discharge process. Ultrasonic waves also pulverize coarse particles produced by coating deposition, homogenize the microstructure, and polish the surface, thereby improving the performance of cathode plasma-prepared metal coatings. Furthermore, the synergistic effect of the ultrasonic field and plasma improves the efficiency of removing oxides and other deposits from metal surfaces, achieving efficient cleaning and oxide removal.

[0011] In order to achieve the above effects, the technical solutions adopted by the present invention are as follows:

[0012] A method for realizing ultrasonic-assisted cathode plasma electrolytic deposition of coating and surface treatment, comprising the following steps:

[0013] Step 1: Add an appropriate amount of distilled water to dilute the inorganic acid, then add metal salts and water-soluble polymers, and mechanically stir for 15 to 60 minutes to prepare an electrolyte; use the metal substrate as the cathode and the inert electrode as the anode, and polish the metal substrate with 200#, 400#, 800#, 1200#, 1500#, and 2000# sandpaper in stages, soak in acetone solution and ultrasonically remove surface oil stains, soak in acid solution for 1 to 3 minutes to activate, and dry for use.

[0014] Step 2: Immerse the anode in the electrolyte. Adjust the distance between the cathode and cathode to the appropriate level. Control the lifting mechanism to position the cathode just above the electrolyte level, ensuring it's out of contact. Turn on the ultrasonic system to create an ultrasonic environment.

[0015] Step 3: Turn on the pulse power supply. When the deposition voltage is reached, turn on the pull-up device switch to allow the cathode to descend at a constant speed to the appropriate position for deposition. After deposition, rinse and dry the sample.

[0016] Furthermore, the metal salt is a nitrate, chloride, sulfate or carbonate of Fe, Co, Ni, Mo, Cd, Mn, Cu, Zn, Cr, Ag, Sn, Pt, Pd, Au, Na or K; the electrolyte can be prepared from a metal salt of one element or a combination of metal salts of two or more elements.

[0017] Furthermore, the inorganic acid is sulfuric acid, hydrochloric acid, or nitric acid; the water-soluble polymer is one or a combination of polyvinyl alcohol, polyethylene glycol, polyethylene oxide, polyvinyl pyrrolidone, or a block copolymer non-ionic water-soluble polymer.

[0018] Furthermore, the anode is an inert electrode such as stainless steel, platinum, titanium or graphite, and the cathode can be made of carbon steel, stainless steel, aluminum alloy, magnesium alloy, titanium or other metals or alloys. The anode and cathode are placed in parallel with a horizontal spacing of 0.5 to 30 cm.

[0019] Furthermore, the electrolysis process adopts a DC power supply or a pulse power supply, the frequency of the pulse power supply is controlled at 10-5000 Hz, the duty cycle is controlled at 10-90%, and the electrolysis voltage is controlled at a voltage 5-100V higher than the arc starting voltage.

[0020] An apparatus for use in the method for ultrasonically assisted cathode plasma electrolytic deposition of coatings and surface treatment as described above, such as Figure 1 As shown, it includes a pulse power supply (including a computer control system), an electrolyte cooling system (water inlet and outlet), an anode, a cathode, an electrolytic cell, a support grid, an ultrasonic generating system, cooling water, an electrolyte, and a pulling device.

[0021] The connections between the various components are as follows: the ultrasonic system is fixed horizontally to the workbench, the support net supports the electrolytic cell and is immersed in cooling water. The cooling water is connected to an external circulation pump through the water inlet and outlet. The anode and cathode are vertically immersed in the electrolyte. The lifting device is located at a suitable position above the electrolytic cell to control the vertical movement of the cathode.

[0022] Furthermore, the ultrasonic source of the ultrasonic system 8 can be provided by a probe-type ultrasonic generator or an ultrasonic machine, the ultrasonic power can be adjusted to 0.1-5kW, and the ultrasonic frequency can be adjusted to 10-80kHz.

[0023] Furthermore, the pulling device is insulated from the cathode through a polytetrafluoroethylene sleeve, and the pulling or lowering speed is automatically controlled by a controller.

[0024] Furthermore, the electrolyte level should be lower than the cooling water level 9 .

[0025] Beneficial effects of the present invention:

[0026] (1) Under the action of ultrasound, the diameter of bubbles generated by electrode reaction is reduced, the attachment and retention of coarse bubbles on the cathode surface are limited, uneven discharge or arc extinction caused by large bubbles is avoided, and the bubble layer distribution on the cathode surface is more uniform, which stabilizes the plasma discharge process, increases the deposition rate, and reduces energy consumption.

[0027] (2) Under the action of ultrasonic cavitation, the coarse particles formed by plasma deposition are reduced, the surface flatness is improved, and the tip discharge process caused by surface unevenness is reduced, which is beneficial to improving the deposition efficiency and reducing the surface roughness of the coating.

[0028] (3) Under the synergistic effect of ultrasonic cavitation field and plasma, the cleaning efficiency of residual organic matter, inorganic attachments and oxides on the metal surface can be improved, and a highly clean metal surface can be obtained in a neutral aqueous solution (such as sodium bicarbonate aqueous solution). BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Schematic diagram of ultrasonic-assisted cathodic plasma electrolytic deposition coating and surface treatment device;

[0030] Pulse power supply 1 (including computer control system), electrolyte cooling system (water inlet 2, water outlet 3), anode 4, cathode 5, electrolytic cell 6, support net 7, ultrasonic generating system 8, cooling water 9, electrolyte 10 and pulling device 11.

[0031] Figure 2 The surface morphology of Ni coating was prepared without ultrasound application;

[0032] Figure 3 To prepare the surface morphology of Ni coating by applying ultrasound;

[0033] Figure 4 Comparison of current density during the deposition process with and without ultrasound. DETAILED DESCRIPTION

[0034] The above method is further described below with reference to the embodiments:

[0035] Example 1: Ultrasonic-assisted cathode plasma electrolytic deposition of Ni coating

[0036] A 30g / L sulfuric acid dilution was prepared, followed by the addition of 40g / L NiSO4·7H2O and 5g / L polyethylene glycol, and mechanical stirring was performed for 60 minutes. A 30mm×10mm×0.5mm stainless steel cathode and a 120mm×50mm×0.1mm platinum sheet anode were used. The samples were polished with 200#, 400#, 800#, 1200#, 1500#, and 2000# sandpaper in successive grades. The surface was degreased in an acetone solution with ultrasonication for 5 minutes, activated by immersion in a 10% HCl solution for 1 minute, and then dried for later use.

[0037] Immerse the platinum anode 1 cm below the electrolyte surface. Adjust the horizontal distance between the cathode and cathode to 4 cm. Control the lifting mechanism and adjust the cathode's distance from the electrolyte surface so that it is just out of contact with the liquid. Use an ultrasonic generator to provide an ultrasonic source at a frequency of 40 kHz and a power of 180 W. Turn on the ultrasonic switch to create an ultrasonic environment. After adjusting the anode and cathode positions, turn on the pulse power supply. Electrolysis proceeds in DC mode, with a deposition voltage of 110 V and a deposition time of 3 minutes. The power supply operates in linear boost mode. Once the deposition voltage is reached, turn on the lifting mechanism and uniformly lower the cathode to 2 cm below the electrolyte surface. Deposition proceeds at a rate of 2000 μm / s. After deposition, rinse and dry the sample.

[0038] Depend on Figure 2 and Figure 3 By comparison, it can be seen that after applying ultrasound, the protrusions on the surface of the Ni coating are reduced, the coating is smooth and dense, and the surface roughness is reduced.

[0039] Example 2: Ultrasonic-assisted cathode plasma electrolytic deposition of Zn-Ni alloy coating

[0040] A 20g / L sulfuric acid dilution was prepared, followed by the addition of 10g / L ZnSO4, 20g / L NiSO4·7H2O, and 5g / L polyethylene glycol, and mechanical stirring for 60 minutes. A 30mm×10mm×0.5mm Q235 carbon steel cathode and a 120mm×50mm×0.1mm platinum sheet anode were used. The samples were polished with 200#, 400#, 800#, 1200#, 1500#, and 2000# sandpaper in successive grades. The surface was degreased in an acetone solution ultrasonically for 5 minutes, activated by immersion in a 10% HCl solution for 1 minute, and then dried for later use.

[0041] Immerse the platinum anode 1 cm below the electrolyte surface. Adjust the horizontal distance between the cathode and cathode to 3 cm. Control the lifting mechanism and adjust the cathode's distance from the electrolyte surface so that it is just out of contact with the liquid. Use an ultrasonic generator with a frequency of 40 kHz and a power of 90 W to provide the ultrasonic source. Turn on the ultrasonic switch to create an ultrasonic environment. After adjusting the anode and cathode positions, turn on the pulse power supply. Electrolysis proceeds in DC mode with a deposition voltage of 110 V and a deposition time of 3 minutes. The power supply operates in linear boost mode. Once the deposition voltage is reached, turn on the lifting mechanism and uniformly lower the cathode to 2 cm below the electrolyte surface. Deposition proceeds at a rate of 1500 μm / s. After deposition, rinse and dry the sample.

[0042] Depend on Figure 4 It can be seen that compared with the case without ultrasound application, the current density during the preparation of the Zn-Ni alloy coating decreased by 20%, reducing energy consumption.

[0043] Example 3: Ultrasonic-assisted cathode plasma electrolytic deposition of Fe-Co-Ni alloy coating

[0044] A 20g / L sulfuric acid dilution was prepared, followed by the addition of 20g / L Fe2(SO4)3·xH2O, 5g / L CoSO4·7H2O, 20g / L NiSO4·7H2O, and 5g / L polyethylene glycol, and mechanical stirring for 60 minutes. A 30mm×10mm×0.5mm Q235 carbon steel cathode and a 120mm×50mm×0.1mm platinum sheet anode were used. The samples were polished with 200#, 400#, 800#, 1200#, 1500#, and 2000# sandpaper in successive grades. The surface was degreased in an acetone solution for 5 minutes of ultrasonication, activated by immersion in a 10% HCl solution for 1 minute, and then dried for later use.

[0045] Immerse the platinum anode 1 cm below the electrolyte surface. Then, adjust the horizontal distance between the cathode and anode to 3 cm. Control the lifting mechanism and adjust the cathode metal substrate's position from the electrolyte surface so that it is just out of contact with the liquid. Use an ultrasonic generator to provide an ultrasonic source at a frequency of 40 kHz and a power of 180 W. Turn on the ultrasonic switch to create an ultrasonic environment. After adjusting the anode and cathode positions, turn on the pulsed power supply. Electrolysis proceeds in pulsed mode with a deposition voltage of 110 V, a pulse duty cycle of 80%, a pulse frequency of 1500 Hz, and a deposition time of 3 minutes. The power supply operates in linear boost mode. Once the deposition voltage is reached, turn on the lifting mechanism and lower the cathode uniformly to 2 cm below the electrolyte surface. Deposition proceeds at a rate of 1500 μm / s. After deposition, rinse and dry the sample.

[0046] Compared with the case without ultrasound application, the current density during the preparation of the Fe-Co-Ni alloy coating decreased by 30%, reducing energy consumption.

[0047] Example 4: Ultrasonic-assisted cathode plasma cleaning of the oxide layer on the surface of Q235 carbon steel

[0048] A 15% NaHCO3 aqueous solution was prepared and mechanically stirred for 60 minutes. A Q235 carbon steel sheet with a surface oxide layer and a size of 30 mm × 10 mm × 0.5 mm was used as the cathode, and a platinum sheet with a size of 120 mm × 50 mm × 0.1 mm was used as the anode.

[0049] Immerse the platinum anode 1 cm below the electrolyte surface. Adjust the horizontal distance between the cathode and anode to 3 cm. Control the lifting mechanism and adjust the cathode's distance from the electrolyte surface so that it is just out of contact with the liquid. Use an ultrasonic generator with a frequency of 40 kHz and a power of 180 W. Turn on the ultrasonic switch to create an ultrasonic environment. After adjusting the anode and cathode positions, turn on the pulse power supply. Electrolysis proceeds in pulse mode with a cleaning voltage of 110 V, a pulse duty cycle of 70%, a pulse frequency of 1000 Hz, and a treatment time of 5 minutes. The power supply operates in linear boost mode. Once the deposition voltage is reached, turn on the lifting mechanism and lower the cathode uniformly to 2 cm below the electrolyte surface. Deposition proceeds at a rate of 1500 μm / s. After deposition, rinse and dry the sample.

[0050] Compared with the case without ultrasound application, ultrasound-assisted cathode plasma surface treatment has excellent removal efficiency of the surface oxide layer of Q235 carbon steel, and the residual coverage of the surface oxide layer after treatment is less than 1%.

[0051] Example 5: Ultrasonic-assisted cathode plasma cleaning of organic pollutants on the surface of 316L stainless steel

[0052] An 8% aqueous NaHCO₃ solution was prepared and mechanically stirred for 60 min. A 316L stainless steel sheet with surface organic contamination (30 mm × 10 mm × 0.5 mm) was used as the cathode, and a 120 mm × 50 mm × 0.1 mm platinum sheet was used as the anode.

[0053] Immerse the platinum anode 1 cm below the electrolyte surface. Adjust the horizontal distance between the cathode and anode to 3 cm. Control the lifting mechanism and adjust the cathode's distance from the electrolyte surface so that it is just out of contact with the liquid. Use an ultrasonic generator with a frequency of 40 kHz and a power of 180 W. Turn on the ultrasonic switch to create an ultrasonic environment. After adjusting the anode and cathode positions, turn on the pulse power supply. Electrolysis proceeds in pulse mode with a cleaning voltage of 150 V, a pulse duty cycle of 80%, a pulse frequency of 1000 Hz, and a treatment time of 5 minutes. The power supply operates in linear boost mode. Once the deposition voltage is reached, turn on the lifting mechanism and lower the cathode uniformly to 2 cm below the electrolyte surface. Deposition proceeds at a rate of 1500 μm / s. After deposition, rinse and dry the sample.

[0054] Compared with the case without ultrasound, ultrasound-assisted cathode plasma surface treatment has excellent removal efficiency of organic pollutants on the surface of 316L stainless steel, and the organic pollutants are completely removed.

Claims

1. A method for ultrasonic-assisted cathode plasma electrolytic deposition of coatings or surface treatment, characterized in that Ultrasonic-assisted deposition of coatings or surface treatment is performed in the following steps: Step 1: Dilute the inorganic acid with an appropriate amount of distilled water, then add the metal salt and water-soluble polymer, and mechanically stir for 15 to 60 minutes to prepare an electrolyte, which is used to deposit the coating; the electrolyte prepared with NaHCO3 aqueous solution is used for surface treatment; with the metal substrate as the cathode and the inert electrode as the anode, the metal substrate is polished in stages with 200#, 400#, 800#, 1200#, 1500#, and 2000# sandpaper, immersed in acetone solution and ultrasonically removed surface oil, immersed in acid solution for 1 to 3 minutes for activation, and dried for use; Step 2: Immerse the anode in the electrolyte, then adjust the horizontal distance between the cathode and the cathode to an appropriate distance, control the pulling device, and adjust the position of the cathode from the electrolyte surface so that it just does not touch the electrolyte; Turn on the ultrasound system and prepare the ultrasound environment; Step 3: Turn on the pulse power supply. When the deposition voltage is reached, turn on the pull-up device switch to make the cathode drop to the appropriate position at a uniform speed for deposition. After the deposition is completed, rinse and dry the sample. The device used in the method includes a pulse power supply (1), a water inlet (2), a water outlet (3), an anode (4), a cathode (5), an electrolytic cell (6), a support net (7), an ultrasonic generating system (8), cooling water (9), an electrolyte (10) and a pulling device (11); wherein the connection relationship between the various parts is as follows: the ultrasonic system (8) is fixed horizontally on the workbench, the support net (7) is used to support the electrolytic cell (6) and is immersed in the cooling water (9); the cooling water (9) is connected to an external circulation pump through the water inlet (2) and the water outlet (3); the anode (4) and the cathode (5) are vertically immersed in the electrolyte (10); and the pulling device (11) is located at a suitable position above the electrolytic cell (6) to control the up and down movement of the cathode.

2. The method for ultrasonic-assisted cathodic plasma electrolytic deposition of coatings or surface treatment according to claim 1, characterized in that: The metal salt is a nitrate, chloride, sulfate or carbonate of Fe, Co, Ni, Mo, Cd, Mn, Cu, Zn, Cr, Ag, Sn, Pt, Pd or Au; the electrolyte is prepared by metal salts of one, two or more elements.

3. The method for ultrasonic-assisted cathodic plasma electrolytic deposition coating or surface treatment according to claim 1, characterized in that: The inorganic acid is sulfuric acid, hydrochloric acid, or nitric acid; the water-soluble polymer is one or a combination of polyvinyl alcohol, polyethylene oxide, or polyvinyl pyrrolidone.

4. The method for ultrasonically assisted cathodic plasma electrolytic deposition of coatings or surface treatment according to claim 1, characterized in that: The anode is made of platinum, titanium or graphite inert electrode, and the cathode is made of carbon steel, stainless steel, aluminum alloy, magnesium alloy, titanium metal or alloy. The cathode and anode are placed in parallel with a horizontal spacing of 0.5 to 30 cm.

5. The method for ultrasonic-assisted cathodic plasma electrolytic deposition coating or surface treatment according to claim 1, characterized in that: The electrolysis process uses a pulse power supply, the frequency of the pulse power supply is controlled at 10~5000 Hz, the duty cycle is controlled at 10~90%, and the electrolysis voltage is controlled at a voltage 5~100 V higher than the arc starting voltage.

6. The method for ultrasonically assisted cathodic plasma electrolytic deposition of coatings or surface treatment according to claim 1, characterized in that: The ultrasound system is provided by a probe-type ultrasound generator or ultrasound machine, with an adjustable ultrasound power of 0.1 to 5 kW and an adjustable ultrasound frequency of 10 to 80 kHz.

7. The device used to implement the method according to claim 1 is characterized in that The invention comprises a pulse power supply (1), a water inlet (2), a water outlet (3), an anode (4), a cathode (5), an electrolytic cell (6), a support net (7), an ultrasonic generating system (8), cooling water (9), an electrolyte (10) and a pulling device (11); wherein the connection relationship of each part is as follows: the ultrasonic system (8) is fixed horizontally on the workbench, the support net (7) is used to support the electrolytic cell (6) and is immersed in the cooling water (9); the cooling water (9) is connected to the external circulation pump through the water inlet (2) and the water outlet (3); the anode (4) and the cathode (5) are vertically immersed in the electrolyte (10); the pulling device (11) is located at a suitable position above the electrolytic cell (6) to control the up and down movement of the cathode; the ultrasonic source of the ultrasonic generating system (8) is provided by a probe-type ultrasonic generator or an ultrasonic machine, the ultrasonic power is adjustable from 0.1 to 5 kW, and the ultrasonic frequency is adjustable from 10 to 80 kHz.

8. The device according to claim 7, characterized in that The pulling device (11) is insulated from the cathode via a polytetrafluoroethylene sleeve, and the pulling or lowering speed is automatically controlled by a controller.

9. The device according to claim 7, characterized in that The liquid level of the electrolyte (10) should be lower than the liquid level of the cooling water (9).

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