Preparation method of corrosion-resistant thermal control coating for magnesium alloy

Abstract

The present invention discloses a preparation method of a corrosion-resistant thermal control coating for magnesium alloy, which relates to the technical field of metal surface treatment. The preparation method includes: performing numerically controlled laser texturing treatment on the surface of the magnesium alloy with the oxide film removed; using the magnesium alloy after numerically controlled laser texturing treatment as the anode to perform micro-arc oxidation treatment to form a micro-arc oxidation coating on the surface of the magnesium alloy to improve the corrosion resistance and thermal control performance of the magnesium alloy; wherein, the electrolyte additive is nano-copper oxide treated by irradiation modification. By performing laser texturing treatment on the surface of the magnesium alloy, the present invention enables the surface of the magnesium alloy to have more regular and orderly pores, improves the surface activity and roughness of the magnesium alloy. On the one hand, it improves the thermal control performance of the micro-arc oxidation coating, and on the other hand, it improves the microstructure uniformity of the micro-arc oxidation coating, significantly reduces the porosity of the micro-arc oxidation coating, and improves the corrosion resistance of the micro-arc oxidation coating.

Description

Technical Field

[0001] The present invention relates to the technical field of metal surface treatment, and particularly to a preparation method of a corrosion-resistant and thermal control coating for magnesium alloy. Background Art

[0002] As the lightest structural metal material, magnesium alloy has good machinability, ductility, casting ability and good electromagnetic shielding properties. However, compared with other traditional metal materials, magnesium alloy has poor corrosion resistance. Therefore, improving the corrosion resistance of magnesium alloy is an urgent challenge to promote the application of magnesium alloy. Moreover, in recent years, the application of thermal control coating technology has been increasingly widespread in the fields of aerospace, electronic communication and automobile manufacturing, and the research on the thermal control performance of magnesium alloy has gradually become a hot topic.

[0003] In the prior art, there is little research on magnesium alloy coatings with both corrosion resistance and thermal control properties. Summary of the Invention

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art or related technologies.

[0005] For this purpose, the present invention provides a preparation method of a corrosion-resistant and thermal control coating for magnesium alloy, including:

[0006] Performing numerically controlled laser texturing treatment on the surface of the magnesium alloy after removing the oxide film;

[0007] Using the magnesium alloy after numerically controlled laser texturing treatment as the anode, performing micro-arc oxidation treatment to form a micro-arc oxidation coating on the surface of the magnesium alloy to improve the corrosion resistance and thermal control performance of the magnesium alloy;

[0008] Wherein, the electrolyte additive for the micro-arc oxidation treatment is nano-copper oxide modified by irradiation; the nano-copper oxide modified by irradiation has a particle size of 50 nm to 700 nm and an addition concentration in the electrolyte of 5 g / L to 20 g / L.

[0009] Further, the numerically controlled laser texturing treatment includes:

[0010] Designing a laser texturing pattern, generating the processing path and process of the numerically controlled laser texturing treatment, and then performing the numerically controlled laser texturing treatment by using the method of laser galvanometer scanning.

[0011] Further, for the laser galvanometer scanning, the galvanometer frequency is 9000 Hz to 12000 Hz, the laser power is 50 W to 200 W, the laser scanning speed is 5 mm / s to 20 mm / s, and the laser pulse frequency is 15 Hz to 30 Hz.

[0012] Further, the micro-arc oxidation treatment includes: using the magnesium alloy after numerically controlled laser texturing as the anode; using a graphite plate as the cathode; and using an electrolyte containing 5 g / L to 7 g / L of NaF, 25 g / L to 35 g / L of Na2SiO3, and 4 g / L to 6 g / L of NaOH, with deionized water as the solvent.

[0013] Further, the irradiation modification treatment includes: using a Bi ion beam with an energy of 6 MeV / u to 8 MeV / u as the irradiation source, with an irradiation time of 900 s to 1000 s and an irradiation flux rate of 10 ion / (s·cm²). 32+ Ion beam, irradiation time is 900 S~1000 S, irradiation flux rate is 10 5 ion / (s·cm 2 )

[0014] Furthermore, the nano-copper oxide after the irradiation modification treatment has a particle size of 50 nm to 100 nm and an addition concentration in the electrolyte of 8 g / L to 12 g / L.

[0015] Further, for the micro-arc oxidation treatment, a constant current control power supply is used, with a current density range of 3 A / dm² to 5 A / dm², a voltage range of 420 V to 480 V, a frequency of 200 Hz to 300 Hz, a duty cycle of 30% to 40%, and a micro-arc oxidation time of 5 min to 30 min. 2 ~5 A / dm 2 , voltage range is 420 V~480 V, frequency is 200 Hz~300 Hz, duty cycle is 30%~40%, micro-arc oxidation time is 5min~30 min.

[0016] Further, during the micro-arc oxidation treatment, the electrolyte is stirred at a stirring speed of 200 r / min to 500 r / min, and the temperature of the electrolyte is kept below 40 °C by cooling.

[0017] Compared with the prior art, the present invention has at least the following beneficial effects:

[0018] The preparation method of the corrosion-resistant and thermal control coating for magnesium alloy provided by the present invention. The pre-treatment of laser texturing improves the surface activity and roughness of the magnesium alloy. The surface of the magnesium alloy after laser texturing has more regular and orderly pores, which enables more nano-particles to be incorporated into the coating during the micro-arc oxidation process, further improving the thermal control performance of the coating. In addition, the laser texturing treatment orderly adjusts the surface structure of the magnesium alloy. On the one hand, it improves the growth rate of the micro-arc oxidation coating, reduces the energy consumed during the micro-arc oxidation process, and on the other hand, it improves the microstructural uniformity of the micro-arc oxidation coating, significantly reducing the porosity of the micro-arc oxidation coating. The coating has the advantages of hydrophobicity, low surface roughness, excellent corrosion resistance, wear resistance, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1The metallographic morphology of magnesium alloy after being processed by different numerical control laser texturing parameters provided by the embodiments of the present application; among them,

[0020] Figure 1 a is the metallographic morphology of magnesium alloy with a galvanometer frequency < 9000 Hz provided by the embodiments of the present application;

[0021] Figure 1 b is the metallographic morphology of magnesium alloy with a galvanometer frequency > 12000 Hz provided by the embodiments of the present application;

[0022] Figure 1 c is the metallographic morphology of magnesium alloy with a laser power < 50 W provided by the embodiments of the present application;

[0023] Figure 1 d is the metallographic morphology of magnesium alloy with a laser power > 200 W provided by the embodiments of the present application;

[0024] Figure 1 e is the metallographic morphology of magnesium alloy with a scanning speed < 5 mm / s provided by the embodiments of the present application;

[0025] Figure 1 f is the metallographic morphology of magnesium alloy with a scanning speed > 20 mm / s provided by the embodiments of the present application;

[0026] Figure 1 g is the metallographic morphology of magnesium alloy with a pulse frequency < 15 Hz provided by the embodiments of the present application;

[0027] Figure 1 h is the metallographic morphology of magnesium alloy with a pulse frequency > 30 Hz provided by the embodiments of the present application;

[0028] Figure 1 i is the first metallographic morphology of magnesium alloy with better experimental parameters provided by the embodiments of the present application;

[0029] Figure 1 j is the second metallographic morphology of magnesium alloy with better experimental parameters provided by the embodiments of the present application.

[0030] Figure 2 It is the micro-arc oxidation boosting curve provided by Embodiment 1 of the present application and Comparative Example 4.

[0031] Figure 3 It is the metallographic morphology of magnesium alloy after laser remelting treatment in Comparative Example 1 of the present application and the metallographic morphology of magnesium alloy after laser texturing treatment in Comparative Example 2.

[0032] Figure 4 It is the scanning electron microscope image of the surface morphology of the magnesium alloy corrosion-resistant thermal control coating provided by Embodiment 1 of the present application.

[0033] Figure 5Scanning electron microscope images of the surface morphology of the corrosion-resistant thermal control coatings for magnesium alloys provided in Comparative Examples 1-6 of this application.

[0034] Figure 6 Absorptance graphs of the corrosion-resistant thermal control coatings for magnesium alloys provided in Example 1 and Comparative Examples 1-6 of this application.

[0035] Figure 7 Emittance graphs of the corrosion-resistant thermal control coatings for magnesium alloys provided in Example 1 and Comparative Examples 1-6 of this application.

[0036] Figure 8 Contact angle graphs of the micro-arc oxidation coatings for magnesium alloys provided in Comparative Examples 1-4 of this application.

[0037] Figure 9 Contact angle graphs of the corrosion-resistant thermal control coatings for magnesium alloys provided in Example 1 of this application.

[0038] Figure 10 Impedance graphs of the micro-arc oxidation coatings for magnesium alloys provided in Comparative Examples 1-4 of this application.

[0039] Figure 11 Impedance graphs of the corrosion-resistant thermal control coatings for magnesium alloys provided in Example 1 of this application. Detailed implementation manners

[0040] To better understand the above technical solutions, the technical solutions of the present invention will be described in detail below through specific examples.

[0041] An embodiment of the present invention provides a method for preparing a corrosion-resistant thermal control coating for a magnesium alloy, including:

[0042] Performing numerically controlled laser texturing treatment on the surface of the magnesium alloy with the oxide film removed;

[0043] Using the magnesium alloy after numerically controlled laser texturing treatment as the anode, performing micro-arc oxidation treatment to form a micro-arc oxidation coating on the surface of the magnesium alloy to improve the corrosion resistance and thermal control performance of the magnesium alloy; wherein, the electrolyte additive for the micro-arc oxidation treatment is nano-copper oxide modified by irradiation.

[0044] The preparation method of the corrosion-resistant thermal control coating for magnesium alloy provided by the embodiment of the present invention is a method for preparing a corrosion-resistant thermal control coating for magnesium alloy based on laser texturing pretreatment-assisted micro-arc oxidation technology. The laser texturing pretreatment improves the surface activity and roughness of the magnesium alloy. The surface of the magnesium alloy after laser texturing treatment has more regular and orderly holes, which enables more nanoparticles to be incorporated into the coating during the micro-arc oxidation process, and can further improve the thermal control performance of the coating. In addition, the laser texturing treatment orderly adjusts the surface structure of the magnesium alloy. On the one hand, it improves the growth rate of the micro-arc oxidation coating and reduces the energy consumed during the micro-arc oxidation process. On the other hand, it improves the microstructure uniformity of the micro-arc oxidation coating, significantly reduces the porosity of the micro-arc oxidation coating, and the coating has the advantages of hydrophobicity, low surface roughness, excellent corrosion resistance, wear resistance, etc.

[0045] In a feasible implementation manner, the numerical control laser texturing treatment includes:

[0046] Design the laser texturing pattern, generate the processing path and process of the numerical control laser texturing treatment, and then use the method of laser galvanometer scanning to perform the numerical control laser texturing treatment.

[0047] Specifically, first, it is necessary to precisely design the laser texturing pattern. Use CAD software to design the geometric shape and size. The pattern can be selected as simple geometric shapes or patterns such as squares, circles, diamonds, and wavy lines. The area of the diamond and square can be 30 square micrometers - 100 square micrometers. During the texturing process, ensure that the material surface is flat without obvious undulations or bumps. Subsequently, use CAM software to generate the processing path and process of the numerical control laser texturing treatment, and then use the method of laser galvanometer scanning to perform the numerical control laser texturing treatment.

[0048] In a feasible implementation manner, for laser galvanometer scanning, the galvanometer frequency is 9000 Hz - 12000 Hz, the laser power is 50 W - 200 W, the laser scanning speed is 5 mm / s - 20 mm / s, and the laser pulse frequency is 15 Hz - 30 Hz.

[0049] Specifically, if the frequency of the laser galvanometer is too high or too low, it will cause deviations in the positioning of the light beam. When the frequency of the galvanometer is too high, the high-frequency vibration may cause the position of the galvanometer to shift or become misaligned, affecting the accurate control and positioning of the light beam, resulting in deviations in the pattern. The unstable vibration of the low-frequency galvanometer will reduce the stability of the light beam, and the beam may shake or drift. The experiment found that, taking the laser texturing pattern designed as a diamond as an example, when the galvanometer frequency is less than 9000 Hz, the laser cannot produce a diamond according to the set pattern, and defects will occur during operation; when the galvanometer frequency is greater than 12000 Hz, there will be too many dots. In addition, when the laser power is less than 50 W, the laser will have defects, and some positions will have defects due to insufficient laser power; when the laser power is greater than 200 W, excessive ablation will occur. Excessive and low scanning speeds and pulse frequencies will also affect the preparation of graphics. The experimental results are listed in Tables 1 and Figure 1 a- Figure 1 As shown in j, it can be seen that Figure 1 a- Figure 1 h cannot effectively prepare diamond patterns. Figure 1 i and Figure 1 j effectively prepared the diamond pattern, which is the optimal experimental parameter.

[0050] Table 1

[0051]

[0052] In a feasible implementation, the micro-arc oxidation treatment includes: a magnesium alloy treated by CNC laser texturing is used as an anode; a graphite plate is used as a cathode; the electrolyte is: NaF 5 g / L~7 g / L, Na2SiO3 25 g / L~35 g / L, NaOH 4 g / L~6 g / L, the solvent is deionized water, and the electrolyte additive is nano copper oxide treated by irradiation. Among them, the irradiation modification treatment includes: the irradiation source is Bi 6 MeV / u~8 MeV / u 32+ Ion beam, irradiation time is 900 s~1000 s, irradiation flux rate is 10 5 ion / (s·cm 2 );

[0053] The particle size of nano copper oxide is 50 nm to 700 nm, and the concentration added in the electrolyte is 5 g / L to 20 g / L. Preferably, the particle size of nano copper oxide is 50 nm to 100 nm, and the concentration added in the electrolyte is 8 g / L to 12 g / L.

[0054] Specifically, by in-situ doping nanoparticles with different bandgap energies into the micro-arc oxidation electrolyte, the thermal control performance of the micro-arc oxidation coating is improved. The surface of the magnesium alloy after numerically controlled laser texturing has more regular and ordered holes, which enables more nanoparticles to be incorporated into the coating during the micro-arc oxidation process, further improving the thermal control performance of the coating. Nano-copper oxide is a semiconductor material belonging to narrow-bandgap semiconductors, with a bandgap of approximately 1.2 to 1.9 electron volts (eV). After irradiation, the bandgap of nano-copper oxide drops to between 0.5 and 0.6 electron volts (eV), making it more suitable for absorbing light in the visible and near-infrared spectral ranges. The absorption usually starts from about 600 nm and continues over a longer wavelength range. Nano-copper oxide modified by irradiation is more conducive to improving the thermal control performance of the coating. Previous studies have not used nano-copper oxide particles modified by irradiation as additives for thermal control coatings. Taking nano-CuO modified by irradiation as an electrolyte additive, the effects of the addition amount and particle size of nano-CuO modified by irradiation on the coating were investigated as follows: When the addition concentration of nano-CuO modified by irradiation is less than 5 g / L, it will lead to a significant decrease in the doping content on the coating surface, affecting the thermal control effect of the coating; when the addition concentration of nano-CuO modified by irradiation is greater than 20 g / L, too much nano-CuO modified by irradiation in the solution will affect the conductivity of the electrolyte and the formation of the micro-arc oxidation film. In addition, excessive nano-CuO modified by irradiation agglomerates on the substrate surface, causing a burning phenomenon on the coating surface. Therefore, the preferred addition concentration of nano-CuO modified by irradiation in the electrolyte is 8 g / L to 12 g / L. In addition, experiments were also carried out on the particle size selection of nano-CuO modified by irradiation: Nano-CuO modified by irradiation with particle size ranges of 50 nm - 100 nm, 200 nm - 300 nm, and 600 nm - 700 nm were selected, with a purity of ≥99.9%. Among them, nano-CuO modified by irradiation with a particle size of 50 nm - 100 nm has better dispersion in the solution. Under the same micro-arc oxidation parameter conditions, through EDS surface scanning, it was found that when 10 g / L of nano-copper oxide modified by irradiation with a particle size of 50 nm - 100 nm was added to the electrolyte, the Cu element content on the coating surface was 9.2 at.%; when 10 g / L of nano-copper oxide modified by irradiation with a particle size of 200 nm - 300 nm was added to the electrolyte, the Cu element content on the coating surface was 6.1 at.%; when 10 g / L of nano-copper oxide modified by irradiation with a particle size of 600 nm - 700 nm was added to the electrolyte, the Cu element content on the coating surface was 4.3 at.%. Therefore, the preferred particle size of nano-copper oxide modified by irradiation is 50 nm to 100 nm.

[0055] The experiment investigated the influence of the electrolyte composition (the solvent was deionized water in all cases) on the properties of the corrosion-resistant thermal control coating for magnesium alloys. Among them, the micro-arc oxidation parameters were: voltage 450 V, current density 4 A / dm 2 , frequency 200 Hz, duty cycle 30%, and the micro-arc oxidation treatment lasted for 10 min. As shown in Table 2, it can be seen that the preferred electrolyte was: 6 g / L of NaF, 30 g / L of Na2SiO3, 5 g / L of NaOH, and the electrolyte additive was nano-copper oxide treated by irradiation modification, with an addition amount of 10 g / L. At this time, the particles in the coating were doped evenly, the coating was relatively thick, the sparks were uniform and dense during the film-forming process, and the pore sizes on the coating surface were uniform.

[0056] Table 2

[0057]

[0058] In a feasible implementation manner, a constant-current control power supply was used for the micro-arc oxidation treatment, the current density range was 3 A / dm 2 ~5 A / dm 2 , the voltage range was 420 V~480 V, the frequency was 200 Hz~300 Hz, the duty cycle was 30%~40%, and the micro-arc oxidation time was 5 min~30 min.

[0059] It was found in the experiment that when the micro-arc oxidation voltage was less than 420 V, the coating thickness was relatively low; when the voltage exceeded 480 V, intense discharge would cause an increase in the pore size on the coating surface; therefore, the voltage range was controlled at 420 V~480 V. When the current density was less than 3 A / dm 2 , no film could be formed; when the current density was higher than 5 A / dm 2 , due to the too high current, the coating surface was prone to be loose and porous.

[0060] Specifically, the micro-arc oxidation frequency and duty cycle usually need to be changed together. When the frequency is too high and the duty cycle is too low, the energy during each pulse period is not sufficient to maintain a strong enough discharge process, affecting the coating formation efficiency and integrity. When the frequency is too low and the duty cycle is too high, the formed oxide layer is incomplete and the quality deteriorates, affecting the wear resistance and corrosion resistance of the oxide film. When the frequency is too high and the duty cycle is too large, it will lead to over-oxidation, making the texture of the oxide layer too rough and the surface roughness increase, reducing the surface quality. It was obtained from the experiment of this application that for the preferred micro-arc oxidation treatment, the frequency was 200 Hz~300 Hz and the duty cycle was 30%~40%. In addition, if the micro-arc oxidation time was too short, less than 5 min, the coating was too thin, resulting in a decrease in the particle doping amount in the coating, affecting the thermal control and corrosion resistance of the coating. If the micro-arc oxidation time was greater than 30 min, the oxidation time of the coating was too long, resulting in a loose structure and deteriorated quality of the oxide layer, affecting the hardness, wear resistance and corrosion resistance of the oxide layer.

[0061] In a feasible implementation, during the micro-arc oxidation process, the electrolyte is stirred at a stirring speed of 200 r / min to 500 r / min, and the temperature of the electrolyte is cooled to below 40 °C.

[0062] Specifically, stirring during the micro-arc oxidation process is to better disperse the nano-copper oxide particles treated by irradiation modification throughout the electrolyte. When the speed is lower than 200 r / min, due to the large self-weight of the particles, a large number of particles may deposit at the bottom of the solution, resulting in a decrease in the particle concentration in the solution. When the rotation speed is higher than 500 r / min, due to the too high rotation speed, the particles cannot be adsorbed on the substrate surface during the micro-arc oxidation process, affecting the particle doping amount in the coating. When the temperature of the electrolyte is higher than 40 °C, the too high solution temperature will affect the pH value and chemical reaction rate of the solution, resulting in incomplete formation or quality degradation of the oxide layer, and reducing the hardness and adhesion of the oxide layer.

[0063] Example 1 A preparation method of a corrosion-resistant and thermal control coating for magnesium alloy

[0064] The specific steps are as follows:

[0065] (1) Sample pretreatment: The magnesium alloy sample is wire-cut according to the size of 40 mm × 40 mm × 5 mm. The surface of the magnesium alloy substrate is polished successively with water sandpapers with roughnesses of 240 #, 400 #, 600 #, 800 #, 1000 #, and 2000 # until the surface of the magnesium alloy substrate is smooth and flat, then rinsed with alcohol and dried for standby.

[0066] (2) Laser texturing treatment: The pretreated sample is subjected to numerical control laser texturing treatment, using a galvanometer scanner, with a galvanometer frequency of 12000 Hz, a laser power of 100 W, a scanning speed of 10 mm / s, and a pulse frequency of 20 Hz. The diamond shape is designed using AutoCAD software and then input into the laser machine tool for processing.

[0067] (3) Micro-arc oxidation treatment: The sample obtained after laser texturing is used as the anode, and the graphite plate is used as the cathode. The micro-arc oxidation electrolyte is poured into the electrolytic cell, and then micro-arc oxidation treatment is carried out. The micro-arc oxidation power supply adopts constant current control, and the power supply voltage is set to 450 V, and the current density is 4 A / dm 2, with a frequency of 200 Hz, a duty cycle of 30%, and micro-arc oxidation treatment for 10 min, a corrosion-resistant and thermal control micro-arc oxidation coating was prepared on the surface of the magnesium alloy. Among them, the micro-arc oxidation electrolyte was: 6 g / L of NaF, 30 g / L of Na2SiO3, 5 g / L of NaOH, and 10 g / L of nano-CuO. The solvent was deionized water. (The particle size of the nano-CuO modified by irradiation was 50 nm to 100 nm). During the preparation process, an electronically controlled stirrer was installed in the electrolytic cell, and the stirring speed was 400 r / min. At the same time, indirect cooling was carried out in the electrolytic cell, and the cooling temperature was set at 25 °C.

[0068] Comparative Example 1 A method for preparing a corrosion-resistant and thermal control coating on magnesium alloy

[0069] The specific steps are as follows:

[0070] (1) Sample pretreatment: The same as in Example 1.

[0071] (2) Laser melting treatment: The pretreated sample was subjected to laser melting treatment with a laser power of 500 W, a scanning speed of 5 mm / s, and a pulse frequency of 30 Hz.

[0072] (3) Micro-arc oxidation treatment: The same as in Example 1.

[0073] Comparative Example 2 A method for preparing a corrosion-resistant and thermal control coating on magnesium alloy

[0074] The specific steps are as follows:

[0075] (1) Sample pretreatment: The same as in Example 1.

[0076] (2) Laser texturing treatment: The pretreated sample was subjected to numerically controlled laser texturing treatment. A galvanometer scan was used, with a galvanometer frequency of 15000 Hz, a laser power of 200 W, a scanning speed of 5 mm / s, and a pulse frequency of 10 Hz. The diamond shape was designed using AutoCAD software and then input into the laser machine tool for processing.

[0077] (3) Micro-arc oxidation treatment: The same as in Example 1.

[0078] Comparative Example 3 A method for preparing a corrosion-resistant and thermal control coating on magnesium alloy

[0079] The specific steps are as follows:

[0080] (1) Sample pretreatment: The same as in Example 1.

[0081] (2) Laser texturing treatment: The same as in Example 1.

[0082] (3) Micro-arc oxidation treatment: Different from Example 1, in the micro-arc oxidation electrolyte, NaF is 15 g / L, Na2SiO3 is 40 g / L, NaOH is 10 g / L, and CuO is 10 g / L.

[0083] Comparative Example 4 A method for preparing a corrosion-resistant thermal control coating for magnesium alloy

[0084] The specific steps are as follows:

[0085] (1) Sample pretreatment: The same as in Example 1.

[0086] (2) Micro-arc oxidation treatment: The same as in Example 1.

[0087] Comparative Example 5 A method for preparing a corrosion-resistant thermal control coating for magnesium alloy

[0088] The specific steps are as follows:

[0089] (1) Sample pretreatment: The same as in Example 1.

[0090] (2) Laser texturing and micro-arc oxidation are carried out simultaneously: During the process of preparing the coating by micro-arc oxidation, the coating is simultaneously subjected to laser texturing treatment using a laser. The laser texturing treatment parameters are the same as those in Example 1, and the micro-arc oxidation parameters are the same as those in Example 1.

[0091] Comparative Example 6 A method for preparing a corrosion-resistant thermal control coating for magnesium alloy

[0092] The specific steps are as follows:

[0093] (1) Sample pretreatment: The same as in Example 1.

[0094] (2) Micro-arc oxidation treatment: The pretreated sample is directly subjected to micro-arc oxidation treatment, and the micro-arc oxidation treatment parameters are the same as those in Example 1.

[0095] (3) Laser texturing treatment: The coating is subjected to laser treatment using a laser, and the laser treatment parameters are the same as those in Example 1.

[0096] Results and discussion:

[0097] Roughness and wear rate tests of the examples and comparative examples: After preparation, the samples were rinsed with deionized water and dried. The roughness of the samples was measured using an SJ-310 roughness meter produced by Mitutoyo Corporation of Japan, and the wear rate of the samples was measured using an H2R-2M reciprocating friction and wear tester produced by Lanzhou Zhongke Kaihua Technology Development Co., Ltd. The results are shown in Table 3. As can be seen from Table 3, after the numerical control laser texturing treatment in Example 1, the roughness of the micro-arc oxidation coating was significantly reduced, while the roughness of the coatings provided in Comparative Examples 1-6 was relatively high. When using the H2R-2M reciprocating friction and wear tester produced by Lanzhou Zhongke Kaihua Technology Development Co., Ltd. to test the samples, it was found that the wear rate of the coating provided in Example 1 was relatively low. Since the coating in Example 1 was smoother and contained more doped CuO, the coating was more wear-resistant.

[0098] Table 3 Roughness and wear rate of magnesium alloy samples prepared in examples and comparative examples

[0099]

[0100] In the cases of Example 1 and Comparative Example 4, the micro-arc oxidation voltage boosting curves are shown in Figure 2 . After the numerical control laser texturing treatment, the micro-arc oxidation voltage boosts faster, which improves the growth rate of the micro-arc oxidation coating and reduces the energy consumed during the micro-arc oxidation process; while when performing micro-arc oxidation alone, the voltage boosting is slower during the coating preparation process, consuming more energy. The metallographic morphology of the magnesium alloy after the numerical control laser texturing treatment in Example 1 is in the shape of regular rhombus ( Figure 1 i), while the surface of the laser remelting in Comparative Example 1 is a non-smooth molten surface ( Figure 3 Comparative Example 1). In Comparative Example 2, when the laser power and pulse frequency are increased, the laser pattern cannot be in a regular shape ( Figure 3 Comparative Example 2), and the too high laser power results in deeper laser ablation pits ( Figure 5 Comparative Example 2). The corrosion-resistant and thermal control coating of the magnesium alloy based on the pre-treatment of laser texturing + micro-arc oxidation in Example 1 ( Figure 4 ) has a lower surface porosity, significantly lower than the micro-arc oxidation coatings provided in Comparative Examples 1-6 ( Figure 5 ). From Figure 5It can be seen that: in Comparative Example 1, laser remelting + micro-arc oxidation slightly improved the coating morphology; for the coating of Comparative Example 2 with laser texturing + micro-arc oxidation, due to the too high laser power and pulse frequency during laser texturing, the prepared micro-arc oxidation coating had a higher surface porosity and larger pores; in Comparative Example 3, when the micro-arc oxidation coating formula was changed, due to the relatively high content of fluoride and sodium hydroxide in the solution, a large number of cracks existed on the coating surface and the pores were the largest; Comparative Example 4 was the micro-arc oxidation coating of magnesium alloy without pretreatment, and there were also a large number of micropores on its surface with relatively large pore diameters; Comparative Example 5 was to prepare a coating by combining laser treatment during the micro-arc oxidation process. The surface porosity of the coating was relatively high, indicating that laser treatment during the micro-arc oxidation process did not affect the growth morphology of the coating. The main reason for the analysis was that diffuse reflection would occur when the laser irradiated into the electrolyte, seriously affecting the laser efficiency; Comparative Example 6 was to perform laser treatment on the micro-arc oxidation coating. After treatment, the surface did not show a regular shape and ablation phenomenon occurred, but the coating pores were not effectively sealed and the coating porosity was relatively high.

[0101] From Figure 6 and Figure 7 It can be seen that the absorptivities of Comparative Examples 1 - 6 were 0.63, 0.57, 0.47, 0.41, 0.39, and 0.51 respectively, and the emissivities were 0.85, 0.84, 0.85, 0.85, 0.85, 0.84. While the absorptivity of Example 1 was 0.96 and the emissivity was 0.96. This indicated that the laser texturing pretreatment + micro-arc oxidation treatment in Example 1 effectively improved the thermal control performance of the coating and successfully prepared a high-absorption and high-emission thermal control coating.

[0102] From Figure 8 and Figure 9 It can be seen that due to the relatively high surface porosity of the micro-arc oxidation coatings provided by Comparative Examples 1 - 4, the contact angles of the coatings were relatively low, showing hydrophilicity. While for the micro-arc oxidation coating provided by Example 1, due to the reduction of its surface porosity, the coating showed hydrophobicity and the contact angle reached 117°.

[0103] From Figure 10 and Figure 11 It can be seen that the impedance value of the magnesium alloy micro-arc oxidation coating with laser texturing + micro-arc oxidation in Example 1 was significantly higher than that of Comparative Examples 1 - 4, indicating that the preparation method of the corrosion-resistant thermal control coating of magnesium alloy in Example 1 effectively improved the corrosion resistance of the coating.

[0104] It is easily understandable to those skilled in the art that, on the premise of no conflict, the above-mentioned advantageous ways can be freely combined and superimposed. The above are only the preferred embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present application shall be included within the protection scope of the present application. The above is only the preferred implementation manner of the present application. It should be noted that for those of ordinary skill in the art in this technical field, several improvements and variations can be made without departing from the technical principle of the present application, and these improvements and variations should also be regarded as within the protection scope of the present application.

Claims

1. A method for preparing a corrosion-resistant thermal control coating of a magnesium alloy, characterized in that: include: Perform CNC laser texturing on the surface of magnesium alloy with oxide film removed; The CNC laser texturing process comprises: designing a laser texturing pattern, generating a processing path and a processing process of the CNC laser texturing process, and then performing the CNC laser texturing process by using a laser galvanometer scanning method; the laser galvanometer scanning has a galvanometer frequency of 9000 Hz to 12000 Hz, a laser power of 50 W to 200 W, a laser scanning speed of 5 mm / s to 20 mm / s, and a laser pulse frequency of 15 Hz to 30 Hz; The magnesium alloy treated by CNC laser texturing is used as the anode to perform micro-arc oxidation treatment to form a micro-arc oxidation coating on the surface of the magnesium alloy to improve the corrosion resistance and thermal control properties of the magnesium alloy; The electrolyte for micro-arc oxidation treatment is: NaF 5 g / L~7 g / L, Na2SiO3 25 g / L~35 g / L, NaOH 4 g / L~6 g / L, and the solvent is deionized water; the electrolyte additive for micro-arc oxidation treatment is nano copper oxide modified by irradiation; the nano copper oxide modified by irradiation has a particle size of 50 nm~700 nm and an addition concentration of 5 g / L~20 g / L in the electrolyte; the irradiation modification treatment includes: the irradiation source is Bi 6 MeV / u~8 MeV / u 32+ Ion beam, irradiation time is 900 s~1000 s, irradiation flux rate is 10 5 ion / (s·cm 2 ).

2. The method for preparing the corrosion-resistant thermal control coating of magnesium alloy according to claim 1, characterized in that: The nano copper oxide modified by radiation has a particle size of 50 nm to 100 nm and is added to the electrolyte at a concentration of 8 g / L to 12 g / L.

3. The method for preparing the corrosion-resistant thermal control coating of magnesium alloy according to claim 1 or 2, characterized in that: The micro-arc oxidation treatment uses a constant current control power supply with a current density range of 3 A / dm 2 ~5 A / dm 2 , the voltage range is 420 V~480 V, the frequency is 200 Hz~300 Hz, the duty cycle is 30%~40%, and the micro-arc oxidation time is 5 min~30 min.

4. The method for preparing the corrosion-resistant thermal control coating of magnesium alloy according to claim 3, characterized in that: During the micro-arc oxidation treatment, the electrolyte is stirred at a speed of 200 r / min to 500 r / min, and the electrolyte temperature is cooled to below 40°C.

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