Preparation method of nickel-based nano pearl powder composite electrodeposited layer on surface of AZ91D magnesium alloy

Abstract

The present application belongs to the technical field of surface treatment of metal base material and biomass particle composite electrodeposition, and discloses a preparation method of AZ91D magnesium alloy surface nickel base nano pearl powder composite electrodeposition layer. The cathode adopts a magnesium alloy sample after chemical pre-deposition, the anode adopts a nickel plate with mass fraction greater than 99%, both are connected to the negative pole and the positive pole of the pulse power source respectively, are immersed in the pre-configured electrodeposition liquid and placed in an ultrasonic generator for electrodeposition, and the ultrasonic generator works in a variable frequency mode. The formed deposition layer has smooth appearance, compact and uniform, the hardness is increased by 20 times to 22 times compared with the magnesium alloy substrate, increased by 1.3 times to 1.6 times compared with the pure nickel layer on the magnesium alloy surface electrodeposition, and the self-corrosion current density is decreased by 2 orders of magnitude to 3 orders of magnitude compared with the magnesium alloy substrate.

Description

Technical Field

[0001] This invention belongs to the field of surface treatment technology of composite electrodeposition of metal-based materials and biomass particles. Specifically, it relates to a method for preparing a nickel-based nano-pearl powder composite electrodeposition layer on the surface of AZ91D magnesium alloy. More specifically, it relates to a method for preparing a high-hardness, highly corrosion-resistant nickel-based nano-pearl powder composite electrodeposition layer on the surface of AZ91D magnesium alloy. Background Technology

[0002] Magnesium alloys possess numerous excellent properties, including high specific strength and stiffness, good damping performance, good biocompatibility, large hydrogen storage capacity, and good recyclability, making them one of the most promising energy and biomedical materials of the 21st century. Due to their superior lightweight characteristics, magnesium alloys have significant application value in industrial manufacturing and green development, significantly reducing equipment energy consumption and alleviating the energy crisis. my country, as the world's largest producer and holder of magnesium resources, holds a dominant position in the international market. However, despite these superior properties, the practical application of magnesium alloys is limited by their poor corrosion resistance. Magnesium alloys are chemically reactive, easily forming a loose oxide film on their surface, which cannot effectively prevent further corrosion. Furthermore, magnesium alloys have relatively low hardness and belong to a hexagonal close-packed (HCP) crystal structure, resulting in relatively weak interatomic bonding. Their lower bond energies make atoms more prone to displacement under external forces, leading to easy deformation and manifesting as low hardness.

[0003] Composite electrodeposition refers to a method in which one or more particles are added to a deposition solution and co-deposited with a matrix metal under the action of an electric field. The prepared nanocomposite layer has many properties that pure metals and alloys do not possess, such as good hardness, wear resistance, corrosion resistance, and high-temperature oxidation resistance. However, in the electrodeposition process, ceramic particles are expensive, cannot be recycled, and may cause environmental pollution during recycling. Summary of the Invention

[0004] To overcome the shortcomings of existing technologies, this invention provides a method for preparing a nickel-based nano-pearl powder composite electrodeposition layer on the surface of AZ91D magnesium alloy. Specifically, it is adapted to the electrodeposition solution of AZ91D magnesium alloy and the variable frequency power ultrasonic pulse electrodeposition process. In the ultrasonic generator, the agglomeration of particles during the composite electrodeposition process is reduced by adjusting the ultrasonic frequency and ultrasonic power. The resulting deposition layer has a smooth, dense and uniform appearance, and its hardness is 20 to 22 times higher than that of the magnesium alloy substrate and 1.3 to 1.6 times higher than that of the pure nickel electrodeposition layer on the magnesium alloy surface. The self-corrosion current density is 2 to 3 orders of magnitude lower than that of the magnesium alloy substrate and is also lower than that of the pure nickel electrodeposition layer on the magnesium alloy surface.

[0005] The above-mentioned objective of this invention is achieved through the following technical solution: A method for preparing a nickel-based nano-pearl powder composite electrodeposition layer on the surface of AZ91D magnesium alloy, wherein the cathode is a pre-deposited magnesium alloy sample and the anode is a nickel plate with a mass fraction greater than 99%, which are respectively connected to the negative and positive terminals of a pulse power supply, immersed in a pre-prepared electrodeposition solution and placed in an ultrasonic generator for electrodeposition, the ultrasonic generator operating in a frequency conversion mode. The electrodeposition solution has the following specific composition: nickel sulfate 110 g / L to 130 g / L, ammonium citrate 8 g / L to 12 g / L, ammonium bifluoride 35 g / L to 50 g / L, sodium saccharin 1 g / L to 3 g / L, sodium dodecyl sulfate 0.1 g / L to 0.2 g / L, Tween 20 5 g / L to 15 mL / L, and pearl powder 1 g / L to 9 g / L; the pearl powder size is 50 nm to 300 nm.

[0006] A nickel-based pearl powder composite electrodeposition layer was prepared by co-depositing pearl powder and nickel matrix metal on the surface of a magnesium alloy substrate.

[0007] In the electrodeposition solution, nickel sulfate is used as the main salt, forming a stable complex with ammonium citrate. Ammonium citrate regulates the concentration of free nickel ions in the solution through complexation, synergistically enhancing the stability and uniformity of the plating solution. Ammonium bifluoride possesses both corrosion inhibition and activation functions, working synergistically with the complexation system to effectively inhibit corrosion of the magnesium alloy substrate in the plating solution while promoting surface reactions, ensuring a continuous and stable deposition process. Furthermore, sodium saccharin and sodium dodecyl sulfate are used in combination, synergistically refining grain size, improving surface wetting, and effectively reducing the porosity of the deposited layer. Together with the aforementioned main salt, complexing agent, and corrosion inhibitor, they construct a chemical nickel plating system characterized by uniform deposition, strong adhesion, and few defects.

[0008] By investigating different amounts of pearl powder added (0 g / L, 1 g / L, 3 g / L, 5 g / L, 7 g / L, and 9 g / L), and comparing the effects on the hardness and corrosion resistance of the deposited layer, the optimal pearl powder addition amount was determined to be 7 g / L. Preferably, the optimal amount of pearl powder added is 7g / L.

[0009] Furthermore, the preparation method of the nickel-based nano-pearl powder composite electrodeposition layer on the surface of AZ91D magnesium alloy includes the following specific steps: (1) Mechanical grinding: The magnesium alloy is ground and polished. After grinding, it is ultrasonically cleaned with anhydrous ethanol and cleaned with deionized water. (2) Alkaline washing to remove oil: The saponification effect of alkaline solution is used to remove oil stains from the surface of magnesium alloy after polishing. The alkaline solution consists of sodium hydroxide 30g / L~50g / L, sodium phosphate 30g / L~35g / L, and sodium carbonate 10g / L~12g / L. The alkaline washing temperature is 60℃~70℃. After alkaline washing for 15~20min, it is rinsed with deionized water. (3) Pickling, using a solution containing 85% by mass and a concentration of 580 cm⁻¹ 3 / L~620cm 3 Pickling with a phosphoric acid solution of / L for 35s to 45s removes oxides from the magnesium alloy surface after alkaline washing. After pickling, rinse with deionized water. (4) Surface conditioning: The pickled magnesium alloy is surface-conditioned for 2 min to 2.5 min at 65 to 70 °C using a pyrophosphate system to remove oxides from the pickling process and to slightly etch and level the β phase of the magnesium alloy to fully expose the substrate. The surface conditioning solution includes 150 g / L to 170 g / L potassium pyrophosphate, 18 g / L to 22 g / L sodium carbonate, and 8 g / L to 12 g / L potassium fluoride. After surface conditioning, the surface is rinsed with deionized water. (5) Activation: The magnesium alloy after surface conditioning is activated by using a mixed solution of 170 mL / L to 190 mL / L phosphoric acid and 90 g / L to 100 g / L ammonium fluoride at room temperature for 1 to 2 minutes to remove oxides and generate a magnesium fluoride protective film. After activation, it is washed with deionized water. (6) Alkaline chemical deposition: Alkaline chemical deposition is performed on the activated magnesium alloy. The alkaline chemical deposition solution includes nickel sulfate 20 g / L to 25 g / L, sodium hypophosphite 20 g / L to 25 g / L, sodium citrate 18 g / L to 22 g / L, ammonium bifluoride 10 g / L to 12 g / L, and sodium carbonate 18 g / L to 22 g / L. The deposition process is as follows: deposition temperature is 70℃ to 75℃, pH is adjusted to 9.20 to 9.60 with ammonia water, deposition time is 40 min to 50 min, and magnetic stirring speed is 210 r / min to 280 r / min. (7) Acidic chemical deposition: The magnesium alloy after alkaline chemical deposition is subjected to acidic chemical deposition. The acidic chemical deposition solution includes nickel sulfate 20 g / L to 25 g / L, sodium hypophosphite 20 g / L to 25 g / L, citric acid 4 g / L to 6 g / L, and ammonium bifluoride 18 g / L to 22 g / L. The deposition process is as follows: deposition temperature is 80℃ to 85℃, pH is adjusted to 6.00 to 6.25 with ammonia water, deposition time is 40 min to 50 min, and magnetic stirring speed is 210 r / min to 280 r / min. Magnesium alloy samples are obtained. (8) Prepare the basic electrodeposition solution: nickel sulfate 110 g / L to 130 g / L, ammonium citrate 8 g / L to 12 g / L, ammonium bifluoride 35 g / L to 50 g / L, sodium saccharin 1 g / L to 3 g / L, sodium dodecyl sulfate 0.1 g / L to 0.2 g / L; (9) Prepare electrodeposition solution by mixing pearl powder (1 g / L~9 g / L) and Tween 20 (5 mL / L~15 mL / L) with deionized water to obtain a mixture. Simultaneously, apply mechanical stirring and ultrasound to fully disperse the mixture. Add the dispersed solution to the basic electrodeposition solution in step (8) and continue to disperse for 0.5 h to obtain the electrodeposition solution. (10) Electrodeposition: The nickel plate at the anode and the magnesium alloy sample at the cathode are immersed in the electrodeposition solution and placed in an ultrasonic generator. The positive and negative terminals of the pulse power supply are connected to the anode and cathode, respectively. The area ratio of the anode to the cathode is 2:3, and the electrode spacing is 25 mm. The electrodeposition process is as follows: voltage is 3V, current density is 1.5A·cm. -2 ~3A·cm -2 The duty cycle was 35%–80%, the ultrasonic power was 150W–240W, the ultrasonic frequency was 45KHz and 80KHz alternating for 10s–20s, the magnetic stirring rate was 300r / min, the electrodeposition temperature was 55℃, and the electrodeposition time was 60min; thus, a composite electrodeposition layer was obtained.

[0010] Preferably, in step (2), the alkaline solution consists of 35 g / L sodium hydroxide, 30 g / L sodium phosphate, and 11 g / L sodium carbonate, the alkaline washing temperature is 65°C, and the alkaline washing time is 20 min.

[0011] Preferably, in step (3), the phosphoric acid concentration is 600 cm⁻¹. 3 / L, pickling time is 40s.

[0012] Preferably, in step (4), the surface conditioning solution is composed of 160 g / L potassium pyrophosphate, 20 g / L sodium carbonate, and 11 g / L potassium fluoride, with a surface conditioning temperature of 70°C and a surface conditioning time of 2.5 min.

[0013] Preferably, in step (5), the phosphoric acid concentration is 180 mL / L, the ammonium bifluoride concentration is 95 g / L, and the activation time is 1.5 min.

[0014] Preferably, in step (6), the alkaline chemical deposition solution consists of 20 g / L nickel sulfate, 25 g / L sodium hypophosphite, 20 g / L sodium citrate, 10 g / L ammonium bifluoride, and 23 g / L sodium carbonate; the deposition temperature is 75°C, the pH is 9.40, the deposition time is 45 min, and the magnetic stirring rate is 210 r / min.

[0015] Preferably, in step (7), the acidic chemical deposition solution consists of 20 g / L nickel sulfate, 20 g / L sodium hypophosphite, 5 g / L citric acid, and 20 g / L ammonium bifluoride; the deposition temperature is 80 °C, the pH is 6.20, the deposition time is 45 min, and the magnetic stirring rate is 210 r / min.

[0016] Preferably, in step (8), the basic electrodeposition solution is nickel sulfate 120 g / L, ammonium citrate 10 g / L, ammonium bifluoride 40 g / L, sodium saccharin 3 g / L, and sodium dodecyl sulfate 0.1 g / L.

[0017] Preferably, in step (9), the amount of pearl powder added is 7 g / L, and the amount of Tween20 is 10 mL / L.

[0018] Preferably, in step (10), the electrodeposition process is as follows: current density 2A·cm -2 The duty cycle was 80%, the ultrasonic power was 210W, and the ultrasonic frequencies of 45KHz and 80KHz were alternated for 10s and 20s.

[0019] The advantages of this invention compared to the prior art are: This invention provides a preparation method that produces a uniform, dense, and smooth deposition layer. The hardness is 20 to 22 times higher than that of a magnesium alloy substrate and 1.3 to 1.6 times higher than that of a pure nickel electrodeposited layer on a magnesium alloy surface. The self-corrosion current density is 2 to 3 orders of magnitude lower than that of a magnesium alloy substrate and also lower than that of a pure nickel electrodeposited layer on a magnesium alloy surface. Under existing process parameters, pearl powder and the nickel-based deposition system exhibit a significant synergistic effect, thereby greatly improving the overall performance of the nickel-based composite deposition layer. The active sites on the pearl powder surface and the Ni in the system... 2+ Targeted adsorption is formed, and pearl powder acts as Ni 2+ Reduced deposition of heterogeneous nucleation cores significantly increases the nucleation rate; simultaneously, specific Ni... 2+ The matching of concentration and amount of pearl powder allows for the orderly formation of more nucleation centers, synergistically restricting the growth space of grains, achieving grain refinement in the deposited layer, and synergistically exerting a fine-grain strengthening effect. Under the control of the above process parameters, pearl powder particles and Ni 2+ Co-deposition eventually forms a uniformly dispersed second-phase particle in the sedimentary matrix; these dispersed pearl powder particles work synergistically with the nickel-based sedimentary matrix to effectively hinder dislocation slip and proliferation, and significantly improve the hardness of the sedimentary layer.

[0020] The synergistic effect of pearl powder and nickel-based deposition system under specific process parameters can significantly improve the corrosion resistance of nickel-based composite deposition layers through a triple synergistic effect of filling pores, extending corrosion paths, and optimizing the electrochemical micro-region structure of the deposition layer. Neutral salt spray test results show that compared with pure nickel deposition layers with the same parameters, the corrosion resistance of composite deposition layers is improved by 2 to 3 times, with simultaneous improvement in hardness and corrosion resistance. Attached Figure Description

[0021] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0022] Figure 1These are magnified images of the surface metallographic structure of the deposited layer in the examples, magnified 2000 times. (a) Example 1 (b) Example 2 (c) Example 3 (d) Example 4 (e) Example 5 (f) Example 6.

[0023] Figure 2 This is a cross-sectional metallographic morphology image of the deposition layer in the examples, magnified 560 times. (a) Example 1 (b) Example 2 (c) Example 3 (d) Example 4 (e) Example 5 (f) Example 6.

[0024] Figure 3 These are microhardness diagrams of the deposition layers in Examples 1-6.

[0025] Figure 4 These are polarization curves of the deposition layers in Examples 1-6. Detailed Implementation

[0026] The present invention is described in detail below through specific embodiments, but this does not limit the scope of protection of the present invention. Unless otherwise specified, the experimental methods used in the present invention are all conventional methods, and the experimental equipment, materials, reagents, etc. used can all be obtained commercially.

[0027] This invention uses an electrodeposition solution with the following composition: nickel sulfate 110 g / L–130 g / L, ammonium citrate 8 g / L–12 g / L, ammonium bifluoride 35 g / L–50 g / L, sodium saccharin 1 g / L–3 g / L, sodium dodecyl sulfate 0.1 g / L–0.2 g / L, Tween 20 5 mL / L–15 mL / L, and pearl powder (particle size 50 nm–300 nm) 1 g / L–9 g / L. A variable-frequency power ultrasonic pulse electrodeposition method is used to ultimately prepare a nickel-based pearl powder composite deposition layer on the surface of a magnesium alloy substrate. The obtained composite deposition layer has a smooth, dense, and uniform surface. Its hardness is 20 to 22 times higher than that of the magnesium alloy substrate and 1.3 to 1.6 times higher than that of a pure nickel layer electrodeposited on a magnesium alloy surface. The self-corrosion current density is 2 to 3 orders of magnitude lower than that of the magnesium alloy substrate, and the corrosion resistance is improved compared to a pure nickel layer electrodeposited on a magnesium alloy surface. The nickel-based nano-pearl powder composite electrodeposition layer prepared on the surface of AZ91D magnesium alloy by this invention has extremely high hardness and good corrosion resistance.

[0028] In one or more embodiments of this implementation, the specific preparation process is as follows: (1) The substrate is leveled by mechanically leveling its surface to reduce its surface roughness, including grinding and polishing. The surface of the AZ91D magnesium alloy substrate is mechanically ground with 320 grit, 600 grit, 800 grit, 1000 grit, 1200 grit, 1500 grit and 2000 grit wet sandpaper. During the grinding process, from a materials science perspective, the substrate surface should be ground from two mutually perpendicular directions, and the number of grinding passes in both directions should be kept as consistent as possible. At the same time, the grinding marks should be small and uniform to ensure both the bonding force between the deposited layer and the substrate and the smoothness of the deposited layer.

[0029] (2) The substrate undergoes surface treatment to remove any dust, grease, and oxides, and to form a protective magnesium fluoride film. First, it is cleaned with anhydrous ethanol for 10 minutes using an ultrasonic wave at 80 kHz and 180 W, followed by rinsing with deionized water. Then, the substrate is placed in a degreasing alkaline solution at 60℃~70℃ for 15 minutes~20 minutes to remove any grease from the surface. The degreasing alkaline solution consists of 30 g / L~50 g / L sodium hydroxide, 30 g / L~35 g / L sodium phosphate, 10 g / L~12 g / L sodium carbonate, and water as the balance. After alkaline washing, it is rinsed with deionized water. Then, the substrate is acid-washed at room temperature for 35 s~45 s to remove oxides from the magnesium alloy surface. The acid-washing solution mainly consists of 85% by mass and a concentration of 580 cm3 / L~620 cm3 / L. 3 The magnesium alloy was pickled with phosphoric acid at a concentration of 1 / L and then rinsed with deionized water. Afterward, the magnesium alloy was surface-conditioned at 65–70°C for 2–2.5 minutes to remove pickling corrosion products adsorbed on the substrate surface and to slightly etch the β phase of the magnesium alloy, thus smoothing the surface. The surface-conditioning solution consisted of 150–170 g / L potassium pyrophosphate, 18–22 g / L sodium carbonate, 8–12 g / L potassium fluoride, and water as the balance. After surface conditioning, the alloy was rinsed with deionized water. Finally, the magnesium alloy was activated at room temperature for 1–2 minutes to further dissolve the oxides, exposing the active metal interface and forming a magnesium fluoride protective film. The activation solution consisted of 170–190 mL / L phosphoric acid, 90–100 g / L ammonium bifluoride, and water as the balance. After activation, the alloy was immediately rinsed with deionized water.

[0030] (3) After surface treatment of the substrate, it is immediately placed in a constant temperature water bath for alkaline chemical deposition. The alkaline chemical deposition solution consists of 20 g / L to 25 g / L nickel salt, 20 g / L to 25 g / L sodium hypophosphite, 18 g / L to 22 g / L citrate, 10 g / L to 12 g / L ammonium bifluoride, and 18 g / L to 22 g / L sodium carbonate. During the alkaline chemical deposition process, the temperature is 70℃ to 75℃, the pH of the alkaline solution is adjusted to 9.20 to 9.60, the deposition time is 45 min to 55 min, and the magnetic stirring rate is 250 to 300 r / min.

[0031] (4) After alkaline chemical deposition, the surface is rinsed with deionized water and then placed in a constant temperature water bath for acidic chemical deposition. The acidic chemical deposition solution consists of 20 g / L to 25 g / L nickel salt, 20 g / L to 25 g / L sodium hypophosphite, 4 g / L to 6 g / L citric acid, and 18 g / L to 22 g / L ammonium bifluoride. During the acidic chemical deposition process, the temperature is 80℃ to 85℃, the pH is adjusted to 6.00 to 6.25 with the alkaline solution, the deposition time is 45 r / min to 55 min, and the magnetic stirring speed is 250 r / min to 300 r / min.

[0032] (5) After the acidic chemical deposition is completed, the deposited layer should be quickly removed from the water bath, stirring should be stopped, and the mixture should be washed with deionized water and dried with hot air. A magnesium alloy sample is obtained.

[0033] (6) First, prepare the basic electrodeposition solution according to the main salt formula. Its components are: nickel sulfate 110 g / L–130 g / L, ammonium citrate 8 g / L–12 g / L, ammonium bifluoride 35 g / L–50 g / L, sodium saccharin 1 g / L–3 g / L, and sodium dodecyl sulfate 0.1 g / L–0.2 g / L. Mix 7 g / L pearl powder and 5 mL / L–15 mL / L L-20 with deionized water. Simultaneously, apply mechanical stirring and ultrasound to fully disperse the mixture. Add the dispersed solution to the basic electrodeposition solution and continue dispersion for 0.5 h. The electrodeposition solution is then obtained.

[0034] (7) Immerse the nickel anode plate and the magnesium alloy cathode sample in the electrodeposition solution and place them in an ultrasonic generator. Connect the positive and negative terminals of the pulse power supply to the anode and cathode, respectively. The electrodeposition process is as follows: voltage 3V, current density 1.5A·cm. -2 ~3A·cm -2 The duty cycle is 35%–80%, the ultrasonic power is 150W–240W, the ultrasonic frequency is 45KHz and 80KHz alternating for 10–20s, the magnetic stirring rate is 300r / min, the electrodeposition temperature is 55℃, and the electrodeposition time is 60min.

[0035] To enable those skilled in the art to better understand the technical solutions of this disclosure, the technical solutions of this disclosure will be described in detail below with reference to specific embodiments.

[0036] Example 1 A method for preparing a nickel-based nano-pearl powder composite electrodeposition layer on the surface of AZ91D magnesium alloy includes the following steps; (1) Grinding. The AZ91D magnesium alloy substrate was ground and polished with sandpaper, and then ultrasonically cleaned in ethanol solution for 2 minutes and cleaned with deionized water for 2 minutes.

[0037] (2) Alkaline washing to remove oil: Alkaline washing is performed on the AZ91D magnesium alloy after grinding in step (1). An alkaline washing solution containing 35g / L sodium hydroxide, 30g / L sodium phosphate and 10g / L sodium carbonate is prepared. The alkaline washing temperature is 65℃ and the alkaline washing time is 20min.

[0038] (3) Pickling: Pickling of AZ91D magnesium alloy after alkaline washing, using a solution containing 600 cm⁻¹ 3 Pickling solution of phosphoric acid (85% by mass) / L, followed by rinsing with deionized water for 1 min.

[0039] (4) Surface conditioning: For the pickled AZ91D magnesium alloy, prepare a surface conditioning solution containing 160 g / L potassium pyrophosphate, 20 g / L sodium carbonate and 11 g / L potassium fluoride. Surface condition the magnesium alloy at 70°C for 2.5 min. After surface conditioning, rinse with deionized water for 1 min.

[0040] (5) Activation: Activate the surface-conditioned AZ91D magnesium alloy by preparing an activation solution containing 180 mL / L phosphoric acid and 95 g / L ammonium fluoride, and activate the surface-conditioned AZ91D magnesium alloy for 1.5 min at room temperature. After activation, rinse with deionized water for 1 min.

[0041] (6) Alkaline chemical deposition: Alkaline chemical deposition was performed on the activated AZ91D magnesium alloy. The alkaline chemical deposition solution included 20 g / L nickel sulfate, 25 g / L sodium hypophosphite, 20 g / L sodium citrate, 10 g / L ammonium bifluoride, and 20 g / L sodium carbonate, with a pH of 9.40. The prepared alkaline chemical deposition solution was placed in a constant temperature water bath at 75°C and deposited for 45 min. The magnetic stirring rate was 210 r / min.

[0042] (7) Acidic chemical deposition: The AZ91D magnesium alloy after alkaline chemical deposition was subjected to acidic chemical deposition. The acidic chemical deposition solution included 20 g / L nickel sulfate, 20 g / L sodium hypophosphite, 5 g / L citric acid, and 20 g / L ammonium bifluoride, with a pH of 6.20. The prepared acidic chemical deposition solution was placed in a constant temperature water bath at 80°C and deposited for 45 min with a magnetic stirring rate of 210 r / min. Magnesium alloy samples were obtained.

[0043] (8) First, prepare the basic electrodeposition solution according to the main salt formula, the components of which are: nickel sulfate 120 g / L, ammonium citrate 10 g / L, ammonium bifluoride 40 g / L, sodium saccharin 3 g / L, and sodium dodecyl sulfate 0.1 g / L. Mix pearl powder (particle size 250 nm ~ 300 nm) 7 g / L and 10 mL / L L-20 with deionized water, and simultaneously apply mechanical stirring and ultrasound to fully disperse the mixture. Add the dispersed solution to the basic electrodeposition solution and continue dispersion for 0.5 h. Obtain the electrodeposition solution.

[0044] (9) Immerse the nickel anode plate and the magnesium alloy cathode sample in the electrodeposition solution and place them in an ultrasonic generator. Connect the positive and negative terminals of the pulse power supply to the anode and cathode, respectively. The electrodeposition process is as follows: voltage 3V, current density 2A·cm. -2 The electrodeposition process was carried out with a duty cycle of 80%, an ultrasonic power of 210W, and alternating ultrasonic frequencies of 45kHz and 80kHz for 10s and 20s, respectively. The magnetic stirring rate was 300r / min, the electrodeposition temperature was 55℃, and the electrodeposition time was 60min. A nickel-based pearl powder composite deposition layer was obtained.

[0045] Figure 1 (a) The metallographic surface morphology of the nickel-based pearl powder composite deposition layer prepared in Example 1 shows that the deposition layer is uniform and dense; Figure 2 (a) From the metallographic cross-sectional morphology, no obvious cracks were observed, and the deposited layer was tightly bonded to the matrix; the hardness test results are as follows. Figure 3 As shown, the microhardness of the deposited layer is 1280.64 HV, which is 18.46 times higher than the microhardness of the substrate (69.38 HV) and 1.37 times higher than the microhardness of the pure nickel layer (933.6 HV); the electrochemical corrosion resistance test results are as follows: Figure 4 As shown, the self-corrosion potential of the deposited layer is -0.662V, which is 658mV more positive than that of the substrate (-1.32V) and 286mV more negative than that of the pure nickel layer (-0.376V). The self-corrosion current density is also higher than that of the pure nickel layer (7.771×10⁻⁶). -7 A·cm -2 It rose to 3.50x10 -6 A·cm -2 Compared to the substrate (1.669×10), -4 A·cm -2The hardness decreased by two orders of magnitude. This indicates that 7 g / L of pearl powder (particle size 250 nm to 300 nm) can significantly improve the hardness of the deposited layer, and the corrosion resistance is improved compared to the substrate, but decreased compared to the pure nickel layer.

[0046] Example 2 A method for preparing a nickel-based nano-pearl powder composite electrodeposition layer on the surface of AZ91D magnesium alloy includes the following steps; the difference from Example 1 is that the amount of pearl powder added in the electrodeposition solution is 7g / L, and the pearl powder particle size is 200nm~250nm.

[0047] Figure 1 (b) shows the metallographic morphology of the composite deposition layer prepared in Example 2, which is more uniform and dense than that in Example 1; Figure 2 (b) From the cross-sectional metallographic morphology, no peeling or cracking was observed, and the deposited layer was tightly bonded to the matrix; the hardness test results are as follows. Figure 3 As shown, the microhardness of the composite deposition layer is 1430.92 HV, which is 20.62 times higher than the microhardness of the substrate (69.382 HV) and 1.53 times higher than the microhardness of the pure nickel layer (933.6 HV); the electrochemical corrosion resistance test results are as follows: Figure 4 As shown, the self-corrosion potential of the deposited layer is -0.492V, which is 828mV more positive than that of the substrate (-1.32V) and 116mV more negative than that of the pure nickel layer (-0.376V). The self-corrosion current density is also higher than that of the pure nickel layer (7.771×10⁻⁶). -7 A·cm -2 It rose to 4.31x10 -6 A·cm -2 Compared to the substrate (1.669×10), -4 A·cm -2 The hardness decreased by two orders of magnitude. This indicates that 7 g / L of pearl powder (particle size 200 nm to 250 nm) can significantly improve the hardness of the deposited layer, and the corrosion resistance is improved compared to the substrate, but decreased compared to the pure nickel layer.

[0048] Example 3 A method for preparing a nickel-based nano-pearl powder composite electrodeposition layer on the surface of AZ91D magnesium alloy includes the following steps; the difference from Example 1 is that the amount of pearl powder added in the electrodeposition solution is 7g / L, and the pearl powder particle size is 150min~200nm.

[0049] Figure 1 (c) shows the metallographic morphology of the composite deposition layer prepared in Example 3. The deposition layer is more uniform and dense than that in Example 1. Figure 2 (c) From the cross-sectional metallographic morphology, no peeling or cracking was observed, and the deposited layer was tightly bonded to the matrix; the hardness test results are as follows. Figure 3As shown, the microhardness of the composite deposition layer is 1468.38 HV, which is 21.16 times higher than the microhardness of the substrate (69.382 HV) and 1.57 times higher than the microhardness of the pure nickel layer (933.6 HV); the electrochemical corrosion resistance test results are as follows: Figure 4 As shown, the self-corrosion potential of the deposited layer is -0.59V, which is 730mV more positive than that of the substrate (-1.32V) and 240mV more negative than that of the pure nickel layer (-0.350V). The self-corrosion current density is also higher than that of the pure nickel layer (7.771×10⁻⁶). -7 A·cm -2 It rose to 1.19x10 -6 A·cm -2 Compared to the substrate (1.669×10), -4 A·cm -2 The hardness decreased by two orders of magnitude. This indicates that 7 g / L of pearl powder (particle size 150 nm to 200 nm) can significantly improve the hardness of the deposited layer, and the corrosion resistance is improved compared to the substrate, but decreased compared to the pure nickel layer.

[0050] Example 4 A method for preparing a nickel-based nano-pearl powder composite electrodeposition layer on the surface of AZ91D magnesium alloy includes the following steps; the difference from Example 1 is that the amount of pearl powder added in the electrodeposition solution is 7g / L, and the pearl powder particle size is 100~150 nm.

[0051] Figure 1 (d) shows the metallographic morphology of the composite deposition layer prepared in Example 4. The deposition layer is the most uniform and dense compared to that in Example 1. Figure 2 (d) From the cross-sectional metallographic morphology, no peeling or cracking was observed, and the deposited layer was tightly bonded to the matrix; the hardness test results are as follows. Figure 3 As shown, the microhardness of the composite deposition layer is 1491.12 HV, which is 21.49 times higher than the microhardness of the substrate (69.382 HV) and 1.60 times higher than the microhardness of the pure nickel layer (933.6 HV); the electrochemical corrosion resistance test results are as follows: Figure 4 As shown, the self-corrosion potential of the deposited layer is -0.756V, which is 564mV more positive than that of the substrate (-1.32V) and 406mV more negative than that of the pure nickel layer (-0.350V). The self-corrosion current density is also higher than that of the pure nickel layer (7.771×10⁻⁶). -7 A·cm -2 It dropped to 3.42x10 -7 A·cm -2 Compared to the substrate (1.669×10), -4 A·cm -2The hardness decreased by three orders of magnitude. This indicates that 7 g / L of pearl powder (particle size 100 nm to 150 nm) can significantly improve the hardness of the deposited layer, and the corrosion resistance is also improved. This shows that as the pearl powder grains are further refined, the hardness of the deposited layer increases while its corrosion resistance also improves.

[0052] Example 5 A method for preparing a nickel-based nano-pearl powder composite electrodeposition layer on the surface of AZ91D magnesium alloy includes the following steps; the difference from Example 1 is that the amount of pearl powder added in the electrodeposition solution is 7g / L, and the pearl powder particle size is 80~100 nm.

[0053] Figure 1 (e) shows the metallographic morphology of the composite deposition layer prepared in Example 5; the deposition layer is uniform and dense. Figure 2 (e) From the cross-sectional metallographic morphology, no peeling or cracking was observed, and the deposited layer was tightly bonded to the matrix; the hardness test results are as follows. Figure 3 As shown, the microhardness of the composite deposition layer is 1524.25 HV, which is 21.97 times higher than the microhardness of the substrate (69.382 HV) and 1.63 times higher than the microhardness of the pure nickel layer (933.6 HV); the electrochemical corrosion resistance test results are as follows: Figure 4 As shown, the self-corrosion potential of the deposited layer is -0.528V, which is 792mV more positive than that of the substrate (-1.32V) and 178mV more negative than that of the pure nickel layer (-0.350V). The self-corrosion current density is also higher than that of the pure nickel layer (7.771×10⁻⁶). -7 A·cm -2 It dropped to 1.27x10 -7 A·cm -2 Compared to the substrate (1.669×10), -4 A·cm -2 The hardness of the deposited layer decreased by three orders of magnitude. This indicates that as the pearl powder grains are further refined, the hardness of the deposited layer reaches its peak when the pearl powder (particle size 80~100nm) is 7g / L, and the corrosion resistance of the deposited layer is also significantly improved.

[0054] Example 6 A method for preparing a nickel-based nano-pearl powder composite electrodeposition layer on the surface of AZ91D magnesium alloy includes the following steps; the difference from Example 1 is that the amount of pearl powder added in the electrodeposition solution is 7g / L, and the pearl powder particle size is 50~80 nm.

[0055] Figure 1 (f) shows the metallographic morphology of the composite deposition layer prepared in this embodiment; the deposition layer is uniform and dense. Figure 2 (f) From the cross-sectional metallographic morphology, no peeling or cracking was observed, and the deposited layer was tightly bonded to the matrix; the hardness test results are as follows. Figure 3As shown, the microhardness of the composite deposition layer is 1506.37 HV, which is 21.71 times higher than the microhardness of the substrate (69.382 HV) and 1.61 times higher than the microhardness of the pure nickel layer (933.6 HV); the electrochemical corrosion resistance test results are as follows: Figure 4 As shown, the self-corrosion potential of the deposited layer is -0.398V, which is 922mV more positive than that of the substrate (-1.32V) and 48mV more negative than that of the pure nickel layer (-0.350V). The self-corrosion current density of the deposited layer is 4.21 x 10⁻⁶. -7 A•cm -2 Compared to the matrix (1.669×10 -4 A•cm -2 The decrease is three orders of magnitude compared to the pure nickel layer (7.771 × 10⁻⁶). -7 A·cm -2 The hardness of the deposited layer has decreased. This indicates that as the nano-pearl powder crystals reach their finest point, the hardness of the deposited layer can be significantly improved, while the corrosion resistance of the deposited layer is also significantly enhanced.

[0056] Comparative Example 1 A method for preparing a pure nickel layer by electrodeposition on the surface of AZ91D magnesium alloy. The specific operation steps are the same as in Example 1. The anode nickel plate and the cathode magnesium alloy sample are immersed in the electrodeposition solution and placed in an ultrasonic generator. The positive and negative terminals of the pulse power supply are connected to the anode and cathode, respectively. The electrodeposition process is as follows: voltage 3V, current density 2A·cm⁻¹. -2 A pure nickel layer was successfully electrodeposited on the surface of AZ91D magnesium alloy using the following methods: duty cycle 80%, ultrasonic power 210W, alternating ultrasonic frequencies of 45kHz and 80kHz for 10s and 20s, magnetic stirring rate 300r / min, electrodeposition temperature 55℃, and electrodeposition time 60min.

[0057] Comparative Example 2 A method for preparing a nickel-based nanodiamond composite electrodeposition layer on the surface of AZ91D magnesium alloy. The specific process flow differs from Example 1 in that: the nanodiamond concentration is 5 g / L, the voltage is 3 V, and the current density is 2 A·cm⁻¹. -2 The electrodeposition process was carried out with a duty cycle of 80%, an ultrasonic power of 210W, and alternating ultrasonic frequencies of 45kHz and 80kHz for 10s and 20s, a mechanical stirring rate of 300r / min, an electrodeposition temperature of 55℃, and an electrodeposition time of 60min. Mechanical stirring ensured uniform dispersion of nanodiamonds in the deposition solution, resulting in a nickel-based nanodiamond composite electrodeposited layer on the surface of AZ91D magnesium alloy.

[0058] Comparative Example 3 A method for preparing a nickel-based nano-pearl powder composite electrodeposition layer on the surface of AZ91D magnesium alloy. The specific process flow differs from Example 1 in that: the amount of pearl powder added to the electrodeposition solution is 5 g / L, the pearl powder particle size is 200~250 nm, and the current density is 2 A·cm⁻¹. -2 The electrodeposition process was carried out with a duty cycle of 80%, an ultrasonic power of 210W, and alternating ultrasonic frequencies of 45kHz and 80kHz for 10s and 20s, a mechanical stirring rate of 300r / min, an electrodeposition temperature of 55℃, and an electrodeposition time of 60min. Sodium dodecyl sulfate (0.1g / L) and Tween 20 (5-15mL / L) were used. Mechanical stirring ensured uniform dispersion of pearl powder in the deposition solution, resulting in a nickel-based nano-pearl powder composite electrodeposition layer on the surface of AZ91D magnesium alloy.

[0059] Comparative Example 4 A method for preparing a nickel-based nano-pearl powder composite electrodeposition layer on the surface of AZ91D magnesium alloy. The specific process flow differs from Example 1 in that: the amount of pearl powder added to the electrodeposition solution is 7 g / L, the pearl powder particle size is 200~250 nm, and the current density is 2 A·cm⁻¹. -2 The electrodeposition process was carried out using a duty cycle of 70%, an ultrasonic power of 210W, alternating ultrasonic frequencies of 45kHz and 80kHz for 10s and 20s, a mechanical stirring rate of 300r / min, an electrodeposition temperature of 55℃, and an electrodeposition time of 90min. Sodium dodecyl sulfate (0.1g / L) and Tween 20 (5-15mL / L) were added. Mechanical stirring ensured uniform dispersion of pearl powder in the deposition solution, resulting in a nickel-based nano-pearl powder composite electrodeposition layer on the surface of AZ91D magnesium alloy.

[0060] Comparative Example 5 A method for preparing a nickel-based nano-pearl powder composite electrodeposition layer on the surface of AZ91D magnesium alloy. The specific process flow differs from Example 1 in that: the amount of pearl powder added to the electrodeposition solution is 9 g / L, the pearl powder particle size is 200~250 nm, and the current density is 2 A·cm⁻¹. -2 The electrodeposition process was carried out with a duty cycle of 80%, an ultrasonic power of 210W, and alternating ultrasonic frequencies of 45kHz and 80kHz for 10s and 20s, a mechanical stirring rate of 300r / min, an electrodeposition temperature of 55℃, and an electrodeposition time of 60min. Sodium dodecyl sulfate (0.1g / L) and Tween 20 (5-15mL / L) were used. Mechanical stirring ensured uniform dispersion of pearl powder in the deposition solution, resulting in a nickel-based nano-pearl powder composite electrodeposition layer on the surface of AZ91D magnesium alloy.

[0061] A comparative study was conducted to examine the effects of the proposed solution against a comparative example. The comparative effect evaluation is shown in Table 1.

[0062] Table 1 Evaluation of the comparative effects of magnesium alloy electrodeposition layers The embodiments described above are merely preferred embodiments of the present invention, and not all feasible embodiments of the present invention. Any obvious modifications made by those skilled in the art without departing from the principles and spirit of the present invention should be considered to be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a nickel-based nano-pearl powder composite electrodeposition layer on the surface of AZ91D magnesium alloy, characterized in that, The cathode is a pre-deposited magnesium alloy sample, and the anode is a nickel plate with a mass fraction greater than 99%. The two are connected to the negative and positive terminals of the pulse power supply, respectively. They are immersed in a pre-prepared electrodeposition solution and placed in an ultrasonic generator for electrodeposition. The ultrasonic generator operates in a frequency conversion mode. The electrodeposition solution has the following specific composition: nickel sulfate 110 g / L to 130 g / L, ammonium citrate 8 g / L to 12 g / L, ammonium bifluoride 35 g / L to 50 g / L, sodium saccharin 1 g / L to 3 g / L, sodium dodecyl sulfate 0.1 g / L to 0.2 g / L, Tween 20 5 g / L to 15 mL / L, and pearl powder 1 g / L to 9 g / L; the pearl powder size is 50 nm to 300 nm.

2. The method for preparing a nickel-based nano-pearl powder composite electrodeposition layer on the surface of AZ91D magnesium alloy as described in claim 1, characterized in that, The amount of pearl powder added is 7g / L.

3. The method for preparing a nickel-based nano-pearl powder composite electrodeposition layer on the surface of AZ91D magnesium alloy as described in claim 1, characterized in that, The specific steps are as follows: (1) Mechanical grinding: The magnesium alloy is ground and polished. After grinding, it is ultrasonically cleaned with anhydrous ethanol and cleaned with deionized water. (2) Alkaline washing to remove oil: Alkaline solution is used to remove oil stains from the surface of the magnesium alloy after polishing. After alkaline washing, deionized water is used for cleaning. (3) Pickling, using a solution containing 85% by mass and a concentration of 580 cm⁻¹ 3 / L~620cm 3 Pickling with a phosphoric acid solution of / L for 35s to 45s removes oxides from the magnesium alloy surface after alkaline washing. After pickling, rinse with deionized water. (4) Surface conditioning: The pickled magnesium alloy is surface-conditioned for 2 min to 2.5 min at 65 to 70 °C using a pyrophosphate system to remove oxides from the pickling process and to slightly etch and level the β phase of the magnesium alloy to fully expose the substrate. After surface conditioning, it is rinsed with deionized water. (5) Activation: The magnesium alloy after surface conditioning is activated by using a mixed solution of 170 mL / L to 190 mL / L phosphoric acid and 90 g / L to 100 g / L ammonium fluoride at room temperature for 1 to 2 minutes to remove oxides and generate a magnesium fluoride protective film. After activation, it is washed with deionized water. (6) Alkaline chemical deposition: Alkaline chemical deposition is performed on the activated magnesium alloy. (7) Acidic chemical deposition: Acidic chemical deposition is performed on the magnesium alloy after alkaline chemical deposition to obtain a magnesium alloy sample. (8) Prepare the basic electrodeposition solution: nickel sulfate 110 g / L to 130 g / L, ammonium citrate 8 g / L to 12 g / L, ammonium bifluoride 35 g / L to 50 g / L, sodium saccharin 1 g / L to 3 g / L, sodium dodecyl sulfate 0.1 g / L to 0.2 g / L; (9) Prepare electrodeposition solution by mixing pearl powder (1 g / L~9 g / L) and Tween 20 (5 mL / L~15 mL / L) with deionized water to obtain a mixture. Simultaneously, apply mechanical stirring and ultrasound to fully disperse the mixture. Add the dispersed solution to the basic electrodeposition solution in step (8) and continue to disperse for 0.5 h to obtain the electrodeposition solution. (10) Electrodeposition: The anode nickel plate and the cathode magnesium alloy sample were immersed in the electrodeposition solution and placed in an ultrasonic generator. The positive and negative terminals of the pulse power supply were connected to the anode and the cathode, respectively. The electrodeposition process was as follows: voltage 3V, current density 1.5A·cm-2~3A·cm-2, duty cycle 35%~80%, ultrasonic power 150W~240W, ultrasonic frequency 45KHz and 80KHz alternating for 10s~20s, magnetic stirring rate 300r / min, electrodeposition temperature 55℃, and electrodeposition time 60min. A composite electrodeposition layer was obtained.

4. The method for preparing a nickel-based nano-pearl powder composite electrodeposition layer on the surface of AZ91D magnesium alloy as described in claim 3, characterized in that, In step (2), the alkaline solution consists of sodium hydroxide 30 g / L to 50 g / L, sodium phosphate 30 g / L to 35 g / L, and sodium carbonate 10 g / L to 12 g / L. The alkaline washing temperature is 60℃ to 70℃, and the alkaline washing time is 15 to 20 min.

5. The method for preparing a nickel-based nano-pearl powder composite electrodeposition layer on the surface of AZ91D magnesium alloy as described in claim 3, characterized in that, In step (4), the surface conditioning solution includes 150 g / L to 170 g / L potassium pyrophosphate, 18 g / L to 22 g / L sodium carbonate, and 8 g / L to 12 g / L potassium fluoride.

6. The method for preparing a nickel-based nano-pearl powder composite electrodeposition layer on the surface of AZ91D magnesium alloy as described in claim 3, characterized in that, In step (6), the alkaline chemical deposition solution includes nickel sulfate 20 g / L to 25 g / L, sodium hypophosphite 20 g / L to 25 g / L, sodium citrate 18 g / L to 22 g / L, ammonium bifluoride 10 g / L to 12 g / L, and sodium carbonate 18 g / L to 22 g / L. The deposition process is as follows: deposition temperature is 70℃ to 75℃, pH is adjusted to 9.20 to 9.60 with ammonia, deposition time is 40 min to 50 min, and magnetic stirring speed is 210 r / min to 280 r / min.

7. The method for preparing a nickel-based nano-pearl powder composite electrodeposition layer on the surface of AZ91D magnesium alloy as described in claim 3, characterized in that, In step (7), the acidic chemical deposition solution includes 20 g / L to 25 g / L nickel sulfate, 20 g / L to 25 g / L sodium hypophosphite, 4 g / L to 6 g / L citric acid, and 18 g / L to 22 g / L ammonium bifluoride. The deposition process is as follows: deposition temperature is 80℃ to 85℃, pH is adjusted to 6.00 to 6.25 with ammonia, deposition time is 40 min to 50 min, and magnetic stirring speed is 210 r / min to 280 r / min.

8. The method for preparing a nickel-based nano-pearl powder composite electrodeposition layer on the surface of AZ91D magnesium alloy as described in claim 3, characterized in that, In step (10), the area ratio of the anode to the cathode is 2:3, and the electrode spacing is 25mm.

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