A method for preparing a magnesium alloy surface variable-frequency power ultrasonic electrodeposited nanometer nickel-based composite layer

Abstract

The application discloses a preparation method of a magnesium alloy surface variable-frequency power ultrasonic electrodeposited nanometer nickel-based composite layer and belongs to the technical field of metal substrate surface coating layer preparation. The electrodeposition liquid composition is as follows: nickel sulfate 110-130 g / L, ammonium citrate 8-12 g / L, ammonium hydrogen fluoride 35-50 g / L, sodium saccharin 3 g / L, ammonia water 35-45 ml / L, TiN 1-7 g / L, and GO 0.05-0.25 g / L (auxiliary addition). The preparation specific process is as follows: the voltage is 3 V, the current density is 1.5-3 A / cm ‑2 , the duty cycle is 35-80%, the ultrasonic power is 150-240 W, the ultrasonic frequency is 45 KH Z and 80 KH Z alternately acts for 10-20 s, the magnetic stirring rate is 300 r / min, the deposition temperature is 55 DEG C, and the deposition time is 75 min. The formed deposition layer is bright in appearance, has no peeling and falling, the hardness is increased by 8.5-10.8 times of the substrate, the self-corrosion current density is decreased by 2-3 orders of magnitude of the substrate, and the deposition layer has high hardness and excellent corrosion resistance.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of surface coating layer preparation of metal base materials, and relates to a method for preparing a nano nickel-based composite layer on the surface of a magnesium alloy through variable-frequency power ultrasonic electrodeposition. BACKGROUND

[0002] Magnesium alloy has low density, high specific strength, high dimensional stability, good impact resistance and electromagnetic shielding capacity, and is easy to recycle, and thus is widely concerned as an environmentally friendly material. Currently, the most widely used magnesium alloy is AZ91D cast magnesium alloy, but its poor corrosion resistance seriously restricts its large-scale application.

[0003] The commonly used electrodeposited layer on the surface of a magnesium alloy is composed of copper, aluminum or nickel. Copper-based electrodeposited layer is often used in electronic devices due to its high electrical conductivity and thermal conductivity, but the copper-based electrodeposited layer has low tensile strength, poor wear resistance and high corrosion rate, and contains highly toxic cyanide in the plating solution to ensure the film-substrate adhesion. Aluminum and magnesium are both light metals, and depositing aluminum can greatly reduce the potential difference between the deposited layer and the substrate and reduce galvanic corrosion, but depositing aluminum requires anhydrous environment and has high requirements for equipment and complex process.

[0004] With the development of nanotechnology, nano-composite electrodeposition technology has attracted widespread attention due to its simple process and easy operation. By adding nanoparticles to the electrodeposition solution, the substrate metal and nanoparticles can be co-deposited under the action of an electric field. The nano nickel-based metal ceramic composite layer prepared by this method has excellent wear resistance, corrosion resistance and high-temperature oxidation resistance and is widely used. The commonly used method for preparation is direct current electrodeposition assisted by mechanical stirring, but this method cannot well solve the problem of nanoparticle agglomeration in the plating solution, resulting in unsatisfactory hardness and corrosion resistance of the prepared deposited layer. In addition, the widely used traditional Watts nickel plating solution (including improved ones) is not suitable for magnesium alloy. Although a pre-plating layer is prepared on the surface of the magnesium alloy, it is still difficult to form a bright and excellent performance nickel plating layer. For example, the improved Watts nickel plating solution suitable for alloy steel (application number CN202110383810) disclosed by the research group in the early stage is applied to magnesium alloy electrodeposition, and a large number of peeling phenomena occur in the obtained nickel plating layer. SUMMARY

[0005] In order to overcome the prior art, the present application provides a kind of magnesium alloy surface variable frequency power ultrasonic electrodeposition nanometer nickel-based composite layer preparation method, including a kind of adaptation AZ91D magnesium alloy's electrodeposition fluid and variable frequency power ultrasonic pulse electrodeposition method, in ultrasonic generator by adjusting ultrasonic frequency and ultrasonic power reduce the agglomeration of nano particles in the composite electrodeposition process, the appearance of the deposited layer is bright, and there is no peeling and falling, the hardness (600-750HV) is increased by 8.5-10.8 times compared with the matrix, the self-corrosion current density is reduced by 2-3 orders of magnitude compared with the matrix, with high hardness and excellent corrosion resistance.

[0006] The above-mentioned object of the present application is achieved by the following technical solutions:

[0007] A kind of magnesium alloy surface variable frequency power ultrasonic electrodeposition nanometer nickel-based composite layer preparation method, cathode uses the magnesium alloy sample after chemical pre-deposition, anode uses the nickel plate with the purity greater than 99%, both are connected the negative pole and the positive pole of pulse power respectively, is immersed in the pre-configured electroplating solution and is placed in ultrasonic generator to carry out electrodeposition, ultrasonic generator works in variable frequency mode.

[0008] For the above preparation method, the present application provides an electrodeposition fluid suitable for magnesium alloy, and the specific composition is as follows: nickel sulfate 110-130 g / L, ammonium citrate 8-12 g / L, ammonium hydrogen fluoride 35-50 g / L, sodium saccharin 3 g / L, ammonia water 35-45 ml / L, TiN 1-7 g / L, GO 0.05-0.25 g / L (auxiliary additive), and 0.1 g / L sodium dodecyl sulfate.

[0009] In the electrodeposition fluid suitable for magnesium alloy, nickel sulfate provides nickel ions; ammonium citrate acts as a complexing agent to complex free nickel ions in the plating solution, control the deposition rate, and improve the stability of the plating solution; ammonium hydrogen fluoride acts as a corrosion inhibitor and an accelerator to promote the reaction while ensuring that the magnesium alloy is not corroded in the plating solution; TiN as a reinforcing phase can be co-deposited with Ni 2+ , further improving the performance of the plating layer; GO as an auxiliary additive can promote the movement rate of metal particles and nanoparticles to the cathode, further improve the morphology of the plating layer, and improve the corrosion resistance; sodium dodecyl sulfate as a surfactant can promote the wettability of nanoparticles and GO in water, and better mix with the solution. The provided plating solution component ratio can obtain good deposition rate while ensuring that the magnesium alloy is not corroded during plating, so that a well-bonded, high-hardness, high-corrosion-resistant plating layer can be obtained.

[0010] The present application further provides an electrodeposition process under the above-mentioned deposition solution, comprising the following steps:

[0011] (a) pretreatment: polish, degrease, acid wash, surface conditioning and activation treatment for magnesium alloy.

[0012] (b) Chemical pre-deposition: double-layer electroless nickel-phosphorus plating on the pretreated magnesium alloy sample.

[0013] (c) Preparing the electro-deposition solution according to the main salt formula, adding nickel sulfate into ammonium citrate, then sequentially adding ammonium hydrogen fluoride, sodium saccharin, and ammonia water, which together constitute the basic electro-deposition solution, then mixing TiN and GO with sodium dodecyl sulfate in deionized water and performing ultrasonic dispersion, and finally mixing with the basic electro-deposition solution while applying mechanical stirring and ultrasonic waves to the electro-deposition solution for 1 h.

[0014] (d) Immersing the anode nickel plate and the cathode magnesium alloy sample in the electro-deposition solution and placing them in an ultrasonic generator, with the positive and negative poles of the pulse power source connected to the anode and cathode, respectively, and the ultrasonic generator working in a variable frequency manner.

[0015] Further, the specific steps of the above process are as follows:

[0016] (1) Mechanical polishing, polishing and polishing the magnesium alloy, and then performing ethanol ultrasonic cleaning and deionized water cleaning.

[0017] (2) Alkaline cleaning to remove oil, using the saponification of an alkaline solution to remove oil on the surface of the magnesium alloy, with the composition of the alkaline solution being sodium hydroxide 30-50 g / L, sodium phosphate 30-35 g / L, and sodium carbonate 10-12 g / L, and after alkaline cleaning at 60-70°C for 15-20 min, performing deionized water cleaning.

[0018] Preferably, the sodium hydroxide is 35 g / L, the sodium phosphate is 30 g / L, the sodium carbonate is 11 g / L, the temperature is 65°C, and the time is 20 min.

[0019] (3) Chromium-free pickling, using an acid solution mainly containing phosphoric acid with a mass fraction of 85% and a concentration of 580-620 cm 3 / L to pickling for 35-45 s to remove oxides on the surface of the magnesium alloy, and then performing deionized water cleaning.

[0020] Preferably, the concentration of phosphoric acid is 600 cm 3 / L, and the pickling time is 40 s.

[0021] (4) Surface conditioning, using a pyrophosphate system to perform surface conditioning on the magnesium alloy at 65-70°C for 2-2.5 min to remove oxides during pickling and slightly etch and flatten the surface of the β phase of the magnesium alloy to fully expose the substrate, with the surface conditioning solution including potassium pyrophosphate 150-170 g / L, sodium carbonate 18-22 g / L, and potassium fluoride 8-12 g / L, and after surface conditioning, performing deionized water cleaning.

[0022] Preferably, the potassium pyrophosphate is 160 g / L, the sodium carbonate is 20 g / L, the potassium fluoride is 11 g / L, the surface conditioning temperature is 70°C, and the time is 2.5 min.

[0023] (5) Activation, using a mixed solution of phosphoric acid 170-190 ml / L and ammonium hydrogen fluoride 90-100 g / L at room temperature for 2-2.5 min to remove oxides and form a magnesium fluoride protective film layer. After activation, the solution is washed with deionized water.

[0024] Preferably, the phosphoric acid is 180 ml / L, the ammonium hydrogen fluoride is 95 g / L, and the activation time is 2.5 min.

[0025] (6) Inner layer electroless nickel plating solution includes nickel sulfate 20-25 g / L, sodium hypophosphite 20-25 g / L, sodium citrate 18-22 g / L, ammonium hydrogen fluoride 10-12 g / L, and sodium carbonate 18-22 g / L. The plating process is as follows: plating temperature is 70-75°C, PH is adjusted to 9.00-9.25, plating time is 45-55 min, and magnetic stirring rate is 210 r / min.

[0026] Preferably, the nickel sulfate is 20 g / L, the sodium hypophosphite is 25 g / L, the sodium citrate is 20 g / L, the ammonium hydrogen fluoride is 10 g / L, and the sodium carbonate is 20 g / L; the plating temperature is 75°C, the PH is 9.25, and the plating time is 50 min.

[0027] (7) Outer layer electroless nickel plating solution includes nickel sulfate 20-25 g / L, sodium hypophosphite 20-25 g / L, citric acid 4-6 g / L, and ammonium hydrogen fluoride 18-22 g / L. The plating process is as follows: plating temperature is 80-85°C, PH is adjusted to 6.00-6.25, plating time is 45-55 min, and magnetic stirring rate is 210 r / min.

[0028] Preferably, the nickel sulfate is 20 g / L, the sodium hypophosphite is 20 g / L, the citric acid is 5 g / L, and the ammonium hydrogen fluoride is 20 g / L; the plating temperature is 80°C, the PH is 6.25, and the plating time is 50 min.

[0029] (8) The base electrodeposition solution is prepared according to the main salt formula, and the components are: nickel sulfate 110-130 g / L, ammonium citrate 8-12 g / L, ammonium hydrogen fluoride 35-50 g / L, sodium saccharin 3 g / L, and ammonia water 35-45 ml / L.

[0030] Preferably, the nickel sulfate is 120 g / L, the ammonium citrate is 10 g / L, the ammonium hydrogen fluoride is 40 g / L, and the ammonia water is 40 ml / L.

[0031] (9) TiN (content 1-7 g / L), GO (content 0.05-0.25 g / L), and 0.1 g / L sodium dodecyl sulfate are mixed with an appropriate amount of deionized water, and mechanical stirring and ultrasonic waves are applied to disperse the mixture. The dispersed solution is added to the base electrodeposition solution and continues to disperse for 1 h.

[0032] Preferably, the TiN content is 1 g / L and the GO content is 0.1 g / L.

[0033] (10) The anode nickel plate and the cathode magnesium alloy sample are immersed in the electroplating solution and placed in an ultrasonic generator, and the positive and negative poles of the pulse power source are connected to the anode and the cathode, respectively.

[0034] Preferably, the area ratio of the anode to the cathode is 2:3, and the inter-electrode distance is 25 mm.

[0035] (11) The Ni-TiN is electrodeposited by the following process: the voltage is 3 V, the current density is 1.5-3 A·cm -2 , the duty cycle is 35-80%, the ultrasonic power is 150-240 W, the ultrasonic frequency is 45 KH Z and 80 KH Z alternately for 10-20 s, the magnetic stirring rate is 300 r / min, the deposition temperature is 55°C, and the deposition time is 75 min.

[0036] Preferably, the current density is 2 A·cm -2 , the duty cycle is 80%, the ultrasonic power is 210 W, the ultrasonic frequency is 45 KH Z and 80 KH Z alternately for 10 s and 20 s.

[0037] The beneficial effects of the present application compared with the prior art are:

[0038] (1) The ultrasonic frequency of the nano nickel-based composite layer preparation method of the present application is controllable, which can better disperse the nanoparticles, is conducive to the uniform deposition of the nanoparticles with metal atoms, plays a role of dispersion strengthening and heterogeneous nucleation, in addition, the strong shock action of high ultrasonic frequency can break and interrupt the growth trend of larger grains and cause the change of interface energy, promote the growth of grains in different directions, improve the nucleation rate, and the strong mechanical shearing action will constantly flush the grain tips while breaking the grains, so as to smooth the growing grains.

[0039] (2) The plating solution does not contain Cl - which can destroy the plating layer, so that the magnesium alloy can be deposited with a smooth plating layer in the plating solution.

[0040] (3) The TiN in the plating solution can be co-deposited with Ni 2+ , on the one hand, the TiN can become a heterogeneous nucleation site to provide a large number of nucleation centers for Ni 2+ , playing a role of fine-grain strengthening; on the other hand, the TiN particles are dispersedly distributed in the plating layer, which can hinder the movement of dislocations and improve the hardness of the plating layer.

[0041] (4) GO is a derivative of graphene in the plating solution, and its ultrathin and two-dimensional honeycomb lattice structure makes it have a large specific surface area, high mechanical strength and excellent lubricity. GO can adsorb Ni 2+ and TiN nanoparticles due to its electronegativity, improve the deposition efficiency, and as second-phase particles dispersedly distributed on the surface of the material, can act as heterogeneous nucleation sites to improve the nucleation rate to a certain extent, reduce defects, effectively refine the grains, and improve the hardness of the coating. In addition, the sheet-like distribution of GO in the coating can prolong the corrosion path and improve the corrosion resistance.

[0042] The application provides a preparation method of a magnesium alloy surface variable-frequency power ultrasonic electrodeposited nanometer nickel-based composite layer, and the deposition layer prepared by the method is uniform and dense, has a bright appearance, and has no peeling and falling. The hardness (600-750 HV) of the deposition layer is 8.5-10.8 times higher than that of the substrate, and the self-corrosion current density is 2-3 orders of magnitude lower than that of the substrate, which indicates that the coating has high hardness and excellent corrosion resistance. BRIEF DESCRIPTION OF DRAWINGS

[0043] The application will be further described below in combination with the drawings and examples:

[0044] Figure 1 Fig. 1 is a surface metallographic morphology diagram of the deposition layer of Examples 1-5 amplified 800 times. (a) Example 1 (b) Example 2 (c) Example 3 (d) Example 4 (e) Example 5.

[0045] Figure 2 Fig. 2 is a cross-sectional metallographic morphology diagram of the deposition layer of Examples 1-5 amplified 800 times. (a) Example 1 (b) Example 2 (c) Example 3 (d) Example 4 (e) Example 5 (f) cross-sectional thickness value.

[0046] Figure 3 Fig. 3 is a microhardness diagram of the deposition layer of Examples 1-5.

[0047] Figure 4 Fig. 4 is a polarization curve diagram of the deposition layer of Examples 1-5.

[0048] Figure 5 Fig. 5 is a macroscopic morphology diagram of the comparative examples. (a) Comparative Example 1 (b) Comparative Example 2 (c) Comparative Example 3 (d) Comparative Example 4. DETAILED DESCRIPTION

[0049] The application will be further described below in combination with the drawings and examples:

[0050] In one or more embodiments of the embodiment, the specific preparation process is as follows:

[0051] (1) The substrate is leveled by mechanically leveling the surface of the substrate material to reduce its surface roughness, including grinding and polishing. AZ91D magnesium alloy is ground using 360 grit, 600 grit, 800 grit, 1000 grit, 1200 grit, 1500 grit, and 2000 grit wet sandpaper. From a materials science perspective, the substrate surface should be ground from two perpendicular directions, with the number of grinding passes in both directions being as consistent as possible. Simultaneously, the grinding marks should be small and uniform to ensure both the adhesion between the coating and the substrate and to maintain the smoothness of the coating.

[0052] (2) The substrate undergoes surface treatment to remove any dust, grease, oxides, and to form a protective magnesium fluoride film. First, it is subjected to 80KH Z The substrate was subjected to ultrasonic cleaning at 180W for 10 minutes with ethanol, followed by rinsing with deionized water. Then, the substrate was placed in a degreasing alkaline solution at 60-70℃ for 15-20 minutes to remove any remaining grease. The degreasing alkaline solution consisted of 30-50 g / L sodium hydroxide, 30-35 g / L sodium phosphate, 10-12 g / L sodium carbonate, and water as the balance. After alkaline cleaning, the substrate was rinsed with deionized water. Finally, the substrate was acid-washed at room temperature for 35-45 seconds to remove oxides from the magnesium alloy surface. The acid-washing solution mainly consisted of 85% phosphoric acid at 580-620 cm⁻¹. 3 The magnesium alloy was pickled and then rinsed with deionized water. Afterward, the magnesium alloy was surface-conditioned at 65–70°C for 2–2.5 min 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 magnesium alloy was rinsed with deionized water. Finally, the magnesium alloy was activated at room temperature for 2–2.5 min 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 magnesium alloy was rinsed with deionized water.

[0053] (3) After surface treatment of the substrate, it is immediately placed in a constant temperature water bath for inner layer electroless nickel-phosphorus plating. The components of the inner layer electroless nickel-phosphorus plating solution are: nickel sulfate 20-25 g / L, sodium hypophosphite 20-25 g / L, sodium citrate 18-22 g / L, ammonium bifluoride 10-12 g / L, and sodium carbonate 18-22 g / L. During the electroless plating process, the temperature is 70-75℃, the pH is adjusted to 9.00-9.25 with an alkaline solution, the plating time is 50 min, and the magnetic stirring speed is 210 r / min.

[0054] (4) Inner layer electroless nickel-phosphorus plating, then clean the surface with deionized water, and place it in a constant temperature water bath for outer layer electroless nickel-phosphorus plating. The composition of the plating solution for outer layer electroless nickel-phosphorus plating is nickel sulfate 20-25 g / L, sodium hypophosphite 20-25 g / L, citric acid 4-6 g / L, and ammonium hydrogen fluoride 18-22 g / L. During the electroless plating process, the temperature is 80-85 °C, the pH of the alkaline solution is adjusted to 6.00-6.25, the plating time is 50 min, and the magnetic stirring rate is 210 r / min.

[0055] (5) After the outer layer electroless nickel-phosphorus plating is completed, since the plating solution is in an acidic environment, the plated layer needs to be quickly taken out of the water bath, the stirring is stopped, and deionized water is used for cleaning and hot air drying for standby.

[0056] (6) Prepare a basic electrodeposition solution according to the main salt formula, which contains nickel sulfate 110-130 g / L, ammonium citrate 8-12 g / L, ammonium hydrogen fluoride 35-50 g / L, sodium saccharin 3 g / L, and ammonia water 35-45 ml / L. Mix TiN (content 1-7 g / L), GO (content 0.05-0.25 g / L), and 0.1 g / L sodium dodecyl sulfate with an appropriate amount of deionized water, and apply mechanical stirring and ultrasonic waves to fully disperse the mixture. Add the dispersed solution to the basic electrodeposition solution and continue to disperse for 1 h.

[0057] (7) Immerse the anode nickel plate and cathode magnesium alloy sample in the electrodeposition solution and place them in an ultrasonic generator. The positive and negative poles of the pulse power source are connected to the anode and cathode, respectively. The electrodeposition process is as follows: voltage 3 V, current density 1.5-3 A·cm -2 , duty cycle 35-80%, ultrasonic power 150-240 W, ultrasonic frequency 45 KHz and 80 KHz alternating action for 10-20 s, magnetic stirring rate 300 r / min, deposition temperature 55 °C, and deposition time 75 min.

[0058] In order for those skilled in the art to have a clearer understanding of the technical solutions of the present disclosure, the technical solutions of the present disclosure will be described in detail below in conjunction with specific examples.

[0059] Example 1

[0060] A method for preparing a nano nickel-based composite layer on the surface of a magnesium alloy by frequency conversion power ultrasonic electrodeposition. The specific process flow is as follows:

[0061] (1) The substrate is polished with sandpaper and ultrasonically cleaned in ethanol solution for 2 min and deionized water for 2 min.

[0062] (2) Alkaline cleaning to remove oil, prepare an alkaline cleaning solution containing 35 g / L sodium hydroxide, 30 g / L sodium phosphate, and 10 g / L sodium carbonate, alkaline cleaning temperature 65 °C, alkaline cleaning time 15 min.

[0063] (3) No chromium pickling, a pickling solution mainly containing 600 cm 3 / L of phosphoric acid (mass fraction 85%) was configured, and after pickling, deionized water was used for rinsing for 1 min.

[0064] (4) Surface conditioning, a surface conditioning solution containing potassium pyrophosphate 160 g / L, sodium carbonate 20 g / L, potassium fluoride 11 g / L was configured, and the magnesium alloy was subjected to surface conditioning at 70°C for 2.5 min, and after surface conditioning, deionized water was used for rinsing for 1 min.

[0065] (5) Activation, an activation solution containing phosphoric acid 180 ml / L, ammonium hydrogen fluoride 95 g / L was configured, and the magnesium alloy was subjected to activation at room temperature for 2.5 min, and after activation, deionized water was used for rinsing for 1 min.

[0066] (6) Inner layer electroless nickel-phosphorus plating, an inner layer electroless nickel-phosphorus plating solution containing nickel sulfate 20 g / L, sodium hypophosphite 25 g / L, sodium citrate 20 g / L, ammonium hydrogen fluoride 10 g / L, sodium carbonate 20 g / L was configured, and the prepared plating solution was placed into a constant-temperature water bath at 75°C, and plating was performed for 50 min, and the magnetic stirring rate was 210 r / min.

[0067] (7) Outer layer electroless nickel-phosphorus plating, an outer layer electroless nickel-phosphorus plating solution containing nickel sulfate 20 g / L, sodium hypophosphite 20 g / L, citric acid 5 g / L, ammonium hydrogen fluoride 20 g / L was configured, and the prepared plating solution was placed into a constant-temperature water bath at 80°C, and plating was performed for 50 min, and the magnetic stirring rate was 210 r / min.

[0068] (8) A basic electrodeposition solution was prepared according to the main salt formula, and the components were: nickel sulfate 120 g / L, ammonium citrate 10 g / L, ammonium hydrogen fluoride 40 g / L, sodium saccharin 3 g / L, ammonia water 40 ml / L. TiN (content 7 g / L) and 0.1 g / L sodium dodecyl sulfate were mixed with an appropriate amount of deionized water, and mechanical stirring and ultrasonic wave were applied to the mixed solution for sufficient dispersion, and the dispersed solution was added to the basic electroplating solution for further dispersion for 1 h.

[0069] (9) The anode nickel plate and the cathode magnesium alloy sample were immersed in the electroplating solution and placed in an ultrasonic generator, and the positive and negative poles of the pulse power source were connected to the anode and the cathode respectively. The electrodeposition process was: voltage 3 V, current density 1.5 A·cm -2 , duty cycle 80%, ultrasonic power 240 W, ultrasonic frequency 45 KHz and 80 KHz alternately acting for 20 s and 20 s, magnetic stirring rate 300 r / min, deposition temperature 55°C, deposition time 75 min.

[0070] Figure 1(a) shows the metallographic surface morphology of the nano-nickel-based metal-ceramic composite layer prepared in this embodiment; the coating is uniform and dense. Figure 2 (a) From the metallographic cross-sectional morphology, no obvious cracks were observed, the coating was tightly bonded to the substrate, and the coating thickness was 36.4354 μm; the hardness test results are as follows: Figure 3 As shown, the microhardness of the composite layer is 668.48 HV, which is 9.63 times higher than that of the substrate (69.382 HV); the electrochemical corrosion resistance test results are as follows: Figure 4 As shown, the self-corrosion potential of the deposited layer is -0.253V, which is 1067mV positively shifted from the substrate (-1.32V), and the self-corrosion current density is 8.175×10⁻⁶ mV. -6 A·cm -2 Compared to the substrate (1.669×10 -4 A·cm -2 The significant decrease indicates that the hardness of the deposited layer has increased while its corrosion resistance has also increased significantly.

[0071] Example 2

[0072] A method for preparing a nano-nickel-based composite layer on the surface of a magnesium alloy by frequency conversion power ultrasonic electrodeposition. The specific process flow differs from that of Example 1 in that:

[0073] The TiN content in the electroplating solution is 1 g / L. The electrodeposition process is as follows: voltage 3V, current density 2A·cm⁻¹. -2 The parameters were: duty cycle 80%, ultrasonic power 210W, ultrasonic frequency 45KHz and 80KHz alternating for 10s and 20s, magnetic stirring rate 300r / min, deposition temperature 55℃, and deposition time 75min.

[0074] Figure 1 (b) shows the metallographic surface morphology of the nano-nickel-based metal-ceramic composite layer prepared in this embodiment; the coating is uniform and dense. Figure 2 (b) From the metallographic cross-sectional morphology, no obvious cracks were observed, the coating was tightly bonded to the substrate, and the coating thickness was 38.7766 μm; the hardness test results are as follows: Figure 3 As shown, the microhardness of the composite layer is 732.9 HV, which is 10.56 times higher than that of the substrate (69.382 HV); the electrochemical corrosion resistance test results are as follows: Figure 4 As shown, the self-corrosion potential of the deposited layer is -0.303V, which is 1017mV more positive than that of the substrate (-1.32V), and the self-corrosion current density is 1.848×10⁻⁶ mV. -6 A·cm -2 Compared to the substrate (1.669×10 -4 A·cm -2 The significant decrease indicates that the hardness of the deposited layer has increased while its corrosion resistance has also increased significantly.

[0075] Example 3

[0076] A method for preparing a nano nickel-based composite layer on a magnesium alloy surface by variable-frequency power ultrasonic electrodeposition. The difference between the specific process flow and Embodiment 1 is that:

[0077] The TiN content in the electroplating solution is 7 g / L. The electrodeposition process is: voltage 3 V, current density 3 A·cm -2 , duty cycle 50%, ultrasonic power 210 W, ultrasonic frequency 45 KHz and 80 KHz alternately acting for 10 s and 10 s, magnetic stirring rate 300 r / min, deposition temperature 55°C, and deposition time 75 min.

[0078] Figure 1 (c) The metallographic surface morphology of the nano nickel-based cermet composite layer prepared in this embodiment is uniform and dense; from Figure 2 (c) The metallographic cross-sectional morphology, there is no obvious cracking, the coating is tightly combined with the substrate, and the coating thickness is 35.1896 μm; the hardness test results are shown in Figure 3 , the microhardness of the composite layer is 664.18 HV, which is 9.57 times higher than the microhardness of the substrate (69.382 HV); the electrochemical corrosion resistance test is shown in Figure 4 , the deposition layer has a self-corrosion potential of -0.325 V, which is positively shifted by 995 mV compared with the substrate (-1.32 V), and the self-corrosion current density is 6.320×10 -6 A·cm -2 , which is significantly lower than that of the substrate (1.669×10 -4 A·cm -2 ), indicating that the deposition layer has significantly improved corrosion resistance while increasing the hardness.

[0079] Embodiment 4

[0080] A method for preparing a nano nickel-based composite layer on a magnesium alloy surface by variable-frequency power ultrasonic electrodeposition. The difference between the specific process flow and Embodiment 1 is that:

[0081] The TiN content in the electroplating solution is 1 g / L, and the GO content is 0.05 g / L. The electrodeposition process is: voltage 3 V, current density 2 A·cm -2 , duty cycle 80%, ultrasonic power 210 W, ultrasonic frequency 45 KHz and 80 KHz alternately acting for 10 s and 20 s, magnetic stirring rate 300 r / min, deposition temperature 55°C, and deposition time 75 min.

[0082] Figure 1 (d) The metallographic surface morphology of the nano nickel-based cermet composite layer prepared in this embodiment is uniform and dense; from Figure 2 (d) The metallographic cross-sectional morphology, there is no obvious cracking, the coating is tightly combined with the substrate, and the coating thickness is 38.8742 μm; the hardness test results are shown inFigure 3 As shown, the microhardness of the composite layer is 734.68 HV, which is 10.59 times higher than the microhardness of the substrate (69.382 HV); the electrochemical corrosion resistance test is as shown in Figure 4 As shown, the self-corrosion potential of the deposited layer is -0.287 V, which is positively shifted by 1033 mV compared with the substrate (-1.32 V), and the self-corrosion current density is 1.832 x 10 -6 A·cm -2 A·cm -4 A·cm -2 A·cm -2 A·cm -7 A·cm -2 A·cm -4 A·cm -2 A·cm

[0083] Example 5

[0084] A method for preparing a nano-nickel-based composite layer on a magnesium alloy surface by frequency conversion power ultrasonic electrodeposition. The specific process flow is different from that of Example 1 in that:

[0085] The content of TiN in the electroplating solution is 1 g / L, and the content of GO is 0.1 g / L. The electrodeposition process is as follows: voltage 3 V, current density 2 A·cm -2 , duty cycle 80%, ultrasonic power 210 W, ultrasonic frequency 45 KHz and 80 KHz alternately acting for 10 s and 20 s, magnetic stirring rate 300 r / min, deposition temperature 55°C, and deposition time 75 min.

[0086] Figure 1 (e) The metallographic surface morphology of the nano-nickel-based cermet composite layer prepared in this example is uniform and dense; from Figure 2 (e) From the metallographic cross-sectional morphology, no obvious cracking is observed, the plated layer is tightly combined with the substrate, and the plated layer thickness is 41.6958 μm; the hardness test results are as shown in Figure 3 As shown, the microhardness of the composite layer is 744.9 HV, which is 10.74 times higher than the microhardness of the substrate (69.382 HV); the electrochemical corrosion resistance test is as shown in Figure 4 As shown, the self-corrosion potential of the deposited layer is -0.249 V, which is positively shifted by 1071 mV compared with the substrate (-1.32 V), and the self-corrosion current density is 7.517 x 10 -7 A·cm -2 A·cm -4 A·cm -2 A·cm

[0087] The effects of the comparative examples and the technical solutions of the present application are compared:

[0088] The effect evaluation of the comparative examples is shown in Table 1.

[0089] Table 1 Comparative effect evaluation of magnesium alloy electrodeposition layer

[0090]

[0091]

[0092] The above-described embodiments are merely preferred embodiments of the present application and are not all possible implementations of the present application. Any obvious modifications made by those of ordinary skill in the art to the present application without departing from the principles and spirit of the present application should be considered to be within the scope of the claims of the present application.

Claims

1. A method for preparing a magnesium alloy surface variable-frequency power ultrasonic electrodeposited nanometer nickel-based composite layer, characterized in that a magnesium alloy sample after chemical pre-deposition is used as a cathode, a nickel plate with a purity greater than 99% is used as an anode, the two are respectively connected to the negative and positive poles of a pulse power supply, are immersed in a pre-prepared electrodeposition solution, and are placed in an ultrasonic generator for electrodeposition, and the ultrasonic generator works in a variable-frequency mode. The basic electrodeposition solution is prepared according to a main salt formula, and the components are: nickel sulfate 120 g / L, ammonium citrate 10 g / L, ammonium hydrogen fluoride 40 g / L, sodium saccharin 3 g / L, ammonia water 40 ml / L, TiN 1 g / L, GO 0.1 g / L, and 0.1 g / L sodium dodecyl sulfate. The electrodeposition process is: voltage 3 V, current density 2 A·cm -2 , duty cycle 80%, ultrasonic power 210 W, ultrasonic frequency 45 KHz and 80 KHz alternately acting for 10 s and 20 s, magnetic stirring rate 300 r / min, deposition temperature 55 DEG C, deposition time 75 min; The specific steps of the preparation method are as follows:

2. The method for preparing a nanometer nickel-based composite layer on the surface of a magnesium alloy by power ultrasonic electrodeposition with frequency conversion as claimed in claim 1, characterized in that, (a) Pretreatment: the magnesium alloy is sequentially polished, degreased, pickled, surface adjusted, and activated; (b) Chemical pre-deposition: the magnesium alloy sample after pretreatment is double-layer electroplated with nickel-phosphorus; (c) The electrodeposition solution is prepared according to the main salt formula, and the components are: nickel sulfate 120 g / L, ammonium citrate 10 g / L, ammonium hydrogen fluoride 40 g / L, sodium saccharin 3 g / L, ammonia water 40 ml / L, TiN 1 g / L, GO 0.1 g / L, and 0.1 g / L sodium dodecyl sulfate; nickel sulfate is added to ammonium citrate, and then ammonium hydrogen fluoride, sodium saccharin, and ammonia water are sequentially added thereto to form a basic electrodeposition solution, then TiN and GO are mixed with deionized water and ultrasonically dispersed with 0.1 g / L sodium dodecyl sulfate, and finally mixed with the basic electrodeposition solution while mechanical stirring and ultrasonic dispersion are applied to the electrodeposition solution for 1 h; (d) The anode nickel plate and the cathode magnesium alloy sample are immersed in the electrodeposition solution and placed in the ultrasonic generator, the positive and negative poles of the pulse power supply are respectively connected to the anode and the cathode, and the ultrasonic generator works in a variable-frequency mode. The area ratio of the anode to the cathode is 2:3, and the distance between the two poles is 25 mm.

3. The method according to claim 2, wherein the method is characterized in that, ​

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