CN116065208A

CN116065208A - Preparation method of variable-frequency power ultrasonic electro-deposition nano nickel-based composite layer on magnesium alloy surface

Info

Publication number: CN116065208A
Application number: CN202310065355.8A
Authority: CN
Inventors: 李智; 胡德枫
Original assignee: Dalian University
Current assignee: Dalian University
Priority date: 2023-01-12
Filing date: 2023-01-12
Publication date: 2023-05-05

Abstract

The invention discloses a preparation method of a variable-frequency power ultrasonic electro-deposition nano nickel-based composite layer on a magnesium alloy surface, and belongs to the technical field of preparation of a coating layer on a metal substrate surface. The electrodepositing solution comprises 110-130 g/L of nickel sulfate, 8-12 g/L of ammonium citrate, 35-50 g/L of ammonium bifluoride, 3g/L of saccharin sodium, 35-45 ml/L of ammonia water, 1-7 g/L of TiN and GO0.05-0.25 g/L (auxiliary addition). The preparation method comprises the following specific steps: the voltage is 3V, and the current density is 1.5-3A cm ^‑2 Duty ratio is 35-80%, ultrasonic power is 150-240W, ultrasonic frequency is 45KH _Z And 80KH _Z Alternately acting for 10-20 s, and magnetically stirring at the speed of 300r/min, wherein the deposition temperature is 55 ℃ and the deposition time is 75min. The formed deposit layer has bright appearance, no peeling and falling, hardness 8.5-10.8 times higher than that of the matrix, self-corrosion current density 2-3 orders of magnitude lower than that of the matrix, high hardness and excellent corrosion resistance.

Description

Preparation method of variable-frequency power ultrasonic electro-deposition nano nickel-based composite layer on magnesium alloy surface

Technical Field

The invention belongs to the technical field of preparation of a coating layer on a metal substrate surface, and relates to a preparation method of a variable-frequency power ultrasonic electrodeposited nano nickel-based composite layer on a magnesium alloy surface. In particular to an electrodeposition liquid and an electrodeposition process for an AZ91D magnesium alloy.

Background

The magnesium alloy has the characteristics of low density, high specific strength, high dimensional stability, good impact resistance and electromagnetic shielding capability, and easy recovery, is widely focused as an environment-friendly material, and is widely applied to AZ91D casting magnesium alloy at present, but the large-scale application of the magnesium alloy is severely restricted by poor corrosion resistance.

The components of the common electrodeposited layer on the surface of the magnesium alloy are copper, aluminum and nickel. Copper-based deposit layers are often used in electronic devices due to high electrical and thermal conductivity, but copper-based deposit layers have low tensile strength, poor wear resistance, high corrosion rate, and in order to ensure film-based binding force, plating solutions contain highly toxic cyanide; aluminum and magnesium are light metals, the potential difference between a deposited layer and a substrate can be greatly reduced by depositing aluminum, and galvanic corrosion is reduced, but the deposited aluminum needs an anhydrous environment, and has higher requirements on equipment and complex process.

With the development of nano science and technology, the nano composite electrodeposition technology is widely focused, the process is simple, the operation is convenient, the co-deposition of matrix metal and nano particles can be realized under the action of an electric field by adding nano particles into a deposition solution, and the prepared nano nickel-based metal ceramic composite layer has excellent wear resistance, corrosion resistance and high-temperature oxidation resistance and is widely applied. The conventional method for preparing the nano-particles is direct current deposition and auxiliary mechanical stirring, but the problem of agglomeration of the nano-particles in the plating solution cannot be well solved, so that the hardness and corrosion resistance of the prepared deposition layer are not ideal. In addition, the conventional wattage nickel plating solution (including improvement) widely used is not suitable for magnesium alloy, and although a pre-plating layer is prepared on the surface of the magnesium alloy, a bright nickel plating layer with excellent performance is still difficult to form, for example, the improved wattage nickel plating solution (application number CN 202110383810) of the adaptive alloy steel disclosed in the earlier stage of the subject group is applied to the electrodeposition of the magnesium alloy, and a great amount of skinning phenomenon occurs in the obtained nickel plating layer.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention provides a preparation method of a variable-frequency power ultrasonic electrodeposited nano nickel-based composite layer on the surface of a magnesium alloy, which comprises an electrodepositing liquid adapting to AZ91D magnesium alloy and a variable-frequency power ultrasonic pulse electrodepositing method, wherein the appearance of a formed deposited layer is bright, peeling and falling are not seen by adjusting ultrasonic frequency and ultrasonic power to reduce agglomeration of nano particles in the composite electrodepositing process in an ultrasonic generator, the hardness (600-750 HV) is improved by 8.5-10.8 times compared with a matrix, the self-corrosion current density is reduced by 2-3 orders of magnitude compared with the matrix, and the self-corrosion current density is high in hardness and excellent in corrosion resistance.

The above object of the present invention is achieved by the following technical solutions:

a method for preparing nano nickel-base composite layer by ultrasonic deposition with variable frequency power on magnesium alloy surface includes using magnesium alloy sample after chemical pre-deposition as cathode, using nickel plate with purity higher than 99% as anode, connecting both to negative and positive poles of pulse power source respectively, immersing them in pre-prepared electroplating solution, placing them in ultrasonic generator for electrodeposition, and operating ultrasonic generator in variable frequency mode.

Aiming at the preparation method, the invention provides an electrodeposition liquid for adapting to magnesium alloy, which comprises the following specific components: 110-130 g/L of nickel sulfate, 8-12 g/L of ammonium citrate, 35-50 g/L of ammonium bifluoride, 3g/L of saccharin sodium, 35-45 ml/L of ammonia water, 1-7 g/L of TiN, 0.05-0.25 g/L of GO (auxiliary addition), and 0.1g/L of sodium dodecyl sulfate.

In the electrodeposition liquid of the adaptive magnesium alloy, nickel sulfate provides nickel ions; ammonium citrate is used 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 bifluoride is used as a corrosion inhibitor and an accelerator to promote the reaction and ensure that the magnesium alloy is not corroded in the plating solution; tiN as reinforcing phase capable of reacting with Ni ²⁺ Co-deposition, further improving the coating performance; the GO is used as an auxiliary additive, so that the moving speed of metal particles and nano particles to a cathode can be promoted, the appearance of a coating is further improved, and the corrosion resistance is improved; sodium dodecyl sulfate as a surfactant can promote wettability of the nanoparticles and GO in water, and is better mixed with the solution. The proportion of the components of the plating solution can obtain good deposition rate and ensureThe magnesium alloy is not corroded in the plating process, so that a plating layer with good combination, high hardness and high corrosion resistance can be obtained.

The invention further provides an electrodeposition process under the deposition solution, which comprises the following steps:

(a) Pretreatment: sequentially polishing, degreasing, pickling, surface conditioning and activating the magnesium alloy.

(b) Chemical pre-deposition: and carrying out double-layer chemical nickel-phosphorus plating on the magnesium alloy sample after pretreatment.

(c) Preparing an electrodeposition liquid according to a main salt formula, adding nickel sulfate into ammonium citrate, sequentially adding ammonium bifluoride, saccharin sodium and ammonia water into the mixture to form a basic electrodeposition liquid, mixing TiN and GO with sodium dodecyl sulfate by deionized water, performing ultrasonic dispersion, finally mixing the mixture with the basic electrodeposition liquid, and simultaneously applying mechanical stirring and ultrasonic waves to fully disperse the electrodeposition liquid for 1h.

(d) Immersing anode nickel plate and cathode magnesium alloy sample in electrodeposit liquid and placing in ultrasonic generator, positive and negative poles of pulse power source are connected with anode and cathode respectively, ultrasonic generator works in frequency conversion mode.

Further, the specific steps of the process are as follows:

(1) Mechanically polishing, namely polishing the magnesium alloy, and performing ethanol ultrasonic cleaning and deionized water cleaning after polishing.

(2) Alkaline washing to remove oil, removing greasy dirt on the surface of the magnesium alloy by saponification of an alkaline solution, wherein the alkaline solution comprises 30-50 g/L of sodium hydroxide, 30-35 g/L of sodium phosphate, 10-12 g/L of sodium carbonate, and washing with deionized water after alkaline washing for 15-20 min at 60-70 ℃.

Preferably, 35g/L of sodium hydroxide, 30g/L of sodium phosphate, 11g/L of sodium carbonate, and the temperature is 65 ℃ for 20min.

(3) Chromium-free pickling, mainly comprising 85% by mass and with the concentration of 580-620 cm ³ Acid solution of/L phosphoric acid is used for pickling for 35-45 s, oxide on the surface of the magnesium alloy is removed, and deionized water is used for cleaning after pickling.

Preferably, the phosphoric acid concentration is 600cm ³ Acid washing time/L40s。

(4) And (3) performing surface conditioning for 2-2.5 min at 65-70 ℃ by adopting a pyrophosphate system, removing oxides during pickling, slightly etching and leveling the surface of the beta phase of the magnesium alloy to fully expose the matrix, wherein the surface conditioning solution comprises 150-170 g/L of potassium pyrophosphate, 18-22 g/L of sodium carbonate and 8-12 g/L of potassium fluoride, and cleaning with deionized water after surface conditioning.

Preferably, 160g/L of potassium pyrophosphate, 20g/L of sodium carbonate and 11g/L of potassium fluoride, and the surface temperature is 70 ℃ for 2.5min.

(5) Activating by using 170-190 ml/L of phosphoric acid and 90-100 g/L of ammonium bifluoride mixed solution for 2-2.5 min at room temperature, removing oxide and generating a magnesium fluoride protective film layer, and cleaning by deionized water after activation.

Preferably, the phosphoric acid is 180ml/L, the ammonium bifluoride is 95g/L, and the activation time is 2.5min.

(6) The inner layer chemical nickel-phosphorus plating solution comprises 20-25 g/L of nickel sulfate, 20-25 g/L of sodium hypophosphite, 18-22 g/L of sodium citrate, 10-12 g/L of ammonium bifluoride and 18-22 g/L of sodium carbonate. The plating process comprises the following steps: the plating temperature is 70-75 ℃, the PH is adjusted to 9.00-9.25, the plating time is 45-55 min, and the magnetic stirring rate is 210r/min.

Preferably, 20g/L of nickel sulfate, 25g/L of sodium hypophosphite, 20g/L of sodium citrate, 10g/L of ammonium bifluoride and 20g/L of sodium carbonate; the plating temperature is 75 ℃, the PH is 9.25, and the plating time is 50min.

(7) The outer layer is chemically plated with nickel and phosphorus, and the plating solution comprises 20 to 25g/L of nickel sulfate, 20 to 25g/L of sodium hypophosphite, 4 to 6g/L of citric acid and 18 to 22g/L of ammonium bifluoride. The plating process comprises the following steps: the plating temperature is 80-85 ℃, the PH is regulated to 6.00-6.25, the plating time is 45-55 min, and the magnetic stirring rate is 210r/min.

Preferably, nickel sulfate 20g/L, sodium hypophosphite 20g/L, citric acid 5g/L, ammonium bifluoride 20g/L; the plating temperature is 80 ℃, the PH is 6.25, and the plating time is 50min.

(8) The basic electrodeposition liquid is prepared according to a main salt formula, and comprises the following components: 110-130 g/L nickel sulfate, 8-12 g/L ammonium citrate, 35-50 g/L ammonium bifluoride, 3g/L saccharin sodium and 35-45 ml/L ammonia water.

Preferably, the nickel sulfate is 120g/L, the ammonium citrate is 10g/L, the ammonium bifluoride is 40g/L and the ammonia water is 40ml/L.

(9) Mixing TiN (content is 1-7 g/L), GO (content is 0.05-0.25 g/L) and 0.1g/L sodium dodecyl sulfate with proper deionized water, simultaneously applying mechanical stirring and ultrasonic wave to fully disperse the mixed solution, and adding the dispersed solution into the basic electroplating solution for continuous dispersion for 1h.

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

(10) Immersing anode nickel plate and cathode magnesium alloy sample in electroplating solution and placing in ultrasonic generator, positive and negative poles of pulse power source are respectively connected with anode and cathode.

Preferably, the cathode-anode area ratio is 2:3, and the electrode spacing is 25mm.

(11) The electro-deposition Ni-TiN comprises the following steps: the voltage is 3V, and the current density is 1.5-3A cm ^-2 Duty ratio is 35-80%, ultrasonic power is 150-240W, ultrasonic frequency is 45KH _Z And 80KH _Z Alternately acting for 10-20 s, and magnetically stirring at the speed of 300r/min, wherein the deposition temperature is 55 ℃ and the deposition time is 75min.

Preferably, the current density is 2A cm ^-2 Duty ratio 80%, ultrasonic power 210W, ultrasonic frequency 45KH _Z And 80KH _Z Alternating the application times 10s and 20s.

Compared with the prior art, the invention has the beneficial effects that:

(1) The preparation method of the nano nickel-based composite layer has controllable ultrasonic frequency, can better disperse nano particles, is favorable for uniform deposition along with metal atoms, plays roles of dispersion strengthening and heterogeneous nucleation, can break and break the growth trend of larger crystal grains and cause the change of interface energy due to the strong vibration effect of high ultrasonic frequency, promotes the crystal grains to grow in different directions, improves nucleation rate, and can continuously wash the tips of the crystal grains when breaking the crystal grains due to the strong mechanical shearing effect, so that the grown crystal grains are smooth.

(2) The plating solution does not contain Cl which damages the plating layer ^- Can ensure that the magnesium alloy deposits the coating steadily in the plating solution.

(3) TiN and Ni in the plating solution ²⁺ Co-deposition, on the one hand TiN can become heterogeneous nucleation sites, ni ²⁺ Providing a large number of nucleation centers and playing a role in fine grain strengthening; on the other hand, tiN particles are mixed in the coating and are dispersed, dislocation movement can be prevented, and the hardness of the coating is improved.

(4) GO in the plating solution is a derivative of graphene, and has an ultrathin and two-dimensional honeycomb lattice structure, so that the graphene has extremely large specific surface area, high mechanical strength and excellent lubricity, and the GO can adsorb positively charged Ni due to electronegativity ²⁺ And TiN nano particles, improve the deposition efficiency, as the second phase particles disperse and distribute on the surface of the material as heterogeneous nucleation sites to a certain extent, improve nucleation rate, reduce defects and effectively refine crystal grains, improve the hardness of the coating, and in addition, GO is distributed in lamellar form on the coating, can prolong the corrosion path and improve the corrosion resistance.

The invention provides a preparation method of a variable-frequency power ultrasonic electrodeposited nano nickel-based composite layer on the surface of a magnesium alloy, which is characterized in that the deposited layer prepared by the method is uniform and compact, has bright appearance, does not peel and fall off, has hardness (600-750 HV) which is 8.5-10.8 times higher than that of a matrix, and has self-corrosion current density which is reduced by 2-3 orders of magnitude than that of the matrix, thus indicating that the coating has high hardness and excellent corrosion resistance.

Drawings

The invention is further illustrated by the following examples in conjunction with the accompanying drawings:

FIG. 1 is a surface metallographic structure morphology at 800 times magnification of a deposited layer of an example. (a) example 1 (b) example 2 (c) example 3 (d) example 4 (e) example 5.

FIG. 2 is a cross-sectional metallographic structure morphology at 800 times magnification of the deposited layer of the example. (a) cross-sectional thickness values of example 1 (b) example 2 (c) example 3 (d) example 4 (e) example 5 (f).

FIG. 3 is a microhardness map of the deposited layers of examples 1-5.

FIG. 4 is a polarization graph of the deposited layers of examples 1-5.

Fig. 5 is a graph of comparative macro topography. (a) comparative example 1 (b) comparative example 2 (c) comparative example 3 (d) comparative example 4.

Detailed Description

The present invention is described in detail below by way of specific examples, but the scope of the present invention is not limited thereto. Unless otherwise specified, the test methods employed in the present invention are conventional, and the test materials used and the like are commercially available.

In one or more examples of this embodiment, the specific preparation process is as follows:

(1) The substrate is flattened, and the surface of the substrate material is mechanically flattened to reduce the surface roughness, including grinding, polishing, etc. The AZ91D magnesium alloy is polished, and the surface of the substrate is mechanically polished by water abrasive paper with 360 meshes, 600 meshes, 800 meshes, 1000 meshes, 1200 meshes, 1500 meshes and 2000 meshes respectively in the polishing process. In the polishing process, from the aspect of materialology, the surface of the base material is polished from two directions which are perpendicular to each other, the polishing times in the two directions are ensured to be consistent as much as possible, and meanwhile, the fineness and uniformity of polishing marks are ensured, so that the binding force between a plating layer and a base body is ensured, and the flatness of the plating layer is not influenced.

(2) The substrate is subjected to a surface treatment to remove dust, grease, oxides which may be present and to produce a protective magnesium fluoride film, first of all at 80KH _Z Washing with ethanol for 10min in 180W ultrasonic wave, and washing with deionized water; then placing the substrate in 60-70 ℃ degreasing alkali liquor for 15-20 min to clean grease possibly existing on the surface, wherein the degreasing alkali liquor comprises 30-50 g/L sodium hydroxide, 30-35 g/L sodium phosphate, 10-12 g/L sodium carbonate and water as the rest, and washing with deionized water after alkaline washing; then pickling the substrate at room temperature for 35-45 s to remove oxides on the surface of the magnesium alloy, wherein the main composition of the pickling solution is 580-620 cm phosphoric acid with the mass fraction of 85 percent ³ Washing with deionized water after pickling; then surface regulating magnesium alloy at 65-70 deg.c for 2-2.5 min to eliminate acid pickling corrosion product adsorbed onto the surface of the base body, and slightly etching beta phase of magnesium alloy to smooth the surface, and the surface regulating solution includes potassium pyrophosphate 150-170 g/L, sodium carbonate 18-22 g/L, potassium fluoride 8-12 g/L and water as the rest, and deionized water is used to flush after surface regulatingThe method comprises the steps of carrying out a first treatment on the surface of the And finally, activating the magnesium alloy at room temperature for 2-2.5 min, further dissolving the oxide to expose an active metal interface, generating a magnesium fluoride protective film, and washing the activated solution with deionized water after the activation, wherein the activated solution comprises 170-190 ml/L phosphoric acid, 90-100 g/L ammonium bifluoride and the balance of water.

(3) And (3) after the surface treatment is carried out on the base material, the base material is immediately placed in a constant-temperature water bath kettle to carry out inner-layer chemical nickel-phosphorus plating. The inner layer chemical nickel-phosphorus plating solution comprises 20-25 g/L of nickel sulfate, 20-25 g/L of sodium hypophosphite, 18-22 g/L of sodium citrate, 10-12 g/L of ammonium bifluoride and 18-22 g/L of sodium carbonate. In the chemical plating process, the temperature is 70-75 ℃, the PH of the alkaline solution is adjusted to 9.00-9.25, the plating time is 50min, and the magnetic stirring rate is 210r/min.

(4) After the inner layer is chemically plated with nickel and phosphorus, the surface is cleaned by deionized water, and the surface is placed in a constant temperature water bath for outer layer chemical plating of nickel and phosphorus. The plating solution for plating the outer layer with nickel and phosphorus comprises 20 to 25g/L of nickel sulfate, 20 to 25g/L of sodium hypophosphite, 4 to 6g/L of citric acid and 18 to 22g/L of ammonium bifluoride. In the chemical plating process, the temperature is 80-85 ℃, the PH of the alkaline solution is regulated to 6.00-6.25, the plating time is 50min, and the magnetic stirring rate is 210r/min.

(5) After the chemical plating of the outer layer with nickel and phosphorus is finished, the plating solution is in an acidic environment, the plating layer is required to be quickly taken out of the water bath, stirring is stopped, deionized water is used for cleaning, and hot air is used for drying for standby.

(6) The basic electrodeposition liquid is prepared according to a main salt formula, and comprises the following components: 110-130 g/L nickel sulfate, 8-12 g/L ammonium citrate, 35-50 g/L ammonium bifluoride, 3g/L saccharin sodium and 35-45 ml/L ammonia water. Mixing TiN (content of 1-7 g/L), GO (content of 0.05-0.25 g/L) and 0.1g/L sodium dodecyl sulfate with a proper amount of deionized water, simultaneously applying mechanical stirring and ultrasonic waves to fully disperse the mixed solution, and adding the dispersed solution into the basic electroplating solution for continuous dispersion for 1h.

(7) Immersing anode nickel plate and cathode magnesium alloy sample in electroplating solution and placing in ultrasonic generator, positive and negative poles of pulse power source are respectively connected with anode and cathode. The electrodeposition process is as follows: the voltage is 3V, the current density is 1.5-3A cm ^-2 Duty ratio is 35-80%, ultrasonic power is 150-ultra240W, the ultrasonic frequency is 45KHz and 80KHz alternately act for 10-20 s, the magnetic stirring speed is 300r/min, the deposition temperature is 55 ℃, and the deposition time is 75min.

In order to enable those skilled in the art to more clearly understand the technical solutions of the present disclosure, the technical solutions of the present disclosure will be described in detail below with reference to specific embodiments.

Example 1

A method for preparing a variable-frequency power ultrasonic electrodeposited nano nickel-based composite layer on the surface of a magnesium alloy. The specific process flow comprises the following steps:

(1) The substrate is sanded and polished by sand paper, and is ultrasonically cleaned in ethanol solution for 2min and deionized water for 2min.

(2) And (3) alkaline washing to remove oil, preparing alkaline washing solution containing 35g/L sodium hydroxide, 30g/L sodium phosphate and 10g/L sodium carbonate, wherein the alkaline washing temperature is 65 ℃ and the alkaline washing time is 15min.

(3) The composition mainly comprises 600cm ³ Phosphoric acid (85% by mass) pickling solution of/L, and washing with deionized water for 1min after pickling.

(4) Preparing a surface regulating solution containing 160g/L of potassium pyrophosphate, 20g/L of sodium carbonate and 11g/L of potassium fluoride, regulating the magnesium alloy at 70 ℃ for 2.5min, and flushing with deionized water for 1min after surface regulating.

(5) Activating, namely preparing an activating solution containing 180ml/L of phosphoric acid and 95g/L of ammonium bifluoride, activating the magnesium alloy for 2.5min at room temperature, and washing the magnesium alloy with deionized water for 1min after activation.

(6) Preparing an inner-layer chemical nickel-phosphorus plating solution containing 20g/L of nickel sulfate, 25g/L of sodium hypophosphite, 20g/L of sodium citrate, 10g/L of ammonium bifluoride and 20g/L of sodium carbonate, wherein the PH is 9.25, placing the prepared plating solution into a constant-temperature water bath kettle at 75 ℃, plating for 50min, and the magnetic stirring rate is 210r/min.

(7) Preparing an outer-layer chemical nickel-phosphorus plating solution containing 20g/L of nickel sulfate, 20g/L of sodium hypophosphite, 5g/L of citric acid and 20g/L of ammonium bifluoride, wherein the pH value is 6.25, placing the prepared plating solution into a constant-temperature water bath at 80 ℃, and plating for 50min with a magnetic stirring rate of 210r/min.

(8) The basic electrodeposition liquid is prepared according to a main salt formula, and comprises the following components: 120g/L nickel sulfate, 10g/L ammonium citrate, 40g/L ammonium bifluoride, 3g/L saccharin sodium and 40ml/L ammonia water. Mixing TiN (content 7 g/L) and 0.1g/L sodium dodecyl sulfate with proper deionized water, simultaneously applying mechanical stirring and ultrasonic wave to fully disperse the mixed solution, and adding the dispersed solution into the basic electroplating solution for continuous dispersion for 1h.

(9) Immersing anode nickel plate and cathode magnesium alloy sample in electroplating solution and placing in ultrasonic generator, positive and negative poles of pulse power source are respectively connected with anode and cathode. The electrodeposition process is as follows: voltage 3V, current density 1.5A cm ^-2 The duty ratio is 80%, the ultrasonic power is 240W, the ultrasonic frequency is 45KHz and 80KHz alternately act for 20s and 20s, the magnetic stirring speed is 300r/min, the deposition temperature is 55 ℃, and the deposition time is 75min.

FIG. 1 (a) shows the metallographic surface morphology of a nano nickel-based cermet composite layer prepared in the embodiment, and the coating is uniform and compact; from the metallographic cross-sectional morphology of FIG. 2 (a), no obvious cracking is seen, the coating is tightly combined with the matrix, and the thickness of the coating is 36.4354 mu m; the hardness test result is shown in fig. 3, wherein the microhardness of the composite layer is 668.48HV, which is 9.63 times higher than that of the matrix (69.382 HV); as shown in FIG. 4, the self-etching potential of the deposited layer is-0.253V, 1067mV forward movement compared with the substrate (-1.32V), and the self-etching current density is 8.175 ×10 ^-6 A·cm ^-2 Compared with the substrate (1.669×10) ^-4 A·cm ^-2 ) The corrosion resistance of the deposited layer is obviously improved while the hardness is obviously reduced.

Example 2

A method for preparing a variable-frequency power ultrasonic electrodeposited nano nickel-based composite layer on the surface of a magnesium alloy. The specific process flow is different from that of the embodiment 1 in that:

the TiN content in the electroplating solution is 1g/L. The electrodeposition process is as follows: voltage 3V, current density 2A cm ^-2 The duty ratio is 80%, the ultrasonic power is 210W, the ultrasonic frequency is 45KHz and 80KHz alternately act for 10s and 20s, the magnetic stirring speed is 300r/min, the deposition temperature is 55 ℃, and the deposition time is 75min.

FIG. 1 (b) shows a nano nickel-based cermet composite layer prepared in this exampleThe phase surface morphology and the plating layer are uniform and compact; from the metallographic cross-sectional morphology of FIG. 2 (b), no obvious cracking is seen, the coating is tightly combined with the matrix, and the thickness of the coating is 38.7766 mu m; the hardness test result is shown in fig. 3, wherein the microhardness of the composite layer is 732.9HV, which is 10.56 times higher than that of the matrix (69.382 HV); as shown in FIG. 4, the self-etching potential of the deposited layer is-0.303V, 1017mV forward than the substrate (-1.32V), and the self-etching current density is 1.848×10 ^-6 A·cm ^-2 Compared with the substrate (1.669×10) ^-4 A·cm ^-2 ) The corrosion resistance of the deposited layer is obviously improved while the hardness is obviously reduced.

Example 3

the TiN content in the plating solution was 7g/L. The electrodeposition process is as follows: voltage 3V, current density 3A cm ^-2 The duty ratio is 50%, the ultrasonic power is 210W, the ultrasonic frequency is 45KHz and 80KHz alternately act for 10s and 10s, the magnetic stirring speed is 300r/min, the deposition temperature is 55 ℃, and the deposition time is 75min.

FIG. 1 (c) shows the metallographic surface morphology of the nano nickel-based cermet composite layer prepared in the embodiment, and the coating is uniform and compact; from the metallographic cross-sectional morphology of FIG. 2 (c), no obvious cracking is seen, the coating is tightly combined with the matrix, and the thickness of the coating is 35.1896 mu m; the hardness test result is shown in fig. 3, wherein the microhardness of the composite layer is 664.18HV, which is 9.57 times higher than that of the matrix (69.382 HV); as shown in FIG. 4, the self-etching potential of the deposited layer is-0.325V, 995mV forward compared with the substrate (-1.32V), and the self-etching current density is 6.320 ×10 ^-6 A·cm ^-2 Compared with the substrate (1.669×10) ^-4 A·cm ^-2 ) The corrosion resistance of the deposited layer is obviously improved while the hardness is obviously reduced.

Example 4

TiN content in the plating solution 1g/L, GO content 0.05gand/L. The electrodeposition process is as follows: voltage 3V, current density 2A cm ^-2 The duty ratio is 80%, the ultrasonic power is 210W, the ultrasonic frequency is 45KHz and 80KHz alternately act for 10s and 20s, the magnetic stirring speed is 300r/min, the deposition temperature is 55 ℃, and the deposition time is 75min.

FIG. 1 (d) shows the metallographic surface morphology of the nano nickel-based cermet composite layer prepared in the embodiment, and the coating is uniform and compact; from the metallographic cross-sectional morphology of FIG. 2 (d), no obvious cracking is seen, the coating is tightly combined with the matrix, and the thickness of the coating is 38.8742 mu m; the hardness test result is shown in fig. 3, wherein the microhardness of the composite layer is 734.68HV, which is improved by 10.59 times compared with the microhardness of the matrix (69.382 HV); as shown in FIG. 4, the self-etching potential of the deposited layer is-0.287V, 1033mV is forward-shifted relative to the substrate (-1.32V), and the self-etching current density is 1.832 ×10 ^-6 A·cm ^-2 Compared with the substrate (1.669×10) ^-4 A·cm ^-2 ) The corrosion resistance of the deposited layer is obviously improved while the hardness is obviously reduced.

Example 5

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

FIG. 1 (e) shows the metallographic surface morphology of the nano nickel-based cermet composite layer prepared in the embodiment, and the coating is uniform and compact; from the metallographic cross-sectional morphology of FIG. 2 (e), no obvious cracking is seen, the coating is tightly combined with the matrix, and the thickness of the coating is 41.6958 mu m; the hardness test result is shown in fig. 3, wherein the microhardness of the composite layer is 744.9HV, which is 10.74 times higher than that of the matrix (69.382 HV); as shown in FIG. 4, the self-etching potential of the deposited layer is-0.249V, 1071mV higher than that of the substrate (-1.32V), and the self-etching current density is 7.517 ×10 ^-7 A·cm ^-2 Compared with the substrate (1.669×10) ^-4 A·cm ^-2 ) Significantly decline to indicate sinkingThe hardness of the laminated layer is improved, and the corrosion resistance is also improved obviously.

The effect study and comparison are carried out by adopting the technical scheme of the comparison example and the application:

the effect evaluation of the comparative examples is shown in Table 1.

Table 1 evaluation of comparative effect of electrodeposited layer of magnesium alloy

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The above-described embodiments are only preferred embodiments of the invention, and not all embodiments of the invention are possible. Any obvious modifications thereof, which would be apparent to 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 the appended claims.

Claims

1. A method for preparing a magnesium alloy surface variable-frequency power ultrasonic electrodeposition nano nickel-based composite layer is characterized in that a magnesium alloy sample subjected to chemical pre-deposition is adopted as a cathode, a nickel plate with purity of more than 99% is adopted as an anode, the cathode and the anode are respectively connected with a negative electrode and a positive electrode of a pulse power supply, the negative electrode and the positive electrode are immersed in a pre-configured electroplating solution and placed in an ultrasonic generator for electrodeposition, and the ultrasonic generator works in a variable-frequency mode.

2. The method for preparing the variable-frequency power ultrasonic electrodeposition nano nickel-based composite layer on the surface of the magnesium alloy as claimed in claim 1, wherein the preparation method comprises the following specific steps:

(a) Pretreatment: sequentially polishing, degreasing, pickling, surface conditioning and activating the magnesium alloy;

(b) Chemical pre-deposition: carrying out double-layer chemical nickel-phosphorus plating on the magnesium alloy sample after pretreatment;

(c) Preparing electrodeposition liquid according to a main salt formula, wherein the electrodeposition liquid comprises the following components: 110-130 g/L of nickel sulfate, 8-12 g/L of ammonium citrate, 35-50 g/L of ammonium bifluoride, 3g/L of saccharin sodium, 35-45 ml/L of ammonia water, 1-7 g/L of TiN, 0.05-0.25 g/L of GO and 0.1g/L of sodium dodecyl sulfate; adding nickel sulfate into ammonium citrate, sequentially adding ammonium bifluoride, saccharin sodium and ammonia water into the ammonium citrate to form a basic electrodeposition liquid, mixing TiN and GO with sodium dodecyl sulfate by deionized water, performing ultrasonic dispersion, finally mixing with the basic electrodeposition liquid, and simultaneously applying mechanical stirring and ultrasonic waves to fully disperse the electrodeposition liquid for 1h;

3. The method for preparing the variable-frequency power ultrasonic electrodeposited nano nickel-based composite layer on the surface of the magnesium alloy as claimed in claim 1, which is characterized in that the electrodeposition process comprises the following steps: the voltage is 3V, the current density is 1.5-3A cm ^-2 The duty ratio is 35-80%, the magnetic stirring speed is 300r/min, the deposition temperature is 55 ℃, and the deposition time is 75min.

4. The method for preparing the variable-frequency power ultrasonic electrodeposited nano nickel-based composite layer on the surface of the magnesium alloy as claimed in claim 3, wherein the ultrasonic power of the ultrasonic generator is 150-240W, and the ultrasonic frequency is 45KH _Z And 80KH _Z Alternately acting for 10-20 s.

5. The method for preparing the variable-frequency power ultrasonic electrodeposition nano nickel-based composite layer on the surface of the magnesium alloy according to claim 4, wherein the ratio of the cathode area to the anode area is about 2:3, and the distance between two poles is 25mm.