Electroplating method for preparing high-wear-resistance self-lubricating coating

Abstract

The invention relates to the technical field of composite electroplating, in particular to an electroplating method for preparing a high-wear-resistance self-lubricating plating layer, which comprises the following steps: firstly, carrying out pretreatment of oil removal and acid pickling activation on a metal workpiece; then preparing a nano composite nickel plating solution in which a nickel plating basic solution contains a nano particle composite phase subjected to pre-dispersion treatment, and the total concentration of composite particles is 10-60g / L; then the dispersion stability of the nano-composite nickel plating solution is maintained in a circulating filtration and mechanical stirring combined mode, and the pretreated workpiece is electroplated; and finally, after electroplating is completed, the workpiece is cleaned and dried. According to the electroplating process for preparing the nickel-based composite coating with high wear resistance and low friction coefficient, the pulse current is adopted, and the high instantaneous current density and turn-off time of the pulse current are utilized, so that desorption and rearrangement of adsorbed particles are facilitated, uniform embedding of the particles is promoted, nickel matrix crystal grains are refined, and the compactness and comprehensive mechanical properties of the coating are further optimized.

Description

Technical Field

[0001] This invention relates to the field of composite electroplating technology, and more specifically to an electroplating method for preparing a highly wear-resistant, self-lubricating coating. Background Technology

[0002] Nickel plating is widely used as a protective and functional coating due to its excellent mechanical strength and corrosion resistance. However, pure nickel plating has a high coefficient of friction and is prone to wear under dry friction or boundary lubrication conditions, limiting its application in high-speed, high-load moving parts. To improve its wear resistance and friction reduction properties, composite electroplating technology has emerged, which involves dispersing solid particles in a plating bath and embedding them into a nickel matrix through electrodeposition to form a composite coating.

[0003] Currently, this technology faces the following key bottlenecks in practical applications: 1. Particle dispersion problem: Nanoparticles have a large specific surface area and high surface energy, and are very prone to agglomeration and sedimentation in the plating solution, resulting in uneven particle distribution and unstable content in the coating, which seriously affects the performance reproducibility. 2. Limitations of Single Performance: Most studies use a single type of particle, such as hard wear-resistant particles like diamond or soft lubricating particles like PTFE. While the former is wear-resistant, it may exacerbate wear on the workpiece; the latter has good friction-reducing properties but poor load-bearing capacity and insufficient wear resistance. 3. Low co-deposition efficiency: The bonding force between particles and the metal matrix is ​​weak, and co-deposition mainly relies on physical and mechanical interlocking. Under harsh operating conditions, particles are prone to detachment and failure. Traditional particle addition methods are difficult to effectively improve the interfacial bonding strength between particles and the coating. 4. Complex process control: To maintain particle suspension, continuous and strong stirring is required, which can easily lead to air inclusion in the plating solution and the generation of pores. Furthermore, it results in poor uniform co-deposition in deep holes and grooves of complex-shaped workpieces.

[0004] Therefore, developing a composite nickel plating technology that can achieve stable dispersion and synergistic enhancement of nanoparticles and has controllable process is crucial for preparing next-generation high-performance wear-resistant and friction-reducing coatings. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention discloses an electroplating method for preparing a high wear-resistant self-lubricating coating. This electroplating process utilizes the plating solution to prepare a nickel-based composite coating with high wear resistance and low friction coefficient, overcoming the shortcomings of existing composite electroplating technologies such as easy particle agglomeration, single performance, weak bonding force, and unstable process.

[0006] The specific technical solution is as follows: An electroplating method for preparing a highly wear-resistant self-lubricating coating specifically includes the following steps: (1) Pretreatment of metal workpieces by degreasing, pickling and activation; (2) Preparation of nanocomposite nickel plating solution; (3) The dispersion stability of the nano-composite nickel plating solution is maintained by a combination of circulating filtration and mechanical stirring, and the pretreated workpiece is then electroplated. (4) After electroplating, the workpiece is cleaned and dried.

[0007] The electroplating process parameters in step (3) are: pH value 3.8-4.5, temperature 50-60℃, cathode current density 2-8A / dm², pulse power supply, average current density is DC equivalent value, pulse frequency 100-1000Hz, and duty cycle 20-50%.

[0008] The mechanical stirring in step (3) is: using a bottom magnetic stirrer and a propeller-type stirrer installed on the side wall of the plating tank for combined stirring, and controlling the stirring speed to make the plating solution form a gentle vortex but without foaming.

[0009] The electroplating method is used to prepare the coating for use in the manufacture of engine cylinder liners, mold ejector pins, and hydraulic piston rod components.

[0010] The electroplating method for preparing a high wear-resistant self-lubricating coating uses a nano-composite nickel plating solution, which includes a nickel plating base solution containing a pre-dispersed nanoparticle composite phase with a total composite particle concentration of 10-60 g / L. The components and concentrations of the nickel plating base solution are: nickel sulfamate 350-450 g / L, nickel chloride 10-20 g / L, and boric acid 35-45 g / L.

[0011] The pre-dispersion process is as follows: First, nano-molybdenum disulfide and nano-diamond powder are added to an ethanol solution containing surfactant at a mass ratio of 3:1 and mechanically stirred for pre-wetting; then, the resulting mixture is subjected to high-intensity ultrasonic treatment with an ultrasonic power of 800-1200W for 30-60 minutes; KH-550 silane coupling agent is added dropwise to the resulting dispersion and magnetically stirred at a constant temperature of 60-70℃ for 2-4 hours to complete the particle surface modification; the resulting modified particle suspension is centrifuged, the supernatant is removed, and after washing with deionized water, it is redispersed in a small amount of nickel plating base solution to obtain a high-concentration nanoparticle slurry for later use.

[0012] The preparation process of the nanocomposite nickel plating solution is as follows: the nanoparticle slurry is added to the nickel plating base solution under strong mechanical stirring, sodium dodecyl sulfate 0.05-0.2 g / L is added, and stirring is continued to form a uniform suspension.

[0013] The surfactant is PEG-1000.

[0014] Compared with the prior art, the present invention has the following beneficial technical effects: This invention employs a composite reinforcing phase composed of nano-molybdenum disulfide and nanodiamond. Molybdenum disulfide, as a layered solid lubricant, can significantly reduce the coefficient of friction; nanodiamond, as ultra-hard particles, can greatly improve the hardness and resistance to ploughing wear of the coating. The two are compounded in a specific ratio to construct a synergistic reinforcement mechanism of "both soft and hard" in a nickel matrix, achieving a balance between wear resistance and friction reduction.

[0015] This invention proposes an innovative method for particle pre-dispersion and surface modification. Pre-wetting and ultrasonic dispersion: Particles are initially wetted using an ethanol solution containing PEG, followed by high-intensity ultrasonic breaking up of initial agglomerates. Surface chemical modification: A silane coupling agent is introduced, one end of which, after hydrolysis, binds to hydroxyl groups and other functional groups on the particle surface, while the other end's organic functional groups are more compatible with the plating bath environment and can form a stronger interfacial bond with the deposited nickel during electrodeposition. This step is crucial for improving particle co-deposition efficiency and interfacial bonding. Preparation of concentrated slurry: The modified particles are prepared into a concentrated slurry compatible with the basic components of the plating bath, facilitating accurate addition and rapid dispersion. Through the pretreatment of "physical ultrasound + chemical modification," the problems of nanoparticle agglomeration and sedimentation in the plating bath are fundamentally solved, ensuring long-term stability of particle concentration in the plating bath and uniform particle distribution in the coating. The composite addition of molybdenum disulfide and nanodiamond gives the coating both a low coefficient of friction and high hardness, with wear resistance more than 5 times higher than that of pure nickel plating, achieving a synergistic effect. The introduction of silane coupling agents establishes a "chemical bridge" between the particles and the nickel matrix, which greatly improves the interfacial bonding strength, prevents the particles from falling off prematurely during friction, and extends the service life of the coating.

[0016] This invention proposes a specialized composite nickel plating solution, primarily based on a nickel sulfamate system. This solution exhibits low internal stress in the plating layer, allowing for higher particle content and coating thickness, and includes pretreated nanocomposite particles. A combination of mechanical stirring and circulating filtration is employed to achieve uniform suspension throughout the plating solution without introducing air bubbles, thus maintaining dispersion. This invention utilizes the aforementioned composite nickel plating solution to prepare a high-wear-resistant, low-friction coefficient nickel-based composite coating electroplating process. Pulsed current is employed, leveraging its high instantaneous current density and short turn-off time to facilitate the desorption and rearrangement of adsorbed particles, promoting uniform particle embedding and refining the nickel matrix grains, further optimizing the coating's density and overall mechanical properties. Attached Figure Description

[0017] Figure 1 This is a process flow diagram of the electroplating method for preparing a high wear-resistant self-lubricating coating according to the present invention. Detailed Implementation

[0018] The present invention will now be described in detail with reference to specific embodiments and accompanying drawings, but the scope of protection of the present invention is not limited to the specific embodiments and accompanying drawings. Example 1

[0019] Figure 1 The figure shows a process flow diagram of the electroplating method for preparing a high wear-resistant self-lubricating coating according to the present invention. The electroplating method for preparing a high wear-resistant self-lubricating coating according to the present invention specifically includes the following steps: (1) Pretreatment of metal workpieces by degreasing, pickling and activation; (2) Preparation of nanocomposite nickel plating solution; the nanocomposite nickel plating solution includes a nickel plating base solution, which contains a pre-dispersed nanoparticle composite phase, and the total concentration of the composite particles is 40 g / L; The components and concentrations of the nickel plating base solution are as follows: nickel aminosulfonate 400g / L, nickel chloride 15g / L, and boric acid 40g / L.

[0020] The pre-dispersion process is as follows: Weigh 30g of nano-molybdenum disulfide and 10g of nano-diamond, add them to 200mL of ethanol containing 2g of PEG-1000, and mechanically stir for 30 minutes for pre-wetting; then subject the resulting mixture to high-intensity ultrasonic treatment at a power of 1000W for 45 minutes; add 5mL of KH-550 silane coupling agent to the resulting dispersion, and magnetically stir at 65℃ for 3 hours to complete the particle surface modification; centrifuge the resulting modified particle suspension, remove the supernatant, wash with deionized water, and redisperse it in a small amount of nickel plating base solution to obtain a high-concentration nanoparticle slurry for later use.

[0021] The above-mentioned nanoparticle slurry was added to the nickel plating base solution under strong mechanical stirring, and sodium dodecyl sulfate 0.1 g / L was added. The mixture was stirred continuously to form a uniform suspension.

[0022] (3) The dispersion stability of the nano-composite nickel plating solution was maintained by a combination of circulating filtration and mechanical stirring. The pretreated workpiece was then electroplated. The electroplating process parameters were: pH 4.2, temperature 55℃, cathode current density 4A / dm², pulse power supply, average current density equivalent to DC, pulse frequency 500Hz, and duty cycle 30%. Mechanical stirring was performed by a combination of bottom magnetic stirring and a propeller-type stirrer installed on the side wall of the plating tank. The stirring speed was controlled to form a gentle vortex in the plating solution without foaming. Under continuous side wall stirring and circulating filtration, the pretreated 45# steel sample was electroplated for 120 minutes. The resulting coating was uniform, dense, and grayish-black.

[0023] (4) After electroplating, the workpiece is cleaned and dried. Example 2

[0024] The difference from Example 1 is that, In step (2), a nanocomposite nickel plating solution is prepared. The nanocomposite nickel plating solution includes a nickel plating base solution containing a pre-dispersed nanoparticle composite phase with a total concentration of 10 g / L. The components and concentrations of the nickel plating base solution are: nickel aminosulfonate 350 g / L, nickel chloride 10 g / L, and boric acid 35 g / L. The pre-dispersion process is as follows: 30 g of nano molybdenum disulfide and 10 g of nano diamond are weighed and added to 200 mL of ethanol containing 2 g of PEG-1000. The mixture is mechanically stirred for 30 minutes for pre-wetting. Then, the resulting mixture is subjected to high-intensity ultrasonic treatment with an ultrasonic power of 800 W for 30 minutes. KH-550 silane coupling agent is added dropwise to the resulting dispersion and magnetically stirred at 60 °C for 2 hours to complete the particle surface modification. The resulting modified particle suspension is centrifuged to remove the supernatant, washed with deionized water, and then redispersed in a small amount of nickel plating base solution to obtain a high-concentration nanoparticle slurry for later use. The above-mentioned nanoparticle slurry was added to the nickel plating base solution under strong mechanical stirring, and sodium dodecyl sulfate 0.05 g / L was added. The mixture was stirred continuously to form a uniform suspension.

[0025] In step (3), a combination of circulating filtration and mechanical stirring is used to maintain the dispersion stability of the nano-composite nickel plating solution, and the pretreated workpiece is electroplated. The electroplating process parameters are: pH value 3.8, temperature 50℃, cathode current density 2A / dm², pulse power supply, average current density is DC equivalent value, pulse frequency 100Hz, duty cycle 20%. Mechanical stirring is carried out by a combination of bottom magnetic stirring and propeller-type stirring installed on the side wall of the plating tank. The stirring speed is controlled to form a gentle vortex in the plating solution without foaming. Example 3

[0026] The difference from Example 1 is that, In step (2), a nanocomposite nickel plating solution is prepared. The nanocomposite nickel plating solution includes a nickel plating base solution containing a pre-dispersed nanoparticle composite phase with a concentration of 60 g / L. The components and concentrations of the nickel plating base solution are: nickel aminosulfonate 450 g / L, nickel chloride 20 g / L, and boric acid 45 g / L. The pre-dispersion process is as follows: 30 g of nano molybdenum disulfide and 10 g of nano diamond are weighed and added to 200 mL of ethanol containing 2 g of PEG-1000. The mixture is mechanically stirred for 30 minutes for pre-wetting. Then, the resulting mixture is subjected to high-intensity ultrasonic treatment with an ultrasonic power of 1200 W for 60 minutes. KH-550 silane coupling agent is added dropwise to the resulting dispersion and the mixture is magnetically stirred at 70 °C for 4 hours to complete the particle surface modification. The resulting modified particle suspension is centrifuged to remove the supernatant. After washing with deionized water, the mixture is redispersed in a small amount of nickel plating base solution to obtain a high-concentration nanoparticle slurry for later use. The above-mentioned nanoparticle slurry was added to the nickel plating base solution under strong mechanical stirring, and sodium dodecyl sulfate 0.2 g / L was added. The mixture was stirred continuously to form a uniform suspension.

[0027] In step (3), a combination of circulating filtration and mechanical stirring is used to maintain the dispersion stability of the nano-composite nickel plating solution, and the pretreated workpiece is electroplated. The electroplating process parameters are: pH value 4.5, temperature 60℃, cathode current density 8A / dm², pulse power supply, average current density is DC equivalent value, pulse frequency 1000Hz, duty cycle 50%. Mechanical stirring is carried out by a combination of bottom magnetic stirring and propeller-type stirring installed on the side wall of the plating tank. The stirring speed is controlled to form a gentle vortex in the plating solution without foaming.

Claims

1. An electroplating method for preparing a high-wear-resistant self-lubricating coating, characterized in that, Specifically, the steps include the following: (1) Pretreatment of metal workpieces by degreasing, pickling and activation; (2) Preparation of nanocomposite nickel plating solution; (3) The dispersion stability of the nano-composite nickel plating solution is maintained by a combination of circulating filtration and mechanical stirring, and the pretreated workpiece is then electroplated. (4) After electroplating, the workpiece is cleaned and dried.

2. The electroplating method for preparing a high-wear-resistant self-lubricating coating according to claim 1, characterized in that: The electroplating process parameters in step (3) are: pH value 3.8-4.5, temperature 50-60℃, cathode current density 2-8A / dm², pulse power supply, average current density is DC equivalent value, pulse frequency 100-1000Hz, and duty cycle 20-50%.

3. The electroplating method for preparing a high-wear-resistant self-lubricating coating according to claim 1, characterized in that: The mechanical stirring in step (3) is: using a bottom magnetic stirrer and a propeller-type stirrer installed on the side wall of the plating tank for combined stirring, and controlling the stirring speed to make the plating solution form a gentle vortex but without foaming.

4. The electroplating method for preparing a high-wear-resistant self-lubricating coating according to claim 1, characterized in that: The electroplating method is used to prepare the coating for use in the manufacture of engine cylinder liners, mold ejector pins, and hydraulic piston rod components.

5. The nano-composite nickel plating solution used in the electroplating method for preparing a high-wear-resistant self-lubricating coating according to claim 1, characterized in that, The nickel plating base solution contains a pre-dispersed nanoparticle composite phase with a total concentration of 10-60 g / L. The components and concentrations of the nickel plating base solution are: nickel sulfamate 350-450 g / L, nickel chloride 10-20 g / L, and boric acid 35-45 g / L.

6. The nanocomposite nickel plating solution used in the electroplating method for preparing a high wear-resistant self-lubricating coating according to claim 5, characterized in that: The pre-dispersion process is as follows: First, nano-molybdenum disulfide and nano-diamond powder are added to an ethanol solution containing surfactant at a mass ratio of 3:1, and then mechanically stirred to pre-wet them. The resulting mixture was then subjected to high-intensity ultrasonic treatment at a power of 800-1200W for 30-60 minutes. KH-550 silane coupling agent was added dropwise to the resulting dispersion, and the mixture was magnetically stirred at a constant temperature of 60-70℃ for 2-4 hours to complete the surface modification of the particles. The resulting modified particle suspension was centrifuged to remove the supernatant, washed with deionized water, and then redispersed in a small amount of nickel plating base solution to obtain a high-concentration nanoparticle slurry for later use.

7. The nanocomposite nickel plating solution used in the electroplating method for preparing a high wear-resistant self-lubricating coating according to claim 5, characterized in that: The preparation process of the nanocomposite nickel plating solution is as follows: the nanoparticle slurry is added to the nickel plating base solution under strong mechanical stirring, sodium dodecyl sulfate 0.05-0.2 g / L is added, and stirring is continued to form a uniform suspension.

8. The nanocomposite nickel plating solution used in the electroplating method for preparing a high wear-resistant self-lubricating coating according to claim 6, characterized in that: The surfactant is PEG-1000.

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