Pulse-direct current electrochemical composite deposition process for nickel-tungsten-phosphorus alloy coating

Abstract

The invention provides a pulse-direct current electrochemistry composite deposition process of a nickel-tungsten-phosphorus alloy coating, and belongs to the technical field of coating preparation, and the pulse-direct current electrochemistry composite deposition process comprises the following steps: carrying out silane coupling agent modification treatment on alpha-aluminum oxide; carrying out modification treatment on the hexagonal boron nitride nanosheet by adopting hexadecyl trimethyl ammonium bromide; carrying out polyacrylic acid modification treatment on the nano silicon dioxide; nickel salt, tungsten salt, phosphorus salt, a complexing agent, a buffering agent, a primary brightener, a secondary brightener, a wetting agent, modified aluminum oxide, modified boron nitride, modified silicon dioxide and deionized water are mixed, stirred and heated, and a composite plating solution is obtained; the substrate serves as a cathode, pulse current is applied to the substrate for pulse electroplating, then the current density of the pulse current is continuously and linearly reduced to a target value, and finally direct current electroplating is conducted under the target value; by optimizing the formula of the composite plating solution and the pulse-direct current composite electroplating process, the nickel-tungsten-phosphorus alloy composite plating layer with high hardness, low friction, high wear resistance and corrosion resistance is finally obtained.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of plating layer preparation, and relates to a pulse-direct current electrochemical composite deposition process for a nickel tungsten phosphorus alloy plating layer. BACKGROUND

[0002] In the field of electroplating technology, nickel-based alloy plating layers, especially nickel tungsten phosphorus alloy, are widely used for surface strengthening and protection of mechanical parts, molds and precision devices due to their excellent hardness, wear resistance and corrosion resistance. Traditional nickel tungsten phosphorus alloy electroplating processes mostly use single direct current or pulse power mode. Direct current electroplating process is simple and has high deposition rate, but the obtained plating layer has relatively large internal stress, general compactness, and is prone to dendrite or "burning" phenomenon in the high current density area, which affects the quality of the plating layer. Pulse electroplating helps to reduce concentration polarization through periodic current on-off, making the plating layer crystallize more finely and improving the physical properties of the plating layer to some extent. However, the single pulse electroplating mode still has insufficient ability to control the composition and structure of the plating layer when preparing thick plating layer, and it is difficult to realize the gradient design of the plating layer performance in the thickness direction. SUMMARY

[0003] In view of the deficiencies of the prior art, the purpose of the present application is to provide a pulse-direct current electrochemical composite deposition process for a nickel tungsten phosphorus alloy plating layer, which obtains a nickel tungsten phosphorus alloy composite plating layer with high hardness, low friction, high wear resistance and corrosion resistance by optimizing the component ratio of the composite plating solution and combining it with the pulse-direct current electrochemical composite deposition process.

[0004] To achieve this purpose, the present application adopts the following technical solutions:

[0005] In the first aspect, the present application provides a pulse-direct current electrochemical composite deposition process for a nickel tungsten phosphorus alloy plating layer, which comprises:

[0006] (I) modifying alpha-alumina with silane coupling agent to obtain modified alumina; modifying hexagonal boron nitride nanosheet with cetyltrimethylammonium bromide to obtain modified boron nitride; modifying nanosilica with polyacrylic acid to obtain modified silica;

[0007] (II) mixing and stirring nickel salt, tungsten salt, phosphorus salt, complexing agent, buffer, primary brightener, secondary brightener, wetting agent, the modified alumina, the modified boron nitride, the modified silica and deionized water to obtain a composite plating solution;

[0008] (III) immersing the substrate as a cathode and an anode plate into the composite plating solution, applying pulse current to the substrate for pulse electroplating, then continuously linearly reducing the current density of the pulse current to a target value, and finally performing direct current electroplating at the target value.

[0009] The present application improves the dispersion stability of the nanoparticles in the composite plating solution and the interface bonding performance between the plating layer matrix and the nanoparticles by surface modification of the alumina, boron nitride and silica nanoparticles with silane coupling agent, cetyltrimethylammonium bromide and polyacrylic acid, respectively. By optimizing the component ratio of the composite plating solution and combining with the pulse-direct current electrochemical composite deposition process, a gradient plating layer structure from the dense fine-grained bottom layer (formed in the pulse plating stage) to the low-stress main layer (formed in the direct current plating stage) is finally formed, and a nickel tungsten phosphorus alloy composite plating layer with high hardness, low friction, high wear resistance and corrosion resistance is obtained.

[0010] In the material pretreatment stage, the dispersion stability of the nanoparticles in the composite plating solution and the interface bonding performance between the plating layer matrix and the nanoparticles are significantly improved by surface modification of the three different types of nanoparticles. After modification of the α-alumina with silane coupling agent, organic functional groups are introduced to the surface, which enhances the affinity with metal ions and improves the suspension stability in the composite plating solution, avoiding sedimentation. After modification of the hexagonal boron nitride nanoplatelets with cetyltrimethylammonium bromide, the layered structure is more easily exfoliated and uniformly dispersed, which not only improves the thermal conductivity and friction reduction performance of the plating layer, but also reduces the agglomeration phenomenon through the adsorption effect of the surfactant. After modification of the nanosilica with polyacrylic acid, the surface is negatively charged, which can be stably dispersed in the composite plating solution through electrostatic repulsion, and its high specific surface area can adsorb metal ions to promote nucleation of the plating layer.

[0011] In the pulse-direct current electrochemical composite deposition process, the three types of surface-modified nanoparticles improve the comprehensive performance of the nickel tungsten phosphorus alloy plating layer through their unique physical and chemical properties and synergistic effect. Modified alumina has high hardness and good thermal stability, and it is uniformly dispersed in the plating layer as a hard reinforcing phase, which can effectively hinder dislocation movement through physical dispersion strengthening, thereby improving the macro hardness and plastic deformation resistance of the plating layer. Modified boron nitride has a layered structure and excellent lubricity, which mainly plays a role in reducing friction and wear in the plating layer. Its sheet structure can form a lubricating transfer film on the contact surface during friction, significantly reducing the friction coefficient and volume wear of the plating layer, and its high thermal conductivity helps to quickly dissipate friction heat, avoiding local overheating that causes the plating layer to soften or fail. Modified silica has a large specific surface area and surface activity, which preferentially adsorbs metal ions and becomes a heterogeneous nucleation core during deposition, which can refine the plating layer grains and increase the grain boundary density, not only further improving the hardness of the plating layer, but also the dense microstructure significantly blocks the penetration path of the corrosion medium, enhancing the corrosion resistance of the plating layer. Through the combined action of modified alumina, modified boron nitride and modified silica, the final nickel tungsten phosphorus alloy plating layer has high hardness, low friction coefficient, excellent wear resistance and good corrosion resistance.

[0012] In the composite plating bath, nickel, tungsten, and phosphate salts serve as metal sources, forming stable complexes under the action of a complexing agent. This slows down the deposition rate, preventing roughness and dendrite growth in the coating caused by rapid deposition. The addition of a buffer maintains a stable pH value in the composite plating bath, ensuring the co-deposition efficiency of tungsten and phosphorus. The combined use of primary and secondary brighteners further refines the coating grains, improving surface smoothness and gloss. The wetting agent reduces the surface tension of the composite plating bath, improving the wettability of the substrate surface and reducing the generation of pinholes and defects in the coating.

[0013] This invention employs a pulse-DC electrochemical composite deposition process in the electrodeposition stage. The initial stage uses pulsed electroplating, utilizing the intermittent switching of the pulsed current to effectively reduce concentration polarization, resulting in a uniform distribution of metal ions on the cathode surface. This not only promotes the uniform deposition of nickel, tungsten, and phosphorus metal ions but also facilitates the adsorption and embedding of modified alumina, modified boron nitride, and modified silica on the cathode surface. Positively charged modified alumina migrates more easily to the cathode under the influence of the electric field and is captured and coated by the rapidly growing substrate, its high hardness providing a supporting framework for the coating. The sheet-like modified boron nitride, with its two-dimensional structure, arranges parallel to the substrate surface under the impact of the pulsed current, which is beneficial for its friction-reducing advantages. Negatively charged modified silica adsorbs metal ions through the electric field, serving as heterogeneous nucleation sites to refine the initial grains and promote the formation of a fine-grained, dense underlying coating.

[0014] After pulse electroplating, the pulse current density is continuously and linearly reduced to the target value, while the duty cycle is gradually increased to 100%, achieving a smooth transition from pulse electroplating to DC electroplating. This process avoids stress concentration and interface defects in the coating caused by sudden current changes, reducing the risk of coating peeling. Simultaneously, during the transition from pulse to DC electroplating, as the current density decreases, the metal deposition rate slows down, allowing modified alumina, modified boron nitride, and modified silica more time to embed into the coating through electrophoretic migration and adsorption. The final DC electroplating is performed at a low current density, primarily to achieve coating thickness increase and structural relaxation. During this process, modified alumina maintains the overall hardness of the coating, modified boron nitride reduces internal shear stress, and modified silica fills the micropores within the coating, ultimately forming a nickel-tungsten-phosphorus alloy coating with high hardness, high wear resistance, and high corrosion resistance in the DC electroplating stage.

[0015] As a preferred technical solution of the present invention, in step (I), the modified alumina is specifically prepared by the following method:

[0016] α-alumina was dispersed in a silane coupling agent solution and ultrasonically dispersed under water bath heating conditions. Then, it was filtered. The filter cake obtained by filtration was washed and dried to obtain the modified alumina.

[0017] This invention modifies the surface of α-alumina particles using a silane coupling agent, significantly improving the dispersion stability of alumina in the composite plating bath and its bonding performance with the coating substrate. The alkoxy groups in the silane coupling agent molecule first hydrolyze to generate silanol groups. These silanol groups undergo a dehydration condensation reaction with the hydroxyl groups on the surface of α-alumina, forming a strong Si-O-Al covalent bond. Simultaneously, the organic functional groups (such as amino and epoxy groups) at the other end of the silane molecule extend outward, enhancing compatibility with the composite plating bath, effectively reducing the surface energy of the alumina particles, and minimizing agglomeration caused by van der Waals forces. This allows the particles to maintain stable dispersion in the composite plating bath through electrostatic repulsion and steric hindrance.

[0018] In the electrochemical composite deposition process, the main role of modified alumina is:

[0019] On the one hand, the modified alumina nanoparticles are uniformly dispersed in the coating to form a hard reinforcing phase, which hinders dislocation movement. When dislocations encounter the non-deformable modified alumina particles, they can only bypass the particles and form dislocation loops, thereby increasing the resistance to subsequent dislocation movement and significantly improving the microhardness, resistance to plastic deformation and wear resistance of the coating.

[0020] On the other hand, after the alumina nanoparticles are modified with silane coupling agents, organic functional groups are introduced on their surface. These organic functional groups can adsorb or coordinate with metal ions such as nickel ions and tungsten ions in the composite plating solution. This interaction makes the surface of the modified alumina particles a metal ion enrichment area, effectively reducing the nucleation barrier required for metal deposition. When electrochemical deposition begins, metal ions preferentially reduce and deposit on the modified alumina surface to form stable crystal nuclei, rather than spontaneously nucleating on the substrate surface, which is conducive to the formation of finer and more uniform grains.

[0021] As a preferred technical solution of the present invention, the average particle size of the α-alumina is 50~100nm, for example, it can be 50nm, 55nm, 60nm, 65nm, 70nm, 75nm, 80nm, 85nm, 90nm, 95nm or 100nm, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0022] In some alternative examples, the silane coupling agent solution consists of a silane coupling agent and an aqueous ethanol solution.

[0023] In some optional examples, the mass fraction of the silane coupling agent in the silane coupling agent solution is 1 to 2 wt%, for example, it may be 1.0 wt%, 1.1 wt%, 1.2 wt%, 1.3 wt%, 1.4 wt%, 1.5 wt%, 1.6 wt%, 1.7 wt%, 1.8 wt%, 1.9 wt%, or 2.0 wt%, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0024] In some optional instances, the water bath heating temperature is 50~60°C, for example, it can be 50°C, 51°C, 52°C, 53°C, 54°C, 55°C, 56°C, 57°C, 58°C, 59°C or 60°C, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0025] In some optional instances, the ultrasonic power of the ultrasonic dispersion is 400-500W, for example, it can be 400W, 410W, 420W, 430W, 440W, 450W, 460W, 470W, 480W, 490W or 500W, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0026] In some optional instances, the ultrasonic dispersion time is 30 to 50 minutes, for example, 30 minutes, 32 minutes, 34 minutes, 35 minutes, 36 minutes, 38 minutes, 40 minutes, 42 minutes, 44 minutes, 46 minutes, 48 ​​minutes or 50 minutes, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0027] In the process of preparing modified alumina, the drying temperature can be selected from 80 to 90℃, for example, 80℃, 81℃, 82℃, 83℃, 84℃, 85℃, 86℃, 87℃, 88℃, 89℃ or 90℃; the drying time can be selected from 3 to 4 hours, for example, 3.0 hours, 3.1 hours, 3.2 hours, 3.3 hours, 3.4 hours, 3.5 hours, 3.6 hours, 3.7 hours, 3.8 hours, 3.9 hours or 4.0 hours, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0028] As a preferred technical solution of the present invention, in step (I), the modified boron nitride is specifically prepared by the following method:

[0029] Hexagonal boron nitride was dispersed in an aqueous solution of hexadecyltrimethylammonium bromide, and the mixture was simultaneously stirred, heated, and sonicated. Subsequently, the mixture was centrifuged, and the precipitate was washed and dried to obtain the modified boron nitride.

[0030] This invention employs hexadecyltrimethylammonium bromide (CTAB) to surface modify hexagonal boron nitride, thereby significantly improving its dispersibility in composite plating solutions and its interfacial bonding ability with the plating substrate. As a cationic surfactant, CTAB's hydrophilic quaternary ammonium groups adsorb onto the surface of boron nitride sheets via electrostatic interactions, while its hydrophobic long-chain alkyl groups extend outwards to form a steric hindrance layer. CTAB modification not only effectively neutralizes some of the surface charge of boron nitride and reduces van der Waals forces between sheets, but more importantly, through the hydrophobicity and steric hindrance of the alkyl chains, it prevents the recombination and aggregation of boron nitride nanosheets, enabling them to be stably dispersed in the composite plating solution.

[0031] In the electrochemical composite deposition process, the main role of modified boron nitride is:

[0032] On the one hand, modified boron nitride, due to the directional arrangement of CTAB molecules on its surface, is more likely to be arranged in a direction parallel to the substrate under the action of an electric field. This arrangement can maximize the lubrication advantage of modified boron nitride. When the coating is subjected to friction, these parallel-arranged layers can effectively form a continuous lubrication network at the contact interface. When the coating is subjected to friction, the weak van der Waals forces between the boron nitride layers allow the layers to slip relative to each other, thereby forming a lubrication transfer film at the friction interface, effectively reducing the coefficient of friction and wear rate.

[0033] On the other hand, hexagonal boron nitride has excellent thermal conductivity. When modified boron nitride is embedded in the coating, its layered structure can build an efficient heat conduction path, quickly dissipating the heat generated by local frictional heat and electrochemical reaction, thus avoiding coating softening or failure due to heat accumulation.

[0034] As a preferred embodiment of the present invention, the mass fraction of hexadecyltrimethylammonium bromide in the aqueous solution is 0.5~1wt%, for example, it can be 0.5wt%, 0.55wt%, 0.6wt%, 0.65wt%, 0.7wt%, 0.75wt%, 0.8wt%, 0.85wt%, 0.9wt%, 0.95wt%, or 1.0wt%, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0035] In some optional instances, the mass ratio of the hexagonal boron nitride to the hexadecyltrimethylammonium bromide in the aqueous solution is 1:(13~15), for example, it can be 1:13, 1:13.2, 1:13.4, 1:13.6, 1:13.8, 1:14, 1:14.2, 1:14.4, 1:14.6, 1:14.8 or 1:15, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0036] In some optional instances, the stirring speed is 300 to 500 rpm, for example, 300 rpm, 320 rpm, 340 rpm, 360 rpm, 380 rpm, 400 rpm, 420 rpm, 440 rpm, 460 rpm, 480 rpm or 500 rpm, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0037] In some optional instances, the heating temperature is 60~70°C, for example, it can be 60°C, 61°C, 62°C, 63°C, 64°C, 65°C, 66°C, 67°C, 68°C, 69°C or 70°C, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0038] In some optional instances, the ultrasonic power of the ultrasound is 400 to 500 W, for example, 400 W, 410 W, 420 W, 430 W, 440 W, 450 W, 460 W, 470 W, 480 W, 490 W or 500 W, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0039] In some optional instances, the stirring, heating, and ultrasonic treatment time is 3 to 4 hours, for example, 3.0 hours, 3.1 hours, 3.2 hours, 3.3 hours, 3.4 hours, 3.5 hours, 3.6 hours, 3.7 hours, 3.8 hours, 3.9 hours, or 4.0 hours, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0040] In the preparation of modified boron nitride, the centrifugal speed can be selected from 8000 to 10000 rpm, for example, 8000 rpm, 8200 rpm, 8400 rpm, 8600 rpm, 8800 rpm, 9000 rpm, 9200 rpm, 9400 rpm, 9600 rpm, 9800 rpm, or 10000 rpm; the centrifugal time can be selected from 10 to 15 min, for example, 10 min, 10.5 min, 11 min, 11.5 min, 12 min, 12.5 min, or 13 min. The drying time can be 13.5 min, 14 min, 14.5 min, or 15 min; the drying temperature can be selected from 80 to 90℃, for example, 80℃, 81℃, 82℃, 83℃, 84℃, 85℃, 86℃, 87℃, 88℃, 89℃, or 90℃; the drying time can be selected from 3 to 4 hours, for example, 3.0h, 3.1h, 3.2h, 3.3h, 3.4h, 3.5h, 3.6h, 3.7h, 3.8h, 3.9h, or 4.0h, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0041] As a preferred technical solution of the present invention, in step (I), the modified silica is specifically prepared by the following method:

[0042] Nano-silica was dispersed in an aqueous solution of polyacrylic acid, and then subjected to heating and ultrasonic treatment. The mixture was then filtered, and the resulting filter cake was washed and dried to obtain the modified silica.

[0043] This invention utilizes polyacrylic acid to modify the surface of silica, thereby significantly improving its dispersion stability in composite plating solutions and the interfacial bonding strength with the plating substrate. As an anionic polymer, the carboxyl groups on polyacrylic acid's molecular chains can be adsorbed onto the silica surface via hydrogen bonding and electrostatic interactions. Simultaneously, its polymer segments extending into the solution prevent silica particles from approaching each other and agglomerating through steric hindrance. The polyacrylic acid adsorption layer formed on the silica surface not only imparts stronger hydrophilicity and surface negative charge to the silica particles but also, through electrostatic repulsion and steric hindrance, enables the silica particles to maintain uniform dispersion in the composite plating solution over a long period.

[0044] In the electrochemical composite deposition process, the main role of modified silica is reflected in:

[0045] On the one hand, after being modified with polyacrylic acid, silica nanoparticles are rich in carboxyl functional groups on their surface. These functional groups can combine with metal ions such as nickel and tungsten ions in the composite plating solution through coordination and electrostatic adsorption, making the surface of silica particles a metal ion enrichment area. This effectively reduces the nucleation energy barrier required for metal deposition, allowing metal ions to preferentially reduce on the surface of silica particles and form stable crystal nuclei. This heterogeneous nucleation method greatly increases the density of nucleation points, thereby promoting grain refinement and improving the density and uniformity of the coating.

[0046] Secondly, after the modified silica is coated by the continuously deposited coating substrate, it can fill the micropores and defects formed during the coating growth process, improve the density and continuity of the coating, block the penetration path of corrosive media, and enhance the corrosion resistance of the coating. In addition, the pore-filling effect of modified silica not only blocks the penetration path of corrosive media, but also enhances the mechanical integrity of the coating by reducing stress concentration points.

[0047] Thirdly, the modification of polyacrylic acid also improves the interfacial bonding strength between silica and the coating substrate. The flexible interfacial layer formed by the polyacrylic acid molecular chains on the surface of silica particles can buffer stress changes during the deposition process and suppress the occurrence of microcracks caused by the difference in thermal expansion coefficients between silica particles and the coating substrate.

[0048] As a preferred technical solution of the present invention, the average particle size of the nano-silica is 30~50nm, for example, it can be 30nm, 32nm, 34nm, 36nm, 38nm, 40nm, 42nm, 44nm, 46nm, 48nm or 50nm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0049] In some alternative examples, the concentration of polyacrylic acid in the aqueous polyacrylic acid solution is 1 to 2 g / L, for example, it can be 1.0 g / L, 1.1 g / L, 1.2 g / L, 1.3 g / L, 1.4 g / L, 1.5 g / L, 1.6 g / L, 1.7 g / L, 1.8 g / L, 1.9 g / L or 2.0 g / L, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0050] In some alternative examples, the mass ratio of the nano-silica to the polyacrylic acid in the aqueous polyacrylic acid solution is 1:(1~2), for example, it can be 1:1.0, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9 or 1:2.0, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0051] In some optional instances, the heating temperature is 40 to 50°C, for example, 40°C, 41°C, 42°C, 43°C, 44°C, 45°C, 46°C, 47°C, 48°C, 49°C or 50°C, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0052] In some optional instances, the ultrasonic power of the ultrasonic treatment is 300 to 400 W, for example, 300 W, 310 W, 320 W, 330 W, 340 W, 350 W, 360 W, 370 W, 380 W, 390 W or 400 W, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0053] In some optional instances, the heating and ultrasonic treatment time is 1 to 2 hours, for example, 1.0h, 1.1h, 1.2h, 1.3h, 1.4h, 1.5h, 1.6h, 1.7h, 1.8h, 1.9h or 2.0h, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0054] In the process of preparing modified silica, the drying temperature can be selected from 60 to 80℃, for example, 60℃, 62℃, 64℃, 66℃, 68℃, 70℃, 72℃, 74℃, 76℃, 78℃ or 80℃; the drying time can be selected from 2 to 3 hours, for example, 2.0 hours, 2.1 hours, 2.2 hours, 2.3 hours, 2.4 hours, 2.5 hours, 2.6 hours, 2.7 hours, 2.8 hours, 2.9 hours or 3.0 hours, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0055] As a preferred technical solution of the present invention, in step (II), the composite plating solution is prepared by the following method:

[0056] Nickel salt, tungsten salt, complexing agent, and buffer are added sequentially to deionized water. Each component is stirred until completely dissolved before adding the next component. Alkali solution is added to the resulting mixed solution to adjust its pH to 7-8, followed by the addition of phosphate salt, and the mixture is stirred until completely dissolved. The primary brightener, secondary brightener, wetting agent, modified alumina, modified boron nitride, and modified silicon dioxide are then added, while the mixture is stirred, heated, and ultrasonically treated to obtain the composite plating solution.

[0057] Nickel ions and tungstate ions migrate to the cathode interface under the influence of an electric field, where nickel ions are directly reduced to metallic nickel (Ni). 2+ +2e -→Ni), while tungsten deposition requires induced co-deposition, meaning tungsten cannot be electrodeposited alone from aqueous solution; it needs to be reduced together with metals such as nickel and iron. During the deposition process, tungstate ions are first adsorbed at the cathode interface and reduced to metallic tungsten (WO4) under the catalysis of nickel atoms. 2- +4H2O+6e - →W+8OH - Sodium hypophosphite undergoes a reduction reaction on the deposited nickel surface to generate phosphorus atoms (H2PO2). - +e - →P+2OH - These phosphorus atoms combine with nickel and tungsten to form amorphous or microcrystalline Ni-WP alloy coatings.

[0058] Co-deposition is achieved through the regulation of a citric acid complexing agent. This agent forms stable complexes with nickel and tungsten ions, slowing down the reduction rate of the metal ions and bringing the deposition potentials closer together, thereby promoting the simultaneous precipitation of nickel, tungsten, and phosphorus. Sodium acetate acts as a buffer to maintain the pH stability of the composite plating bath, ensuring the smooth progress of the complexation system and the reduction reaction.

[0059] The deposition of modified alumina, modified boron nitride, and modified silica is achieved through electrophoretic migration and adsorption. Under the action of an electric field, the modified alumina, modified boron nitride, and modified silica migrate toward the cathode and are captured and coated by the continuously deposited coating substrate, eventually being uniformly dispersed in the coating, playing a role in dispersion strengthening, lubrication and friction reduction, and grain refinement strengthening.

[0060] The high current density in the pulse phase promotes fine grain nucleation and the embedding of modified nanoparticles, while the low current density in the DC phase enables low-stress thick-layer growth, ultimately forming a nickel-tungsten-phosphorus alloy coating with uniform composition and dense structure.

[0061] In some optional instances, the stirring speed is 300 to 400 rpm, for example, 300 rpm, 310 rpm, 320 rpm, 330 rpm, 340 rpm, 350 rpm, 360 rpm, 370 rpm, 380 rpm, 390 rpm or 400 rpm, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0062] In some optional instances, the heating temperature is 45~55°C, for example, it can be 45°C, 46°C, 47°C, 48°C, 49°C, 50°C, 51°C, 52°C, 53°C, 54°C or 55°C, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0063] In some optional instances, the ultrasonic power of the ultrasound is 400 to 500 W, for example, 400 W, 410 W, 420 W, 430 W, 440 W, 450 W, 460 W, 470 W, 480 W, 490 W or 500 W, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0064] In some optional instances, the stirring, heating, and ultrasonic treatment time is 1 to 2 hours, for example, 1.0 hours, 1.1 hours, 1.2 hours, 1.3 hours, 1.4 hours, 1.5 hours, 1.6 hours, 1.7 hours, 1.8 hours, 1.9 hours, or 2.0 hours, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0065] As a preferred technical solution of the present invention, in step (II), the concentration of the nickel salt in the composite plating solution is 20~30g / L, for example, it can be 20g / L, 21g / L, 22g / L, 23g / L, 24g / L, 25g / L, 26g / L, 27g / L, 28g / L, 29g / L or 30g / L, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0066] In some optional examples, the concentration of the tungsten salt in the composite plating solution is 50-60 g / L, for example, it can be 50 g / L, 51 g / L, 52 g / L, 53 g / L, 54 g / L, 55 g / L, 56 g / L, 57 g / L, 58 g / L, 59 g / L or 60 g / L, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0067] In some optional examples, the concentration of the phosphate salt in the composite plating solution is 15-25 g / L, for example, it can be 15 g / L, 16 g / L, 17 g / L, 18 g / L, 19 g / L, 20 g / L, 21 g / L, 22 g / L, 23 g / L, 24 g / L or 25 g / L, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0068] In some optional examples, the concentration of the complexing agent in the composite plating solution is 80-100 g / L, for example, it can be 80 g / L, 82 g / L, 84 g / L, 86 g / L, 88 g / L, 90 g / L, 92 g / L, 94 g / L, 96 g / L, 98 g / L or 100 g / L, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0069] In some optional examples, the concentration of the buffer in the composite plating solution is 10-20 g / L, for example, it can be 10 g / L, 11 g / L, 12 g / L, 13 g / L, 14 g / L, 15 g / L, 16 g / L, 17 g / L, 18 g / L, 19 g / L or 20 g / L, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0070] In some alternative examples, the concentration of the primary brightener in the composite plating solution is 1 to 3 g / L, for example, it can be 1.0 g / L, 1.2 g / L, 1.4 g / L, 1.6 g / L, 1.8 g / L, 2.0 g / L, 2.2 g / L, 2.4 g / L, 2.6 g / L, 2.8 g / L or 3.0 g / L, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0071] In some alternative examples, the concentration of the secondary brightener in the composite plating solution is 0.1 to 0.5 g / L, for example, it can be 0.1 g / L, 0.15 g / L, 0.2 g / L, 0.25 g / L, 0.3 g / L, 0.35 g / L, 0.4 g / L, 0.45 g / L or 0.5 g / L, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0072] In some alternative examples, the concentration of the wetting agent in the composite plating solution is 0.1~0.2 g / L, for example, it can be 0.1 g / L, 0.11 g / L, 0.12 g / L, 0.13 g / L, 0.14 g / L, 0.15 g / L, 0.16 g / L, 0.17 g / L, 0.18 g / L, 0.19 g / L or 0.2 g / L, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0073] It should be noted that the present invention does not impose special requirements or specific limitations on nickel salts, tungsten salts, phosphate salts, complexing agents, buffers, primary brighteners, secondary brighteners, and wetting agents. For example, nickel salts can be nickel sulfate, tungsten salts can be sodium tungstate, phosphate salts can be sodium hypophosphite, complexing agents can be citric acid, buffers can be sodium acetate, primary brighteners can be sodium saccharin, secondary brighteners can be 1,4-butynediol, and wetting agents can be sodium dodecyl sulfate.

[0074] It is understood that the above are merely optional specific materials provided to ensure the integrity of the technical solution, and do not constitute a further limitation on the claims of this invention. The scope of protection of this invention shall still be determined by the claims. If those skilled in the art replace the above optional specific materials with other materials, they shall also fall within the scope of protection of this invention.

[0075] In some alternative examples, the concentration of the modified alumina in the composite plating solution is 4 to 5 g / L, for example, 4.0 g / L, 4.1 g / L, 4.2 g / L, 4.3 g / L, 4.4 g / L, 4.5 g / L, 4.6 g / L, 4.7 g / L, 4.8 g / L, 4.9 g / L or 5.0 g / L, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0076] This invention specifically limits the concentration of modified alumina to 4-5 g / L. The alumina nanoparticles modified with the silane coupling agent can fully utilize their surface-active groups to adsorb metal ions in the composite plating solution. Under the action of a pulsed electric field, they effectively migrate to the cathode surface and are uniformly coated by the deposited plating substrate. When the concentration of modified alumina is within the range specified in this invention, it ensures that the modified alumina particles are uniformly distributed in the plating layer, effectively hindering dislocation movement and significantly improving the microhardness and resistance to plastic deformation of the plating layer. Simultaneously, it avoids excessively high viscosity of the composite plating solution and particle agglomeration caused by excessive modified alumina particles.

[0077] When the concentration of modified alumina is below 4 g / L, there are insufficient modified alumina particles in the composite plating solution, making it difficult to form a continuous and effective dispersed strengthening network within the coating. Consequently, the hardness and wear resistance of the coating cannot be fully improved. Furthermore, the insufficient number of modified alumina particles reduces the number of sites available for heterogeneous nucleation, resulting in a coarser coating structure and an increase in crystal defects. This not only reduces the mechanical properties of the coating but also affects its corrosion resistance due to the higher porosity.

[0078] When the concentration of modified alumina exceeds 5 g / L, high concentrations of modified alumina are prone to agglomeration, forming large agglomerates. These agglomerates become stress concentration points in the coating, thus reducing the mechanical properties of the coating. Furthermore, excessive modified alumina significantly increases the viscosity of the composite plating solution, hindering the migration and deposition of metal ions. This results in uneven deposition rates of metal ions on the substrate surface, ultimately leading to a rough coating surface or even nodule formation.

[0079] In some alternative examples, the concentration of the modified boron nitride in the composite plating solution is 1 to 3 g / L, for example, it can be 1.0 g / L, 1.2 g / L, 1.4 g / L, 1.6 g / L, 1.8 g / L, 2.0 g / L, 2.2 g / L, 2.4 g / L, 2.6 g / L, 2.8 g / L or 3.0 g / L, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0080] This invention specifically limits the concentration of modified boron nitride to 1-3 g / L. The CTAB-modified hexagonal boron nitride nanosheets can be stably dispersed in the composite plating solution using the steric hindrance of CTAB. During pulse-DC composite electrodeposition, these sheet-like boron nitride nanosheets align and embed into the plating substrate under the influence of an electric field, forming a layered structure parallel to the substrate surface. This orientation distribution not only effectively reduces the coefficient of friction of the plating layer through its own lubrication properties but also forms a continuous lubrication transfer film at the contact interface during friction, significantly improving the lubrication and friction-reducing performance of the plating layer. When the concentration of modified boron nitride is within the range specified in this invention, it ensures a sufficient amount of modified boron nitride to form a complete lubrication transfer film, thereby achieving the ideal lubrication and friction-reducing effect, while avoiding the dispersion stability problem of the composite plating solution caused by excessive modified boron nitride.

[0081] When the concentration of modified boron nitride is below 1 g / L, the amount of modified boron nitride is insufficient, making it difficult to form a continuous and effective lubrication network in the coating, thus significantly reducing the friction reduction and anti-wear effect. In addition, excessively low concentrations of modified boron nitride have limited effect on improving the thermal conductivity of the coating, and are prone to generating frictional heat during friction, accelerating the wear of the coating.

[0082] When the concentration of modified boron nitride exceeds 3 g / L, high concentrations of modified boron nitride are more prone to agglomeration and stacking, disrupting its distribution parallel to the substrate surface and negatively impacting its lubrication effect. Furthermore, excessive modified boron nitride increases the viscosity of the composite plating solution, affecting the electrodeposition process of metal ions and leading to increased surface roughness of the coating. Simultaneously, excessive modified boron nitride hinders the continuous growth of the coating substrate, generating microscopic defects at the interface between the modified boron nitride and the coating substrate, thus reducing the mechanical properties of the coating.

[0083] In some alternative examples, the concentration of the modified silica in the composite plating solution is 3 to 4 g / L, for example, it can be 3.0 g / L, 3.1 g / L, 3.2 g / L, 3.3 g / L, 3.4 g / L, 3.5 g / L, 3.6 g / L, 3.7 g / L, 3.8 g / L, 3.9 g / L or 4.0 g / L, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0084] This invention specifically limits the concentration of modified silica to 3-4 g / L. The polyacrylic acid-modified nano-silica particles can be stably dispersed in the composite plating bath by utilizing the electronegativity and steric hindrance of their surface carboxyl groups. During pulse-DC composite electrodeposition, the modified silica particles migrate to the cathode surface, acting as heterogeneous nucleation centers to promote metal grain refinement. Simultaneously, they are coated by the coating matrix deposited on the substrate surface, effectively filling the micropores of the coating and improving its density. When the concentration of modified silica is within the range specified in this invention, it ensures a sufficient number of nucleation sites, significantly improving the mechanical properties and corrosion resistance of the coating through grain boundary strengthening and pore filling, while avoiding the increase in composite plating bath viscosity and particle agglomeration caused by excessive particles. This is beneficial for forming a high-quality coating with uniform structure and fewer defects.

[0085] When the concentration of modified silica is below 3 g / L, the density of heterogeneous nucleation sites is insufficient, limiting its effect on grain refinement. The resulting coarse grains in the coating not only reduce its hardness but also negatively impact corrosion resistance due to fewer grain boundaries. Furthermore, insufficient modified silica weakens its ability to fill pores and defects in the coating, failing to effectively block the penetration pathways of corrosive media. Consequently, both the density and corrosion resistance of the coating are affected.

[0086] When the concentration of modified silica exceeds 4 g / L, the high concentration of modified silica particles is prone to agglomeration, forming larger secondary particles. These agglomerates become stress concentration points in the coating, easily leading to microcracks. Furthermore, excessive modified silica significantly increases the viscosity of the composite plating solution, hindering the migration and deposition of metal ions. This results in uneven deposition rates of metal ions on the substrate surface, ultimately leading to a rough coating surface or even nodule formation.

[0087] As a preferred embodiment of the present invention, in step (III), the current density of the pulse current is 4~6 A / dm. 2 For example, it could be 4.0A / dm 2 4.2A / dm 2 4.4A / dm 2 4.6A / dm 2 4.8A / dm 2 5.0A / dm 2 5.2A / dm 2 5.4A / dm 2 5.6A / dm 2 5.8A / dm 2 Or 6.0A / dm 2 However, this does not apply to all values ​​listed; other unlisted values ​​within the same range also apply.

[0088] This invention specifically limits the pulse current density to 4~6 A / dm. 2 Within this range, the cathode surface can obtain sufficient deposition overpotential to promote the co-deposition of nickel ions, tungsten ions and phosphorus ions, while ensuring that modified alumina, modified boron nitride and modified silicon dioxide can effectively migrate and be embedded in the coating under the action of the electric field. The higher current density is conducive to the formation of fine crystal nuclei, providing a dense underlying structure for the coating.

[0089] When the current density is below 4A / dm 2 At low current densities, the metal ion reduction rate is too slow, significantly reducing the coating deposition efficiency. This results in excessively long suspension times for modified alumina, modified boron nitride, and modified silica in the composite plating solution, increasing the risk of agglomeration and sedimentation. Ultimately, this affects the amount and uniformity of the incorporation of these substances in the coating. Furthermore, the nucleation rate is slow at low current densities, leading to predominantly grain growth and the formation of coarse grain structures, which significantly impacts the hardness, density, and corrosion resistance of the coating.

[0090] When the current density is higher than 6A / dm 2 Excessively high deposition rates can exacerbate concentration polarization in the diffusion layer at the cathode interface, leading to insufficient metal ion supply and problems such as inclusions of hydrogen evolution reaction byproducts and abnormal dendrite growth. Simultaneously, high current densities significantly increase deposition stress, increasing coating brittleness and making it prone to microcracks or peeling. Furthermore, modified alumina, modified boron nitride, and modified silica are difficult to fully coat by the substrate during rapid deposition, resulting in uneven particle distribution, increased agglomerates, and reduced interfacial bonding strength with the substrate, thus affecting the strengthening effect of nanoparticles on the coating.

[0091] In some optional instances, the pulse frequency of the pulse current is 300 to 400 Hz, for example, it can be 300 Hz, 310 Hz, 320 Hz, 330 Hz, 340 Hz, 350 Hz, 360 Hz, 370 Hz, 380 Hz, 390 Hz or 400 Hz, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0092] In some optional instances, the duty cycle of the pulse current is 35-45%, for example, it can be 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44% or 45%, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0093] In some optional instances, the pulse electroplating time is 10 to 20 minutes, for example, 10 minutes, 11 minutes, 12 minutes, 13 minutes, 14 minutes, 15 minutes, 16 minutes, 17 minutes, 18 minutes, 19 minutes or 20 minutes, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0094] The purpose of the pulse electroplating stage is to rapidly form a dense, fine-grained, and well-bonded bottom layer on the substrate surface. A strong, instantaneous high current density is generated by a high-frequency pulse current of 300-400 Hz. This intermittent power supply effectively reduces the thickness of the cathode diffusion layer and greatly alleviates concentration polarization. The high peak current provides extremely high electrochemical polarization, significantly increasing the nucleation rate, allowing metal ions to be reduced in large quantities and form ultrafine grains in a short time. During the current-off period, metal ions are replenished, preventing dendrite growth caused by metal ion depletion. Simultaneously, the strong current disturbance facilitates the migration of modified alumina, modified boron nitride, and modified silica to the cathode and their capture by the rapidly deposited substrate, ensuring that these modified nanoparticles are uniformly distributed in the bottom layer of the coating.

[0095] In some optional instances, after the pulse electroplating is completed, the current density of the pulse current is continuously and linearly reduced to 1-2 A / dm² within 5-10 minutes. 2 Simultaneously, the duty cycle of the pulse current is continuously and linearly increased to 100% to switch the pulse current to direct current. The duration can be 5.0 min, 5.5 min, 6.0 min, 6.5 min, 7.0 min, 7.5 min, 8.0 min, 8.5 min, 9.0 min, 9.5 min, or 10.0 min; the current density can be 1.0 A / dm³. 2 1.1A / dm 2 1.2A / dm 2 1.3A / dm 2 1.4A / dm 2 1.5A / dm 2 1.6A / dm 2 1.7A / dm 2 1.8A / dm 2 1.9A / dm 2 Or 2.0A / dm 2 However, this does not apply to all values ​​listed; other unlisted values ​​within the same range also apply.

[0096] This invention specifically defines the continuous linear reduction of the pulse current density to 1~2 A / dm. 2Direct current plating in a lower current density range helps to reduce concentration polarization and electrochemical polarization, allowing metal ions to deposit at a more controllable rate. This results in the formation of a fine-grained, dense coating in the middle and surface layers. At the same time, the lower current density helps to reduce the accumulation of internal stress during the deposition process, reduce the risk of hydrogen embrittlement, improve the toughness of the coating, and ultimately obtain a coating with excellent overall performance.

[0097] When the current density is less than 1A / dm 2 At low current densities, the deposition rate of metal ions is too slow, leading to discontinuous deposition of the coating and the formation of a porous structure, which severely affects the density and corrosion resistance of the coating. In addition, the migration rates of modified alumina, modified boron nitride, and modified silica slow down at low current densities, making them prone to agglomeration, which affects their dispersion uniformity in the coating and thus weakens the strengthening effect of nanoparticles on the coating.

[0098] When the current density exceeds 2A / dm 2 At higher deposition rates, concentration polarization increases significantly. Although the deposition rate increases, excessively rapid growth can lead to coarse grains and reduce the mechanical properties of the coating. In addition, modified alumina, modified boron nitride, and modified silicon dioxide are difficult to be stably captured by the coating substrate at high current densities. They are pushed out due to excessively rapid metal ion deposition and accumulate at grain boundaries, forming stress concentration points.

[0099] It should be noted that the "continuous linear decrease" defined in this invention means that the rate of decrease of the peak current density is constant. For example, the current density of the pulse current decreases from 4 A / dm³ within 5 minutes. 2 Reduced to 2A / dm 2 Therefore, the rate of decrease in the current density of the pulse current is 0.4 A / dm per minute. 2 .

[0100] In some optional instances, the DC electroplating time is 40 to 50 minutes, for example, 40 minutes, 41 minutes, 42 minutes, 43 minutes, 44 minutes, 45 minutes, 46 minutes, 47 minutes, 48 ​​minutes, 49 minutes or 50 minutes, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0101] In some optional instances, during the electroplating process, the composite plating solution is stirred and the temperature of the composite plating solution is maintained at 70~80°C, for example, 70°C, 71°C, 72°C, 73°C, 74°C, 75°C, 76°C, 77°C, 78°C, 79°C or 80°C, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0102] The purpose of the DC electroplating stage is to achieve stable and efficient coating thickening based on the existing base layer, while ensuring the uniformity of the coating structure in the thickness direction and low internal stress. Under a constant low current density, the deposition rate of metal ions is moderate, the crystal growth mode tends to be stable, and the steady-state current is conducive to the uniform growth of the coating thickness, avoiding the problem of internal defect accumulation that occurs during the coating thickening process in pulse electroplating. At the same time, the lower current density can effectively suppress the occurrence of hydrogen evolution side reactions, reduce the risk of hydrogen embrittlement of the coating, and significantly reduce the internal stress during the deposition process, avoiding coating warping or peeling.

[0103] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0104] This invention modifies the surfaces of alumina, boron nitride, and silica nanoparticles using silane coupling agents, hexadecyltrimethylammonium bromide, and polyacrylic acid, respectively, significantly improving their dispersion stability in the composite plating bath and their interfacial bonding performance with the coating substrate. By optimizing the component ratio of the composite plating bath and combining it with a pulse-DC electrochemical composite deposition process, a gradient coating structure is finally formed, from a dense fine-grained bottom layer (formed during the pulse electroplating stage) to a low-stress main layer (formed during the DC electroplating stage), resulting in a nickel-tungsten-phosphorus alloy composite coating with high hardness, low friction, high wear resistance, and corrosion resistance. Attached Figure Description

[0105] Figure 1 This is a scanning electron microscope (SEM) image of the nickel-tungsten-phosphorus alloy coating prepared in Example 1 of the present invention.

[0106] Figure 2 This is a cross-sectional scanning electron microscope image of the nickel-tungsten-phosphorus alloy coating prepared in Example 1 of the present invention;

[0107] Figure 3 This is a scanning electron microscope (SEM) image of the nickel-tungsten-phosphorus alloy coating prepared in Example 1 of the present invention after a wear test.

[0108] Figure 4 This is a scanning electron microscope (SEM) image of the nickel-tungsten-phosphorus alloy coating prepared in Comparative Example 6 of the present invention after a wear test. Detailed Implementation

[0109] The technical solutions of the present invention will be described in detail below with reference to specific embodiments and accompanying drawings. The embodiments described herein are specific implementations of the present invention, used to illustrate the concept of the present invention; these descriptions are explanatory and exemplary, and should not be construed as limiting the implementation methods or the scope of protection of the present invention. In addition to the embodiments described herein, those skilled in the art can employ other obvious technical solutions based on the content disclosed in the claims and specification of this application. These technical solutions include those that make any obvious substitutions and modifications to the embodiments described herein.

[0110] Example 1

[0111] This embodiment provides a pulse-DC electrochemical composite deposition process for nickel-tungsten-phosphorus alloy coatings, which specifically includes the following steps:

[0112] Step (1) α-alumina with an average particle size of 50 nm was dispersed in a silane coupling agent solution (composed of silane coupling agent KH550 and an ethanol aqueous solution with a volume ratio of 8:2). The mass fraction of silane coupling agent KH550 in the silane coupling agent solution was 1 wt%. The dispersion was ultrasonically dispersed for 50 min at 400 W ultrasonic power under the condition of heating in a water bath at 50 °C. Then, the mixture was filtered. The filter cake obtained by the filtration was washed with anhydrous ethanol. After washing, it was dried at 80 °C for 4 h to obtain modified alumina.

[0113] Step (2) Hexagonal boron nitride was dispersed in an aqueous solution of hexadecyltrimethylammonium bromide with a mass fraction of 0.5 wt%, and the mass ratio of hexagonal boron nitride to hexadecyltrimethylammonium bromide was 1:13. At the same time, it was treated for 4 h at a stirring speed of 300 rpm, a heating temperature of 60 °C and an ultrasonic power of 500 W. Then, it was centrifuged at a speed of 8000 rpm for 15 min, the precipitate was washed, and then dried at 80 °C for 4 h to obtain modified boron nitride.

[0114] Step (3) Disperse nano-silica with an average particle size of 30 nm in a 1 g / L aqueous solution of polyacrylic acid. The mass ratio of nano-silica to polyacrylic acid is 1:1. The mixture is treated at a heating temperature of 40 °C and an ultrasonic power of 300 W for 2 h. Then, it is filtered and the resulting filter cake is washed. After washing, it is dried at 60 °C for 3 h to obtain modified silica.

[0115] Step (4) Add nickel sulfate, sodium tungstate, citric acid and sodium acetate to deionized water in sequence. Stir until completely dissolved after each component is added before adding the next component. Add 20 wt% sodium hydroxide solution to the resulting mixed solution to adjust its pH value to 7. Add sodium hypophosphite to the mixed solution and stir until completely dissolved. Continue to add sodium saccharin, 1,4-butynediol, sodium dodecyl sulfate, modified alumina obtained in step (1), modified boron nitride obtained in step (2) and modified silica obtained in step (3). Treat for 2 hours at a stirring speed of 300 rpm, a heating temperature of 45°C and an ultrasonic power of 500 W to obtain a composite plating solution.

[0116] In the composite plating solution, the concentrations of nickel sulfate (20 g / L), sodium tungstate (58 g / L), sodium hypophosphite (18 g / L), citric acid (90 g / L), sodium acetate (20 g / L), sodium saccharin (3 g / L), 1,4-butynediol (0.3 g / L), sodium dodecyl sulfate (0.2 g / L), modified alumina (4 g / L), modified boron nitride (2 g / L), and modified silica (4 g / L) are all present.

[0117] Step (5) Using a stainless steel plate as the cathode, immerse the stainless steel plate and the platinum-titanium coated mesh in a composite plating solution at 70°C, stir the composite plating solution, turn on the pulse power supply, and apply a pulse current to the stainless steel plate for pulse electroplating. The current density of the pulse current is 4A / dm. 2 The pulse frequency is 300Hz and the duty cycle is 35%.

[0118] After 20 minutes of pulse electroplating, the current density of the pulse current was reduced from 4 A / dm³ within 5 minutes. 2 Continuous linear reduction to 1 A / dm 2 Simultaneously, the duty cycle of the pulse current is continuously and linearly increased to 100% to switch pulse electroplating to DC electroplating, finally at 1A / dm 2 DC electroplating was performed at a current density of 50 min to form a nickel-tungsten-phosphorus alloy coating on the surface of the stainless steel plate.

[0119] Figure 1 The image shows a scanning electron microscope (SEM) image of the nickel-tungsten-phosphorus alloy coating prepared in this embodiment. As can be seen from the image, the alloy microstructure of the nickel-tungsten-phosphorus alloy coating is a cellular structure with dense crystals, and uniformly dispersed modified nanoparticles can be seen.

[0120] Figure 2 The image shows a cross-sectional scanning electron microscope (SEM) image of the nickel-tungsten-phosphorus alloy coating prepared in this embodiment. As can be seen from the image, the nickel-tungsten-phosphorus alloy coating has a thickness of about 5 μm, a dense structure, no defects such as pores, and a tight bond at the interface between the coating and the stainless steel plate.

[0121] Example 2

[0122] This embodiment provides a pulse-DC electrochemical composite deposition process for nickel-tungsten-phosphorus alloy coatings, which specifically includes the following steps:

[0123] Step (1) α-alumina with an average particle size of 60 nm was dispersed in a silane coupling agent solution (composed of silane coupling agent KH550 and an ethanol aqueous solution with a volume ratio of 8:2). The mass fraction of silane coupling agent KH550 in the silane coupling agent solution was 1.2 wt%. The dispersion was ultrasonically dispersed at 420 W for 45 min under water bath heating at 52 °C. Then, the mixture was filtered. The filter cake obtained by filtration was washed with anhydrous ethanol. After washing, it was dried at 82 °C for 3.8 h to obtain modified alumina.

[0124] Step (2) Hexagonal boron nitride was dispersed in an aqueous solution of hexadecyltrimethylammonium bromide with a mass fraction of 0.6 wt%, and the mass ratio of hexagonal boron nitride to hexadecyltrimethylammonium bromide was 1:13.5. The mixture was treated for 3.8 h at a stirring speed of 350 rpm, a heating temperature of 62 °C and an ultrasonic power of 480 W. Then, it was centrifuged at a speed of 8500 rpm for 13 min. The precipitate was washed and dried at 82 °C for 3.8 h to obtain modified boron nitride.

[0125] Step (3) Disperse nano-silica with an average particle size of 35 nm in a 1.2 g / L aqueous solution of polyacrylic acid. The mass ratio of nano-silica to polyacrylic acid is 1:1.2. The mixture is treated at a heating temperature of 42 °C and an ultrasonic power of 320 W for 1.8 h. Then, it is filtered and the resulting filter cake is washed. After washing, it is dried at 65 °C for 2.8 h to obtain modified silica.

[0126] Step (4) Add nickel sulfate, sodium tungstate, citric acid and sodium acetate to deionized water in sequence. Stir until completely dissolved after each component is added before adding the next component. Add 20 wt% sodium hydroxide solution to the resulting mixed solution to adjust its pH value to 7.2. Add sodium hypophosphite to the mixed solution and stir until completely dissolved. Continue to add sodium saccharin, 1,4-butynediol, sodium dodecyl sulfate, modified alumina obtained in step (1), modified boron nitride obtained in step (2) and modified silicon dioxide obtained in step (3). Treat for 1.2 h at a stirring speed of 320 rpm, a heating temperature of 48 ℃ and an ultrasonic power of 480 W to obtain a composite plating solution.

[0127] In the composite plating solution, the concentrations of nickel sulfate (22 g / L), sodium tungstate (60 g / L), sodium hypophosphite (25 g / L), citric acid (80 g / L), sodium acetate (20 g / L), sodium saccharin (1 g / L), 1,4-butynediol (0.2 g / L), sodium dodecyl sulfate (0.2 g / L), modified alumina (5 g / L), modified boron nitride (3 g / L), and modified silica (3 g / L) are all present.

[0128] Step (5) Using a stainless steel plate as the cathode, immerse the stainless steel plate and the platinum-titanium coated mesh in a composite plating solution at 72°C, stir the composite plating solution, turn on the pulse power supply, and apply a pulse current to the stainless steel plate for pulse electroplating. The current density of the pulse current is 4.5 A / dm. 2 The pulse frequency is 320Hz and the duty cycle is 38%.

[0129] After 18 minutes of pulse electroplating, the current density of the pulse current was reduced from 4.5 A / dm³ within 6 minutes. 2 The continuous linear reduction was reduced to 1.2 A / dm. 2 Simultaneously, the duty cycle of the pulse current is continuously and linearly increased to 100% to switch pulse electroplating to DC electroplating, finally at 1.2 A / dm 2 DC electroplating was performed at a current density of 48 min to form a nickel-tungsten-phosphorus alloy coating on the surface of the stainless steel plate.

[0130] Example 3

[0131] This embodiment provides a pulse-DC electrochemical composite deposition process for nickel-tungsten-phosphorus alloy coatings, which specifically includes the following steps:

[0132] Step (1) α-alumina with an average particle size of 70 nm was dispersed in a silane coupling agent solution (composed of silane coupling agent KH550 and an ethanol aqueous solution with a volume ratio of 8:2). The mass fraction of silane coupling agent KH550 in the silane coupling agent solution was 1.5 wt%. The dispersion was ultrasonically dispersed at 450 W for 40 min under the conditions of water bath heating at 55 °C. Then, the mixture was filtered. The filter cake obtained by vacuum filtration was washed with anhydrous ethanol. After washing, it was dried at 85 °C for 3.5 h to obtain modified alumina.

[0133] Step (2) Hexagonal boron nitride was dispersed in a 0.7 wt% aqueous solution of hexadecyltrimethylammonium bromide, with a mass ratio of hexagonal boron nitride to hexadecyltrimethylammonium bromide of 1:14. The mixture was then treated for 3.5 h at a stirring speed of 400 rpm, a heating temperature of 65 °C, and an ultrasonic power of 450 W. Subsequently, the mixture was centrifuged at a speed of 9000 rpm for 12 min. The precipitate was washed and then dried at 85 °C for 3.5 h to obtain modified boron nitride.

[0134] Step (3) Disperse nano-silica with an average particle size of 40 nm in a 1.5 g / L aqueous solution of polyacrylic acid. The mass ratio of nano-silica to polyacrylic acid is 1:1.5. The mixture is treated at a heating temperature of 45 °C and an ultrasonic power of 350 W for 1.5 h. Then, it is filtered and the resulting filter cake is washed. After washing, it is dried at 70 °C for 2.5 h to obtain modified silica.

[0135] Step (4) Add nickel sulfate, sodium tungstate, citric acid and sodium acetate to deionized water in sequence. Stir until completely dissolved after each component is added before adding the next component. Add 20wt% sodium hydroxide solution to the resulting mixed solution to adjust its pH value to 7.5. Add sodium hypophosphite to the mixed solution and stir until completely dissolved. Continue to add sodium saccharin, 1,4-butynediol, sodium dodecyl sulfate, modified alumina obtained in step (1), modified boron nitride obtained in step (2) and modified silica obtained in step (3). Treat for 1.5h at a stirring speed of 350rpm, a heating temperature of 50℃ and an ultrasonic power of 450W to obtain a composite plating solution.

[0136] In the composite plating solution, the concentrations of nickel sulfate (25 g / L), sodium tungstate (55 g / L), sodium hypophosphite (23 g / L), citric acid (85 g / L), sodium acetate (18 g / L), sodium saccharin (3 g / L), 1,4-butynediol (0.4 g / L), sodium dodecyl sulfate (0.1 g / L), modified alumina (4.5 g / L), modified boron nitride (2 g / L), and modified silica (3.8 g / L) are all present.

[0137] Step (5) Using a stainless steel plate as the cathode, immerse the stainless steel plate and the platinum-titanium coated mesh in a composite plating solution at 75°C, stir the composite plating solution, turn on the pulse power supply, and apply a pulse current to the stainless steel plate for pulse electroplating. The current density of the pulse current is 5A / dm. 2 The pulse frequency is 350Hz and the duty cycle is 40%.

[0138] After pulse electroplating for 15 minutes, the current density of the pulse current was reduced from 5 A / dm³ within 7 minutes. 2The continuous linear reduction was reduced to 1.5 A / dm. 2 Simultaneously, the duty cycle of the pulse current is continuously and linearly increased to 100% to switch pulse electroplating to DC electroplating, finally at 1.5 A / dm 2 DC electroplating was performed at a current density of 45 min to form a nickel-tungsten-phosphorus alloy coating on the surface of the stainless steel plate.

[0139] Example 4

[0140] This embodiment provides a pulse-DC electrochemical composite deposition process for nickel-tungsten-phosphorus alloy coatings, which specifically includes the following steps:

[0141] Step (1) α-alumina with an average particle size of 80 nm was dispersed in a silane coupling agent solution (composed of silane coupling agent KH550 and an ethanol aqueous solution with a volume ratio of 8:2). The mass fraction of silane coupling agent KH550 in the silane coupling agent solution was 1.8 wt%. The dispersion was ultrasonically dispersed for 35 min at an ultrasonic power of 480 W under the condition of water bath heating at 58 °C. Then, the mixture was filtered. The filter cake obtained by vacuum filtration was washed with anhydrous ethanol. After washing, it was dried at 88 °C for 3.2 h to obtain modified alumina.

[0142] Step (2) Hexagonal boron nitride was dispersed in an aqueous solution of hexadecyltrimethylammonium bromide with a mass fraction of 0.8 wt%, and the mass ratio of hexagonal boron nitride to hexadecyltrimethylammonium bromide was 1:14.5. The mixture was treated for 3.2 h at a stirring speed of 450 rpm, a heating temperature of 68 °C and an ultrasonic power of 420 W. Then, it was centrifuged at a speed of 9500 rpm for 11 min. The precipitate was washed and dried at 88 °C for 3.2 h to obtain modified boron nitride.

[0143] Step (3) Disperse nano-silica with an average particle size of 45 nm in a 1.8 g / L aqueous solution of polyacrylic acid. The mass ratio of nano-silica to polyacrylic acid is 1:1.8. The mixture is treated at a heating temperature of 48 °C and an ultrasonic power of 380 W for 1.2 h. Then, it is filtered and the resulting filter cake is washed. After washing, it is dried at 75 °C for 2.2 h to obtain modified silica.

[0144] Step (4) Add nickel sulfate, sodium tungstate, citric acid and sodium acetate to deionized water in sequence. Stir until completely dissolved after each component is added before adding the next component. Add 20 wt% sodium hydroxide solution to the resulting mixed solution to adjust its pH value to 7.8. Add sodium hypophosphite to the mixed solution and stir until completely dissolved. Continue to add sodium saccharin, 1,4-butynediol, sodium dodecyl sulfate, modified alumina obtained in step (1), modified boron nitride obtained in step (2) and modified silicon dioxide obtained in step (3). Treat for 1.2 h at a stirring speed of 380 rpm, a heating temperature of 52 °C and an ultrasonic power of 420 W to obtain a composite plating solution.

[0145] In the composite plating solution, the concentrations of nickel sulfate (28 g / L), sodium tungstate (50 g / L), sodium hypophosphite (20 g / L), citric acid (100 g / L), sodium acetate (10 g / L), sodium saccharin (1.5 g / L), 1,4-butynediol (0.1 g / L), sodium dodecyl sulfate (0.1 g / L), modified alumina (4.8 g / L), modified boron nitride (2 g / L), and modified silica (3 g / L) are all present.

[0146] Step (5) Using a stainless steel plate as the cathode, immerse the stainless steel plate and the platinum-titanium coated mesh in a composite plating solution at 78°C, stir the composite plating solution, turn on the pulse power supply, and apply a pulse current to the stainless steel plate for pulse electroplating. The current density of the pulse current is 5.5 A / dm. 2 The pulse frequency is 380Hz and the duty cycle is 42%.

[0147] After 12 minutes of pulse electroplating, the current density of the pulse current was reduced from 5.5 A / dm³ within 8 minutes. 2 The continuous linear reduction was reduced to 1.8 A / dm. 2 Simultaneously, the duty cycle of the pulse current is continuously and linearly increased to 100% to switch pulse electroplating to DC electroplating, finally at 1.8 A / dm 2 DC electroplating was performed at a current density of 42 min to form a nickel-tungsten-phosphorus alloy coating on the surface of the stainless steel plate.

[0148] Example 5

[0149] This embodiment provides a pulse-DC electrochemical composite deposition process for nickel-tungsten-phosphorus alloy coatings, which specifically includes the following steps:

[0150] Step (1) α-alumina with an average particle size of 100 nm was dispersed in a silane coupling agent solution (composed of silane coupling agent KH550 and an ethanol aqueous solution with a volume ratio of 8:2). The mass fraction of silane coupling agent KH550 in the silane coupling agent solution was 2 wt%. The dispersion was ultrasonically dispersed for 30 min at 500 W ultrasonic power under the conditions of water bath heating at 60 °C. Then, the mixture was filtered. The filter cake obtained by vacuum filtration was washed with anhydrous ethanol. After washing, it was dried at 90 °C for 3 h to obtain modified alumina.

[0151] Step (2) Hexagonal boron nitride was dispersed in a 1 wt% aqueous solution of hexadecyltrimethylammonium bromide, with a mass ratio of 1:15 between hexagonal boron nitride and hexadecyltrimethylammonium bromide. The mixture was then treated for 3 h at a stirring speed of 500 rpm, a heating temperature of 70 °C, and an ultrasonic power of 400 W. Subsequently, it was centrifuged at a speed of 10000 rpm for 10 min. The precipitate was washed and then dried at 90 °C for 3 h to obtain modified boron nitride.

[0152] Step (3) Disperse nano-silica with an average particle size of 50 nm in a 2 g / L aqueous solution of polyacrylic acid. The mass ratio of nano-silica to polyacrylic acid is 1:2. The mixture is treated at a heating temperature of 50 °C and an ultrasonic power of 400 W for 1 h. Then, it is filtered and the resulting filter cake is washed. After washing, it is dried at 80 °C for 2 h to obtain modified silica.

[0153] Step (4) Add nickel sulfate, sodium tungstate, citric acid and sodium acetate to deionized water in sequence. Stir until completely dissolved after each component is added before adding the next component. Add 20wt% sodium hydroxide solution to the resulting mixed solution to adjust its pH value to 8. Add sodium hypophosphite to the mixed solution and stir until completely dissolved. Continue to add sodium saccharin, 1,4-butynediol, sodium dodecyl sulfate, modified alumina obtained in step (1), modified boron nitride obtained in step (2) and modified silica obtained in step (3). Treat for 1 hour at a stirring speed of 400 rpm, a heating temperature of 55℃ and an ultrasonic power of 400W to obtain a composite plating solution.

[0154] In the composite plating solution, the concentrations of nickel sulfate (30 g / L), sodium tungstate (53 g / L), sodium hypophosphite (15 g / L), citric acid (95 g / L), sodium acetate (15 g / L), sodium saccharin (2.5 g / L), 1,4-butynediol (0.5 g / L), sodium dodecyl sulfate (0.1 g / L), modified alumina (4.2 g / L), modified boron nitride (1 g / L), and modified silica (3.2 g / L) are all present.

[0155] Step (5) Using a stainless steel plate as the cathode, immerse the stainless steel plate and the platinum-titanium coated mesh in a composite plating solution at 80°C, stir the composite plating solution, turn on the pulse power supply, and apply a pulse current to the stainless steel plate for pulse electroplating. The current density of the pulse current is 6A / dm. 2 The pulse frequency is 400Hz and the duty cycle is 45%.

[0156] After 10 minutes of pulse electroplating, the current density of the pulse current was reduced from 6 A / dm³ within 10 minutes. 2 Continuous linear reduction to 2A / dm 2 Simultaneously, the duty cycle of the pulse current is continuously and linearly increased to 100% to switch the pulse electroplating to DC electroplating, finally at 2A / dm 2 DC electroplating was performed at a current density of 40 min to form a nickel-tungsten-phosphorus alloy coating on the surface of the stainless steel plate.

[0157] Comparative Example 1

[0158] This comparative example provides a pulse-DC electrochemical composite deposition process for nickel-tungsten-phosphorus alloy coating. The difference from Example 1 is that in step (4), the concentration of modified alumina in the composite plating solution is adjusted to 2 g / L. Other operating steps and process parameters are exactly the same as in Example 1. This comparative example will not be repeated here. The nickel-tungsten-phosphorus alloy coating is finally formed on the surface of stainless steel plate through the composite deposition process.

[0159] Comparative Example 2

[0160] This comparative example provides a pulse-DC electrochemical composite deposition process for nickel-tungsten-phosphorus alloy coating. The difference from Example 1 is that in step (4), the concentration of modified alumina in the composite plating solution is adjusted to 8 g / L. Other operating steps and process parameters are exactly the same as in Example 1. This comparative example will not be repeated here. The nickel-tungsten-phosphorus alloy coating is finally formed on the surface of stainless steel plate through the composite deposition process.

[0161] Comparative Example 3

[0162] This comparative example provides a pulse-DC electrochemical composite deposition process for nickel-tungsten-phosphorus alloy coating. The difference from Example 1 is that in step (4), the concentration of modified boron nitride in the composite plating solution is adjusted to 0.1 g / L. Other operating steps and process parameters are exactly the same as in Example 1. This comparative example will not be repeated here. The nickel-tungsten-phosphorus alloy coating is finally formed on the surface of stainless steel plate through the composite deposition process.

[0163] Comparative Example 4

[0164] This comparative example provides a pulse-DC electrochemical composite deposition process for nickel-tungsten-phosphorus alloy coating. The difference from Example 1 is that in step (4), the concentration of modified boron nitride in the composite plating solution is adjusted to 5 g / L. Other operating steps and process parameters are exactly the same as in Example 1. This comparative example will not be repeated here. The nickel-tungsten-phosphorus alloy coating is finally formed on the surface of stainless steel plate through the composite deposition process.

[0165] Comparative Example 5

[0166] This comparative example provides a pulse-DC electrochemical composite deposition process for nickel-tungsten-phosphorus alloy coating. The difference from Example 1 is that in step (4), the concentration of modified silica in the composite plating solution is adjusted to 1 g / L. Other operating steps and process parameters are exactly the same as in Example 1. This comparative example will not be repeated here. The nickel-tungsten-phosphorus alloy coating is finally formed on the surface of stainless steel plate through the composite deposition process.

[0167] Comparative Example 6

[0168] This comparative example provides a pulse-DC electrochemical composite deposition process for nickel-tungsten-phosphorus alloy coating. The difference from Example 1 is that in step (4), the concentration of modified silica in the composite plating solution is adjusted to 6 g / L. Other operating steps and process parameters are exactly the same as in Example 1. This comparative example will not be repeated here. The nickel-tungsten-phosphorus alloy coating is finally formed on the surface of stainless steel plate through the composite deposition process.

[0169] Comparative Example 7

[0170] This comparative example provides a pulse-DC electrochemical composite deposition process for nickel-tungsten-phosphorus alloy coatings. The difference from Example 1 is that in step (5), when the pulse power supply is turned on and a pulse current is applied to the stainless steel plate for pulse electroplating, the current density of the pulse current is adjusted to 2A / dm³. 2 Other operating steps and process parameters are exactly the same as in Example 1, and will not be repeated here. The nickel-tungsten-phosphorus alloy coating is finally formed on the surface of the stainless steel plate through the composite deposition process.

[0171] Comparative Example 8

[0172] This comparative example provides a pulse-DC electrochemical composite deposition process for nickel-tungsten-phosphorus alloy coatings. The difference from Example 1 is that in step (5), when the pulse power supply is turned on and a pulse current is applied to the stainless steel plate for pulse electroplating, the current density of the pulse current is adjusted to 8 A / dm. 2 Other operating steps and process parameters are exactly the same as in Example 1, and will not be repeated here. A nickel-tungsten-phosphorus alloy coating is finally formed on the surface of the stainless steel plate through a composite deposition process.

[0173] Comparative Example 9

[0174] This comparative example provides a pulse-DC electrochemical composite deposition process for nickel-tungsten-phosphorus alloy coatings. The difference from Example 1 is that in step (5), the current density of the pulse current is continuously and linearly reduced to 0.1 A / dm³. 2 Other operating steps and process parameters are exactly the same as in Example 1, and will not be repeated here. A nickel-tungsten-phosphorus alloy coating is finally formed on the surface of the stainless steel plate through a composite deposition process.

[0175] Comparative Example 10

[0176] This comparative example provides a pulse-DC electrochemical composite deposition process for nickel-tungsten-phosphorus alloy coatings. The difference from Example 1 is that in step (5), the current density of the pulse current is continuously and linearly reduced to 3 A / dm. 2 Other operating steps and process parameters are exactly the same as in Example 1, and will not be repeated here. A nickel-tungsten-phosphorus alloy coating is finally formed on the surface of the stainless steel plate through a composite deposition process.

[0177] Comparative Example 11

[0178] This comparative example provides a pulse-DC electrochemical composite deposition process for nickel-tungsten-phosphorus alloy coating. The difference from Example 1 is that steps (2) and (3) are omitted, and modified boron nitride and modified silicon dioxide are not added in step (4). Other operation steps and process parameters are exactly the same as in Example 1. This comparative example will not be repeated here. The nickel-tungsten-phosphorus alloy coating is finally formed on the surface of stainless steel plate through the composite deposition process.

[0179] Comparative Example 12

[0180] This comparative example provides a pulse-DC electrochemical composite deposition process for nickel-tungsten-phosphorus alloy coating. The difference from Example 1 is that steps (1) and (2) are omitted, and modified alumina and modified boron nitride are not added in step (4). Other operation steps and process parameters are exactly the same as in Example 1. This comparative example will not be repeated here. The nickel-tungsten-phosphorus alloy coating is finally formed on the surface of stainless steel plate through the composite deposition process.

[0181] Comparative Example 13

[0182] This comparative example provides a pulse-DC electrochemical composite deposition process for nickel-tungsten-phosphorus alloy coating. The difference from Example 1 is that steps (1) and (3) are omitted, and modified alumina and modified silicon dioxide are not added in step (4). Other operation steps and process parameters are exactly the same as in Example 1. This comparative example will not be repeated here. The nickel-tungsten-phosphorus alloy coating is finally formed on the surface of stainless steel plate through the composite deposition process.

[0183] The Vickers hardness, volumetric wear, coefficient of friction, and corrosion current density of the nickel-tungsten-phosphorus alloy coatings prepared in Examples 1-5 and Comparative Examples 1-13 were tested. The specific test steps are as follows:

[0184] (1) Vickers hardness:

[0185] The Vickers hardness of nickel-tungsten-phosphorus alloy coatings was tested in accordance with the national standard GB / T 4340.1-2024 "Metallic materials - Vickers hardness test - Part 1: Test method".

[0186] (2) Volumetric wear:

[0187] Referring to the national standard GB / T 12444-2006 "Test Methods for Wear of Metallic Materials - Sliding Wear Test of Test Ring-Block", the volumetric wear of nickel-tungsten-phosphorus alloy coatings was tested.

[0188] (3) Coefficient of friction:

[0189] The friction coefficient of nickel-tungsten-phosphorus alloy coatings was tested in accordance with the national standard GB / T 12444-2006 "Test Methods for Wear of Metallic Materials - Sliding Wear Test of Test Ring-Block".

[0190] (4) Corrosion current density:

[0191] The corrosion current density of nickel-tungsten-phosphorus alloy coatings was tested in accordance with the national standard GB / T 24196-2009 "Electrochemical Test Methods for Corrosion of Metals and Alloys - Guidelines for Measurement of Potentiostatic and Potentiodynamic Polarization".

[0192] The test results are shown in Table 1.

[0193] Table 1. Performance test results of nickel-tungsten-phosphorus alloy coatings prepared in Examples 1-5 and Comparative Examples 1-13

[0194]

[0195] The test data from Examples 1, 1, and 2 show that when the concentration of modified alumina is too low (Comparative Example 1), the hardness and resistance to plastic deformation of the coating cannot be effectively improved due to insufficient reinforcing phase, resulting in decreased wear resistance. Corrosion resistance is also reduced due to insufficient coating density. When the concentration of modified alumina is too high (Comparative Example 2), the modified alumina particles severely agglomerate. These agglomerates not only become stress concentration points, weakening the overall mechanical properties of the coating, but also easily detach during friction to form third abrasive grains, causing abrasive wear and increasing volumetric wear. Furthermore, the structural defects caused by the agglomerates provide channels for corrosive media, significantly reducing corrosion resistance.

[0196] The test data from Examples 1, 3, and 4 show that when the concentration of modified boron nitride is too low (Comparative Example 3), a complete and effective lubrication transfer film cannot be formed at the friction interface, leading to an increase in the coefficient of friction, a decrease in the lubrication and friction reduction effect, and an increase in volumetric wear. When the concentration of modified boron nitride is too high (Comparative Example 4), the modified boron nitride is prone to stacking and agglomeration, which disrupts its parallel orientation in the coating, making it difficult to exert the lubricating effect of the layered material. At the same time, the agglomerates also become defect points, reducing the density and bonding strength of the coating, resulting in a decrease in the wear resistance and corrosion resistance of the coating.

[0197] The test data from Examples 1, 5, and 6 show that when the concentration of modified silica is too low (Comparative Example 5), the number of heterogeneous nucleation sites is insufficient, the grain refinement effect is limited, the coating is relatively rough, and there are many micropores. This not only reduces the hardness of the coating but also makes it easier for corrosive media to penetrate, resulting in poor corrosion resistance. When the concentration of modified silica is too high (Comparative Example 6), the modified silica particles are prone to agglomeration, forming large agglomerates that disrupt the continuity of the coating matrix. This not only easily leads to microcracks but also causes material peeling during wear. It also increases the viscosity of the composite plating solution, affecting the uniformity of the metal ion deposition process and severely impacting the overall performance of the coating.

[0198] Figure 3 and Figure 4 The images show scanning electron microscope (SEM) images of the nickel-tungsten-phosphorus alloy coatings prepared in Example 1 and Comparative Example 6 after wear tests. The comparison shows that, compared to Example 1, the wear scratches on the nickel-tungsten-phosphorus alloy coating prepared in Comparative Example 6 are deeper, and the volumetric wear is greater. This is because the modified silica concentration in Comparative Example 6 is too high, causing the modified silica in the composite plating solution to agglomerate, forming larger micron-sized agglomerates. These agglomerates cannot be fully encapsulated by the coating substrate, resulting in weak adhesion between them and the surrounding coating substrate. During friction, these weakly bonded agglomerates easily detach from the coating substrate and enter the friction interface, becoming third-body abrasive particles and accelerating the wear of surrounding materials.

[0199] The test data from Examples 1, 7, and 8 show that when the current density during the pulse electroplating stage is too low (Comparative Example 7), insufficient electrochemical polarization results in a low nucleation rate and dominant grain growth, leading to coarse grains and a loose structure in the underlying coating, ultimately resulting in poor wear resistance and corrosion resistance. When the current density during the pulse electroplating stage is too high (Comparative Example 8), severe concentration polarization and hydrogen evolution reactions occur, increasing the internal stress of the coating and causing dendrite formation and hydrogen embrittlement. Simultaneously, the excessively fast deposition rate makes it difficult for the modified nanoparticles to be effectively coated by the substrate, resulting in poor interfacial bonding between the nanoparticles and the substrate.

[0200] The test data from Examples 1, 9, and 10 show that when the current density during the DC electroplating stage is too low (Comparative Example 9), the deposition rate of metal ions is too slow, resulting in discontinuous coating growth and a porous, loose coating structure. This structure not only has low hardness and is easily worn, but also provides a large surface area for corrosion, leading to a reduction in the corrosion resistance of the coating. When the current density during the DC electroplating stage is too high (Comparative Example 10), the deposition rate of metal ions is too fast, leading to the accumulation of internal stress in the coating, increasing the risk of brittleness and warping / peeling. At the same time, the excessively fast growth rate also affects the uniform embedding of the modified nanoparticles, which is not conducive to the full realization of their strengthening effect.

[0201] The test data from Examples 1, 11, 12, and 13 show that Comparative Example 11, by omitting modified boron nitride and modified silica, lacks lubrication, friction reduction, and grain refinement strengthening effects, resulting in a significant decrease in the lubricity and corrosion resistance of the coating. Comparative Example 12, by omitting modified alumina and modified boron nitride, leads to substrate softening and accelerated wear. Comparative Example 13, by omitting modified alumina and modified silica, lacks hardening and pore-filling effects, resulting in a loose coating structure that is easily corroded, leading to a significant decrease in the hardness and corrosion resistance of the coating.

[0202] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A pulse-DC electrochemical composite deposition process for nickel-tungsten-phosphorus alloy coatings, characterized in that, include: (I) Modified alumina was obtained by modifying α-alumina with a silane coupling agent; Hexagonal boron nitride nanosheets were modified with hexadecyltrimethylammonium bromide to obtain modified boron nitride; Modified silica was obtained by modifying nano-silica with polyacrylic acid. (II) Nickel salt, tungsten salt, phosphate salt, complexing agent, buffer, primary brightener, secondary brightener, wetting agent, modified alumina, modified boron nitride, modified silicon dioxide and deionized water are mixed, stirred and heated to obtain a composite plating solution; (III) Using the substrate as the cathode, the substrate and the anode plate are immersed in the composite plating solution, and a pulse current is applied to the substrate for pulse electroplating. Then, the current density of the pulse current is continuously and linearly reduced to the target value, and finally, DC electroplating is performed at the target value.

2. The pulse-DC electrochemical composite deposition process for nickel-tungsten-phosphorus alloy coatings according to claim 1, characterized in that, In step (I), the modified alumina is specifically prepared using the following method: α-alumina was dispersed in a silane coupling agent solution and ultrasonically dispersed under water bath heating conditions. Then, it was filtered. The filter cake obtained by filtration was washed and dried to obtain the modified alumina.

3. The pulse-DC electrochemical composite deposition process for nickel-tungsten-phosphorus alloy coatings according to claim 2, characterized in that, The average particle size of the α-alumina is 50~100 nm; The mass fraction of the silane coupling agent in the silane coupling agent solution is 1~2 wt%; The water bath heating temperature is 50~60℃; The ultrasonic power of the ultrasonic dispersion is 400~500W; The ultrasonic dispersion time is 30-50 minutes.

4. The pulse-DC electrochemical composite deposition process for nickel-tungsten-phosphorus alloy coatings according to claim 1, characterized in that, In step (I), the modified boron nitride is prepared using the following method: Hexagonal boron nitride was dispersed in an aqueous solution of hexadecyltrimethylammonium bromide, and simultaneously stirred, heated and sonicated. Then, it was centrifuged, and the precipitate was washed and dried to obtain the modified boron nitride.

5. The pulse-DC electrochemical composite deposition process for nickel-tungsten-phosphorus alloy coatings according to claim 4, characterized in that, The mass fraction of hexadecyltrimethylammonium bromide in the aqueous solution is 0.5~1wt%; The mass ratio of the hexagonal boron nitride to the hexadecyltrimethylammonium bromide in the aqueous solution is 1:(13~15); The stirring speed is 300~500 rpm; The heating temperature is 60~70℃; The ultrasonic power of the ultrasound is 400~500W; The stirring, heating, and ultrasonic treatments are performed for 3-4 hours.

6. The pulse-DC electrochemical composite deposition process for nickel-tungsten-phosphorus alloy coatings according to claim 1, characterized in that, In step (I), the modified silica is specifically prepared using the following method: Nano-silica was dispersed in an aqueous solution of polyacrylic acid, and then subjected to heating and ultrasonic treatment. The mixture was then filtered, and the resulting filter cake was washed and dried to obtain the modified silica.

7. The pulse-DC electrochemical composite deposition process for nickel-tungsten-phosphorus alloy coatings according to claim 6, characterized in that, The average particle size of the nano-silica is 30~50nm; The concentration of polyacrylic acid in the polyacrylic acid aqueous solution is 1~2 g / L; The mass ratio of the nano-silica to the polyacrylic acid in the polyacrylic acid aqueous solution is 1:(1~2); The heating temperature is 40~50℃; The ultrasonic power of the ultrasound is 300~400W; The heating and ultrasonic treatment time is 1-2 hours.

8. The pulse-DC electrochemical composite deposition process for nickel-tungsten-phosphorus alloy coatings according to claim 1, characterized in that, In step (II), the composite plating solution is prepared using the following method: Nickel salt, tungsten salt, complexing agent, and buffer are added sequentially to deionized water. After each component is added, the mixture is stirred until completely dissolved before adding the next component. Alkali solution is added to the resulting mixed solution to adjust its pH to 7-8, followed by the addition of phosphate salt, and the mixture is stirred until completely dissolved. The primary brightener, secondary brightener, wetting agent, modified alumina, modified boron nitride, and modified silicon dioxide are then added, while the mixture is stirred, heated, and ultrasonically treated to obtain the composite plating solution. The stirring speed is 300~400 rpm; The heating temperature is 45~55℃; The ultrasonic power of the ultrasound is 400~500W; The stirring, heating, and ultrasonic treatment processes take 1-2 hours.

9. The pulse-DC electrochemical composite deposition process for nickel-tungsten-phosphorus alloy coatings according to claim 1, characterized in that, In step (II), the concentration of the nickel salt in the composite plating solution is 20~30 g / L; In the composite plating solution, the concentration of the tungsten salt is 50~60 g / L; In the composite plating solution, the concentration of the phosphate salt is 15~25 g / L; In the composite plating solution, the concentration of the complexing agent is 80~100g / L; In the composite plating solution, the concentration of the buffer is 10~20 g / L; In the composite plating solution, the concentration of the primary brightener is 1~3 g / L; In the composite plating solution, the concentration of the secondary brightener is 0.1~0.5 g / L; In the composite plating solution, the concentration of the wetting agent is 0.1~0.2 g / L; In the composite plating solution, the concentration of the modified alumina is 4~5 g / L; In the composite plating solution, the concentration of the modified boron nitride is 1~3 g / L; In the composite plating solution, the concentration of the modified silica is 3~4 g / L.

10. The pulse-DC electrochemical composite deposition process for nickel-tungsten-phosphorus alloy coatings according to claim 1, characterized in that, In step (III), the current density of the pulse current is 4~6 A / dm. 2 ; The pulse frequency of the pulse current is 300~400Hz; The duty cycle of the pulse current is 35-45%; The pulse electroplating time is 10~20 min; After the pulse electroplating is completed, the current density of the pulse current is continuously and linearly reduced to 1-2 A / dm³ within 5-10 minutes. 2 Meanwhile, the duty cycle of the pulse current is continuously and linearly increased to 100% to switch the pulse current to DC current. The DC electroplating time is 40~50 minutes; During the electroplating process, the composite plating solution is stirred and its temperature is maintained at 70~80℃.

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