Ni-W coating with gradient structure on surface of pipe and preparation method of Ni-W coating

Abstract

The invention discloses a Ni-W coating with a gradient structure on the surface of a pipe and a preparation method of the Ni-W coating, and belongs to the technical field of metal surface modification. According to the Ni-W coating with the gradient structure, the bottom layer is of a nanocrystalline crystalline structure, and the surface layer is of an amorphous structure; according to the gradient structure of the Ni-W coating, the tungsten content is gradually increased in the growth direction of the coating, and continuous gradient distribution is formed. In the plating process, the concentration of tungsten ions in the plating solution is controlled by regulating and controlling the current or the potential, the structure transformation of the Ni-W alloy plating layer from a nanocrystalline structure to an amorphous structure is achieved, the gradient Ni-W plating layer with the nanocrystalline crystalline structure at the bottom layer and the amorphous structure at the surface layer is obtained, the metal activity of carbon steel is enhanced, and the corrosion resistance of the Ni-W alloy plating layer is improved. And the plating layer gives consideration to the binding force, corrosion resistance and wear resistance. According to the method, the technical problems that the binding force between a carbon steel substrate and a plating layer interface is weak, and the Ni-W plating layer deposition speed is low due to the fact that the carbon steel metal activity is low are solved.

Description

Technical Field

[0001] This invention belongs to the field of metal surface modification technology, specifically relating to a gradient structure Ni-W coating on the surface of a pipe and its preparation method. Background Technology

[0002] Pipeline erosion is a common type of corrosion in the oil and gas industry. In my country's shale gas development, large-scale horizontal well fracturing is one of the main technologies for efficient shale gas development, but fracturing the reservoir can easily lead to sand production. The "strong injection and strong extraction" operation mode of gas storage facilities also makes the reservoir prone to sand production during peak-shaving gas production. Once the pipeline transport medium contains sand, it can easily cause erosion of the inner wall of the pipe, leading to failure. Currently, there are three main technical countermeasures for pipe erosion caused by sand production. One is to increase the hardness and elastic modulus of the material, but high hardness reduces the plasticity of the material and increases its susceptibility to sulfide stress cracking; while the elastic modulus is related to the alloy composition of the material and is difficult to improve through cold working or heat treatment. Secondly, surface modification of materials can be achieved through coatings, cermet coatings, and polymer materials. However, cermet coatings are limited in use due to their high cost, poor impact resistance, and difficult application. While polymer surface modification can achieve better corrosion resistance and features low strength and good toughness, it suffers from poor resistance to sharp particles and poor resistance to sand and gravel erosion. Regarding coatings, research has shown that metal coatings can effectively improve the wear resistance and corrosion resistance of material surfaces. Thirdly, adjusting the production process to reduce sand volume and flow rate can improve the erosion resistance of materials. For example, using screens offers advantages such as simple process, low cost, and high efficiency; however, screens are prone to clogging, negatively impacting production. Comparing these three technical solutions, metal coatings are an effective means of solving pipe erosion caused by sand discharge, especially Ni-W metal coatings, which combine the wear resistance of tungsten-based metals with the corrosion resistance of nickel-based metals, and are environmentally friendly. This is an effective way to simultaneously solve the erosion and corrosion problems of oil and gas pipelines. Electrodeposited Ni-W coatings are primarily achieved by controlling the grain size of Ni-W within the nanocrystalline region. When an amorphous Ni-W coating is obtained, its hardness can reach 550-1100 Hv, and its corrosion resistance is more than 100 times that of ordinary materials. However, for pipes primarily made of carbon steel, the low activity of carbon steel results in weak affinity for anions in the plating bath during direct electroplating. This necessitates the addition of a large amount of reducing agent to the plating bath, increasing resistivity. Consequently, the Ni-W coating deposition rate is slow, requiring high energy density and a long time to form a Ni-W amorphous coating of a certain thickness. Furthermore, the amorphous Ni-W coating differs significantly from the carbon steel substrate in stiffness and crystallographic properties, resulting in weak adhesion between the coating and the metal substrate. During service, the mismatch in performance between the substrate and the coating makes them prone to cracking and peeling. Designing a method for preparing Ni-W amorphous coatings that can improve the activity of carbon steel substrates, be efficient and rapid, and reduce the stiffness difference between carbon steel substrates and amorphous coatings is currently a technical bottleneck in the application of Ni-W metal coatings. This method is of great significance for ensuring the safety of pipes operating under erosion and corrosion conditions.

[0003] Currently, there are three main technical means to improve the adhesion of metal coatings: First, maintain the crystalline structure of the coating. Beijing University of Science and Technology used electrodeposition to prepare Ni-W crystalline coatings, and the 32178 Unit of the Chinese People's Liberation Army modified the heat treatment process to crystallize the Ni-W and Ni-W-SiC coating structures, resulting in good adhesion, but the coatings were brittle and had poor wear resistance. Second, change the coating preparation process. Shenyang Aerospace University used ultrasonic-assisted chemical plating to prepare Ni-WP coatings. The introduction of ultrasound improved the hardness and wear resistance of the coating, but further reduced the bonding strength between the coating and the substrate. Henan University of Science and Technology improved the adhesion between the high-speed steel substrate and the Ni-WP coating to 32.3 N by adjusting the surface activation treatment process. Third, prepare multi-layered coatings. Chinese patent CN111926358A discloses an electrodeposition method for preparing a Ni-Co-B-Sc quaternary gradient coating that combines the composite strengthening properties of gradient structure and alloying elements. While this improves the wear and corrosion resistance of the coating, it does not enhance adhesion. Chinese patent CN117888157A discloses a Cu / nanocrystalline / amorphous multilayer Ni-W coating and its preparation method. This involves depositing Cu layers → crystalline Ni-W layers → transitional Ni-W layers → amorphous Ni-W layers on the surface of a pipe, forming a multilayer structure. The flexibility of the Cu layers alleviates the interfacial stress between the carbon steel and the Ni-W coating. However, the multilayer coating process is complex and costly. These techniques demonstrate that while crystalline Ni-W coatings exhibit high adhesion to the substrate, their toughness and wear resistance are poor. Multilayer structures are inefficient and costly to prepare. Furthermore, techniques to improve adhesion by modifying the process are unstable and may even further reduce adhesion. Summary of the Invention

[0004] In order to overcome the shortcomings of the prior art, the present invention aims to provide a gradient structure Ni-W coating on the surface of a pipe and its preparation method, which aims to overcome the technical problems of weak interfacial bonding between the carbon steel substrate and the coating and slow deposition rate of the Ni-W coating due to the low metal activity of carbon steel.

[0005] To achieve the above objectives, the present invention employs the following technical solution: This invention discloses a gradient structure Ni-W coating on the surface of a pipe, wherein the Ni-W coating has a bottom layer of nanocrystalline crystalline structure and a top layer of amorphous gradient Ni-W coating.

[0006] Furthermore, the gradient structure of the Ni-W coating is characterized by a gradual increase in tungsten content along the coating growth direction, forming a continuous gradient distribution.

[0007] Furthermore, the thickness of the gradient structure Ni-W coating is 55-65 micrometers.

[0008] More preferably, the thickness of the gradient structure Ni-W coating is 50 micrometers.

[0009] This invention also discloses a gradient structure Ni-W coating on the surface of a pipe and its preparation method, comprising the following steps: S1: Using carbon steel for oil and gas pipelines as a base, the carbon steel substrate is subjected to surface activation treatment by physical and chemical methods to improve the surface metal activity.

[0010] In the electrodeposition of Ni-W coatings, controlling the current or potential can alter the nucleation and growth of crystal particles. When the single crystal size increases to 10-100 nm, increasing the potential does not affect the final crystal particle size. The Ni-W alloy exhibits a nanocrystalline structure, and the size of the underlying nanocrystalline structure also affects the size of the surface layer. Performance. If the nanocrystal size is too large, the continuity of the surface amorphous structure will be affected, thereby reducing corrosion and wear resistance. Therefore, controlling the nanocrystal structure within an appropriate size range helps to maintain the integrity and performance of the surface amorphous structure.

[0011] S2: The activated carbon steel substrate is placed in the plating solution and electroplated to obtain a gradient structure Ni-W coating.

[0012] With increasing W content, the Ni-W coating gradually forms a nanocrystalline to amorphous structure. During the plating process, the concentration of tungsten ions in the plating bath is controlled by adjusting the current density and bath temperature, achieving the structural transformation of the Ni-W alloy coating from nanocrystalline to amorphous. This results in a gradient Ni-W coating with a nanocrystalline crystalline bottom layer (ensuring adhesion between the coating and the substrate) and an amorphous surface layer (ensuring corrosion and wear resistance). This is a feasible method for preparing Ni-W coatings that balance adhesion and corrosion / wear resistance.

[0013] Furthermore, in S1, the carbon steel substrate surface activation process is a physical method of plasma and a chemical method of activation liquid. After plasma activation, it is ultrasonically cleaned with acetone and activated with hydrochloric acid with a volume fraction of 45-55% or ultrasonically cleaned with alcohol and activated with hydrofluoric acid with a volume fraction of 30-40%.

[0014] Furthermore, the physical activation treatment takes 5 to 10 minutes.

[0015] More preferably, the physical activation treatment time is 5 minutes.

[0016] Furthermore, the working gas of the atmospheric pressure plasma device is a mixture of one of Ar, He and N2 with H2, wherein the volume of H2 is 40% to 50% of the volume of the mixture.

[0017] More preferably, activation is performed using hydrochloric acid with a volume fraction of 50%.

[0018] Furthermore, the chemical activation treatment takes 3-8 minutes.

[0019] More preferably, the chemical activation treatment time is 4 minutes.

[0020] Furthermore, in S2, the plating solution comprises: 0.1~0.05 mol of nickel sulfate, 0.3~0.8 mol of ammonium chloride, 0.1~0.2 mol of sodium bromide, and a mixed complexing agent. The mixed complexing agent comprises: trisodium citrate, triethanolamine, and glycine, with a concentration ratio of (1.2~1.7):(0.8~1.2):(0.8~1.2).

[0021] More preferably, the concentration ratio of trisodium citrate, triethanolamine, and glycine is 1.5:1:1.

[0022] Furthermore, in S2, the electroplating conditions include: a duty cycle of 90-95%, a frequency of 45-50Hz, a stirring speed of 250-350 rpm, and the plating solution being in an ultrasonic environment.

[0023] More preferably, in S2, the electroplating conditions include: a duty cycle of 95%, a frequency of 48 Hz, a stirring speed of 300 rpm, and the plating solution being in an ultrasonic environment.

[0024] Furthermore, in S2, the formation process of the gradient structure Ni-W coating involves computer-controlled current density increasing by 0.1 A / cm² every 10 minutes. 2 The rate of change ranged from 0.08 to 0.12 A / cm. 2 The gradient was increased to 0.3~0.7 A / cm. 2 The temperature of the plating solution is controlled to increase gradually from 35~45℃ to 55~65℃ at a rate of 5℃ every 10 minutes.

[0025] More preferably, in S2, the process for forming the gradient structure Ni-W coating includes: using computer-controlled current density to increase by 0.1 A / cm² every 10 minutes. 2 The rate of change, from 0.1 A / cm 2 The gradient was increased to 0.5 A / cm. 2 The temperature of the plating solution is controlled by a computer and increases gradually from 40°C to 60°C at a rate of 5°C every 10 minutes.

[0026] Furthermore, in S2, 20-30 ml of sodium tungstate is injected into the plating solution every 4-8 minutes, and 0.5 mol-1.2 mol of ammonium chloride is injected into the plating solution every 5-15 minutes; throughout the entire electrodeposition process, 250-350 ml of sodium tungstate is injected at a concentration of 0.8 mol / L to 1 mol / L.

[0027] More preferably, in S2, 25 ml of sodium tungstate is injected into the plating solution every 5 minutes through a dropper during the entire electrodeposition process, and 0.1 mol of ammonium chloride is injected into the plating solution every 10 minutes.

[0028] Furthermore, 250-350 ml of sodium tungstate with a concentration of 0.8-1 mol / L is injected throughout the electrodeposition process.

[0029] More preferably, 300 ml of sodium tungstate with a concentration of 0.9 mol / L is injected throughout the electrodeposition process.

[0030] Furthermore, in S2, after electrodeposition for 40-60 minutes, a gradient Ni-W coating with a thickness of 55-65 micrometers is obtained.

[0031] More preferably, in S2, after electrodeposition for 60 minutes, the thickness of the gradient structure Ni-W coating reaches 50 micrometers.

[0032] Compared with the prior art, the present invention has the following beneficial effects: This invention discloses a gradient structure Ni-W coating for pipe surfaces. The bottom layer is a nanocrystalline structure, and since both the nanocrystalline structure and the carbon steel substrate are crystalline structures, the bonding between the two is easier and the bonding effect is better. The surface layer is an amorphous structure. The amorphous structure has no clear grain boundaries, making it difficult for corrosive liquids to corrode through the grain boundaries, thus giving the coating better corrosion resistance. The amorphous structure also has higher hardness, giving the coating better corrosion resistance and wear resistance.

[0033] Furthermore, in the nanocrystalline-amorphous gradient structure Ni-W coating on the pipe surface of the present invention, the W atom concentration exhibits a gradient distribution from low to high from the bottom layer to the surface layer. This ensures the excellent wear and corrosion resistance of the surface amorphous structure while preventing high residual stress defects caused by excessive lattice distortion due to excessive W atom concentration within the coating. In addition, because the bottom layer of the nanocrystalline-amorphous gradient structure Ni-W coating has a nanocrystalline structure, it has good crystallographic compatibility with the metal substrate, improving the coating adhesion and effectively enhancing the overall performance of the coating.

[0034] Furthermore, the gradient structure Ni-W coating of the present invention has a thickness of 55-65 micrometers, which provides a sufficient protective layer for the coating to prevent the substrate from being corroded and worn.

[0035] This invention also discloses a method for preparing a gradient Ni-W coating on the surface of a pipe. First, surface activation treatment using physical and chemical methods improves the surface activity of the carbon steel substrate, increases the affinity with anions in the plating solution, accelerates the deposition rate of the Ni-W coating, and also results in a coating with a certain thickness. Second, the activated carbon steel substrate is placed in the plating solution, and electroplating is performed to obtain a gradient Ni-W coating with a nanocrystalline structure as the bottom layer and an amorphous structure as the surface layer. This strengthens the adhesion of the coating and prevents cracking and peeling of the substrate and coating during service.

[0036] Furthermore, the preparation method of this invention employs a physical method of plasma and a chemical activation method using hydrochloric acid. On the one hand, the physical method of plasma can remove contaminants and oxide layers from the carbon steel surface, while increasing surface roughness, which is beneficial for the adhesion of subsequent electroplating layers. On the other hand, the chemical activation solution (such as 45-55% hydrochloric acid and 30-40% hydrofluoric acid by volume) further reacts with the carbon steel surface to form active sites, improving metal activity and facilitating the deposition of Ni-W alloys during electroplating. Acetone ultrasonic cleaning can remove residues and oil stains after plasma treatment, ensuring surface cleanliness. In summary, the activation treatment using both physical and chemical methods is beneficial for improving the adhesion between the coating and the substrate. This helps ensure the quality and stability of the coating.

[0037] Furthermore, the preparation method of the present invention employs computer-controlled gradient distribution of current density and plating temperature over time to control the deposition efficiency of tungsten ions from low to high, thereby forming a gradient-structured Ni-W coating. This process is simple, effective, and easy to control.

[0038] Furthermore, the preparation method of the present invention regulates the activity of the plating bath and the co-deposition efficiency of nickel and tungsten ions by employing a mixed complexing agent. Triethanolamine improves the cathode current efficiency, trisodium citrate serves as a complexing agent for the co-deposition of nickel and tungsten ions, and glycine increases the conductivity of the plating bath. Ammonium chloride is volatile, and its batch addition during electrodeposition ensures the pH value of the plating bath and improves current efficiency.

[0039] Furthermore, the preparation method of the present invention, by using a dropper to add sodium tungstate in batches, can not only provide a precursor for W, but also control the concentration of tungsten ions in the plating solution, so that the concentration of tungsten ions increases in a gradient with the electroplating time. This injection method is simple and easy to implement, and can accurately control the tungsten content in the coating, while adjusting the composition and performance of the electroplating solution. Attached Figure Description

[0040] Figure 1 This is a cross-sectional view of the coating in Embodiment 1 of the present invention; Figure 2 This is a tungsten element concentration distribution diagram of the coating cross section in Embodiment 1 of the present invention; Figure 3 This is a comparison of the polarization curves of the Ni-W gradient coating and the crystalline coating prepared in Example 1 of this invention; Figure 4 This is a comparison of the friction coefficients of the Ni-W gradient coating and the crystalline coating prepared in Example 1 of this invention; Figure 5 This is a comparison of the deposition rates of the Ni-W gradient coating and the crystalline coating prepared in Example 1 of this invention. Detailed Implementation

[0041] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0042] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0043] The present invention will now be described in further detail with reference to the accompanying drawings: Example 1 S1: Carbon steel surface activation treatment.

[0044] The carbon steel, after surface grease removal, is first subjected to physical activation treatment using an atmospheric pressure plasma device for 5 minutes. The working gas of the atmospheric pressure plasma device is a mixture of Ar and H2, wherein the volume of H2 is 40% of the volume of the mixture. The physically activated carbon steel is then further activated chemically by ultrasonic cleaning with acetone and activation with 50% hydrochloric acid for 4 minutes.

[0045] S2: Electroplated gradient structure Ni-W coating.

[0046] The activated carbon steel was placed in an electroplating solution for Ni-W plating. The electroplating conditions were: duty cycle 95%, frequency 48Hz, stirring speed 300 rpm, and a computer-controlled increment of 0.1 A / cm² every 10 minutes. 2 The rate of change, controlling the current density from 0.08 A / cm 2 The gradient was increased to 0.7 A / cm. 2 The temperature of the plating solution was controlled to increase from 35°C to 65°C in a gradient of 5°C every 10 minutes. The plating solution consists of: 0.08 mol nickel sulfate, 0.5 mol ammonium chloride, 0.1 mol sodium bromide, 0.6 mol trisodium citrate, 0.4 mol triethanolamine, and 0.4 mol glycine.

[0047] During electroplating, 300 ml of sodium tungstate with a concentration of 0.9 mol was injected into the plating solution every 5 minutes using a dropper, and 0.5 mol of ammonium chloride was added to the plating solution every 10 minutes.

[0048] Throughout the electroplating process, a magnetic stirrer is used to keep the plating solution mechanically agitated, and the electrodeposition process is conducted in an ultrasonic environment. After 60 minutes of electroplating, a Ni-W coating with a nanocrystalline-amorphous gradient structure and a thickness of approximately 50 μm can be obtained.

[0049] Comparative example: S1: Carbon steel surface activation treatment.

[0050] The carbon steel, after surface grease removal, is first subjected to physical activation treatment using an atmospheric pressure plasma device for 5 minutes. The working gas of the atmospheric pressure plasma device is a mixture of Ar and H2, wherein the volume of H2 is 40% of the volume of the mixture. The physically activated carbon steel is then further activated chemically by ultrasonic cleaning with acetone and activation with 50% hydrochloric acid for 4 minutes.

[0051] S2: Electroplated crystalline Ni-W coating.

[0052] The activated carbon steel was placed in an electroplating solution to perform Ni-W plating. The electroplating conditions were: duty cycle 95%, frequency 48Hz, stirring speed 300 rpm, and current density 0.5 A / cm². 2 The plating solution temperature is 60℃; The plating solution consists of: 0.08 mol nickel sulfate, 0.5 mol ammonium chloride, 0.1 mol sodium bromide, 0.6 mol trisodium citrate, 0.4 mol triethanolamine, 0.4 mol glycine, and 0.9 mol sodium tungstate.

[0053] Throughout the electroplating process, a magnetic stirrer is used to keep the plating solution mechanically agitated, and the electrodeposition process is conducted in an ultrasonic environment. A Ni-W coating with a crystalline structure can be obtained after 60 minutes of electroplating.

[0054] Figure 1 The figure shows a cross-sectional view of the Ni-W amorphous coating on the pipe surface in Example 1. It can be seen from the figure that the Ni-W coating thickness is about 50 μm, and the Ni-W coating has good adhesion to the substrate and no obvious defects such as pores.

[0055] Figure 2 The figure shows the concentration distribution of tungsten from the substrate to the surface of the Ni-W amorphous coating on the pipe surface in Example 1. As can be seen from the figure, the concentration of tungsten atoms in the coating is distributed in a gradient from low to high, thus ensuring the nanocrystalline-amorphous gradient distribution in the coating.

[0056] Figure 3 This is a comparison of the polarization curves of the Ni-W gradient coating prepared in Example 1 and the crystalline coating prepared in the comparative example. It can be seen from the figure that the Ni-W gradient coating has higher polarization current and electrode potential, and better corrosion resistance.

[0057] Figure 4 This is a comparison chart of the friction coefficients of the Ni-W gradient coating prepared in Example 1 and the crystalline coating prepared in the comparative example. It can be seen from the chart that the Ni-W gradient coating has a lower and more stable friction coefficient and better wear resistance.

[0058] Figure 5 This is a comparison graph of the deposition rates of the Ni-W gradient coating prepared in Example 1 and the crystalline coating prepared in the comparative example. It can be seen from the graph that the Ni-W gradient coating has a higher deposition rate.

[0059] Example 2 S1: Carbon steel surface activation treatment.

[0060] The carbon steel, after surface grease removal, is first subjected to physical activation treatment using an atmospheric pressure plasma device for 10 minutes. The working gas of the atmospheric pressure plasma device is a mixture of He and H2, wherein the volume of H2 is 45% of the volume of the mixture. The physically activated carbon steel is then further activated chemically by ultrasonic cleaning with acetone and activation with 45% hydrochloric acid for 3 minutes.

[0061] S2: Electroplated gradient structure Ni-W coating.

[0062] The activated carbon steel was placed in an electroplating solution for Ni-W plating. The electroplating conditions were: duty cycle 90%, frequency 45Hz, stirring speed 250 rpm, and the agitation was increased by 0.1 A / cm² every 10 minutes using a computer. 2The rate of change, controlling the current density from 0.12 A / cm 2 The gradient was increased to 0.3 A / cm. 2 The temperature of the plating solution was controlled to increase gradually from 45°C to 55°C at a rate of 5°C every 10 minutes. The plating solution consists of: 0.05 mol nickel sulfate, 0.3 mol ammonium chloride, 0.1 mol sodium bromide, 0.6 mol trisodium citrate, 0.4 mol triethanolamine, and 0.4 mol glycine.

[0063] During electroplating, 300 ml of sodium tungstate with a concentration of 0.9 mol was injected into the plating solution every 5 minutes using a dropper, with 25 ml added every 5 minutes. Additionally, 1 mol of ammonium chloride was added to the plating solution every 5 minutes.

[0064] Throughout the electroplating process, a magnetic stirrer was used to maintain mechanical agitation of the plating solution, and the electrodeposition process was conducted in an ultrasonic environment. After 40 minutes of electroplating, a Ni-W coating with a nanocrystalline-amorphous gradient structure was obtained.

[0065] Example 3 S1: Carbon steel surface activation treatment.

[0066] The carbon steel, after surface grease removal, is first subjected to physical activation treatment using an atmospheric pressure plasma device for 7 minutes. The working gas of the atmospheric pressure plasma device is a mixture of N2 and H2, wherein the volume of H2 is 50% of the volume of the mixture. The physically activated carbon steel is then further activated chemically by ultrasonic cleaning with acetone and activation with 55% hydrochloric acid for 8 minutes.

[0067] S2: Electroplated gradient structure Ni-W coating.

[0068] The activated carbon steel was placed in an electroplating solution for Ni-W plating. The electroplating conditions were: duty cycle 93%, frequency 50Hz, stirring speed 350 rpm, and a computer-controlled increment of 0.1 A / cm² every 10 minutes. 2 The rate of change, controlling the current density from 0.1 A / cm 2 The gradient was increased to 0.5 A / cm. 2 The temperature of the plating solution was controlled to increase from 40°C to 60°C at a rate of 5°C every 10 minutes. The plating solution consists of: 0.1 mol nickel sulfate, 0.8 mol ammonium chloride, 0.2 mol sodium bromide, 1.7 mol trisodium citrate, 1.2 mol triethanolamine, and 1.2 mol glycine.

[0069] During electroplating, 350 ml of sodium tungstate with a concentration of 1 mol was injected into the plating solution every 8 minutes using a dropper, and 1.2 mol of ammonium chloride was added to the plating solution every 15 minutes.

[0070] Throughout the electroplating process, a magnetic stirrer was used to maintain mechanical agitation of the plating solution, and the electrodeposition process was conducted in an ultrasonic environment. After 50 minutes of electroplating, a Ni-W coating with a nanocrystalline-amorphous gradient structure was obtained.

[0071] Example 4 S1: Carbon steel surface activation treatment.

[0072] The carbon steel, after surface grease removal, is first subjected to physical activation treatment using an atmospheric pressure plasma device for 7 minutes. The working gas of the atmospheric pressure plasma device is a mixture of N2 and H2, wherein the volume of H2 is 50% of the volume of the mixture. The physically activated carbon steel is then further activated chemically by ultrasonic cleaning with alcohol and activation with 30% hydrofluoric acid by volume. S2: Electroplated gradient structure Ni-W coating.

[0073] The activated carbon steel was placed in an electroplating solution for Ni-W plating. The electroplating conditions were: duty cycle 93%, frequency 50Hz, stirring speed 350 rpm, and a computer-controlled increment of 0.1 A / cm² every 10 minutes. 2 The rate of change, controlling the current density from 0.1 A / cm 2 The gradient was increased to 0.5 A / cm. 2 The temperature of the plating solution was controlled to increase from 40°C to 60°C at a rate of 5°C every 10 minutes. The plating solution consists of: 0.1 mol nickel sulfate, 0.8 mol ammonium chloride, 0.2 mol sodium bromide, 1.7 mol trisodium citrate, 1.2 mol triethanolamine, and 1.2 mol glycine. During electroplating, 350 ml of sodium tungstate (1 mol concentration) is added to the plating solution every 8 minutes using a dropper, and 1.2 mol ammonium chloride is added to the plating solution every 15 minutes. Throughout the electroplating process, a magnetic stirrer was used to maintain mechanical agitation of the plating solution, and the electrodeposition process was conducted in an ultrasonic environment. After 50 minutes of electroplating, a Ni-W coating with a nanocrystalline-amorphous gradient structure was obtained.

[0074] Example 5 S1: Carbon steel surface activation treatment.

[0075] The carbon steel, after surface grease removal, is first subjected to physical activation treatment using an atmospheric pressure plasma device for 7 minutes. The working gas of the atmospheric pressure plasma device is a mixture of N2 and H2, wherein the volume of H2 is 50% of the volume of the mixture. The physically activated carbon steel is then further activated chemically by ultrasonic cleaning with alcohol and activation with 35% hydrofluoric acid by volume. S2: Electroplated gradient structure Ni-W coating.

[0076] The activated carbon steel was placed in an electroplating solution for Ni-W plating. The electroplating conditions were: duty cycle 93%, frequency 50Hz, stirring speed 350 rpm, and a computer-controlled increment of 0.1 A / cm² every 10 minutes. 2 The rate of change, controlling the current density from 0.1 A / cm 2 The gradient was increased to 0.5 A / cm. 2 The temperature of the plating solution was controlled to increase from 40°C to 60°C at a rate of 5°C every 10 minutes. The plating solution consists of: 0.1 mol nickel sulfate, 0.8 mol ammonium chloride, 0.2 mol sodium bromide, 1.7 mol trisodium citrate, 1.2 mol triethanolamine, and 1.2 mol glycine. During electroplating, 350 ml of sodium tungstate (1 mol concentration) is added to the plating solution every 8 minutes using a dropper, and 1.2 mol ammonium chloride is added to the plating solution every 15 minutes. Throughout the electroplating process, a magnetic stirrer was used to maintain mechanical agitation of the plating solution, and the electrodeposition process was conducted in an ultrasonic environment. After 50 minutes of electroplating, a Ni-W coating with a nanocrystalline-amorphous gradient structure was obtained.

[0077] Example 6 S1: Carbon steel surface activation treatment.

[0078] The carbon steel, after surface grease removal, is first subjected to physical activation treatment using an atmospheric pressure plasma device for 7 minutes. The working gas of the atmospheric pressure plasma device is a mixture of N2 and H2, wherein the volume of H2 is 50% of the volume of the mixture. The physically activated carbon steel is then further activated chemically by ultrasonic cleaning with alcohol and activation with 40% hydrofluoric acid by volume. S2: Electroplated gradient structure Ni-W coating.

[0079] The activated carbon steel was placed in an electroplating solution for Ni-W plating. The electroplating conditions were: duty cycle 93%, frequency 50Hz, stirring speed 350 rpm, and a computer-controlled increment of 0.1 A / cm² every 10 minutes. 2 The rate of change, controlling the current density from 0.1 A / cm 2The gradient was increased to 0.5 A / cm. 2 The temperature of the plating solution was controlled to increase from 40°C to 60°C at a rate of 5°C every 10 minutes. The plating solution consists of: 0.1 mol nickel sulfate, 0.8 mol ammonium chloride, 0.2 mol sodium bromide, 1.7 mol trisodium citrate, 1.2 mol triethanolamine, and 1.2 mol glycine. During electroplating, 350 ml of sodium tungstate (1 mol concentration) is added to the plating solution every 8 minutes using a dropper, and 1.2 mol ammonium chloride is added to the plating solution every 15 minutes. Throughout the electroplating process, a magnetic stirrer was used to maintain mechanical agitation of the plating solution, and the electrodeposition process was conducted in an ultrasonic environment. After 50 minutes of electroplating, a Ni-W coating with a nanocrystalline-amorphous gradient structure was obtained.

[0080] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A gradient Ni-W coating on the surface of a pipe, characterized in that, The Ni-W coating has a bottom layer of nanocrystalline crystalline structure and a surface layer of amorphous gradient Ni-W coating.

2. The gradient structure Ni-W coating on the surface of a pipe according to claim 1, characterized in that, The gradient structure of Ni-W coatings is characterized by a gradual increase in tungsten content along the coating growth direction, forming a continuous gradient distribution.

3. The gradient structure Ni-W coating on the surface of a pipe according to claim 1, characterized in that, The thickness of the gradient structure Ni-W coating is 55-65 micrometers.

4. A method for preparing a gradient Ni-W coating on a pipe surface according to any one of claims 1 to 3, characterized in that, Includes the following steps: S1: Surface activation treatment of carbon steel substrate by physical and chemical methods; S2: The activated carbon steel substrate is placed in the plating solution and electroplated to obtain a gradient structure Ni-W coating.

5. The method for preparing a gradient Ni-W coating on a pipe surface according to claim 4, characterized in that, In S1, the physical surface activation treatment includes: physical plasma; the chemical surface activation treatment includes: ultrasonic cleaning with acetone and activation with 45-55% hydrochloric acid by volume or ultrasonic cleaning with alcohol and activation with 30-40% hydrofluoric acid by volume.

6. The method for preparing a gradient Ni-W coating on a pipe surface according to claim 4, characterized in that, In S2, the gradient structure Ni-W coating is formed by controlling the current density to increase by 0.1 A / cm² every 10 minutes. 2 The rate of change ranged from 0.08 to 0.12 A / cm. 2 The gradient was increased to 0.3~0.7 A / cm. 2 The temperature of the plating solution is controlled to increase gradually from 35~45℃ to 55~65℃ at a rate of 5℃ every 10 minutes.

7. The method for preparing a gradient Ni-W coating on a pipe surface according to claim 4, characterized in that, In S2, the plating solution includes: 0.05~0.1 mol nickel sulfate, 0.3~0.8 mol ammonium chloride, 0.1~0.2 mol sodium bromide, and a mixed complexing agent. The mixed complexing agent consists of: trisodium citrate, triethanolamine, and glycine, with a concentration ratio of (1.2~1.7):(0.8~1.2):(0.8~1.2).

8. The method for preparing a gradient Ni-W coating on a pipe surface according to claim 4, characterized in that, In S2, 20-30 ml of sodium tungstate is injected into the plating solution every 4-8 minutes, and 0.5 mol-1.2 mol of ammonium chloride is injected into the plating solution every 5-15 minutes.

9. A method for preparing a gradient Ni-W coating on a pipe surface according to claim 8, characterized in that, The concentration of sodium tungstate is 0.8 mol / L ~ 1 mol / L.

10. The method for preparing a gradient Ni-W coating on a pipe surface according to claim 4, characterized in that, In S2, the electroplating conditions include: a duty cycle of 90-95%, a frequency of 45-50Hz, a stirring speed of 250-350 rpm, an electroplating time of 40-60 minutes, and the plating solution being in an ultrasonic environment.

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