Tungsten alloy coating, preparation method thereof and perforated liner tube

Abstract

The invention relates to the technical field of alloy plating layers, in particular to a tungsten alloy plating layer and a preparation method thereof and a liner tube with holes, the tungsten alloy plating layer is a tungsten-nickel alloy plating layer, the plating layer is compact and free of defects, the thickness of the plating layer is 40-100 microns, and the Vickers hardness of the plating layer is not lower than 900 HV1. The preparation method comprises the following steps: forming a stable electroplating solution by using a special composite complexing agent, conductive salt, a buffer agent and an additive as auxiliary materials, and electroplating under matched pulse parameters and mechanical stirring through plasma cleaning in combination with a profiling anode and pulse electroplating technology. According to the method, the high-hardness tungsten alloy coating with uniform thickness and excellent performance can be deposited on a workpiece with a complex shape, particularly the inner wall and the outer wall of a liner tube with holes and the inner surfaces of all the holes, and the technical problem of uniformity of the coating on the surface of a deep hole and a complex structural part is solved.

Description

Technical Field

[0001] This invention relates to the field of alloy coating technology, specifically to a tungsten alloy coating and its preparation method, and a perforated liner. Background Technology

[0002] Tungsten-nickel alloy coatings, due to their high hardness, corrosion resistance, and high-temperature stability, have broad application prospects in aerospace, petrochemical, and precision mold industries. In particular, applying a hard tungsten alloy coating to perforated pipe liner in the petroleum industry can significantly improve its resistance to sand erosion and scouring, thereby extending its service life.

[0003] Currently, electrodeposition technology is the main method for preparing tungsten-nickel alloy coatings. However, existing electroplating processes still face many technical challenges in achieving high-quality coatings, especially when applied to workpieces with complex structures. Conventional electroplating techniques, when processing workpieces with deep holes, blind holes, or complex internal cavities, such as perforated liner tubes, are prone to uneven coating thickness at the edges of holes and deep within the inner walls due to uneven electric field distribution and limited mass transport. The edges of holes often have excessively thick coatings due to edge effects, even producing burrs, while the interior of holes and the center of deep holes have thin coatings due to weak electric fields, failing to provide effective protection and severely affecting the overall performance and service life of the workpiece. Traditional nickel-tungsten electroplating systems, such as those using nickel chloride or nickel sulfate as the main salt, result in coatings with high internal stress. When depositing thicker coatings, such as those exceeding 40 μm, microcracks or even peeling are easily generated, leading to insufficient coating density and defects such as pores and inclusions, reducing its corrosion resistance and mechanical strength. Tungsten, as a metal that is difficult to electrodeposit alone in aqueous solutions, relies heavily on the complexing agent system in the electroplating solution for its co-deposition with nickel. Existing technologies use a single citrate complexing system, which lacks stability or efficiency, potentially leading to spontaneous decomposition of the electroplating solution, poor uniform plating ability, and an inability to obtain alloy coatings with high tungsten content and stable performance. Finally, the process uses DC electroplating, which has poor coverage for deep holes and grooves in complex workpieces. Although pulse electroplating technology has been proven to help improve coating quality, it is still difficult to obtain high-performance coatings with uniform thickness on various surfaces of three-dimensional complex structures without combining them with optimized electroplating solution formulations and special tooling, such as contour anodes.

[0004] CN102337569B discloses a method for preparing a cobalt-tungsten nano-alloy coating. The method uses platinum titanium or a cobalt-tungsten alloy as the anode and the workpiece to be plated as the cathode. Electroplating is performed using a mixed solution of cobalt sulfate (100-200 g / L), sodium tungstate (10-70 g / L), sodium sulfate (50-150 g / L), boric acid (15-50 g / L), sodium saccharin (1-4 g / L), surfactant (0.01-0.1 g / L), and complexing agent (40-120 g / L). The alloy coating has a nanocrystalline structure with a grain size of 20-40 nm; the tungsten content in the nano-alloy coating is 13.2-25.1 wt%. The advantages of this invention are: the coating preparation method is simple, and it not only possesses the hardness of hard chrome plating but also has better wear resistance and friction reduction properties than hard chrome plating. It is suitable for parts requiring high hardness, high wear resistance, and a low coefficient of friction, and has wide applications.

[0005] CN105543910B discloses a nickel-tungsten alloy composite coating, the preparation method of which includes the following steps: (1) Preparation of electroplating solution: weigh trisodium citrate, NH4Cl, NaBr, Na2WO4·2H2O, NiSO4·6H2O, and β-cyclodextrin and add them to deionized water in sequence, and mix well; (2) polish the substrate 45# carbon steel with 400, 800, and 1200 grit sandpaper in sequence, put the polished steel sheet into 1 mol / L sulfuric acid for activation, and then put it into the electroplating solution for electroplating; (3) The electroplating process adopts pulse electrodeposition method with a deposition current density of 5A / dm. 2 The duty cycle was 0.8, and the deposition time was 1 hour. β-cyclodextrin was used as a grain refiner for electroplated nickel-tungsten alloys. During the deposition process, the grain size of the nickel-tungsten alloy was significantly reduced. Moreover, this substance is very stable during the preparation process and does not affect the performance of the product, while also making the coating more corrosion resistant.

[0006] In summary, current methods for preparing tungsten alloy coatings do not address key issues such as the stability of workpieces with complex shapes and the plating solution. Therefore, there is an urgent need for a novel tungsten alloy coating and its preparation method that can effectively solve the problems of high internal stress and poor thickness uniformity in complex geometries without sacrificing core properties such as coating hardness, thereby meeting the high-standard application requirements of precision parts such as perforated liner tubes. Summary of the Invention

[0007] To address the aforementioned problems, this invention provides a tungsten alloy coating and its preparation method. The tungsten alloy coating is a tungsten-nickel alloy coating. The preparation method uses nickel sulfamate and sodium tungstate as the main salts, supplemented with specific composite complexing agents, conductive salts, buffers, and additives to form a stable electroplating solution. Electroplating is then performed through plasma cleaning, combined with contour anode and pulse electroplating technology, under matched pulse parameters and mechanical stirring. This method can deposit a high-hardness tungsten alloy coating with uniform thickness and excellent performance on workpieces with complex shapes, especially the inner and outer walls of perforated liner tubes and the inner surfaces of all holes.

[0008] Specifically, it is a tungsten alloy coating made of nickel-tungsten alloy, characterized by a dense and defect-free coating with a thickness of 40~100μm and a Vickers hardness of not less than 900 HV1. Step (1): Prepare the following raw materials for electroplating solution by weight: 80-120 parts nickel aminosulfonate, 70-100 parts sodium tungstate, 60-100 parts composite complexing agent, 10-30 parts conductive salt, 10-20 parts buffer, 0.5-3 parts stress reliever, 0.1-1 part brightener, 0.1-0.5 parts surfactant, 0.5-5 parts rare earth salt, and 1000 parts deionized water; Rare earth salts are premixed with 1 / 3 to 1 / 2 of the composite complexing agent and added to deionized water. After complete dissolution, the remaining components are added. After thorough dissolution, the mixture is stirred evenly and filtered to obtain an electroplating solution. The electroplating solution is placed in an electroplating tank, and the temperature is maintained at 60 to 70°C and the pH value is 8.0 to 9.0. Step (2): After degreasing and acid activation, the perforated liner is bombarded and cleaned using argon plasma in a vacuum environment. Step (3): The perforated liner obtained in step (2) is placed in the electroplating tank as the cathode, and a contoured anode matching the contour of the substrate is used for electroplating under pulsed current and mechanical stirring. Step (4): After electroplating, remove the workpiece, rinse it with deionized water, and then place it in a forced-air drying oven at 80~120℃ for 20~40 minutes using circulating hot air.

[0009] Preferably, in step (1), the composite complexing agent is a system composed of citrate and ethylenediaminetetraacetic acid in a mass ratio of 3 to 5:1; Different complexing agents have different complexing abilities for different metal ions. Using them in combination can better balance the deposition potentials of nickel and tungsten, making them closer together, and can simultaneously take into account the stability of the electroplating solution, the deposition rate, and the coating quality.

[0010] Preferably, in step (1), the conductive salt is nickel sulfate, the buffer is boric acid, the stress reliever is sodium saccharin, the brightener is propargyl alcohol, and the surfactant is sodium dodecyl sulfate. Preferably, in step (1), the rare earth salt is cerium nitrate; Rare earth ion Ce 3+ Adsorption at growth points inhibits rapid grain growth and promotes the formation of nanocrystalline or amorphous structures, thereby significantly improving the hardness, density, and corrosion resistance of the coating. Additionally, rare earth ions (Ce)... 3+ By refining the grain size and improving the deposition process, the intrinsic internal stress of the coating is effectively reduced, preventing crack formation.

[0011] This invention uses nickel sulfamate and sodium tungstate as the main salts, providing a thermodynamic driving force for nickel-tungsten co-deposition. Its advantage lies in employing a citrate-ethylenediaminetetraacetic acid composite complexing agent system. This system, through synergistic action, forms complexes with nickel and tungstate ions of varying stability, not only inhibiting tungstic acid precipitation and ensuring the long-term stability of the plating solution, but also promoting uniform co-deposition of nickel and tungsten at the atomic scale by adjusting the activity and reduction rate of the two metal ions within the cathode diffusion layer. This results in a uniform, dense, defect-free amorphous or microcrystalline nickel-tungsten alloy coating. Simultaneously, the addition of stress-relieving agents, surfactants, and other additives, along with the pre-mixing of rare earth salts with the complexing agent, further refines the grains, reduces internal stress, and avoids the introduction of chloride ions, fundamentally eliminating the initiation source of later pitting corrosion. This significantly improves the long-term stability of the coating in corrosive environments, ultimately ensuring high hardness, high density, and excellent corrosion resistance.

[0012] Preferably, in step (2), the specific steps for plasma cleaning of the perforated liner are as follows: S1, place the perforated liner, which has undergone preliminary degreasing and acid activation, on the cathode tray of the vacuum chamber, ensuring that the matrix axis is parallel to the gas flow direction to facilitate uniform plasma penetration, and close and seal the chamber door; S2, start the mechanical pump and molecular pump group to pump the background vacuum of the vacuum chamber to a level not lower than 5 × 10⁻⁶. -3 S3. High-purity argon gas is introduced into the vacuum chamber as the process gas. The gas flow rate is precisely controlled at 150~250ml / min by a mass flow controller. At the same time, the working pressure in the chamber is stabilized at 30~60Pa by a throttle valve. S4. After the vacuum degree and gas flow rate are stabilized, radio frequency power at a frequency of 13.56MHz is applied to the cathode tray. The power is set at 800~1500W and the processing time lasts for 10~20min. S5. After the processing is completed, the radio frequency power source is first turned off to stop plasma generation, then the process gas is stopped. Then, high-purity nitrogen gas is refilled into the chamber until the pressure returns to normal. Finally, the chamber door is opened, the perforated liner that has been processed is quickly taken out and immediately transferred to the electroplating process to avoid surface contamination. Preferably, in step (3), the conformal anode is a nickel plate, the pulse current density is 6~12 ASD, the pulse frequency is 500~1500Hz, the duty cycle is 25%~35%, the electroplating time is 90~150min, and the stirring rate is 150~250r / min; A perforated liner includes a tube body and a plurality of holes provided on the tube body. The inner wall, outer wall and inner surface of all holes are covered with a dense and defect-free tungsten alloy coating with a thickness of 40~100μm and a Vickers hardness of not less than 900 HV1. As a preferred embodiment, a perforated liner is characterized in that the ratio of the thickness of the tungsten alloy coating at the perforation to the average thickness of the inner wall of the liner is 0.85 to 1.05. This invention utilizes plasma cleaning technology to not only remove physically adsorbed contaminants but also activates the substrate surface at the atomic scale through high-energy particle bombardment, enhancing the chemical bonding and physical adhesion between the coating and the substrate. By employing a contoured anode and pulsed current, the primary current distribution is geometrically optimized, making the electric field lines more uniform on complex contour surfaces and overcoming edge effects. Simultaneously, the concentration recovery effect during the pulse interval optimizes the mass transfer process within the cathode diffusion layer, and the instantaneous high current density promotes crystal nucleation and inhibits grain growth, thereby achieving a finer microstructure and higher uniformity in macroscopic thickness of the coating. Circulating hot air drying, through controlled heat input, systematically removes moisture from the micropores of the coating, avoiding stress caused by rapid moisture vaporization and potentially promoting slight relaxation of atoms within the coating, further releasing internal stress and stabilizing the coating structure.

[0013] This technical solution forms a uniform amorphous composite structure, avoiding the introduction of chloride ions and fundamentally eliminating the long-term stability of the coating in corrosive environments. Rare earth salts, with their unique electronic layer structure, selectively adsorb at the growth interface, effectively reducing the deposition overpotential of tungsten and promoting co-deposition, while also achieving grain refinement and structural densification. Plasma cleaning achieves interface purification and lattice activation at the atomic scale, ensuring metallurgical-grade bonding without weak interfaces. The synergistic effect of the contoured anode and pulsed current breaks through the edge effect of complex structures from the field dimension, while the pulsed current promotes nucleation and relaxation period ion replenishment through transient high-energy input, jointly achieving thickness uniformity and structural integrity in the deep hole region.

[0014] Compared with the prior art, the present invention has the following advantages: 1. This invention solves the problem of uniform electric field distribution in deep holes, inner walls and hole edges of perforated liner by the synergistic effect of the contoured anode and pulse power supply, so that the coating can ignore the shielding effect of complex geometric structures and achieve uniform coverage of the entire area from macro scale to micro contour.

[0015] 2. This invention utilizes the synergistic modulation effect formed by rare earth salts and composite complexing agents. Rare earth elements not only reduce the deposition energy barrier of key elements through interfacial adsorption, but also stabilize the chemical environment of the electroplating solution together with the complexing agent. Thus, while achieving stable co-deposition of high tungsten content, the microstructure of the coating is refined, enabling it to maintain a low internal stress state while obtaining excellent hardness, achieving a balance between toughness and high corrosion resistance that is difficult to achieve with traditional technologies. Attached Figure Description

[0016] Figure 1 This is a microscopic morphology diagram of the tungsten alloy coating described in Example 1 of the present invention; Figure 2 This is a microscopic morphology diagram of the tungsten alloy coating described in Comparative Example 3 of the present invention; Figure 3 This is a microscopic morphology diagram of the tungsten alloy coating described in Comparative Example 4 of the present invention; Detailed Implementation The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0017] The conductive salt is nickel sulfate; The buffer is boric acid; The stress reliever is sodium saccharin; The brightener is propargyl alcohol; The surfactant is sodium dodecyl sulfate.

[0018] Example 1 A perforated liner with a tungsten alloy coating is prepared by the following steps: Step (1): Prepare the electroplating solution raw materials by mass: 100 parts nickel aminosulfonate, 90 parts sodium tungstate, 80 parts composite complexing agent, 20 parts conductive salt, 15 parts buffer, 2 parts stress reliever, 0.5 parts brightener, 0.3 parts surfactant, 3 parts rare earth salt, and 1000 parts deionized water. The composite complexing agent is composed of citrate and ethylenediaminetetraacetic acid in a mass ratio of 4:1, and the rare earth salt is cerium nitrate. Prepare the electroplating solution according to the formula. Premix the rare earth salt with 1 / 2 of the composite complexing agent and add it to deionized water. After it is completely dissolved, add the remaining components. After it is fully dissolved, stir it evenly and filter it to obtain the electroplating solution. Place the electroplating solution in the electroplating tank and maintain the temperature at 70℃ and the pH value at 8.5. Step (2): After the perforated liner is degreased and activated with dilute hydrochloric acid, it is placed in a vacuum plasma cleaning device, argon gas is introduced, and it is treated for 15 minutes at a power of 1000W. Step (3): The perforated liner obtained in step (2) is used as the cathode and immersed together with the nickel contour anode that matches the inner wall profile into the electroplating solution. A pulse power supply is used, with the current density set to 8 ASD, the frequency to 1000 Hz, and the duty cycle to 30%. At the same time, mechanical stirring is performed at a rate of 200 r / min, and the electroplating time is 120 min. Step (4): After electroplating, remove the workpiece, rinse it with deionized water, and dry it in a 100℃ forced-air drying oven for 30 minutes.

[0019] After testing the tungsten alloy coating using Vickers hardness, neutral salt spray, microstructure, and average thickness, the Vickers hardness was measured to be 1100 HV1. The time to develop red rust in the neutral salt spray test was 900 hours. The microstructure was dense and defect-free. The average coating thickness on the inner wall was 88 μm, and the average coating thickness at the apertures was 80 μm. The ratio of the thickness at the apertures to the average thickness of the inner wall coating was 0.91. (See...) Figure 1 The structure in the image is dense, with no defects such as pores, cracks, or inclusions.

[0020] Example 2 A perforated liner with a tungsten alloy coating is prepared by the following steps: Step (1): Prepare the electroplating solution raw materials by mass: 80 parts nickel aminosulfonate, 70 parts sodium tungstate, 60 parts composite complexing agent, 10 parts conductive salt, 10 parts buffer, 0.5 parts stress reliever, 0.1 parts brightener, 0.1 parts surfactant, 0.5 parts rare earth salt, and 1000 parts deionized water. The composite complexing agent is composed of citrate and ethylenediaminetetraacetic acid in a mass ratio of 4:1, and the rare earth salt is cerium nitrate. Prepare the electroplating solution according to the formula. Premix the rare earth salt with 1 / 2 of the composite complexing agent and add it to deionized water. After it is completely dissolved, add the remaining components. After it is fully dissolved, stir it evenly and filter it to obtain the electroplating solution. Place the electroplating solution in the electroplating tank and maintain the temperature at 70℃ and the pH value at 8.5. Step (2): After the perforated liner is degreased and activated with dilute hydrochloric acid, it is placed in a vacuum plasma cleaning device, argon gas is introduced, and it is treated for 15 minutes at a power of 1000W. Step (3): The perforated liner obtained in step (2) is used as the cathode and immersed together with the nickel contour anode that matches the inner wall profile into the electroplating solution. A pulse power supply is used, with the current density set to 8 ASD, the frequency to 1000 Hz, and the duty cycle to 30%. At the same time, mechanical stirring is performed at a rate of 200 r / min, and the electroplating time is 120 min. Step (4): After electroplating, remove the workpiece, rinse it with deionized water, and dry it in a 100℃ forced-air drying oven for 30 minutes.

[0021] After testing the tungsten alloy coating with Vickers hardness, neutral salt spray test, microstructure and average thickness, the Vickers hardness was measured to be 1000 HV1, the time to red rust appear in the neutral salt spray test was 850 h, the microstructure was dense and defect-free, the average thickness of the coating on the inner wall was 70 μm, the average thickness of the coating at the holes was 65 μm, and the ratio of the thickness at the holes to the average thickness of the coating on the inner wall was 0.93.

[0022] Example 3 A perforated liner with a tungsten alloy coating is prepared by the following steps: Step (1): Prepare the raw materials for the electroplating solution by weight: 120 parts nickel aminosulfonate, 100 parts sodium tungstate, 100 parts composite complexing agent, 30 parts conductive salt, 20 parts buffer, 3 parts stress reliever, 1 part brightener, 0.5 parts surfactant, 5 parts rare earth salt, and 1000 parts deionized water. The composite complexing agent is composed of citrate and ethylenediaminetetraacetic acid in a mass ratio of 4:1, and the rare earth salt is cerium nitrate. Prepare the electroplating solution according to the formula. Premix the rare earth salt with 1 / 2 of the composite complexing agent and add it to deionized water. After it is completely dissolved, add the remaining components. After it is fully dissolved, stir it evenly and filter it to obtain the electroplating solution. Place the electroplating solution in the electroplating tank and maintain the temperature at 70℃ and the pH value at 8.5. Step (2): After the perforated liner is degreased and activated with dilute hydrochloric acid, it is placed in a vacuum plasma cleaning device, argon gas is introduced, and it is treated for 15 minutes at a power of 1000W. Step (3): The perforated liner obtained in step (2) is used as the cathode and immersed together with the nickel contour anode that matches the inner wall profile into the electroplating solution. A pulse power supply is used, with the current density set to 8 ASD, the frequency to 1000 Hz, and the duty cycle to 30%. At the same time, mechanical stirring is performed at a rate of 200 r / min, and the electroplating time is 120 min. Step (4): After electroplating, remove the workpiece, rinse it with deionized water, and dry it in a 100℃ forced-air drying oven for 30 minutes.

[0023] After testing the tungsten alloy coating with Vickers hardness, neutral salt spray, microstructure, and average coating thickness, the Vickers hardness was measured to be 1200 HV1, the time to red rust appear in the neutral salt spray test was 950 h, the microstructure was dense and defect-free, the average coating thickness on the inner wall was 80 μm, the average coating thickness at the holes was 75 μm, and the ratio of the thickness at the holes to the average thickness of the coating on the inner wall was 0.94.

[0024] Comparative Example 1 The only difference from Example 1 is that the electroplating solution is composed of: 70 parts nickel aminosulfonate, 60 parts sodium tungstate, 50 parts composite complexing agent, 5 parts conductive salt, 5 parts buffer, 0.1 parts stress reliever, 0.05 parts brightener, 0.05 parts surfactant, 0.1 parts rare earth salt, and 1000 parts deionized water.

[0025] After testing the tungsten alloy coating with Vickers hardness, neutral salt spray test, microstructure and average thickness, the Vickers hardness was measured to be 650 HV1, the time to red rust appear in the neutral salt spray test was 600 h, the microstructure was dense and defect-free, the average thickness of the coating on the inner wall was 35 μm, the average thickness of the coating at the holes was 28 μm, and the ratio of the thickness at the holes to the average thickness of the coating on the inner wall was 0.8.

[0026] Comparative Example 2 The only difference from Example 1 is that the electroplating solution is composed of: 150 parts nickel aminosulfonate, 120 parts sodium tungstate, 120 parts composite complexing agent, 50 parts conductive salt, 30 parts buffer, 5 parts stress reliever, 2 parts brightener, 1 part surfactant, 10 parts rare earth salt, and 1000 parts deionized water.

[0027] After testing the tungsten alloy coating with Vickers hardness, neutral salt spray test, microstructure and average thickness, the Vickers hardness was measured to be 750 HV1, the time to red rust appear in the neutral salt spray test was 650 h, the microstructure was dense and defect-free, the average thickness of the coating on the inner wall was 40 μm, the average thickness of the coating at the holes was 30 μm, and the ratio of the thickness at the holes to the average thickness of the coating on the inner wall was 0.75.

[0028] Comparative Example 3 The only difference from Example 1 is that the complexing agent used is only citrate.

[0029] After testing the tungsten alloy coating using Vickers hardness, neutral salt spray, microstructure, and average thickness, the Vickers hardness was measured to be 650 HV1. The time to develop red rust in the neutral salt spray test was 500 hours. Microscopic morphology revealed defects such as pores and inclusions. The average coating thickness on the inner wall was 32 μm, and the average coating thickness at the pores was 25 μm. The ratio of the thickness at the pores to the average thickness of the inner wall coating was 0.78. Figure 2 The image contains many defects; the areas within the box are inclusions, and the arrows mark holes.

[0030] Comparative Example 4 The only difference from Example 1 is that no rare earth salts are added.

[0031] After testing the tungsten alloy coating using Vickers hardness, neutral salt spray, microstructure, and average thickness, the Vickers hardness was measured to be 620 HV1. The time to red rust appeared in the neutral salt spray test was 510 hours. Microscopic morphology revealed defects such as pores and inclusions. The average coating thickness on the inner wall was 30 μm, and the average coating thickness at the pores was 20 μm. The ratio of the thickness at the pores to the average thickness of the inner wall coating was 0.67. Figure 3 The image contains many defects; the areas within the box are inclusions, and the arrows mark holes.

[0032] Comparative Example 5 The only difference from Example 1 is that nickel aminosulfonate is replaced with nickel chloride.

[0033] After testing the tungsten alloy coating with Vickers hardness, neutral salt spray test, microstructure and average thickness, the Vickers hardness was measured to be 800 HV1, the time for red rust to appear in the neutral salt spray test was 300 h, the microstructure was dense and defect-free, the average thickness of the coating on the inner wall was 45 μm, the average thickness of the coating at the holes was 36 μm, and the ratio of the thickness at the holes to the average thickness of the coating on the inner wall was 0.8.

[0034] Comparative Example 6 The only difference from Example 1 is that the perforated liner is placed directly into the electroplating tank after being degreased and activated with dilute hydrochloric acid.

[0035] After testing the tungsten alloy coating with Vickers hardness, neutral salt spray test, microstructure and average thickness, the Vickers hardness was measured to be 720 HV1, the time to red rust appeared in the neutral salt spray test was 500 h, and defects such as pores and inclusions were visible in the microstructure. The average thickness of the coating on the inner wall was 38 μm, the average thickness of the coating at the holes was 30 μm, and the ratio of the thickness at the holes to the average thickness of the coating on the inner wall was 0.79.

[0036] Comparative Example 7 The only difference from Example 1 is that a conventional DC power supply with a current density of 8 ASD is used during electroplating.

[0037] After testing the tungsten alloy coating with Vickers hardness, neutral salt spray test, microstructure and average thickness, the Vickers hardness was measured to be 700 HV1, the time to red rust appeared in the neutral salt spray test was 550 h, the microstructure was dense and defect-free, the average thickness of the coating on the inner wall was 38 μm, the average thickness of the coating at the holes was 30 μm, and the ratio of the thickness at the holes to the average thickness of the coating on the inner wall was 0.79.

[0038] Comparative Example 8 The only difference from Example 1 is that only a pulse power supply is used during electroplating, and no contour anode is used.

[0039] After testing the tungsten alloy coating with Vickers hardness, neutral salt spray test, microstructure and average thickness, the Vickers hardness was measured to be 650 HV1, the time to red rust appeared in the neutral salt spray test was 500 h, and defects such as pores and inclusions were visible in the microstructure. The average thickness of the coating on the inner wall was 35 μm, the average thickness of the coating at the pores was 26 μm, and the ratio of the thickness at the pores to the average thickness of the coating on the inner wall was 0.74.

[0040] Comparative Example 9 The only difference from Example 1 is that a conventional DC power supply with a current density of 8 ASD is used during electroplating, and pulse mode and contour anode are not used.

[0041] After testing the tungsten alloy coating with Vickers hardness, neutral salt spray test, microstructure and average thickness, the Vickers hardness was measured to be 550 HV1, the time to red rust appeared in the neutral salt spray test was 450 h, the microstructure showed defects such as pores and inclusions, the average thickness of the coating on the inner wall was 32 μm, the average thickness of the coating at the pores was 20 μm, and the ratio of the thickness at the pores to the average thickness of the coating on the inner wall was 0.63.

[0042] Comparative Example 10 The only difference from Example 1 is that the pH value of the electroplating solution is 7.0.

[0043] After testing the tungsten alloy coating with Vickers hardness, neutral salt spray test, microstructure and average thickness, the Vickers hardness was measured to be 450 HV1, the time to red rust appear in the neutral salt spray test was 400 h, the microstructure was dense and defect-free, the average thickness of the coating on the inner wall was 25 μm, the average thickness of the coating at the holes was 20 μm, and the ratio of the thickness at the holes to the average thickness of the coating on the inner wall was 0.8.

[0044] Comparative Example 11 The only difference from Example 1 is that the plasma cleaning power is 2000W and the processing time is 30min.

[0045] After testing the tungsten alloy coating with Vickers hardness, neutral salt spray test, microstructure and average thickness, the Vickers hardness was measured to be 680 HV1, the time to red rust appeared in the neutral salt spray test was 520 h, and defects such as pores and inclusions were visible in the microstructure. The average thickness of the coating on the inner wall was 36 μm, the average thickness of the coating at the pores was 30 μm, and the ratio of the thickness at the pores to the average thickness of the coating on the inner wall was 0.83.

[0046] Vickers hardness test: According to GB / T 4340.1-2024 "Metallic materials - Vickers hardness test - Part 1: Test method", a load of 9.807 N is used; Microstructure testing: according to GB / T 13298-2015 "Metallic Microstructure Examination Methods"; The average thickness of the coating was measured according to GB / T 6462-2005, "Microscopic Method for Measuring the Thickness of Metallic and Oxide Coatings". The specific procedures are as follows: Sample preparation: Samples were taken from the coatings of each example / comparative example, with a size of 5mm×5mm×10mm. After being inlaid and polished with 400#-2000# sandpaper in stages, they were ready for use.

[0047] Table 1 shows a comparison of the performance data of the examples and the comparative examples.

[0048] Table 1 Performance data of the examples and comparative examples

[0049] Through component ratio design, Examples 1-3 demonstrate that the composite complexing agent can establish a stable multi-coordination site environment, precisely control the co-deposition of nickel and tungsten ions at the molecular scale, and deliberately avoid the introduction of chloride ions, thus fundamentally eliminating the inducing source of later pitting corrosion and significantly improving the long-term stability of the coating in corrosive environments. Rare earth salts, with their unique electronic layer structure, selectively adsorb at the growth interface, which not only effectively reduces the deposition overpotential of tungsten and promotes co-deposition, but also achieves grain refinement and structural densification. Plasma cleaning achieves interface purification and lattice activation at the atomic scale, providing a guarantee for obtaining metallurgical-grade bonding without weak interfaces. The synergistic effect of the contoured anode and pulsed current breaks through the edge effect of complex structures from the field dimension, while the pulsed current promotes nucleation and relaxation period ion replenishment through transient high-energy input, jointly achieving thickness uniformity in the deep hole region.Comparative Example 1 had too low a component, failing to form a sufficiently thick and correctly composed reinforcing phase; Comparative Example 2 had too high a component, leading to an imbalance in the electroplating solution and the generation of a large amount of precipitation, which in turn damaged the density and adhesion of the coating; Comparative Example 3 used only citrate as a complexing agent, and the complexing ability of citrate alone was insufficient to stabilize the high concentration of tungsten, resulting in low co-deposition efficiency, insufficient tungsten content in the coating, low coating hardness, and unstable electroplating solution, leading to the formation of pores and inclusions; Comparative Example 4 did not add rare earth salts, and the lack of rare earth salts resulted in the loss of catalysis in the co-deposition process, leading to difficulties in tungsten deposition, poor coating growth, coarse grains, low hardness, poor corrosion resistance, and poor adhesion. Insufficient density; Comparative Example 5 replaced nickel sulfamate with nickel chloride. The use of nickel chloride introduced chloride ions. Although the hardness and thickness were still acceptable, the neutral salt spray test time plummeted from 900 hours to 300 hours. The chloride ions were encapsulated in the coating, becoming corrosion ignition points. Once the corrosive medium arrived, it would quickly cause pitting corrosion; Comparative Example 6 placed the perforated liner directly into the electroplating tank after degreasing and activation with dilute hydrochloric acid without plasma cleaning. The substrate surface had invisible contaminants and a weak interface layer, which resulted in poor coating adhesion. Under deposition stress or corrosive environment, it was easy to fail from the interface, and corrosion would preferentially start from the weak bonding area, greatly reducing corrosion resistance; Comparative Example 7 used a traditional DC power supply with a current density of 8 ASD during electroplating. The continuous concentration polarization in DC electroplating resulted in high internal stress, low hardness, and poor density of the plating layer. Comparative Example 8 used a pulsed power supply without a contoured anode, failing to address the edge effects of the perforated liner's inner wall and the holes. The electric field lines could not be evenly distributed, directly leading to severe uneven thickness on the inner wall and at the hole edges, failing to form effective all-area protection. Comparative Example 9 also used a traditional DC power supply with a current density of 8 ASD during electroplating, without a pulsed mode or contoured anode. The continuous concentration polarization in DC electroplating resulted in low hardness and poor density of the plating layer, failing to provide adequate protection. Using a contoured anode cannot solve the edge effect of the inner wall and orifices of the perforated liner, which directly leads to severe uneven thickness of the inner wall and orifice edges. The pH value of the electroplating solution in Comparative Example 10 is 7.0, which deviates from the optimal range of the complexing agent, especially the optimal working pH value of ethylenediaminetetraacetic acid, resulting in a decrease in complexing ability, instability of the electroplating solution, loss of control of the co-deposition process, and a significant overall decline in all performance indicators. The plasma cleaning power of Comparative Example 11 is 2000W, and the treatment time is 30min. Excessive power and excessively long treatment time will cause over-cleaning of the liner, which will damage the liner surface, form new defects, and reduce the adhesion and coating quality.

[0050] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a tungsten alloy coating, characterized in that, Includes the following steps: Step (1): Prepare the following raw materials for electroplating solution by weight: 80-120 parts nickel aminosulfonate, 70-100 parts sodium tungstate, 60-100 parts composite complexing agent, 10-30 parts conductive salt, 10-20 parts buffer, 0.5-3 parts stress reliever, 0.1-1 part brightener, 0.1-0.5 parts surfactant, 0.5-5 parts rare earth salt, and 1000 parts deionized water; Rare earth salts are premixed with 1 / 3 to 1 / 2 of the composite complexing agent and added to deionized water. After complete dissolution, the remaining components are added. After thorough dissolution, the mixture is stirred evenly and filtered to obtain an electroplating solution. The electroplating solution is placed in an electroplating tank, and the temperature is maintained at 60 to 70°C and the pH value is 8.0 to 9.

0. Step (2): After degreasing and acid activation, the perforated liner is bombarded and cleaned using argon plasma in a vacuum environment; Step (3): The perforated liner obtained in step (2) is placed in the electroplating tank as the cathode, and electroplating is carried out under pulsed current and mechanical stirring using a contoured anode that matches the contour of the substrate. Step (4): After electroplating, remove the workpiece, rinse it with deionized water, and then place it in a forced-air drying oven at 80~120℃ for 20~40 minutes using circulating hot air.

2. The method for preparing a tungsten alloy coating according to claim 1, characterized in that, In step (1), the complexing agent is a system composed of citrate and ethylenediaminetetraacetic acid in a mass ratio of 3 to 5:

1.

3. The method for preparing a tungsten alloy coating according to claim 1, characterized in that, In step (1), the conductive salt is nickel sulfate, the buffer is boric acid, the stress reliever is sodium saccharin, the brightener is propargyl alcohol, and the surfactant is sodium dodecyl sulfate.

4. The method for preparing a tungsten alloy coating according to claim 1, characterized in that, In step (1), the rare earth salt is cerium nitrate.

5. The method for preparing a tungsten alloy coating according to claim 1, characterized in that, In step (2), the power of plasma cleaning is 800~1500W and the processing time is 10~20min.

6. The method for preparing a tungsten alloy coating according to claim 1, characterized in that, In step (3), the conformal anode is a nickel plate, the pulse current density is 6~12 ASD, the pulse frequency is 500~1500Hz, the duty cycle is 25%~35%, the electroplating time is 90~150min, and the stirring rate is 150~250r / min.

7. A tungsten alloy coating, characterized in that, The tungsten alloy coating is prepared by the method described in any one of claims 1-6. The tungsten alloy coating is a tungsten-nickel alloy coating with a thickness of 40~100μm and a Vickers hardness of not less than 900 HV1.

8. A perforated liner, comprising a tube body and a plurality of holes disposed on the tube body, characterized in that, The inner wall, outer wall, and inner surface of all the holes of the tube are covered with the tungsten alloy coating as described in claim 7.

9. The perforated liner as described in claim 8, characterized in that, The ratio of the thickness of the tungsten alloy coating at the aperture to the average thickness of the inner wall of the tube is 0.85~1.05.

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