A method for directly plating thick nickel on a tungsten alloy surface

Abstract

The present application relates to a kind of thick nickel plating method of tungsten alloy surface directly.The steps of the present application are obtained by the following: first, the surface of tungsten alloy is pretreated to its to be plated surface exposes fresh metal and the roughness Ra of welding surface is less than or equal to 0.2 μm;Then with nickel acetate electrolyte as main electroplating solution, and SDS is added to it, the concentration of SDS is 0.04-0.1 g / L, after being dissolved sufficiently, start electroplating, control current density 0.3-1.1 A / dm 2 When electroplating, pH 3.5-5.5.The initial concentration of sodium chloride in the used nickel acetate electroplating solution is 3-14 g / L, the initial concentration of Ni 2+ Ion is 5-10 g / L, and the initial pH is 3.5-5.5.The number of drugs used in the present application is small, highly dangerous reagents such as hydrofluoric acid and sulfuric acid do not need to be used, expensive electroplating equipment such as pulse power is also not needed, the requirement for instrument is low, safety is good, production efficiency is high, and quite thick and dense nickel plating layer can also be stably obtained, which provides a low-cost, industrialized production method for the surface of tungsten alloy used for diffusion bonding to electroplate thick nickel layer.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of surface treatment, in particular to a method for directly plating thick nickel on the surface of tungsten alloy. BACKGROUND

[0002] The preparation method of tungsten alloy / steel composite components includes diffusion welding, brazing, co-sintering, etc. In order to inhibit the generation of intermetallic compounds and relieve residual stress, a suitable interlayer metal must be added at the welding interface. The traditional form of interlayer addition is foil or powder, but the purity and thickness of the interlayer are difficult to control and difficult to apply. In addition, the surface cleaning of the interlayer is also a big problem. Although PVD, CVD and other deposition methods can deposit a certain thickness of metal cover layer on the surface of tungsten alloy, only a very thin metal layer can be deposited, which cannot meet the existing thickness requirements of the interlayer, and the construction cost is high and the efficiency is low. Compared with the above, the electroplating process is mature, the equipment is highly automated, and the volume and shape of the sample are less limited. Therefore, using electroplating as a method for depositing metal on the surface of tungsten alloy, especially for depositing samples with complex surfaces, is an ideal treatment method. In addition, the nickel deposition layer can not only be used as a welding interlayer, but also can improve the electrical conductivity of tungsten alloy itself and serve as a substrate for other composite plating layers.

[0003] However, the electrical conductivity of tungsten alloy itself is not good, and the thickness requirement of the interlayer for diffusion bonding is very high, at least 10-20 μm, which exceeds the thickness of commonly used decorative plating or functional plating (a few microns). At present, there is no thick nickel electroplating process developed for tungsten alloy for diffusion bonding. In the existing literature on tungsten alloy electroplating process (CN102465325 A, CN103173821 B and CN105420699 B), not only is the plating layer very thin, but also dangerous reagents such as hydrofluoric acid and sulfuric acid are required during electroplating, which causes serious environmental pollution and safety hazards. It is not suitable for laboratory exploration experiments and is difficult to achieve industrial production at low cost. Therefore, a process for depositing thick nickel on the surface of tungsten alloy is needed, which is simple in operation, safe and controllable, and low in cost. SUMMARY

[0004] The present application aims to provide a method for depositing thick nickel layer on tungsten alloy substrate using direct current power, which adjusts a series of parameters such as current density, electroplating solution Ni 2+ ion concentration and pH to obtain a relatively thick pure nickel plating layer with good adhesion, low porosity, fine crystallization and continuous thickness to meet the welding needs of tungsten alloy; replace the traditional sulfate or chloride salt strong acid salt electroplating solution system with acetate system to reduce the use of buffer (such as boric acid); use acetic acid instead of traditional hydrofluoric acid or concentrated sulfuric acid cleaning agent to reduce pollution caused by strong acid and hydrofluoric acid.

[0005] The technical solution of the present invention is: a method for directly plating thick nickel onto the surface of a tungsten alloy, comprising the following steps:

[0006] Step 1: Surface Pretreatment of Tungsten Alloy

[0007] The oxide layer on the tungsten alloy surface is removed by mechanical machining, followed by grinding and polishing until the surface to be plated exposes fresh metal and the surface roughness is less than Ra0.2 μm; then it is cleaned sequentially with detergent + hot water, ethanol and acetic acid to obtain a cleaned sample to be plated;

[0008] Step 2: Nickel plating

[0009] First, add nickel acetate plating solution to the electroplating tank, then add sodium dodecyl sulfate (SDS) and dissolve it completely. The amount of SDS added is 0.04-0.1 g / L, preferably 0.04-0.08 g / L. Adjust the pH of the electroplating tank to 3.5-5.5, preferably 4-4.7, and ideally 4.2-4.6. Use an electrolytic nickel plate as the anode and connect it to the positive terminal of the power supply. Connect the sample to be plated to the negative terminal of the power supply. Turn on the power supply and set the target current density to 0.3-1.1 A / dm³. 2 The preferred value is 0.35-0.9 A / dm. 2 Further preferably, it is 0.35-0.8 A / dm 2 Electroplating begins; the initial concentration of sodium chloride in the nickel acetate electroplating solution is 3-14 g / L, preferably 4-8 g / L, more preferably 5 g / L, and the initial concentration of glacial acetic acid is 5-25 ml / L. The initial Ni... 2+ The concentration of ions is 5-10 g / L.

[0010] In industrial applications, tungsten alloy surface pretreatment includes: removing significant oxide layers from the tungsten alloy surface using machining methods such as sandblasting, turning, and polishing; then, grinding and polishing the surfaces to be welded. Following this, ultrasonic cleaning is performed sequentially using detergent + hot water, ethanol, and acetic acid, with each step repeated 1-2 times. The sample is then immediately removed and thoroughly cleaned with running deionized water, completing the pretreatment. To further improve performance, the surface finishing requirements for the tungsten alloy parts to be plated are: non-welding surfaces must expose fresh metal surfaces, and welding surfaces must be finely polished with a roughness Ra less than or equal to 0.2 μm.

[0011] The process for ultrasonic cleaning of tungsten alloy parts to be plated using detergent + hot water, ethanol, and acetic acid in sequence is as follows: hot water washing uses commercially available alkaline detergent mixed with hot water, the detergent is added at 5-15 g / L, the hot water temperature is 85-100°C, the detergent is dissolved in hot water, the sample is immersed in the solution, and ultrasonic cleaning is performed, the cleaning time is 5-10 min, and the cleaning frequency is 1-2 times; then the sample is immersed in anhydrous ethanol (purity >99.5%) after being washed with flowing cold water to remove the residual detergent on the surface, the anhydrous ethanol temperature is 20-50°C, the cleaning time is 5-10 min, and the cleaning frequency is 1-2 times; then the sample is immersed in an acetic acid aqueous solution after being washed with flowing anhydrous ethanol, the acetic acid aqueous solution has a concentration of 40-60%vol, the sample is immersed after the acetic acid is dissolved in deionized water and stirred evenly, the ultrasonic cleaning time is 5-10 min, the cleaning temperature is 20-50°C, and the sample is washed with flowing cold water to remove the residual acetic acid solution on the surface after cleaning, and the surface treatment is completed. The flowing cold water can be deionized water or distilled water, and tap water that meets the “Drinking Water Health Standards” can be used for washing when the conditions are limited. The ethanol and acetic acid washing solutions can be filtered and reused after supplementing ethanol and acetic acid, and the solutions can be replaced when they are significantly discolored.

[0012] The nickel acetate electroplating solution can be prepared directly using nickel acetate salt, and the Ni 2+ ion concentration, pH, and the foregoing are consistent, and the remaining parameters do not need to be changed too much. However, the nickel content of nickel acetate is low, and high-purity reagents are expensive, in order to save costs and improve the quality of the plated layer and speed up the plating process, electrolysis can also be used to prepare the nickel acetate electroplating solution. The electrolysis method for preparing the nickel acetate electroplating solution includes: first, using sodium chloride, glacial acetic acid, and water to prepare a solution, the sodium chloride concentration is 3-14 g / L, and the glacial acetic acid concentration is 15-30 mL / L, then using an electrolytic nickel plate as the cathode and anode for electrolysis, and electrolyzing until the Ni 2+ ion concentration in the solution is 5-10 g / L. In the present application, the reason for controlling the Ni 2+ ion concentration in the nickel acetate electroplating solution before electroplating is that the Ni 2+The concentration directly determines the deposition efficiency and coating quality of the coating. Too high concentration will cause the coating stress to be too large, cracking, even burning and nodulation, and too low concentration will cause poor conductivity of the plating solution and low plating efficiency, and higher voltage is required to achieve plating. In the preparation of the nickel acetate electroplating solution by the electrolysis method, 3-14 g / L of sodium chloride is used to reduce the polarization of the nickel anode and improve the dissolution efficiency of the nickel anode, and 15-30 ml / L of glacial acetic acid is used to adjust the pH of the electrolyte to be slightly acidic to avoid the precipitation of nickel hydroxide due to the increase of pH in the electrolysis process. The specific steps of preparing the nickel acetate electroplating solution by the electrolysis method are as follows: first, weigh the sodium chloride and dissolve it in deionized water, then measure the glacial acetic acid and mix it with the above solution and stir uniformly, and then add deionized water to supplement the target concentration for standby. Then pour the solution into the electroplating tank, use the electrolytic nickel plate (purity above 99.5%) as the cathode and anode for electrolysis, and electrolyze until the concentration of Ni ions is 5-10 g / L. The reference process is as follows: first, weigh 5 g of sodium chloride and dissolve it in a small amount of deionized water, then measure 25 mL of glacial acetic acid and mix it with the above solution and stir uniformly, add deionized water to dilute the mixed solution to 1 L, then pour the mixed solution into the electroplating tank; use the electrolytic nickel plate (purity above 99.5%) as the cathode and anode to electrolyze at room temperature, the electrolysis current is 2 A, the electrolysis time is 325 min, and after electrolysis, the electroplating solution is filtered and supplemented to 1 L for standby, because part of the nickel will be deposited on the cathode, at this time the concentration of nickel ions in the solution is 5.611 g / L (atomic absorption spectrometry).

[0013] When electroplating nickel, direct current electroplating nickel with constant current density is used. The method for adjusting the pH of direct current electroplating nickel with constant current density is as follows: before plating, if the pH is too high, glacial acetic acid can be added to lower it, and if the pH is too low, graphite or an electrolytic nickel plate can be used as the cathode and anode to electrolyze the electroplating solution with appropriate current (such as 2 A) to increase the pH. The pH will slowly rise during the electroplating process, and the pH of the system can be monitored in time and supplemented with glacial acetic acid.

[0014] The process conditions for direct current electroplating nickel with constant current density are as follows: the current density is 0.3-1.1 A / dm 2 , preferably 0.35-0.9 A / dm 2 , further preferably 0.35-0.8 A / dm 2 , of course 0.35-0.4 A / dm 2 , also including 0.4-0.6 A / dm 2 , 0.6-0.7 A / dm 2 , 0.7-0.8 A / dm 2The plating time can be up to 10 hours or more according to the thickness requirement, and the plating layer will not crack, the plating solution temperature is less than or equal to 30 DEG C, and the plating solution can be stirred by mechanical stirring, magnetic stirring, air flow stirring or directly moving the sample, but no significant bubbles can be introduced into the plating bath. In the present application, too low current density will result in too long deposition time, and too high current density will result in too fast deposition speed, nodule or cracking, and even local overburning.

[0015] In the constant current density direct current nickel plating, the temperature of the plating solution is controlled to be 10-30 DEG C, preferably 20-30 DEG C, more preferably 20-27 DEG C, and further more preferably 20-25 DEG C.

[0016] In the present application, the plating layer with a thickness of 24-25 microns can be obtained in 208 minutes, the plating layer with a thickness of greater than or equal to 80 microns can be obtained in 1295 minutes, and the plating layer with a thickness of greater than or equal to 180 microns can be obtained in 3000-3100 minutes, and the plating layer is well combined with the substrate, meeting the requirements of diffusion bonding.

[0017] After the plating is completed, the sample is taken out of the plating bath, washed with deionized water and dried, and the target plated part is obtained, and the remaining plating solution can be filtered and recovered, and the pH is adjusted for later use in the preparation of nickel acetate plating solution by electrolysis method.

[0018] The present application carries out plating quality inspection on the nickel plating layer, including visual inspection of the plating layer quality and judgment of the plating layer thickness and joint strength after diffusion welding with steel.

[0019] The diffusion bonding and test conditions are: the plating layer on the surface to be welded and the butt joint steel block are polished to Ra less than 0.2 microns, then washed thoroughly and diffusion bonded by hot pressing or hot isostatic pressing, the diffusion bonding temperature is 900-1000 DEG C, the welding pressure is 10-40 MPa (hot pressing diffusion) and 50-200 MPa (hot isostatic pressing diffusion), and the joint evaluation method is tensile strength. This test method is also the first of the present application.

[0020] The beneficial effects of the present application are: compared with the existing technology, the use of cleaning agent and plating solution of acetate system for rust removal and plating on the surface of tungsten alloy avoids the use of highly or highly polluting drugs such as hydrofluoric acid or sulfuric acid, which is safe and environmentally friendly; the use of direct current power supply and a few types of drugs can complete the plating, the process is simple, and meets the laboratory plating requirements; the use of lower current density range can match the poor conductivity of tungsten alloy, realize thick plating layer deposition, obtain the required nickel plating layer with adjustable thickness in a large range, and meet the needs of tungsten alloy and steel welding.

[0021] Principle and advantage

[0022] The application discloses a green and environment-friendly method for direct plating of thick nickel on a tungsten alloy surface under constant current density for diffusion connection.

[0023] The specific principle is as follows: first, a nickel acetate electroplating solution is prepared, which can be prepared by electrolysis or by using a nickel acetate salt, preferably by electrolysis, because the solution prepared by electrolysis has higher purity and lower cost, thereby saving the problems of nickel acetate storage and preparation. Sodium chloride in the electroplating solution can improve the conductivity of the solution and prevent nickel anode passivation, thereby improving the anode dissolution efficiency; acetic acid can provide acetate on one hand and adjust the pH to avoid the formation of too much hydroxyl to make Ni 2+ Precipitate as nickel hydroxide, and can also form an acetic acid-acetate buffer system with the generated nickel acetate, so that no additional buffer such as boric acid needs to be added, thereby avoiding the inclusion of additional buffers; then, the sample is pretreated by using mechanical polishing and a detergent + hot water, ethanol and acetic acid in sequence for ultrasonic cleaning, the mechanical processing and polishing are mainly used to expose the fresh surface and reduce the difficulty of subsequent cleaning, and the fresh metal surface can be exposed on the unimportant surface, and the important welding surface needs to be polished to the required surface roughness; the hot water ultrasonic cleaning uses an alkaline detergent containing a surfactant, which can remove various types of oil stains including mineral oil on the surface of the sample, and can also remove the possible tungsten oxides in the alkaline solution at high temperature; the anhydrous ethanol cleaning is used to further remove residual organic matter and the detergent; and the acetic acid cleaning is used to further remove the tungsten oxides and nickel-iron oxides on the tungsten alloy surface, expose the fresh and activated surface, improve the adhesion of the plating layer, and wash away the possible residual ethanol in the previous step to prevent the sample from polluting the electroplating solution when the sample is put into the electroplating tank.

[0024] Then, the cleaned tungsten alloy is plated. Because the conductivity of the tungsten alloy is poor, a higher current density and a higher cation concentration cannot be used as in the plating of steel and iron parts, which will cause stress concentration or serious local overburning of the plating layer, thereby causing the failure of the plating layer and making it difficult to obtain a thick plating layer, and the more suitable current density is 0.3-1.1 A / dm 2 , and the more suitable Ni 2+The ion concentration is 5-10 g / L, the concentration can be quickly identified by colorimetry, and when the concentration exceeds the tolerance, it can be diluted with deionized water; since acetic acid and nickel acetate can form a buffer system, the pH during electroplating will only slowly increase, and when it exceeds the range, ice acetic acid is added in time to adjust the pH to the target range; a proper amount of SDS is added before electroplating as a pinhole inhibitor, so that the surface tension of hydrogen bubbles is reduced and timely overflow from the surface of the plated part, preventing pores from being wrapped in the plated layer, resulting in low density of the plated layer or even pinholes and nodules.

[0025] Compared with the prior art, the present application has the advantages that:

[0026] 1. The electroplating process is simple, and the drugs are low in toxicity, which is not only suitable for laboratory-level small-batch sample electroplating, but also can be expanded to industrial production. The electroplating solution using acetic acid system only needs sodium chloride, nickel acetate (electrolytic solution preparation can omit this drug), glacial acetic acid, electrolytic nickel plate, and sodium dodecyl sulfate (SDS), and the auxiliary reagent only needs alkaline detergent (dishwashing liquid, laundry detergent, etc.) and ethanol. Since acetic acid and acetate can form a buffer system, no additional pH buffer (boric acid, etc.) is needed to maintain the stability of the plating solution pH. The electroplating can be carried out stably at room temperature (25°C) without the need for additional constant temperature equipment. Ordinary direct current power supply can be used to obtain better results without the need for expensive pulse power supply.

[0027] 2. The plated layer has good bonding quality, high density, and continuous controllable thickness, and matches the electrical conductivity of tungsten alloy. A relatively thick nickel plating layer (more than 20 μm) can be obtained using a low current density, which can meet the needs of different samples for different thicknesses of the intermediate layer and can cover the plating layer on the curved surface without cracking.

[0028] 3. After actual diffusion welding of the electroplated sample and steel, a high interface bonding strength can be obtained. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 is the surface effect of short-time electroplating (0.76 A / dm 2 , 6h) when the process is appropriate, and the surface effect (b) of long-time electroplating (0.76 A / dm 2 , 18h) when the process is appropriate. The surface of the electroplated layer is flat and dense, even if the long-time electroplated layer has only a small amount of pits, no pinholes and nodules, and after slight polishing, it can meet the welding requirements.

[0030] Figure 2These are side views of the interfaces in Examples 1, 2, 3, 4, 5, 6, and 7. Some images were taken after the samples were broken. (a): Example 1; (b): Example 2; (c): Example 3; (d): Example 4; (e): Example 5; (f): Example 6; (g): Example 7. The measured Ni layer thicknesses after welding were 24 μm, 43 μm, 80 μm, 17 μm, 184 μm, 45 μm, and 17 μm, respectively. The welded coatings were dense and free of pores, and no significant cracks were found, indicating that this invention can provide dense Ni coatings over a wide thickness range.

[0031] Figure 3 These are comparison images of the electroplating effects on thread samples with a pitch of 2 mm. The left side shows the result after electroplating (0.76 A / dm). 2 (3h), the right side is before electroplating, where the coating is dense without blistering or cracking and has a uniform color.

[0032] Figure 4 This is a schematic diagram of the sample size for testing the tensile strength of the sample joint (a) and the tensile strength of the joint in the corresponding embodiment (b).

[0033] Figure 5 These are real-life images of coating failures in various comparison examples that deviate from the optimal parameter range. (a) is Comparative Example 1, (b) is Comparative Example 2, (c) is Comparative Example 3, and (d) is Comparative Example 4. Detailed Implementation

[0034] The present invention will now be described in detail through specific embodiments. Example

[0035] (1) Preparation of nickel acetate electroplating solution by electrolysis: First, weigh 5g of sodium chloride and dissolve it in a small amount of deionized water. Then, measure 25 mL of glacial acetic acid, mix it with the sodium chloride and stir evenly. Add deionized water to dilute the mixed solution to 1 L and pour the mixed solution into the electroplating tank. Use electrolytic nickel plates (purity above 99.5%) as anode and cathode and perform electrolysis at room temperature. The electrolysis current is 2 A and the electrolysis time is 325 min. After electrolysis, filter to obtain nickel acetate solution for electroplating (at this time, the nickel acetate solution for electroplating contains Ni...). 2+ The concentration was 5.611 g / L, and the analytical method was atomic absorption spectrometry.

[0036] (2) Tungsten alloy surface pretreatment: select a 93W-4.9Ni-2.1Fe tungsten alloy test block with a diameter of 30 mm and a height of 13 mm, turn the entire cylindrical surface and one end surface to expose the fresh surface, and polish the other end surface to Ra less than 0.2 μm, then place the sample on the hanger, first use hot water cleaning, hot water temperature 96 ℃, detergent addition amount 10 g / L, completely immerse the sample in hot water during ultrasonic cleaning, ultrasonic for 5 min, then use flowing cold water to rinse the surface residual detergent; then immerse the sample in anhydrous ethanol (purity 99.5%) for ultrasonic cleaning, anhydrous ethanol temperature 30 ℃, ultrasonic cleaning time 5 min, after cleaning, immerse the sample in clean anhydrous ethanol and then immerse it in acetic acid solution for ultrasonic cleaning; acetic acid aqueous solution concentration is 50% vol, immerse the sample in 30 ℃ using ultrasonic machine for 5 min, the preparation method of acetic acid aqueous solution is to first take 200 mL glacial acetic acid, then add deionized water to make up to 400 mL and mix evenly, after cleaning, quickly rinse the surface of the sample with flowing cold water to remove the residual acetic acid solution, and the surface treatment is completed.

[0037] (3) Constant current density direct electroplating of nickel: first add 1 L of the nickel acetate solution prepared in step (1) to a 1 L electrolytic cell, then add 0.05 g of SDS and stir to dissolve, adjust the pH of the electroplating bath to 4.42, then place the anode plate and connect it to the anode, connect the plating piece to the cathode of the power supply, adjust the output current to be constant at 0.2 A (theoretical current density 0.76 A / dm 2 , 100% cathode efficiency), then turn on the DC power switch, immerse the sample completely in the electroplating bath under the power-on state, the electroplating time is 208 min, use a magnetic stirrer to slowly stir the electroplating bath during electroplating, the speed is adjusted to not appear bubbles, keep the solution temperature in the electroplating bath stable at 25 ℃, keep the pH in the electroplating bath less than 5.

[0038] (4) After step (3) is completed, take the sample out of the electroplating bath, then rinse it with deionized water and dry it, the target plated piece is obtained, the remaining electroplating solution can be filtered and recovered, adjust the pH to 4.42 for standby

[0039] (5) The nickel plating layer prepared in step (3) is subjected to plating layer quality inspection, including plating layer quality visual inspection and judging plating layer thickness and joint strength after diffusion welding with steel. Visual inspection is performed to check whether there is a significant crack or peeling and warping phenomenon. If no significant problem is found in visual inspection, the plating layer of the surface to be welded and the abutting steel block are polished to Ra less than 0.2 μm, and then are thoroughly cleaned before being subjected to hot pressure diffusion connection. The diffusion welding process is as follows: from room temperature, the temperature is increased to 1000 ℃ at a rate of 10 ℃ / min, then is kept for 1 h, while a pressure of 28 MPa is applied and kept for 1 h, then the pressure is removed, and then is cooled to 550 ℃ at a rate of 5 ℃ / min, then is kept for 1 h, and finally is furnace cooled. A dog bone shaped sample is taken, and the tensile strength of the joint is measured in an abutting manner. The interface morphology of the sample after welding is shown in Figure 2 (a), it can be seen that the plating layer is dense and uniform, and there is no significant hole. The average thickness is about 24 μm. The mechanical properties of the joint at room temperature are shown in Figure 4 . The tensile strength of the joint is about 381 MPa. Example

[0040] The other conditions are the same as in Example 1, except that the process conditions for direct electroplating of nickel at a constant current density are as follows: the SDS addition amount is 0.07 g / L, the pH of the electroplating bath is adjusted to 4.6 before electroplating, the electroplating time is 840 min, the current is 0.1 A (theoretical current density 0.38 A / dm 2 , 100% cathode efficiency), the sample is completely immersed in the electroplating bath under the condition of being electrified, a magnetic stirrer is slowly rotated during electroplating, and the solution temperature in the electroplating bath is kept stable at 25 ℃. The interface morphology of the sample after welding is shown in Figure 2 (b), it can be seen that the plating layer is dense and uniform, and there is no significant hole. The average thickness is about 43 μm. The mechanical properties at room temperature are shown in Figure 4 . The tensile strength of the joint is about 541 MPa. Example

[0041] The other conditions are the same as in Example 1, except that the process conditions for direct electroplating of nickel at a constant current density are as follows: the SDS addition amount is 0.05 g / L, the pH of the electroplating bath is adjusted to 4.42 before electroplating, the electroplating time is 1295 min, the current is 0.2 A (theoretical current density 0.76 A / dm 2 , 100% cathode efficiency), the sample is completely immersed in the electroplating bath under the condition of being electrified, a magnetic stirrer is slowly rotated during electroplating, and the solution temperature in the electroplating bath is kept stable at 27 ℃. The side surface morphology of the fracture of the steel side of the sample after welding is shown in Figure 2 (c), it can be seen that the plating layer is dense and uniform, and there is no significant hole. The average thickness is about 80 μm. The mechanical properties at room temperature are shown in Figure 4The tensile strength of the joint is about 444 MPa. Example 1

[0042] The other parameters are the same as in Example 1, except that the electrolyte is prepared directly from nickel acetate. The preparation method of the electrolyte is as follows: 24 g of nickel acetate tetrahydrate (at this time, the Ni 2+ concentration is about 5.6 g / L), 5 g of sodium chloride, and 0.05 g of SDS are placed in a beaker, and an appropriate amount of deionized water is added to dissolve them completely. Then, 8 ml of acetic acid is added, and water is added to make up to 1 L. After stirring, the pH is adjusted to 4.42 with glacial acetic acid, and the electrolyte is poured into an electrolysis tank with a capacity of 1 L. The side surface morphology of the sample after welding is shown in Figure 2 As shown in (d), the coating is dense and uniform, and there are no significant pores. The average thickness is about 17 μm, and the room temperature mechanical properties are as shown in Figure 4 The tensile strength of the joint is about 332 MPa, which is close to that of Example 1 but still has room for improvement. It may be necessary to adjust the process parameters accordingly. Example 1

[0043] The other conditions are the same as in Example 1, except that the process conditions for direct electroplating of nickel at a constant current density are as follows: the amount of SDS added is 0.05 g / L, the pH of the electroplating bath is adjusted to 4.56 before electroplating, the electroplating time is 3096 min, the current is 0.2 A (theoretical current density 0.76 A / dm 2 , 100% cathode efficiency), and the sample is completely immersed in the electroplating bath under the condition of being electrified. A magnetic stirrer is used to rotate slowly during electroplating, and the solution temperature in the electroplating bath is kept stable at 24 ℃. The interface microstructure of the sample after welding is shown in Figure 2 As shown in (e), the coating is dense and uniform, and there are no significant pores. The average thickness is about 184 μm, and the room temperature mechanical properties are as shown in Figure 4 The tensile strength of the joint is about 675 MPa. Example 1

[0044] The other conditions are the same as in Example 1, except that after the electrolyte is prepared, it is naturally volatilized to concentrate it. The actual concentration of Ni 2+ in the electrolyte is 7.905 g / L (atomic absorption spectrometry). The process conditions for direct electroplating of nickel at a constant current density are as follows: the amount of SDS added is 0.05 g / L, the pH of the electroplating bath is adjusted to 4.44 before electroplating, the electroplating time is 647 min, the current is 0.2 A (theoretical current density 0.76 A / dm 2 , 100% cathode efficiency), and the sample is completely immersed in the electroplating bath under the condition of being electrified. A magnetic stirrer is used to rotate slowly during electroplating, and the solution temperature in the electroplating bath is kept stable at 25 ℃. The interface morphology of the sample after welding is shown in Figure 2(f) shows that the plating layer is dense, uniform, and has no significant holes, with an average thickness of about 45 μm, and the room temperature mechanical properties are as shown in Figure 4 (f) shows that the plating layer is dense, uniform, and has no significant holes, with an average thickness of about 45 μm, and the room temperature mechanical properties are as shown in Example

[0045] Other conditions are the same as in Example 1, except that the electrolyte is naturally volatilized to concentrate after being prepared, and the Ni 2+ concentration is between 8-10 g / L, close to 10 g / L (standard colorimetric series is prepared by directly adding nickel acetate, and 2 g / L is taken as a scale, from 2 g / L to 16 g / L). The process conditions for direct plating of nickel at a constant current density are as follows: the SDS addition amount is 0.08 g / L, the plating bath pH is adjusted to 4.5 before plating, the plating time is 215 min, the current is 0.2 A (theoretical current density 0.76 A / dm 2 , 100% cathode efficiency), the sample is completely immersed in the plating bath under the power-on state, a magnetic stirrer is slowly rotated during plating to ensure that no bubbles are generated, and the solution temperature in the plating bath is kept stable at 25 °C. The sample interface morphology after welding is as shown in Figure 2 (f) shows that the plating layer is dense, uniform, and has no significant holes, with an average thickness of about 45 μm, and the room temperature mechanical properties are as shown in Figure 4 (f) shows that the plating layer is dense, uniform, and has no significant holes, with an average thickness of about 45 μm, and the room temperature mechanical properties are as shown in Example

[0046] In this example, the sample is a sample with a hole and external threads, the inner hole is 10 mm, the outer diameter is 30 mm, the height is 13 mm, the external threads are 55° triangular threads, the pitch is 2 mm, and the depth is 2 mm. The process conditions for direct plating of nickel at a constant current density are as follows: the SDS addition amount is 0.05 g / L, the plating bath pH is adjusted to 4.2 before plating, the plating time is 180 min, the current is 0.2 A (theoretical current density 0.76 A / dm 2 , 100% cathode efficiency), the sample is completely immersed in the plating bath under the power-on state, a magnetic stirrer is slowly rotated during plating to ensure that no bubbles are generated, and the solution temperature in the plating bath is kept stable at 25 °C, and other steps are the same as in Example 1. The sample appearance is as shown in Figure 3 (f) shows that the plating layer is dense, uniform, and has no significant holes, with an average thickness of about 45 μm, and the room temperature mechanical properties are as shown in

[0047] (1) Electrolytic preparation of nickel acetate plating solution: first, weigh 5 g of sodium chloride and dissolve it in a small amount of deionized water, then mix 25 mL of glacial acetic acid with it and stir until homogeneous, dilute the mixture to 1 L, then pour the mixture into the electroplating tank; use electrolytic nickel plate (purity > 99.5%) as anode and cathode to carry out electrolysis at room temperature, electrolysis current 2 A, electrolysis time 325 min, after electrolysis, filter the plating solution and reserve it for later use.

[0048] (2) Tungsten alloy surface pretreatment: select a 93W-4.9Ni-2.1Fe tungsten alloy test block with a diameter of 30 mm and a height of 13 mm, turn the entire cylindrical surface and one end surface to expose the fresh surface, and use a grinder to grind the other end to Ra 0.8 μm, then place the sample on the hanger, immerse the sample in anhydrous ethanol (purity 99.5%) and ultrasonic clean, anhydrous ethanol temperature 30°C, ultrasonic cleaning time 5 min, after cleaning, rinse the sample thoroughly with clean anhydrous ethanol and immerse it in an acetic acid aqueous solution, acetic acid aqueous solution concentration 50% vol, first take 200 mL of glacial acetic acid, then add deionized water to make up to 400 mL and mix well, then immerse the sample in the acetic acid aqueous solution at 30°C and clean it with an ultrasonic cleaner for 5 min, after cleaning, rinse the sample surface with flowing cold water to remove residual acetic acid solution, and the surface treatment is complete.

[0049] (3) Constant current density direct plating of nickel: first, add 1 L of the nickel acetate solution prepared in step (1) to a 1 L electrolytic tank, then add 0.05 g of SDS and stir to dissolve, adjust the pH of the plating bath to 4.42, then place the anode plate and connect it to the anode, then connect the plating piece to the cathode of the power supply, adjust the output current to be constant at 0.2 A (theoretical current density 0.76 A / dm 2 , 100% cathode efficiency), then turn on the DC power switch, immerse the sample completely in the plating bath under power, the plating time is 208 min, use a magnetic stirrer to rotate slowly during plating, make sure there are no bubbles, keep the temperature of the solution in the plating bath stable at 25°C, and keep the pH in the plating bath less than 5.

[0050] (4) After step (3) is completed, remove the sample from the plating bath, then rinse it thoroughly with deionized water and dry it, the target plating piece is obtained, the remaining plating solution can be filtered and recovered, adjust the pH to 4.42 and reserve it for later use;

[0051] (5) The nickel plating layer prepared in step (3) is subjected to plating layer quality inspection, including plating layer quality visual inspection and judging plating layer thickness and joint strength after diffusion welding with steel. Visual inspection is performed to check whether there are significant cracks or peeling and warping phenomena. If no significant problems are found in visual inspection, the plating layer of the surface to be welded and the abutting steel block are polished to Ra less than 0.2 μm, and then are thoroughly washed before being subjected to hot-press diffusion connection. The diffusion welding process is as follows: from room temperature, the temperature is raised to 1000 ℃ at a rate of 10 ℃ / min, then is kept for 1 h, while a pressure of 28 MPa is applied and kept for 1 h, then the pressure is removed, and then is cooled to 550 ℃ at a rate of 5 ℃ / min, then is kept for 1 h, and finally is furnace-cooled. A dog bone-shaped sample is taken, and the tensile strength of the joint is measured in an abutting manner. The visual inspection result is as follows: Figure 4 (a) As shown, due to the low surface machining quality, the surface still has scratches, which reduces the bonding ability of the plating layer and the substrate, and the tungsten alloy is not cleaned with a hot detergent solution, so it is difficult to fully remove the oil stains and thin-layer oxides on the surface of the tungsten alloy, resulting in failure of electroplating.

[0052] (1) Electrolytic preparation of nickel acetate plating solution: first, 5 g of sodium chloride is dissolved in a small amount of deionized water, then 25 mL of glacial acetic acid is measured and mixed with it and stirred uniformly, and the mixed solution is diluted to 1 L with deionized water, then the mixed solution is poured into the electroplating tank; an electrolytic nickel plate (purity above 99.5%) is used as the anode and cathode to perform electrolysis at room temperature, the electrolysis current is 2 A, the electrolysis time is 325 min, and after electrolysis, the electrolyte is filtered and reserved.

[0053] (2) Tungsten alloy surface pretreatment: a 93W-4.9Ni-2.1Fe tungsten alloy test block with a diameter of 30 mm and a height of 13 mm is selected, the entire cylindrical surface and one end surface are turned to expose fresh surfaces, and the other end surface is polished to Ra less than 0.2 μm, then the sample is installed on a hanger, first cleaned with hot water, the hot water temperature is 90 ℃, the washing-up liquid addition amount is 10 g / L, the sample is completely immersed in the hot water, ultrasonic cleaning for 5 min, then the surface residual detergent is thoroughly washed with flowing cold water; then the sample is immersed in anhydrous ethanol (purity 99.5%) for ultrasonic cleaning, the anhydrous ethanol temperature is 30 ℃, the ultrasonic cleaning time is 5 min, after cleaning, the sample is thoroughly washed with clean anhydrous ethanol and then immersed in an acetic acid aqueous solution for ultrasonic cleaning, the acetic acid aqueous solution concentration is 50%vol, 200 mL of glacial acetic acid is measured first, then deionized water is added to make up to 400 mL, then the sample is immersed in the acetic acid aqueous solution at 30 ℃ for ultrasonic cleaning for 5 min, after cleaning, the sample is quickly and thoroughly washed with flowing cold water to remove the residual acetic acid solution on the surface, and the surface treatment is completed.

[0054] (3) Constant current density direct electroplating nickel: first add 1 L of nickel acetate solution prepared in step (1) into an electrolytic cell with a capacity of 1 L, then add 0.07 g of SDS and fully stir to dissolve, adjust the pH of the electroplating cell to 4.40, then put the anode plate first and connect it to the anode, then connect the plating piece to the cathode of the power supply, adjust the output current to be constant at 0.35 A (theoretical current density 1.32 A / dm 2 , 100% cathode efficiency) and turn on the DC power supply switch, fully immerse the sample in the electroplating cell under power-on state, the electroplating time is 217 min, use a magnetic stirrer to rotate slowly during electroplating, and the solution temperature in the electroplating cell is kept stable at 27 ℃, and the pH in the electroplating cell is kept less than 5.

[0055] (4) After step (3) is completed, the sample is taken out of the electroplating cell, then it is washed with deionized water and dried, and the target plated piece is obtained, the remaining electroplating solution can be filtered and recovered, and the pH is adjusted to 4.42 for standby;

[0056] (5) The plating quality of the nickel plating layer prepared in step (3) is inspected, including visual inspection of the plating quality and judgment of the plating layer thickness and joint strength after diffusion welding with steel. Visual inspection is performed to check whether there are significant cracks or peeling and warping, if no significant problems are found in visual inspection, the plating layer on the surface to be welded and the steel block to be butt-jointed are polished to Ra less than 0.2 μm, then they are thoroughly cleaned and hot-pressed diffusion jointing is used, the diffusion welding process is as follows: from room temperature, the temperature is raised to 1000 ℃ at a rate of 10 ℃ / min, then kept for 1 h, at the same time, a pressure of 28 MPa is applied and kept for 1 h, then the pressure is removed, and the temperature is cooled to 550 ℃ at a rate of 5 ℃ / min, then kept for 1 h, and finally furnace-cooled, a dog bone-shaped sample is taken, and the tensile strength of the joint is measured in a butt-jointed manner. The visual inspection result is shown in Figure 4 (b) as shown, due to the high current density and poor electrical conductivity of the tungsten alloy itself, the plating layer is significantly thickened at the edge, the stress is concentrated, the plating layer is cracked, and the electroplating fails.

[0057] (1) Electrolytic preparation of nickel acetate electroplating solution: first, weigh 5 g of sodium chloride and dissolve it in a small amount of deionized water, then mix 25 mL of glacial acetic acid with it and stir evenly, dilute the mixed solution to 1 L with deionized water, and then pour the mixed solution into the electroplating cell; use an electrolytic nickel plate (purity above 99.5%) as anode and cathode to perform electrolysis at room temperature, electrolysis current is 2 A, electrolysis time is 325 min, after electrolysis, the electrolyte is filtered and reserved for standby.

[0058] (2) Tungsten alloy surface pretreatment: A 93W-4.9Ni-2.1Fe tungsten alloy test block with a diameter of 30 mm and a height of 13 mm is selected. The entire cylindrical surface and one end surface are turned to expose the fresh surface, and the other end surface is polished to Ra less than 0.2 μm. Then the sample is installed on the hanger, immersed in anhydrous ethanol (purity 99.5%) for ultrasonic cleaning, the anhydrous ethanol temperature is 30℃, the ultrasonic cleaning time is 5 min, after cleaning, the sample is washed with clean anhydrous ethanol and then immersed in acetic acid solution for ultrasonic cleaning. The concentration of acetic acid solution is 50% vol. First, 200 mL of glacial acetic acid is measured, then deionized water is added to make up to 400 mL, then the sample is immersed in the ultrasonic machine at 30℃ for 5 min. After cleaning, the sample is quickly washed with flowing cold water to remove the residual acetic acid solution on the surface. The surface treatment is completed.

[0059] (3) Constant current density direct electroplating of nickel: First, add 1 L of the nickel acetate solution prepared in step (1) to a 1 L electrolytic cell, adjust the pH of the electroplating bath to 4.0, then place the anode plate and connect it to the anode, then connect the plating piece to the cathode of the power supply, adjust the output current to be constant at 0.2 A (theoretical current density 0.76 A / dm 2 , 100% cathode efficiency), then turn on the DC power switch, immerse the sample completely in the electroplating bath under power-on state, the electroplating time is 236 min, use a magnetic stirrer to rotate slowly during electroplating, the rotation speed is adjusted to ensure that no bubbles appear, keep the solution temperature in the electroplating bath stable at 22℃, and keep the pH in the electroplating bath less than 5.

[0060] (4) After step (3) is completed, the sample is taken out of the electroplating bath, then washed with deionized water and dried, the target plated piece is obtained, the remaining electroplating solution can be filtered and recycled, adjust the pH to 4.42 for standby;

[0061] (5) The nickel plating layer prepared in step (3) is subjected to plating layer quality inspection, including plating layer quality visual inspection and judging plating layer thickness and joint strength after diffusion welding with steel. Visual inspection is performed to check whether there is a significant crack or peeling and warping phenomenon, if no significant problem is found in visual inspection, the plating layer of the surface to be welded and the butt joint steel block are polished to Ra less than 0.2 μm, then after being washed thoroughly, hot pressure diffusion connection is used, the diffusion welding process is as follows: from room temperature, the temperature is increased to 1000 ℃ at a rate of 10 ℃ / min, then kept for 1 h, at the same time, 28 MPa pressure is added and kept for 1 h, then the pressure is removed, and then cooled to 550 ℃ at a rate of 5 ℃ / min, then kept for 1 h, and finally furnace cooling, the dog bone-shaped sample is taken, the tensile strength of the joint is measured in a butt joint manner. Due to insufficient cleaning of the sample in the early stage, the initial pH of electroplating is too low, and SDS is not added as an anti-pinhole agent, a large amount of hydrogen is precipitated on the surface during electroplating, leaving a large number of pits and shallow grooves on the plating layer, and the overall plating layer also shows an orange peel pattern with unevenness, the plating layer quality is too poor to meet the needs of diffusion welding.

[0062] (1) Nickel acetate electroplating solution is prepared using nickel acetate tetrahydrate: first, 5 g of sodium chloride and 64 g of nickel acetate tetrahydrate are weighed and dissolved in a small amount of deionized water, deionized water is added to dilute the mixed solution to 1 L, then glacial acetic acid is used to adjust the pH to 4.5, and then the mixed solution is reserved for later use, at this time the Ni 2+ concentration in the solution is about 15 g / L

[0063] (2) Tungsten alloy surface pretreatment: a 93W-4.9Ni-2.1Fe tungsten alloy test block with a diameter of 30 mm and a height of 13 mm is selected, the entire cylindrical surface and one end surface are turned to expose fresh surfaces, and the other end surface is polished to Ra less than 0.2 μm, then the sample is installed on the hanger, the sample is immersed in anhydrous ethanol (purity 99.5%) for ultrasonic cleaning, the anhydrous ethanol temperature is 30 ℃, the ultrasonic cleaning time is 5 min, after cleaning, the sample is washed thoroughly with clean anhydrous ethanol and then immersed in an acetic acid aqueous solution for ultrasonic cleaning, the acetic acid aqueous solution has a concentration of 50% vol, 200 mL of glacial acetic acid is measured, then deionized water is added to make up to 400 mL, then the sample is immersed in the acetic acid aqueous solution at 30 ℃ for 5 min using an ultrasonic cleaner, after cleaning, the sample is washed thoroughly with flowing cold water to remove residual acetic acid solution on the surface, and the surface treatment is completed.

[0064] (3) Constant current density direct electroplating of nickel: first, 1 L of the nickel acetate solution prepared in step (1) is added to an electrolytic cell with a capacity of 1 L, then 0.05 g of SDS is added and dissolved by stirring, the plating bath pH is adjusted to 4.50, then the anode plate is placed first and connected to the anode, then the plating piece is connected to the cathode of the power supply, the output current is adjusted to be constant at 0.2 A (theoretical current density 0.76 A / dm2 After the open-circuit potential reaches the steady state (100% cathode efficiency), the direct current switch is turned on, the sample is fully immersed in the plating bath under the power on state, the plating time is 540 min, a magnetic stirrer is used to rotate slowly during the plating, the rotation speed is adjusted to ensure that no bubbles appear, the temperature of the solution in the plating bath is kept stable at 27 °C, and the pH in the plating bath is kept less than 5.

[0065] (4) After step (3) is completed, the sample is taken out of the plating bath, then it is washed with deionized water and dried, and the target plated part is obtained, the remaining plating solution can be filtered and recovered, and the pH is adjusted to 4.42 for standby;

[0066] (5) The quality of the nickel plating layer prepared in step (3) is inspected, including visual inspection of the plating layer quality and joint strength after diffusion welding with steel. Visual inspection is performed to check whether there are significant cracks or peeling and warping phenomena. If no significant problems are found in the visual inspection, the plated layer on the surface to be welded and the butt joint steel block are polished to Ra less than 0.2 μm, then they are thoroughly cleaned and then subjected to hot pressure diffusion bonding. The diffusion welding process is as follows: from room temperature, the temperature is increased to 1000 °C at a rate of 10 °C / min, then it is kept for 1 h, at the same time, a pressure of 28 MPa is applied and kept for 1 h, then the pressure is removed, and then it is cooled to 550 °C at a rate of 5 °C / min, then it is kept for 1 h, and finally it is furnace cooled. Dog bone-shaped samples are taken, and the tensile strength of the joint is measured in a butt joint manner. Due to the high concentration of the solution, the conductivity is too good, the plating deposition rate is too fast, and significant current density concentration occurs at the edge of the tungsten alloy sample, resulting in excessive stress of the plating layer, which is difficult to adhere to the surface of the substrate, and the whole plating layer falls off, resulting in plating failure. 2+ high, the conductivity is too good, the plating deposition rate is too fast, and significant current density concentration occurs at the edge of the tungsten alloy sample, resulting in excessive stress of the plating layer, which is difficult to adhere to the surface of the substrate, and the whole plating layer falls off, resulting in plating failure.

Claims

1. A method for direct plating of thick nickel on tungsten alloy surface, characterized by, Comprising the following steps: Step one tungsten alloy surface pretreatment Tungsten alloy surface using mechanical processing to remove the oxide layer, and then polishing treatment to the surface of the fresh metal to be plated, plated surface roughness less than Ra0.2 μm; then using detergent + hot water, ethanol, acetic acid in turn cleaning; get clean after the plated sample; Using the process of ultrasonic cleaning of detergent + hot water, ethanol, acetic acid in turn: hot water wash using commercially available alkaline detergent with hot water, detergent addition amount of 5-15 g / L, hot water temperature 85-100 ℃, first the detergent is dissolved in hot water after the sample immersed in the ultrasonic cleaning, cleaning time 5-10 min, cleaning times 1-2 times; then the sample using the flow of cold water to rinse the surface of the residual detergent after immersion in the purity of 99.5% above anhydrous ethanol ultrasonic cleaning, anhydrous ethanol temperature 20-50 ℃, cleaning time 5-10 min, cleaning times 1-2 times; then the sample using the flow of anhydrous ethanol to rinse after put into acetic acid solution ultrasonic cleaning, acetic acid aqueous solution concentration of 40-60% vol, first the glacial acetic acid is dissolved in deionized water after stirring evenly after the sample immersed, ultrasonic cleaning time 5-10 min, cleaning temperature is 20-50 ℃, cleaning after quickly using the flow of cold water to rinse the surface of the residual acetic acid solution, surface treatment is completed; Step two electroplating nickel First in the electroplating tank is added nickel acetate electroplating solution, then add sodium dodecyl sulfate and fully dissolved, the amount of sodium dodecyl sulfate is added to 0.04-0.1 g / L, and adjust the pH of the electroplating bath to between 3.5-5.5, the anode uses electrolytic nickel plate, connected to the positive pole of the power supply, the sample to be plated is connected to the negative pole of the power supply, the power is turned on, the target current density is set to 0.3-1.1 A / dm 2 , the electroplating is started; the initial concentration of sodium chloride in the nickel acetate electroplating solution is 3-14 g / L, the initial concentration of glacial acetic acid is 5-25 ml / L, and the pH of the electroplating bath is adjusted to between 3.5-5.5, the initial concentration of Ni 2+ ions is 5-10 g / L; The preparation of nickel acetate electroplating solution by electrolysis method; The preparation of nickel acetate electroplating solution by electrolysis method includes: first using sodium chloride, glacial acetic acid and water to prepare the solution, wherein the concentration of sodium chloride is 3-14 g / L, the concentration of glacial acetic acid is 15-30 mL / L, then using electrolytic nickel plate as anode and cathode to electrolyze, electrolyze to the concentration of Ni ion in the solution is 5-10 g / L.

2. A method of direct plating of thick nickel on tungsten alloy surfaces as claimed in claim 1, wherein: The tungsten alloy surface pretreatment includes: using sand blasting, turning, polishing to remove the obvious oxide layer on the surface of tungsten alloy.

3. The method of claim 1 wherein: The initial concentration of sodium chloride in the nickel acetate electroplating solution is 4-8 g / L, and the pH of the electroplating bath is adjusted to 4.2-4.

6.

4. The method of claim 1 wherein: The process conditions for the constant current density direct current nickel plating are: current density is 0.3-1.1 A / dm 2 , plating time is up to 10 h or more according to thickness requirement, plating solution temperature is less than or equal to 30 degrees Celsius, and the plating solution is stirred by using mechanical stirring, magnetic stirring, air flow stirring or direct moving sample method.

5. The method of claim 4 wherein: The current density is 0.4-0.9 A / dm 2 .

6. The method of claim 5 wherein the tungsten alloy surface is directly plated with a thick layer of nickel. The current density is 0.57-0.76 A / dm 2 .

7. The method for directly plating thick nickel on the surface of tungsten alloy according to claim 1, characterized in that: After electroplating, the sample is taken out of the electroplating bath, rinsed with water and dried, and the target plated part is obtained. The remaining electroplating solution is filtered and recovered, and the pH is adjusted for later use in the preparation of nickel acetate electroplating solution by electrolysis method.

8. The method of claim 1 wherein: the tungsten alloy surface is directly plated with a thick layer of nickel. Electroplating for 208 min obtains a plated layer with a thickness of 24-25 μm; electroplating for 1295 min obtains a plated layer with a thickness of more than or equal to 80 μm.

9. The method for directly plating thick nickel on the surface of tungsten alloy according to claim 1, characterized in that: The quality of the nickel plated layer is inspected, including visual inspection of the plated layer quality and judgment of the plated layer thickness and joint strength after diffusion welding with steel; The diffusion bonding and testing conditions are as follows: the plated surface of the to-be-bonded steel block and the abutting steel block are polished to Ra less than 0.2 μm, then cleaned thoroughly, and then diffusion bonded by hot pressing or hot isostatic pressing, with a diffusion bonding temperature of 900-1000 ℃, a welding pressure of 10-40 MPa and 50-200 MPa, and the joint is evaluated in terms of tensile strength.

Images