A plating solution and a method for preparing an ultra-high strength mixed microstructure nickel coating using the plating solution.

Abstract

This invention discloses a plating solution and a method for preparing ultra-high strength nickel coatings with a mixed microstructure using the plating solution. The plating solution consists of a solvent and nickel sulfate, nickel chloride, boric acid, and sodium dodecyl sulfate dissolved in the solvent, with a nickel chloride concentration of 0.5–10 g / L. This invention utilizes the non-uniform diffusion, nucleation, and crystal growth induced by chloride ion depletion in the plating solution to prepare high-quality, ultra-high strength nickel coatings with a mixed microstructure. This overcomes the limitations of existing electrodeposited nickel coating strengthening technologies and effectively solves the problem of difficulty in controlling the microstructure and strength of traditional additive-free electroplated nickel coatings. It provides technical support for designing and preparing high-performance, novel microstructure nickel metal or alloy coating materials.

Description

Technical Field

[0001] This invention relates to the field of coating preparation technology, and in particular to a plating solution and a method for preparing an ultra-high strength mixed microstructure nickel coating using the plating solution. Background Technology

[0002] Electrochemical deposition of nickel metal and its alloy coatings typically exhibits excellent mechanical properties and corrosion resistance, making them widely used in precision electronic components, aerospace parts, mold manufacturing, and surface protection. How to effectively control the microstructure of nickel metal / alloys through electrochemical deposition processes to further enhance the mechanical properties of coating materials has always been a research hotspot and technological pursuit in this field.

[0003] Currently, the main technical approaches for preparing high-strength nickel metal / alloy coatings by electrochemical deposition fall into two categories: First, post-treatment of the electrodeposited metal / alloy involves plastic deformation, such as cold rolling or shot peening, to introduce dislocations and substructures into the material's microstructure to optimize mechanical properties. Second, adding grain refiners to the base Watt's plating bath, such as organic or inorganic additives like saccharin, 2-butynedi-1,4-diol, thiourea, and their derivatives. The adsorption effect of these additives effectively inhibits grain growth during electroplating, resulting in finer grains and improved material strength. However, both approaches have certain limitations: While post-plastic deformation treatment methods can significantly improve the strength of materials, they increase production processes, energy consumption, and time costs, and may alter the size or shape of the base workpiece.

[0004] Adding grain refiners to the plating bath introduces additional impurities (such as sulfur and phosphorus), which deteriorates the toughness, conductivity, or corrosion resistance of the prepared coating material. Furthermore, the use of additives narrows the electrochemical deposition process window, increases the complexity of the plating bath composition, and raises maintenance costs. Additionally, the basic Watt's plating bath contains a high concentration of chloride ions (30-60 g / L nickel chloride), whose main function is to promote anodic nickel dissolution, improve the plating bath conductivity, reduce anodic polarization, and ensure uniform crystallization. However, without additives, the high-concentration chloride ion Watt's plating bath can only produce nickel metal / alloy coatings with coarse grains and a simple microstructure, whose strength level is often within the conventional range (microhardness approximately 250 HV), making it difficult to achieve breakthrough improvements. Summary of the Invention

[0005] The main objective of this invention is to provide an electrochemical deposition method that can directly produce high-quality, ultra-high-strength nickel coatings without the need for grain refiners.

[0006] To achieve the above objectives, the present invention provides a plating solution for electrochemical deposition of nickel metal or nickel alloy coatings, comprising a solvent and nickel sulfate, nickel chloride, boric acid and sodium dodecyl sulfate dissolved in the solvent, wherein the concentration of nickel chloride is 0.5-10 g / L.

[0007] Furthermore, the solvent is water.

[0008] Furthermore, the concentration of nickel sulfate is 280–320 g / L, the concentration of boric acid is 40–50 g / L, and the concentration of sodium dodecyl sulfate is 0.15–0.35 g / L.

[0009] The present invention also provides a method for preparing an ultra-high strength mixed structure nickel coating by electrochemical deposition, wherein a high-purity nickel foil is used as the anode and a metal substrate is used as the cathode, and electrochemical deposition is performed in the above-mentioned plating solution to obtain the ultra-high strength mixed structure nickel coating.

[0010] Furthermore, the mixed microstructure includes equiaxed ultrafine grains and columnar coarse grains.

[0011] Furthermore, the current density for electrochemical deposition is 30–70 mA / cm². 2 .

[0012] Furthermore, the bath temperature for electrochemical deposition is 55–70°C.

[0013] Furthermore, the stirring rate for electrochemical deposition is 800–1100 rpm.

[0014] The design principle of the present application is: During their research, the inventors accidentally discovered that by using an unconventional plating solution containing low concentrations of chloride ions, high-quality, ultra-high-strength nickel coatings could be directly produced without the addition of grain refiners. The principle behind this is that the extremely low nickel chloride content in the plating solution leads to a lack of chloride ions during electrodeposition, resulting in a non-uniform current spatial distribution between the anode and cathode. Furthermore, the interaction between the local environment and ion migration causes nickel ion transport and diffusion to be in a metastable state. Under the control of a series of non-equilibrium kinetic processes, this ultimately induces non-uniform nucleation and growth of metallic nickel on the cathode surface, forming a nickel coating with a mixed microstructure of numerous equiaxed ultrafine grains and a small amount of columnar coarse grains. This type of nickel coating has high quality, is free of defects such as pores and cracks, has uniform thickness, low macroscopic tensile stress, and exhibits ultra-high strength.

[0015] The beneficial effects of the present application are embodied in: The plating solution and method provided by this invention, for the first time, utilize the non-uniform diffusion, nucleation, and crystal growth induced by chloride ion deficiency in the plating solution to prepare a high-quality, ultra-high-strength nickel coating with a mixed microstructure. This breaks through the limitations of existing electrodeposited nickel coating strengthening technologies and effectively solves the problem of difficulty in controlling the microstructure and strength of traditional additive-free electroplated nickel coatings. It provides technical support for the design and preparation of high-performance nickel metal or alloy coating materials with novel microstructures. Compared with existing technologies, this invention has the following advantages: (1) This invention is pure and additive-free, and the process is simple and direct. It breaks through the limitations of existing nickel coating strengthening technology based on the addition of grain refiners, and solves the problems of large grains, simple microstructure and difficulty in further improving the strength of traditional additive-free electrodeposited nickel coatings.

[0016] (2) The present invention saves the complex process and high cost of traditional methods that rely on additives or post-processing techniques.

[0017] (3) This invention broadens the controllable window of the microstructure and properties of nickel coatings, providing important technical guidance for the flexible design and creation of high-performance nickel metal and alloy materials. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the electrochemical deposition process for preparing an ultra-high strength hybrid microstructure nickel coating according to the present invention; Figure 2 The microstructure characteristics of the nickel coating obtained in Example 1 are shown in the electron backscatter diffraction diagram. Figure 3 The microstructure characteristics of the nickel coating obtained in Example 2 are shown in the electron backscatter diffraction diagram. Figure 4 The microstructure characteristics of the nickel coating obtained in Example 3 are shown in the electron backscatter diffraction diagram. Figure 5 This is a microstructure diagram of the nickel coating obtained in Comparative Example 1 under electron backscatter diffraction.

[0019] Explanation of markings in the diagram: 1—Electrochemical deposition tank; 2—Plastering solution; 3—High-purity nickel foil; 4—Metal substrate; 5—Electroplating power source; 6—Non-uniform nucleation and growth; 7—Nickel coating. Detailed Implementation

[0020] To enable those skilled in the art to more clearly understand the technical solutions described in this invention, the following embodiments are provided for illustration. It should be noted that the following embodiments do not constitute a limitation on the scope of protection claimed by this invention.

[0021] Unless otherwise specified, the raw materials, reagents or devices used in the following embodiments can be obtained from conventional commercial sources or by existing known methods; unless otherwise specified, the methods used in the embodiments of the present invention are methods mastered by those skilled in the art.

[0022] The present invention prepares ultra-high strength hybrid microstructure nickel coatings by electrochemical deposition. Figure 1 The facility shown implements a plating solution 2 containing a small amount of chloride ions in an electrochemical deposition tank 1. A large-area high-purity nickel foil 3 serves as the anode, and a metal substrate 4 as the cathode. A constant current output from an electroplating power supply 5 promotes the heterogeneous nucleation and growth 6 of nickel on the cathode surface, ultimately forming a high-quality nickel coating 7 with ultra-high strength and a mixed microstructure. Specific examples are as follows: Example 1 Electrochemical deposition of ultra-high strength mixed structure nickel coating (1) Under constant temperature of 50°C and stirring at 800 rpm, analytical grade nickel sulfate (Aladdin, item number N100215), nickel chloride (Aladdin, item number N434171), boric acid (Aladdin, item number B111605) and sodium dodecyl sulfate (Aladdin, item number S108347) were dissolved in deionized water to prepare a chloride ion-deficient plating solution with a concentration of 300 g / L nickel sulfate, 0.5 g / L nickel chloride, 45 g / L boric acid and 0.25 g / L sodium dodecyl sulfate.

[0023] (2) Fill the electrochemical deposition tank (15cm long × 15cm wide × 20cm high) with 3L of plating solution, and pour the solution at a depth of 5cm. 2 High-purity nickel foil (purity > 99.9%) with a surface area of ​​1 cm is used as the anode. 2 A Ni-W-Cr alloy substrate (Shanghai Institute of Applied Physics, Chinese Academy of Sciences, grade GH3539) with a surface area of ​​10 cm was used as the cathode, and the electrochemical deposition parameters were set to 50 mA / cm². 2 Constant current density, constant temperature of 65°C, stirring speed of 900 rpm, and deposition time of 3 hours. After deposition, the cathode with nickel coating was immediately immersed in a flowing ultrapure water bath and ultrasonically cleaned for 1 minute to remove residual electrolyte.

[0024] Example 2 Electrochemical deposition of ultra-high strength mixed structure nickel coating The preparation method in this embodiment is basically the same as in Example 1, except that the concentration of nickel chloride in the plating solution is adjusted to 5 g / L.

[0025] Example 3 Electrochemical deposition of ultra-high strength mixed structure nickel coating The preparation method in this embodiment is basically the same as in Example 1, except that the concentration of nickel chloride in the plating solution is adjusted to 10 g / L.

[0026] Comparative Example 1 Electrochemical deposition of nickel coating with rich chloride ions in plating solution The preparation method of this comparative example is basically the same as that of Example 1, except that the concentration of nickel chloride in the plating solution is adjusted to 30 g / L, that is, it is replaced with a plating solution rich in chloride ions.

[0027] Experimental Example 1 Analysis of the structure of the nickel coating The microstructures of the nickel coatings obtained in Examples 1-3 and Comparative Example 1 are as follows: Figures 2-5 As shown.

[0028] As can be seen, the nickel coatings prepared from chloride-deficient plating solutions all exhibit mixed microstructure characteristics. Specifically, the nickel coating obtained in Example 1 consists of 94.1% equiaxed ultrafine grains with a grain size <1 μm and a 5.9% columnar coarse grain structure with a grain size of 1-26.5 μm. The average grain size is 0.46 μm. (See [link to example]). Figure 2 The microstructure of the nickel coating obtained in Example 2 consists of 94.3% equiaxed ultrafine grains with a grain size <1 μm and 5.7% columnar coarse grains with a grain size of 1-20.5 μm. The average grain size is 0.47 μm. See [link to relevant documentation]. Figure 3 The microstructure of the nickel coating obtained in Example 3 consists of 91.0% equiaxed ultrafine grains with a grain size <1 μm and 9.0% columnar coarse grains with a grain size of 1-14.0 μm. The average grain size is 0.55 μm. See [link to example]. Figure 4 In contrast, the chloride-rich plating solution, i.e., the nickel coating prepared in Comparative Example 1, exhibits a uniform microstructure, composed of single, coarse columnar crystals with an average grain size of 1.3 μm, which is 2.4-2.8 times the average grain size of the mixed-structure nickel coating. (See [reference]). Figure 5 .

[0029] In addition, no defects such as pores or cracks were found in the mixed microstructure nickel coatings obtained in Examples 1-3 and the uniform microstructure nickel coatings obtained in Comparative Example 1, and the thickness was uniform.

[0030] Experimental Example 2 Stress and strength detection of the nickel coating Macroscopic stress and strength tests were performed on the nickel coatings obtained in each embodiment and comparative example.

[0031] Macroscopic stress was detected using X-ray sinusoidal radiation.2 The ψ method (GB / T 7704-2017 Nondestructive Testing X-ray Stress Measurement Method) was used under the following conditions: Mn target, wavelength 2.10314 Å, tube current 2 mA, tube voltage 20 kV, spot diameter 2 mm, ψ range -45-45°, face-centered cubic structure, Ni (311) diffraction crystal plane.

[0032] The strength was tested using the indentation characterization method (GB / T 9790-2021 "Vickers and Knoop Microhardness Tests for Metallic Materials and Other Inorganic Coatings"), i.e. Vickers microhardness analysis. The test conditions were: a square pyramidal diamond indenter, room temperature, a load of 300g, and a holding time of 15s.

[0033] The test results are as follows: The nickel coating in Example 1 has a macroscopic tensile stress of +12 MPa and a Vickers microhardness of 270 HV.

[0034] The nickel coating in Example 2 has a macroscopic tensile stress of +27 MPa and a Vickers microhardness of 366 HV.

[0035] The nickel coating in Example 3 has a macroscopic tensile stress of +33 MPa and a Vickers microhardness of 300 HV.

[0036] The macroscopic tensile stress of the nickel coating in Comparative Example 1 was +72 MPa, and the Vickers microhardness was 246 HV.

[0037] It can be seen that the mixed-structure nickel coatings obtained in Examples 1-3 are basically in a zero-stress state (≤35MPa), while the macroscopic tensile stress of the uniform-structure nickel coating obtained in Comparative Example 1 is as high as +72MPa. In addition, the mixed-structure nickel coatings of Examples 1-3 have excellent resistance to indentation, and their hardness can reach up to 1.5 times that of the uniform-structure nickel coating of Comparative Example 1.

[0038] In addition, the inventors conducted experiments on the electrochemical deposition effects of nickel coatings prepared by plating solutions with different chloride ion concentrations. The results showed that, based on Example 1, when the concentration of nickel chloride was adjusted to less than 0.5 g / L while other factors remained unchanged, the resulting nickel coating still exhibited a mixed structure, but its hardness decreased significantly. When the concentration of nickel chloride was adjusted to greater than 10 g / L while other factors remained unchanged, with increasing chloride ion concentration, the mixed characteristics of the nickel coating's structure gradually became less pronounced, and the hardness also decreased significantly, until at a concentration of 30 g / L, the mixed structure was completely absent. For the sake of brevity, detailed experimental procedures are not provided here.

[0039] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A plating solution for electrochemical deposition of nickel metal or nickel alloy coatings, characterized in that, It consists of a solvent and nickel sulfate, nickel chloride, boric acid and sodium dodecyl sulfate dissolved in the solvent, wherein the concentration of nickel chloride is 0.5 to 10 g / L.

2. The plating bath for electrochemical deposition of nickel metal or nickel alloy coatings as described in claim 1, characterized in that, The solvent is water.

3. The plating bath for electrochemical deposition of nickel metal or nickel alloy coatings as described in claim 1 or 2, characterized in that, The concentration of nickel sulfate is 280–320 g / L, the concentration of boric acid is 40–50 g / L, and the concentration of sodium dodecyl sulfate is 0.15–0.35 g / L.

4. A method for preparing an ultra-high strength hybrid microstructure nickel coating by electrochemical deposition, characterized in that, Using high-purity nickel foil as the anode and a metal substrate as the cathode, electrochemical deposition is performed in the plating solution as described in claim 1, 2, or 3 to obtain the ultra-high strength mixed structure nickel coating.

5. The method for preparing ultra-high strength hybrid microstructure nickel coating by electrochemical deposition as described in claim 4, characterized in that, The mixed microstructure includes equiaxed ultrafine grains and columnar coarse grains.

6. The method for preparing ultra-high strength hybrid microstructure nickel coating by electrochemical deposition as described in claim 4 or 5, characterized in that, The current density for electrochemical deposition is 30–70 mA / cm². 2 .

7. The method for preparing ultra-high strength hybrid microstructure nickel coating by electrochemical deposition as described in claim 4 or 5, characterized in that, The bath temperature for electrochemical deposition is 55–70°C.

8. The method for preparing ultra-high strength hybrid microstructure nickel coating by electrochemical deposition as described in claim 4 or 5, characterized in that, The stirring rate for electrochemical deposition is 800–1100 rpm.

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