Ni-Cr composite coating containing Ni nanocrystals and preparation method of Ni-Cr composite coating

Abstract

The invention discloses a Ni-Cr composite coating containing Ni nanocrystals and a preparation method of the Ni-Cr composite coating. The preparation method of the Ni-Cr composite coating containing the Ni nanocrystals comprises the following steps: (1) cleaning a to-be-plated workpiece with an organic solvent, soaking the to-be-plated workpiece in a sulfuric acid solution, and cleaning the to-be-plated workpiece until the to-be-plated workpiece is neutral after soaking treatment to obtain a pretreated to-be-plated workpiece; and (2) the pretreated workpiece to be plated is put into an electrolyte for electro-deposition, the workpiece is taken out after electro-deposition is completed, the workpiece is cleaned and then subjected to heat treatment, and the Ni-Cr composite coating containing the Ni nanocrystals is obtained after heat treatment is completed. The research shows that the Ni-Cr composite coating containing the Ni nanocrystals, which is prepared by the method disclosed by the invention, has relatively good corrosion resistance. In addition, the electro-deposition condition is mild, and the energy consumption in the electroplating process is reduced; and the formula of the electrolyte is reasonable, and the impurity ion detection limit can be controlled within 0.01 g / L or less. Therefore, the method is of great significance in promoting green development of the electroplating industry and achieving the purposes of energy conservation and emission reduction.

Description

Technical Field

[0001] The present invention relates to the technical field of electroplating, and in particular to a Ni-Cr composite coating containing Ni nanocrystals and a preparation method thereof. Background Art

[0002] Hydraulic components, as core components in modern mechanical systems, perform crucial functions in energy conversion, transmission, and control. They include power elements (such as hydraulic pumps), actuators (such as hydraulic cylinders or motors), control elements (such as valves), and auxiliary components (such as fuel tanks and filters). Hydraulic systems are widely used in industries such as heavy machinery, aerospace, and shipbuilding due to their high torque, fast response, and ease of achieving continuously variable speeds.

[0003] With the development of modern industry, especially in the field of hydraulic components, the requirements for material performance are becoming increasingly stringent. Traditional single metal coatings are no longer able to meet the demands of high-performance applications, especially in complex and harsh working environments such as corrosive media. Therefore, the development of corrosion-resistant composite coatings has become a research hotspot. Summary of the Invention

[0004] In order to overcome at least one of the technical problems existing in the prior art, the present invention first provides a Ni-Cr composite coating containing Ni nanocrystals and a preparation method thereof.

[0005] The technical solutions of the present invention are as follows:

[0006] The present invention first provides a method for preparing a Ni-Cr composite coating containing Ni nanocrystals, which comprises the following steps:

[0007] (1) After cleaning the workpiece to be plated with an organic solvent, immersing it in a sulfuric acid solution, and washing it to neutrality after immersion treatment to obtain a pre-treated workpiece to be plated;

[0008] (2) placing the pre-treated workpiece to be plated in an electrolyte for electrodeposition, taking out the workpiece after the electrodeposition is completed, cleaning it, and then performing a heat treatment, and obtaining the Ni-Cr composite coating containing Ni nanocrystals after the heat treatment;

[0009] The electrolyte described in step (2) is prepared with deionized water and contains the following components: NiSO4·6H2O 100-200 g / L, NiCl2·6H2O 30-50 g / L, Cr2(SO4) 340-60 g / L, additives 8-12 g / L; and buffer 15-25 g / L.

[0010] The inventors surprisingly found during their research that the Ni nanocrystalline Ni-Cr composite coating prepared by the method of the present invention has good corrosion resistance.

[0011] Preferably, the mass fraction of sulfuric acid in the sulfuric acid solution in step (2) is 10-20%.

[0012] Most preferably, the mass fraction of sulfuric acid in the sulfuric acid solution in step (2) is 15%.

[0013] Preferably, the electrolyte described in step (2) is prepared with deionized water and contains the following components: NiSO4·6H2O 150g / L, NiCl2·6H2O 40g / L, Cr2(SO4) 350g / L, additive 10g / L; buffer 20g / L.

[0014] Preferably, the additive is sodium citrate.

[0015] Preferably, the buffer is boric acid.

[0016] Preferably, the specific conditions of the electrodeposition in step (2) are: at a current density of 1 to 10 A / dm 2 , and electrodeposition is carried out at a temperature of 40 to 60°C for 30 to 50 minutes.

[0017] Most preferably, the specific conditions of the electrodeposition in step (2) are: at a current density of 5A / dm 2 , and electrodeposition was carried out at a temperature of 50°C for 40 min.

[0018] Preferably, the specific conditions of the electrodeposition in step (2) are: first, at a current density of 3A / dm 2 , the electrodeposition was carried out at a temperature of 45°C for 15 min; then the current density was 5 A / dm 2 , the electrodeposition was carried out at a temperature of 50°C for 20 min; finally, the current density was 8 A / dm 2 , and electrodeposition was carried out at a temperature of 55°C for 5 min.

[0019] In further research, the inventors found that the corrosion resistance of the Ni-Cr composite coating containing Ni nanocrystals prepared under the above-mentioned three-step electrodeposition conditions of the present invention is significantly higher than that of the Ni-Cr composite coating containing Ni nanocrystals prepared under the above-mentioned one-step conditions of the present invention.

[0020] Here, the inventors need to explain that the specific conditions of the electrodeposition of the present invention are very critical; only when the Ni-Cr composite coating containing Ni nanocrystals is prepared under the above-mentioned three-step electrodeposition conditions of the present invention, its corrosion resistance can be further significantly improved; however, the Ni-Cr composite coating containing Ni nanocrystals prepared under other electrodeposition conditions cannot be further significantly improved.

[0021] Preferably, the specific conditions of the heat treatment in step (2) are: heat treatment at 200-300° C. for 1-3 hours.

[0022] Most preferably, the specific conditions of the heat treatment in step (2) are: heat treatment at 250°C for 2h.

[0023] Preferably, the workpiece to be plated is made of stainless steel, copper, aluminum, cast steel or gray cast iron.

[0024] Preferably, the workpiece to be plated is a hydraulic component.

[0025] The present invention also provides a Ni-Cr composite coating containing Ni nanocrystals prepared by the above preparation method.

[0026] Beneficial Effects: This invention provides a method for preparing a Ni-Cr composite coating containing Ni nanocrystals. Studies have shown that the Ni-Cr composite coating prepared by this method exhibits excellent corrosion resistance. Furthermore, the mild electrodeposition conditions of this invention reduce energy consumption during the electroplating process. Furthermore, the rational formulation of the electrolyte allows the detection limit of impurity ions to be controlled within 0.01 g / L or less. This invention is therefore of great significance for promoting green development in the electroplating industry and achieving energy conservation and emission reduction goals. DETAILED DESCRIPTION

[0027] The present invention is further explained below with reference to specific examples, but the examples do not limit the present invention in any form.

[0028] Example 1 Preparation method of Ni-Cr composite coating containing Ni nanocrystals

[0029] (1) After cleaning the workpiece to be plated with acetone, immerse it in a sulfuric acid solution with a mass fraction of 15%, and rinse it until it is neutral after immersion treatment to obtain a pre-treated workpiece to be plated; the material of the workpiece to be plated is gray cast iron;

[0030] (2) placing the pre-treated workpiece to be plated in an electrolyte for electrodeposition, taking out the workpiece after the electrodeposition is completed, cleaning it, and then heat treating it at 250° C. for 2 hours, and obtaining the Ni-Cr composite coating containing Ni nanocrystals after the heat treatment;

[0031] The electrolyte described in step (2) is prepared with deionized water and contains the following components: NiSO4·6H2O 150g / L, NiCl2·6H2O 40g / L, Cr2(SO4) 350g / L, sodium citrate 10g / L; boric acid 20g / L;

[0032] The specific conditions of the electrodeposition described in step (2) are: at a current density of 5A / dm 2, and electrodeposition was carried out at a temperature of 50°C for 40 min.

[0033] Example 2 Preparation method of Ni-Cr composite coating containing Ni nanocrystals

[0034] (1) After cleaning the workpiece to be plated with acetone, immerse it in a sulfuric acid solution with a mass fraction of 15%, and rinse it until it is neutral after immersion treatment to obtain a pre-treated workpiece to be plated; the material of the workpiece to be plated is gray cast iron;

[0035] (2) placing the pre-treated workpiece to be plated in an electrolyte for electrodeposition, taking out the workpiece after the electrodeposition is completed, cleaning it, and then heat treating it at 250° C. for 2 hours, and obtaining the Ni-Cr composite coating containing Ni nanocrystals after the heat treatment;

[0036] The electrolyte described in step (2) is prepared with deionized water and contains the following components: NiSO4·6H2O 150g / L, NiCl2·6H2O 40g / L, Cr2(SO4) 350g / L, sodium citrate 10g / L; boric acid 20g / L;

[0037] The specific conditions of the electrodeposition in step (2) are: first, at a current density of 3A / dm 2 , the electrodeposition was carried out at a temperature of 45°C for 15 min; then the current density was 5 A / dm 2 , the electrodeposition was carried out at a temperature of 50°C for 20 min; finally, the current density was 8 A / dm 2 , and electrodeposition was carried out at a temperature of 55°C for 5 min.

[0038] Comparative Example 1 Preparation Method of Ni-Cr Composite Coating Containing Ni Nanocrystals

[0039] (1) After cleaning the workpiece to be plated with acetone, immerse it in a sulfuric acid solution with a mass fraction of 15%, and rinse it until it is neutral after immersion treatment to obtain a pre-treated workpiece to be plated; the material of the workpiece to be plated is gray cast iron;

[0040] (2) placing the pre-treated workpiece to be plated in an electrolyte for electrodeposition, taking out the workpiece after the electrodeposition is completed, cleaning it, and then heat treating it at 250° C. for 2 hours, and obtaining the Ni-Cr composite coating containing Ni nanocrystals after the heat treatment;

[0041] The electrolyte described in step (2) is prepared with deionized water and contains the following components: NiSO4·6H2O 150g / L, NiCl2·6H2O 40g / L, Cr2(SO4) 350g / L, sodium citrate 10g / L; boric acid 20g / L;

[0042] The specific conditions of the electrodeposition in step (2) are: first, at a current density of 3A / dm 2 , electroplating was carried out at a temperature of 45°C for 20 minutes; then electroplating was carried out at a current density of 5A / dm2 and a temperature of 50°C for 20 minutes.

[0043] Comparative Example 2 Preparation Method of Ni-Cr Composite Coating Containing Ni Nanocrystals

[0044] (1) After cleaning the workpiece to be plated with acetone, immerse it in a sulfuric acid solution with a mass fraction of 15%, and rinse it until it is neutral after immersion treatment to obtain a pre-treated workpiece to be plated; the material of the workpiece to be plated is gray cast iron;

[0045] (2) placing the pre-treated workpiece to be plated in an electrolyte for electrodeposition, taking out the workpiece after the electrodeposition is completed, cleaning it, and then heat treating it at 250° C. for 2 hours, and obtaining the Ni-Cr composite coating containing Ni nanocrystals after the heat treatment;

[0046] The electrolyte described in step (2) is prepared with deionized water and contains the following components: NiSO4·6H2O 150g / L, NiCl2·6H2O 40g / L, Cr2(SO4) 350g / L, sodium citrate 10g / L; boric acid 20g / L;

[0047] The specific conditions of the electrodeposition in step (2) are: first, at a current density of 2A / dm 2 , the electrodeposition was carried out at a temperature of 45°C for 20 min; then the current density was 6 A / dm 2 , the electrodeposition was carried out at a temperature of 50°C for 10 min; finally, the current density was 10 A / dm 2 , and electrodeposition was carried out at a temperature of 55°C for 10 min.

[0048] Comparative Example 3 Preparation Method of Ni-Cr Composite Coating Containing Ni Nanocrystals

[0049] (1) After cleaning the workpiece to be plated with acetone, immerse it in a sulfuric acid solution with a mass fraction of 15%, and rinse it until it is neutral after immersion treatment to obtain a pre-treated workpiece to be plated; the material of the workpiece to be plated is gray cast iron;

[0050] (2) placing the pre-treated workpiece to be plated in an electrolyte for electrodeposition, taking out the workpiece after the electrodeposition is completed, cleaning it, and then heat treating it at 250° C. for 2 hours, and obtaining the Ni-Cr composite coating containing Ni nanocrystals after the heat treatment;

[0051] The electrolyte described in step (2) is prepared with deionized water and contains the following components: NiSO4·6H2O 150g / L, NiCl2·6H2O 40g / L, Cr2(SO4) 350g / L, sodium citrate 10g / L; boric acid 20g / L;

[0052] The specific conditions of the electrodeposition in step (2) are: first, at a current density of 3A / dm 2 , the electrodeposition was carried out at a temperature of 40°C for 10 min; then the current density was 5 A / dm 2 , the electrodeposition was carried out at a temperature of 55°C for 20 min; finally, the current density was 8 A / dm 2 , and electrodeposition was carried out at 60°C for 10 min.

[0053] Experimental Example 1 Corrosion Resistance Test

[0054] The workpieces of Ni-Cr composite coating containing Ni nanocrystals prepared according to Examples 1-2 and Comparative Examples 1-3 were placed in a salt spray test chamber, and a 5% (mass fraction) sodium chloride aqueous solution with a pH of 6.5 was used as the spray medium at a rate of 1 ml / (cm 2 The spraying was carried out at a spray volume of 1.5 h) and the temperature of the spray box was (35±2)°C; the time when blistering of the composite coating appeared was recorded. The results are shown in Table 1.

[0055] Table 1. Corrosion resistance test results

[0056] Foaming time Ni-Cr composite coating containing Ni nanocrystals prepared by the method of Example 1 144h Ni-Cr composite coating containing Ni nanocrystals prepared by the method of Example 2 336h Ni-Cr composite coating containing Ni nanocrystals prepared by the method of Comparative Example 1 120h Ni-Cr composite coating containing Ni nanocrystals prepared by the method of Comparative Example 2 168h Ni-Cr composite coating containing Ni nanocrystals prepared by the method of Comparative Example 3 156h

[0057] It can be seen from the experimental results in Table 1 that in the salt spray test, the Ni-Cr composite coating containing Ni nanocrystals prepared by the method of Example 1 did not show blistering until 144 hours, which shows that the Ni-Cr composite coating containing Ni nanocrystals prepared by the method of the present invention has good corrosion resistance.

[0058] It can be seen from the experimental results in Table 1 that in the salt spray test, the Ni-Cr composite coating containing Ni nanocrystals prepared by the method of Example 2 has a significantly longer time for blistering to appear than the Ni-Cr composite coating containing Ni nanocrystals prepared by the method of Example 1; this indicates that the Ni-Cr composite coating containing Ni nanocrystals prepared under the three-step electrodeposition conditions of the present invention has significantly higher corrosion resistance than the Ni-Cr composite coating containing Ni nanocrystals prepared under the above-mentioned one-step conditions of the present invention.

[0059] It can be seen from the experimental results in Table 1 that in the salt spray test, the time for blistering of the Ni-Cr composite coating containing Ni nanocrystals prepared by the method of Comparative Example 1 was not extended compared with the Ni-Cr composite coating containing Ni nanocrystals prepared by the method of Example 1; the time for blistering of the Ni-Cr composite coating containing Ni nanocrystals prepared by the methods of Comparative Examples 2 and 3 was extended compared with the Ni-Cr composite coating containing Ni nanocrystals prepared by the method of Example 1, but the extension was not large, and was not as good as the Ni-Cr composite coating containing Ni nanocrystals prepared by the method of Example 2; this shows that the specific conditions of the electrodeposition of the present invention are very critical; only the Ni-Cr composite coating containing Ni nanocrystals prepared under the three-step electrodeposition conditions of the present invention can further significantly improve its corrosion resistance; however, the Ni-Cr composite coating containing Ni nanocrystals prepared under other electrodeposition conditions cannot further significantly improve its corrosion resistance.

Claims

1. A method for preparing a Ni-Cr composite coating containing Ni nanocrystals, characterized in that: The following steps are included: (1) After cleaning the workpiece to be plated with an organic solvent, immersing it in a sulfuric acid solution, and washing it until it is neutral after immersion treatment to obtain a pre-treated workpiece to be plated; (2) placing the pre-treated workpiece to be plated in an electrolyte for electrodeposition, taking out the workpiece after the electrodeposition is completed, cleaning it, and then performing heat treatment, and obtaining the Ni-Cr composite coating containing Ni nanocrystals after the heat treatment is completed; The electrolyte described in step (2) is prepared with deionized water and contains the following components: NiSO4·6H2O 100-200 g / L, NiCl2·6H2O 30-50 g / L, Cr2(SO4)3 40-60 g / L, additives 8-12 g / L; and buffer 15-25 g / L.

2. The method for preparing a Ni-Cr composite coating containing Ni nanocrystals according to claim 1, wherein: The mass fraction of sulfuric acid in the sulfuric acid solution described in step (2) is 10-20%.

3. The method for preparing a Ni-Cr composite coating containing Ni nanocrystals according to claim 1, wherein: The electrolyte described in step (2) is prepared with deionized water and contains the following components: NiSO4·6H2O 150g / L, NiCl2·6H2O 40g / L, Cr2(SO4)3 50g / L, additive 10g / L; buffer 20g / L.

4. The method for preparing a Ni-Cr composite coating containing Ni nanocrystals according to claim 3, wherein: The additive is sodium citrate.

5. The method for preparing a Ni-Cr composite coating containing Ni nanocrystals according to claim 3, wherein: The buffer is boric acid.

6. The method for preparing a Ni-Cr composite coating containing Ni nanocrystals according to claim 1, wherein: The specific conditions of the electrodeposition described in step (2) are: at a current density of 1 to 10 A / dm 2 , and electrodeposition is carried out at a temperature of 40 to 60°C for 30 to 50 minutes.

7. The method for preparing a Ni-Cr composite coating containing Ni nanocrystals according to claim 1, wherein: The specific conditions of the heat treatment described in step (2) are: heat treatment at 200-300° C. for 1-3 hours.

8. The method for preparing a Ni-Cr composite coating containing Ni nanocrystals according to claim 1, wherein: The material of the workpiece to be plated is stainless steel, copper, aluminum, cast steel or gray cast iron.

9. The method for preparing a Ni-Cr composite coating containing Ni nanocrystals according to claim 1, wherein: The workpiece to be plated is a hydraulic part.

10. A Ni-Cr composite coating containing Ni nanocrystals prepared by the preparation method according to any one of claims 1 to 9.