CN115613087A - A kind of high hardness nano-Ni-Co-B alloy substitutes chromium electroplating solution and its application - Google Patents

Abstract

A high-hardness nano-Ni-Co-B alloy chromium-substituting electroplating solution and an application thereof belong to the field of electroplating, and in particular relate to a high-hardness nano-Ni-Co-B alloy chromium-substituting electroplating solution and an application thereof. The purpose of the present invention is to solve the problem that the existing trivalent chromium electroplating cannot meet the needs of replacing hard chromium, the composite plating process is complex, and the uneven current distribution leads to uneven thickness of the coating, and its large-scale application is still subject to relatively large restrictions and the existence of nickel-based alloys. The problem of large internal stress, low hardness and slow plating speed. A high-hardness nano Ni-Co-B alloy chromium-substituting electroplating solution is prepared from a main salt, a boron source, an anode activator, a pH buffer, a grain refiner, a stress reliever, a wetting agent and distilled water. The Ni-Co-B alloy substituting chromium coating prepared by using a high-hardness nano-Ni-Co-B alloy substituting chromium electroplating solution has a hardness of 1100-1300HV-50.

Description

A kind of high-hardness nano-Ni-Co-B alloy substitutes chromium electroplating solution and its application

technical field

The invention belongs to the field of electroplating, and in particular relates to a high-hardness nano-Ni-Co-B alloy chromium-substituting electroplating solution and an application thereof.

Background technique

As one of the indispensable processes in the electroplating industry, hexavalent chromium electroplating technology is widely used. When used as a protective-decorative coating, it has the advantages of bright and beautiful color and strong anti-discoloration ability; in addition, due to the advantages of high hardness, good wear resistance and high corrosion resistance, the chrome plating layer is widely used in cylinders and pistons of engines Ring, the roll surface of the embossing roller, the inner cavity of the gun, etc. However, the hexavalent chromium plating technology also has some disadvantages that limit its application. For example, severe hydrogen evolution at the cathode, low current efficiency, high current and high voltage deposition are required, hexavalent chromium is highly toxic, and wastewater treatment is difficult. It is very necessary to find a green and environmentally friendly generation of chromium plating coatings and process methods that meet or even exceed the performance of chromium (Ⅵ) coatings.

Due to the large reduction in grain size and the existence of a large number of grain boundaries between adjacent grains, nano-coatings have unique physical and chemical properties, such as high corrosion resistance, high hardness, and high wear resistance. In the electroplating process, it is usually necessary to add suitable additives to increase the cathode polarization, so that the nucleation speed of crystal nuclei increases and the grains are finer, so as to obtain nano-coatings. Therefore, the primary problem of preparing nano-coatings is to develop suitable non-toxic additives, which can significantly increase the cathodic polarization under the blocking effect or penetration effect of the additives. Adding a small amount of additives in the plating solution can greatly improve performance of the coating. According to the different types of additives, it plays the role of grain refinement, leveling, wetting, and stress relief.

The current chromium generation technology mainly includes trivalent chromium electroplating process, composite electroplating process and alloy electroplating/electroless plating process, etc. Among them, trivalent chromium plating has been more and more used in the field of decorative chromium for its low toxicity, high dispersion and coverage. However, this technology cannot meet the needs of the generation of hard chrome. Using composite electroplating technology, adding insoluble hard phase particles to the plating solution can significantly increase the hardness of the coating, for example, the hardness of Ni-diamond and Ni-Co-diamond composite coatings can reach 700HV. However, the composite plating process is complicated, and the uneven current distribution leads to uneven thickness of the coating, so its large-scale application is still limited. Nickel-based alloys have the advantages of bright appearance, high hardness, high wear resistance, and high corrosion resistance, and have become the most promising coatings to replace hard chrome. Molybdenum alloys also have problems such as large internal stress, low hardness, and slow plating speed.

Contents of the invention

The purpose of the present invention is to solve the problem that the existing trivalent chromium electroplating cannot meet the needs of replacing hard chromium, the composite plating process is complex, and the uneven current distribution leads to uneven thickness of the coating, its large-scale application is still relatively limited and the existence of nickel-based alloys To solve the problems of large internal stress, low hardness and slow plating speed, a high-hardness nano-Ni-Co-B alloy chromium-substituting electroplating solution and its application are provided.

A high-hardness nano-Ni-Co-B alloy chromium-substituting electroplating solution is prepared from main salt, boron source, anode activator, pH buffer, grain refiner, stress reliever, wetting agent and distilled water;

Described main salt is nickel salt and cobalt salt;

The grain refiner is 2-ethylamino-4-methylthiazole-5-carboxylic acid, polyethyleneimine, myrcene, allyl furoate, 3-(methylthio)hexanol acetic acid One or a mixture of several esters;

The stress reliever is 1,3-dicyclohexyl imidazole chloride, 2-methoxy-4-vinylphenol or rose bengal;

Described wetting agent is polyethylene glycol, OP emulsifier or sodium lauryl sulfate.

A high-hardness nanometer Ni-Co-B alloy substituting chromium electroplating solution is used for preparing Ni-Co-B alloy substituting chromium coating.

Principle of the present invention:

The grain refiner of the present invention forms an extremely thin adsorption layer on the surface of the cathode through adsorption, which hinders the discharge of metal ions, thereby improving the polarization of the cathode; the grain refiner adsorbed on the surface of the cathode will Hinder or even completely inhibit the growth of crystals, so new crystals will be produced in other positions; so repeated, you can get fine and bright high-quality coatings;

The stress reliever of the present invention can cause the coating to produce a certain compressive stress, thereby offsetting the tensile stress in the coating, improving the ductility of the coating, preventing the generation of micro-cracks on the surface of the coating, and improving the brightness of the coating;

The addition of the wetting agent of the present invention can reduce the surface tension of the electrode/solution interface, improve the wettability of the electrolyte to the electrode surface, and make metal ions easier to deposit on the cathode; at the same time, when the size of the hydrogen bubbles is small It is separated from the surface of the electrode, preventing it from staying on the surface of the cathode and causing shielding, eliminating pinholes, and improving the hardness and brightness of the coating.

The addition of the grain refiner, the stress reliever and the wetting agent can make the coating of the present invention meet the appearance and hardness requirements of the hexavalent chromium coating, and avoid the use of toxic hexavalent chromium.

Advantages of the present invention:

One, the average grain size of the Ni-Co-B alloy substituting chromium coating prepared by the high-hardness nano Ni-Co-B alloy substituting chromium plating solution prepared by the present invention is about 10nm, which is a nanocrystalline coating, and the coating stress is lower, There is no micro-crack in electroplating for a long time;

2. The hardness of the coating of the present invention after heat treatment can reach 1100-1300HV-50, and the corrosion resistance is good, the bonding strength between the coating and the substrate is high, and the coating has no cracks;

3. The cathodic current efficiency of the high-hardness nano-Ni-Co-B alloy chromium-substituting electroplating solution prepared by the present invention reaches 95%, and the deposition rate is 70-80 μm/h.

Description of drawings

Fig. 1 is X-ray diffraction (XRD) figure, among the figure 1 is the X-ray diffraction curve of the plated piece prepared in step 3 of embodiment 1 before heat treatment, and 2 is the Ni-Co obtained after 200 ℃ of heat treatment in step 4 of embodiment 1 -The X-ray diffraction curve of the B alloy chromium coating, 3 is the X-ray diffraction curve of the Ni-Co-B alloy chromium coating obtained after the 300°C heat treatment in Step 4 of Example 2;

Fig. 2 is the SEM figure of the Ni-Co-B alloy substituting chromium coating obtained after 200 DEG C of heat treatment in step 4 of embodiment 1;

Fig. 3 is the optical micrograph of the Ni-Co-B alloy chromium-substituting coating obtained after 200 DEG C of heat treatment in step 4 of embodiment 1;

Fig. 4 is an optical microscope image of the chromium-substituting Ni-Co-B alloy coating obtained after heat treatment at 200°C in Step 4 of Example 1 after being corroded by a 3.5% sodium chloride solution.

detailed description

The following examples further illustrate the content of the present invention, but should not be construed as limiting the present invention. Without departing from the essence of the present invention, the modifications and substitutions made to the methods, steps or conditions of the present invention all belong to the scope of the present invention.

Specific embodiment one: In this embodiment, a high-hardness nano-Ni-Co-B alloy chromium-substituting electroplating solution consists of main salt, boron source, anode activator, pH buffer, grain refiner, stress reliever, wetting Prepared with reagent and distilled water;

Described main salt is nickel salt and cobalt salt;

The grain refiner is 2-ethylamino-4-methylthiazole-5-carboxylic acid, polyethyleneimine, myrcene, allyl furoate, 3-(methylthio)hexanol acetic acid One or a mixture of several esters;

The stress reliever is 1,3-dicyclohexyl imidazole chloride, 2-methoxy-4-vinylphenol or rose bengal;

Described wetting agent is polyethylene glycol, OP emulsifier or sodium lauryl sulfate.

Embodiment 2: This embodiment differs from Embodiment 1 in that: the nickel salt is nickel sulfate; the cobalt salt is cobalt sulfate. Other steps are the same as in the first embodiment.

Specific embodiment three: the differences between this embodiment and specific embodiment one or two are: the boron source is dimethylaminoborane; the anode activator is nickel chloride; the pH The buffer is boric acid. Other steps are the same as those in Embodiment 1 or 2.

Embodiment 4: The difference between this embodiment and Embodiments 1 to 3 is that the concentration of nickel salt in the high-hardness nano-Ni-Co-B alloy chromium-substituting electroplating solution is 100-150 g/L, The concentration of cobalt salt is 10-15g/L, the concentration of boron source is 1-5g/L, the concentration of anode activator is 20-50g/L, the concentration of pH buffer is 30-50g/L, and the grain is refined The concentration of the agent is 0.1-5g/L, the concentration of the stress relief agent is 0.5-1.5g/L, and the concentration of the wetting agent is 0.05-1g/L. Other steps are the same as those in Embodiments 1 to 3.

Embodiment 5: This embodiment differs from Embodiments 1 to 4 in that: a high-hardness nano-Ni-Co-B alloy chromium-substituting electroplating solution is used to prepare Ni-Co-B alloy chromium-substituting plating. Other steps are the same as those in Embodiments 1 to 4.

Specific embodiment six: the difference between this embodiment and one of the specific embodiments one to five is: a high-hardness nano-Ni-Co-B alloy chromium-substituting electroplating solution is used to prepare a Ni-Co-B alloy chromium-substituting coating as follows Steps completed:

1. Preparation of chromium-substituting electroplating solution:

Dissolving the main salt, boron source, anode activator, pH buffer, grain refiner, stress reliever and wetting agent into distilled water to obtain a chromium-substituting electroplating solution;

2. Pretreating the substrate to obtain a pretreated substrate;

In step 2, immerse the substrate in a degreasing solution at 80-90°C, take it out and rinse it with distilled water; pickle it with hydrochloric acid and rinse it with distilled water to obtain the pretreated substrate;

3. Adjust the pH value of the chromium-substituting electroplating solution to 3.5-4.0, immerse the pretreated substrate into the chromium-substituting electroplating solution, and then under the conditions of a temperature of 40°C-50°C and a current density of ^2-7A /dm2 Electroplating is carried out to obtain the plated parts;

4. High temperature heat treatment:

Put the plated parts in a tube furnace, under the protection of argon atmosphere, raise the temperature of the plated parts to 200-300°C, keep the temperature at 200-300°C, and finally cool down to room temperature naturally to obtain Ni- on the surface of the substrate. Co-B alloy instead of chromium plating. Other steps are the same as those in Embodiments 1 to 5.

Specific embodiment seven: the difference between this embodiment and one of specific embodiments one to six is that the degreasing liquid described in step 2 is formed by mixing sodium hydroxide, sodium carbonate, sodium phosphate, sodium silicate and distilled water, wherein The concentration of sodium hydroxide is 60～80g/L, and the concentration of sodium carbonate is 20～60g/L, and the concentration of sodium phosphate is 15～30g/L, and the concentration of sodium silicate is 5～10g/L; The mass fraction of the hydrochloric acid is 10%-20%; the matrix in the second step is cold-rolled steel. Other steps are the same as those in Embodiments 1 to 6.

Embodiment 8: The difference between this embodiment and Embodiments 1 to 7 is: in step 2, immerse the substrate in the degreasing solution for 5 minutes to 10 minutes, rinse it with distilled water for 3 to 5 times after taking it out, and then use hydrochloric acid Pickling for 3 to 5 times and rinsing with distilled water for 3 to 5 times to obtain the pretreated substrate. Other steps are the same as those in Embodiments 1 to 7.

Embodiment 9: The difference between this embodiment and Embodiment 1 to Embodiment 8 is that the electroplating time in Step 3 is 30-180 minutes. Other steps are the same as those in Embodiments 1 to 8.

Embodiment 10: The difference between this embodiment and Embodiment 1 to Embodiment 9 is: the time of heat preservation described in step 4 is 1h～2h; °C/min. Other steps are the same as those in Embodiments 1 to 9.

Adopt the following examples to verify the beneficial effects of the present invention:

Embodiment 1: a kind of high hardness nano-Ni-Co-B alloy substitution chromium electroplating solution is used for preparing Ni-Co-B alloy substitution chromium coating and is finished according to the following steps:

1. Preparation of chromium-substituting electroplating solution:

NiSO ₄ ·6H ₂ O, CoSO ₄ ·7H ₂ O, NiCl ₂ ·6H ₂ O, boric acid, dimethylaminoborane, 2-ethylamino-4-methylthiazole-5-carboxylic acid, 2- Methoxy-4-vinylphenol and sodium lauryl sulfate are dissolved in distilled water to obtain a chromium-substituted electroplating solution;

The concentration of NiSO ₄ 6H ₂ O in the chromium-substituting electroplating solution described in step 1 is 120g/L, the concentration of CoSO ₄ 7H ₂ O is 12g/L, and the concentration of NiCl ₂ 6H ₂ O is 40g/L, The concentration of boric acid is 35g/L, the concentration of dimethylaminoborane is 3g/L, the concentration of 2-ethylamino-4-methylthiazole-5-carboxylic acid is 3g/L, 2-methoxy- The concentration of 4-vinylphenol is 1g/L, and the concentration of sodium lauryl sulfate is 0.1g/L;

2. Pretreating the substrate to obtain a pretreated substrate;

In step 2, immerse the substrate in a degreasing solution at 90°C for 5 minutes, take it out, rinse it with distilled water for 5 times, then pickle it with 15% hydrochloric acid for 3 times, and rinse it with distilled water for 5 times to obtain the pretreated substrate;

The degreasing liquid described in step 2 is mixed by sodium hydroxide, sodium carbonate, sodium phosphate, sodium silicate and distilled water, and wherein the concentration of sodium hydroxide is 60g/L, and the concentration of sodium carbonate is 30g/L, phosphoric acid The concentration of sodium is 20g/L, and the concentration of sodium silicate is 8g/L;

The substrate described in step 2 is cold-rolled steel;

3. Adjust the pH value of the chromium-substituting electroplating solution to 3.5-4.0, immerse the pretreated substrate in the chromium-substituting electroplating solution, and then electroplate for 30 minutes at a temperature of 50°C and a current density of 7A/dm ² to obtain plating;

4. High temperature heat treatment:

The plated parts were placed in a tube furnace, and under the protection of argon atmosphere, the plated parts were heated up to 200 °C at a heating rate of 10 °C/min, then kept at 200 °C for 1 h, and finally cooled to room temperature naturally to obtain the base The surface of the material is Ni-Co-B alloy instead of chromium plating.

The comparison of the XRD patterns of the plated parts obtained in this embodiment before and after heat treatment is shown in Figure 1; it shows that the crystal grains grow preferentially along the (111) crystal plane. After comparison, it can be found that after heat treatment, the width of the half-maximum width of the diffraction peak corresponding to Ni(111) of the coating becomes smaller, and the peak intensity gradually increases. inter-compound, so that the hardness increases rapidly.

Fig. 1 is X-ray diffraction (XRD) figure, among the figure 1 is the X-ray diffraction curve of the plated piece prepared in step 3 of embodiment 1 before heat treatment, and 2 is the Ni-Co obtained after 200 ℃ of heat treatment in step 4 of embodiment 1 -The X-ray diffraction curve of the B alloy chromium coating, 3 is the X-ray diffraction curve of the Ni-Co-B alloy chromium coating obtained after the 300°C heat treatment in Step 4 of Example 2;

Further, when the grain size is between 1 and 100nm, the average grain size can be calculated using the Scherrer formula, the specific formula is as follows:

In the formula, d——average grain size (nm);

λ—X-ray wavelength (λ=0.154nm);

K - Scherrer constant (K=0.89);

B——Diffraction peak width at half maximum;

θ—Bragg diffraction angle;

After calculation, the average grain size is 10.26nm, which proves that the coating is a nano-coating. The hardness value is 1210HV-50.

Fig. 2 is the SEM figure of the Ni-Co-B alloy substituting chromium coating obtained after 200 DEG C of heat treatment in step 4 of embodiment 1;

Fig. 3 is the optical micrograph of the Ni-Co-B alloy chromium-substituting coating obtained after 200 DEG C of heat treatment in step 4 of embodiment 1;

Figures 2 and 3 show that the surface is dense and smooth, and the hard phase is evenly distributed.

Example 2: The difference between this example and Example 1 is that in step 4, the plated piece is placed in a tube furnace, and under the protection of an argon atmosphere, the plated piece is heated up to 300 °C at a heating rate of 10 °C/min. ℃, and then kept at 300 ℃ for 1h, and finally cooled to room temperature naturally to obtain a Ni-Co-B alloy instead of chromium coating on the surface of the substrate. Other steps and parameters are all the same as in Example 1.

The XRD of embodiment 2 gained coating is shown in Figure 1;

It can be found from Figure 2 that the coating also appears in a crystalline state at this time, which improves the hardness of the coating.

Further, the average grain size was calculated by the Scherrer formula. In Example 2, the average grain size was 9.38nm, which proved that the coating was a nano-coating. The hardness value is 1290HV-50.

Comparative example: the difference between the present example and Example 1 is: in step one: prepare chromium-substituting electroplating solution:

Dissolve NiSO ₄ 6H ₂ O, CoSO ₄ 7H ₂ O, NiCl ₂ 6H ₂ O, boric acid and dimethylaminoborane into distilled water to obtain a chromium substitute electroplating solution; the chromium substitute described in step one The concentration of NiSO ₄ 6H ₂ O in the electroplating solution is 120g/L, the concentration of CoSO ₄ 7H ₂ O is 12g/L, the concentration of NiCl ₂ 6H ₂ O is 40g/L, and the concentration of boric acid is 35g/L. The concentration of dimethylaminoborane was 3 g/L. Other steps and parameters are all the same as in Example 1.

The grain size of the coating prepared in the comparative example is 100.4nm, and the hardness value is 698HV-50. It is further illustrated that the grain refiner, stress reliever, and wetting agent of the present invention play a significant role in reducing the crystal size and improving the hardness of the coating.

Claims (10)

1. A high-hardness nano Ni-Co-B alloy chromium-substituting electroplating solution is characterized in that the high-hardness nano Ni-Co-B alloy chromium-substituting electroplating solution is prepared from main salt, a boron source, an anode activator, a pH buffering agent, a grain refiner, a stress relieving agent, a wetting agent and distilled water;

the main salt is nickel salt and cobalt salt;

the grain refiner is one or a mixture of more of 2-ethylamino-4-methylthiazole-5-carboxylic acid, polyethyleneimine, myrcene, allyl furoate and 3- (methylthio) hexanol acetate;

the stress relieving agent is 1,3-dicyclohexyl imidazole chloride, 2-methoxy-4-vinylphenol or rose bengal;

the wetting agent is polyethylene glycol, OP emulsifier or lauryl sodium sulfate.

2. The plating solution of high hardness nano Ni-Co-B alloy as recited in claim 1, wherein the nickel salt is nickel sulfate; the cobalt salt is cobalt sulfate.

3. The plating solution of high hardness nano Ni-Co-B alloy as recited in claim 1, wherein the boron source is dimethyl amino borane; the anode activator is nickel chloride; the pH buffering agent is boric acid.

4. The electroplating solution as claimed in any one of claims 1 to 3, wherein the concentration of the nickel salt, the cobalt salt, the boron source, the anode activator, the pH buffer and the grain refiner is 100 to 150g/L, 10 to 15g/L, 1 to 5g/L, 20 to 50g/L, 30 to 50g/L, 0.1 to 5g/L, 0.5 to 1.5g/L, and 0.05 to 1g/L, respectively.

5. The use of the high hardness nano Ni-Co-B alloy chromium-substituting electroplating solution according to claim 1, wherein a high hardness nano Ni-Co-B alloy chromium-substituting electroplating solution is used for preparing the Ni-Co-B alloy chromium-substituting plating layer.

6. The use of the high-hardness nano Ni-Co-B alloy chromium-substituting electroplating solution as claimed in claim 5, wherein the preparation of the Ni-Co-B alloy chromium-substituting electroplating solution by using the high-hardness nano Ni-Co-B alloy chromium-substituting electroplating solution is carried out by the following steps:

1. preparing a chromium-substituted electroplating solution:

dissolving main salt, a boron source, an anode activator, a pH buffering agent, a grain refiner, a stress relieving agent and a wetting agent into distilled water to obtain a chromium-substituted electroplating solution;

2. pretreating the substrate to obtain a pretreated substrate;

soaking the matrix into deoiling liquid at 80-90 ℃, taking out and washing with distilled water; then using hydrochloric acid for pickling and washing by distilled water to obtain a pretreated matrix;

3. regulating the pH value of the chromium-substituting electroplating solution to 3.5-4.0, immersing the pretreated substrate into the chromium-substituting electroplating solution, and then controlling the temperature to be 40-50 ℃ and the current density to be 2-7A/dm ² Electroplating under the condition of (1) to obtain a plated part;

4. high-temperature heat treatment:

and (3) placing the plated part in a tube furnace, heating the plated part to 200-300 ℃ under the protection of argon atmosphere, preserving heat at 200-300 ℃, and naturally cooling to room temperature to obtain the Ni-Co-B alloy chromium-substituted plating layer on the surface of the base material.

7. The use of the high-hardness nano Ni-Co-B alloy chromium-substituting electroplating solution according to claim 5, wherein the degreasing liquid in the step two is formed by mixing sodium hydroxide, sodium carbonate, sodium phosphate, sodium silicate and distilled water, wherein the concentration of the sodium hydroxide is 60-80 g/L, the concentration of the sodium carbonate is 20-60 g/L, the concentration of the sodium phosphate is 15-30 g/L, and the concentration of the sodium silicate is 5-10 g/L; the mass fraction of the hydrochloric acid in the second step is 10-20%; and the substrate in the second step is cold-rolled steel.

8. The application of the high-hardness nano Ni-Co-B alloy chromium-substituting electroplating solution according to claim 5 is characterized in that in the second step, the substrate is immersed in deoiling liquid for 5min to 10min, the substrate is taken out and washed by distilled water for 3 times to 5 times, then washed by hydrochloric acid for 3 times to 5 times, and washed by distilled water for 3 times to 5 times, so that the pretreated substrate is obtained.

9. The use of the electroplating solution of high hardness nano Ni-Co-B alloy as claimed in claim 5, wherein the electroplating time in step three is 30-180 min.

10. The application of the high-hardness nano Ni-Co-B alloy chromium-substituting electroplating solution as claimed in claim 5, wherein the heat preservation time in the fourth step is 1-2 h; the heating rate in the fourth step is 5-10 ℃/min.

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