Process for compositely plating coating on surface of diamond

Abstract

The invention discloses a process for compositely plating a plating layer on the surface of diamond, and relates to the technical field of diamond composite plating. According to the method, firstly, the diamond micro powder is pretreated through chemical plating, then plating is conducted through electroplating, and finally the obtained plating is subjected to characterization testing. According to the diamond surface composite plating process, through combination of chemical plating and nickel electroplating, the electrical conductivity of the diamond micro-powder and the binding force of the diamond micro-powder and the metal matrix are improved, the uniformity and stability of the plating are ensured, the mechanical performance and the surface quality of the plating are enhanced, and meanwhile, the diamond surface composite plating process is suitable for various metal matrixes and diamonds with different particle sizes; the working efficiency is improved; and the production cost is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of diamond composite plating, and in particular to a diamond surface composite plating process. Background Art

[0002] In addition to the introduction of impurities, diamond powder will also produce cracks, pores and other defects during the production process, which will directly affect the quality of diamond. At the same time, diamond has ultra-high chemical stability, and the interface energy between it and metal binders and resin binders is very high, which leads to weak interface bonding between diamond and binders in diamond tools, and poor bonding force. Therefore, a metal layer is first plated on the surface of the diamond to improve its quality.

[0003] Since diamond itself is not conductive, before electroplating, it is necessary to chemically plate nickel (diamond surface metallization), coat a layer of conductive film (nickel) on the surface of diamond micropowder, and then electroplate nickel by roller plating.

[0004] In summary, the present invention designs a diamond surface composite plating process. Summary of the invention

[0005] In view of the deficiencies in the prior art, the purpose of the present invention is to provide a diamond surface composite plating process, which adopts a composite plating method of chemical plating and electroplating, and improves the plating effect of electroplating nickel on artificial diamond micropowder and improves the quality of artificial diamond micropowder by optimizing process parameters.

[0006] In order to achieve the above object, the present invention is implemented by the following technical scheme: a diamond surface composite plating process, comprising the following steps:

[0007] 1. First, pre-treat the diamond powder and prepare the chemical plating solution, add 40-80g / L citric acid, 40-80g / L sodium hypophosphite, 0.001-1g / L thiourea, 2-10ml / L lactic acid, and finally adjust the pH value of the chemical plating solution to 6-9 with an appropriate amount of ammonia water; after preparing the chemical plating solution, add the diamond powder for mechanical stirring, the stirring speed is 150-180r / min, the water bath is heated at 35-70℃ for 2-4h, and the liquid is replenished during the stirring process to maintain the concentration of the chemical plating solution, and the coating weight increases by 5-35%;

[0008] 2. Prepare a nickel electroplating solution for the diamond powder after chemical plating in step 1, add 150-300g / L nickel sulfate, 5-15g / L nickel chloride, and 30-45g / L boric acid, and adjust the pH value of the electroplating solution to 3-5, the plating bottle speed is 1-60r / min, and the pH value of the electroplating solution is monitored every 30min;

[0009] 3. Post-process the diamond powder after electroplating, wash with water to remove the electroplating solution and other impurities on the surface of the diamond powder composite coating, and sieve and sort;

[0010] 4. Conduct characterization tests on the composite coating, including coating weight gain rate, coating density and coating corrosion resistance.

[0011] Coating weight gain rate: The coating weight gain rate is expressed by the ratio of the difference in mass of diamond powder before electroplating to the mass before electroplating per unit time, and m3 is the mass of diamond powder after electroplating.

[0012]

[0013] Coating density: Coating density is expressed by the coating mass per unit volume. Diamond micropowder particles are often irregular in shape under microscope observation. For the convenience of calculation, the shape of diamond particles is approximated as sphere in this invention. The equivalent volume particle size of diamond micropowder before and after coating is measured by laser particle size analyzer as the average particle size r0 and r1, and the diamond density is ρ0 (3.5 g / cm 3 ), n in (2) represents the number of particles in 3g of diamond powder, and the coating density ρ1 is calculated using formula (3):

[0014]

[0015] Coating morphology: The coating morphology on the surface of diamond powder was observed using a scanning electron microscope.

[0016] Before the chemical plating in step 1, the nickel block and the cathode wire are immersed in dilute nitric acid to remove the oxide film, and then the treated nickel block is used as the anode and the cathode wire is used as the cathode.

[0017] The diamond micropowder has a D50 value of 1.0-500.

[0018] The electroplating in step 2 is performed by roller plating, the electroplating current is 0.5-20A, and the electroplating load is 500-5000g.

[0019] The beneficial effects of the present invention are as follows: the present invention adopts a composite plating method of chemical plating and electroplating, and the wire collection adopts chemical plating to increase the quality of the diamond micropowder coating, which can improve the coating quality. The diamond micropowder after chemical plating is then electroplated, and the coating weight gain is better. Increasing the quality of the diamond micropowder by chemical plating can make the combined force on the diamond micropowder during the electroplating process downward, reduce the occurrence of floating phenomenon, greatly enhance the plating effect of diamond micropowder electroplating nickel, and improve the quality of diamond micropowder. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments;

[0021] Figure 1 This is a schematic diagram of Example 1 of the present invention. DETAILED DESCRIPTION

[0022] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further explained below in conjunction with specific implementation methods.

[0023] Reference Figure 1 , this specific implementation adopts the following technical solution: a diamond surface composite plating process, comprising the following steps:

[0024] 1. Firstly, pre-treat the diamond powder and prepare the chemical plating solution, add 40-80g / L citric acid, 40-80g / L sodium hypophosphite, 0.001-1g / L thiourea, 2-10ml / L lactic acid, and finally adjust the pH value of the chemical plating solution to 6-9 with an appropriate amount of ammonia water; after preparing the chemical plating solution, add the diamond powder for mechanical stirring, the stirring speed is 150-180r / min, the water bath is heated at 35-70℃ for 2-4h, and the liquid is added during the stirring process to maintain the concentration of the chemical plating solution, and the coating weight increases by 5-35%; the chemical plating process is the same as the single chemical plating patent except for the different amount of supplementation, and the other processes are the same, and the formula needs to be supplemented at the same time as the cylinder formula.

[0025] 2. Prepare nickel electroplating solution for the diamond powder after chemical plating in step 1, add 150-300g / L nickel sulfate, 5-15g / L nickel chloride, 30-45g / L boric acid, and adjust the pH value of the plating solution to 3-5, the plating bottle speed is 1-60r / min, and the pH value of the plating solution is monitored every 30min.

[0026] 3. Post-process the diamond powder after electroplating, wash with water to remove the electroplating solution and other impurities on the surface of the diamond powder composite coating, and sieve and sort;

[0027] 4. Conduct characterization tests on the composite coating, including coating weight gain rate, coating density and coating corrosion resistance.

[0028] Coating weight gain rate: The coating weight gain rate is expressed by the ratio of the difference in mass of diamond powder before electroplating to the mass before electroplating per unit time, and m3 is the mass of diamond powder after electroplating.

[0029]

[0030] Coating density: Coating density is expressed by the coating mass per unit volume. Diamond micropowder particles are often irregular in shape under microscope observation. For the convenience of calculation, the shape of diamond particles is approximated as sphere in this invention. The equivalent volume particle size of diamond micropowder before and after coating is measured by laser particle size analyzer as the average particle size r0 and r1, and the diamond density is ρ0 (3.5 g / cm3 ), n in (2) represents the number of particles in 3g of diamond powder, and the coating density ρ1 is calculated using formula (3):

[0031]

[0032] Coating morphology: The coating morphology on the surface of diamond powder was observed using a scanning electron microscope.

[0033] Before the chemical plating in step 1, the nickel block and the cathode wire are immersed in dilute nitric acid to remove the oxide film, and then the treated nickel block is used as the anode and the cathode wire is used as the cathode.

[0034] The electroplating in step 2 is performed by roller plating, the electroplating current is 0.5-20A, and the electroplating load is 500-5000g.

[0035] This specific embodiment forms a conductive film on the surface of diamond micropowder through chemical plating and electroplating nickel process, thereby improving its conductivity. The process of chemical nickel plating and electroplating nickel can increase the bonding force between diamond micropowder and metal matrix, making the composite coating more solid. By accurately controlling the composition, pH value, temperature and stirring speed of chemical plating solution and electroplating solution, the uniformity and stability of the coating can be ensured. This process is suitable for various metal matrices and diamonds of different particle sizes. By improving the hardness, wear resistance and corrosion resistance of diamond tools, their service life can be extended, work efficiency can be improved and production costs can be reduced.

[0036] This specific implementation method optimizes the electroplating process parameters to improve the plating quality of diamond micropowder by optimizing the electroplating process parameters, and improves the electroplating coating quality by optimizing the electroplating process conditions and optimizing the composition and quality of the chemical coating in the chemical-electro composite plating. The diamond surface composite plating process has broad application prospects in industrial production and scientific research.

[0037] Example 1: When the electroplating weight gain rate is optimal, the electroplating process conditions are: electroplating current 2.5A, loading amount 18g, and electroplating time 8h; when the electroplating coating density is optimal, the electroplating process conditions are: electroplating current 2.5A, loading amount 12g, and electroplating time 6h.

[0038] like Figure 1 The SEM morphology of diamond powder electroplating under the best process conditions of weight gain rate and coating density is shown in the figure. It can be seen from the figure that the diamond surface is smooth and flat, which means that the diamond particles are tightly wrapped by nickel, there is no leakage plating, and the coating is dense. The SEM image shows that there is almost no free nickel metal and other impurities, which means that the plating solution is relatively stable, not decomposed, the reaction rate is appropriate, and the metal nickel produced by the reaction is all deposited on the diamond surface.

[0039] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A diamond surface composite plating process, characterized in that: The following steps are involved: (1) First, pre-treat the diamond powder and prepare a chemical plating solution by mixing 40-80 g / L citric acid, 40-80 g / L sodium hypophosphite, 0.0014-1 g / L thiourea and 2-10 ml / L lactic acid, and finally adjusting the pH value of the chemical plating solution to 6-9 with ammonia water; after preparing the chemical plating solution, add the diamond powder and stir mechanically at a stirring speed of 150-180 r / min, heat in a water bath at 35-70°C for 2-4 hours, increase the liquid replenishment during the stirring process, maintain the concentration of the chemical plating solution, and increase the weight of the coating by 5-35%; (2) preparing a nickel electroplating solution for the diamond powder after chemical plating in step (1), adding 150-300 g / L nickel sulfate, 5-15 g / L nickel chloride, and 30-45 g / L boric acid, and adjusting the pH value of the electroplating solution to 3-5, the plating bottle speed to 1-60 r / min, and monitoring the pH value of the electroplating solution every 30 min; (3) Post-processing the diamond powder after electroplating, washing and sieving to remove the electroplating solution and other impurities on the surface of the diamond powder composite coating; (4) Conduct characterization tests on the composite coating, including coating weight gain rate, coating density and coating corrosion resistance tests.

2. A diamond surface composite plating process according to claim 1, characterized in that: Before the chemical plating in step (1), the nickel block and the cathode wire are immersed in dilute hydrochloric acid to remove the oxide film, and then the treated nickel block is used as the anode and the cathode wire is used as the cathode.

3. A diamond surface composite plating process according to claim 1, characterized in that: The diamond micropowder has a D50 value of 1.0-500.

4. A diamond surface composite plating process according to claim 1, characterized in that: The electroplating in step (2) is performed by roller plating, the electroplating current is 0.5-20A, and the electroplating loading amount is 500-5000g.

5. A diamond surface composite plating process according to claim 1, characterized in that: The coating weight gain rate in step (4) is expressed as the ratio of the difference in mass of diamond powder before electroplating to the mass before electroplating per unit time, and m3 is the mass of diamond powder after electroplating.

6. A diamond surface composite plating process according to claim 1, characterized in that: The coating density in step (4) is expressed as the coating mass per unit volume. The shape of diamond micropowder particles is often irregular under microscope observation. For the convenience of calculation, the shape of diamond particles is approximated as a sphere. The equivalent volume particle size of diamond micropowder before and after coating is measured by a laser particle size analyzer as the average particle size r0 and r1. The diamond density is ρ0 (3.5 g / cm 3 ), n in (2) represents the number of particles in 3g of diamond powder, and the coating density ρ1 is calculated using formula (3):

7. A diamond surface composite plating process according to claim 1, characterized in that: The coating morphology in the step (4) is as follows: the coating morphology on the surface of the diamond powder is observed using a scanning electron microscope.

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