A chemical copper plating process for cemented carbide surface

Abstract

The present application relates to the field of metal surface treatment, and specifically discloses a process for chemical copper plating on a cemented carbide surface, comprising the following steps: S1, cleaning; S2, intermediate layer treatment: using plasma spraying to coat the composite powder after mixing Co-25Cr-8W alloy powder with Ni-5Al and aluminum oxide on the surface of the cemented carbide substrate after cleaning in step S1 to form an intermediate layer, to obtain a pretreated substrate; S3, activation: the pretreated substrate is first activated in an acidic palladium chloride solution, then ultrasonically treated in a nanosilver colloid solution after cleaning, and then dried after washing to obtain an activated substrate; S4, chemical copper plating: the obtained activated substrate is placed in a chemical copper plating solution containing a copper salt, a reducing agent and a stabilizer for chemical plating to form a copper plating layer, to obtain a copper-plated substrate; S4, post-processing to obtain a copper-plated cemented carbide. The present application has the characteristics of improving the bonding strength between the copper plating layer and the cemented carbide substrate.

Description

Technical Field

[0001] The present invention relates to the field of metal surface treatment, and more specifically, to a process for chemical copper plating on a cemented carbide surface. Background Art

[0002] In the aerospace field, fasteners are key connectors, and their performance directly affects the structural safety and reliability of aircraft. Cemented carbide materials are widely used in the manufacture of high-strength bolts, screws and other accessories due to their high hardness, wear resistance, high temperature resistance and corrosion resistance. However, there are natural defects on the surface of cemented carbide. When cemented carbide is used, such as in the aluminum alloy brackets in the engine compartment, which need to be fixed with cemented carbide bolts to high-temperature components (such as titanium alloy turbine blades), electrochemical corrosion occurs when cemented carbide comes into contact with active metals such as aluminum alloy, limiting its adaptability in complex working conditions. Electrochemical corrosion can cause local perforation or failure of the aluminum alloy base material, threatening flight safety. Therefore, surface treatment of cemented carbide is crucial to its oxidation resistance and corrosion resistance.

[0003] Although traditional surface treatment technologies such as electroplating copper can improve the surface properties of cemented carbide, the bonding strength between electroplating and cemented carbide substrate is usually insufficient, and it is prone to falling off or failure under extreme conditions such as high temperature and vibration. It cannot meet the stringent requirements of the aerospace field for long-term reliability. In addition, electroplating requires an external power supply, and it is difficult to ensure the uniformity of the coating on workpieces with complex shapes. Chemical copper plating deposits a copper layer on the surface of the substrate through an autocatalytic reaction. It does not require an external power supply and can evenly cover workpieces with complex morphologies. It is especially suitable for precision structures such as fastener threads. However, the bonding strength between the coating and the cemented carbide substrate of the current chemical copper plating process is unstable. Since the carbide of cemented carbide has high hardness and low surface energy, it is difficult for the plating solution to spread on its surface, resulting in poor wettability of the cemented carbide surface, resulting in insufficient bonding between the chemical copper plating layer and the cemented carbide substrate, affecting the adhesion of the copper plating layer. Therefore, the chemical copper plating process needs to be further improved to improve the bonding strength of the coating. Summary of the Invention

[0004] In order to improve the bonding strength between the copper plating layer and the cemented carbide substrate, the present application provides a chemical copper plating process for cemented carbide surface.

[0005] This application provides a process for chemical copper plating on cemented carbide surfaces, which adopts the following technical solutions:

[0006] A process for chemical copper plating on a cemented carbide surface comprises the following steps:

[0007] S1. Cleaning: Use acetone organic solvent to clean the cemented carbide substrate;

[0008] S2, intermediate layer treatment: using plasma spraying to coat a composite powder obtained by mixing Co-25Cr-8W alloy powder with Ni-5Al and alumina on the surface of the cemented carbide substrate cleaned in step S1 to form an intermediate layer, thereby preparing a pretreated substrate;

[0009] S3, activation: the pretreated substrate treated in step S2 is first activated in an acidic palladium chloride solution, then cleaned and ultrasonically treated in a nanosilver colloidal solution, washed with water, and then dried to obtain an activated substrate;

[0010] S4, chemical copper plating: placing the prepared activated substrate in a chemical copper plating solution containing a copper salt, a reducing agent, and a stabilizer to perform chemical plating to form a copper plating layer, thereby preparing a copper-plated substrate;

[0011] S4, post-processing: cleaning and drying the copper-plated substrate obtained after the treatment in step S4 to obtain a copper-plated cemented carbide.

[0012] By adopting the above technical solution, in this application, the oil and impurities on the surface of the cemented carbide are first removed by organic solvent cleaning, providing a good foundation for subsequent processing. Then, a composite powder obtained by mixing Co-25Cr-8W alloy powder and Ni-5Al is coated on the surface of the cemented carbide substrate by plasma spraying to form an intermediate layer. The Co element in the alloy powder has good chemical compatibility with the Co element in the cemented carbide substrate. During the plasma spraying process, they dissolve each other to form a certain degree of diffusion layer, forming a strong metallurgical bond and achieving chemical bonding. Finally, a local metallurgical fusion zone is formed between the intermediate layer and the substrate, which significantly improves the bonding strength.

[0013] The addition of Cr and W to the alloy powder not only utilizes their high melting point properties to ensure a strong bond between the coating and the substrate during plasma spraying, but also the Cr element improves oxidation resistance and corrosion resistance, the W element enhances hardness, and the Co element on the surface after spraying can also serve as a reducing agent for palladium salt reduction. The nickel element and the Co element in the Ni-5Al alloy have similar crystal structures and chemical properties, forming a continuous solid solution. During the plasma spraying process, the nickel element diffuses with the Co element and the W element to form a uniform alloy layer, achieving chemical bonding with the intermediate layer. Moreover, during the electroless copper plating process, copper atoms can diffuse on the nickel surface to form a copper-nickel alloy transition layer. In addition, the oxide film (such as NiO) on the nickel surface can also undergo certain chemical reactions with copper ions, promoting copper deposition and bonding. The addition of aluminum oxide can form an intermediate layer with a certain degree of roughness, forming a mechanical locking effect with the cemented carbide substrate and improving bonding strength. At the same time, in this application, Ni-5Al alloy powder and alumina particles are introduced as part of the intermediate layer and are surrounded by Co-25Cr-8W alloy powder. Subsequently, chemical copper plating is performed to form a copper plating layer. Therefore, the introduction of the above-mentioned aluminum element will not affect the problem of electrochemical corrosion caused by the need to isolate the cemented carbide substrate from direct contact with the external aluminum material in this application, but will help improve the corrosion resistance of the coating.

[0014] After the intermediate layer is sprayed and formed, palladium salt reduction is first carried out under acidic conditions. The Co remaining on the surface of the intermediate layer after spraying directly acts as a reducing agent in the subsequent palladium salt activation, making Pd 2+ Selectively reduced with Co to form island-shaped Pd 0 The catalytic core and the palladium salt activation layer serve as the catalytic core of chemical copper plating, accelerating the reduction reaction of copper ions. The island-shaped catalytic core formed provides more reaction sites, which is conducive to the uniform deposition of copper ions. The nanosilver colloid ultrasonic treatment allows the nanosilver to be embedded in the gaps of the palladium activation layer. Silver and palladium form a primary battery in the micro area (Ag as anode and Pd as cathode). The formation of a micro-battery effect can accelerate the subsequent reduction process of copper ions and realize chemical copper plating.

[0015] The intermediate layer composite powder in this application not only utilizes the nickel element and elements such as Co in the cemented carbide substrate during the plasma spraying process, the nickel element and the Co element and the W element diffuse into each other to form a continuous solid solution and form a chemical bond, but also the plasma spraying technology can form a layer of rough intermediate layer on the surface of the cemented carbide substrate. This roughness provides a mechanical anchoring effect, allowing the subsequent copper plating layer to be embedded in the tiny bumps of the intermediate layer like a "nail", forming a "pinning" effect. This mechanical anchoring effect strengthens the bonding between the copper plating layer and the intermediate layer, thereby indirectly improving the overall bonding between the copper plating layer and the cemented carbide substrate; and the chemical metallurgical effect formed between the intermediate layer and the cemented carbide substrate makes the bonding strength between the intermediate layer and the cemented carbide substrate better. In addition, during the activation step, the nanosilver particles and Pd form a micro-area galvanic cell effect, further accelerating the reduction rate of copper ions, improving the uniformity and density of the copper plating layer, and thus further strengthening the bonding between the coating and the substrate. At the same time, the embedding of the nanosilver particles also increases the contact area and bonding between the coating and the substrate, which is conducive to forming a more solid coating.

[0016] Finally, in this application, the bonding strength between the copper plating layer and the cemented carbide substrate is significantly improved through the intermediate layer treatment and activation steps, and the plating layer is more uniform and dense, thereby improving the plating quality.

[0017] Optionally, in step S2, the mass proportion of Ni-5Al in the composite powder is 10-30%, the mass proportion of aluminum oxide is 5-10%, and the balance is Co-25Cr-8W alloy powder.

[0018] By adopting the above technical solution, the Ni-5Al ratio control can achieve chemical bonding between the intermediate layer and the cemented carbide substrate and the copper-plated layer. On this basis, in this application, alumina is used as a high-hardness ceramic particle, which is combined with the molten Co-25Cr-8W alloy powder during the plasma spraying process to form a rough surface structure. The mechanical bite significantly improves the interface bonding force between the intermediate layer and the cemented carbide base layer, and between the intermediate layer and the copper-plated layer. In addition, the thermal expansion coefficient of alumina is between that of cemented carbide and copper, which can effectively alleviate the interfacial thermal stress, reduce the risk of coating cracking leading to coating shedding and reduced corrosion resistance, and the chemical properties of alumina are stable, which will not affect the activation process during the subsequent acidic activation of palladium solution, and the intermediate layer has good chemical stability.

[0019] Optionally, in step S2 , the thickness of the intermediate layer is 2-5 μm.

[0020] By adopting the above technical solution, when the thickness of the intermediate layer is relatively small, the effect of increasing the roughness of aluminum oxide to improve the bonding strength through mechanical locking is limited. Therefore, in this application, by controlling the raw materials and thickness of the intermediate layer, it is possible to combine mechanical locking with chemical metallurgy at a relatively small thickness, thereby significantly improving the bonding performance between the copper plating layer and the cemented carbide substrate, and also meeting the coating thickness processing requirements of cemented carbide fasteners.

[0021] Optionally, in step S2, the plasma spraying adopts a supersonic plasma spraying process, the spraying distance is 50-80 mm, the spraying power is 50-80 kW, the plasma gas is a mixture of argon and hydrogen, the argon flow rate is 30-50 slpm, and the hydrogen flow rate is 3-8 slpm.

[0022] Optionally, after the plasma spraying in step S2 is completed, heat treatment is performed at 800-1000° C. for 1-2 hours, and then cooled to room temperature to perform step S3.

[0023] By adopting the above technical solution, heat treatment is performed after plasma spraying to eliminate internal stress and improve interface bonding strength.

[0024] Optionally, in step S3, the concentration of palladium chloride in the palladium chloride solution is 0.1-0.5 g / L, and the pH of the palladium chloride solution is adjusted to 1.5-2.5 by hydrochloric acid. When the pretreated substrate is activated in the palladium chloride solution, the treatment temperature is 35-40° C. and the treatment time is 5-10 min. The substrate is then washed with water, dried with nitrogen, and then ultrasonically treated in a nanosilver colloidal solution.

[0025] Optionally, in step S3, when the pretreated substrate activated by the acidic palladium chloride solution is treated in a nanosilver colloidal solution, the treatment temperature is 20-25° C., the treatment time is 5-15 min, the ultrasonic power is 100-200 W, and after ultrasonic treatment, the substrate is washed with water and then dried with cold air to obtain an activated substrate.

[0026] By adopting the above technical solution, in the present application, under the conditions of acidic palladium chloride, Pd 2+ Through a displacement reaction, the silver ions are adsorbed on the surface of the pretreated substrate, forming catalytic active sites. Ultrasonic action causes the silver ions to embed into the pores of the intermediate layer. The silver nanoparticles and Pd form a micro-region galvanic cell effect, further accelerating the reduction rate of copper ions and improving the uniformity and density of the copper plating layer, thereby further strengthening the bonding between the coating and the substrate. At the same time, the embedding of the silver nanoparticles also increases the contact area and bonding strength between the coating and the substrate, which is conducive to the formation of a more solid coating.

[0027] Optionally, in step S4, the chemical copper plating solution includes the following raw materials:

[0028] 10-20 g / L copper sulfate, 15-20 g / L EDTA, 3-5 g / L ammonium citrate, 5-10 g / L potassium sodium tartrate, 0.05-0.15 g / L thiourea, and 0.03-0.08 g / L polyvinylpyrrolidone.

[0029] By adopting the above technical solution, copper sulfate in the chemical copper plating solution of the present application is used as a copper salt, EDTA is used as a chelating agent to form a complex with copper ions to stabilize the concentration of free copper ions, and potassium sodium tartrate is used as an auxiliary chelating agent to form a soluble complex with copper ions under alkaline conditions to prevent the local copper concentration from being too high. Ammonium citrate can be used as a buffer to stabilize the pH value of the plating solution and can also cooperate with EDTA to adjust the copper ion concentration. Finally, a multi-coordinated complex matrix is ​​used in the present application, EDTA is used as a dominant strong complex, tartaric acid is used as a quadridentate ligand, and citric acid is used as a tridentate ligand. It forms a dynamic buffer, a gradient complex network, controls the release rate of copper ions, and inhibits abnormal grain growth. Thiourea acts as a side reaction inhibitor to inhibit the disproportionation reaction of copper ions, while the polar groups of polyvinyl pyrrolidone are adsorbed around the copper ions to form a protective layer, preventing the copper ions from prematurely agglomerating into large particles, which helps to evenly distribute the copper ions in the plating solution, so that the copper ions are evenly deposited on the surface of the substrate, forming small and uniform copper grains, reducing defects, and improving the bonding strength between the plating layer and the intermediate layer, thereby ultimately improving the bonding strength between the copper plating layer and the cemented carbide substrate.

[0030] Optionally, in step S4, the pH value of the chemical copper plating solution is 12-13, and the plating solution temperature is 40-50°C.

[0031] Optionally, 1.5-3 g / L of nickel sulfate and 0.1-0.3 g / L of benzodiazepine are further added to the chemical copper plating solution in step S4.

[0032] By adopting the above technical solution, when nickel sulfate is added to the electroless copper plating solution in this application, nickel ions co-deposit with copper ions during the electroless plating process to form a Cu-Ni alloy transition layer, thereby forming a metallurgical bond with the Ni skeleton of the intermediate layer. Furthermore, the aluminum oxide particles in the intermediate layer have a negative surface charge under highly alkaline conditions, which can adsorb nickel ions in the plating solution to form Ni-Al2O3 active sites, improving the occlusion between the coating and the intermediate layer. Furthermore, the addition of nickel further matches the thermal expansion coefficient of the Cu-Ni alloy formed with the Ni-5Al intermediate layer, reducing interfacial stress and improving the bonding strength between the coating and the substrate. Benzopropanone can form coordination bonds with the copper surface, enhancing the adhesion of the coating to the intermediate layer and improving the bonding strength.

[0033] In summary, this application has the following beneficial effects:

[0034] 1. The intermediate layer composite powder in this application not only utilizes the diffusion of nickel, Co, and W elements in the cemented carbide substrate during the plasma spraying process to form a continuous solid solution and chemical bond, but also uses plasma spraying technology to form a rough intermediate layer on the surface of the cemented carbide substrate. This roughness provides a mechanical anchoring effect, enhancing the bonding between the copper plating layer and the intermediate layer, thereby indirectly improving the overall bonding between the copper plating layer and the cemented carbide substrate; the chemical metallurgical effect formed between the intermediate layer and the cemented carbide substrate further enhances the bonding strength between the intermediate layer and the cemented carbide substrate;

[0035] 2. After the intermediate layer is sprayed and formed, palladium salt reduction is first carried out under acidic conditions. The Co remaining on the surface of the intermediate layer after spraying directly acts as a reducing agent in the subsequent palladium salt activation, making Pd 2+ Selectively reduced with Co to form island-shaped Pd 0 Catalytic core: The palladium salt activation layer serves as the catalytic core of chemical copper plating, accelerating the reduction reaction of copper ions. The island-shaped catalytic core formed provides more reaction sites, which is conducive to the uniform deposition of copper ions. The nanosilver colloid ultrasonic treatment allows the nanosilver to be embedded in the gaps of the palladium activation layer. Silver and palladium form a primary battery in the micro-region (Ag as anode and Pd as cathode). The micro-battery effect can accelerate the subsequent reduction process of copper ions and realize chemical copper plating. At the same time, the embedding of nanosilver particles also increases the contact area and bonding force between the coating and the substrate, which is conducive to the formation of a more solid coating.

[0036] 3. In the present application, when nickel sulfate is also added to the electroless copper plating solution, on the one hand, nickel ions co-deposit with copper ions during the electroless plating process to form a Cu-Ni alloy transition layer, thereby forming a metallurgical bond with the Ni skeleton of the intermediate layer. On the other hand, the aluminum oxide particles in the intermediate layer have a negative surface charge under high alkaline conditions, which can adsorb nickel ions in the plating solution to form Ni-Al2O3 active sites, thereby improving the occlusion between the coating and the intermediate layer. Moreover, after adding nickel, the Cu-Ni alloy formed has a better match in thermal expansion coefficient with the intermediate layer containing Ni-5Al, thereby reducing interfacial stress and improving the bonding strength between the coating and the substrate. DETAILED DESCRIPTION

[0037] The present application is further described in detail below with reference to the examples. It is particularly noted that if no specific conditions are specified in the following examples, the reactions are carried out according to conventional conditions or the conditions recommended by the manufacturer. Unless otherwise specified, the raw materials used in the following examples can be obtained from common commercial sources.

[0038] In this application, the Co-25Cr-8W alloy powder is a cobalt-based alloy containing 25wt% Cr and 8wt% W, with the remainder being Co. Similarly, the Ni-5Al alloy powder is an alloy powder containing 5wt% Al and the remainder being nickel. The above-mentioned Co-25Cr-8W alloy powder and Ni-5Al alloy powder can be obtained from ordinary commercial sources, or the above-mentioned alloy powder can be produced by a gas atomization method and then ball-milled to a particle size of 20-100nm.

[0039] The nano silver colloidal solutions in the following examples were prepared by the following method:

[0040] Silver nitrate, sodium borohydride, and sodium citrate were weighed in a mass ratio of 30:1:7, and then the silver nitrate was dissolved in water to form a 0.05 mol / L silver nitrate solution; sodium borohydride was weighed and dissolved in water under ice bath conditions to prepare a 0.05 mol / L sodium borohydride solution; sodium citrate was dissolved in water to prepare a 0.05 mol / L sodium citrate solution;

[0041] The silver nitrate solution was placed in an ice bath and magnetically stirred, and then the sodium borohydride solution was added dropwise to the silver nitrate solution at a dropping speed of 5 drops / min. After the sodium borohydride solution was added dropwise, the reaction was allowed to proceed for 5 minutes, and the color of the solution changed from colorless to dark brown. Then, the sodium citrate solution was added and stirred for 40 minutes. After the reaction was completed, the supernatant was removed by centrifugation, and the precipitate was collected and washed with water to remove impurities to obtain nanosilver, which was then mixed with water at a ratio of 1 mg:1 ml to obtain a nanosilver colloidal solution with a concentration of 0.1 mg / ml.

[0042] The cemented carbide in the following examples is grade K465 (WC-12% Co+TaC).

[0043] Example 1

[0044] A process for chemical copper plating on a cemented carbide surface, comprising the following steps:

[0045] S1. Cleaning: Use acetone organic solvent to clean the cemented carbide substrate to remove impurities;

[0046] S2. Intermediate layer treatment: Co-25Cr-8W alloy powder is mixed with Ni-5Al and alumina according to the following mass percentages to prepare a composite powder: 20% Ni-5Al alloy powder, 8% alumina powder (particle size of 800-1200 nm), and the remainder Co-25Cr-8W alloy powder;

[0047] Then, the composite powder is coated on the surface of the cemented carbide substrate cleaned in step S1 by a supersonic plasma spraying process to form an intermediate layer, and then heat treated at 900° C. for 1.5 hours and cooled to room temperature to obtain a pretreated substrate;

[0048] The supersonic plasma spraying process parameters are as follows: spraying distance 60 mm, spraying power 60 kW, spraying thickness 3 μm, plasma gas is a mixture of argon and hydrogen, with argon flow rate 40 slpm and hydrogen flow rate 5 slpm;

[0049] S3, activation: specifically comprising the following steps:

[0050] S3-1, adding hydrochloric acid to a palladium chloride solution having a concentration of 0.3 g / L to adjust the pH of the palladium chloride solution to 2 to obtain an acidic palladium chloride solution;

[0051] S3-2, then activating the pretreated substrate after step S2 in an acidic palladium chloride solution at a temperature of 40° C. for 5 minutes, then washing with water and drying with nitrogen;

[0052] S3-3, ultrasonically treating the pretreated substrate treated in S3-2 in a nanosilver colloidal solution, wherein the concentration of the nanosilver colloidal solution is 0.1 g / L, and the pH value of the nanosilver colloidal solution is adjusted to 4.5, the ultrasonic treatment time is 10 min, the treatment temperature is 25° C., and the ultrasonic power is 150 W. After the ultrasonic treatment, the substrate is washed with water and dried with nitrogen to obtain an activated substrate;

[0053] S4, chemical copper plating: placing the prepared activated substrate in a chemical copper plating solution with a pH value of 12.5 for chemical plating to form a copper plating layer with a thickness of 8 μm and a plating solution temperature of 45° C., to prepare a copper-plated substrate;

[0054] Among them, the chemical copper plating solution includes the following raw materials:

[0055] 15 g / L copper sulfate, 18 g / L EDTA, 4 g / L ammonium citrate, 8 g / L potassium sodium tartrate, 12 g / L sodium hypophosphite, 0.1 g / L thiourea, and 0.05 g / L polyvinylpyrrolidone;

[0056] S4, post-processing: cleaning and drying the copper-plated substrate obtained after the treatment in step S4 to obtain a copper-plated cemented carbide.

[0057] Example 2

[0058] A process for chemical copper plating on a cemented carbide surface, comprising the following steps:

[0059] S1. Cleaning: Use acetone organic solvent to clean the cemented carbide substrate to remove impurities;

[0060] S2. Intermediate layer treatment: Co-25Cr-8W alloy powder is mixed with Ni-5Al and alumina according to the following mass percentages to prepare a composite powder: 10% Ni-5Al alloy powder, 5% alumina powder (particle size of 800-1200 nm), and the remainder Co-25Cr-8W alloy powder;

[0061] Then, the composite powder is coated on the surface of the cemented carbide substrate cleaned in step S1 by a supersonic plasma spraying process to form an intermediate layer, and then heat-treated at 800° C. for 2 hours and cooled to room temperature to obtain a pretreated substrate;

[0062] The supersonic plasma spraying process parameters are as follows: spraying distance 50 mm, spraying power 50 kW, spraying thickness 2 μm, plasma gas is a mixture of argon and hydrogen, with argon flow rate 30 slpm and hydrogen flow rate 3 slpm;

[0063] S3, activation: specifically comprising the following steps:

[0064] S3-1, adding hydrochloric acid to a palladium chloride solution having a concentration of 0.1 g / L to adjust the pH of the palladium chloride solution to 1.5 to obtain an acidic palladium chloride solution;

[0065] S3-2, then activating the pretreated substrate after step S2 in an acidic palladium chloride solution at a temperature of 35° C. for 10 min, then washing with water and drying with nitrogen;

[0066] S3-3, ultrasonically treating the pretreated substrate treated in S3-2 in a nanosilver colloidal solution, wherein the concentration of the nanosilver colloidal solution is 0.1 g / L, and the pH value of the nanosilver colloidal solution is adjusted to 4.5, the ultrasonic treatment time is 5 minutes, the treatment temperature is 20° C., and the ultrasonic power is 100 W. After the ultrasonic treatment, the substrate is washed with water and dried with nitrogen to obtain an activated substrate;

[0067] S4, chemical copper plating: placing the prepared activated substrate in a chemical copper plating solution with a pH value of 12 for chemical plating to form a copper plating layer with a thickness of 9 μm and a plating solution temperature of 40° C., thereby preparing a copper-plated substrate;

[0068] Among them, the chemical copper plating solution includes the following raw materials:

[0069] 10 g / L copper sulfate, 15 g / L EDTA, 3 g / L ammonium citrate, 5 g / L potassium sodium tartrate, 8 g / L sodium hypophosphite, 0.05 g / L thiourea, and 0.03 g / L polyvinylpyrrolidone;

[0070] S4, post-processing: cleaning and drying the copper-plated substrate obtained after the treatment in step S4 to obtain a copper-plated cemented carbide.

[0071] Example 3

[0072] A process for chemical copper plating on a cemented carbide surface, comprising the following steps:

[0073] S1. Cleaning: Use acetone organic solvent to clean the cemented carbide substrate to remove impurities;

[0074] S2. Intermediate layer treatment: Co-25Cr-8W alloy powder is mixed with Ni-5Al and alumina according to the following mass percentages to prepare a composite powder: 30% Ni-5Al alloy powder, 10% alumina powder (particle size of 800-1200 nm), and the remainder Co-25Cr-8W alloy powder;

[0075] Then, the composite powder is coated on the surface of the cemented carbide substrate cleaned in step S1 by a supersonic plasma spraying process to form an intermediate layer, and then heat-treated at 1000° C. for 1 hour and cooled to room temperature to obtain a pretreated substrate;

[0076] The supersonic plasma spraying process parameters are as follows: spraying distance 80 mm, spraying power 80 kW, spraying thickness 5 μm, plasma gas is a mixture of argon and hydrogen, with argon flow rate 50 slpm and hydrogen flow rate 8 slpm;

[0077] S3, activation: specifically comprising the following steps:

[0078] S3-1, adding hydrochloric acid to a palladium chloride solution having a concentration of 0.5 g / L to adjust the pH of the palladium chloride solution to 2.5 to obtain an acidic palladium chloride solution;

[0079] S3-2, then activating the pretreated substrate after step S2 in an acidic palladium chloride solution at a temperature of 40° C. for 5 minutes, then washing with water and drying with nitrogen;

[0080] S3-3, ultrasonically treating the pretreated substrate treated in S3-2 in a nanosilver colloidal solution, wherein the concentration of the nanosilver colloidal solution is 0.1 g / L, and the pH value of the nanosilver colloidal solution is adjusted to 6, the ultrasonic treatment time is 15 min, the treatment temperature is 25° C., and the ultrasonic power is 200 W. After the ultrasonic treatment, the substrate is washed with water and dried with nitrogen to obtain an activated substrate;

[0081] S4, chemical copper plating: placing the prepared activated substrate in a chemical copper plating solution with a pH value of 12-13 for chemical plating to form a copper plating layer with a thickness of 6 μm and a plating solution temperature of 50° C., to prepare a copper-plated substrate;

[0082] Among them, the chemical copper plating solution includes the following raw materials:

[0083] 20 g / L copper sulfate, 20 g / L EDTA, 5 g / L ammonium citrate, 10 g / L potassium sodium tartrate, 18 g / L sodium hypophosphite, 0.15 g / L thiourea, and 0.08 g / L polyvinylpyrrolidone;

[0084] S4, post-processing: cleaning and drying the copper-plated substrate obtained after the treatment in step S4 to obtain a copper-plated cemented carbide.

[0085] Example 4

[0086] A process for chemical copper plating on a cemented carbide surface is carried out according to the method in Example 1, except that 2 g / L nickel sulfate and 0.2 g / L benzodiazepine are further added to the chemical copper plating solution in step S4.

[0087] Example 5

[0088] A process for chemical copper plating on a cemented carbide surface is carried out according to the method in Example 1, except that 1.5 g / L nickel sulfate and 0.1 g / L benzodiazepine are further added to the chemical copper plating solution in step S4.

[0089] Example 6

[0090] A process for chemical copper plating on a cemented carbide surface is carried out according to the method in Example 1, except that 3 g / L nickel sulfate and 0.3 g / L benzodiazepine are further added to the chemical copper plating solution in step S4.

[0091] Example 7

[0092] A process for chemical copper plating on a cemented carbide surface is carried out according to the method in Example 1, except that 2 g / L of nickel sulfate is further added to the chemical copper plating solution in step S4.

[0093] Example 8

[0094] A process for chemical copper plating on a cemented carbide surface is carried out according to the method in Example 1, except that no thiourea is added to the chemical copper plating solution in step S4.

[0095] Example 9

[0096] A process for chemical copper plating on a cemented carbide surface is carried out according to the method in Example 1, except that polyvinyl pyrrolidone is not added to the chemical copper plating solution in step S4.

[0097] Comparative Example 1

[0098] A process for chemical copper plating on a cemented carbide surface is carried out according to the method in Example 1, except that step S3 is not processed in step S3-3, and the activated substrate after nitrogen drying after step S3-2 is directly processed in step S4.

[0099] Comparative Example 2

[0100] A process for chemical copper plating on a cemented carbide surface is carried out according to the method in Example 1, except that step S2 is not performed.

[0101] Comparative Example 3

[0102] A process for chemical copper plating on a cemented carbide surface is carried out according to the method in Example 1, except that in step S2, an equal amount of alumina powder in the composite powder is replaced by Co-25Cr-8W alloy powder.

[0103] Comparative Example 4

[0104] A process for chemical copper plating on a cemented carbide surface is carried out according to the method in Example 1, except that the composite powder in step S2 is Co-25Cr-8W alloy powder.

[0105] Comparative Example 5

[0106] A process for chemical copper plating on a cemented carbide surface is carried out according to the method in Example 1, except that in step S2, an equal amount of Ni-5Al alloy powder is replaced by Co-25Cr-8W alloy powder.

[0107] Performance testing

[0108] Chemical copper plating was performed on the cemented carbide according to the process in the above-mentioned embodiment and comparative example, and the copper-plated cemented carbide obtained in the embodiment and comparative example of the present application was subjected to a thermal shock test, specifically: heating to 300°C and keeping warm for 2 hours, then water-cooling to room temperature, continuing to heat to 300°C and then water-cooling, and repeating the cycle 30 times to calculate the percentage of coating peeling area. The statistical results are shown in Table 1 below.

[0109] Table 1:

[0110]

[0111] Referring to the test results in Table 1 above, the coating formed by the copper plating process in the present application has excellent bonding strength with the cemented carbide substrate. Referring to the test results of Example 1 and Examples 4-6, when nickel sulfate and benzodiazolidine are also added to the chemical copper plating solution, the bonding strength of the coating and the substrate is further significantly improved. Combined with the test results of Example 7, when only nickel sulfate is added to the chemical copper plating solution without benzodiazolidine, the bonding strength is reduced. Combined with the test results of Example 8 and Example 9, when thiourea or polyvinyl pyrrolidone is not added to the chemical copper plating solution, the bonding strength of the coating is also reduced. The addition of the above substances helps to uniformly plate copper and improve the bonding strength with the substrate.

[0112] Referring to the test results of Example 1 and Comparative Example 1, during the activation treatment step, when only palladium chloride activation treatment was performed without treatment in the nanosilver colloidal solution, the adhesion was also significantly reduced. Combined with the test results of Comparative Example 2, when the copper plating treatment was performed directly after activation without forming an intermediate layer, the bonding strength was significantly reduced. Combined with the test results of Comparative Examples 3-5, when only Co-25Cr-8W alloy powder was added to the composite powder, although its adhesion was improved compared to Comparative Example 2, the improvement was small. When two composites were selected in Comparative Examples 3 and 5, the bonding performance was still weak.

[0113] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A process for chemical copper plating on a cemented carbide surface, characterized in that: The following steps are involved: S1, cleaning: using acetone organic solvent to clean the K465 cemented carbide substrate; S2, intermediate layer treatment: using plasma spraying to coat the composite powder obtained by mixing Co-25Cr-8W alloy powder with Ni-5Al and aluminum oxide on the surface of the cemented carbide substrate cleaned in step S1 to form an intermediate layer, thereby obtaining a pretreated substrate; S3, activation: first activating the pretreated substrate treated in step S2 in an acidic palladium chloride solution, then ultrasonically treating it in a nanosilver colloid solution after cleaning, washing it with water, and then drying it to obtain an activated substrate; S4, chemical copper plating: placing the obtained activated substrate in a chemical copper plating solution containing a copper salt, a reducing agent, and a stabilizer to perform chemical plating to form a copper plating layer, thereby obtaining a copper-plated substrate; S5, post-treatment: cleaning and drying the copper-plated substrate obtained after the treatment in step S4 to obtain a copper-plated cemented carbide; In step S2, the composite powder comprises 10-30% by mass of Ni-5Al, 5-10% by mass of alumina, and the remainder is Co-25Cr-8W alloy powder; In step S4, the chemical copper plating solution includes the following raw materials: 10-20 g / L copper sulfate, 15-20 g / L EDTA, 3-5 g / L ammonium citrate, 5-10 g / L potassium sodium tartrate, 8-18 g / L sodium hypophosphite, 0.05-0.15 g / L thiourea and 0.03-0.08 g / L polyvinylpyrrolidone, 1.5-3 g / L nickel sulfate and 0.1-0.3 g / L benzodiazepine.

2. The process for chemical copper plating on a cemented carbide surface according to claim 1, wherein: The thickness of the intermediate layer in step S2 is 2-5 μm.

3. The process for chemical copper plating on a cemented carbide surface according to claim 1, wherein: In step S2, the plasma spraying adopts a supersonic plasma spraying process, the spraying distance is 50-80 mm, the spraying power is 50-80 kW, the plasma gas is a mixed gas of argon and hydrogen, the argon flow rate is 30-50 slpm, and the hydrogen flow rate is 3-8 slpm.

4. The process for chemical copper plating on a cemented carbide surface according to claim 1, wherein: After the plasma spraying in step S2 is completed, the substrate is heat treated at 800-1000° C. for 1-2 hours and then cooled to room temperature for step S3.

5. The process for chemical copper plating on a cemented carbide surface according to claim 1, wherein: In step S3, the concentration of palladium chloride in the palladium chloride solution is 0.1-0.5 g / L, and the pH of the palladium chloride solution is adjusted to 1.5-2.5 by hydrochloric acid. When the pre-treated substrate is activated in the palladium chloride solution, the treatment temperature is 35-40° C. and the treatment time is 5-10 minutes. Then, the substrate is washed with water, dried with nitrogen, and then ultrasonically treated in a nanosilver colloidal solution.

6. The process for chemical copper plating on a cemented carbide surface according to claim 1, wherein: In step S3, the pretreated substrate activated by the acidic palladium chloride solution is treated in a nanosilver colloidal solution at a treatment temperature of 20-25° C., a treatment time of 5-15 min, and an ultrasonic power of 100-200 W. After the ultrasonic treatment, the substrate is washed with water and then dried with cold air to obtain an activated substrate.

7. The process for chemical copper plating on a cemented carbide surface according to claim 1, wherein: In step S4, the pH value of the chemical copper plating solution is 12-13, and the plating solution temperature is 40-50°C.

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