Chemical copper plating process for hard alloy surface

Abstract

The invention relates to the field of metal surface treatment, and particularly discloses a hard alloy surface chemical copper plating process which comprises the following steps: S1, cleaning; s2, intermediate layer treatment: coating the surface of the hard alloy base material cleaned in the step S1 with composite powder formed by mixing Co-25Cr-8W alloy powder, Ni-5Al and aluminum oxide by adopting plasma spraying to form an intermediate layer, so as to prepare a pretreated base material; s3, activation: firstly activating the pretreated substrate in an acidic palladium chloride solution, cleaning, then carrying out ultrasonic treatment in a nano-silver colloidal solution, washing with water, and blow-drying to obtain an activated substrate; s4, chemical copper plating is conducted, specifically, the prepared activated base material is placed in chemical copper plating liquid containing copper salt, a reducing agent and a stabilizing agent to be subjected to chemical plating to form a copper plating layer, and a copper plating base material is prepared; and S4, carrying out post-treatment to obtain the copper-plated hard alloy. The method has the characteristic of improving the binding force of the copper plating layer and the hard alloy base material.

Description

Technical Field

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

[0002] In the field of aerospace, 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 the aluminum alloy bracket in the engine compartment, which needs to be fixed with cemented carbide bolts to fix high-temperature components (such as titanium alloy turbine blades), electrochemical corrosion occurs when cemented carbide contacts with active metals such as aluminum alloy, limiting its adaptability under 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 for 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 easy to fall off or fail 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 external power supply, and it is difficult to ensure the uniformity of the coating on complex-shaped workpieces. 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 morphology. 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 on the cemented carbide surface.

[0005] The present application provides a process for chemical copper plating on a cemented carbide surface, which adopts the following technical solution: A process for chemical copper plating on a cemented carbide surface comprises the following steps: S1. Cleaning: Use acetone organic solvent to clean the 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 alumina on the surface of the cemented carbide substrate cleaned in step S1 to form an intermediate layer, thereby obtaining a pretreated substrate; S3, activation: the pretreated substrate treated in step S2 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: placing the prepared activated substrate 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, thereby preparing a copper-plated substrate; S4, post-processing: cleaning and drying the copper-plated substrate obtained after the processing in step S4 to obtain a copper-plated cemented carbide.

[0006] By adopting the above technical scheme, in the present application, the oil and impurities on the surface of the cemented carbide are first removed by washing with an organic solvent, which provides a good foundation for subsequent processing, and then the 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 and the Co element in the cemented carbide substrate have good chemical compatibility, and they are mutually dissolved in the plasma spraying process to form a certain degree of diffusion layer, forming a strong metallurgical bond, achieving chemical bonding, and finally forming a local metallurgical fusion zone between the intermediate layer and the substrate, which significantly improves the bonding strength; The addition of Cr and W in the alloy powder not only ensures the firm bonding between the coating and the substrate during plasma spraying by utilizing their high melting point characteristics, but also the Cr element improves the oxidation resistance and corrosion resistance, the W element enhances the hardness, and the Co element on the surface after spraying can also be used as a reducing agent for palladium salt reduction. The nickel element in the Ni-5Al alloy has similar crystal structure and chemical properties to the Co element, and can form 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, and during the chemical 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 react chemically with copper ions to promote the deposition and bonding of copper. 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 to improve the bonding strength. At the same time, in the present 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 coating. 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 the present application, but will help to improve the corrosion resistance of the coating.

[0007] After the intermediate layer is sprayed, it is first reduced by palladium salt under acidic conditions. The Co remaining on the surface of the intermediate layer after spraying directly acts as a reducing agent during the subsequent palladium salt activation, making Pd 2+ Selectively reduced with Co to form island-shaped Pd 0 Catalytic core, palladium salt activation layer as the catalytic core of chemical copper plating, accelerates the reduction reaction of copper ions, and the formed island catalytic core provides more reaction sites, which is conducive to the uniform deposition of copper ions. The nanosilver colloid ultrasonic treatment makes the nanosilver embedded in the gap of the palladium activation layer. Silver and palladium form a primary battery in the micro area (Ag as anode, Pd as cathode). The formation of a micro-battery effect can accelerate the subsequent reduction process of copper ions and realize chemical copper plating.

[0008] In the present application, the intermediate layer composite powder not only utilizes the nickel element and the 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 mutually to form a continuous solid solution and form a chemical bond, and the plasma spraying technology can form a layer of intermediate layer with roughness on the surface of the cemented carbide substrate. This roughness provides the effect of mechanical anchoring, so that the subsequent copper plating layer can be embedded in the tiny concave and convex of the intermediate layer like a "nail", forming a "pinning" effect, and this mechanical anchoring effect enhances the bonding force between the copper plating layer and the intermediate layer, thereby indirectly improving the overall bonding force 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. Moreover, in the activation step, the nano silver particles and Pd form a micro-region galvanic cell effect, which further accelerates the reduction rate of copper ions, improves the uniformity and compactness of the copper plating layer, and further enhances the bonding force between the coating and the substrate. At the same time, the embedding of the nano silver particles also increases the contact area and bonding force between the coating and the substrate, which is conducive to forming a more solid coating.

[0009] Finally, in the present application, the bonding force 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 layer quality.

[0010] 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 remainder is Co-25Cr-8W alloy powder.

[0011] By adopting the above technical scheme, the Ni-5Al ratio control can realize the chemical bonding between the intermediate layer and the cemented carbide substrate and the copper-plated layer. On this basis, in the present 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 interface bonding force between the intermediate layer and the cemented carbide base layer and the intermediate layer and the copper-plated layer is significantly improved through mechanical bite. In addition, the thermal expansion coefficient of alumina is between that of cemented carbide and copper, which can effectively alleviate the thermal stress of the interface, reduce the risk of coating shedding and corrosion resistance caused by coating cracking, and the chemical properties of alumina are stable, which will not affect the activation process in the subsequent acidic activation of palladium solution, and the intermediate layer has good chemical stability.

[0012] Optionally, in step S2, the thickness of the intermediate layer is 2-5 μm.

[0013] 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 material 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.

[0014] Optionally, in step S2, the plasma spraying uses 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, and the argon flow rate is 30-50 slpm, and the hydrogen flow rate is 3-8 slpm.

[0015] 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.

[0016] By adopting the above technical solution, heat treatment is performed after plasma spraying to eliminate internal stress and improve interface bonding strength.

[0017] 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 pre-treated substrate is activated in the palladium chloride solution, the treatment temperature is 35-40° C., the treatment time is 5-10 min, and then the substrate is washed with water, dried with nitrogen, and then ultrasonically treated in a nanosilver colloid solution.

[0018] 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 5-15min, the ultrasonic power is 100-200W, and after the ultrasonic treatment, it is washed with water and then dried with cold air to obtain an activated substrate.

[0019] By adopting the above technical solution, in the present application, under the condition of acidic palladium chloride, Pd 2+ Through replacement reaction, the silver ions are adsorbed on the surface of the pretreated substrate to form catalytic active sites. The silver ions are embedded in the pores of the intermediate layer by ultrasound. The nanosilver particles and Pd form a micro-region galvanic cell effect, which further accelerates the reduction rate of copper ions and improves the uniformity and density of the copper plating layer, thereby further enhancing the bonding force between the plating layer and the substrate. At the same time, the embedding of nanosilver particles also increases the contact area and bonding force between the plating layer and the substrate, which is conducive to the formation of a more solid plating layer.

[0020] Optionally, 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, 0.05-0.15 g / L thiourea and 0.03-0.08 g / L polyvinyl pyrrolidone.

[0021] By adopting the above technical scheme, in the chemical copper plating solution of the present application, copper sulfate is used as a copper salt, EDTA is used as a complexing 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 complexing 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 copper ions to form a protective layer to prevent copper ions from prematurely agglomerating into large particles, which helps to evenly distribute copper ions in the plating solution, so that copper ions are evenly deposited on the surface of the substrate to form fine and uniform copper grains, reduce defects, and improve 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.

[0022] 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.

[0023] Optionally, in step S4, 1.5-3 g / L of nickel sulfate and 0.1-0.3 g / L of benzodiazepine are also added to the chemical copper plating solution.

[0024] By adopting the above technical solution, when nickel sulfate is also added to the chemical copper plating solution in the present application, on the one hand, nickel ions co-deposit with copper ions during the chemical plating process to form a Cu-Ni alloy transition layer, thereby forming a metallurgical bond with the Ni skeleton of the middle layer; on the other hand, the aluminum oxide particles in the middle layer have a negative charge on the surface under high alkalinity conditions, which can adsorb nickel ions in the plating solution to form a Ni-Al 2 O 3 Active sites improve the bite of the coating and the middle layer, and the addition of nickel forms a Cu-Ni alloy that better matches the thermal expansion coefficient of the middle layer containing Ni-5Al, reduces the interface stress, and improves the bonding strength between the coating and the substrate. Benzodiazol can form a coordination bond with the copper surface, enhance the adhesion of the coating on the middle layer, and improve the bonding strength.

[0025] In summary, this application has the following beneficial effects: 1. The intermediate layer composite powder in this application not only utilizes the nickel element and the elements such as Co in the cemented carbide substrate to diffuse with each other during the plasma spraying process to form a continuous solid solution and chemical bond, but also the plasma spraying technology can form an intermediate layer with roughness on the surface of the cemented carbide substrate. This roughness provides a mechanical anchoring effect, enhances the bonding force between the copper plating layer and the intermediate layer, thereby indirectly improving the overall bonding force 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; 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 during 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 is used as the catalytic core of chemical copper plating, which accelerates 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 is the anode and Pd is the 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. 3. In the present application, when nickel sulfate is added to the chemical copper plating solution, on the one hand, nickel ions co-deposit with copper ions during the chemical plating process to form a Cu-Ni alloy transition layer, thereby forming a metallurgical bond with the Ni skeleton of the middle layer; on the other hand, the aluminum oxide particles in the middle layer have a negative charge on the surface under high alkalinity conditions, which can adsorb nickel ions in the plating solution to form a Ni-Al alloy transition layer. 2 O 3 Active sites improve the bite between the coating and the intermediate layer. Moreover, after adding nickel, the Cu-Ni alloy formed has a better match with the thermal expansion coefficient of the intermediate layer containing Ni-5Al, which reduces the interface stress and improves the bonding strength between the coating and the substrate. DETAILED DESCRIPTION

[0026] The present application is further described in detail below in conjunction with the examples. It is particularly noted that if no specific conditions are specified in the following examples, the experiments 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.

[0027] In the present 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, with 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.

[0028] The nano silver colloidal solution in the following examples was prepared by the following method: 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 prepare 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; 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 solution was reacted 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, the supernatant was removed by centrifugation, the precipitate was collected, and the impurities were removed after washing 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.

[0029] The cemented carbide in the following embodiments is grade K465 (WC-12%Co+TaC).

[0030] Example 1

[0031] A chemical copper plating process for cemented carbide surface, comprising the following methods: S1. Cleaning: Use acetone organic solvent to clean the cemented carbide substrate to remove impurities; S2, intermediate layer treatment: Co-25Cr-8W alloy powder is mixed with Ni-5Al and alumina according to the following mass percentages to obtain a composite powder: 20% Ni-5Al alloy powder, 8% alumina powder (particle size of 800-1200nm) and the remainder Co-25Cr-8W alloy powder; 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 then cooled to room temperature to obtain a pretreated substrate; The supersonic plasma spraying process parameters are as follows: spraying distance is 60 mm, spraying power is 60 kW, spraying thickness is 3 μm, plasma gas is a mixture of argon and hydrogen, and the argon flow rate is 40 slpm and the hydrogen flow rate is 5 slpm; S3, activation: specifically comprising the following steps: 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; S3-2, then activating the pretreated substrate after step S2 in an acidic palladium chloride solution at a temperature of 40° C. for 5 min, then washing with water and drying with nitrogen; S3-3, subjecting the pretreated substrate treated in S3-2 to ultrasonic treatment in a nanosilver colloid solution, wherein the concentration of the nanosilver colloid solution is 0.1 g / L, and the pH value of the nanosilver colloid solution is adjusted to 4.5, the ultrasonic treatment time is 10 min, the treatment temperature is 25° C., the ultrasonic power is 150 W, and after the ultrasonic treatment, the substrate is washed with water and dried with nitrogen to obtain an activated substrate; 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, the copper plating layer has a thickness of 8 μm, and the plating solution temperature is 45° C., to prepare a copper-plated substrate; Among them, the chemical copper plating solution includes the following raw materials: 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; S4, post-processing: cleaning and drying the copper-plated substrate obtained after the processing in step S4 to obtain a copper-plated cemented carbide.

[0032] Example 2

[0033] A chemical copper plating process for cemented carbide surface, comprising the following methods: S1. Cleaning: Use acetone organic solvent to clean the cemented carbide substrate to remove impurities; S2, intermediate layer treatment: Co-25Cr-8W alloy powder is mixed with Ni-5Al and alumina according to the following mass percentages to obtain a composite powder: 10% Ni-5Al alloy powder, 5% alumina powder (particle size of 800-1200nm) and the remainder Co-25Cr-8W alloy powder; 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; The supersonic plasma spraying process parameters are as follows: spraying distance is 50 mm, spraying power is 50 kW, spraying thickness is 2 μm, plasma gas is a mixture of argon and hydrogen, and the argon flow rate is 30 slpm and the hydrogen flow rate is 3 slpm; S3, activation: specifically comprising the following steps: 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; 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; S3-3, subjecting the pretreated substrate treated in S3-2 to ultrasonic treatment in a nanosilver colloid solution, wherein the concentration of the nanosilver colloid solution is 0.1 g / L, and the pH value of the nanosilver colloid solution is adjusted to 4.5, the ultrasonic treatment time is 5 min, the treatment temperature is 20° C., the ultrasonic power is 100 W, and after the ultrasonic treatment, the substrate is washed with water and dried with nitrogen to obtain an activated substrate; 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, the copper plating layer has a thickness of 9 μm, and the plating solution temperature is 40° C., to prepare a copper-plated substrate; Among them, the chemical copper plating solution includes the following raw materials: 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; S4, post-processing: cleaning and drying the copper-plated substrate obtained after the processing in step S4 to obtain a copper-plated cemented carbide.

[0034] Example 3

[0035] A chemical copper plating process for cemented carbide surface, comprising the following methods: S1. Cleaning: Use acetone organic solvent to clean the cemented carbide substrate to remove impurities; S2, intermediate layer treatment: Co-25Cr-8W alloy powder is mixed with Ni-5Al and alumina according to the following mass percentages to obtain a composite powder: 30% Ni-5Al alloy powder, 10% alumina powder (particle size of 800-1200nm) and the remainder Co-25Cr-8W alloy powder; Then, the composite powder is coated on the surface of the cleaned cemented carbide substrate 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; The supersonic plasma spraying process parameters are as follows: spraying distance is 80 mm, spraying power is 80 kW, spraying thickness is 5 μm, plasma gas is a mixture of argon and hydrogen, and the argon flow rate is 50 slpm and the hydrogen flow rate is 8 slpm; S3, activation: specifically comprising the following steps: 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; S3-2, then activating the pretreated substrate after step S2 in an acidic palladium chloride solution at a temperature of 40° C. for 5 min, then washing with water and drying with nitrogen; S3-3, subjecting the pretreated substrate treated in S3-2 to ultrasonic treatment 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., the ultrasonic power is 200 W, and after the ultrasonic treatment, the substrate is washed with water and dried with nitrogen to obtain an activated substrate; 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, the copper plating layer has a thickness of 6 μm, and the plating solution temperature is 50° C., to prepare a copper-plated substrate; Among them, the chemical copper plating solution includes the following raw materials: 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; S4, post-processing: cleaning and drying the copper-plated substrate obtained after the processing in step S4 to obtain a copper-plated cemented carbide.

[0036] Example 4

[0037] 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 also added to the chemical copper plating solution in step S4.

[0038] Example 5

[0039] 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 also added to the chemical copper plating solution in step S4.

[0040] Example 6

[0041] 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 also added to the chemical copper plating solution in step S4.

[0042] Example 7

[0043] 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 also added to the chemical copper plating solution in step S4.

[0044] Example 8

[0045] 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.

[0046] Example 9

[0047] 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.

[0048] Comparative Example 1 A process for chemical copper plating on a cemented carbide surface is carried out according to the method in Example 1, except that step S3-3 is not performed in step S3, and the activated substrate after nitrogen drying after step S3-2 is directly processed in step S4.

[0049] Comparative Example 2 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.

[0050] Comparative Example 3 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.

[0051] Comparative Example 4 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.

[0052] Comparative Example 5 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.

[0053] Performance Testing The cemented carbide was subjected to chemical copper plating according to the process in the above-mentioned embodiments and comparative examples, and the copper-plated cemented carbide obtained in the embodiments and comparative examples of the present application was subjected to a thermal shock test, specifically: heated to 300°C and kept warm for 2 hours, then water-cooled to room temperature, continued to heat to 300°C and then water-cooled, and the coating peeling area was counted after 30 cycles. The statistical results are shown in Table 1 below.

[0054] Table 1:

[0055] 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 benzodiazepine 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 benzodiazepine, the bonding strength is reduced. Combined with the test results of Examples 8 and 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.

[0056] 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, its adhesion was also significantly reduced. Combined with the test results of Comparative Example 2, when no intermediate layer was formed and copper plating was performed directly after activation, its 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 with Comparative Example 2, the improvement was small. When two composites were selected in Comparative Examples 3 and 5, its bonding performance was still weak.

[0057] 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 modifications to the present embodiment without any creative contribution as needed, but such modifications are protected by the patent law as long as they are within the scope of the claims of the present application.

Claims

1. A process for chemical copper plating on a cemented carbide surface, characterized in that: The following steps are involved: S1. Cleaning: Use acetone organic solvent to clean the 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 alumina on the surface of the cemented carbide substrate cleaned in step S1 to form an intermediate layer, thereby obtaining a pretreated substrate; S3, activation: the pretreated substrate treated in step S2 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: placing the prepared activated substrate 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, thereby preparing a copper-plated substrate; S4, post-processing: cleaning and drying the copper-plated substrate obtained after the processing in step S4 to obtain a copper-plated cemented carbide.

2. A process for chemical copper plating on a cemented carbide surface according to claim 1, characterized in that: 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 remainder is Co-25Cr-8W alloy powder.

3. A process for chemical copper plating on a cemented carbide surface according to claim 1, characterized in that: The thickness of the intermediate layer in step S3 is 2-5 μm.

4. A process for chemical copper plating on a cemented carbide surface according to claim 1, characterized in that: 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, and the argon flow rate is 30-50 slpm, and the hydrogen flow rate is 3-8 slpm.

5. A process for chemical copper plating on cemented carbide surface according to claim 1, characterized in that: After the plasma spraying in step S2 is completed, a heat treatment is performed at 800-1000° C. for 1-2 hours, and then the heat treatment is performed at room temperature to proceed to step S3.

6. A process for chemical copper plating on cemented carbide surface according to claim 1, characterized in that: 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., the treatment time is 5-10 min, and then the substrate is washed with water, dried with nitrogen, and then ultrasonically treated in a nanosilver colloid solution.

7. A process for chemical copper plating on a cemented carbide surface according to claim 1, characterized in that: In step S3, the pretreated substrate activated by the acidic palladium chloride solution is treated in a nanosilver colloidal solution at a 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.

8. The process for chemical copper plating on cemented carbide surface according to claim 1, characterized in that: 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 polyvinyl pyrrolidone.

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

10. A process for chemical copper plating on a cemented carbide surface according to claim 8, characterized in that: In step S4, 1.5-3 g / L of nickel sulfate and 0.1-0.3 g / L of benzodiazepine are also added to the chemical copper plating solution.

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