Copper Plating on Tungsten Carbide Cutting Tools (2/2)

However, inside tungsten carbide usually contain some grease, which is not easily to be cleaned. And in the process of electro-deposition pretreatment, it will penetrate into plating solution, which resulting in the coating pan-point corrosion from the inside out, so that the final coating falls off. Compared with copper plating on other materials, tungsten carbide has higher requirements on degreasing. Commonly used methods of electrolytic degreasing, heat degreasing and organic solvent degreasing, and the heat degreasing is the best choice for tungsten carbide. It should be polished after degreasing, and remove the oxide layer on the surface and then wash by ionized water ultrasonic.

In pre-plating process, we use cyanide copper, and electroplating of copper sulfate usually used as the plating solution, the temperature controlled at about 20 ℃, air agitation, anode copper (copper) plating time is about 5-10min. Finally, we make a comprehensive assessment of coating from the appearance, the hardness and the bonding strength. From the appearance of the copper layer surface is smoother and surface roughness of less than 0.3μm. Compared with the coating without pretreatment or high-temperature degreasing, it has higher density and there is no peeling, cracking or shedding. The hardness of Cu plating layer on tungsten carbide can reach 216-219HV. Bonding strength test method can be divided into two types, one is heating, which heat the plated workpiece to 300℃ and hold 1h, quickly removed and placed in water at room temperature to observe whether the coating peeled or shed; the other is scribing, was 30 ° with the edge of the cutting carbide layer again designated as the side length of 1mm squares, and observation of the coating peeling off phenomenon.

In addition, the carbide deposition process for copper plating is a mechanical process of accumulation, due to copper and tungsten carbide WC and Co in the substantial absence of mutual penetration and dissolution, is a combination of mechanical way. After coating the hydrogen plasma treatment, the elements Cu and carbide matrix was dissolved in each other at the joint surface, diffusion, thereby forming an interface diffusion layer. The existence of this diffusion layer will make the combination of copper layer and cemented carbide substrate metallurgical bonded to shift from mechanical binding, thus combining the strength of the copper layer and the cemented carbide substrate has been significantly improved.

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