Electroplated diamond tools involve many processes in the manufacturing process, any process is not sufficient, will cause the coating to fall off.
Effect of the pre-plating treatment
The treatment process of the steel matrix before entering the plating tank is called the pre-plating treatment. Pre-plating treatment includes: mechanical polishing, oil removal, erosion and activation steps. The purpose of pre-plating treatment is to remove the burr, oil, oxide film, rust and oxidation skin on the surface of the matrix, so as to expose the matrix metal to grow the metal lattice normally and form the intermolecular binding force.
If the pre-plating treatment is not good, the surface of the matrix has a very thin oil film and oxide film, the metal character of the matrix metal can not be fully exposed, which will hinder the formation of the coating metal and the matrix metal, which is only a mechanical inlay, the binding force is poor. Therefore, poor pretreatment before plating is the main cause of coating shedding.
The effect of the plating
The formula of the plating solution directly affects the type, hardness and wear resistance of the coating metal. With different process parameters, the thickness, density and the stress of the coating metal crystallization can also be controlled.
For the production of diamond electroplating tools, most people use nickel or nickel-cobalt alloy. Without the influence of plating impurities, the factors affecting the coating shedding are:
(1) The influence of internal stress The internal stress of the coating is produced in the process of electrodeposition, and the additives in the dissolved wave and their decomposition products and hydroxide will increase the internal stress.
Macroscopic stress can cause bubbles, cracking and falling off of the coating in the process of storage and use.
For nickel plating or nickel-cobalt alloy, the internal stress is very different, the higher the chloride content, the greater the internal stress. For the main salt of nickel sulfate coating solution, the internal stress of watt coating solution is less than that of other coatings solution. By adding organic luminent or stress eliminating agent, the macro internal stress of the coating can be significantly reduced and the microscopic internal stress can be increased.
(2)The effect of hydrogen evolution in any plating solution, regardless of its PH value, there is always a certain amount of hydrogen ions due to the dissociation of water molecules. Therefore, under appropriate conditions, regardless of plating in an acidic, neutral, or alkaline electrolyte, there is often hydrogen precipitation in the cathode along with the metal precipitation. After hydrogen ions reduce at the cathode, part of the hydrogen escapes, and part seeps into the matrix metal and coating in the state of atomic hydrogen. It distort the lattice, causing great internal stress, and also makes the coating significantly deformed.
Effects of the plating process
If the composition of the electroplating solution and other process control effects are excluded, the power failure in the electroplating process is an important cause of the coating loss. The electroplating production process of electroplating diamond tools is very different from other types of electroplating. The plating process of electroplating diamond tools includes empty plating (base), sand coating and thickening process. In each process, there is the possibility of the matrix leaving the plating solution, that is, a long or short power outage. Therefore, the use of more reasonable process, process can also reduce the emergence of coating shedding phenomenon.
The article was reprinted from "China Superhard Materials Network"
Post time: Mar-14-2025
