Electroplated diamond tools refer to a type of diamond tool made by metal electrodeposition, in which diamond is firmly wrapped by matrix metal on a substrate (steel or other materials). It is widely used in mechanical electronics, glass, building materials, oil drilling and other industries. With the development of the economy and the advancement of science and technology, the requirements of different industries for electroplated diamond tools are basically the same, that is, high efficiency, long life and high grinding precision. To ensure these characteristics, the coating metal must not only have high hardness and wear resistance, but also be evenly distributed in all parts of the substrate to prevent the coating from shedding and shortening the tool life. In some special industries, such as the strong grinding of the magnetic material industry, the feed rate is controlled at about 0.3mm; the dry grinding with large feed rate in the ceramic industry, etc., has particularly demanding requirements on the bonding force between the coating metal and the steel substrate. In the production process of electroplated diamond tools, most manufacturers only pay attention to the type, hardness and wear resistance of the coating metal, but often ignore the bonding strength between the coating metal and the substrate. In actual use, the phenomenon of coating shedding is common. This article analyzes the causes of this problem and briefly discusses the solution.
Types of coating shedding
During the use of electroplated diamond tools, due to the use conditions such as grinding force, temperature rise, and impact of the workpiece, the metal coating containing diamonds will separate from the steel substrate. This is coating shedding. Coating shedding is generally partial shedding, and the phenomenon of complete peeling of the coating is rare. In actual use, there are roughly three situations of coating shedding:
(1) The coating falls off to the surface of the substrate: that is, the metal coating containing diamonds and the metal bottom coating without diamonds are separated from the steel substrate at the same time.
(2) Layer shedding to the metal base coating: that is, the metal base coating without diamonds is not separated from the steel substrate, but the metal coating containing diamonds is peeled off from the metal base coating.
(3) Layer separation of the coating metal in the diamond-containing metal coating: During the use of the diamond-containing metal coating, the coating metal in the part in contact with the workpiece is not normally worn, but abnormally falls off in flakes or powder. The diamonds are not completely shed, but partially granular. This phenomenon is not easy to attract attention, and the consequence is a shorter product life, which often gives people the illusion that the coating has poor holding power or wear resistance. Excluding factors such as scorching of the coating during thickening and poor wear resistance of the coating, when the tool is in normal use, the shedding of diamond particles is intuitively manifested as continuous large holes on the surface of the tool, which should be the shedding of this type of coating.
Causes of coating shedding
The manufacturing process of electroplated diamond tools involves multiple processes. If any process is not carried out sufficiently, the coating will fall off.
Effect of pre-plating treatment
The treatment process of the steel substrate before entering the electroplating tank is called pre-plating treatment. Pre-plating treatment includes mechanical polishing, degreasing, etching and activation. The purpose of pre-plating treatment is to remove burrs, oil stains, oxide films, rust and oxide scale on the surface of the substrate to expose the substrate metal so that the metal lattice grows normally and forms intermolecular bonding. If the pre-plating treatment is not good, there will be a thin oil film and oxide film on the surface of the substrate, and the metal lattice of the substrate metal cannot be fully exposed, which will hinder the formation of intermolecular bonding between the plated metal and the substrate metal. It is only a mechanical embedding effect with poor bonding. Therefore, poor pre-plating treatment is the main cause of coating shedding.
