Click the links below to read more about diamond-, DLC- and aluminium-rich coating.
Diamond coating is carried out using the CVD method. It is a synthesized coating, which has a hardness and thermal conductivity equal to natural diamond, offers high performance machining of non-ferrous and non-metal materials.
CVD diamond coating is a relatively new process. It is carried out by activating a number of gases such as methane, hydrocarbon and alcohol and then precipitates on to the surface of the tool as a coating. Looking at the image below, the gases mentioned are usually mixed with hydrogen and fed into the apparatus. The gas is activated by either microwave, thermal filament* or other methods and then broken down into electrons and ions by a plasma electro-discharge*.
DLC (Diamond Like Carbon) is an amorphous hard carbon film and has similar qualities to graphite and diamond, both of which are constituted from the same carbon atoms.
DLC coating generally has a low friction coefficient with non-ferrous metals and is used for non-ferrous and non-metal machining such as aluminium alloys.
The mainstream coating material of solid carbide drills and end mills is (Al,Ti)N. It is a material manufactured by replacing the Ti in TiN crystals with smaller atomic radii Al. This replacement causes strain in the crystal structure, heightening the hardness and oxidation temperature resistance. As shown in the figure on the right hand side, hardness increases with up to approximately 60mol% AlN, while over 70mol% AlN, altered crystal structures appear and the hardness becomes lower. Coatings containing Al like this are called aluminium-rich coatings.
To use the properties of aluminium-rich coatings effectively in order to improve cutting performance, it is necessary to ensure meticulous cleaning of the tools prior to coating and ensure that the coating procedure itself is rigidly adhered to and controlled for quality.