Ion plating is a technique by which coatings of a substance, usually a metal or a compound, are deposited upon a target part or surface. The coating material is vaporized and ionized by an electric arc, then propelled at high speed towards the target, where the electrical charge of the ionized particles causes them to bond to the surface of the target. This technique is sometimes called physical vapor deposition. It is usually done in a vacuum chamber or in an atmosphere of inert gas.
Materials to undergo ion plating are first treated to remove any foreign material and to clean all surfaces. This is done in the same environment in which the plating is to be performed and is called sputtering. The process of sputtering is similar to the plating process that follows, but the target is bombarded with ions of another material, such as argon gas, which strips the surface of all foreign matter, instead of bonding to the target. The surface must be perfectly clean to ensure proper bonding of the coating material.
Once the target is treated and prepared for coating, the ion plating process begins. The coating material is vaporized using an electric arc current that utilizes a very low voltage with high current flow. This not only vaporizes the coating material, it ionizes the individual atoms which repel each other due to their identical electrical charges. This vapor is then propelled at the target, which is given a weak opposing electrical charge to attract the ionized coating material. This causes the vaporized ions of the coating to bond to the prepared surface.
The basic technique for ion plating can be modified in a number of ways. By introducing certain gases and other vaporized ions into the closed environment, it is possible to to combine the vaporized ions of one material with other ions to create a new compound that then bonds to the target. Combining different types of materials allows for a wide variety of coatings.
Coatings applied by ion plating techniques are often very thin and very even. These coatings can have thicknesses on the order of microns. The ability to apply such thin coatings evenly makes this technique good for parts with irregular shapes as well as for applying coatings that cannot be applied by other techniques, such as electroplating.
