Physical Vapor Deposition, or PVD, is a term used to describe a family of coating processes. The most common of these PVD coating processes are evaporation (typically using cathodic arc or electron beam sources), and sputtering (using magnetic enhanced sources or "magnetrons", cylindrical or hollow cathode sources). All of these processes occur in vacuum at working pressure (typically 10-2 to 10-4 mbar) and generally involve bombardment of the substrate to be coated with energetic positively charged ions during the coating process to promote high density. Additionally, reactive gases such as nitrogen, acetylene or oxygen may be introduced into the vacuum chamber during metal deposition to create various compound coating compositions. The result is a very strong bond between the coating and the tooling substrate and tailored physical, structural and tribological properties of the film.