1. The PVD coating is a process to create a thin layer of metal on a base metal surface. The base metal is called the "substrate," and the newly-coated layer is called the "layer."

2. The PVD coating process can be divided into two main categories: chemical vapor deposition (CVD) and physical vapor deposition (PVD).

3. Chemical vapor deposition (CVD) involves exposing a material to gaseous precursors of its own chemical composition, which are then converted into the desired product by heating the gas in an electric arc or other high-temperature environment. In this case, the precursor materials are typically gases that contain atoms from which layers can be built up on the substrate's surface.

4. Physical vapor deposition (PVD), by contrast, requires no chemical reaction; instead, it relies on physical processes such as evaporation or sputtering to build up layers on a substrate's surface through heat caused by electric discharges in vacuum chambers or other high-temperature environments