PVD

PVD is formation of a thin layer on the surface of substrate in the vacuum environment with vapor transition phase. So it's called PHYSICAL VAPOUR DEPOSITION.
Most common hard coatings in this field are:
TiN , AlTiN , DLC , CrN , TiCN , ZrN

GENERAL PROPERTIES
•    High Hardness
•    Wear Resistance
•    Reduce of Friction Coefficient
•    Resistance to Corrosion
•    Resistance to Oxidation in high temperature
•    Good adhesion
•    Stable and compatible in various environment
•    Inert and Non-toxic
•    Thin Thickness and holding shape and sharp edges

* Most  common coatings is TiN with gold color.
* AlTiN has the best resistance to oxidation in high temperature.
* DLC has a lowest Friction Coefficient.