I'm just making a coating for medical devices. Golden common do TiN (commonly known as titanium plating), also have do CrN or TiAlN, will tell from hardness TiAlN > TiN > CrN, but from a security point of view, TiN is better, CrN is not recommended, think there may be six valence Cr ions, harmful to human body. These treatments are collectively referred to as PVD processing.
