Manufacturing: Surface Finishing

Low Temperature Arc Vapor Deposition (LTAVD)

Recent developments in PVD, (Physical Vapor Deposition), now let vapor-deposited coatings go on at low temperatures. The technique, known as low-temperature arc-vapor deposition (LTAVD), can now apply both refractory metals and conventional metal coatings at near ambient temperatures. Parts to be coated go in a chamber and revolve around a cathode that is the metallic source of the coating (often zirconium). A vacuum is drawn on the chamber and a low-voltage arc is established on the metallic source. The arc evaporates the metal from the source temperatures rarely above 100°C.

The chamber gets charged with a mixture of common inert and reactive gasses, such as argon and nitrogen, and an arc-generated plasma surrounds the source. Arc-evaporated metal atoms and reactive-gas molecules ionize in the plasma and accelerate away from the source. Arc-generated plasmas are unique in that they generate a flux of atoms and molecules that have high energies and are mostly (>95%) ionized. The high energy causes hard and adherent coatings to form on parts mounted to fixtures that rotate around the source. A bias power supply can be used to apply a negative charge to the parts which further boosts the energy of the condensing atoms.