PVD Coating

J. J Castings gives you the best PVD Coating experience in Great Britain

PVD coating processes differ by the way in which the metal is evaporated. We use the Arc process in which each source consists of a block of metal on which we strike an electric arc. The arc gives such intense heat that the surface of the metal block is vapourised to give a charged cloud or plasma of metallic ions. The choice of metal can be Titanium, Titanium/Aluminium mixes or Chromium and this controls the vapour composition. Multiple sources or evaporators mounted in the chamber walls give all-over coverage and by choosing different metals for each evaporator, multi-layered and alloyed coatings can be made.

To apply a PVD coating the items are meticulously cleaned, inspected and loaded  into a vacuum chamber on suitable jigging. When all the air has been pumped out the parts are warmed up to coating temperature by a combination of radiant heating and by bombardment by metal ions. A high DC voltage applied to the items attracts the metal  ions which impinge with sufficient energy to clean the surface and build up to an adhesion layer. Once at coating temperature the metal continues to be evaporated into the chamber and a small controlled amount of pure nitrogen is bled in. The metal  ions reacts with the Nitrogen to form the hard nitride coating.

The coating is very thin, between 2 and 10 microns depending upon application, so has negligible effect on dimensions. The coating replicates the original surface finish. Areas can be masked off  by mechanical shields where geometry allows.

Arc evaporation gives the best Ionisation Rate of any PVD process which ensures excellent coating adhesion and structure. The throwing power is good so the most complex shapes can be coated.

It can accommodate thousands of small parts or larger parts up to 1200mm long and 800mm across.

Good surface support for thin, hard coatings is always recommended so the quality and hardness of the item to be coated is important. Suitable surfaces include ground, machined, polished and plated. Other finishes can be coated after special pre-cleaning such as plasma nitride items.

PVD coating is carried out at low temperature between 200°C and 500°C. The temperature is selected to suit the material being coated, to retain the temper condition and prevent distortion.

Choice of Coating

Titanium Nitride (TiN)

Hardness: 2500HV
Colour: Gold
Typical Uses: Tools / Plastic Moulds / Medical Implants / Electronics / Decoration

Chromium Nitride (CrN)

Hardness: 2000HV
Colour: Silver
Typical Uses: Tools for Non-ferrous Use / Forming Tools for Steel / Anti-Corrosion / High Temperature Use / Die-casting

Titanium Aluminium Nitride (TiAlN)

Hardness: 3000HV
Colour: Blue/Black
Typical Use: High-Rate Tools / Interrupted Cutting / High Temperature Use / Decoration