What and Why PVD?

Until recently, electroplating of gold (more popularly called as wetplating of gold) was the usual way of obtaining a thin layer of gold for decorative applications such as artificial jewellery, watch cases and straps, spectacle frames etc. The disadvantage of the above process is that gold being extremely soft, gets rapidly eroded; and the process is very expensive due to the high costs of gold as a large thickness is required for a minimum guaranteed lifetime. It is also very difficult to electroplate stainless steel with gold.

PVD offers a wonderful solution to this problem by combining TiN (Titanium Nitride) layer with gold layer. Hardness of TiN base layer gives durability and high lifetime while thin top gold layer maintains the decorative value. Colour of TiN layer is also very similar to gold layer.

Hardness: Ranging from 2000 to 3000 HV, more than twice the hardness of hard chromium. This is generated by the intercrystalline compressive stress and hence it provides a high resistance against abrasive wear caused by dust, metal particles, chips and fillers as used in plastics.

Friction Coefficient: The friction between steel and steel is reduced by half when a layer such as TiN is applied onto one of the surfaces. This is due to the highly homogenous and dense crystalline structure.

Surface / Chemical Affinity: As a result of the small inter-atomic inter-crystalline distance, the interaction of PVD coatings with substrate materials is extremely low, and as such avoids fretting (cold welding).

Chemical Resistance: PVD coatings are resistant against most chemical and environmental influences. This provides protection against corrosive wear or deterioration.

Thermal Behavior: PVD coatings can withstand thermal shocks very well. The temperatures may rise from 400°C to 800°C under permanent operational conditions.

For tools:

Low adhesive & abrasive wear Low coefficient of friction Heat resistivity

- Extended lifetime of the tool - Improved surface quality of workpiece - Low heat generation - Higher operational speeds - Less heat transfer to tool substrate

The above factors lead to reduced operation cycle times, less rejects and a longer uninterrupted machine operation providing a large increase in productivity. Additional advantages are a lower tool consumption and lesser resharpening.