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

A solution to the above problem is a configuration involving the combination of a TiN layer and a gold layer. A very thin layer of gold (about 0.1 micron thick) is deposited with a thicker underlayer of TiN thus combining the advantages of the hardness of TiN with the colour of gold providing longer life guarantee with considerable lower consumption of gold. This configuration is being successfully used in India by several watch companies as Titan (Hosur, Tamil Nadu) and Timex (Noida, U.P.)

Properties of the decorative coatings by PVD
  • Scratch and wear resistant
  • Chemically inert & corrosion resistant
  • Perfect adhesion
  • Deposition on steel, plastic, brass, zinc and aluminium
  • Excellent colour consistency
 
Possible Colours of the coatings by PVD
  • Polished brass : ZrN
  • Gold appearance : TiN
  • Silver grey , steel & chromium : CrN
  • Black & grey : TiAlN
  • Violet : TiCN
  • Aubergine : TiAlN
  • Various other colours possible on request
 

The above coatings have successfully passed the various standard tests recommended for decorative coatings such as:
  1. Porosity test
  2. Salt spray test
  3. Synthetic perspiration test.
CLASSIFICATION OF COATINGS
Broadly classified, there are three types of coatings:

  1. Decorative coatings: These are used for watches, jewellery, bathroom / kitchen door hardware, writing instruments, spectacle frames, cutlery and leatherware accessories.
  2. Tool coatings: These are used for drills, cutters, punches and saw blades as well as used for tools used in bending, rolling, pressing, forming and in the plastic processing industry.
  3. Functional coatings: These are used in applications such as piston rings, connecting rods, fuel injection pumps and gears where high wear and friction are involved.
  4. Special coatings: Very often the customers’ requirements are too highly specific to be met by our standard systems.
TRIBOLOGICAL CHARACTERISTICS OF PVD COATINGS
  • 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.
 
BENEFITS OF PVD COATINGS
For tools:

  1. Low adhesive & abrasive wear
  2. Low coefficient of friction
  3. 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.

For decorative applications:
  • High hardness (coatings are scratch and wear resistant)
  • High corrosion resistance
  • Perfect adhesion
  • Deposition on steel, brass, zinc, aluminium and plastic
  • Excellent colour consistency
  • A wide range of colours can be obtained
  • Reduced gold consumption
  • No environmental pollution or waste disposal.
 

For functional applications:
  • Low adhesive & abrasive wear
  • Low coefficient of friction
- Extended lifetime
- Reduced power consumption
- Higher operational speeds
- Reduced heat generation
- Reduced noise levels
 
Major features of the above systems are:
  • PLC-controlled automatic processing; provides consistency in coating quality
  • Short process cycle
  • Individual shutters for each cathode
  • Thermocouple monitoring & control
  • Rectangular cathodes for high coating uniformity
  • Closed loop cold/hot water distribution unit
  • Large wide opening door which offer easy access to the substrates and targets
  • Substrate table with triple rotational facility; offering high loading capacity with uniformity in coating.
  • Easy maintenance; high system availability
  • Software control, including features like trend analysis, help functions and maintenance information.