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Coating technologies - introduction

Dr. Dmitri Kopeliovich

Coating is a layer of a substance applied to the substrate surface.

Coating is also a process of applying a layer to the substrate surface.

Coating material is different from the substrate material and it permits achieving special surface properties of the part without changing its bulk properties.

Coatings may improve the following surface properties:

TiN, TiAlN, TiCN, NiN coatings for cutting tools.

Hard chrome coating for rolling mill rolls, hydraulic cylinder rods, rollers, piston rings, mold surfaces, thread guides.

Aluminum Hard anodizing.

Metal coating of steel (Zn, Ni, Cr).

Enameling.

Ceramic coating for high temperature oxidation protection.

  • Anti-friction properties (wear resistance, low coefficient of friction, score resistance).

Engine bearings electroplated with Pb-Sn-Cu, or sputter coated with Al-Sn.

Diamond like coatings for tools, dies, valves.

Carbon and MoS2 coatings for camshafts, pistons, cylinder-head studs, conveyor chains.

PTFE (Teflon®) anti-stick coatings for food industry, medical devices, electrical equipment.

  • Cosmetic appearance.

Cr-Ni decorative coatings,

Anodizing

TiN gold-like coatings for jewelry, eye glass frames, watches, pens.

Black oxide coating of bearings, gears, firearms, journals.

The following technologies are used for applying coatings on metals:

  • Electroplating – the process of deposition of metal ions from electrolyte solution onto the cathode part.
  • Electroless plating - the process of deposition of metal ions from electrolyte solution onto the part, when no electric current is involved and the plating is a result of chemical reaction occurring on the part surface.
  • Conversion coating - the process, in which the coating is formed as a result of chemical or electrochemical reaction on the part surface.
  • Hot dipping - immersing the part into a molten metal, followed by removal of the part from the metal bath, which results in formation of the metal coating on the part surface.
  • Physical Vapor Deposition (PVD) - the process involving vaporization of the coating material in vacuum, transportation of the vapor to the substrate and condensation of the vapor on the substrate (part) surface.
  • Chemical Vapor Deposition (CVD) – the process, in which the coating is formed on the hot substrate surface placed in an atmosphere of a mixture of gases, as a result of chemical reaction or decomposition of the gases on the substrate material.
  • Thermal spraying – deposition of the atomized at high temperature metal, delivered to the substrate surface in a high velocity gas stream.

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coating_technologies-introduction.txt · Last modified: 2014/05/03 by dmitri_kopeliovich
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