Technology
 

Thermal spraying is a technique where a metal, alloy or cermet, in wire- or powder form, is being melted and transferred with high velocity to the surface of the substrate where it forms a protective coating. Coatings can be adjusted to the specific conditions of industry. Thermal spraying is with one exception a "cold" process. This means that in spite of the heat source the substrate will not suffer from deformation.

The structure of a "cold" sprayed layer is lamellar, it somewhat looks like cast iron. In some sprayed metal layers are micro pores and oxide inclusions the cause of a low friction coefficient and a high hardness. A benefit of a micro porous layer is that they will take up oil which gives them excellent wear resistant (metal/metal) properties. Cold sprayed layers have a high resistance against pressure and a lower tensile strength than the base material. This makes them not suitable for a high impacts. Because of their structure, thermally sprayed coatings show an excellent resistance against all forms of wear like: corrosion, heat-oxidation, adhesive wear, abrasive wear, fatigue, cavitation, erosion, etc...

Thermal spraying has one group of materials which are known as self fluxing cermets or hard metals. The coating will be additionally treated by a heat source the part will be heated to approximately 1050 - 1150 °C. The structure of these fused coatings is homogen which will increase the mechanical strength. This makes the typical coating suitable for high impacts, chemical corrosion, heat oxidation, etc. Coatings of this type contain the base material Nickel, Chromium or Cobalt and, if necessary, wolfram carbides. These fused coatings can reach a hardness from Rc30 to Rc75.

Thermal spraying shows the following techniques :

     Atmospheric Plasma Spraying
      Combustion Wire Spraying
      Combustion Powder Spraying
     Arc Wire Spraying
      HVOF

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