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Thermal spraying is a cost-effective method for applying coatings that enhance surface properties. In the simplest terms, thermal spray involves heating a feedstock material, generally in powder or wire form, to a molten or semi-molten state. The feedstock is propelled using a stream of gas or compressed air to deposit it, creating a surface structure on a given substrate.

The coating feedstock material may consist of a single metallic element, but more often it is an alloy, composite, ceramic, carbide or blend that will give rise to a surface having physical properties that are only achievable through the thermal spray process. Thermal spray is a family of processes, with each member of the process family providing unique opportunities for engineered surfaces.

Oerlikon Metco actively supports all common thermal spray methods, with options to suit your surfacing and applications requirements — such as the size of your production run, geometry of your part, environmental concerns and portability. Through thermal spray, Oerlikon Metco has developed and marketed application technologies to apply coatings that solve our customers’ toughest surface challenges since 1933.

Electric arc wire spray offers excellent portability and flexibility for on-site coating work; however, it is popular for in-shop work, as well. It is often used for applications such as coating welded tube seams, piston rings, capacitors, varistors, boiler walls, and large infrastructures. It only requires electricity and compressed air to melt metallic alloys and pure metal wires and allows very high spray and application rates.

Key benefits of this process
  • Low equipment investment costs 
  • Excellent portability/flexibility for on-site coating jobs 
  • Only requires compressed air, no other process gas or cooling media 
  • Very High spray and application rates
Typical applications
  • Bridge decks 
  • Transport pipes 
  • Capacitors / varistors 
  • Welded tube seams 
  • Boiler walls 
  • Other large infrastructures 
  • Bond coats for other thermal spray coatings
Process description

Two metallic wires are needed for the coating feedstock. The two wires are electrically charged with opposing polarity and are fed into the arc gun at matched, controlled speeds. The tips of the two wires contact each other as they exit the spray gun. The opposing charges on the wires create enough heat to continuously melt the tips of the wires, whereby compressed air is used to atomize the now molten material and accelerate it onto the workpiece surface to form the coating.

Process basics
  • Heat source: arc
  • Feedstock: solid or composite metallic wires
  • Arc temperature: approx. 4 000 °C (7 200 °F)
  • Particle velocity: approx. 150 m/s (500 ft/s)
  • Approximate application rate: 15 to 3,300 g/min 2 to 440 lb/h)

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