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Thermal Spraying Processes

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.

The atmospheric plasma spray process is used for wear and corrosion protection, thermal insulation, repair, restoration and further surface functions. As it is the most flexible of all thermal spray processes, coatings can be applied at high deposition rates onto different metallic substrates by using the widest variety of powder feedstock materials composed of metals, alloys, carbides, ceramics and others. As such, atmospheric plasma spray is often used to apply coatings for thermal protection, wear resistance, corrosion control, dimensional control and restoration and much, much more.

Key benefits of this process
  • Most flexible of all the thermal spray processes, with sufficient energy to melt any material — even materials with high melting points such as ceramics. 
  • Excellent control of coating thickness and surface characteristics such as porosity and hardness 
  • Widely used for high-volume production 
Typical applications
  • Gas turbine components  
  • Textile and printing machinery 
  • Automotive cylinder liners 
  • Medical implants 
Process description

A strong electric arc is generated between a positively charged pole (anode) and a negatively charged pole (cathode). This ionizes the flowing process gasses into the plasma state. The powder feedstock material is injected into the plasma jet, melting the powder particles and propelling them onto the workpiece surface. 

In addition to conventional atmospheric plasma spray guns, Oerlikon Metco has pioneered cascading arc plasma spray guns. Cascading arc spray guns constrain the arc between the anode and cathode, resulting in a more controlled spray plume. In turn, this results in more homogeneous heating of the plasma particles, and significantly increases the possible spray throughput (measured as deposit efficiency times spray rate). The resulting coatings are more reliable and can be applied faster. 

Process basics
  • Heat source: arc 
  • Feedstock: powder (ceramics, metals, alloys, blends, carbides and others) 
  • Plasma temperature: approx. 16 000 °C (28 800 °F) 
  • Particle velocity: up to 450 m/s (1 500 ft/s) 
  • Approximate application rate: 4 to 8 kg/h (9 to 18 lb/h) 

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