What Does Thermal Spraying Mean?
Thermal spraying is a group of coating processes in which finely divided metallic or nonmetallic materials are deposited in a molten or semi-molten condition to form a coating. The coating material may be in the form of powder, ceramic rod, wire or molten materials.
Substrate materials include:
- Stainless steel
- Some plastics
Coating materials include:
- Tungsten carbides
- Stainless steels
- Nickel-chrome carbides (chrome oxide, aluminum oxide, zirconia, titania)
Corrosionpedia Explains Thermal Spraying
A basic thermal spray system consists of the following:
- Spray gun: The core device performing the melting and acceleration of the particles to be deposited
- Feeder: For supplying the powder, wire or liquid to the torch
- Media supply: Gases or liquids for the generation of the flame or plasma jet, gases for carrying the powder, etc.
- Robot: for manipulating the torch or the substrates to be coated
- Power supply: often standalone for the torch
- Control console: either integrated or individual for all of the above
Thermal spraying can provide coatings with an approximate thickness range of 20 micrometers to several millimeters depending on the process and feedstock. Coating materials available for thermal spraying include metals, alloys, ceramics, plastics and composites. Coating quality is usually assessed by measuring its porosity, oxide content, macro and micro-hardness, bond strength and surface roughness.
Thermal spraying is a generic term encompassing several coating processes:
- Plasma spraying
- Detonation spraying
- Wire arc spraying
- Flame spraying
- High velocity oxy-fuel coating spraying (HVOF)
- Warm spraying
- Cold spraying
This technique is mostly used to produce coatings on structural materials. Such coatings provide protection against high temperatures, corrosion, erosion and wear. They can also change the appearance, electrical or tribological properties of the surface.