Thermal Spray techniques are coating processes which involve spraying melted (or heated) materials onto a surface. As such thermal spraying is a line-of-sight process. The energy to heat the feedstock (coating precursor) is supplied by electrical (plasma or arc) or chemical means (combustion flame). Coating thicknesses range between approximately 20 micrometers (μm) and several millimetres (mm) depending on the process and feedstock. A coating is a covering that is applied to an object to protect it or change its appearance. ... A feedstock is a petrochemical used as a raw material to be fed into a machine or processing plant. ...

The materials to be deposited as the coating are typically fed into the spray gun in powder or wire form where they may be atomized before being accelerated towards the substrate, or material to be coated^[1]. "As the sprayed particles impinge upon the surface, they cool and build up, splat by splat, into a laminar structure forming the thermal spray coating."^[2] Atomization (British English: atomisation) is conversion of bulk liquid into a spray or mist (i. ... Substrate is a term used in materials science to describe the base material on which processing is conducted to produce new film or layers of material such as deposited coatings. ...

Coating quality is usually assessed by measuring its porosity, oxide content, macro and microhardness, bond strength and surface roughness. Generally, the coating quality increases with increasing particle velocities. Porosity is a measure of the void spaces in a material, and is measured as a fraction, between 0–1, or as a percentage between 0–100%. The term porosity is used in multiple fields including manufacturing, earth sciences and construction. ... In materials science, hardness is the characteristic of a solid material expressing its resistance to permanent deformation. ... In chemistry, bond strength is measured between two atoms joined in a chemical bond. ... It has been suggested that Rugosity be merged into this article or section. ...

Spray coatings may either be applied manually or by machine, depending on complexity, cost, and environmental^[3] and safety concerns. OSHA logo The United States Occupational Safety and Health Administration (OSHA) is an agency of the United States Department of Labor. ...

Some common reasons for spray coating are:^[4]

• corrosion protection
• fouling protection
• increase conductivity
• increase surface hardness to reduce wear
• to repair damaged surfaces - rebuild
• high temperature protection (thermal barrier coatings)
• medical implants

Some common types of thermal spray are: For the hazard, see corrosive. ... The term fouling refers to the fouling of heat-transferring system components through ingredients contained in the cooling water. ... Electrical conductivity is a measure of how well a material accommodates the transport of electric charge. ... Look up hardness in Wiktionary, the free dictionary. ...

• Flame Spraying (with powder and wires)

• High Velocity Oxygen-Fuel (HVOF)
• Detonation gun (D-Gun)

• Arc Spraying with wires
• Plasma Spraying with powders under atmospheric and vacuum or low pressure conditions

• DC-arc plasma spray
• RF induction plasma spray
• Wire-arc spray
• Plasma transferred arc spray

High Velocity Oxygen Fuel (HVOF) is a technique to deposit thin films on a material, and can be used to deposit layers as thick as 12mm (1/2). Among others, it is used to deposit a wear and corrosion resistant ceramic coating on a light weight material. ... Plasma spraying, one of the thermal spraying family, is a materials processing technique for producing coatings and free-standing parts using a plasma jet. ...

References

1. ^ Sulzer Metco website describing the processes and applications[1]
2. ^ Army manual describing spray coating - http://www.usace.army.mil/usace-docs/eng-manuals/em1110-2-3401/c-2.pdf - Accessed 20 June 2006.
3. ^ Article discusses briefly several environmental concerns and provides links at the bottom to industrial pollution papers - [2] - Accessed 20 June 2006.
4. ^ Army manual

External links

• www.tspc.ru/en/, company providing Thermal spray coatings and equipment in Russia