Thermal spraying techniques are coating methods that include spraying melted (or heated) materials onto a surface. Electrical (plasma or arc) or chemical techniques are used to heat the "feedstock" (coating precursor) (combustion flame).
When compared to other coating methods such as electroplating, physical and chemical vapour deposition, thermal spraying may create thick coatings (approximate thickness range is 20 microns to several millimetres, depending on the procedure and feedstock) over a large area at a high deposition rate. Metals, alloys, ceramics, polymers, and composites are among the coating materials accessible for thermal spraying. They are fed as powder or wire, heated to a molten or semimolten state, and accelerated as micrometer-sized particles towards substrates. The source of energy for thermal spraying is typically combustion or electrical arc discharge. Resulting coatings are made by the accumulation of numerous sprayed particles. The surface may not heat up significantly, allowing the coating of flammable substances.
The mechanical bond between a thermal spraying coating and the substrate is stronger than metallurgical or fused bonds. Adhesion to the substrate is determined by the quality of the substrate surface, which must be cleaned and roughened prior to spraying with grit blasting or machining
Thermal spraying methods have been widely employed for component preservation and reclamation for many years across all main engineering industry areas. Recent equipment and process innovations have enhanced the quality of thermally sprayed coatings and broadened their possible application range.
What are the Benefits of Thermal Spraying?
- Comprehensive choice of coating materials: metals, alloys, ceramics, cermets, carbides, polymers and plastics
- Thick coatings can be applied at high deposition rates
- Thermal spray coatings are mechanically bonded to the substrate - can often spray coating materials which are metallurgically incompatible with the substrate
- Can spray coating materials with a higher melting point than the substrate
- Most parts can be sprayed with little or no preheat or postheat treatment, and component distortion is minimal
Thermal spray coatings are extensively used in the manufacturing of gas turbines, diesel engines, bearings, journals, pumps, compressors and oil field equipment, as well as coating medical implants.
Thermal spraying is principally an alternative to arc welded coatings, although it is also used as an alternative to other surfacing processes, such as electroplating, physical and chemical vapour deposition and ion implantation for engineering applications.
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