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Thermal spraying techniques are coating processes in which melted (or heated) materials are sprayed onto a surface. The "feedstock" (coating precursor) is heated by electrical (plasma or arc) or chemical means (combustion flame). Thermal spraying can provide thick coatings (approx. thickness range is 20 micrometers to several mm, depending on the process and feedstock), over a large area at high deposition rate as compared to other coating processes such as electroplating, physical and chemical vapor deposition. Coating materials available for thermal spraying include metals, alloys, ceramics, plastics and composites. They are fed in powder or wire form, heated to a molten or semimolten state and accelerated towards substrates in the form of micrometer-size particles. Combustion or electrical arc discharge is usually used as the source of energy for thermal spraying. Resulting coatings are made by the accumulation of numerous sprayed particles. The surface may not heat up significantly, allowing the coating of flammable substances. Coating quality is usually assessed by measuring its porosity, oxide content, macro and micro-hardness, bond strength and surface roughness. Generally, the coating quality increases with increasing particle velocities. Several variations of thermal spraying are distinguished: *Plasma spraying *Detonation spraying *Wire arc spraying *Flame spraying *High velocity oxy-fuel coating spraying (HVOF) *Warm spraying *Cold spraying In classical (developed between 1910 and 1920) but still widely used processes such as flame spraying and wire arc spraying, the particle velocities are generally low (< 150 m/s), and raw materials must be molten to be deposited. Plasma spraying, developed in the 1970s, uses a high-temperature plasma jet generated by arc discharge with typical temperatures >15000 K, which makes it possible to spray refractory materials such as oxides, molybdenum, etc.〔 ==System overview== A typical thermal spray system consists of the following: *Spray torch (or 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 through tubes. *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(s) - either integrated or individual for all of the above 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Thermal spraying」の詳細全文を読む スポンサード リンク
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