During Thermal Spraying, melted coating materials are "sprayed" onto the substrate. The use of plasma is Salvo Coatings' method of choice, but the coating can be melted using chemical means as well. This method, as with powder coating, is ideal for thicker coatings. A 3-5mm thick coating is routine and the use of metals, alloys and plastics is common. Another benefit is the low temperature of the substrate during the process. This allows materials that are either flammable or have low melting points themselves to be coated.
Cold spraying or gas dynamic spraying of thermal sprayed coatings is also possible. In this process a pressure gradient is used to accelerate material with enough force to bond to the substrate. This process is used only in extreme cases as the acceleration needed usually creates extreme process parameters. For example, it has been reported that nitrogen gas needs to be heated to over 1000°C to create stronger bonds.
Warm spraying is basically the intermediate step between cold spraying and hot spraying with high velocity oxy fuel spraying. The temperature is reduced by increasing the nitrogen content in the combustion gas. This process is typically used for coating plastics and some glasses which cannot withstand higher process temperatures.
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