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What is Thermal Spray ?

Thermal Spray is a group of coating processes in which metallic, ceramic, cermet, and some polymeric materials in the form of wire, powder, or rod are fed to a gun which results in heating to near or somewhat above their melting point. The resulting molten or nearly molten droplets of material are then accelerated in a gas stream and projected against the surface to be coated. When the hot energetic particles impact the surface of the part being coated, they rapidly solidify. As subsequent particles impact the surface, a deposit thickness is built up. The droplets flow into thin lamellar particles adhering to the surface, overlapping and interlocking as they solidify. The total coating thickness is usually generated in multiple passes of the coating device. Thermal spray devices used to accomplish this work are commonly called as guns or torches.

Advantages of Thermal Spray

Versatility: One of the primary advantages of thermal spray technology is its versatility in terms of material selection. Virtually any material that can be melted without decomposing can be used for coating applications, allowing for a wide range of coating compositions and properties.

Low Heat Input: Unlike traditional coating methods such as welding or brazing, thermal spray processes typically do not significantly heat the substrate. This allows for the application of coatings onto heat-sensitive materials or fully heat-treated components without compromising their properties or dimensional integrity.

Repairability: Thermal spray coatings can often be stripped and recoated without altering the properties or dimensions of the underlying substrate. This makes it an ideal choice for repairing worn or damaged coatings, extending the service life of components and minimizing downtime.

Selection of the appropriate thermal spray method is typically determined by:

  • Desired coating material
  • Coating performance requirements
  • Economics
  • Part size and portability

    • The Process Basics

    All methods of thermal spraying involves the projection of small molten particles onto a prepared surface where they adhere and form a continuous coating. To create the molten particles, a heat source, a spray material and an atomisation/projection method are required. Upon contact, the particles flatten onto the surface, freeze and mechanically bond, firstly onto the roughened substrate and then onto each other as the coating thickness is increased.

    The metal spray equipment falls into four main categories, Powder Flame Spray, Combustion Wire Flame Spray, Twin Wire Arc Spray, High Velocity Oxygen Fuel (HVOF) and Plasma Spray.

    Please view the individual process pages to read more about each process.