Thermal Spray

Thermal spraying is a variety of coating processes in which melted (or heated) materials are sprayed onto a surface.The surfacing material may be in the form of powder, rod, cord, or wire. Thermal sprayed coatings are extremely effective in increasing component life and value, decreasing machinery down-time, and improving performance in a wide variety of applications.

HVOF (High Velocity Oxygen Fuel)
A mixture of gaseous or liquid fuel and oxygen is fed into a combustion chamber, where they are ignited and combusted continuously. The resultant hot gas emanates through a onverging–diverging nozzle and travels through a straight section. A powder feed stock is injected into the gas stream. The stream of hot gas and powder is directed towards the surface to be coated. The powder partially melts in the stream, and deposits upon the substrate. The resulting coating has low porosity and high bond strength.

Plasma
In plasma spraying process, the material to be deposited, typically as a powder, sometimes as a liquid, suspension, or wire, is introduced into the plasma jet, emanating from a plasma torch. In the jet, where the temperature approaches 10,000 K, the material is melted and propelled towards a substrate. There, the molten droplets flatten, rapidly solidify and form a deposit.

Twin Arc
Wire arc spray is a form of thermal spraying where two consumable metal wires are fed independently into the spray gun. These wires are then charged and an arc is generated between them. The heat from this arc melts the incoming wire, which is then entrained in air jet from the gun. This entrained molten feedstock is then deposited onto a substrate. This process is commonly used for metallic, heavy coatings.

Combustion
The combustion spray process carried out correctly is called a "cold process" (relative to the substrate material being coated) as the substrate temperature can be kept low during processing avoiding damage, metallurgical changes and distortion to the substrate material. Combustion coatings are typically not as well bonded as coatings produced with other processes, but can often be applied in very thick coatings due to their low coating stress.

Spray & Fuse
The spray-and-fuse process is a two-step process in which powdered coating material is deposited by using either a combustion gun or plasma spray gun, and subsequently fused using either a heating torch or a furnace.