The high velocity flame spraying process involves continuous combustion of a gas under high pressure in a combustion chamber. The powdered coating material is fed in at the central axis of the chamber and the expansion nozzle that is usually located down-stream of the chamber. The desired high flow velocity in the gas jet is due to this high pressure.
Particles of the coating material are accelerated to high velocities in this way, leading to enormously dense spray coatings with outstanding adhesion. Because the temperature rise is adequate but moderate, the coating material undergoes only slight metallurgical changes as a result of the spraying process. Extremely thin coatings with dimensional accuracy are made by this process.
