Powder Flame-Spray Gun
The diagram illustrates a typical powder flame-spray gun. Nozzles are used to generate the flame,
introduce the spray material, and shape the spray pattern. In conventional flame-spray guns,
oxygen and fuel mix inside the nozzle, exiting the nozzle through a set of holes in the face of the
nozzle.
Combustion occurs at the nozzle exit, and combustion gases are free to expand. Feedstock
material is introduced axially through the nozzle into the combustion zone. In some powder-fed gun
designs, a constricting flow of air is fed through a concentric set of holes near the nozzle exit. The
concentric holes are used to pinch the expanding gases, generating a higher-temperature
combustion zone and accelerating the molten powder.
Coaxial air caps located over the end of the nozzle are added to wire- and rod-fed guns to produce
a concentrated air jet to atomize the molten wire or rod at the tip. The air cap confines and
accelerates the molten spray material. As with powder, wires and rods are fed through the center of
the nozzle into the combustion zone. Ceramic and metal rods and wires can be used as coating
feedstock.
Volume 5A, Thermal Spray Technology -> Thermal Spray Processes and Coatings -> Thermal
Spray Processes -> Process Characteristics