AcuKote HVAF Process Schematics

The principle schematic of the AcuKote HVAF gun is presented in the Figure below:

Compressed air enters the gun as a cooling medium. Then, the air flows into a mixing chamber, where it is mixed with gaseous fuel. The mixture flows into a combustion chamber through multiple orifices of its catalytic ceramic wall. In the combustion chamber, the mixture is ignited by a spark plug, starting combustion. Within a second, the catalytic ceramic wall is heated above the auto-ignition temperature of the mixture, constantly activating its further ignition and combustion during the whole job cycle. Combusted gases flow into an accelerating nozzle, where their speed reaches sonic velocity. Exhausting gaseous jet has a supersonic speed.

Spray powder is fed axially into the combustion chamber, where it is heated. Then, the powder flows into the accelerating nozzle, where it is accelerated almost to the gas velocity. Leaving the nozzle with exhaust gases, the powder jet is directed to the substrate, forming a coating.

The spray powder's temperature is controlled by combustion process parameters, as well as by small additions of a high-enthalpy and high thermal conductivity secondary fuel, such as hydrogen. Hydrogen (Fuel 2) is fed into the combustion chamber and/or into the powder carrier gas. This approach allows either  fusing the spray material or heating it below its melting temperature, whichever is required by the conditions for optimal coating deposition for the specific feedstock material.