In this process the coating material in powder form is melted in a hot plasma flame and propelled on to a prepared substrate surface to form a coating. When the spray contacts the prepared surface of a substrate material, the fine molten droplets rapidly solidify forming a coating.
Plasma Spray Process：
Plasma spray system consists of a Plasma Spray Gun, Power Source, Powder Feeder, Control unit and Heat Exchanger. Plasma is formed inside the specially designed plasma spray gun, by introducing a high intensity electric arc between a cathode (tungsten electrode) and anode (nozzle) assembly. Plasma forming gas is introduced in this arc, where it gets ionised to form a plasma. When this plasma exits the special design convergent
Wire Flame Spray
The process is basically the spraying of molten metal onto a surface to provide a coating. Material in wire form is melted in a flame (Oxy-Acetylene flame most common) & atomised using compressed air to form a fine spray. When the spray contacts the prepared surface material, the fine molten dropletsw rapidly solidify forming a coating.
WIRE ARC SPRAY
This form of thermal spraying uses wire material as a feed stock. An electric arc is used as the heat source. As the wires are fed towards each other, an electric arc is struck between the wires creating a temperature of around 4,000°C.
The HVOF (High Velocity Oxy-Fuel) Thermal Spray
The HVOF (High Velocity Oxy-Fuel) Thermal Spray Process is basically the same as the combustion powder spray process (LVOF) except that this process has been developed to produce extremely high spray velocity.
Oxygen and fuel (acetylene most common) is fed into the barrel along with a charge of powder. A spark is used to ignite the gas mixture and the resulting detonation heats and accelerates the powder to supersonic velocity down the barrel. A pulse of nitrogen is used to purge the barrel after each detonation. This process is repeated many times a second. The high kinetic energy of the hot powder particles on impact with the substrate results in build up of a very dense and strong coating.