HVOF is a thermal spray system utilising the combustion of gases, such as Hydrogen or a liquid fuel such as kerosene. Fuel and oxygen mix and atomise within the combustion area under conditions that monitor the correct combustion mode and pressure.
The process creates a very high velocity which is used to propel the particles at near supersonic speeds before impact onto the substrate. One of the basic rules of spraying is that high combustion pressure = high gas velocity, high particle velocity and resulting high coating quality.
One of the key benefits of this system's high velocity is the extremely high coating density and low oxide content. The low oxides are due partly to the speed of the particles spending less time within the heat source and partly due to the lower flame temperature (around 3,000 °C) of the heat source compared with alternative processes.
Schematic of HVOF Combustion Chamber
As well as producing excellent bond strength, some HVOF coatings can be sprayed very thick due to the exceptionally high velocities producing coatings in compression instead of tension. This enables materials such as carbide to be applied very quickly in excess of 6mm.
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