Achieving this requires more than simply increasing particle temperature and velocity. The key lies in finding the optimal balance between the thermal and kinetic energy transferred to the particles.
Kinetic energy, in particular, offers significant opportunities for process optimisation. Higher combustion chamber pressures can generate higher flame and particle velocities, while precise control of process parameters makes it possible to tailor coating characteristics to specific applications.
Based on these principles, Flame Spray Technologies (FST) developed the eGun™ System, an ethanol-fuelled liquid HVOF system that has since established itself as a proven technology for demanding coating applications.
Proven high-pressure HVOF performance
At the heart of the system is the eGun™, capable of operating at combustion chamber pressures of up to 13 bar (188 PSI). These higher pressures enable increased particle velocities and provide a wide operating window for optimising coating characteristics.
Depending on the material, particle size distribution and process parameters, measured particle velocities have reached up to 850 m/s for chromium carbide and 750 m/s for WC-CoCr powders.
The combination of a pre-combustion chamber and compact main combustion chamber provides efficient fuel preparation and combustion. Together with radial powder injection, this gives operators greater control over particle heating and acceleration.
Parameters can be adjusted from slower, hotter conditions for bonding layers to high-velocity conditions for dense, high-integrity coatings.
Why ethanol?
Using ethanol instead of conventional kerosene offers several practical advantages. Ethanol is a consistent, widely available, non-petroleum-based fuel that burns cleanly without soot or ash formation. It also allows fuel-rich operation without the same risk of carbon contamination.
The efficient combustion process can reduce oxygen consumption by approximately 30–50% compared with conventional kerosene processes. In addition, the compact combustion module can reduce cooling requirements by up to 50%, helping to lower energy consumption and operating costs.
A wide and flexible process window
Because ethanol combustion does not produce soot, the eGun™ can be operated with oxygen-rich, neutral or fuel-rich parameters. This wide operating window creates additional opportunities to tailor coating microstructures using conventional thermal spray powders.
Accurate monitoring of fuel and oxygen flows, pressures and cooling-water temperatures provides precise control over the combustion process. This level of process control supports repeatable coating quality and makes the system suitable for a wide range of industrial applications.
A complete and established HVOF system
The eGun™ is integrated into FST’s mass-flow-controlled HVOF system and operated through a full-colour touchscreen with recipe storage. Fuel, gas and electrical components are separated into dedicated modules, while integrated flow, pressure and temperature sensors continuously monitor process conditions.
The system can be supplied with the FST-20/MC Powder Feeder or integrated with other commercially available powder feeders. A mobile configuration is also available for applications requiring greater flexibility.
Today, the eGun™ represents a proven liquid fuel HVOF technology, combining high combustion pressure, efficient energy utilisation and flexible process control. Its established performance demonstrates that high coating quality, process efficiency and reduced resource consumption can successfully go hand in hand.
Improve your HVOF coating process and discover the possibilities of the eGun™ System.