Because protective coatings are becoming a widespread part of metal working, thermal
spray is a rapidly growing market.
The methods classified under thermal spraying include flame spraying, plasma spraying,
High-Velocity-Oxyfuel (HVOF), and twin-wire-arc spraying, all of which share the following
common features:
1) Production of molten particles: molten particles are formed in the spraying gun region
2) Transport of molten particles: molten particles are propelled towards the substrate to
be coated
3) Particle deposition: molten particles are deposited and flattened on the substrate,
forming solidified or sintered splats that form the coating layer.
These three common features are the basic principles underlying the thermal spray
process and are schematically shown in Figure 1.1.