HVOF spray guns are a part of a thermal spray coating system in the HVOF process. The HVOF process efficiently combusts oxygen and a gaseous or liquid fuel to produce high kinetic energy with controlled heat input. The coating material, in powder form, is introduced into and uniformly heated by the hot gas stream to a molten or semi-molten condition. The flame and powder are accelerated by a converging/diverging nozzle (air cap) to produce supersonic gas and particle velocities, which propel the powder particles toward the substrate to be coated. The powder particles flatten plastically upon impact with the substrate; cooling and solidifying to form the coating. High particle velocities, uniform heating and low dwell time combine to produce coatings that are very dense and tightly bonded to the substrate. Coating chemistries are more predictable and coatings have fine, homogeneous microstructures.
Liquid-fuel HVOF gun. Gas-fuel HVOF gun works slightly different.