THE HVAF METHOD
The HVAF method is a process for refinement of screws. A air fuel mix is ignited with a special gun, which causes the metallic powder particles to melt, and they are shot onto the screw at a speed of 1000–1200 m/s. The kinetic energy of the impact produces additional heat, supports the bond and increases the density; the required hardness levels are achieved.
With this method the screw is fully encapsulated.
A layer thickness of up to 0.25 mm is possible. The screw has the character of a carbide screw combined with the benefit of toughning in the core. Extreme torsion stress on small screws should be avoided.