HVOF refinement for screw conveyors

The HVOF method

The HVOF method is a process for refinement of screw conveyors. The screw conveyors made of tool steel are roughened to start. A gas mix is now ignited with a special gun, which causes the metallic powder particles to melt, and they are shot onto the screw conveyor at a speed of 750m/s. The kinetic energy of the impact produces additional heat, supports the bond and increases the density; the required hardness levels are achieved.

The screw conveyor is fully encapsulated with this method.

A layer thickness of up to 0.25 mm is possible. The screw conveyor has the character of a carbide screw conveyor combined with the benefit of toughness in the core. Extreme torsion stress on small screw conveyors should however be avoided.


  • No adhesions
  • Longer process cycles, infrequent cleaning
  • Improved service life
  • Increase of surface hardness
  • Reduction of surface reactions
  • Reduction of friction
  • Reduction of servicing costs
Type Härte / HRC Compostion Areas of application
GT 1000 Co 68 - 71 88% Wc / 12% Co Plasitc with high proportions of GF with a low corrosion effect, glass fibre, mineral, magnectic powder, filled plastics
GT 1000 Ni 68 - 71 88% Wc / 12% Ni K-materials with high proportions of GF and corrosion effect e.g. VO
GT 4000 55 - 65 75% Cr3C2 / 25% NiCr Extreme corrosion effect e.g. PFA, POM, PMMA, PC, Fluorpolimere, Brom, PEEK
GT 9000 68 - 71 88% Wc / 12% Co + Microcarbide Extremely high GF proportions with average corrosion effect

We recommend the above listed coatings for the respective applications:
The GT 1000 / GT 9000 coatings allow processing temperatures up to 450°C.
GT 4000 is suitable up to 600°C.