One of the most effecting parameters for the wire arc spraying with the regard to the properties of the sprayed coatings is the flow characteristic of the atomizing gas. Depending on the nozzle inner contour at the entrance of the torch, the atomizing gas is emanating the nozzle as a non-adjusted supersonic gas jet, either under- or over expanded. Thus, a convergent-divergent nozzle with a bell-shaped divergent exit is designed in order to generate a completely expanded atomizing gas flow inside the nozzle without any shock nodes in the emanating gas jet. The influence of the flow characteristic of the atomizing gas (air) on the droplet velocity is investigated by Laser- Doppler-Anemometry measurements. The coating quality is characterised with regard to the surface roughness and porosity.

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