Calculated and Measured Oxygen Contents in the Gas Flow of a Shrouded Thermal Spray Process

Shrouding a thermal spray process to reduce the oxidation of particle stream is not a new concept. Nevertheless the actual use of this idea is not very widely used in practice, due to some problems arising. In this paper the results of the study performed to optimize two shrouding devices for thermal spray are presented. Gas flows inside the device and in between its outlet and the target were modeled by Computational Fluid Dynamics both for an arc-wire and a plasma system. To validate the modeling methodology measurements were performed of the oxygen content using a gas sampling probe and a paramagnetic O₂ analyzer. A good agreement between calculated and measured O₂ values was obtained. Modeling results in different conditions could suggest the best shroud configuration and shielding gas flows necessary to reduce the oxygen content around the particle stream at very low values. Coatings with very low defect contents can now be produced.