Schlüsselwörter: Diagnostik / Gasgeschwindigkeit / Laserstreuung / Particle Imaging Velocimetry (PIV) / Überschall / Thermal spraying, as one of the key industries of the 21st century, is being developed particularly due to its potential in reducing production costs. The possibility of a deposition of high quality coatings requires a deep knowledge of each step involved in the spraying process. One important factor are the properties of the gas flow close to the outlet of the flame generator, if the reproducibility of the sprayed coatings is to be achieved, as well as their production cost reduction. The optimisation of the injection parameters for different powders is the main object of this work. This paper presents a robust contact-less optical diagnostic technique for high velocity gas flows, based in the measurement of the Doppler shift of scattered laser light. Additionally, in order to validate these measurements, a supersonic nozzle of known Mach number at outlet has been designed and measured with the well established particle imaging velocimetry technique.

In cold spray and thermal spray applications, one of the primary factors affecting coating deposition is the location where particles are injected into the gas jet. Therefore, a detailed knowledge of the gas flow distribution at that location is required. Use of non-resonant laser scattering allows to spatially resolve the distribution of drift velocity and mass density within the flow, particularly, at locations close to the injector. Based on this technique, this article presents a new diagnostic to locally measure drift velocity and relative mass density distribution of a gas stream. Its application is mainly focused on cold gas flows, where velocity measurements in a supersonic nozzle, obtained by means of laser scattering correlate well with theoretical calculations and particle image velocimetry (PIV) experimental results.