Recent works have been devoted to achieve dense and thin (<15 µm) zirconia coatings using a relatively new process, Suspension Plasma Spraying (SPS). Nevertheless, the parameters controlling the microstructure of the deposit are not yet clearly identified, particularly for the injection of suspension. Hence, the liquid penetration into the plasma has been observed with a fast shutter (10 -5 s) camera coupled with a laser flash and triggered by a defined instantaneous voltage level of the plasma torch. This paper is focused on the treatment of the suspension jet or drops according to the suspension properties (with the viscosity, particles load, injection velocity…) and depending on the different spray parameters such as the plasma forming gas mixture composition and the plasma torch design (either PTF4 or home made torch). These works have permitted the obtention of zirconia coatings with low thicknesses (~10 µm) and dense structure (~4% of porosity).

Suspension Plasma Spraying (SPS) allows depositing finely structured coatings. This paper presents an analysis of the influence of plasma instabilities which control the interaction plasma jet-zirconia suspension. A particular attention is paid to the treatment of suspension jet or drops according to the importance of voltage fluctuations (linked to those of arc root) and depending on the different spray parameters such as the plasma forming gas mixture and the suspension momentum. By observing the suspension drops injection with a fast shutter camera and a laser flash triggered by a defined transient voltage level of the plasma torch, the influence of plasma fluctuation on drops fragmentation is studied through the deviation and dispersion trajectories of droplets within the plasma jet.