Suspension Plasma Spraying (SPS) is a relatively new deposition process which enables to spray micron and submicron particles. It offers the possibility to form finely structured coatings with intermediate thicknesses of a few tens of microns. In order to have a better understanding in SPS, the two parts of this paper are devoted to the description of the phenomena involved in this spray process. The first part focuses on the suspension injection within a d.c. plasma jet. Simplified models, backed by plasma and suspension diagnostics, allow describing the interaction plasma-suspension. It is shown that the suspension is atomized by the plasma jet before the starting of the droplets vaporization. The plasma jet recovers its flow symmetry about 15 mm downstream of the nozzle exit. The strong influence of plasma instabilities on suspension injection is also highlighted. The second part is devoted to solid particle treatments and the coating formation.

The first part of this paper was devoted to phenomena related to liquid injection in the Suspension Plasma Spraying (SPS) process. This second part emphasizes the solid particles treatment and the coating generation. A simplified theoretical approach is proposed to evaluate the influence of the numerous experimental parameters on heat and momentum transfers from the plasma jet to individual particles. It is shown that small solid particles vanish by vaporization and are very sensitive to plasma arc fluctuations and thermophoresis effect, which makes particles to escape from the jet. This study is completed by experimental investigations concerning, first, in-flight collection of particles and, second, coating elaboration. The importance of the particle size distribution of the injected powder and the parameters for the plasma generation is demonstrated, as their choice can give either porous or dense coatings.