Suspension Plasma Spraying: Process Development and Applications

Suspension plasma spraying (SPS) offers the establishment of unique microstructures which are not possible with conventional powdery feedstocks. Due to the considerably smaller size of the droplets and also the further fragmentation of these in the plasma jet the attainable microstructural features like splat and pore sizes can be extremely small down to the nanometer range.
Our present understanding of the deposition process including injection, suspension plasma plume interaction and deposition will be outlined. The drawn conclusions are based on analysis of the coating microstructures in combination with particle temperature and velocity measurements as well as enthalpy probe investigations. The last measurements with the water cooled stagnation probe gives valuable information on the interaction of the carrier fluid with the plasma plume.
Meanwhile different areas of application of SPS coatings are known. In this talk the focus will be on coatings for energy systems. Thermal barrier coatings (TBCs) for modern gas turbine are one important application field. SPS coatings offer the manufacture of strain tolerant, segmented TBCs with low thermal conductivity. In addition, highly reflective coatings, which reduce the thermal load of the parts from radiation, can be produced. Further applications of SPS coatings as cathode layers in solid oxide fuel cells (SOFC) and for photovoltaic applications will be presented.