Thermal barrier coatings are extensively used in turbine industry where high performance coatings which can withstand very high temperatures and have long lifetime are required. Yttria stabilized zirconia coatings were found to best fulfil these needs; however increasing performance requirements have begun to make conventional air plasma sprayed coatings insufficient for future needs. Since the thermal conductivity of bulk material cannot be lowered easily; the design of highly porous coatings may be the most efficient way to achieve coatings with low thermal conductivity. The approach of fabrication of coatings with a high porosity level based on plasma spraying of ceramic particles of dysprosia stabilized zirconia mixed with polymer particles, has been tested. Both polymer and ceramic particles melt in plasma and after impact to a substrate they form a coating. When the coating is subjected to heat treatment, polymer burns out and a complex structure of pores and cracks is formed. In order to obtain desired porosity level and microstructural features in coatings; a design of experiments (DoE), based on changes in spray distance, powder feeding rate and plasma forming atmosphere, was performed. Acquired coatings were evaluated for thermal conductivity, thermo-cyclic fatigue and their morphology was assessed using scanning electron microscopy. It was shown that porosity level can be controlled by appropriate changes in spraying parameters.
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