The Influence of Plasma Composition in the Thermal Cyclic Performance of Yttria-Stabilized Zirconia (8YSZ) Thermal Barrier Coatings (TBCs).

In the combustion chambers of gas turbine engines, ZrO-8wt.%YO (YSZ) TBCs are commonly applied by air plasma spray (APS) using Ar-/H-based plasmas via legacy torches. Alternatively, N/H plasmas could be used with the potential of increasing overall deposition efficiency (DE) and hence reduce the consumption of high-value feedstock powder. Also, by increasing DE, spraying time would be reduced, thereby providing another contribution to bring down production costs. In this work, TBCs were prepared with Ar- and N-based plasmas with different YSZ powders using Metco 9MB legacy torch. The use of N-based plasma resulted in higher particle temperature and lower particle velocity values than those provided by the Ar-based plasma. The measured DEs were between 41-43 and 53-60% for the Ar- and N-based plasmas, respectively. This represents a ~ 40% increase in the DE. The coatings produced with the two different plasmas exhibited equivalent porosity levels ~ 11-13%. On average, the lowest thermal conductivity values were given by a N-based LD-B YSZ TBC. In the furnace cycle test, the performance of the TBCs prepared with the N-based plasma was superior to that of the TBCs prepared with the Ar plasma, and also exceeding that of an industrial APS TBC benchmark.