In the combustion chambers of gas turbine engines, ZrO2-8wt.%Y2O3 (YSZ) TBCs are commonly applied by air plasma spray (APS) using Ar-/H2-based plasmas via legacy torches. Alternatively, N2/H2 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 N2-based plasmas with different YSZ powders using Metco 9MB legacy torch. The use of N2-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 N2-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 N2-based LD-B YSZ TBC. In the furnace cycle test, the performance of the TBCs prepared with the N2-based plasma was superior to that of the TBCs prepared with the Ar plasma, and also exceeding that of an industrial APS TBC benchmark.
Keywords: APS; Ar-H2; N2-H2; TBC; YSZ; deposition efficiency (DE); thermal conductivity; thermal cycling (FCT).
© ASM International 2021.