In the combustion chambers of gas turbine engines, ZrO 2 -8wt.%Y 2 O 3 (YSZ) TBCs are commonly applied by air plasma spray (APS) using Ar-/H 2 -based plasmas via legacy torches. Alternatively, N 2 /H 2 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 2based plasmas with different YSZ powders using Metco 9MB legacy torch. The use of N 2 -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 Arand N 2 -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 2 -based LD-B YSZ TBC. In the furnace cycle test, the performance of the TBCs prepared with the N 2 -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 Á Ar-H 2 Á deposition efficiency (DE) Á N 2 -H 2 Á TBC Á thermal conductivity Á thermal cycling (FCT) Á YSZ
Nickel aluminum bronze (NAB) castings possess favourable combinations of strength and resistance to corrosion, biofouling and cavitation/erosion, and so have long been used in naval applications. Nonetheless, in seawater environments NAB castings are susceptible to selective phase corrosion and so such components periodically require either replacement, which is very costly, or repair. However, repairs involving traditional, high heat input welding operations can lead to distortion and microstructural changes that unacceptably degrade NAB corrosion performance, and so repairs are not commonly performed. In the present work, cold spray is explored as an alternative for NAB (alloy CuAl9Fe5Ni5) repair without excessive distortion or base metal degradation, and preliminary results of its performance reported. Suitable cold spray parameters have been determined using an iterative approach by analyzing deposits in terms of microstructure, porosity and adhesion to the substrate. It is intended that these parameters will later be used to create simulated repairs which can be more thoroughly characterized for strength, toughness and corrosion performance.
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