Environmental, Economical and Performance Impacts of Ar/H2 & N2/H2 Plasma Sprayed YSZ TBCs

Since the 1970s the Ar/H₂ plasma has been the standard APS gas system employed to deposit YSZ TBCs for the gas turbine industry. Although much less costly and yielding higher YSZ deposition efficiency (DE) levels, N₂/H₂ plasmas were discarded. This N₂/H₂ discard issue occurred due to problems like preliminary APS torch Cu-nozzle erosion (Cu contamination on TBCs) and the tendency to produce denser coatings; potentially leading to TBCs exhibiting higher thermal conductivity (TC) and lower thermal cycle lifetimes. However, in the 21^st century, environmental impact and economical aspects are becoming paramount. In addition, the introduction of new technologies (e.g., W-lined Cu nozzles, particle T & V sensors and computer-controlled automation) has increased dramatically the stability of APS processing. Therefore, the N₂/H₂ plasma concept needs to be revisited. In this paper different sets of APS YSZ TBCs were deposited via Ar/H₂ and N₂/H₂ plasmas (3MB torch). The DE, TC and furnace cycle test (FCT) were evaluated. The top-performing Ar/H₂ and N₂/H₂ TBCs exhibited equivalent FCT lifetimes and TC values within the 1.15-1.25 W/mK range at 1200^oC. Moreover, the top-performing N₂/H₂ TBC exhibited a 2-fold increase in DE and a 24% lower electricity consumption when compared to the top-performing Ar/H₂ TBC.