Nanostructured Partially Stabilized Zirconia as an Interlayer in a Multi LayeredThermal Barrier Coating

摘要

Stresses developed within a thermal barrier coating (TBC) dueto the mismatch in thermal expansion of different coatingcomponents can cause coating failure. Nanostructuredmaterials have an increased volume fraction of grainboundaries and this microstructural attribute may allowcoatings to relieve the strain in the coating structure therebyimproving the effectiveness and the lifetime of the TBC. Multi– layered TBCs were prepared using two techniques;atmospheric pressure plasma spray (APS) using a commercialsystem, and reduced pressure plasma spray using the TripleTorch Plasma Reactor (TTPR). The coatings were depositedon mullite and on NiCrAlY-coated steel substrates, andconsisted of an inter – layer of nano-phase partially stabilizedzirconia (n – PSZ) and a layer of conventional partially yttriastabilized zirconia coating (c – YSZ) as the top thermal barriercoat. The coatings were heat treated at various temperaturesand the microstructural changes analyzed using scanningelectron microscopy (SEM) images. Mechanical properties ofthe coating were studied using four point bend testing to betterunderstand the effect of the n-PSZ inter-layer on the strainrelief mechanisms that may be operative within the TBC.