Abstract
Build up of strain within thermal barrier coatings has been identified as one of the main reasons for coating failure. The large volume fraction of grain boundaries in nanostructured materials has been predicted to partially relieve the strain in a coating structure. In this study, the difference in morphological characteristics of regular PSZ (r-PSZ) particles and nano-agglomerate PSZ (n-PSZ) particles have been investigated to improve our understanding of the stresses and strains within a coating. The Triple Torch Plasma Reactor, a reduced pressure plasma spray system along with a pair of tungsten and molybdenum apertures was used to isolate spray particles from the plume to deposit splat sample. Cross sections of the splat samples were prepared. Image analysis techniques were used on scanning electron microscopy (SEM) images to characterize both the surface and the cross sectional features of the splat samples. Semi-molten structures were found to be the defining characteristic of the n-PSZ samples. Peak height distribution (PHD) was defined to quantify the distribution of the height of semi-molten structures. PHD was estimated for different samples and was found to track the changes in the morphological characteristics as a function of the deposition conditions.
