Influence of spray angle onto the microstructural and mechanical properties of air plasma sprayed 8YSZ TBCs

In this paper, the air plasma sprayed 8YSZ TBC was deposited onto the Inconel 800 with NiCrAlY bond coat using spray angle variation. The comparative study was conducted to evaluate the change in microstructural and mechanical properties with the effect of spray angle. The 8YSZ TBCs were deposited using 90° and 60° spray angles. The microstructural examination with elemental analysis was done by SEM and EDS. The mechanical properties such as porosity, hardness, and surface roughness were determined using SEM image analysis with greyscale threshold, indentation test, and surface profilometer technique. The experimental result shows the spray angle effect over the structure in grain growth behaviour, defects like pores, cracks, and surface irregularities. The 90° showed a uniform grain growth structure with few defects compared to the 60° spray angle. The spray angle 60° shows large amount of defects resulting in decreased hardness, surface roughness, and increased porosity. Also the shadow region obtained is high leading to large porous structure developing rough surface.