Effect of microstructure and phase of nanostructured YSZ thermal barrier coatings on its thermal shock behaviour

The purpose of this work is the evaluation and comparison of plasma sprayed nanostructured 7 wt-% yttria stabilised zirconia (t-7YSZ) with two different sizes and 15YSZ coating with cubic phase (c-15YSZ). To this end, two kinds of 7YSZ nanogranules consisting of agglomerated nanosized particles (40-50 and 90-100 nm respectively) and 15YSZ were plasma sprayed on nickel based superalloy substrates with NiCrAlY as the bond coat. The thermal shock behaviours of all as sprayed thermal barrier coatings (TBCs) were investigated at 1000 degrees C. The results indicated that the thermal cycling lifetime of nanostructured 7YSZ TBCs was longer than that of the nanostructured 15YSZ TBCs due to higher fracture toughness. Moreover, 7YSZ TBC with smaller particle size (labelled as non-commercial 7YSZ) shows better thermal shock resistance than 7YSZ TBC with bigger particle size (labelled as commercial 7YSZ) due to lower elastic modulus and residual stress.