Residual micro- and macrostresses in the plasma-sprayed zirconia-based TBCs

Micro- and macrostresses as well as the size of coherently diffracting domains were studied with the aid of X-ray diffraction in plasma-sprayed ZrO 2-7Y 2O 3 thermal barrier coatings (TBCs) as functions of substrate temperature. The macrostresses were measured by the “sin 2Ψ”-technique, the microstresses and the domain size were evaluated from X-ray line broadening. The changes in the macrostresses were explained by differences in the thermal contractions of the ceramic layer and the metallic substrate, while the variations in the microstresses were attributed to the growth of the m-ZrO 2 phase with the increase of the substrate temperature during deposition. The increase in dislocation density associated with the formation of the m-ZrO 2 phase was revealed by XRD and was also confirmed by transmission electron microscopy.