Influence of dopant on the behavior under thermal cycling of two plasma- sprayed zirconia coatings Part 2: residual stresses

The evolution of coating morphology and surface residual stresses was followed for three different pow-ders: zirconia stabilized with 8 wt% yttria (YSZ), 9.9 wt% dysprosia (DSZ), and 9.8 wt% ytterbia (YbSZ). The YSZ reference powder was fused and crushed (-45 +22 μm), and the other two were agglom-erated and sintered (-90 +10 μm). According to the size distributions and manufacturing process, the plasma-sprayed YSZ particles were fully molten, resulting in dense coatings with good contact between the splats; the DSZ and, especially, the YbSZ particles were partially molten. In general, the surface residual stresses were slightly compressive before thermal cycling. The YSZ and DSZ coatings were insensitive to aging (600 h in air at room temperature), as shown by the surface stress evolution, which was not the case for YbSZ coatings. Six hundred furnace thermal cycles from 1100 °C to room temperature indicated excellent behavior of YSZ and DSZ coatings, with almost no variation of sur-face residual stresses, compared to a high dispersion for YbSZ coatings with the development of macrocracks parallel and perpendicular to the substrate within the coating.