Segmentation cracks in plasma sprayed thin thermal barrier coatings

Thick thermal barrier coatings (TBCs) containing segmentation cracks have seen a successful application in combustion chamber parts. In this work, rather thin TBCs were produced by spraying yttria stabilized zirconia (YSZ) coatings onto two kinds of bond coats: CoNiCrAlY and Pt-Ir. The effects of process parameters including substrate temperature on the density of segmentation cracks were studied. The thermal cycling performance and failure mechanisms of the segmented thin TBCs were also investigated. The coating sprayed at 1073 K contains a segmentation crack density of approximately 5 mm^-1. The segmented coatings significantly improved the thermal cycling lifetime as compared with the non-segmented coatings. The segmented TBC with Pt-Ir bond coat attained a lifetime of more than 5000 cycles (each cycle includes 3 minute heating up to the maximum temperature and 7 minute holding at the temperature), revealing an excellent thermal cycling performance.