Thermal cycling behavior of suspension plasma sprayed yttria partially-stabilized zirconia thick thermal barrier coating

摘要

The present paper focused on evaluating the cyclic thermal shock performance of the suspension plasma sprayed (SPS) 7.5wt% Y_2O_3 partially stabilized ZrO_2 (7.5YSZ) thick thermal barrier coatings (TBCs). The SPS 7.5YSZ coating in thickness of approximately 720 microns was deposited on a 150 micron-thick CoNiCrAlY bond coat. The vertically segmented cracks were observed in the SPS 7.5YSZ coatings. The phase analysis shows that the coating crystallized in non-transformable tetragonal phase of zirconia. The thermal cycling test of the SPS 7.5YSZ coatings was carried out on a burner rig with propane-oxygen flame which heated the coating surface at temperature of 1523 K, followed by quenching to temperature of 423 K by compressed air. The results obtained shows that the SPS 7.5YSZ coatings performs longer thermal shock life relative to the atmospheric plasma sprayed (APS) counterparts under the same test conditions, which is probably attributed to the improvement in strain tolerance through the vertically segmented cracks therein. The failure behaviour of the SPS coatings is distinctly different from that of the APS coatings, which is supposed to be related to the special microstructure.