J. Liu, B. Jayaraj, Y. Sohn, University of Central Florida, Orlando, FL
Air plasma sprayed (APS) ZrO2-7wt.%Y2O3 (YSZ) thermal barrier coatings (TBCs) with an APS NiCoCrAlY bond coat were examined for the evaluation of thermal cycling lifetime and microstructural development. The TBCs consisted of 600 um-thick APS YSZ, 175 um-thick APS NiCoCrAlY and Haynes 230 substrate, and the 1-, 10- and 50 hour thermal cycling consisted of 10-minute heat-up to 1121oC, dwell at 1121oC and 10-minute forced-air-quench. Despite the significant internal oxidation of APS NiCoCrAlY bond coat, these TBCs exhibited excellent thermal cycling lifetime. Microstructural evolution of TBCs with an emphasis on the development of thermally grown oxide including internal oxidation was examined by scanning electron microscopy, transmission electron microscopy (TEM) and scanning TEM. Oxides such as Al2O3, (Al,Cr)2O3 and (Ni,Co)(Al,Cr)2O4 within the TGO were identified by electron diffraction, and quantitative microscopy were carried out to elucidate the superior performance of these TBCs with APS NiCoCrAlY bond coats.
Summary: Air plasma sprayed (APS) ZrO2-7wt.%Y2O3 (YSZ) thermal barrier coatings (TBCs) with an APS NiCoCrAlY bond coat were examined for the evaluation of thermal cycling lifetime and microstructural development. The TBCs consisted of 600 um-thick APS YSZ, 175 um-thick APS NiCoCrAlY and Haynes 230 substrate, and the 1-, 10- and 50 hour thermal cycling consisted of 10-minute heat-up to 1121C, dwell at 1121C and 10-minute forced-air-quench. Despite the significant internal oxidation of APS NiCoCrAlY bond coat, these TBCs exhibited excellent thermal cycling lifetime. Microstructural evolution of TBCs with an emphasis on the development of thermally grown oxide including internal oxidation was examined by scanning electron microscopy, transmission electron microscopy (TEM) and scanning TEM. Oxides such as Al2O3, (Al,Cr)2O3 and (Ni,Co)(Al,Cr)2O4 within the TGO were identified by electron diffraction, and quantitative microscopy were carried out to elucidate the superior performance of these TBCs with APS NiCoCrAlY bond coats.
