Durability And Lifetime Improvement In Thermal Barrier Coatings From The Superalloy Modified With Hf And/Or Y

Thermal cyclic lifetime and microstructural degradation for thermal barrier coatings (TBCs) of Yttria-Stabilized Zirconia (YSZ) deposited on the Hf- and/or Y-modified CMSX-4 superalloy substrate with (Ni, Pt) Al as a bond coat were examined. Also, a beneficial role of reactive element (RE) on the durability of TBCs was systematically investigated. In this study, thermal cyclic lifetime of TBCs was measured using a furnace thermal cycle test that consisted of 10-minute heat-up, 50-minute dwell at 1135 °C, and 10-minute forced-airquench. As a result, TBC lifetime was observed to improve from 600 cycles to over 3200 cycles with appropriate Hf- and/or Y-alloying of CMSX-4 superalloys, where each thermal cycle consisted of 10-minute heat-up, 50-minute dwell at 1135°C, and 10-minute forced-airquench. Degradation and failure of TBCs after thermal cycling were characterized by scanning and transmission electron microscopy (SEM and TEM/STEM) and X-ray diffraction (XRD) with emphasis on rumpling, ratcheting, interfacial segregation, thermally grown oxide (TGO) growth, TGO phase constituents, TGO grain size, residual stress within the TGO scale, and martenstic transformations within the (Ni, Pt) Al bond coat. Copyright © 2009 by the American Institute of Aeronautics and Astronautics, Inc