Dresden 2009 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 32: Topical Session High Temperature Materials III

MM 32.2: Talk

Wednesday, March 25, 2009, 17:15–17:30, IFW A

Load rate dependence of the mechanical properties of thermal barrier coating systems — •Nikolay Zotov¹, Marion Bartsch², and Gunther Eggeler¹ — ¹Institut für Werkstoffe, Ruhr Universität Bochum, 44780 Bochum — ²Institut für Werkstoff-Forschung, DLR Köln, 51147 Köln

Thermal barrier coatings (TBC), composed of yttrium-stabilized zirconia (YSZ) ceramic top coat (TC) and intermetallic NiCoCrAlY bond coat (BC) are commonly used as protective coatings of Ni-based high temperature gas engine components. Nanoindentation techniques are increasingly applied for determining the TBC mechanical properties on a nanometre scale. However, little is known about the load-rate dependence of the mechanical properties, which is important for better understanding of cyclic thermal fatigue experiments. Nanoindentations with different load rates omega were performed on polished cross-sections of TBC, deposited by EB-PVD on IN625 substrates (S), using a XP Nanoindenter (MTS) equipped with Berkovich diamond tip. The Young's modulus (E) of the TC is independent of omega, while E for the BC and the S decreases with omega. The hardness (H) of the TC and the BC increases, while H for the S decreases with omega. From the dependence of H on omega, creep power-law exponents c = 0.24(11) and c = 0.023(6) for the TC and the BC were determined. For all TBC components, a decrease with omega of the power-law exponents n and m, describing the loading and unloading nanoindentation curves, is observed.