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Thermomechanical Fatigue Damage Evolution in a Superalloy/Thermal Barrier System Containing a Circular Through Hole
Author(s) -
Tanaka Makoto,
Mercer Christopher,
Kagawa Yutaka,
Evans Anthony G.
Publication year - 2011
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1551-2916.2011.04539.x
Subject(s) - materials science , thermal barrier coating , superalloy , composite material , yttria stabilized zirconia , temperature cycling , scanning electron microscope , residual stress , ultimate tensile strength , bending , stress (linguistics) , coating , cubic zirconia , thermal , microstructure , ceramic , linguistics , physics , philosophy , meteorology
The results of an investigation of thermomechanical fatigue (TMF) on a superalloy specimen, with an applied thermal barrier coating (TBC) and a circular through hole, are presented. Tensile loads were applied in phase with increasing temperature. Damage evolution in the form of cracks develops in the TBC adjacent to the hole. These cracks run perpendicular to the loading axis. Stress mapping of the thermally grown oxide (TGO) using luminescence spectroscopy determined an increase in compressive residual stress with increasing TMF cycling. Scanning electron microscopy examination, following cross sectioning, determined the TBC cracks to be vertical separations of the columnar yttria‐stabilized zirconia (YSZ) top coat. Microscopic damage mechanisms in the form of plasticity (bending of YSZ columns) and TGO cracking were observed. Imperfections in the bond coat are associated with these vertical separations. Energy‐dispersive element mapping of these imperfections indicated a composition of alumina and mixed Cr, Co, and Ni oxides.