Journal
MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING
Volume 490, Issue 1-2, Pages 26-35Publisher
ELSEVIER SCIENCE SA
DOI: 10.1016/j.msea.2008.01.006
Keywords
thermal barrier coatings; delamination; thermal gradients; cracking; environmental degradation
Categories
Funding
- Office of Naval Research [N00014-00-1-0438 (MURI)]
- NSF [DMR00-80034]
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An analysis has been conducted that characterizes the susceptibility to delamination of thermal barrier coated (TBC) hot-section aero-turbine components when penetrated by calcium-magnesium-alumino-silicate (CMAS). The assessment has been conducted on stationary components (especially shrouds) with relatively thick TBCs after removal from aero-engines. In those segments that experience the highest temperatures, the CMAS melts, penetrates to a depth about half the coating thickness, and infiltrates all open areas. Therein the TBC develops channel cracks and sub-surface delaminations, as well as spalls. Estimates of the residual stress gradients made on cross-sections (by using the Raman peak shift) indicate tension at the surface, becoming compressive below. By invoking mechanics relevant to the thermo-elastic stresses upon cooling, as well as the propagation of channel cracks and delaminations, a scenario has been presented that rationalizes these experimental findings. Self-consistent estimates of the stress and temperature gradients are presented as well as predictions of channel cracking and delamination upon cooling. (c) 2008 Elsevier B.V. All rights reserved.
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