POWRE: Electron Microscopy Studies of the Microstructure and Chemistry of Interfaces in Thermal Barrier Coating Systems

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This project investigates the microstructural, compositional, and bonding aspects of the topcoat/thermally grown oxide(TGO)/bondcoat interfaces to understand and control the spallation problem of thermal barrier coatings. The goal is to develop a set of materials and processing recommendations which will produce a TBC(thermal barrier coating) system with improved reliability and a reduced propensity for spallation. A secondary goal is to tailor this improved TBC system to withstand higher operating temperatures in aircraft turbine applications. Electron microscopy(TEM) will be used to examine the phases present in alumina as a function of processing conditions and thermal cycling. The objective is to correlate any phase transitions that occur in the alumina layer during TBC processing to spallation. Trace additions of reactive elements can lead to the formation of different oxides, and this will be investigated as a function of bondcoat chemistry by probing grain boundaries in the bondcoat layer and the TGO/ bondcoat interface for the segregation of reactive elements. A combination of high resolution imaging and electron energy loss spectroscopy (EELS) provided by an ultrasmall probe in a UHV STEM will be used to study this segregation issue. The goal is to use bonding information obtained from EELS to determine the effect of the presence of other oxides on the strength of the TGO/bondcoat interface.%%% This is a research enhancement grant made under the Professional Opportunities for Women in Research and Education (POWRE) program. The research will contribute basic materials science knowledge relevant to thermal barrier coatings used in aircraft turbines. The project encourages the integration of research and education through direct graduate student participation in research related to classroom activities. The project is co-supported by the Division of Materials Research, and the MPS OMA(Office of Multidisciplinary Activities). ***