Abstract
Thermal conductivity of thermal barrier coating (TBC) with porous microstructure is examined by characterizing porosity, pore size and its orientation in order to contribute to develop advanced TBC with a low-thermal-conductivity. In this study, TBC with various kinds of porosity is deposited by atmospheric plasma spraying technique, and porosity was controlled by adjusting a weight percent of polyester powder involved in a spraying powder. Thermal conductivity for free-standing TBCs is measured by laser flash measurement. In order to relate between microstructure and thermal conductivity of TBCs, steady-state heat transfer analysis is performed using the finite element model reconstructed from SEM picture. As a result, it was found from laser flash measurement that thermal conductivity was decreased exponentially with increasing porosity, and was coincided completely with the result estimated from finite element model. In order to clarify influence of shape and orientation of pore on thermal conductivity, the model idealized by which elliptical-shaped pore was regularly arranged was also analyzed. It was confirmed that thermal conductivity could be affected by area projected on the plane normal to a heat flow direction.
