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Microstructural Characterization of Porous Thermal Barrier Coatings by IR gas porosimetry and sintering forecasts

pubblicazioni - Articolo ISI

Microstructural Characterization of Porous Thermal Barrier Coatings by IR gas porosimetry and sintering forecasts

It presents a new methodology for non-destructive microstructural characterization of porous materials that is based on measurement of the thermal diffusivity of the material once that the pores were filled with gases having different properties. It is also applied to a model of sintering to make predictions on the evolution of microstructural parameters in function of time and temperature of aging.

It is known that the thermal diffusivity of plasma sprayed coatings is quite sensitive to the operating conditions, namely the composition and pressure of the operating atmosphere. This makes it possible, in principle, to obtain information, in a non-destructive way, on the microstructure of thermal barrier coatings (TBCs) from thermal diffusivity measurements. An experimental assessment of this idea is presented in this paper. The microstructure of as-sprayed and sintered free-standing atmospheric plasma sprayed YPSZ TBC samples have been characterized by a new technique, named infrared (IR) gas porosimetry, as well as by mercury intrusion porosimetry and image analysis. The results from these different techniques have been compared. Furthermore, the microstructure and thermal diffusivity of sintered samples have been compared with the sintering forecasts produced by Cipitria’s sintering code coupled with the Bruggeman model for thermal diffusivity estimation. Sample-to-sample variations have been discussed and uncertainties in experimental techniques have been analysed. Conditions for accurate microstructural estimations have been obtained and suggestions on the reliability of the statistical evaluation are provided.

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