Evaluation of the Thermophysical Properties of Functionally Graded Materials at High Temperatures by the Photothermal Radiometry

Abstract

Thermal barrier coatings and functionally graded materials (FGM) have been applied to a turbine blade exposed to high temperatures. Therefore, the evaluation of thermophysical properties of these coating materials is very important for designing turbine blade. We have adopted the photothermal radiometry (PTR) for the measurement of thermophysical properties of FGM at high temperatures. In this method, a layered sample is periodically heated by a modulated light source and periodic temperature variation is caused on the sample. The phase-lag between the modulated light source and the temperature variation on the sample contains information of thermal properties of the sample. We have measured the thermal diffusivity and thermal conductivity of round-robin FGM (single layer) at room temperature and compared the present results with other data obtained by the laser flash method. The average deviation of the other data from the present results was 14% both for thermal diffusivity and the thermal conductivity. We have measured the thermal diffusivity and thermal conductivity of FGM in the temperature range up to 1 273 K.