Phase of thermal emission spectroscopy for properties measurements of delaminating thermal barrier coatings

Phase of thermal emission spectroscopy is developed for determining the thermal properties of thermal barrier coating (TBC) in the presence of thermal contact resistance between the coating and the substrate. In this method, a TBC sample is heated using a periodically modulated laser and the thermal emission from the coating is collected using an infrared detector. The phase difference between the heating signal and the emission signal is measured experimentally. A mathematical model is developed to predict the phase difference between the laser and the measured emission, which considers the coating properties and the thermal contact resistance of the interface. An electron-beam physical vapor deposition thermal barrier coating with local regions delaminated by laser shock is characterized using this technique. The measurements are made on two regions of the coating, one where good thermal contact between the coating and substrate exists and the other where the interface has been damaged by laser shock. The results for the thermal properties and thermal contact resistance of the interface are presented and compared