Non-destructive thermal property measurements of an APS TBC on an intact turbine blade

The ability to measure the properties of thermal barrier coatings (TBCs) applied to engine components is challenging due to the complex geometry of parts and the difficulty of preparing samples suitable for conventional techniques. As a result, there is a shortage of information related to the morphology and thermal properties of coatings on engine components. Phase of photothermal emission analysis (PopTea) is a relatively new non-destructive technique that is suitable for measuring the thermal properties of coatings on serviceable engine parts. To demonstrate this capability, measurements are performed on an intact turbine blade coated with air plasma sprayed (APS) 7 wt.% Y2O3-stabilized ZrO2 (7YSZ). The average thermal diffusivity of the coating applied to the blade was ~ 0.5 mm2/s which is typical for thermal diffusivity previously measured on 7YSZ APS coatings made on test coupons with PopTea and laser flash. Furthermore, trends in thermal properties over the blade are studied and compared. It is discovered that variations in thermal properties are the result of differences in coating porosity.