Non-Destructive Evaluation of Thermal Barrier Coatings Using Direct Heat Flux Method

Thermal barrier coatings are essential for reliable and efficient turbine engines. The coatings allow the engine to operate at higher temperatures and protect the super alloy components within the hot section. Turbine hot section components have complex geometries. Complex geometries can lead to inconsistent coatings. It is critical to determine which components have defective coatings because engine manufacturers warranty these parts and under life parts have large costs associated with them. Non-destructive detection of damage progression is useful for accurate part lifetime prediction and also in root cause analysis. The present thesis describes a new, non-destructive approach to test thermal barrier coatings. The approach was implemented using custom hardware. In initial testing, defects were successfully detected under a thermal barrier coating as well as under both a thermal barrier coating and bond coat. The approach is based on obtaining temperature maps of the coating on the surface with a long-wavelength IR camera and temperature maps of the metal to ceramic interface with a mid-wavelength IR camera. This separation is possible due to the spectral absorption properties of the thermal barrier coating. This work delivers a first proof-of-concept non-destructive detection for defects in thermal barrier coatings.