Quality evaluation for air plasma spray thermal barrier coatings with pulsed thermography

Pulsed thermography (PT) as a non-contact non-destructiv e evaluation (NDE) technique was employed to examine as-sprayed air plasma spray (APS) thermal barrier coatings (TBCs) for quality eval uation. Thickness and micro-structural characteristics play a vital ro le in determining the quality. In this pape r, PT logarithmic peak second-derivative m ethod was adopted to measure the thickness of top coat. Time dependent ther mal images were used to characterize the microstructure which was confirmed by scanning electron microscope (SEM). The results showed that there was relationship between the temperature distribution of the surface and microstructu re change in TBCs. Temperature distribution in thermal images and measurement results of thickness were in fairly good agreement with the microstructure change. It can be concluded th at it was possible to employ these NDE methods as quality evaluation for as-sprayed TBCs.