Influence of substrate curvature on the bonding strength of TBCs via non-destructive testing research

In order to understand the failure mechanisms of the thermal barrier coatings(TBCs) applied on the aviation turbine engine blades with complex profiles, two kinds of TBC samples are prepared on plated and curvatured substrates, respectively. The evolutions of the microstructure and interface bonding strength of the TBCs during thermal cycling are investigated via AC impedance spectroscopy (IS) and Rockwell hardness (RH) indentation test. The AC IS results show that the themally grown oxide (TGO) layer thickness and micro-cracks grew with increasing thermal cycling for both samples, while an accelerated degradation is observed for the curvatured one. The RH indentation results confirm that the curvatured sample exhibites a relatively lower interface bonding strength than plated sample.