Thickness Assessment of Thermal Barrier Coatings of Aeroengine Blades Via Dual-Frequency Eddy Current Evaluation

A thermal barrier coating (TBC), consisting of the top and bond coatings, is normally deployed over the alloying body of an aeroengine blade in order to protect the blade from hostile environments. Thickness loss of TBC severely undermines the structural integrity of blades, and thus leads to the failure of aeroengines. Before catastrophic accidents occur, it is important to nonintrusively assess the TBC thickness via effective nondestructive evaluation (NDE) techniques. In this letter, the dual-frequency eddy current technique (DFEC) in conjunction with an efficient inverse model is intensively investigated for quantitative evaluation of TBC thickness in micrometers. The thickness of both top and bond coatings are assessed simultaneously. Comparison between the estimated TBC thickness of blade specimens and true values acquired using scanning electron microscope (SEM) indicates that DFEC is applicable for quantitative evaluation of TBC thickness without much loss of accuracy.