A blade coating inspection method based on an electromagnetic inverse scattering approach

The quantitative evaluation of blade coatings is a key task for evaluating the structural integrity in power generation plants. Several conventional techniques are available, e.g., the ones based on micrographic analysis and eddy current techniques. However, the small thickness (of the order of hundreds of microns) of the highly conductive coatings of the blades allows the use of electromagnetic fields to inspect those structures. In this paper, an innovative multi-frequency approach based on electromagnetic waves is preliminarily proposed. In this method, the coating characterization problem is formulated as an inverse scattering problem, in which the measured scattered-field data are inverted in order to retrieve the information on the relevant diagnostic parameters. A new and efficient inversion technique, which exhibit high regularization capabilities, is employed. In this paper, the proposed approach is preliminary validated by means of a simplified structure, in order to study its feasibility for the solution of the coating characterization problem.