Non-Destructive Evaluation of Thermal Spray Coatings Using Ultra-High Frequency Micro-Induction Inspection Technology

The U.S. Air Force needs to non-destructively and easily inspect thermal spray metallic and ceramic thermal spray coatings on critical surfaces of gas turbines. Current methods fail to adequately detect sub-surface and interfacial defects, and are cumbersome to use, particularly with conformal geometries.Issues exist with capturing accurate measurements over a range of coating and substrate materials. Finally, inspection data must be interpreted by skilled operators that are subject to misinterpretation.Grid Logic has developed the foundation for a new non-destructive inspection technology called Micro-Induction Inspection (MII). This technology uses an ultra-high frequency resonant circuit inductively coupled to a substrate to measure the characteristics of a composite test sample. The technique is not only sensitive to variations in the substrate surface, but also to sub-surface and interfacial variations. In this Phase I project, MII sensors will be developed that are tuned to the materials used in metallic and ceramic thermal sprays on jet turbines. The potential for a system will be demonstrated to precisely detect flaws by measuring complex impedance variations. The project will establish a foundation for development of a full-scale non-destructive evaluation system in Phase II that can be easily used by the Air Force.