NDE Inspection System for Detecting Flaws Under Terminal Barrier Coatings

Aircraft turbine engines continue to evolve to meet demands for smaller, lighter power plants while improving fuel efficiency and increasing power output. As a result, turbine engines must endure ever increasing operating temperatures. Turbine blades in the hot-gas path are coated with a thermal barrier coating (TBC) that reduces thermal stress and extends their service life. Thermal and centrifugal stresses can initiate and propagate cracks that cannot be seen through the TBC. A method for in-plant inspection of new blades, blades removed from service, and refurbished blades is needed. IDI proposes an NDE technique employing a novel microwave resonant stripline probe that detects changes in the dielectric thickness of the TBC, any oxide formation, as well as surface defects in the Inconel substrate. The NDE system output is a two-dimensional color image detailing the overall health of the component. Phase I will design, build and test a prototype microwave probe. Phase II will further develop the NDE microwave system for demonstration in a production line environment.