Real-Time Coating Evaluation System

Manufacturing and repair processes for gas turbine engine components are often delayed while evaluating if sufficient coatings layers have been applied. Environmental conditions can significantly influence this process, resulting in a wide variability of coating thickness and properties as a function of time. Therefore, a need exists for a technology that can reliably indicate the relative state of coating. During Phase I, Metis Design will design, fabricate and test a laser-based non-contact system for evaluating coating state. The system will include a pulsed laser with beam splitter to excite Rayleigh waves in the surface layer of the coating, and a second laser interferometer to measure the displacement caused by the passing wave, and hence convey the wavespeed. The final output will be the bulk shear modulus as a function of time, which is explicitly related to the wavespeed squared. Initial tasks will seek to refine the system architecture, and analytical models will be produced to determine wave propagation parameters and hardware requirements to formulate response predictions. The final tasks will be devoted to designing and fabricating control circuit and interface hardware for system and testing a representative coating to demonstrate the overall system performance comparing response predictions to actual response. BENEFIT: There are significant benefits to using this technology over the conventional practice of either physically testing or relying on historical data. Physical testing can be very time consuming and often results in the need to remove exiting layers and re-coat the part. Historical data does not present any physical risk, however coating state can be heavily dependent on many factors that are too complex to account for in every environment. Using either of these methods the trade is time and/or cost versus the risk of a bad part. This non-contact coating state monitoring system provides the benefit of complete state knowledge without any of the risks. There exists a broad commercial market for this product. Pratt & Whitney is probably the best candidate licensing partner since MDC has an existing relationship with them, and they are integrally involved in manufacturing and processing gas turbine engine components at their own facility, as well as facilitating maintenance and repair of these components at USAF depot locations. Obviously GE and Rolls Royce are the other major turbine manufactures that could be potential customers. Aside from large aerospace entities, gas turbine engines are used in a variety of other industries, including for building power generation, naval vessels and even new concept automobiles. After proven in aircraft applications this technology could proliferate into these other industries.