Determination of Degree of Thermal Barrier Coating Disbonding by Time-Resolved Infrared Radiometry (TRIR)

We have previously described the time-resolved infrared radiometry (TRIR) technique and demonstrated how both measurement of coating thickness and detection of coating disbonding can be made within the same measurement [1]. We have also reported indications of the sensitivity of the TRIR technique to differing degrees of coating disbonding [2]. In the present work we examine this question in detail and compare TRIR experimental results with both an analytical multilayer theory and a destructive analysis of the coating-substrate interface. While the material system studied in this work is a zirconia thermal barrier coating on a superalloy substrate, the methodology and analytical basis of the technique are applicable to a wide variety of materials and components including printed circuit boards and composite materials. The capability of the TRIR technique for characterization of these specific systems will depend on details of the thermal properties and layer thickness in these specimens