Characterization of Ceramic Coatings by Advanced Nondestructive Evaluation Methods

A number of new, noncontacting techniques for nondestructive evaluation using thermal wave methods have been recently developed. The application of these techniques to the problem of characterization of ceramic coatings is described with emphasis on the selection of the appropriate thermal wave technique for the geometry and material parameters of the system under investigation. Details of a time-resolved infrared technique are given along with a theoretical model for the time-dependent surface temperature. The roles of coating thickness and coating and substrate thermal properties are examined as factors determining the detect-ability of subsurface structure in coating systems. Finally, examples of application of these techniques to model and engineering coatings systems will be given.