Digital Speckle Imaging for In Situ Monitoring and Characterization of Laser-processed Refractory Coatings

The use of high-temperature laser densification/annealing techniques for enhancing materials surface characteristics has opened new opportunities in material/laser-process diagnostic instrumentation. Important issues in fabrication of reproducible refractory ceramic coating film lies in understanding of the interrelationship between processing parameters and surface properties. To respond to this need, the proposed project involves the development of diagnostic instrumentation based on laser speckle imaging for in situ process monitoring and quantitative characterization of high-temperature structural ceramic coating properties. The program is innovative in correlating process parameters relating to coating-sensitive properties at temperatures exceeding 1500 degrees C. Variations in surface-reflected optical images in terms of speckle spatial frequencies and correlation intensities, due to different glass phase transformations, will identify characteristic signatures associated with film formation. Phase I Technical Objectives include the analysis of randomly scattered laser speckle characteristics for optically rough surface coatings, evaluation of laser speckle imaging techniques for measurement of micro-surface properties, assessment of empirical correlation on experimental parameters and optimization of a proof-of-concept instrumentation for in situ monitoring of laser-processed refractory ceramic coating films.