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This research work aims to establish the potential of defect detection of thermal sprayed surface coatings by using a newly developed optical non-destructive interferometric technique – Electronic Speckle Pattern Shearing Interferometry (ESPSI), rather than using mechanical destructive testing methods and other non-destructive methods. This technique has been used in many industries for non-destructive testing (NDT). However, it is innovative to use this technique for NDT of thermal sprayed metal alloy coatings, especially those that are produced by flame powder spraying process. Investigations were carried out by the SUPERJET spray process, which was the flame powder spray process utilised in this research to produce coating samples. Recommendations have been made to optimise the thermal spraying process. Microstructure analysis of various surface coatings was conducted and discussions have been made based on the images obtained. Mechanical measurements were made on a number of thermal sprayed coating samples, including coating hardness measurement, coating surface roughness measurement and coating residual stress measurement. Coating surface roughness was also measured by the White Light Interferometry (WLI) method, and the results obtained were compared with the results obtained by mechanical measurements. The comparisons showed a very good agreement between them. Defect detections have been made on various coating samples. The results showed that ESPSI technique can be applied successfully to surface coating for quality inspection and it is very effective for delamination detection.
Xue, Yueqiang (Thesis), "Thermal Sprayed Surface Coatings and Optical Characterisation" (2006). Masters. Paper 6.