Quantitative inspection of coating thickness by flash-pulse thermography and time-power transformation evaluation

Thermographic testing is an inspection method that primarily indicates the presence of discontinuities in a tested sample. Its application to coatings can indicate a presence of local thickness variations; however, it mostly does not bring any quantitative information about the thickness of the coatings. This contribution is focused on a quantification of the thermographic inspection, which would make possible an evaluation of coating thickness differences. Flash-pulse thermographic testing was applied to thermally sprayed coatings. The importance of a precise synchronization of flash source and thermographic recording was determined. Different evaluation methods were analyzed, and their comparison showed that a time-power transformation method is the most suitable for quantification of the inspection results.