Quantitative inspection of thickness of thermally sprayed coatings by flash pulse thermographic method

Abstract

Flash-pulse thermography is a method for a detection of discontinuities or inhomogeneities in materials at their surface. It is based on an excitation of an inspected sample by a short pulse and analysis of its thermal response. An application of flash-pulse thermography for a quantitative inspection of thickness differences of thermally sprayed coatings is introduced in this contribution. Requirements for a synchronization of thermal response recording and data smoothing precision are described. Signal derivative, pulse-phase and time power-transformation (P-function) methods for an evaluation of the thermographic records are presented. Procedure and results of the inspection are demonstrated on HVOF, TWAS and flame sprayed coatings. A comparison of the method showed that the P-function method is the most suitable for a quantification of coating thickness differences. Some characteristic of the method are demonstrated by numerical computation.