The Assessment of Surface Coatings Using Laser Ultrasound Detected with a Wideband Confocal Fabry-perot Interferometer Operating in Reflection Mode

Coating technology is used in a variety of applications, for example to improve the wear properties or to improve the bonding properties of a surface. The properties of such surfaces depend on the mechanical properties ofthe coating, namely its Young's modulus and its thickness. Tobe able to predict the performance of such coatings it is necessary to be able to measure these properties in a nondestructive way. Conventional ultrasound is one nondestructive method that has been used for coating measurement [l ]. It has the disadvantage of needing a transducer to be placed in direct contact with the material surface, often with the use of a couplant. This is sometimes inconvenient and risks contaminating the surface. Laser ultrasound offers a complete noncontact technique that prevents any surface contamination. lt also offers scanning possibilities and Iaser sensor systems can possess very broad frequency bandwidths [2,3].