The studying of splats in thermal spray is prominent to improve coating properties due to better understanding of coating build-up mechanisms. Most of studies, however, devoted to splats rest on physical aspects of the build-up, which feature the behavior of a single particle impinging on a substrate. These studies involve the nature, velocity and intrinsic characteristics of the particle.

            The present work deals with the study of the splat-substrate interface using an ultra-sonic (U.S.) technique. This technique is based on the determining of splat-substrate adhesion (for an elementary splat or a group of splats) to help in the optimizing of spraying conditions. APS copper, IPS copper and APS hydroxyapatite (HAP) splats were studied for Al and Ti-based substrates respectively.

            This U.S. technique was already tested successfully for adhesion control of thermally-sprayed coatings, as presented at ITSC 2005 in Basel, Switzerland. Further development then related to the specific experimental set-up for splat analysis using several transducers. This involved the use of various frequencies, various sizes for the focal spot and various scan velocities.

            In this study, results from this U.S. technique were discussed in the light of the obervation of cross-sections of U.S.-controled splats. U.S. C-Scan images were shown to fit well with cross-sectional images.