Evaluation of adhesive strength of thermal-sprayed hydroxyapatite coatings using the LAser Shock Adhesion Test (LASAT)

The adhesive strength between a coating and a substrate is an important factor that characterizes the quality of thermally sprayed Hydroxyapatite (HA) coatings such as those for biomedical applications. In this study adhesive strength was evaluated by the LAser Shock Adhesion Test (LASAT) technique. LASAT was developed to be suitable for determining the coating-substrate adhesion. This study deals with hydroxyapatite coatings on Ti-based alloy substrate produced by atmospheric plasma spraying. In order to discuss the influence of the spray condition on adhesive strength, different types of specimens, i.e. from various powder feed rate spraying and different surface roughness, were LASATested. The results showed that the adhesive strength decreases with increasing number of impinging particles on a given area of surface in unit time. Furthermore, the adhesive strength tendency of low-roughness substrate specimens showed scatter. This tendency depends on the surface profile i.e. skewness value. Consequently, not only the height direction roughness parameter but also the wavelength of roughness, roughness morphological parameter and powder feed rate are important factors for the adhesion of the thermally sprayed HA coatings.