Influence of Substrate Temperature on Adhesion Strength of Cold-Sprayed Coatings

Cold spraying is a promising process for fabricating functional coatings. Because of solid state particle deposition, the electrical and chemical properties of cold-sprayed coatings are almost similar to the bulk materials. The most important factor in depositing a particle through cold spraying is known as the critical velocity. When the particle velocity is beyond the critical velocity, the plastic deformation of both the sprayed metallic particle and the metallic substrate causes the removal of surface oxide layers and newly-formed surfaces are exposed. The newly-formed surface yields the metallic bond, and then cold spray deposition can occur. Therefore, the substrate conditions must also be considered in order to understand the cold spray process. In this study, the influence of substrate temperature on the adhesion strength of coatings was investigated by substrate pre-heating. The adhesion strength was examined by a shear adhesion test. This showed that substrate pre-heating enhances the adhesion strength with a specific combination of coating and substrate materials. Thermal stress and substrate surface oxidation have been suggested ss the causes of these.