2010 Volume 18 Pages 118-126
This research studied about the bonding mechanism of supersonically accelerated solid ceramic powder material in cold spray process. In order to understand the bonding mechanism of the solid ceramic particles, the structure of feedstock titanium dioxide (TiO2) particles was carefully observed with the scanning electron microscope (SEM) and the high-resolution transmission electron microscope (TEM). The SEM and TEM data clearly reveal the deformation and adhesion mechanism of the sprayed ceramic particles and the substrate. We have discovered three essential factors for solid ceramic bonding and these are related to the structures of feedstock powder. Firstly, powder has to be agglomerated to a size of about 10μm. This is the suitable particle size for high particles acceleration in the supersonic gas stream. Secondly, the powder has to be an agglomerated porous structure with nano-scaled primary particles. It is believed that porosity assists with the breaking down phenomenon of particles occurred during the cold spray process and this phenomenon influences the adhesion of ceramic particles. Finally, the powder must have primary particles that are agglomerated and oriented within a single crystal axes. This particular structure is believed to be responsible for the adhesion between TiO2 particle and substrate. These three unique structures of the feedstock powder material are required to obtain thick and defined coatings of TiO2 via cold spray process.