Bonding mechanisms of thermally softened metallic powder particles and substrates impacted at high velocity

Thermally softened titanium powder particles were impacted at about 760 m/s onto three substrate materials, i.e., titanium, aluminum, and zirconia, at the same time. In spite of the very different physicochemical properties of these substrate materials, most of particles were bonded to the substrate. However, their microstructures suggested different dynamic deformation behaviors and interface features. On titanium or zirconia substrate, particles showed shear instability and direct metallurgical bonding or metal-ceramic bonding that resulted from the removal of oxide covered on them, while on aluminum, although the particle was not heavily deformed and its oxide remained it was also bonded to the substrate due to the instability of substrate and the removal of aluminum oxide. The results have demonstrated the complex and material dependent nature of bonding formation in kinetic spraying using thermally softened metallic powder particles.