Impact velocity-dependent bonding mechanisms in metal cold spray

In this paper, we probe the bonding mechanisms for an impacting particle on a substrate, as in the cold spray process, over a range of impact velocities using molecular dynamics simulations. For the model copper/copper system, we find that grain boundary-like amorphous phase interlocking and metallurgical bonding are dominant at low and medium impact velocities, respectively, while metallurgical bonding and mechanical interlocking are dominant at high impact velocities. In particular, features including substrate crater depth, particle flattening ratio, and jetting area are tracked with varying impact velocities to further enhance our understanding of the underlying bonding mechanisms and the grain refinement in and around the interface. Because our findings are based only on small particle simulations allowable in MD, size effects can preclude extrapolating the results to physical micron-sized particles used in actual cold spray.