Effect of particle oxidation, size and material on deformation, bonding and deposition during cold spray: a peridynamic investigation

Abstract: Cold spray (CS) has emerged as an important additive manufacturing technology over the past decade. This study investigates the effect of oxide layers on the CS process, focusing on the deformation behavior of copper (Cu) and iron (Fe) particles upon collision with a matching substrate. Using a peridynamics-based approach, we examine the effects of oxide thickness, particle size, and particle/substrate material on material deformation and oxide fracture processes. Our results show that thicker oxide films restrict particle deformation, delay oxide discontinuities and material jetting, and increase the critical velocity required for metal to metal contact. Larger particles, despite uniform deformation across sizes, require lower velocities to initiate jetting and oxide separation because of their higher kinetic energy, leading to metallurgical bonding at lower velocities. Soft to soft impacts induce oxide film cracking at lower velocities, resulting in larger interface areas and more oxide-free contact zones, thereby reducing the critical velocity. Furthermore, the volume of residual oxide has a power-law relationship with the particle size, indicating that the oxide-cleaning ability of the particles affects the critical velocity. This study highlights the importance of oxide deformation and fracture during CS processes and provides valuable insights into the breakage and removal of oxides and subsequent metallic bond formation. These findings offer beneficial new knowledge for the rational design and optimization of CS processes.