Jetting Phenomenon in High Velocity Impacts of Solid Metallic Particles — A Molecular Dynamic Study

Cold Spray (CS) is a solid-state deposition process, in which solid particles are accelerated towards a substrate to high velocities at temperature as low as room temperature. In CS, the high velocity impacts of particles at low temperature result in severe plastic deformation at high strain rates, i.e., up to 10⁹ s^-1.

Numerous studies have been shown that when metallic particles impact substrates at high enough velocities, material ejection at the periphery of the particle/substrate occurs, which called “jetting”. However, the nature of this phenomenon and its significance in particle deposition is still unclear. In CS, in-situ observation of material behavior during the impact is very challenging since the particle deformation occurs over a very short time, i.e., tens of nanoseconds. Therefore, numerical methods have been used as an alternative to experimental studies.

In this study, Molecular Dynamics method, which has been shown to be a powerful tool to investigate the process physics and plasticity mechanisms, is performed to reveal the material behavior and the formation of jetting upon the impact. A copper particle with 0.2 um diameter is modeled. The particle size is expected to be large enough to capture a similar behavior experienced with real particles in CS.