Investigation of Particle Dynamics in a Low-Pressure Cold Spray Additive Manufacturing Process*

Cold spray (CS) additive manufacturing is a solid-state deposition process for repairing and fabricating components in aerospace, medical, and other critical fields. It uses converging-diverging (CD) nozzles to accelerate particles to high velocities, depositing them onto a substrate. This study investigates the particle dynamics in a low-pressure CS system. Lower particle velocity in low-pressure CS systems generally leads to poor quality deposits. Reduced drag on the particles within the boundary layer results in non-uniform and slower particle velocities, thereby lowering the deposition quality. Proper mixing of the particles, facilitated by turbulence inside the nozzle, can address this challenge. A large-eddy simulation model combined with a discrete phase model (DPM) is used to perform the flow and particle simulations. An improved particle drag model has been developed and is used to track the dynamics of irregularly shaped particles in the flow stream. Simultaneously, measurements are conducted in an in-house developed cold spray research facility. Results show that flow turbulence significantly increases particle dispersion for this particular system.