CFD Simulations of Feeder Tube Pressure Oscillations and Prediction of Clogging in Cold Spray Nozzles

Abstract

Cold spray is an additive manufacturing method in which powder particles are accelerated through a supersonic nozzle and impinged into a nearby substrate. This method produces deposits with advantageous attributes, namely with low porosity and low residual stresses, which nearly match those of the bulk material. One challenge with cold spray is nozzle clogging, which occurs when particles bond to the inside of the nozzle, altering the cross-sectional area, increasing roughness on the nozzle inner surface, and causing a drop in the gas velocity, ultimately resulting in a lower quality deposit. Clogging puts certain combinations of materials and operational parameters out of practical reach. A CFD model of the cold spray nozzle is developed to study the flow of metal particles in the cold spray process, and we determine that the two-phase particle-laden flow from the feeder tube is inherently transient. CFD simulations demonstrate that pressure fluctuations in the particle feed system can cause the particles to disperse in the nozzle and ultimately lead to some particles bonding with the nozzle wall. The degree of clogging is found to be strongly dependent on the amplitude of these upstream pressure fluctuations and seemingly independent of the pressure oscillation frequency.