Measurement methods for quantifying powder flowability and velocity in cold spray systems

Four powders with varying bulk densities, Al, Al2O3, Sn, and Cu, were used to determine quantifiable relationships between powder flowability, mass flow rate, and powder velocity with particle morphology and particle distribution in a cold spray system. High particle density results in good powder flowability, specifically when the powders are spherical relative to irregular morphology. Particle velocity during cold spray, measured with a double disk rotary system, increases non-linearly with an increase of inlet pressure. The increase in mass flow rate from the hopper and the resulting mass output of the cold spray system shows a consequence of good powder flowability. Conversely, a high mass flow rate decreases the particle velocity during the cold spray process, with better flowability leading to decreases on the order of 10% in particle velocity in the cold spray system. The described methods, proposed tools, and findings can be easily made with cost-effective and on-the-spot measurements.