Gas and ceramic particle velocities for micro-cold spray
Stephen G. Bierschenk, Michael F. Becker, Desiderio Kovar
Abstract
The particle impact velocity is a critical parameter in assessing deformation and particle adhesion mechanisms that occur during the micro-cold spray process (also referred to as the aerosol deposition method or vacuum kinetic spraying) for depositing fine ceramic particles. In this study, the influence of operating parameters including inlet gas pressure, gas pressure ratios, gas type, and nozzle-to-substrate distance on gas velocities is studied. The gas velocities are then used to calculate maximum particle velocities, slowing that occurs as the particle travels through compressed gas near the substrate, and particle impact velocities. The drag laws used are appropriate for the full range of particles sizes used in micro-cold spray and related processes from 50 nm to 5 μm. The process parameters that maximize particle impact velocity for particles with a range of sizes and densities are delineated, and the influence of nozzle geometries is assessed.