Gas and ceramic particle velocities for micro-cold spray. (March 2023)

• Record Type: Journal Article
• Authors: Bierschenk, Stephen G.; Becker, Michael F.; Kovar, Desiderio
• Is Part Of: Journal of aerosol science. Volume 169(2022)
• Publication Date: 2023-03
• Subjects: Aerosols -- Periodicals; Aerosols -- Periodicals; Aérosols -- Périodiques; 541.34515
• DOI: 10.1016/j.jaerosci.2022.106113
• Languages: English
• ISSNs: 0021-8502

Abstract

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. Highlights: Variations in the gas flow profile showed a wide range of possible impact behavior for typically used powders and gases. Gas density beneath the nozzle increases linearly with inlet pressure which can result in significant particle deceleration. For particle diameters <200 nm or >1 μm, operating conditions produce impact velocities that too low for film formation. The effect of nozzle geometry, especially the diverging region, on impact velocity is notable for all particle diameters.