The Dynamics of Deposit Formation in Thermal-Spray Processes

Abstract

In thermal spraying, coatings are formed by particles flattening and piling up on the substrate. At impact, the sudden deceleration of the particle causes a pressure buildup at the particle-surface interface; the high pressure inside the particle forces melted material to flow laterally and ductile material to deform. The particle spreads outward from the point of impact and forms a “splat.” The arresting of spreading results from the conversion of particle kinetic energy into work of viscous deformation and surface energy. Solidification constraint (when the solidification front is advancing from the substrate surface fast enough to interact with the liquid during spreading) and mechanical constraint (due to the roughness of the substrate surface) can interfere with the flattening process.