Influence of substrate deformation on formation of splats during thermal spraying

摘要

Dynamics of the coating formation and particularly the characteristics of flattening of the droplets impinging onto a substrate surface or onto a surface of the previously deposited layers affect markedly the properties of the coatings produced by thermal spraying [1-3]. Generation of the high pressure at the impact zone during droplet flattening is an important factor for the development of the substrate-coating bonding and the coating porosity [4-7]. Kinetics of the droplet flattening upon impact and the substrate-coating mechanical interaction have been studied in a number of papers taking into account the morphology of the substrate surface, solidification of the lower part of the splat, spraying angle, etc. [8-11]. Due to high kinetic energy of an impinging droplet a strong elastic deformation of the substrate and the formation of its curvature occur which influence the dynamics of the droplet flattening (particularly the thickness and the diameter of a splat) and a pressure formed upon the droplet impact. This paper involves investigation of these phenomena and the development of the simple analytical formulae needed by the engineering practice which enables to estimate the influence of the substrate deformation on the droplet flattening and the high pressure generation.