LAUSR

Abstract Thermally sprayed coatings are manufactured by molten or semi-molten droplets impinging onto the target substrate. The properties of coatings created (porosity, conductivity, cracks, ...) depend largely on the dynamics of the droplets which is an outcome of joint aspects, such as properties of liquid droplet and surface wettability. The present work investigates the normal impact of liquid droplets (molten ceramic or metallic droplets) onto dry solid surfaces of various wetting properties. Use is made of the Volume-Of-Fluid (VOF) interface tracking method with a single set of mass and momentum conservation equations. The wettability of a solid surface, characterised by a contact angle, is taken as part of the boundary conditions in the Smooth VOF algorithm. Introducing the dimensionless time t* = tV 0/D0 for a droplet with the initial speed V 0 and initial diameter D0, its spread factor ξ (= D/D0) is found to be proportional to the square root of t* when 0.2 t * ≥ 0.5 W e .