A POROSITY FORMATION AND FLATTENING MODEL OF AN IMPINGING MOLTEN PARTICLE IN THERMAL SPRAY COATINGS

Thermal spray coatings have porosity; however, reasons for the production of porosity during the coating process are not known. This paper proposes a physical and mathematical model for the production of porosity by considering deformation of a molten particle during thermal spray coating processes. The theoretical model shows that the impinging velocity, the ambient gas pressure, the particle diameter, and the molten material viscosity contribute to producing porosity. This paper also proposes that there is a porosity distribution along the splat radius and that most of the porosity exists in the periphery of the splat. Also, a flattening model proposed in this work agrees well with the results of Engel (Ref 1).