Flattening Behaviour and Cohesion Strength of Molten Metal Particle Impacted onto High-Temperature Substrate

Abstract

In a thermal spraying process, a lot of molten powders are impinged continuously onto a substrate due to a high-temperature plasma flow, and the coating is deposited consequentially. Thus, powder size, powder material, powder velocity, powder temperature and substrate temperature as the process parameter affect the mechanical properties and adhesion of coating. The understanding of fundamental physical principle for the spread and solidification of splat is essential to determine the relation between the coating properties and the process parameter. Relatively few experimental studies have been done to examine about a molten metal droplet impact. The simple model had been also developed to estimate quantitatively the flattening of a splat. However, there are no papers for the splat cohesion property, in spite of an essential one in characterizing the coating adhesion. In this study, the splat cohesion property for molten metal particle (Sn 60%-Pb 40%) dropped onto the substrate (SUS304 stainless steel plate) is examined based on a free fall experimental procedure, which could be simply simulate a powder deposition process in a thermal spraying. Influence of kinetic energy of the impact droplet and the substrate temperature on the flattening of splat and the cohesion is shown. The splat cohesion strength will be tried to estimate based on an energy balance consideration.