Abstract
A freely falling experiment, in which a molten metal droplet fell freely and impinged on a flat substrate, was conducted as a simulation of the thermal spray process. The relating factors to the flattening and solidification behavior of the droplet were explored and their effects were clarified.
A flattening ratio ; D/d has been introduced into consideration and used as an estimation factor of the flattening degree of the splat. It was found in our experiments that the larger Re and We numbers of the splat were, the higher the flattening ratio was. Comparing with the flattening ratio of the conventional Madejski's equation, that obtained in the experiment was fairly small. This suggests that some other factors relating to the actual flattening, for example surface tension, solidification and wetting at splat/substrate interface, have to be taken into account to the analyses. Further investigation results showed that both interface wetting and thermal conductivity of the substrate affected the flattening ratio of the splat. The observation results of the bottom surface of the splat indicated that the solidification affected the flattening behavior of the splat, especially in the central region.
