The flattening of droplet impacting on a substrate is one of the most important basic processes during the formation of a thermal spray coating. The structure of splat will determine the structure of coating, and consequently the adhesion and properties of coating. This paper investigates the dependency of the change of the morphologies of splats from irregularly complicated form to regular disk form by the preheating of substrate on the types of evaporable substances adsorbed on substrate surface in order to provide farther evidence for the evaporated gas induced splashing mechanism. Paper includes a German-language abstract.