Droplet impact on heated powder bed

The impact of droplets on a heated powder bed involves a wide range of phenomena with increasing complexity from spreading of liquid, to bubble nucleation, to more complex ones such as splashing, crater formation, and fluidization. In this study, we focus on the impact behaviors caused by elevation in temperature of the powder bed. We experimentally characterize the impact behaviors for wide ranges of the impact velocity and surface temperature of the powder bed. We reveal several phenomena specific to the impact on a heated powder bed such as rebound, ruptures of expanding liquid films, bubble nucleation, and fluidization. We also show that the maximum spreading diameter increases with the surface temperature of the powder bed and propose an empirical scaling law to describe such a relation.