The main objective of this research is to evaluate the dynamic wetting of the substrate by thermally sprayed particles through direct observation on the freely fallen metallic droplets onto the substrate surface. Compared to normal static wetting, dynamic wetting can be characterized as the wetting phenomenon in which both material movement inside the splat and heat transfer from the splat into the substrate occur simultaneously. As the phenomenon is so complicated, there is a lack of an appropriate evaluation manner. In this study, the wetting behavior of freely fallen metallic droplets was systematically observed onto several kinds of substrate materials. Actually, concrete measurement values on the wetting angle of the droplets with an increasing of the substrate temperature were measured. It was found from the results that even the dynamic contact angle changed transitionally with an increase of the substrate temperature and corresponded well with the changing tendency in the disk splat fraction ratio of the thermally sprayed particle onto the substrate. From the result, it was confirmed that the flattening of thermal sprayed particles is essentially dominated by the dynamic wetting of the substrate by them.

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