Abstract

For the adhesion of thermally sprayed coatings, the substrate roughness, or topography, plays an important role in droplet-substrate interaction. The lack of availability of methods for appropriate characterization of the real topography is a major difficulty in understanding the role that topography plays during droplet impact, wetting and solidification. The complex nature of the usually chaotic substrate topographies cannot be fully characterized by conventional roughness numbers such as Sa or Ra. In our study a scale-sensitive fractal analysis method is used for describing the morphology of grit blasted surfaces. Area-scale analyses are performed on 3D data sets acquired from different substrate materials, treated by various grit blast parameters. From fractal analysis it is known that the apparent area of a rough surface increases as the scale of observation decreases. The area-scale relations are used on one side to guide experimental design for topographical data acquisition and analysis, and on the other side to understand the influence of the grit blast process on the different kind of substrates. The potential of these scale-sensitive analysis techniques for supporting statistical correlations and clear physical interpretations will be discussed.

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