Abstract

It is widely recognized that substrate surface roughness, or topography, plays an important role in droplet-substrate interaction and the adhesion of sprayed coatings. A key difficulty in understanding the role that topography plays during droplet impact, wetting and solidification has been the availability of methods for appropriate characterization of the topography. The complex nature of the substrate topographies cannot be adequately characterized by conventional methods such as Ra. In this work, scale-sensitive fractal analyses are considered for advancing the understanding of roughness of grit blasted surfaces in thermal spray applications. Area-scale analysis is performed on 3D data sets acquired from different grit-blasted substrates. 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 to guide experimental design for topographical data acquisition and analysis and to better understand the influence of grit blasting on substrates for thermal spray. The potential of these scale-sensitive analysis techniques to fulfill the above bases for supporting statistical correlations and clear physical interpretations is discussed.

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