On the implementation of the fractal concept to quantify thermal spray deposit surface characteristics

A methodology is suggested to accurately describe the surface state of thermally sprayed coatings, which is mostly related to the process operating conditions and to the feedstock characteristics. Up to now, standard methodologies and their related descriptors are not sufficient to give simultaneously global and local information about deposit roughness. An approach is proposed, taking into account the multi-scale complexity of the profile. This approach is based on a description of the surface in terms of fractal geometry. Several aspects of the fractal methodology are discussed and some results related to the substrates and upper surface deposit profiles are presented. Comparisons with conventional methodologies do not permit a direct correlation: the fractal methodology proves to be sensitive to the measurement scale and to the calculation protocol.