Introduction of fractal dimension to adhesive strength evaluation of plasma-sprayed coatings

The adhesive strength of ceramic coatings depends on the surface roughness of substrates. Taking account of the bonding mechanisms, however, surface roughness may not be a proper measure to evaluate the surface topography of substrates. Here, fractal dimension is proposed for the evaluation of surface topography. Physically the fractal dimension can include hook-shaped indentations which generate a mechanical interlocking force. By applying fractal dimension to the evaluation of the surface topography of substrates and relating it to the adhesive strength of alumina coatings, it was concluded that fractal dimension properly evaluates the adhesive strength as compared with surface roughness.