Fig. (15) Average S_tr parameter values for the turned surfaces with and without HF treatment for both characterisation techniques. Both surfaces go from random to textured surfaces with increased filter size within the SEM range. For the AFM range, the chemically etched surface is classified as a random surface over the whole range while the untreated surface goes from the mixed zone to textured surface with increased filter size. ▲ = TS, ● = TS+HF. Unfilled symbols represent AFM data.