Evaluation of DLC, WC/C, and TiN Coatings on Martensitic Stainless Steel and Yttria-Stabilized Tetragonal Zirconia Polycrystal Substrates for Reusable Surgical Scalpels
Table 1
Definition of the surface parameters evaluated for the morphological analysis of the specimen surfaces (ISO/FDIS 25178-2:2012).
Symbol
Parameter
Definition
Sa
Arithmetic mean height
Sa measures the dispersion of heights with respect to the mean surface height. The higher Sa, the rougher the surface.
Sq
Root-mean-square height of the scale-limited surface
Sq measures the dispersion of heights with respect to the mean surface height. The higher Sq, the rougher the surface (more sensible than Sa).
Ssk
Skewness of the scale-limited surface
Ssk measures the symmetry of the surface height distribution curve with respect to its mean value. It is 0 for a symmetric height distribution (e.g. Gaussian) and ≠0 for an asymmetric distribution. It is >0 if most heights are below the mean but are counterbalanced by a few regions high above it (hills/peaks); it is <0 if most heights are above the mean but are counterbalanced by a few regions well below it (dales/pits).
Sku
Kurtosis of the scale-limited surface
Sku measures the spikiness of the surface height distribution curve. It is 3 for a roughly Gaussian distribution, >3 for spikier distributions, <3 for flatter ones.
Sz
Maximum height of scale-limited surface
Sz represents the distance between the highest peak and the deepest pit in the profile.
Sk
Core height
Sk represents the core (or kernel) roughness of the surface over which a load may be distributed during most of the functional life of the surface. It is a measure of the nominal roughness and may be used to replace Ra and similar parameters. It is more robust of Ra especially when localized singularities (e.g., very high peaks or deep pits) may affect the outcome of the more traditional parameters.
