On the reliability of the measurements of mechanical properties of superhard coatings

Conditions which have to be satisfied in order to assure the reliability of the measurements of mechanical properties of superhard coatings are briefly summarized with references to earlier papers which provide insight into the relevant problems of fracture physics. It is shown that our published data on coatings with hardness in the range of 100 GPa have been, in contrast to the statement of Musil et al. (Mater. Sci. Eng. (in press)) done in the load independent regime and carefully verified by comparison with the Vickers hardness calculated from the size of the remaining indentation measured by SEM. The self-consistency of the measured mechanical properties was demonstrated by the analysis of the measured indentation curves in terms of Hertzian indentation theory.