Determination of the shape of indenters for nanohardness testers via interferometry

A method for determination of the contact-area functions for diamond indenters of nanohardness testers using a metrological atomic-force microscope with three-coordinate laser interferometer is proposed. Face shapes of a number of indenters of Berkovich pyramid type are measured. The precision of the indenter surface coordinates measurement is 1 nm. It is demonstrated that the indenter tip shape changes in the course of its use; in particular, for the first 100 nm the deviation from the ideal pyramid can exceed 30 nm. Thus, one of the methods for verification of the contact-area function for an indenter is its periodic calibration using a metrological atomic-force microscope.