Investigations of new possibilities in the calibration of diamond hardness indenters geometry

The influence of Rockwell and Vickers diamond indenters geometry in hardness measurements justifies the strict specifications and tolerances in the relative standards. Many methods, and consequently dedicated instruments, have been developed to investigate the geometrical parameters in order to calibrate the diamond indenters. Most of them, using contact or contactless methods, can only investigate some profiles of the indenters; from these partial measurements the whole geometry is derived. Few other instruments can investigate the whole shape but, since they are custom-developed, costs and difficulties in the calibration of these instruments have limited their use. A new method is proposed in this paper using a commercial and not dedicated instrument: a 3D measuring confocal microscope. This type of instrument has also the advantage that the whole geometry is analysed with a consequently knowledge improvement in the indenter calibration. In the paper the measurement method, the used instrument and its calibration to assure traceability to the length and angle standards are investigated.