Correcting Rockwell hardness values based on improved measurements of diamond indenters using a confocal laser scanning microscope

Adhering to the standards is unequivocally important to obtain meaningful Rockwell hardness test results. This entails the calibration of the indenter geometry and ensuring that its geometric properties lie within the permissible tolerances. This work presents the current measurement method and the procedure adopted by the Physikalisch-Technische Bundesanstalt (PTB) to calibrate the spherical tip radius of a Rockwell hardness diamond indenter along with a simple measurement uncertainty budget. Furthermore, it provides an insight into the available methods to correct the hardness deviations arising from deviations in indenter geometry.