Variation of Nanoindentation Curve due to Wear of Indenter Apex and Its Correction Method

A force calibration of a nitridation and a 3a morphology observation of ind enters were carried out in this study. A microbalance calibrated with standard weights was used for measuring the loads generated by a nitridation. The indentation load could be calibrated from the ratio of measured and generated loads and the first contact load also could be detected from the microbalance data. By analyzing atomic force microscopy images of two indenters, curvature radii of apexes were determined by 19.71±3.03 and 1043.94±50.91 nm, respectively, for the nearly new indenter A and the severely worn indenter B. Corresponding bluntness depths were estimated by 1.22 and 64.56 nm for the both indenters by overlapping their profiles on the perfect pyramidal shape. In addition, nanoindentation curves obtained from a fused silica reference material with the both indenters showed a depth difference corresponding to the bluntness depth difference along the indentation depth axis. By shifting amounts of the bluntness depths along the horizontal axis, whole nanoindentation curves overlapped on themselves and resulted in nanohardness values consistent within 1.11 % without considering the complex indenter area function of each indenter.