Sharp tip geometry and its effect on hardness in nanoindentation experiments

Abstract

In this article, we used an indenter, sharper than a Berkovich indenter, consisting of a triangular pyramid with a face angle of 80°, and compared the difference between our own and the Berkovich indenters. First, the cross-sectional shapes of the indenters were analyzed by the Shih, Yang, and Li model [C. W. Shih, M. Yang, and J. C. M. Li, J. Mater. Res. 6, 2623 (1991)]. The result suggested that our sharp indenter has more deviation from the ideal triangular pyramid than the Berkovich indenter, resulting from the difference in sharpness of the indenters. Second, we determined an area function for our indenter using fused silica and compared it with those of an ideal triangular pyramid and a Berkovich indenter. There was a larger difference between the real and ideal indenters in our indenter than in the Berkovich case. Third, hardness measurements indicated that hardness increases with increases in depth and reaches a constant value in both cases of fused silica and single-crystal Si. This dependence of hardness on depth is explained herein in a qualitative manner.