Analysis of nanoindentation tests on SiC-based ceramics

Two silicon carbide-based ceramics, with very different mean grain size, and a standard fused silica sample were characterized by nanoindentation. The values of hardness and Young's modulus were measured at several peak loads and calculated using the models developed by Oliver and Pharr (O&P) and by Cheng et al. (C&C). For all the materials, the values of hardness and Young's modulus were strongly dependent on the adopted model. In the silica specimen, the C&C Young's modulus and hardness were lower than those calculated by the O&P model. In the SiC ceramics, the differences between the two models were both qualitative and quantitative. The C&C Young's modulus values were lower than those calculated by the O&P model but the hardness values were higher. For most of the peak loads, the O&P model distinguished between the two SiC specimens while the C&C model did not.