Micro- and Ultramicrohardness Measurements in SEM

Hardness measurements at very low loads ( greater 2 N ) enable the measurement of the hardness of extremely thin layers, of hardness profiles of e.g. case hardened steels, of the hardness of small particles, inclusions and phases and of the influence of a surface treatment (e.g. polishing) on the properties of this surface. For the measurements a device, that can be operated inside the specimen chamber, was used. This allows an exact placement of the indentations and also the measurement of the indentation diameters with high accuracy. In the microhardness region the measured hardness is dependent on the load (Indentation size effect). Different theories try to explain this dependence by friction of the specimen tip, tip roundness in case of Vickers pyramids, type and number of dislocations, surface tension, ... But no definite theory does exist. Microhardness measurements are also interesting in mineralogy to measure the hardness of small inclusions and phases. By use of standard minerals of well-known hardness, interpolation for the hardness of unknowns seems often possible with sufficient accuracy. Small loads are often also necessary to avoid the formation of cracks.