ESTIMATION OF YOUNG MODULUS AND OF HARDNESS BY ULTRA-LOW LOAD HARDNESS TESTS WITH A VICKERS INDENTER

The evaluation of the elastic-plastic proper-ties of a material by usi ng an ultra-low load hardness test requires a geometrical calibration that must take into account the imperfect form of the diamond indenter . In the present work, the Vickers indenter offset of the microindenta tion equipment was estimated using differently heat-treated steel samp les. To this end, the dimensions of the indentations have been evaluat ed by two different methods: optical measurement of the diagonals and direct measurement of the penetration depth during the test. The elast ic-plastic properties are then calculated from the analysis of the pen etration depth/indentation load curves. The Young's modulus values det ermined for the different high-speed steel samples were very similar a nd close to the literature value for steel if the appropriate correcti ons are performed. The hardness values decrease when the determination procedure includes the geometrical correction of the indenter offset, and still further when using the total correction obtained by means o f optical measurements of the indenter diagonal. Variation of the hard ness values with the applied load is much less when the corrections ar e carried out.