Analysis of the indentation size effect in the microhardness measurement of some cobalt-based alloys

The load dependence of the Vickers microhardness of some cobalt-based alloys subjected to heat treatment at different temperatures for various duration has been investigated using Hanemann’s method and a PMT-3 hardness tester. It is found that even for the same sample Hanemann’s method shows a decrease in microhardness with applied load (i.e., normal indentation size effect) while the PMT-3 hardness testing exhibits a reverse effect. The experimental data were analysed using Meyer’s law, Hays–Kendall’s model, the elastic/plastic deformation model of Bull et al., the proportional specimen resistance model of Li and Bradt and the energy balance approach of Bu¨ckle. The analysis of the experimental data revealed that: (1) the Meyer hardness index n decreases linearly with logarithm of the so-called standardised hardness constant A, (2) within the limits of experimental errors, the load-independent microhardness of a given sample predicted by the other models used is constant, (3) the quantities contributing to the load dependence of hardness are inversely related with the constants describing the load-independent hardness, (4) the quantities contributing to the load dependence of hardness are related with the Meyer hardness index n and (5) the constants of the energy balance approach are mutually related but the load-independent microhardness predicted by this approach is erratic with respect to that obtained by the other models. [Copyright &y& Elsevier]