Application of a diamond spherical indentor with a large curvature for evaluating the hardness of very hard steel

Conclusions

It is possible to extend the hardness-number measuring method represented by (1) to very hard steel, which cannot be tested with a normal ball tip, by applying when necessary relatively small loads to diamond ball indentors with a large curvature. It is possible to lower considerably the maximum hardness for which the above technique is applicable by decreasing the angle at the vertex of the cone and the indentation force. Materials whose hardness is below the indicated limit should be tested with normal loads and ball diameters. Thus, it is possible by means of a ball probe and the new hardness number to evaluate the hardness of all steels, from the very soft to the very hard, and to obtain a hardness number read off the same scale. This property of the technique is of great practical importance [6].