In the Vickers hardness test [7] a diamond indenter, in the form of a square-based pyramid with an angle of 136º between the opposite faces at the vertex, is pressed into the surface of the test piece using a prescribed force F (N) and, after the force has been removed, the diagonal lengths of the indentation d1 (mm) and d2 (mm) are measured. The time for the initial application of the force is 2 s to 8 s, and the test force is maintained for 10 s to 15 s. The Vickers hardness value is proportional to the test force divided by the surface area of the indentation:

HV = Constant × Test force / Surface area of indentation

where: d = arithmetic mean, in mm, of the two diagonal lengths d1 and d2

Table 1 provides a list of the Vickers hardness standard scales.

Table 1. Vickers hardness scales