Indentation hardness
Hardness measurements quantify the resistance of a material to plastic deformation. Indentation hardness tests compose the majority of processes used to determine material hardness, and can be divided into two classes: "microindentation" and "macroindentation" tests. Microindentation tests typically have forces less than . Hardness, however, cannot be considered to be a fundamental material property. Classical hardness testing usually creates a number which can be used to provide a relative idea of material properties. As such, hardness can only offer a comparative idea of the material's resistance to plastic deformation since different hardness techniques have different scales.
Vickers hardness test
If HV is expressed in kgf/mm then the tensile strength (in MPa) of the material can be approximated as ≈ HV× ≈ HV/0.3, where is a constant determined by yield strength, Poisson's ratio, work-hardening exponent and geometrical factors - usually ranging between 2 and 4.. In other words, if HV is expressed in N/mm (i.e. in MPa) then the tensile strength (in MPa) ≈ HV/3. However it should be noted this empirical law depends variably on the work-hardening behavior of the material.