Vickers hardness test

What is it?

By definition, hardness is the ability of a material to resist irreversible deformation when an external force is applied. Scientifically speaking, it is the resistance of the material to plastic deformation by loading. As an intrinsic property of a material, it can be expressed as nanohardness, microhardness, hardness or macrohardness as a function of the applied load.
Hardness measurement is accomplished by pressing a body, called an indenter, onto the material using a force (F). The geometry and the indenter material are factored into hardness measurements.
The figure below represents the hardness measuring equipment.

What is it used for?

Microhardness test measure the indentation resistance of the material to plastic deformation. Microhardness may also be used to infer the wear resistance, mechanical properties using correlation tables and, ultimately, control the quality of thermal treatment or joining processes and as a quality check for plastic formation.

Equipment and working conditions

The equipment used for the hardness testing is a Shimadzu HMV-2 using a square-based pyramidal diamond indenter. The pyramidal indenter is built in such a way that opposing faces meet at the apex at 136º, which relates to the Vickers method.
The test conditions vary from test to test and are related to the specimen. This equipment has a load that can vary between 98.07mN and 19,614N, corresponding to a load from 10g to 2kg.
The Vickers hardness, HV, is established by the ratio of the load applied, F, in kgf, perpendicularly to the surface of the specimen by the contact area of the indented zone. Measuring the diagonals, d, of the indented zone, it is possible to compute the indentation area in mm2 and the hardness as follows: (Kg/mm2)

Example of use

- Cross section evaluation of hardness in materials for identification of different layers
- Hardness evaluation of different phases or components of a material
- Depth analysis of surface nitriding/cementation