Hardness tests are non-destructive testing carried out in structural investigations, when it is important to identify possible alterations of the piece metallurgical structure.
There are many definitions of hardness: physically, hardness can be described as the resistance to the elastic-plastic deformation; in practice, it is usually defined as the resistance that a material opposes to penetration.
In pure metals hardness increases with the cohesion and the density of atoms.
In alloys hardness increases with the work hardening and the amount of residual stress and it depends on the metallurgical state of supplying.
Hardness tests have several advantages:
- They are rather quick and simple;
- They do not prejudice the running of the component;
- From the results it is possible to calculate indirectly other mechanical characteristics of the examined material.
Metalprove S.r.l. is able to perform hardness measurements on the surfaces of metallic items by means of portable equipment. The test is typically applied to welds, especially when the evaluation of the heat input effect on HAZ is required or when the result of a heat treatment has to be verified.