4. Hardness test

Hardness and microhardness tests are widely used to characterize welded joints. There are two techniques that can be used on this type of assembly: the Brinell test and the Vickers test. Both hardness and micro-hardness tests are governed by test method standards: NF EN ISO 6506-1 and NF EN ISO 6507-1 for the Brinell and Vickers tests respectively. The Vickers method is the most widely used in welding.

The Vickers method consists in applying a diamond indenter with a pyramidal shape and square base to the area to be tested. The angle at the top of the pyramid is 136 for a given time (5 to 15 s) and under a given load (see below). Hardness is then measured by measuring the size of the indentation (diagonal measurement) left by the indenter. For this Vickers method, it is also important to differentiate between hardness and microhardness measurements. The difference...