Normally, the surface of the specimen to be tested must be prepared for Brinell hardness testing, because the surface quality must be good enough to allow correct optical evaluation of the indent.
Compared with the Vickers method, which also tests hardness in the micro range, the surface quality requirements for the Brinell method are nevertheless lower, because the latter normally involves testing with higher loads (in the macro range) and larger indenters (balls), so the surface can be rough.
In detail, the specimen to be measured must meet the following requirements for the Brinell method:
- The specimen must be plane-parallel (clean separation of the specimen from the workpiece required during specimen preparation).
- The specimen to be tested must have a level, metallically bare and smooth surface (grinding and polishing of the specimen surface only necessary for tests with small ball diameters).
- The specimen must be fixed in a rigid mounting fixture, so that is cannot move during the testing process (practical tip: measure with the specimen clamped, or embedded or fixed in a specimen holder).