Vickers Hardness

The Vickers hardness test uses a 136° square pyramid diamond indenter pressed into the material under a selectable test force. After removal of the force, the lengths of the two impression diagonals are measured under an optical microscope (or automated image analysis) and averaged to obtain d. Because the impression geometry is self-similar, Vickers hardness is comparable across a wide force range, from macro loads to microhardness conditions.

HV is particularly valuable for thin sections, welds, case-hardened layers, and coatings, where Rockwell might violate minimum thickness rules. Low-force Vickers (often called microhardness when combined with small loads) maps hardness gradients across microstructures and identifies soft or brittle zones.

Surface preparation strongly affects diagonal measurement: excessive deformation during polishing rounds impression corners and biases HV low. Specimens should be flat, perpendicular to the indenter axis, and rigidly supported. For anisotropic materials, diagonal asymmetry may reflect crystallographic orientation rather than machine error.

Modern systems use motorized turrets, automatic focusing, and edge-detection algorithms to reduce operator variability. Verification uses reference blocks and indirect checks of indenter geometry and measuring system resolution per ISO 6507-1; ASTM E384 adds guidance for microindentation force ranges and environmental controls.