Vickers hardness
/ VIK-erz /
The Vickers test presses a small four-sided diamond pyramid into the surface and measures the diagonals of the neat square dent it leaves. Its great appeal is that ONE method and ONE scale cover everything from soft lead to the hardest tool steel and ceramics, because a diamond never flattens the way a steel ball can. Where Brinell and Rockwell each need a family of balls and scales, Vickers uses a single continuous scale for all materials.
A load, often between 1 and 100 kgf, presses the diamond in for a set dwell; the two diagonals of the square imprint are measured under a microscope and averaged, and the Vickers hardness (HV) is the load divided by the contact area of the indent, HV = 1.854 x F / d^2 with F in kgf and d in mm. Because the pyramid makes geometrically similar dents at any load, HV is nearly independent of the load used. Turn the load right down (a few grams to 1 kgf) and it becomes microhardness testing, able to probe a single tiny grain, a thin coating, or the hardened case on a gear tooth.
Vickers is the researcher's and metallurgist's favourite for its accuracy and huge range, and microhardness lets you map how hardness varies across a microstructure or through a case-hardened layer point by point. Its trade-off against Rockwell is speed: the dent must be measured optically, so each reading is slower and needs a flat, polished surface and some care. Like Brinell, its area-based number correlates with tensile strength, and it is the standard choice when one scale must span very soft and very hard materials alike.
To check a carburised gear, a metallurgist takes a row of tiny Vickers microhardness indents from the surface inward, plotting how hardness falls off with depth to confirm the hardened case is thick enough.
One diamond pyramid, one scale for everything — and at tiny loads it probes single grains or thin coatings.
Vickers uses one continuous scale across all hardnesses, but each reading is slower than Rockwell because the diagonals must be measured optically on a polished surface. At very low loads (microhardness) the result becomes sensitive to load and surface finish.