Rockwell Hardness Testers is based on the measure of the net indentation depth increase when a load is applied.
The test is performed by pressing an indenter with a pre-load that causes an initial penetration, by setting the zero point on the tester and then by applying the full-load.
Removing the full-load gives the result value that is referred to the indentation depth.
Different types of indenters are used: 120° diamond spheroconical, 3.175mm and 1.588mm spheres.
This test is widely used due to its speed, resolution, reliability and small indentation area.
Superficial Rockwell tests uses low loads on thin samples and, depending on the indenter, can be performed from ceramic to metal sheets.
The hardness values are expressed with dimensionless numbers, the most commonly used scales are the C and B.
There are several alternative scales A, B, C, D, E, F, G and others.
Superficial Rockwell scales are expressed as 15, 30 and 45 followed by N, T, W, X and Y depending on the used indenter.