Rockwell, Vickers, & Brinell Hardness Test and Procedures
An indenter, sufficiently hard so as not to be deformed, is punched into the metal to be tested using a determined force. After the force has been removed, the dimension or the depth of the indent left in the material tested is measured.
The various hardness scales are differentiated by the nature and form of the indenter and by the method in which the width or depth of the residual indentation is measured.
Rockwell Hardness Test (ISO 6508)
The Rockwell hardness procedure consists of punching an indenter (cone or ball type) twice with force, in the conventional condition defined as follows, and measuring the residual increase in depth (e) of the indentation made by the indenter. The unit of measure (e) is equal to 0,002 mm. The value called Rockwell hardness is found from this increase.
Brinell Hardness Test (EN ISO 6506)
The Brinell hardness procedure consists of imprinting a steel ball of diameter D, with load F, on the piece to be examined and measuring the diameter d of the imprint left on the surface, after the load has been removed.
The Brinell HB hardness is a value equal to a quotient of the test load F of the imprint (expressed in kg f) for the area (in mm2), considered to be a segment of a sphere, with the ball diameter D.
Vickers Hardness Test (EN ISO 6507)
The Vickers hardness procedure consists of punching into the piece to be tested, using a determined force, a pyramid shaped indenter with a square base, having an angle of 136° to the summit and in measuring the diagonal (d) of the indent left in the piece, after having removed the load.
The Vickers hardness is the quotient of the test load(F in kg f) for the area of the indent (in mm), considered to be an upside down pyramid with a square base.