Hardness Testing

metal hardness testing

Why Measure for Hardness?

Hardness testing measures the resistance of metals to plastic deformation by indentation. The table below lists the various tests, the indentor type, and the method of measurement.

Carbon steels and low Alloy steels show a good correlation between hardness and ultimate tensile strength. Hardness is a good indication of consistency and when correlated with the composition and heat treatment of cast ferrous and nonferrous Alloys it is a handy measure of the control and acceptability of castings. The low cost and simplicity of this kind of test leads to their use for a number of quality control applications.

Methods to Test Hardness

ASTM test methods are ASTM E 10 for Brinell hardness, ASTM E 18 for Rockwell hardness, and ASTM E 384 for Microindentional testing.

Brinell hardness10 mm tungsten carbide ballIndentation diameter
ASTM E 10 Rockwell Hardness1/16” or 1/8” steel ballPenetration depth
Diamond pyramidconical brale diamond indentorAve. indentation diagonals
Vickers Hardnessdiamond pyramidAve. indentation diagonals
Knoop Hardnesselongated diamond pyramidAve. indentation diagonals