Principles of hardness testing

Categorisation of hardness testing by load range

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Depending on the field of application, different main loads (test loads) are used during hardness testing. Depending on the level of the main load applied to a test workpiece during the hardness test, a distinction is made between micro, small load and macro hardness testing in the ISO standard.

In the macro range (conventional hardness range), large test loads ≥ 5 kgf are used which result in correspondingly large hardness impressions in the test workpieces. The macro hardness testing methods include Brinell, Vickers and Rockwell.

A hardness test in the low-load range is one in which the test load lies between 0.2 kgf and 5 kgf (test load ≥ 0.2 kgf and < 5 kgf). The most common low-load testing method is Vickers. Low-load hardness testing is used predominantly for testing small parts, thick coatings and materials with a low hardness. < 5 kgf).

During micro hardness testing, low test loads < 0.2 kgf are used, which only leave very small indents in the test pieces (most common method: Vickers). Micro hardness testing can therefore be used to test the hardness of thin layers or, e.g., the hardness of individual crystallites or inclusions.

Categorisation of the hardness testing by load ranges