Principles of hardness testing

History of hardness testing

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The most important dates in the history of hardness testing are as follows:

  • 1722: R. A. Réaumur develops a "scratching" of the surface of minerals using steel.
  • 1822: The Mohs scale for mineral testing is invented. This is a ten-point scratch hardness scale in which each material can be scratched using the next harder material. The Mohs hardness values are still used today in mineralogy, but are not suitable for determining the hardness of technical materials (metals). The individual hardness steps are relatively large and have different intervals.

 

Mohs hardness

Type of mineral

Vickers hardness (HV)

1

 Talcum

                       2HV

2

 Gypsum

                     35HV

3

 Calcite                    100HV

4

 Fluorspar                    200HV

5

 Apatite                    540HV

6

 Orthoclase                    800HV

7

 Quartz                 1.100HV

8

 Topaz                 1.400HV

9

 Corundum                 2.000HV

10

 Diamond               10.000HV

 

  • 1900: J. A. Brinell develops a ball indentation test that later becomes known as the Brinell method.
  • 1920: S. R. Rockwell develops the pre-load method named after him for testing his ships.
  • 1925: The Vickers method was invented by R. Smith and G. Sandland in England. It allows microhardness tests to be carried out.
  • 1939: F. Knoop, C. G. Peters and W. B. E. Emerson develop the Knoop method at the National Bureau of Standards (USA).