Hardness Test - Vickers hardness


Principle

 

Vertical indentation with a quadratic diamond pyramid. Measurement of the indentation diagonals d1 and d2.



Formulas

 

HV = 0.0102 · F · 1.8544 / d2 = 0.189 · F / d2 ... Vickers hardness
A = d2 / 2 · sin ( 136° / 2 ) = d2 / 1.8544 ... ... Surface area of the remaining impression
d ... Average of both diagonals d = (d1 + d2) / 2
F ... Test force [N]

Designation of Vickers hardness HV

Example: 640 HV 30/20
640 - Vickers hardness number
30 - Approximate kgf-value according to test force (with 30 kgf = 294.2 N)
20 - Duration time of test force (if not between 10 - 15 s)

Conditions
  • Vickers hardness tests are defined for diagonal lengths of indents between 0.02 mm and 1.4 mm
  • Presetting or recommendation of a particular test load
  • Vertical and shock-free appliance of the test load
  • The time until the test load has been reached must lie between 2-8 s, with small loads and micro hardness < 10 s
  • Approach speed of the indenter < 0.2 mm/s
  • The dwell time of the test load must lie between 10-15 s
  • The distance from the middle of a test indentation to the edge of the sample has to be at least 2.5 fold the diagnoal length (soft materials 3d).
  • The centers of two indentations have to be at least 3d apart (soft materials 6d).
  • Differences of more than 5 % between the diagonal lengths have to be indicated in the test report.

History

 

Vickers method has been developed by Smith and Sandland in 1925.
The decisive motivation came from flattening the Brinell steel ball, with which tests could be made up to a hardness of 450 HBS.

Valid standard

 

DIN EN ISO 6507:2005 1 - 4 Metallic materials - Vickers hardness test
Revision draft 2016 available
DIN ISO 4516:2002 Metallic and other inorganic coatings - Vickers and Knoop micro hardness tests

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