Microhardness Testing
Shimadzu Model HMV-M3

Microhardness testing, also called microindentation testing, uses smaller applied loads and is suitable for finer spatial scale hardness testing than either Rockwell or Brinell hardness testing. The test units are grams and micrometers, rather than kilograms and millimeters.

Practical applications of microhardness testing include determining depth of case hardening of machine parts, hardness testing of small or thin artifacts, and evaluation of material phases or constituents too small for Rockwell or Brinell hardness testing.

A Vickers (square-based pyramidal geometry) diamond indenter is employed to conduct Vickers microhardness testing with a Shimadzu Model HMV-M3 Micro Hardness Tester. Applied loads are 25 to 1,000 grams and the indentation diagonals are a few to a few hundreds of micrometers across. Indentation depths are related in size. The instrument optics are used to to visually measure the indentation size after the load is applied and removed automatically by the machine.

The hardness at a precise location may be evaluated and a change of hardness may be evaluated within a sub-millimeter distance, as the indentations are of that small size and the test specimen stage incorporates micrometers for fine 2D motion.

The Vickers Hardness Number HV is defined as Applied Load divided by Indentation Surface Area and is computed from the equation:

Vickers Indentation
Polished steel test block
Applied load 300g
Loading dwell time 5 seconds
Coarse and fine scale units micrometers


where

  • P is the applied load of up to 1,000g.
  • d is the mean diagonal length of the indentation in micrometers.

  • Applied loads of 25, 50, 100, 200, 300, 500, and 1,000g are available for the Shimadzu tester.
    The loading dwell period is selectable from 5, 10, 15, 30, or 45 seconds.

    Note: A Knoop (rhombic-based pyramidal geometry) diamond indenter could be employed, if available, for Knoop microhardness testing. The Knoop Hardness Number HK is determined differently from HV, due to the different Knoop indenter geometry and the Knoop Hardness Number HK basic definition as:

    Knoop Hardness Number HK = Applied Load divided by Projected Indentation Area (not a square).

    See ASTM Standard E384 for more information.

    Summary About the Micro Hardness Tester
    Manufacturer Shimadzu Scientific Instruments
    Tests Performed (Vickers) Micro Hardness
    Units in the Lab 1
    Locations in the Lab Area 1