ASTM E384 Microindentation Hardness of Materials

Scope:

Material Microindentation Hardness ASTM E384 is a method for assessing a material’s hardness on a microscopic level. The test method also provides error analysis that can occur during microindentation testing. Microindentation hardness is a measure of machinability, wear resistance, toughness, and ductility in metals.

Test Procedure:

For ASTM E384, a Knoop or Vickers indenter made from diamond is impressed into the test specimen at loads from a few grams to 1 kilogram. The impression length is measured microscopically, and the test load is used to calculate a hardness value. The hardness values obtained in ASTM E384 tests are useful indicators of a material’s properties and expected service behavior. The tester then applies the selected test load using dead weights. The length of the hardness impressions is precisely measured with a light microscope using either a filar eyepiece or a video image and computer software. A hardness number is then calculated using the test load, the impression length, and a shape factor for the indenter type used for the test.

 Specimen size:

The ASTM E384 test should be performed on a flat test specimen with a polished or suitably prepared surface for optimum accuracy of measurement.

For making an accurate measurement of the size of the indentation the test specimen surface should not be etched.

Data:

Knoop hardness (HK) in ASTM E384 testing is calculated as :

HK = 14.229 (F/D² )
where,
F = the applied load (measured in kilograms-force)
D² = the area of the indentation (measured in square millimeters)

Vickers hardness (HV) is calculated as :

HV = 1.854 (F/D² )
where,
F = the applied load (measured in kilograms-force)
D² = the area of the indentation (measured in square millimeters)

Conclusion :

ASTM E384 test method covers the determination of the microindentation hardness of materials.