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ASTM E 384 Standard Test Method for Microindentation Hardness of Materials
This specification covers both the Knoop and Vickers Hardness Tests when conducted using test forces in the 1 to 1000 gf. range. While this test method is primarily designed for metals, it may be used on other materials as well. With the Vickers Hardness Test a diamond with an apical angle of 136° is used. While the Knoops Hardness Test employs a narrow rhombus shaped diamond indenter.
Hardness Testing is very useful for quality control of manufacturing processes, materials evaluation, and for research and development purposes. Although hardness is empirical in nature, it is an indication of ductility and resistance to wear. Hardness may also be shown to correlate to tensile strength in many metals.
The Microindentation Hardness Test (commonly referred to as a micro hardness test) extends hardness testing to materials too thin or too small to use macroindentation test methods. Micro hardness testing can be applied to specific phases or constituents, gradients or region too small for the larger hardness tests.
Because of hardness variations that may exist in a material, a single micro hardness test may not be representative of over all hardness.
In these tests, a hardness number (either Vickers or Knoop depending on which indenter is used) is determined by measuring accurately with the aide of a microscope, a very small indentation produced by the application of a relatively low force (compared to the regular hardness test). The measurements now obtained, are then plugged into the appropriate formula, or cross referenced with the proper charts and a hardness number is obtained.
Complete specifications for ASTM E 384 may be obtained from ASTM International.