Dear Rajesha Kumar S
The microhardness test is associated with penetrations made by an indenter using loads less than 1kgf. Depending on the type of indenter (diamond pyramid, cone, etc.) you will have Vickers, Brinell, Rockwell, Knoop, etc. hardness.
There is a good number use of hardeness testing examples in
www.sciencedirect.com/topics/engineering/vickers-hardness-testing
Dear Rajesha,
The microhardness deals with the surface indentation of less than 1Kgf of load, whereas the macrohardness uses a load of more than 1Kgf of load. Moreover, in microhardness, one can control the indentation dimensions in the micron range and therefore, the hardness of a particular phase can be analyzed in the given material, which could not be possible through the macrohardness testing process.
There is no specific difference between micro and macro hardness, other than that mentioned above. therefore, the conversion table used to convert the macrohardness into MPa can also be used to convert the microhardness values into MPa.
Dear Researchers,
When two solids are pressed together, the contacting asperities will deform and originate small spots of solid-to-solid contact. The crucial parameter that controls the plastic deformation of the contacting asperities is the surface contact microhardness.
Effective microhardness is significantly greater than the bulk hardness. The microhardness decreases with increasing the depth of indenter until bulk hardness is obtained. This increase in the plastic yield stress (microhardness) of the metals near the free surface is a result of local extreme work hardening or some strengthening mechanism during surface preparation. The bulk hardness tests employ relatively large indentation loads, and therefore the indenter penetrates very deep into the surface.
An explicit relation to calculate microhardness is available in following link:
Ref: http://www.mhtlab.uwaterloo.ca/pdf_papers/mhtl88-8.pdf
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