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Chapter VIII Micro-hardness studies…
4. Cutting hardness
Sharp tool of a given geometry is caused to remove a chip of standard
dimensions.
5. Damping hardness
In this test, change in amplitude of a pendulum having hard pivot resting on
test surface is the measure of hardness. The Herbert pendulum test is of this
type.
6. Abrasion hardness
Specimen is loaded against a rotating disk and the rate of wear is taken as a
measure of hardness.
7. Erosion hardness
Sand or abrasive gram is caused to impinge upon the test surface under
standard conditions and loss of material in given time is taken as the measure
of hardness.
In the present chapter, the author describes micro-hardness using a
Vickers hardness tester, which falls under the static hardness category. A
brief account on various static indentation tests is presented here.
8.2.2 Static Indentation Tests
For an indentation method, when a loaded indenter is pressed against
the surface of the material, it creates dislocations. As the indentation
continues, newly created dislocations push the dislocations created earlier.
These dislocations move in some preferred direction in the crystal depending
on the slip systems. This motion of dislocations is obstructed by at least four
factors, viz.
1. Impurities and precipitates present in the material (impurity hardening)
2. Other dislocations present in the material (dislocation hardening)
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