Vickers indentations are geometrically similar, unlike those made by spherical indenters. Therefore Vickers hardness number (VHN) is usually independent of the load.  VHN is related to ultimate tensile strength, yield stress and fatigue strength. These relationships are well documented in the literature.

Vicker hardness  uses a square - base diamond . Vickers hardness provides a continuous scale of hardness , for a givel load , from very soft metal alloys to extremely haed metal alloys . A perfect indentation made with a perfect diamond - pyramid indentor would be sqare .

Normally, the vickers hardness can represent the strength of alloy in someway. 

Hi Ibrahim,

Among hardness tests, Brinell and Rockwell are  commonly used. They use spherical indenters, which yield geometrically dissimilar indentations. Vickers hardness tests use pyramidal indenters, which result in geometrically similar indentations. The main advantage of the Vickers hardness test is that extremely accurate readings can be taken, and just one type of indenter is used for all types of metals and surface treatments. In addition, there has been a strong relation with tensile properties and Vicker hardness measurements.

I hope this helps.

In industry, Vicker hardness testers are preferred for their broader range and accuracy. It covers almost whole range of metals commonly used from soft ones to hard ones. Talking from laboratory point of view when there is load of work it is not convenient for operator to change indenters for different type of materials, rather they use Vickers indenter which covers all type of materials. 

Vickers hardness tester are very accurate in measuring Effective case depth in case hardened gears.compare to Rockwell hardness  tester.Vickers take less space .In 1mm space we can take 8 to 9 reading and estimate ECD in surface hardened components

Vickers hardness is very interesting because its independent of the load and the range of hardness scale is much higher than other methods as Rocwell C or B, or Brinell. It permits you compare the hardness of metal alloys either high or low values. You need to take care with Vickers hardness when the material is heterogeneous mainly if you use a small load.