What should you do if you notice a large disparity in the Vi

What should you do if you notice a large disparity in the Vickers diagonals of a single indent on a sample that exhibits uniform mechanical properties?

Solution

The Vickers hardness test method consists of indenting the test material with a diamond indenter, in the form of a right pyramid with a square base and an angle of 136 degrees between opposite faces subjected to a load of 1 to 100 kgf.

The difference in length of both diagonals and the illumination gradient, are both classic indications of an out-of-level sample. This is not a good indentation.

The difference between the two Vickers diagonal lengths should be max. +/-5%, otherwise the test should be discarded