Microhardness test involves using a diamond indenter to make a microindentation into the surface of the test material, the indentation is measured optically and converted to a hardness value. There are two types of indenters, a square base pyramid shaped diamond for testing in a Vickers tester and a narrow rhombus shaped indenter for a Knoop tester. Typically loads are very light, ranging from a few grams to one or several kilograms. The micro-hardness methods are used to test on a wide variety of materials, such as metals, ceramics, composites, etc.
Microhardness testing is useful for testing very thin materials like foils or measuring the surface of a part, small parts or small areas, measuring individual microstructures, or measuring the depth of case hardening by sectioning a part and making a series of indentations to describe a profile of the change in hardness. The Vickers method is more commonly used. The Knoop method is commonly used when indentations are closely spaced or testing is close to the edge of a specimen due to the narrow shape of the indentation. The width of the Knoop indentation can provide more resolution for measurement and the indentation is also less deep so it is useful for thinner materials.