Microhardness Testing as a Key to Measuring Material Strength

How Microhardness Testing is done?

Testing a material’s microhardness is a means to determine its hardness or resistance to deformation when the test materials are inadequate for macro-hardness. This kind of testing aids in determining the degree to which very small/thin samples, complicated forms, different material phases, and surface coatings/platings are hard. It is also an effective way to identify depths of case-hardened layers, decarburization or carburization, grind burns, and surface contamination.

Vickers and Knoop Methods 

Vickers and Knoop test methods are used to perform microhardness testing, with applied weights ranging from 25 g to 1 kg. All tests are carried out in accordance with industry standards and are PRI Nadcap and A2LA ISO/IEC 17025 recognised. Certified test reports contain documentation of the test outcomes. Test methods and specifications include ASTM E92, ASTM E384, ASTM E1077, ASTM B578, ASME Sect. IX, MIL Specifications, and ISO 6507 / ISO 9015. There are also hardness conversion charts that compare the results of microhardness tests to those of tensile strength and other hardness scales.

During the microhardness test procedure, a penetrator and a light load are used to force a diamond indenter into the material’s surface, either a Vickers (DPH) or Knoop (KHN) diamond indenter. The Knoop test is applied with a maximum load of 1000 grams and a rhombus-shaped indenter, while the Vickers test uses a square-based diamond pyramid indenter with a maximum load of up to 50 kilograms. After applying the load with a penetrator, the depth of the indentation is measured under a microscope. By combining the depth of the indentation with the test load, the hardness value can be calculated.

Video 1: Microhardness Testing