accurate micro/macroindentation hardness-Vickers and Knoop-tests can be a
difficult process, even under the best conditions. Preparing the surface
properly to allow the optical measurement, and the manual indent measurement
process, using a high-powered microscope, is time consuming and costly.
Hardness, as applied to most materials, particularly metals, has been defined in many ways by physicists, metallurgists and engineers. These definitions range from a “conglomeration of properties of a material more or less related to each other” to the commonly accepted idea of “resistance to permanent indentation.” These varied definitions point out the complexity of truly defining hardness so that it satisfies all the criteria associated with the characteristics of hardness.