Hardness testing involves determining surface hardness of a material and is done through the following methods.
Indentation Hardness testing - The basic principle, as with all common measures of hardness, is to observe the questioned material's ability to resist plastic deformation from a standard source.
Non-destructive hardness testing (NDT) - testing carried out by a diamond or ball indentation is for all intents and purposes, still considered a form of NDT. The reason for this is that in the majority of cases the test material is minimally effected. To determine hardness, both the force applied as well as measurements of indentation are evaluated.
Hardness testing allows the inspection of almost any part and heat-treated surface. A range of hardness measurement methodology are available including static Portable Rockwell hardness test as well as the Ultrasonic Contact Impedance (UCI) method.