Micro-indentation Hardness

Hardness testing has found wide application as a method for the classification of materials and for the comparative study of changes in their properties. Hardness is usually determined by abrasion tests, by scratch tests, or by indentation testing. ' The latter method, however, has found most extensive application. The Brinell test, first described in 1900,2 is conducted by pressing a steel ball into the surface to be tested until a specified load is reached. The Brinell hardness, HB, is computed as the ratio of the load (3,000 kg.) to the contact area in square millimeters. The Rockwell hardness testing method is essentially based on a similar principle. The range of application of Brinell and Rockwell testing is limited by the fact that steel-ball indenters may be deformed when used on very hard materials. Smith and Sandland3 used polished diamond pyramids with angles of 120°-150° and, as a result of practical and theoretical considerations, recommended the use of square-based diamond indenters with the 1360 included angle, commonly known as the Vicker's diamond indenter. The Vicker's hardness is normally determined by using loads varying from 1 to 120 kg. The geometry of the Vicker type indentation is inde-