Brinell, ASTM E10 and IS/ BS Standard
This is a simple indentation test for determining the hardness of a wide variety of materials. The test consists of applying a prescribed load, usually between 500kg and 3000kg for a specified time (10-30 seconds) using a 5 or 10mm diameter tungsten carbide ball on the flat surface of a metal sample.
Knoop, ASTM E384 and IS/ BS Standard
The Knoop indenter has a polished rhombohedral shape with an included longitudinal angle of 172° 30´ and an included transverse angle of 130° 0´. The narrowness of the indenter makes it ideal for testing specimens with steep hardness gradients and coatings. Knoop is a better choice for hardness testing of hard brittle materials.
This testing is similar to Brinell in that a defined indenter is pressed into a material. Once the indenting force is removed, the resulting indentation diagonals are measured. Micro indentation Vickers is per ASTM E384 and Macro indentation Vickers is per ASTM E92.
Rockwell, ASTM E18 and IS/ BS Standard
This test differs from the Brinell test in the shape of the indenter and in the manner that the number is determined. The Rockwell number represents the difference in depth penetration between two loads. There are two types of Rockwell; Rockwell and Superficial Rockwell. The difference between the two are the minor and major loads applied to the specimen. The indenter used may be a diamond cone or a hardened ball depending principally on the characteristics of the material being tested.
Micro hardness, ASTM 3384 and IS/ BS Standard
A micro indentation is made on the surface of a metal sample. The hardness number is based upon the measurements made of the indent formed in the surface of the test specimen.
Portable Hardness, ASTM E110 and IS/ BS Standard
Facility for Portable hardness testing using rebound type digital hardness tester are available for carrying out hardness testing at site. This is particularly useful for large objects and where cutting of sample is not possible.