The Rockwell hardness test measures the hardness of materials using indenters under specific loads. It is a quick, inexpensive, and non-destructive test that can be used to test finished parts without damaging them. The test uses a diamond or steel ball indenter that makes an impression under an initial minor load and then a deeper impression under a major load. The hardness number is read from a dial and indicates the material's resistance to plastic deformation. The test is commonly used for quality control and finding tensile strength.

1. Rockwell Hardness Test

2. Definition of Hardness :
 Hardness is the property of a material that enables it to resist plastic deformation
usually by penetration. However the term hardness also refer to resistence
bending, scratching, abrasion or cutting.
 This test also performed when the material’s hardness beyond the range of
Brinell’s hardness.
 Hardness is dependent on ductility, elastic stiffness, plasticity, strain, strength,
toughness, viscoelasticity, and viscosity .This properties are not same for all
materials. That’s why the hardness numbers of different materials are different.
 The purpose of the hardness test is to find out the tensile strength of the
materials.

3. WHY USE A HARDNESS TEST ?
 Easy to perform
 Quick-(1 to 30 sec)
 Relatively inexpensive
 Non-destructive
 Finished part can be tested-but not ruined
 Virtually any size and shape can be tested

4. Rockwell Hardness Test :
 The Rockwell Hardness test uses a machine to apply a specific load and then
measure the depth of the resulting impression.
 It is useful for finished material testing .
 Hardness number is indicated on dial.
 Test piece is place on table of the instrument.
 Indenter is brought into contact with surface of test piece under light load(minor
load).
 Scale is then adjusted to zero.
 Major load is applied ,hardness index is read from the scale.

12. Construction of Rockwell Hardness Tester :

13. Test Principle :
Rockwell hardness Number (RHN) based on an inverse relationship to the
measurements of the additional depth Which an indenter is forced by a heavy (major)
load beyond the depth resulting from a previously applied (minor) load.
It consists of measuring the additional depth of heavy load indenter beyond
the depth of previously applied light load (minor).

14. Types of Indenter :
 This test has 9 scales of hardness ( A to H &k). But B & C is widely used.
 In scale C, A standard 120 degree Diamond cone indenters are used for testing
hard materials such as hardened steel and cemented carbides.
 In scale B,A standard steel ball indenter(with diameter of 1/16,1/8,1/4,1/2 inch.)
are used for testing softer materials such as fully annealed steel, softer grades of
cast iron , wide variety of non-ferrous metals and some nonmetallic materials.

15. Advantages :
 The most widely used method for determining hardness.
 Simple to perform
 Highly skilled operators are not required.
 Different types of loads and indenters can be used.
 The entire operation completes within 10 sec.
 The direct Rockwell hardness number readout on the dial.

16. Disadvantages :
 Possible errors due to shifting of the sample under test load during test cycle
 Quality of the indenter has a strong influence on the test result

17. Difference Between Rockwell Hardness & Brinell
Hardness :
Rockwell Hardness Brinell Hardness
Conical diamond indenter with 120° Included
angle.
Ball Indenter 1/16 , 1/8 , 1/4 and 1/2 inches
diameter.
Ball Indenter: 1mm, 2.5mm, 5 mm and 10 mm ball
diameter.
Two loads Minor 10N, Major 60 -100-150N Single load from 1N to 3000N
The Rockwell hardness is based on difference
indentation depth of indenter from two
load applications.
In Brinell hardness test hard ball indenter is pressed
under load on surface of material. The Brinell
hardness number is expressed as ratio of load and
area of indentation.
Quick and cost effective process. This process is slow. The test cycle takes somewhere
between 30 to 60 seconds.
# Rockwell’s test differs from The Brinell’s test that In Rockwell’s test The loads for making
indent are smaller and thus make smaller and shallower indents.
Some others difference are as follows:

18. Thank You