Hardness testing

Marathwada Mitramandal’s
College of Engineering, Pune
Department of Mechanical Engineering
Subject:- Engineering Materials and
Metallurgy
Topic:- Hardness test
Course Co-ordinator :- Pavanraj S. Khade.
(Assistant Professor MMCOE, Pune)

Hardness Testing
Indentation hardness
Rebound hardness
Scratch hardness
Cutting hardness
Abrasive hardness

Hardness Testing: Indentation
hardness
• Brinell Hardness Test
 The Brinell test is a simple indentation test for
determining the hardness of a wide variety of
materials.
Load: 500 and 3000 kg
(for non-ferrous and ferrous material respectively)
Time: 30 and 10 s
(for non-ferrous and ferrous material respectively)
Indenter: 10 mm diameter steel or tungsten carbide
ball

hardness
• Surface preparation
• Top surface parallel to bottom surface
• Thickness of specimen,

hardness
 The Brinell test is a simple indentation
• test for determining the hardness of a
wide variety of materials.
 The test consists of applying a
constant load (force), usually 500 and
3000 kg (for non-ferrous and ferrous
material),for a specified time (10 to 30
s) using a 10 mm diameter steel or
tungsten carbide ball on the flat
surface of a workpiece

hardness

Hardness Testing: Indentation hardness
Schematic of the principle of
the Brinell indentation process
Brinell indentation with
measuring scale in millimeters

hardness
Drawbacks
1. Because of large size of ball & high load
impression are larger.
2. The ball indenter are likely to deform while
testing hard materials.
3. The test is not recommended for materials
having hardness number more than 400 BHN
4. For some materials piling up effect, & for few
materials sinking effect
5. The test is slow, require more time & readings
are subject to personal errors.

hardness
Advantages:
For certain materials in which hardness varies
from point to point but on an average
hardness is less, a large size indenter is used
which covers more area of material & allow to
measure average hardness.

• Brinell Non standard Hardness Test
In this test, the loads are decreased and also the
ball sizes are reduced.
Ball indenters 1.25, 2.5 and 5.0 mm diameters
with suitable reduced loads are used.
The procedure of testing is similar to that of
standard Brinell hardness test.
The load should be selected such that the
indentation diameter is between 0.25 and 0.50 of
the diameter of ball i.e. it is close to the average
of which is 0.375 of the diameter of ball.

If the tangents are drawn to the edge of an
impression whose diameter is 0.375 of the ball
diameter, the included angle will 136°.
If the loads are properly chosen for an
impression diameter of 0.375 of the indenter,
the impression will be geometrically similar
and BHN will remain same for any size of ball.

• Brinell Non standard Hardness Test
P/D2 Ratio For Various Materials

• Poldi Hardness Test

hardness
• Poldi Hardness Test

hardness
Precautions
• The tube should be held perfectly vertical on
the specimen to avoid elliptical impression.
• Specimen should be kept on hard platform to
avoid rebound.
• The hammer blow should be moderate i.e. it
should neither be too heavy nor be too light.

hardness
• Vickers Hardness Test
• The Vickers test method is similar to the Brinell
principle in that a defined shaped indenter is
pressed into a material, the indenting force is
removed, the resulting indentation diagonals are
measured, and the hardness number is calculated
by dividing the force by the surface area of the
indentation.
• Indenter: Square Base Pyramid with included
angle of 1360 between opposite faces
• Load Applied: 1 to 120 kg

Diamond pyramid indenter used for the Vickers test and
resulting indentation in the workpiece.

hardness

hardness
Advantages :
1. The impressions are small because of small size
of indenter. This does not damage or reduce the
life of component.
2. Since the indenter is made of diamond, it does
not deform during testing of hard materials.
3. For any load of testing contact angle is same i.e.
1360 (vpn is independent of load)
4. Since the impressions are shallow, thin materials
can be tested.

hardness
Limitations :
• Because of small size of indenter, the test is
not recommended for porous powder
metallurgy component.
• The demand good polish of surface, to attain
such polish more time is required.
• The test is slow & subject to personal errors.

Rockwell Hardness Test
 Rockwell hardness testing differs from
Brinell testing in that the Rockwell
hardness number is based on indenter
depth
 Use of a minor load greatly increases the accuracy of
this type of test, because it eliminates the effect of
backlash(inertia) in the measuring system and causes
the indenter to break through slight surface
roughness.

• Rockwell Hardness Test
• Two types of indenters are used:
 Hard steel balls of 1/16", 1/8", 1/4" and
1/2"diameters.
 Brale indenter made of diamond in the
form of a cone with included angle of
120°.
• (The tip of the indenter is accurately ground to a
radius of 0.2 mm.)

 Loads are applied in two stages.
 First a constant minor load of 10 kg is applied
and then major load is applied
 The major loads are 60,100, or 150 kg.

hardness
Brale Indenter

Procedure
1. Place specimen on anvil (No load apply)
2. Rise anvil and apply minor load (10kg)
3. Apply major load by mean of release handle which
is placed at right side of machine(60,100or150)
4. Remove major load(elastic recovery in deformed
region will occur)
5. Hardness can directly measure on dial(without
removing minor load)
6. Minor load removed and next reading will taken on
same specimen with same procedure

Advantages
1 Two types of indenters are used i.e. steel ball &
diamond cone, used to test all types of materials.
2 Thick as well as thin materials can be tested.
3 Surface condition of component to be tested is not
so critical because hardness number is correlated
to the depth of penetration
4 The hardness numbers are obtained directly on the
dial & hence are free from personal errors.
5 The operator needs very little training for
operating this instrument.
6 The test is very fast & require a time less than a
minute.

• Microhardness Test
 These instruments are designed in such a way
that as low as 1 gm and as high as 1000 gm load
can be applied.
 Due to less loads, the impressions are extremely
small and also shallow.
 This feature makes them highly indispensable for
the measurement of hardness of very thin sheet
materials, plated layers, nitrided surfaces and
phases.
 Tukon hardness testing instrument is one of the
machine which is of the above type.

• Microhardness Test
• Two indenters are used for the Tukon
hardness tester
1. The standard Vickers 1360 diamond
pyramid
2. The diamond Knoop indenter.
• The Knoop indenter consists of a pyramidal
shaped diamond cut to an included transverse
angle of 1300,and an included longitudinal angle
of 172030'

• Microhardness Hardness Test

Durometers
• They are use for measuring the hardness of plastic &
rubbers & are of various type
• The A-2 type durometer is used for soft rubber & non
rigid plastcs.
• The D-2 type durometer is used for hard rubber &
plastics.
• Hardness is correlated with the depth of
indentation in an inverse manner & reported in
terms of numbers from 0 to 100.
• 0 number corresponds to depth of 0.1 inch & 100
number corresponds to depth of 0.001 inch.

• Indenters are conical in shape & are made of
steel.
• The sharpness of cone depends on the type of
durometer.
• Type D durometer has the sharpest indenter &
the applied load is also more.
Durometers

Durometer Hardness
Testing Machine

Hardness testing

Recommended

Recommended

More Related Content

What's hot

What's hot (20)

Similar to Hardness testing

Similar to Hardness testing (20)

Recently uploaded

Recently uploaded (20)

Hardness testing