sample for hardness test

1. Hardness Test 1/5
LAB 2
HARDNESS TEST
OBJECTIVES
(1) Make Brinell, Vickers and Rockwell hardness measurements on different
materials specimens.
(2) Compare the measurements in hardness with each other.
INTRODUCTION
Hardness can be defined as resistance to penetration, resistance to abrasion, resistance
to scratching, or resistance to cutting. These are related in that they all require plastic
flow of the material. A variety of tests for hardness are in use, depending on which of the
above situations is of most interest. Material properties, such as hardness can be
altered to desired levels by various heat treatment procedures. Heat treatments affect
the microstructure of the metal. Detailed descriptions of the changes to the
microstructure can be found in material science (1) lecture notes.
This experiment will include Brinell, Vickers and Rockwell tests which measure
resistance to penetration. The amount of deformation that occurs when a small, hard
steel ball or diamond point is pressed into a material surface at some designated load is
the measure of the hardness of the material.
BRINELL HARDNESS TEST
The Brinell test for this experiment uses steel ball with different diameters which is
pressed into a specimen by a different load that is maintained for 15 to 30 seconds. The
Brinell hardness number (BHN) is calculated by:
[ √ ]
Where:
P is the test load [kg]
D is the diameter of the ball [mm]
d is the average impression diameter of indentation [mm]
Since the Brinell number is based on the area of indentation, the diameter of the
indentation must be measured. This is done with a microscope. The scale seen through

2. Hardness Test 2/5
the microscope is in millimeters. The larger diameter indentation corresponds to a softer
material and lower Brinell number.
VICKERS HARDNESS TEST
The Vickers hardness test method consists of indenting the test material with a diamond
indenter, in the form of a right pyramid with a square base and an angle of 136 degrees
between opposite faces subjected to a load of 1 to 100 kgf. The full load is normally
applied for 10 to 15 seconds. The two diagonals of the indentation left in the surface of
the material after removal of the load are measured using a microscope and their
average calculated. The area of the sloping surface of the indentation is calculated. The
Vickers hardness is the quotient obtained by dividing the kgf load by the square mm
area of indentation.
P is the load and it can be varied from 1 to 1000 grams
d is the average diagonal diameter of indentation [mm]
When the mean diagonal of the indentation has been
determined the Vickers hardness may be calculated from the above formula. The
Vickers hardness should be reported like 800 HV/10, which means a Vickers hardness
of 800, was obtained using a 10 kgf force.
The advantages of the Vickers hardness test are that extremely accurate readings can
be taken, and just one type of indenter is used for all types of metals and surface
treatments.
ROCKWELL HARDNESS TEST
The penetrators for the Rockwell hardness tester range from 1/2-inch diameter steel
balls to very small diamond (brale) tips (points). The smaller points are used for harder
materials that have a greater resistance to indentation. There are various force scales
used for various materials. The Rockwell B and Rockwell C scales will be used for this
experiment. The Rockwell B scale is suitable for soft engineering metals, and the
Rockwell C scale is appropriate for hard engineering metals. Each scale requires a
specified tip and load. The B scale uses a 1/16- inch diameter hard steel ball and a 100-
kg load. The C scale uses a conical diamond point and a 150-kg load.

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To perform the Rockwell tests, the penetrator is pressed against the specimen with an
initial 10-kg preload to properly seat the penetrator. The remaining load is applied
gradually after the dial on the hardness tester has been zeroed. After the penetrator has
stopped moving into the specimen, the final position of the dial pointer indicates the
Rockwell hardness number that is related to the depth of penetration.
There are numerous scales in Rockwell test, which are made possible by the
combination of different loads and indenters. The scales are identified by letters and the
common scales range from A through K, with I and J left out, as given in the following
table

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MATERIALS TO BE TESTED
Different materials specimens will be tested in this laboratory experiment namely:
aluminum alloy, carbon steel, stainless steel, Al-alloy, commercial pure copper and
brass. The hardness of mild-steel washer will also be tested to check the validity of
Brinell hardness test.
EQUIPMENT TO BE USED:
Zwick/ZHU187.5 - Universal hardness tester up to 187.5 kg
STUDENT WORK
Selected students will be invited to perform Brinell and Rockwell hardness test,
instructor will do perform Vickers test in order to avoid the diamond pyramid damaging
that could be taken place.
For Brinell experiment, student has to calculate the BHN and depth of impression (h)
through the following formulas for each material tested:
[ √ ]
[ √ ]
For Vickers experiment, student has to calculate the VHN through the following formula
for each material tested:
For Rockwell experiment, student has to calculate the depth due to major load (t)
through the following formulas for each material tested:

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Results:
Exp.
Type
Material Mild
steel
Stainless
steel
Al alloy Pure
copper
Brass Steel
washer
BrinellHardnessTest
d1 [mm]
d2 [mm]
d=(d1+d2)/2 [mm]
P [kg]
D [mm]
H [mm]
√
[mm]
d/D
H/h
[ √ ]
VickersHardnessTest
d1 [mm]
d2 [mm]
d=(d1+d2)/2 [mm]
P [kg]
RockwellHardnessTest
RC (diamond & 140 kg)
RB (1/16” & 90 kg)
RE (1/8” & 90 kg)
RH (1/8” & 50 kg)
Comment:
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