The document outlines the steps to prepare a specimen for microscopic examination, including cutting, grinding, belt polishing, paper polishing, etching, and examination. Specimens are cut to a convenient size and any irregularities are removed through grinding with an emery wheel or paper. Successive finer grades of emery paper are used to polish the surface. Further polishing is done with cloth or velvet to produce a mirror finish. Etching with acid or chemicals reveals grain and grain boundaries under the microscope. The prepared specimen is then examined under a metallurgical microscope.

1. ITM UNIVERSE
Institute of Technology & Management
Universe
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2. SPECIMEN
PREPARATION FOR
MICRO-EXAMINATION
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3. SAMPLE PREPARATION
 Microscopic examination begins with:
1) Cutting
2) Grinding
3) Belt Polishing
4) Paper Polishing
5) Etching
6) Examination through microscope
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4. PROCESS:-
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5. SELECTING OF SPECIMEN FOR MICRO-
EXAMINATION
 A larger body of metal may not be homogeneous either
in composition or crystal structure
 A specimen approx. 20 mm diameter or 20 mm square in
a convenient size to handle is cut parallel to the method
of manufacturing by saw/abrasive cutter.
 Very small specimens are difficult to polish & this can
best be done by mounting them.
 Mounting a specimen provides a safe, standarised &
ergonomic way by which to hold a sample during
grinding & polishing operations
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6. GRINDING THE SPECIMEN
 The surface of the metal or alloy may have irregulurities
which are to be removed before preparation of the
specimen
 The cut sample og metal or alloy is ground by using a
suitable quality grinding wheel or by an emery paper
polishing upon the irregularities present on the surface.
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7. BELT POLISHING
 After grinding operation is over the next step is to polish
the ground surface of the specimen since the observation
of the microstructure is possible by reflection of the light
rays in case of optical microscope.
 For the reflection of the light to be possible the surface of
specimen must be well polished so we first use the 30 to
40 aluminum oxide belt.
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8. BELT POLISHING MACHINE
Belt :- 100mm width x 1000mm length
Rotation :- 1400rpm
Surface speed :- 760rpm
Motor :- 750W
Power :- 380V/50HZ
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9. PAPER POLISHING
 In this polishing require use of emery paper of different
grades such as 1/0, 2/0, 3/0, 4/0, an increasing number of
zeros that indicates that fineness of abrasive particle on
the paper increase.
 The polishing is carryout manually on the ground surface
of the specimen by selecting course grade paper by
moving the specimen to and fro number of times in one
direction.
 The same surface is polished by the next grade emery
paper by rotating the specimen through 90 degree in a
way that the scratches of the previous grade are
completely removed by new ones.
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10. DIFFERENT TYPES OF EMERY PAPER
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11. MIRROR POLISHING
 Once the paper polishing over mirror polishing is done
by using a wet polishing mill having special velvet cloth
being rotated at high speed.
 The specimen surface which is dry polished is kept in
contact with the rotating cloth and special paste of
alumina is poured while the cloth is rotated which range
is 0.5 – 0.03 micrometer.
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12. MIRROR POLISHING MACHINE
Double Disc Polishing Machine
Model -Single/Double Disc
Variable Speed
Digital R.P.M Display
Driven By AC Motor
Double Disc
400 to 1400 R.P.M
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13. ETCHING THE SPECIMEN
 To obtain the visual difference between grain and grains
boundary under the microscope etching process is required.
 In this process of etching a dilute acid or a chemical regent is
applied on the polished surface of the specimen for about five
to ten seconds.
 After that the specimen is washed by flowing water
sufficiently. Thus a depression of an atomic size is produced
throughout the grains boundaries if the metal surface.
 Because of this differential etching process, the light rays if
microscope get reflected back with different intensities.
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14. EXAMINATION
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15. EXAMINATION
 After polishing, the specimen is examined under the
metallurgical microscope by placing it on its table.
Normal Carbon steel
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16. THANK YOU
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