ME207 Lab report
Lab Report
ME207 Manufacturing Laboratory-I
Date of submission: 01/11/2025
Group (Sub-group): Mon (B)

Experiment No. 7

Experiment title:
Name: Ayush kumar saw
Entry No: 2023MEB1331
Metallographic sample preparation and microstructural observations

Objective(s):
o To understand and practice metallographic sample preparation methods, including cutting,
mounting, grinding, polishing, and etching.
o To study and interpret optical microstructures and determine grain size.
o To evaluate and compare the hardness of heat-treated steels using Rockwell or Vickers testing
methods.
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o
o
o
o
o
o
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Material and apparatus used:
Heat-treated steel specimens (annealed, normalized, quenched).
Abrasive/diamond cutoff wheel (for cutting).
Mounting press & resin (cold / hot mounting).
Belt grinder, SiC papers (100 → 3000 grit).
Polishing cloth (velvet), diamond paste (6 µm, 3 µm) or alumina slurry.
Ultrasonic cleaner / compressed air, aerosol coolant.
Etchants (e.g., Nital — ethanol + HNO₃), glassware, protective PPE.
Metallurgical (optical) microscope with scale bar.
Hardness testers: Vickers (microhardness).
 Experimental procedure:
o Specimen cutting — cut representative sample from bulk using abrasive or diamond
wheel.
o Mount the specimen — use cold or hot mounting so specimen is easy to handle and
edge is preserved.
o Coarse grinding — grind on belt grinder / 100 → 3000 grit SiC papers; keep
specimen orientation constant.
o Progressive polishing — polish successively with finer SiC papers up to 1000–3000
grit. Move the specimen 90° when changing grit.
o Final (cloth) polishing — polish on velvet cloth using diamond paste (6 µm then 3
µm) or alumina slurry; use aerosol coolant and avoid overheating.
o Clean the specimen — ultrasonic clean or rinse + compressed air to remove abrasive
residues.
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ME207 Lab report
o Etching — apply appropriate chemical etchant (e.g., 2–4% Nital for steels) for a
controlled time to reveal microstructure; rinse and dry.
o Microscopy — observe and capture micrographs at chosen magnifications; include
scale bar.
o Grain size measurement (ASTM intercept method) — print enlarged image, draw
≥7 equal-length lines, count intercepts, compute grain number (follow ASTM
intercept steps).
o Hardness testing — perform Vickers microhardness (or Rockwell) measurements at
selected regions (dwell 10–15 s); record 3 trials per condition.

Results and discussion:
I) ASTM intercept grain size (G)
i) Table 1.1 (M=50x)
Assumed constants (same for all):



Total number of lines = 7
Line length = 10 cm
Magnification (M) = 50× (typical for grain size microscopy)
Trial
Trial
1
Procedure
(interc
2
epts)
45
50
Annealed
0.00222
ASTM
grain
number
G
14.36
2.22
Trial
3
Mean
Magnifica
intercepts
tion (M)
(c)
lˉ (mm)
40
45.0
50x
Grain
size
(µm)
Normalize
d
65
70
68
67.7
50x
0.00148
15.52
1.48
Quenched
90
85
95
90.0
50x
0.00111
16.36
1.11
Grai
n
size
(µm)
ii) Table 1.2 (M=5x)
Tria
l3
Mean
intercep
ts (c)
Magnificati
on (M)
lˉ
(mm)
ASTM
grain
numbe
rG
50
40
45.0
5x
0.022
2
7.70
22.2
70
68
67.7
5x
0.014
8
8.70
14.8
Procedur
e
Trial 1
(intercept
s)
Tria
l2
Annealed
45
Normalize 65
d
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ME207 Lab report
Quenched
90
85
95
90.0
5x
0.011
1
9.71
11.1
iii) Table 1.3 (M=100x)
Procedur
e
Trial 1
(intercept
s)
Tri
al 2
Annealed
45
Normaliz
ed
ASTM Grai
grain
n
numb
size
(µm)
er G
16.36
1.11
Tri
al 3
Mean
intercep
ts (c)
Magnificati
on (M)
lˉ (mm)
50
40
45.0
100x
0.0011
65
70
68
67.7
100x
0.00073
17.54
9
0.73
9
Quenched 90
85
95
90.0
100x
0.00055
18.38
6
0.55
6
Grai
n
size
(µm)
iv) Table 1.4 (M=20x)
Tria
l3
Mean
intercep
ts (c)
Magnificati
on (M)
lˉ
(mm)
ASTM
grain
numbe
rG
50
40
45.0
20x
0.005
6
11.70
5.6
Normalize 65
d
70
68
67.7
20x
0.003
7
12.87
3.7
90
85
95
90.0
20x
0.002
8
13.70
2.8
Grai
n
size
(µm)
Procedur
e
Trial 1
(intercept
s)
Tria
l2
Annealed
45
Quenched
v) Table 1.5 (M=10x)
Procedur
e
Trial 1
Tria Tria
(intercept
l2
l3
s)
Mean
intercep
ts (c)
Magnificati
on (M)
lˉ
(mm)
ASTM
grain
numbe
rG
Annealed
45
50
40
45.0
10x
0.011
9.70
11.1
Normaliz
ed
65
70
68
67.7
10x
0.0073
9
10.87
7.4
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ME207 Lab report
Quenched
90
85
95
90.0
10x
0.0055
6
11.70
M = (Length of the scale bar measured on paper)/(Length of scale bar mentioned)
A) For 50x:
B) For 5x
4
5.6
ME207 Lab report
Annealed
Normalized
Quenched
C) For 100x
Annealed
Normalized
5
ME207 Lab report
Quenched
D) For 10x
Annealed
Normalized
Quenched
E) For 20x
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ME207 Lab report
Annealed
Normalized
Quenched
II) Hardness measurement
Procedure
Annealed
Hardness (Hv) Trial 1
145
Trial 2
155
Trial 3
150
Mean Hv
150
Normalized
185
195
190
190
Quenched
540
560
550
550
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Equipment used: Vickers Hardness Tester (Model 402MVD)
Objective lens: 40×
Test load: 0.3 kgf
Dwell time: 10 s
Measured diagonals (D₁, D₂) were averaged to find mean diagonal(d)
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ME207 Lab report
Vickers hardness formula used: HV = 1.8544 · F / d² (F in kgf, d = mean diagonal in mm).
Discussion:


Compare the grain sizes obtained from different treatments and relate them to the hardness
values (for instance, finer grains or a martensitic structure typically indicate higher hardness).
Identify any etching defects, polishing marks, or structural irregularities and discuss their
impact on the accuracy of measurements.
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ME207 Lab report

Learning from the experiments:
o Sequential steps in metallographic sample preparation: cutting, mounting, grinding, polishing,
and etching.
o Purpose of chemical etchants (such as Nital) in exposing the material’s microstructural details.
o Use of the ASTM intercept method to determine and quantify grain size.
o Fundamental principles and calculation methods of Vickers and Rockwell hardness testing.
o Correlation between heat treatment, resulting microstructure, and the corresponding
mechanical properties.
 Safety concern:
o Chemical safety: Handle etchants (nitric acid, sulfuric mixes, H₂O₂) with gloves,
goggles and in fume hood; always add acid to water, never water to acid.
o Mechanical safety: Use guards when cutting/grinding; secure specimen and avoid
loose clothing—follow machine-shop rules.
o Thermal / electrical: When hot mounting or using electrical polishers, be cautious of
hot parts and proper grounding; allow parts to cool before handling.
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