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HEAT TREATMENT TECHNOLOGY
by
Dr. SANJIB BANERJEE
DEPARTMENT OF MECHANICAL ENGINEERING
TEZPUR UNIVERSITY
2020
Dr. Sanjib Banerjee 1
IRON CARBON SYSTEM
Fe-C PHASE DIAGRAM
Dr. Sanjib Banerjee 2
IRON CARBON SYSTEM
Fe-C PHASE DIAGRAM
✓It may be noted that one eutectic exists for the iron–iron carbide
system, at 4.30 wt% C and 1147 °C
✓It may be noted that a eutectoid invariant point exists at a
composition of 0.76 wt% C and a temperature of 727 °C
Dr. Sanjib Banerjee3
DEVELOPMENT OF MICROSTRUCTURE IN IRON CARBON SYSTEM
Dr. Sanjib Banerjee 4
❑ Photomicrograph of a
eutectoid steel showing the
pearlite microstructure
consisting of alternating
layers of ferrite (the light
phase) and Fe3C (thin layers
most of which appear dark).
DEVELOPMENT OF MICROSTRUCTURE IN IRON CARBON SYSTEM
EUTECTOID STEEL
Dr. Sanjib Banerjee 5
DEVELOPMENT OF MICROSTRUCTURE IN IRON CARBON SYSTEM
EUTECTOID STEEL
❑ Schematic representation of the formation of pearlite from
austenite; direction of carbon diffusion indicated by arrows.
Dr. Sanjib Banerjee 6
❑ Schematic representations of
the microstructures for an
iron–carbon alloy of
hypoeutectoid composition
(containing less than 0.76
wt.% C) as it is cooled from
within the austenite phase
region to below the eutectoid
temperature.
DEVELOPMENT OF MICROSTRUCTURE IN IRON CARBON SYSTEM
HYPO-EUTECTOID STEEL
Dr. Sanjib Banerjee 7
❑ Photomicrograph of a 0.38 wt.% C steel having a
microstructure consisting of pearlite and proeutectoid
ferrite
DEVELOPMENT OF MICROSTRUCTURE IN IRON CARBON SYSTEM
HYPO-EUTECTOID STEEL
Dr. Sanjib Banerjee 8
❑ Schematic representations of
the microstructures for an
iron–carbon alloy of
hypereutectoid composition
(containing between 0.76 and
2.14 wt% C), as it is cooled
from within the austenite
phase region to below the
eutectoid temperature.
DEVELOPMENT OF MICROSTRUCTURE IN IRON CARBON SYSTEM
HYPER-EUTECTOID STEEL
Dr. Sanjib Banerjee 9
❑ Photomicrograph of a 1.4 wt%
C steel having a microstructure
consisting of a white
proeutectoid cementite network
surrounding the pearlite
colonies
DEVELOPMENT OF MICROSTRUCTURE IN IRON CARBON SYSTEM
HYPER-EUTECTOID STEEL
Dr. Sanjib Banerjee 10
❑A portion of the Fe–Fe3C phase diagram used in computations for
relative amounts of proeutectoid and pearlite microconstituents for
hypoeutectoid and hypereutectoid compositions.
DEVELOPMENT OF MICROSTRUCTURE IN IRON CARBON SYSTEM
Dr. Sanjib Banerjee 11
DEVELOPMENT OF MICROSTRUCTURE IN IRON CARBON SYSTEM
Dr. Sanjib Banerjee 12
DEVELOPMENT OF MICROSTRUCTURE IN IRON CARBON SYSTEM
Dr. Sanjib Banerjee 13
