over all study about cryogenic hardening.

1. Presented by,
Guided by.
DR D.Y Patil School of Engineering & Technology
A
Seminar
on

2. Contains for
the Seminar
2
DYPSOET II CRYOGENIC HARDENING
Need of Cryogenic Hardening
Introduction
How Cryogenic Hardening takes place
Application of Cryogenic Hardening
Advantages of Cryogenic Hardening
Limitations of Cryogenic Hardening
Reference
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3. Need of
Cryogenic
Hardening
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DYPSOET II CRYOGENIC HARDENING 24-04-2019
Conversion of retained austenite into martensite.
Fine Carbide Precipitation.
Stress relieves
Tensile Stress And Hardness
High Cycle Fatigue

4. Introduction
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DYPSOET II CRYOGENIC HARDENING
Cryogenic Treatment(CT) is the process of cold treatment below the
sub-zero temperature
The temperature is about -196°C or 77°K reach up to 4 °K
It is an inexpensive permanent treatment affecting the entire
section of the component unlike coating.
Cryogenic treatment Improves hardness, fatigue resistance,
toughness, and wear resistance of steel.
The third law of thermodynamics states that entropy is zero at
absolute zero temperature. Deep sub-zero treatment uses this
principle to relieve stresses in the material
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5. Process Of Cryogenic Heat Treatment
Quenching
Cryogenic
processing
TemperingAustenite
Heat treatment sequence for maximum martensite
transformations
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6. Austenite
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DYPSOET II CRYOGENIC HARDENING
Austenitization which means to heat the iron, iron
based metal or steel to a temperature at which it
changes crystal structure from ferrite to austenite.
During austenitizing, the final alloying element
partitioning occurs between the austenite matrix (that
transforms to martensite on cooling) and the retained
carbides.
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7. Quenching
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DYPSOET II CRYOGENIC HARDENING
After Austenitizing temperature, the steel is
cooled to ambient temperature rapidly in a
suitable quenching media like water, oil, air.
Once the austenite is cooled below its critical
temperature, it becomes unstable and it
starts to transform into martensite.
After conventional heat treatment(CHT) there
would always be some retained austenite in
the steel, which is up to 20-30%.
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8. Cryogenic
Process
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DYPSOET II CRYOGENIC HARDENING
Cryogenic Treatment (CT) of tool materials cooling temperature
consists of two stages.
1) Shallow Cryogenic Treatment (SCT)
2) Deep Cryogenic Treatment (DCT)
RAMP DOWN
SOAKING
RAMP UP
TEMPER HOLD
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9. Cryogenic Process
 The process is capable of treating a wide
variety of materials, such as ferrous and non-
ferrous metals, metallic alloys, carbides,
plastics (including nylon and Teflon) and
ceramics
 The process is not a surface treatment; it
affects the entire mass of the tool or
component being treated, making it stronger
throughout
 The hardness of the material treated is
unaffected, while its strength is increased
C
BCT
C
FCC
%8.0
)('
%8.0
)( 

Fig.:-Phase Transform in Cryogenic
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10. Properties of
Cryogenic
Process
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DYPSOET II CRYOGENIC HARDENING
In sub-zero temperature steel, increasing austenitizing
temperature increases amount of retained austenite
In DCT, reduction in austenite content will increase the
amount of secondary carbides by ≈47% and 38% in
comparison to CHT and CT, respectively.
Due to super saturation martensite with carbon and
thermodynamic instability the carbon atoms squeezed
out of martensite, migrated to the neighbouring lattice
defects and acted as nucleation sites for the growth of
fine carbides.
The martensite and fine carbide formed by deep
cryogenic treatment work together to reduce abrasive
wear
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11. Microstructure
 Comparative microphotographs
(1000x) of steel samples show the
change in microstructure produced by
the controlled deep cryogenic process.
 Uniform, more completely
transformed microstructure and less
retained austenite at right, is related to
improvements in strength, stability
and resistance to wear
Before Process After Process
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12. Tempering
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DYPSOET II CRYOGENIC HARDENING
Tempering consists of heating a hardened steel to
a temperature below eutectoid temperature. This
makes it softer and ductile.
The carbon trapped in the martensite
transformation can be released by heating the steel
below the 723˚C transformation temperature.
This release of carbon from nucleated areas allows
the structure to deform plastically and relive some
of its internal stresses
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13. Application
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DYPSOET II CRYOGENIC HARDENING
Cutting tools for different machining operations: sawing,
milling, drilling, broaching, turning, slitting, shearing
Metal forming tools: dies, molds, punches
High precision parts: gauges, guides, shafts
Parts of high performance (sport) car engines and
transmissions: crankshafts, connecting rods, piston rings,
engine blocks, gear parts, camshafts
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14. Advantages
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DYPSOET II CRYOGENIC HARDENING
Increases wear resistance of material
Cost of process very small
Transforms soft-retained austenite to martensite
Changes entire structure, not just surface
May increase tensile strength, toughness and release internal
stresses
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15. Limitations
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DYPSOET II CRYOGENIC HARDENING
Handling and storage of cryogenic gases can be
dangerous
Low temperature hazard and oxygen enrichment
Due to high density of fuel, they can become a
dense gas during leakage. This can reduce the
oxygen level leading to Asphyxia (a condition of
severely deficient supply of oxygen to the body that
arises from abnormal breathing
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