pptx on cryogenic hardening

1. DEPARTMENT OF MECHANICAL ENGINEERING
CRYOGENIC HARDENING
GUIDED BY PRESENTED BY
Mr. Anoop T.M Ahadil Ameer P
Asst. Prof. 14418006
PRSCET

2.  INTRODUCTION
 HARDENING TECHNIQUES
 CRYOGENIC SYSTEMS
 THEORY
 PROCESS
 ADVANTAGES
 DISADVANTAGES
 APPLICATIONS
 CONCLUSION
 REFERENCE

3.  Cooled to approximately −185 °C
 Developed for aerospace applications
 Increased hardness, strength,etc
 Done on tool steels, high-carbon, and high-
chromium steels
 Done after initial quenching.
 Austenite to martensite

4.  Work hardening
 By plastic deformation
 Done at low temperature that atoms cant rearrange
themselves
 Precipitate hardening
 Using alloy which precipitate on cooling
 Quenching
 Cooling at rapid rate
 For making martensite
Case hardening
Surface hardening technique
Differential hardening
Diffusion hardening

5. DIFFERENTIAL HARDENING
FLAME HARDENING
•Using oxy gas flame
INDUCTION HARDENING
•Using induction coils
DIFFUSION HARDENING
Carburizing Nitriding Carbon
nitriding
Ferric
nitrocarb
urizing
Boriding

6. 1)Heat exchanger system
 liquid nitrogen passed through a heat
exchanger and the exhaust gas used as a furnace
atmosphere.
 This gas is circulated around the heat exchanger parts
using a fan .
 Neither liquid nitrogen nor dry nitrogen gas ever
comes in contact with the parts.
 Figure 1 shows a heat exchanger type

7. Direct Spray System
• Sprays liquid nitrogen directly into the chamber,
• A fan circulates the gas over the work.
• In this case, the spent gas cannot
be recovered

8. Step-immersion system
 Part is immersed in cryogenic agent for a time period
of about ten minutes.
 The part is then withdrawn from contact with the liquid
cryogenic material.
 It is immediately subjected to a flow of air.
 Process time required is a 25 minutesInch thickness

9. Transformation to martensite
 Due to rapid cooling
Precipitation of microscopic carbides
 Carbides get into micro pores in the structure

10. COOL DOWN
 Temperature: (-150 C)
 Time period : 6-10 h
SOAK
 Temperature :(-180 C)
 Time period: 8-40 h.
 Crystal structure of the metal changes at this
temp at a slower rate.
 Precipitation of fine carbides occurs.

11. WARM UP:
 Temperature: room temperature
 Time period : 8-20 h.
 Ramping up too fast can cause cracking
TEMPER HEAT UP:
 Temperature: 422 F- 866F.
 The cryogenic temperature will convert almost all
retained austenite into primary martensite
 To reduce the brittleness it is tempered.
 We ramp up the temp slowly to assure the temp
gradients within the part are kept low.

12. TEMPER HOLD:
 Holding the elevated temperature for a specific time.
 A typical temper hold time is about 3 hours.
 This time depends on the thickness and mass of the
part.
 There may be more than one temper sequence for a
given part or metal, some metals perform better if
tempered several times.

13. Temperature-time curve

15. Austenite Martensite

16.  Enhances abrasive wear resistance
 Improves corrosion resistance
 Increases dimensional stability
 Closes and refines metal grain structures
 Increased hardness
 Reduces retained stresses
 Cuts operating costs and downtime by reducing the
need for tool replacement or regrinding and
maintenance
 Better surface finish

17.  High cost of operation
 Difficult to Maintain temperature
 Area Under Research

18.  Stabilization of aluminum and magnesium
alloys
 Manufacture of tool for wire EDM
 Aerospace and defense
 Automotive
 Cutting tools
 Musical instruments
 Medical instruments
 Sports equipment

19. Cryogenic hardening is a permanent, non-
destructive, non-damaging process, which reduces
abrasive wear , relieves internal stress, minimizes the
micro cracking due to shock forces, lengthens part
life, and increases performance.

20.  www.sciencedirect.com/
 wikipedia
 Material science and metallurgy text book
 Thermofusion sytems
 David N. Collins “Cryogenic Treatmentof
Tool Steels.” Advanced Materials &Processes
December 1999.