A Study on Effect of Cryogenic Treatment on

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A Study on Effect of Cryogenic Treatment on M2
Tool Steel
Rajendra M. Kelkar
Advisor Prof. Philip Nash
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• Perform mechanical tests
• Characterize the microstructural changes
• Correlate microstructural changes with the
• observed mechanical test results

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• Perform extensive search on,
• physical metallurgy and heat treatment of
  steels
• Cryogenic treatment of tool steel
• Microstructural characterization techniques
• Design various experiments/tests
• Prepare samples
• Schedule experiments and tests
• Analyze and conclude the results

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Study Material

• Chemical Composition Of M2 Tool Steel
• Carbon 0.85 to 1.00
• Chromium 4.00
• Molybdenum 5.00
• Vanadium 2.00
• Tungsten 6.00

• Manganese 0.30
• Nickel 0.20
• Silicon 0.30

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Tensile, Compressive, Hardness and Wear Test
Internal Friction Resistivity Metallography
Dilatometry X-Ray Diffraction Photon Induced
Positron Annihilation (PIPA)
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Design of Experiment
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2
4
3
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5
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Austenitize to 2210F in three steps
900,1500,1780F at 15F/minute heating rate
Quench at 20 bar nitrogen
Temper at 1050F for two hours
Cryotreat At 300F in ten hours hold for
twenty hours
Ramp up the temperature to room temperature
within seventeen hours
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Hardness Test
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Compression
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Stress-Strain Plots
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Internal Friction
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Resistivity
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G.R. Speich
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In-Situ Resistivity
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Photon Induced Positron Annihilation
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X-Ray Diffraction
Sr-2
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Dilatometry
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Metallography
Sequence 1
Sequence 4
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10 µm
Sequence 2
10 µ
Sequence 3
10 µm
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10 µm
Sequence 5
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Summary

• Trends are very similar for hardness and yield
  strength

• Resistivity and PIPA also shows similar trends
  for all the sequences

• Thus, the observed property change could be
  linked with the dislocations and carbon
  clustering effect

• Internal friction study suggests higher mobile
  dislocation density for sequence four

• X-ray diffraction indicates presence of retained
  austenite only in as quenched sample whereas
  higher tetragonality for sequence one and
  sequence four

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Combined Results
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Conclusion

• Cryogenic treatment produces more dislocations.
• These dislocations act as nucleation sites for
  clustering which subsequently may get converted
  into very fine carbides. This fact can be
  attributed to the higher binding energy between
  carbon atoms and dislocations.
• Thus, cryogenic treatment is expected to give
  optimum combination of hardness and toughness,
  which could result inincreased tool life.

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Future Work

• Fracture toughness test
• Real wear resistance measurement
• More statistical analysis
• Different heat treatment parameters
• TEM work to observe small carbide clusters
• Quantification of dislocations with PIPA, TEM
  and X-Diffraction
• Integrated research which includes manufacturing
  of actual tools, cryotreatment and then actual
  on-site evaluation of performance.