Different aspects of heat treatment of nickel base alloys. property variation with heat treatment.

1. HEAT TREATMENT OF
NICKEL BASE
ALLOYS
JABIN MATHEW BENJAMIN
13MY04

2. Nickel (Ni)
• Good resistance to corrosion and oxidation
• Poor conductivity compared to Al and Cu
• Alloyed with Cu, Fe, Cr, Mo, Si.
• Alloys – Inconel, Monel, Hastealloy
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3. Factors Influencing Heat Treatment
Of Ni
• Effect of prior cold work.
• Greater the cold work before annealing  the lower the temperature of
recrystallization  shorter the time required at any one temperature.
• Influences the ductility of nickel and nickel alloys after annealing.
• Small amount of cold work (for example, ~10% reduction), full
ductility cannot be restored by annealing.
• Minimum 20% cold working between anneals ensure maximum
ductility and softness.
• Effect of cooling rate.
• No specific effect on the softness of the annealed nickel materials
• Rapid cooling preferable: Time-saver and to minimize the amount of
oxidation.
• Except for heavy sections - may set up excessive thermal stresses
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4. • Control of grain size.
• Coarse-grained material unsuitable for cold-working
• Coarse grain removed only by cold working and subsequent
annealing treatment.
• Optimum average grain diameter:0.064 mm (0.0025 in.)
(ASTM no. 5).
• Combination of ductility to permit extensive deformation,
strength to withstand the action of tools, and surface quality
to facilitate polishing.
• Effect of atmospheres.
• Susceptible to oxidation under oxidizing atmosphere
• Sufficient excess of reducing atmosphere during heating and
cooling.
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5. • Protection from contamination by foreign material.
• Lubricants used for deep drawing contain sulfur or lead 
unless removed before annealing, they will cause
embrittlement
• Affected material cannot be reclaimed
• Contaminated area must be either removed or scrapped
• Lubricants, paints etc of any type should be removed
entirely from the material before annealing.
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6. Heat treatment
• Annealing
• Stress relieving
• Stress equalizing
• Solution treating
• Age hardening
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7. Annealing
• To produce recrystallized grain structure
• Softens the work hardened alloys
• Temp: 700oC to 1200oC
• Depends on alloy composition and extent of work
hardening
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8. Stress Relieving
• Done to minimize residual stress
• For work hardened and non-age hardenable alloys
• No recrystallization
• Temp: 430oC to 870oC
• Depends on composition
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9. Stress Equalizing
• Low temperature heat treatment
• Balances stresses in cold worked metal or alloy
without affecting the mechanical properties
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10. Solution Treating
• For age hardenable alloys before ageing
• To diffuse age hardening constituents and carbides
into solid solution
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11. Age Hardening
• Temp: 430oC to 870oC
• To obtain maximum strength by precipitation of a
dispersed phase in the matrix
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12. Nimonic
• 20% Cr, 18% Co, 2.5% Ti, 1.5% Al, 0.05% C
• 8-12 hours at 1080- 1180oC then air cooled
• 12-16 hours at 700-850oC and aircooled
• Supersaturated γ solution with a FCC lattice forms
• On ageing γ solid solution decomposes and a fine
precipitate of γ’ phase of Ni(Al) forms
• On longer ageing at 850-900oC stable η phase Ni3Ti
forms- hexagonal type and may cause embrittlement
• γ solid solution has a high recrystallization temperature
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13. Inconel
• 15% Cr, 6.75% Fe, 2.5% Ti, 0.8% Al, 0.85% Co
• 2-4 hours at 1165oC  Air cooling
• 24 hours at 860oC Air cooled then 20 hours at 740oC
air cooled
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14. Hastealloy
• 1% Cr, 2.5% Co, 23-30% Mo, 2.6% V, 1% Si and
Mn, 0.05% C.
• 1200oC for 1 hour then air cooled
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15. Waspalloy
• 19.5% Cr, 13.5% Co, 2% Fe, 4.25% Mo, 1.3% Al,
3% Ti, 0.1% C
• 4 hours at 1100oC then air cooled
• 24 hours at 860oC then air cooled
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16. THANK YOU
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