Microstructural control in hot working of IN-718 superalloy using processing map

Srinivasan, N and Prasad, YVRK (1994) Microstructural control in hot working of IN-718 superalloy using processing map. In: Metallurgical and Materials Transactions A, 25 (10). 2275 -2284 .

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Abstract

The hot-working characteristics of IN-718 are studied in the temperature range 900 degrees C to 1200 degrees C and strain rate range 0.001 to 100 s(-1) using hot compression tests. Processing maps for hot working are developed on the basis of the strain-rate sensitivity variations with temperature and strain rate and interpreted using a dynamic materials model. The map exhibits two domains of dynamic recrystallization (DRX): one occurring at 950 degrees C and 0.001 s(-1) with an efficiency of power dissipation of 37 pct and the other at 1200 degrees C and 0.1 s(-1) with an efficiency of 40 pct. Dynamic recrystallization in the former domain is nucleated by the delta(Ni3Nb) precipitates and results in fine-grained microstructure. In the high-temperature DRX domain, carbides dissolve in the matrix and make interstitial carbon atoms available for increasing the rate of dislocation generation for DRX nucleation. It is recommended that IN-718 may be hot-forged initially at 1200 degrees C and 0.1 s(-1) and finish-forged at 950 degrees C and 0.001 s(-1) so that fine-grained structure may be achieved. The available forging practice validates these results from processing maps. At temperatures lower than 1000 degrees C and strain rates higher than 1 s(-1), the material exhibits adiabatic shear bands. Also, at temperatures higher than 1150 degrees C and strain rates more than 1 s(-1), IN-718 exhibits intercrystalline cracking. Both these regimes may be avoided in hot-working IN-718.

Item Type:	Journal Article
Additional Information:	Copyright of this article belongs to The minerals, metals & materials society.
Department/Centre:	Division of Mechanical Sciences > Materials Engineering (formerly Metallurgy)
Date Deposited:	18 Apr 2011 06:21
Last Modified:	18 Apr 2011 06:21
URI:	http://eprints.iisc.ernet.in/id/eprint/36641

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