MECHANICAL PROCESSING AND MICROSTRUCTURAL CONTROL IN HOT-WORKING OF HOT ISOSTATICALLY PRESSED P M IN-100 SUPERALLOY/

The hot deformation behavior of hot isostatically pressed (HIPd) P/M I N-100 superalloy has been studied in the temperature range 1000-1200 d egrees C and strain rate range 0.0003-10 s(-1) using hot compression t esting. A processing map has been developed on the basis of these data and using the principles of dynamic materials modelling. The map exhi bited three domains: one at 1050 degrees C and 0.01 s(-1), with a peak efficiency of power dissipation of approximate to 32%, the second at 1150 degrees C and 10 s(-1), with a peak efficiency of approximate to 36% and the third at 1200 degrees C and 0.1 s(-1), with a similar effi ciency. On the basis of optical and electron microscopic observations, the first domain was interpreted to represent dynamic recovery of the gamma phase, the second domain represents dynamic recrystallization ( DRX) of gamma in the presence of softer gamma', while the third domain represents DRX of the gamma phase only. The gamma' phase is stable up to 1150 degrees C, gets deformed below this temperature and the chunky gamma' accumulates dislocations, which at larger strains cause cracki ng of this phase. At temperatures lower than 1080 degrees C and strain rates higher than 0.1 s(-1), the material exhibits flow instability, manifested in the form of adiabatic shear bands. The material may be s ubjected to mechanical processing without cracking or instabilities at 1200 degrees C and 0.1 s(-1), which are the conditions for DRX of the gamma phase. (C) 1998 Elsevier Science S.A. All rights reserved.