Faculty Publications

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    Role of δ-phase on recrystallisation behaviour of Inconel 718
    (SAGE Publications Inc., 2024) Padasale, B.; Potphode, L.; Dsilva, P.C.; Hegde, S.R.
    The present work investigates the annealing behaviour of prior-coldworked Inconel 718 (IN718) sheets over wide reduction and temperature ranges by performing cold-rolling and isothermal annealing, followed by mechanical testing and structural characterisation. The study reveals that, with increasing annealing temperature, the prior-coldworked alloy shows non-monotonic M-Type variation with double peak-hardening at 0.3Tm and 0.6Tm. The study discovers that the first peak is due to the ‘static–strain–aging phenomenon’ that precedes recovery-softening. The second peak-hardening is due to precipitation-hardening, following which, the alloy softens due to recrystallisation. Supported by SEM, electron back-scattered diffraction and X-Ray diffraction results, the investigation suggests that the precipitation of fine rod-shaped δ-phase creates numerous nucleation sites at the shear bands that cause recrystallisation-burst at 0.75Tm. However, above 0.75Tm absence of the δ-phase activates grain-boundary migration resulting in rapid grain-coarsening. © The Author(s) 2024.
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    Effect of Heat Treatment on Microstructure and Dry Sliding Wear Behavior of Laser Directed Energy Deposited Inconel 625
    (Springer, 2025) Praharaj, A.K.; Chaurasia, J.K.; Suvin, P.S.; Narayanan, J.A.; Paul, C.P.; Balla, V.K.; Chakrapani, S.K.; Bontha, S.
    Laser directed energy deposition (LDED) is a promising technology for manufacturing and repair of Inconel 625 (IN625) components used in critical sectors requiring enhanced tribological performance due to harsh operating environments. Hence, the current work focuses on the evaluation of the tribological performance of LDED-built IN625 with the implementation of different heat treatment methods, i.e., solution treatment (ST), direct aging (AG), and solution treatment + aging (ST + AG). A detailed microstructural analysis, hardness, and wear testing were performed for the as-deposited (AD) and heat-treated (HT) samples, and the results were compared. The analysis revealed coarser grains in the case of ST and ST + AG samples, whereas finer grains for AD and AG samples, indicating grain coarsening after solution treatment. Further, the brittle laves phase gets dissolved after ST, whereas the AG and ST + AG samples resulted in the precipitation of metal carbides and strengthening phases. The microhardness of the ST sample (193.2 HV) was lower compared to the AD (211.6 HV) sample, whereas the AG and ST + AG samples exhibited 25.6 and 9.3% higher hardness than the AD sample. Considering tribological performance, the AG sample illustrated a maximum reduction of 61.4% in the coefficient of friction (COF) and 36.5% in wear rate when compared to the AD sample. This could be attributed to the presence of finer grains and strengthening phases. © ASM International 2025.