Abstract
The Inconel 718 superalloy was subjected to isothermal and cyclic thermal annealing at 750°C to assess its expected use at higher temperatures. Mcrostructure evaluation during isothermal annealing and thermal cycling was investigated by different imaging techniques. According to High Resolution Scanning and Transmission Electron Mcroscopy (HRSEM & HRTEM) results, all the annealed samples showed the coarsening of γ′, γ″ and δ precipitates, however, the total volume fraction of these precipitates remains the same for all heat treatment conditions. Using backscattered electrons images the size of γ′, γ″ and δ phases were measured and correlated with annealing time. The most striking result is the impact of thermal cycling which accelerates the growth inside the grains of γ″ phase and at the vicinity of the grain-boundaries leading to its transformation to δ phase, which induces a fast decrease of the mechanical properties of thermally cycled specimens compared to isothermally aged ones. A close investigation showed that the γ″ phase grows by ledge mechanism. Moreover, Electron backscattered diffraction analysis (EBSD) revealed no significant grain size change during all annealed times.
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References
R. Cozar, and A. Pineau, “Morphology of γ′ and γ″ precipitates and thermal stability of inconel 718 type alloys,” Metall. Trans., 4 (1973), 47–59.
J. Zhao, J. H. Westbrook, and G. Editors, “Ultrahigh- Temperature Materials for Jet Engines,” MRS Bull., 2003, 28.
D. F. Paulonis, and J. J. Schirra, “Alloy 718 at Pratt & Whitney-Historical Perspective and Future Challenges,” Superalloys, 2001, 13–23.
E. A. Loria, “The Status and Prospects of Alloy 718,” J. of Metals, 40 (7) (1988), 36–41.
L. Renhof, et al., “Analysis of Mcrostructural Properties of IN 718 After High Speed Forging,” Superalloys 718, 625, 706 and Derivatives, TMS, 2005, 261–270.
S. J. Hong, W. P. Chen, and T. W. A. Wang, “Diffraction study of the γ″ phase in Inconel 718 superalloy,” Metall. Mater. Trans. A, 32 (2001), 1887–1901.
X. S. Xie, J. X. Dong, and M. C. Zhang, “Research and Development of Inconel 718 Type Superalloy,” Materials Science Forum, 539–543 (2007), 262–269.
D. D. Krueger, “The development of direct aged 718 for gas turbine engine disk applications Superalloy 718,” Metallurgy and Applications, TMS, (1989), 279–296.
Y. C. Fayman, “Mcrostructural characterization and elemental partitioning in a direct-aged superalloy DA 718,” Mater. Sci. Eng., 92 (1987), 159–171.
T. Matsui, “Dynamic Recrystallization Behavior of Waspaloy during Hot Working,” Mater. Trans., 55 (2014), 255–263.
S. Mannan, S. Patel, and J. De Barbadillo, “Long term Thermal stability of Inconel alloys 718, 706, 909, & Waspaloy at 593 oC and 704 oC,” www.specialmetals.com, 2010, 10.
C. Slama, and M. Abdellaoui, “Structural characterization of the aged Inconel 718,” J. Alloys Compd., 306 (2000), 277–284.
Y. F Han, P. Deb, and M. C. Chaturvedi, “Coarsening behaviour of γ″ & γ′ particles in Inconel alloy 718,” Metal Science, 16 (1982), 555.
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Devarapalli, R.S., Marin, E., Cormier, J., Le Gall, C., Franchet, JM., Jouiad, M. (2016). Microstructure Evolution during Thermal Aging of Inconel 718. In: Ikhmayies, S.J., et al. Characterization of Minerals, Metals, and Materials 2016. Springer, Cham. https://doi.org/10.1007/978-3-319-48210-1_2
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DOI: https://doi.org/10.1007/978-3-319-48210-1_2
Publisher Name: Springer, Cham
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