The Solidification Microstructure and Carbide Formation Behaviors in the Cobalt-Based Superalloy ECY768

Abstract:

Co-base superalloys have been applied in the stationary compoents of gas turbine owing to their excellent high temperaure properties. The stationary Co-base alloy components are generally manufactured by casting. Solidification behavior of the alloy is an important factor in the selection of casting parameters. In the present study, solidification microstructure and carbide formation behaviors were studied by directional solidification. Directional solidification experiments were carried out at the solidification rates of 0.5 ~ 150µm/s with the Co-base superalloy ECY768. Between the dendrites just below the final freezing temperature, MC carbide and M23C6 carbide were found. It was identified that the script or blocky carbides were Ta or W-rich MC carbide, and the lamellar carbides were Cr-rich M23C6 eutectic carbides. The solid/liquid interface morphology clearly showed that freezing of the Cr-rich eutectic carbide occurred just after the script type MC carbide.

• Periodical: Materials Science Forum (Volumes 486-487)
• Pages: 374-377
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.486-487.374
• Online since: June 2005
• Authors: J.S. Lee, Je Hyun Lee, Baig Gyu Choi, Chang Yong Jo, Ung Yu Paik, S.G. Gang
• Keywords: Carbide, Co-Base Superalloy, Directional Solidification, Solidification Rate

References

[1] ASM Specialty Handbook, Heat-Resistant Materials, ASM Inter. (1977).

[2] ASM Specialty Handbook, Nickel, Cobalt and Their Alloys, ASM Inter. (2000).

[3] Charlie R. Brooks, Heat Treatment, Structure and Properties of Nonferrous Alloys, US (1982).

[4] C. T. Sims, N. S. Stoloff and W. G. Hagel, Superalloys II, John Wiley & Sons (1987).

[5] J. H. Lee and J. D. Verhoeven, Journal of Phase Equilibria, 15(2), 136 (1994).

[6] S. R Dharwadkar, K. Hilpert, J. Schubert and V. Venugopal, Zeitshrigt fur Metallkunde, 9, 744 (1992).

[7] D. H. Ye, H. C. Kim, J. H. Lee, Y. S. Yoo and C. Y. Jo, Korean Journal of Materials Research, 12(12), 897 (2002).

[8] J. S. Bae, H. C. Kim, J. H. Lee, Y. S. Yoo and C. Y. Jo, Koran Journal of Materials Research, 11(6), 50 (2001).

[9] J. H. Lee, S. M. Seo, D. H, Kim, S. J. Choe and H. M. Kim, Liquid Metal Processing & Casting, American Vacuum Society, 54 (1999).

[10] H. C. Kim, J. H. Lee, S. M. Seo, D. H. Kim and C. Y. Jo, Korean Journal of Materials Research, 11(9), 721 (2001).

[11] J. D. Verhoeven, Fundamentals of Physical Metallurgy, John Wiley & Sons (1987).

[12] M. McLean, Directionally Solidification Material for High Temperature Service, The Metals Society (1983).