The Solidification Microstructure and Carbide Formation Behaviors in the Cobalt-Based Superalloy ECY768
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.
Hyung Sun Kim, Sang-Yeop Park, Bo Young Hur and Soo Wohn Lee
J.S. Lee et al., "The Solidification Microstructure and Carbide Formation Behaviors in the Cobalt-Based Superalloy ECY768", Materials Science Forum, Vols. 486-487, pp. 374-377, 2005