In-situ Observation of Solidification Process of GH3625 Superalloy at Different Cooling Rates
DING Yutian, DOU Zhengyi, GAO Yubi, GAO Xin, LI Haifeng, LIU Dexue
Key Laboratory of Advanced Processing and Recycling of Nonferrous Metals, College of Materials Science and Engineering, Lanzhou University of Technology, Lanzhou 730050
Abstract: The solidification process of the GH3625 superalloy was in-situ observed at different cooling rates (30 ℃/min, 100 ℃/min and 200 ℃/min ) by means of confocal laser scanning microscope combined with an infrared image furnace. Differential scanning calorimeter (DSC), scanning electron microscope (SEM) and energy dispersive spectrometer (EDS) were adopted to observe the solidified microstructure and the regularity of precipitated phases. The results showed that the liquidus temperature of GH3625 superalloy was 1 356.5 ℃, and the relationship between the variation of solid phase content at the free surface and temperature as well as time was in accordance with Avrami equation. With the decrease of temperature, the precipitation sequence of phases were γ matrix phase, carbides and Laves phase. In the solidification process of GH625 superalloy, with the increasing cooling rate, the dendritic structure refined, the dendrite arm spacing decreased, component segregation reduced, the Laves phase distribution was more dispersed, and mainly precipitated eutectic Laves phase. A large number of Nb segregation occurred in the final period of solidification at the interdendritic and grain boundaries, and this mainly contributes to the formation of Laves phase.
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2017, Vol. 31 
