Seung-Hun Kang1,, Yuho Deguchi1,\footnotemark, Kaoru Yamamoto2, Keisaku Ogi2 and Makoto Shirai3
1Department of Materials Science and Engineering, Graduate School of Engineering, Kyushu University, Fukuoka 812-8581
The thermal and metallographic analysis revealed that the solidification of Inconel 718 alloy proceeds in order of primary γ at 1615 K, γ/NbC eutectic at 1561 K, and γ/Ni2Nb eutectic at 1452 K. On the other hand, equilibrium evaluation using Thermo-Calc expresses the following solidification sequences; primary γ at 1633 K, followed by γ/NbC eutectic at 1555 K. The γ/Ni2Nb eutectic phase doesn't appear in the equilibrium calculation, indicating that the γ/Ni2Nb phase crystallizes as non equilibrium eutectic phase.
The partition coefficients of alloying elements to primary γ and eutectic phases were also determined experimentally (k(Exp.)) and compared with the values estimated with Thermo-Calc (k(T-C)). The behaviors of alloying elements during solidification were estimated by using k(Exp.) and k(T-C) on the Clyne-Kurz model. It was found that both of them are in a good agreement.
(Received July 7, 2003)
solidification, nickel-based superalloy, partition coefficient, Thermo-Calc, segregation
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