Solidification Process and Behavior of Alloying Elements in Ni-Based Superalloy Inconel718

抄録

The thermal and metallographic analysis of Inconel718 alloy revealed that the solidification proceeds in the order of primary γ at 1615 K, (γ + NbC) eutectic at 1561 K, and (γ + Ni₂Nb) eutectic at 1452 K. Additional equilibrium evaluation performed using Thermo-Calc predicts the following solidification sequences: primary γ at 1633 K, followed by (γ + NbC) eutectic at 1555 K. The (γ + Ni₂Nb) eutectic phase does not appear in the equilibrium calculation, indicating that the (γ + Ni₂Nb) phase crystallizes as a non-equilibrium eutectic phase. The partition coefficients of alloying elements in the primary γ and eutectic phases were also determined experimentally (k_(Exp.)) and compared with the values calculated using Thermo-Calc (k_(T-C)). The behaviors of alloying elements during solidification were estimated using k_(Exp.) and k_(T-C) in various solidification models. It was found that the results of the experiments are in agreement with the calculations obtained using the Clyne-Kurz model.