Investigation of Solidification Behavior in a New High Alloy Ni-Based Superalloy

Abstract

While solidification behavior has been investigated in several nickel-based superalloys, few investigations have focused on the meticulous study of solidification behavior in such a highly alloyed and high γ′ volume fraction-containing alloy as GH4151. In this study, several material characterization techniques were employed to identify phase types, illustrate the morphology of precipitates, and detect composition characteristics. In addition, differential scanning calorimeter and isothermal solidification quenching experiments were used to explain the solidification sequence. It has been confirmed that (Nb,Ti)C carbides, η phase, eutectic (γ + γ′), Laves, Ni5Ce, and γ′ phase were found in the as-cast GH4151. The solidification sequence was determined as follows: L → L + γ → L + MC → L + η → L + (γ + γ′) → L + Laves → L+Ni5Ce, and γ → γ′. Combined with electron probe micro-analysis, the results show that Nb, Ti, Mo, and V are significantly enriched in the interdendritic region, which has elemental degrees of segregation such that Nb > Ti > Mo > V, while Al, Co, Cr, W, and Ni are enriched within the dendritic arms, whose degree of segregation is W > Al > Ni > Co > Cr.