Microsegregation and Precipitation Behavior during Solidification in a Nickel-base Superalloy

Abstract

Microsegregation and precipitation behavior in a nickel-base superalloy (INCONEL 625) were analyzed using a computer-aided X-ray microanalyzer (CMA). During solidification, (Nb, Ti) C and (Ni, Cr)2(Nb, Mo), called Laves phase, precipitated only in the interdendritic regions due to the microsegregation of the solute elements. The formation of microsegregation and the Laves phase, which causes loss of deformability at high temperatures, could be decomposed by slow cooling. Moreover, raising the cooling rate only during solidification was effective in reducing the amount of the Laves phase, because the dendrite structure became finer. The microsegregation of niobium, titanium and molybdenum was discussed, compared with experimental results and mathematical calculations. © 1990, The Iron and Steel Institute of Japan. All rights reserved.