Clear path to the directional solidification of Ni-based superalloy CMSX-10: A peritectic reaction

• CMSX-10 was directionally solidified and quenched at different solid fractions.
• The solidification path was decidedly clarified.
• A 3D model was proposed to represent interdendritic colonies.
• Evidence suggests solidification in the interdendritic region of peritectic nature.

The solidification path of directionally solidified Ni-based superalloys is an important feature to define the heat treatments necessary after casting. Ni-based superalloy CMSX-10 was solidified at different velocities in a modified Bridgman type furnace allowing rapid quenching of the samples in water. The results of the experiments allowed to clarify the solidification of the interdendritic region, from nucleation of fine γ′ precipitates at the primary γ dendrite surface to the spatial growth and coarsening of the interdendritic colonies' morphology towards the end of solidification. A three-dimensional model is proposed and explains the different morphologies in the interdendritic region according to the observation plane. The study revealed strong evidence of a solidification in the interdendritic region of peritectic nature. Solute rejection into the liquid ahead of the growing phases, diffusion and convection effects lead to the coupled growth of the γ and γ′ phases according to the reactions L → γ and L + γ → γ′ respectively.