Directional Solidification Microstructure Control in CM247LC Superalloy

Directional solidification of the superalloy CM247LC has been carried out to investigate the microstructural evolution under various solidification conditions. It can be clearly seen that the solid/liquid interface morphology depends primarily on the growth rate and temperature gradient. The planar interface was stable at low velocities and the increased velocity encouraged the development of dendritic interface. As a result, the conditions for the planar to cellular transition and the cellular to dendritic transition were obtained and therefore the solidification microstructure map was constructed based on these results. The experimental results were in good agreement with theoretical predictions for this alloy. However, the condition for the dendritic to equiaxed transition was discussed in the light of the heat balance at the solid/liquid interface.