The influence of melt superheating treatment on the cast structure and stress rupture property of IN718C superalloy

A modified thermally controlled solidification using melt superheating treatment has been designed to an IN718C superalloy to achieve grain refinement and further improve mechanical properties. It is found that the applied melt treatment can refine grain size from 6420 to 89 μm and greatly reduce the amount of porosity from 15.22 to 0.015%. The morphology of the microstructure is evolved from dendritic to granular structure. Meanwhile, the melt superheating treatment has no obvious influence on the dendrite segregation of Cr and Fe, but reduce the dendrite segregation of Nb and Ti. The amount of Laves phase decreases with increasing of melt superheating temperature from 1380 to 1680 °C. Corresponding to this, the stress rupture property under 650 °C/620 MPa is significantly improved.