Suppression of the shadow effect during casting single-crystal superalloys through a central cooling and heating process

Abstract

The “shadow effect” is inevitable when directional solidification technology is employed to fabricate a cluster of large‑caliber castings. It is one of the primary causes of casting defects, resulting in high rejection rates in the Ni-base single-crystal superalloys castings. This study investigates a novel central cooling and heating (CCH) process, which can effectively suppress the shadow effect and improve the yield rate of the castings. The experimental results show that the size of the S‑pores in CCH‑processed castings is reduced, and the freckles are eliminated. During the deformation process, a hexagonal dislocation network forms at the deformed γ/γ′ interface, thereby enhancing the rupture life. In addition, simulation results indicate that the mushy zone width of CCH‑processed castings is shortened by 47.9%, and the temperature field distribution becomes more uniform. Through an in‑depth deduction of the view factor, the radiation heat transfer efficiency is demonstrated, clarifying the level of control over the shadow effect achieved by the CCH process.