Abstract

The conventional Bridgman process for fabricating single-crystal superalloy castings is constrained by low temperature gradient and coarse dendrite structures. In this study, a novel conformal insulation technique was devised to overcome these limitations. The approach involved incorporating insulation materials within the central region of the ceramic shell cluster and applying conformal insulation plates to the mold periphery, effectively suppressing furnace heat loss and enhancing the temperature gradient during solidification. The numerical simulations and experimental casting trials on both single-crystal rods and turbine blades were carried out. It was found that this new technique could more than double the attainable temperature gradient. As a result, the morphology of the solid–liquid interface evolved from inclined to planar, the extent of the mushy zone was substantially reduced, and dendrite refinement within the single-crystal castings was significantly promoted. These results demonstrate the effectiveness of the proposed process in improving the structure control and overall quality of single-crystal superalloy castings.

Keywords:Superalloy; Single crystal; Directional solidification; Temperature gradient; Dendrite refinement