Abstract

The γ/γ’-eutectic structure in the single crystal blade castings of superalloy CMSX-4 was examined. It was observed that the as-cast eutectic in the airfoil region was uniformly distributed and could be nearly completely eliminated during solution heat treatment. In the platform, however, significant difference in the eutectic appearance between top and bottom surface was detected. The as-cast eutectic in the top region was measure to be several times more than that at the bottom. Even after standard heat treatment, there is still a number of residual eutectic remaining undissolved at the platform top. This phenomenon, called as upward accumulation of eutectic structure, is attributed to the upward transmission of γ′-forming elements by means of diffusion and convection, resulting in an eutectic concentrated region at the top of the casting part.

Keywords:Superalloy; Single crystal; Blade casting; Eutectic; Upward accumulation