In investment casting, a single crystal orientation within the casting is typically created via a helix or pigtail from the starter block when there are only primary grain control requirements. However, when both primary and secondary grain control requirements exist, a seed is traditionally used. Effective seed meltback can be defined as when the master alloy and the starter seed dendrite structures mesh after pour and prior to withdrawal creating an ample mushy zone which is sufficient for the seed crystallographic orientation to survive and replicate into the final casting.

In order to investigate this sufficient seed meltback, a design of experiment was performed. This DOE consisted of processing molds while varying the starter seed geometry, the hold time post pour pre-withdrawal during cast, and the mold superheat temperature pre-pour. For each variable, three different parameters were chosen.

Characterization techniques included ProCAST solidification simulation, thermocouple data acquisition from cast molds, grain etch, and X-ray diffraction via Laue. In addition, microscopic samples of the seeds post cast were made in order to analyze the size and effectiveness of the seed meltback region.