US Patent 9144842 Unidirectional solidification process and apparatus and single-crystal seed therefor

A single-crystal seed, apparatus and process for producing a casting having a single-crystal (SX) microstructure. The seed has a geometry that includes a vertex capable of destabilizing an oxide film that forms at the interface between the seed and a molten metal during the casting process, and thereby promotes a continuous single-crystal grain growth and reduces grain misorientation defects that can initiate from the seed/metal interface.