Serrated grain boundary formation potential of Ni-based superalloys and its implications

The serrated grain boundary formation potential of a large number of conventionally forged, powder processed, and investment cast Ni-based superalloys is reviewed. A mechanism of serrated grain boundary formation by which grain boundaryγ′ particles move and displace the local grain boundary segment is discussed and the prerequisite conditions for its occurrence are highlighted. The practical implications of the serrated grain boundary formation are also discussed. It is suggested that modifying the existing heat-treatment cycles in some investment cast and powder processed Ni-based superalloys would improve their properties. The possibility of minimizing weld cracking in superalloys by creating serrated grain boundaries in the base metal and the heat affected zone is also discussed.