Orientation controlling of Ni-based single-crystal superalloy by a novel method: grain selection assisted by un-melted reused seed

Abstract

A new grain selection method assisted by un-melted short seed was proposed to control the primary and secondary orientations of Ni-based single-crystal superalloy. The results showed that the use of short seeds could effectively avoid the formation of the melt back mush zone. Although a few stray grains were formed at the upper of the short seed because Al2O3 and SiO2 particles might act as nucleation sites, an expected grain with the smallest misorientation was predominant in starter block. Finally, the orientations of the Ni-based single crystal superalloy component could be not only well controlled with a smaller misorientation about 2.1°, but also a paper-thin substance mixed Al2O3 and SiO2 particles was partly covered with the surface of the un-melted short seed, which made this seed convenient to separate and reuse resulting in the reduction of cost. Keywords: Directional solidification, Ni-based single crystal superalloys, Grain selection, Orientation