Epitaxial Grain Growth and Texture Evolution Controlled by Hatch Spacing in Flat-Top Laser Powder Bed Fusion of a Ni–8Al Superalloy

Abstract The influence of hatch spacing on epitaxial grain growth and crystallographic texture evolution was investigated in flat-top laser powder bed fusion (LPBF) of a Ni–8Al superalloy. Laser scanning was performed bidirectionally with alternating hatch directions (HDs) of 0 deg and 90 deg between layers, forming droplet-shaped melt pools. At the melt pool center, grains grew epitaxially from the flat pool bottom along the build direction (BD). In the lateral–tail regions, grains followed trajectories inclined ~ 45 deg toward the melt pool center in the scan direction (SD) and ~ 45 deg upward toward the BD. A small hatch spacing promoted epitaxial growth from a melt pool side toward the center. This mode was associated with ± 45 deg rotations about a $$\langle 110\rangle$$ ⟨ 110 ⟩ axis parallel to the BD, induced by the bidirectional scanning. Consequently, a dominant $$\langle 110\rangle$$ ⟨ 110 ⟩ texture developed along the BD, accompanied by a strong $$\langle 111\rangle$$ ⟨ 111 ⟩ texture along the SD and HD. As the hatch spacing increased, deflection caused by the lateral boundary of the adjacent melt pool diminished. This reduction favored $$\langle 100\rangle$$ ⟨ 100 ⟩ -oriented epitaxial growth along the BD, increasing the $$\langle 100\rangle$$ ⟨ 100 ⟩ texture intensity and decreasing the $$\langle 110\rangle$$ ⟨ 110 ⟩ texture intensity. On the SD/HD–BD plane, texture components dispersed. These results indicated that the hatch spacing regulates the melt pool interaction and the epitaxial growth continuity, thereby governing crystallographic texture evolution in flat-top LPBF.