Bulk single-crystal-like IN738 alloy fabricated using laser powder bed fusion by controlling the thermal flow

This study demonstrates the fabrication of a bulk crack-free superalloy specimen with a predominantly {001} <100> single-crystalline-like texture using laser powder bed fusion (LPBF). Laser modulation produced a uniform temperature gradient at the solid–liquid interface along the build direction. The formation of stray grains was suppressed by reducing the melt flow velocity and enhancing the stability of the melt pool. Interlayer orthogonal scanning ensured that the lateral heat flow in the horizontal plane was parallel to the [100] and [010] crystal orientations, thereby suppressing high-angle grain boundaries. Thus, the largest-sized single-crystal-like IN738 alloy built by LPBF to date was achieved. Establishing thermal flow stability as a new paradigm, this work achieves the largest crack-free IN738 bulk (10 × 10 × 40 mm³) with sustained {001}<100> epitaxial growth via laser-modulated LPBF without single-crystal substrates and resolving cracking susceptibility.