Effect of scan strategy on the formation of a pure nickel single-crystal structure using a flat-top laser beam via laser powder bed fusion

In this study, the role of a scan strategy in the fabrication of a single crystal (SX) structure of face-centered cubic (fcc) pure Ni using a flat-top laser profile by a laser powder bed fusion (LPBF) process was investigated. A flat-top laser with a uniform heat intensity across the beam profile was employed to fabricate the SX structure with a texture parallel to the build direction (BD). A meander scan strategy with an XY-90 degrees scan rotation was required to achieve the flat-top-derived SX structure. The meander scanning strategy promoted the epitaxial fcc growth along the direction BD, leading to the BD texture formation. Meanwhile, the XY-90 degrees scan rotation induced the epitaxial growth of fcc phase on the hatch direction (HD)-scan direction (SD) plane in the direction deviated by approximately 45 degrees relative to the SD. This 45 degrees deviation relative to the SD occurred to accommodate the beam movement and the circular beam geometry on the HD - SD plane, resulting in the preferred configurations of SD and HD. Thus, this paper reports the importance of meander scanning with a 90 degrees scan-rotation strategy to yield a flat-top-LPBF-derived SX structure with BD and SD and HD textures.