Work

Layerwise scanning strategy combining Multiple beam shapes to enhance isotropy in high-power laser-based powder bed fusion of IN718

Year: 2025

Type: article

Abstract: Beam shaping technology has transformed laser-based powder bed fusion of metals (PBF-LB/M), enabled increased productivity and expanded process window through the use of higher laser power, faster scanning speeds, and wider hatch distances. Unlike state-of-the-art Gaussian laser beam profile, beam shaping with larger beam diameters and higher laser power delivers higher energy input, typically resulting in broader, flatter melt pools. This promotes epitaxial grain growth in alloys like Inconel 718, leading to large columnar grains and significant anisotropy in microstructural and mechanical properties. While such grains enhance high-temperature creep resistance, they adversely affect fatigue performance, tensile strength, and isotropy, which are critical for many applications. This article presents a novel approach, named as “beam switching”, combining layerwise ring-shaped and Gaussian beam profiles to balance productivity and isotropy in as-built parts. With a maximum build rate of 17 mm3/s, four times higher than state of the art (4.2 mm3/s), this method achieves isotropic microstructural properties (texture index represented by J-index of 1.2) without compromising productivity. Detailed microstructural analysis reveals fine, circular grains similar to those produced by state-of-the-art process parameters, resulting in substantial improvements in as-built tensile properties, including ultimate tensile strength and yield strength. This approach further expands the process window by introducing the so-called "healing effect", which transforms previously non-viable process parameters into buildable conditions.

Source: Journal of Materials Research and Technology

DOI: 10.1016/j.jmrt.2025.09.261