Microstructure and mechanical property comparison of Inconel alloys fabricated using micro and conventional laser powder bed fusion

Abstract

Compared to conventional laser powder bed fusion (c-LPBF), micro laser powder bed fusion (μ-LPBF) offers enhanced capabilities for fabricating complex components with exceptional accuracy. This is achieved through the utilization of a finer laser beam and smaller metal powder, leading to distinct differences in microstructure when compared to c-LPBF. Despite promising outcomes, a comprehensive understanding of these distinctions remains incomplete. One notable observation in the μ-LPBF samples in this study was the presence of a weaker 〈100〉 texture along the build direction. Additionally, these samples exhibited smaller grain sizes, a higher density of low-angle grain boundaries, and the presence of geometrically necessary dislocations. Significantly, μ-LPBF demonstrates the potential to produce IN718 with exceptional isotropic mechanical properties, primarily attributed to its capacity to generate refined microstructures and facilitate distinct solidification behaviors. Of particular significance was the remarkable 39.1 % increase in yield strength observed along the building direction by μ-LPBF. Furthermore, the differences in yield strength and ultimate tensile strength between various directions are notably reduced to 7 and 41 MPa, respectively, with a minimal total elongation variation of only 1.8 %. To gain deeper insights into the solidification behavior, Computational fluid dynamics were conducted in conjunction with the discrete element method.