Densification, microstructure and properties of 91 W-6.3Ni-2.7Fe fabricated by selective laser melting

Abstract

Tungsten is a refractory metal with high density and is widely used in aerospace, medical, and nuclear applications due to its robust performance characteristics. In this study, 91 W-6.3Ni-2.7Fe alloys were fabricated via Selective Laser Melting (SLM). This study delves into the impacts of scanning speed on the densification, microstructure, and mechanical properties of the 91 W-6.3Ni-2.7Fe alloy under the conditions of a laser power of 200 W, scanning pitch of 0.08 mm, and powder layer thickness of 0.03 mm. The investigation demonstrates that an optimal scanning speed of 175 mm/s yields a relative density of 96.89 %, a performance attributed to a balanced energy input that facilitates efficient powder melting and consolidation. This optimized condition further promotes the formation of a microstructure dominated by a high-W phase intertwined with a W-Ni-Fe intermetallic phase, which underpins the alloy's microhardness of 610 HV and tensile strength of approximately 800 MPa. In contrast, higher scanning speeds (≥600 mm/s) introduce reduced energy per unit length, leading to the development of dendritic structures that deteriorate the material’s performance.