Development of processing strategies for multigraded selective laser melting of Ti6Al4V and IN718

Abstract

In energy generation applications, Ti- and Ni-alloys are widely used for their complementary features, where Ti-alloys provide lightweight structures while Ni-alloys are adaptable to high temperature use. The combination of these alloys into a single component through additive manufacturing is highly desirable. This work explores the multi-material selective laser melting (SLM) of a Ti6Al4V-IN718 material system to produce multigraded specimens. An in-house developed multi-material SLM platform with double hopper and a mixing chamber was employed. A work frame based on studying process feasibility through premixed blends and assessing the processability of multigraded components is presented. Material characteristics, in terms of chemistry, microhardness and microstructure are investigated and supported by thermodynamic calculations. Defect-free grading was achieved until 20 wt% inclusion of IN718 in Ti6Al4V. The results were interpreted to reveal the processability limits of the metallurgically incompatible alloys as well as the defect formation mechanisms.