Influence of process parameters on the quality of powder bed fusion-fabricated Ni-Co-Fe-Mn-Ti high entropy alloy prints using elemental powders

Abstract

Ni-Co-Fe-Mn-Ti high entropy alloys (HEA) were fabricated via powder bed fusion using elemental powders. Based on thermodynamic calculations, 3 alloys were designed with medium to high entropy (from 3 to 5 components) and printed. Additive manufacturing (AM) was performed, while varying the laser power and exposure time (point-by-point exposure laser working mode). The obtained samples were characterised by means of macroscopic observations combined with porosity analysis, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), electron backscatter diffraction (EBSD), X-ray diffraction (XRD), as well as compression and hardness tests. The varied process parameters and the content of individual alloying elements directly impacted alloy processability and sample properties. We proved that it is possible to produce HEAs (Ni-Co-Fe-Mn-Ti) with low porosity and good chemical homogeneity from elemental powders. By comparing the processes of producing 3-, 4-, and 5-component alloys, it was observed that it is not the quantity of the components but the melting temperatures of the individual elemental powders and their tendency to oxidise that affect obtaining good 3D prints. The most promising results for 5-component HEAs were obtained for 145 µs of laser exposure time combined with laser powers of 250 and 300 W.