Laser metal deposition of NbTaTiV refractory high entropy alloy

A mixture of Ti, V, Nb and Ta elemental powders was used to print an equimolar Refractory High Entropy Alloy NbTaTiV. Single beads and wall structures were printed on Ti-6Al-4V substrates. The samples were then cut to analyze their cross-section and composition. The samples present a large proportion of non-melted Ta particles, due to the low max power of the used laser (500W) and of the high melting-point of Ta. It was found that using a two-step deposition process (deposition, followed by a powder-less re-melting pass) could allow to homogenize the samples and melt said Ta particles. Moreover, the authors report difficulty to control the composition of the samples due to the very different physical properties of the different elements composing the alloy, with a preferential deposition of Ta.