EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

The main aim of this study is to understand the printability, phase stability, microstructure and resulting mechanical properties of the high entropy alloys using laser powder bed fusion (L-PBF). High entropy alloys (HEAs) are a novel class of alloys which contain multiple principal elements in near equiatomic proportions. The unprecedented compositional complexity has reportedly enabled HEAs to perform better than conventional alloys in various situations. Preparing HEAs using additive manufacturing techniques such as L-PBF helps in reducing the phase segregation and preventing the formation of detrimental phases, owing to the very high solidification rates. In this study, pre-alloyed gas atomized powders of CoCrNi medium entropy alloy were used for the L-PBF process, and the influence of various printing parameters on the densification and its resulting phase stability, microstructure and mechanical properties were investigated. CoCrNi showed excellent printability with a broad parametric window with densities greater than 99.9%. The printed parts were then characterized using X-ray diffraction and EBSD which proved the stabilization of single phase fcc and no detrimental phases were observed. Microstructural examination on the printed parts showed the epitaxial growth of grains in the build direction with a cellular solidification structure owing to the complex solidification conditions induced by the L-PBF processing parameters. The resulting mechanical properties of the CoCrNi medium entropy alloy showed improvement compared to its as-cast counter parts. The tensile test results showed anisotropy in the different building directions which could be attributed to the anisotropy in microstructure in different building directions.