Structure-property correlation of a CoCrFeNi medium-entropy alloy manufactured using extreme high-speed laser material deposition (EHLA)

Abstract

A near-dense and crack-free CoCrFeNi medium entropy alloy (MEA) coating was fabricated using extreme-high-speed laser material deposition (EHLA). The ultra-low local heat input associated with the EHLA process benefitted in attaining minimal dilution and heat-affected zone. The MEA coating retained the single-phase face-centered cubic (FCC) phase structure associated with the original powder feedstock without any evidence of elemental segregation. The coating exhibited a “bonfire”-like clustered fine grain structure near the substrate interface with the large columnar grains in the subsequent layers further from the substrate. Anisotropic mechanical deformation behaviour was observed at a localized level, but homogenous mechanical properties were evidenced by microstructure-mechanical property correlations at the bulk level. The EHLA process offers exciting possibilities for the development of next-generation dense and crack-free coatings for extreme engineering applications.