Additive manufacturing of CoCrFeNiMo eutectic high entropy alloy: Microstructure and mechanical properties

The CoCrFeNiMo eutectic high entropy alloy (EHEA) was fabricated successfully by directed energy deposition (DED). The microstructure and mechanical properties of the CoCrFeNiMo EHEA samples were investigated in this work. Interestingly, the different microstructure morphology and phase composition were shown from bottom to top along the building direction. The seaweed eutectic structure, herringbone-like hierarchical eutectic structure and irregular lamellar structure were observed at the top, middle and bottom parts, respectively, which was due to changes in temperature gradients caused by increasing deposition height. The dominant phases in the CoCrFeNiMo EHEA samples were FCC, σ and μ phases. The FCC phase alternated with the σ phase, and μ phase particles were precipitated from the fringes of the σ phase. Moreover, the CoCrFeNiMo EHEA samples by DED achieved high hardness (658.44 HV) and high wear resistance (the friction coefficient (COF) is 0.586), which were guaranteed by the intermetallic compounds and fine eutectic lamellar structure.