Comparison of microstructure and properties of CoCrFeMnNi high-entropy alloy from selective laser melting and directed energy deposition processes

Abstract

Selective laser melting (SLM) and directed energy deposition (DED) methods were used to prepare CoCrFeMnNi high entropy alloy (HEA) coupons with pre-alloyed powders. The process parameters of SLM and DED methods were selected so that porosity level in the deposited materials is close to zero. It was found that both DED and SLM samples consist of a single-phase FCC, and the microstructure is dominated by columnar grains spreading over several layers along the deposition direction. Small deviation from equiatomic composition was observed in both samples with Cr being about 2.3 and 2.7 at% in excess while Co being in depletion for DED and SLM samples, respectively. On the other hand, spherical shape Mn oxides were found at the top region of the DED sample only, while lack of fusion (LOF) and balling defects were observed in the SLM sample. Also, the grain growth orientations appear to be different for the two processes. The average grain size of DED-produced material is twice that of SL-produced material. The average microhardness values of DED and SLM samples were 221.5 ± 11.9 and 237.2 ± 6.5 HV0.1 respectively.