Powder plasma arc additive manufacturing of CoCrFeNiWx high-entropy alloys: Microstructure evolution and mechanical properties

Powder plasma arc additive manufacturing (PPA-AM) is a promising method for the preparation of high-entropy alloys (HEAs), and has the advantages of low cost, high efficiency, and high quality. In this study, the CoCrFeNiWx (x = 0, 0.2, 0.5, 0.7, and 1.0) HEAs were successfully prepared via the PPA-AM technique. Microstructure and mechanical properties of alloys with different W content were investigated. The results showed that the microstructure changed from a single FCC phase (x = 0) to the dual-phase FCC + µ (x = 0.2 and 0.5), and then to a three-phase combination of FCC + µ + BCC (x = 0.7 and 1.0) with the addition of W. The volume fraction of the µ phase and BCC phase increases with the increase in W content, while the size of FCC columnar grain is significantly reduced. The solid-solution strengthening of the FCC phase and the second phase strengthening were mainly responsible for the increase in the microhardness (136–413 HV) and yield strength (187–567 MPa) while the brittleness of the μ phase contributes to the expansion of the crack, which leads to a decrease in the ductility (50.8% to 0.3%). These results can provide a systematic understanding of the phase transformation of PPA-AM HEAs with different W content and its effects on the mechanical properties.