High throughput synthesis of CoCrFeNiTi high entropy alloys via directed energy deposition

Blown-powder additive manufacturing process, directed energy deposition (DED) is applicable to scale-up material development with cost-effective elemental powder mixtures. In this paper, the effectiveness of applying DED to the design and synthesis of model CoCrFeNiTi high entropy alloys (HEAs) was demonstrated. Through a careful design of composition and delicate selection of particle size and shape, three CoCrFeNiTi HEAs with different microstructures were in-situ synthesized from premixed elemental powders. Transmission electron microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction were used for microstructure characterization. H3-Co24.4Cr17.4Fe17.5Ni24.2Ti16.5 in at% (close to Co1.5CrFeNi1.5Ti) was fabricated with a soft face-centered cubic (FCC)-gamma phase structure while hard intermetallic phases such as sigma-FeCr, delta-NiTi2, and a small amount of Ni3Ti2 were precipitated and uniformed distributed in the FCC matrix for H1-Co22.2Cr16.1Fe19Ni21.8Ti20.9 and H2-Co25.9Cr15Fe17Ni20.8Ti21.3. With a large percent of the secondary phases, H1 exhibited a hardness value of about 853 HV0.5. These HEAs displayed a high oxidation resistance comparable to Inconel 625 superalloy. A detailed evaluation of the composition, microstructure, hardness, oxidation resistance, and wear resistance of these HEAs was conducted as compared with those of a reference HEA and two popular wear-resistant steels. (c) 2022 Elsevier B.V. All rights reserved.