Abstract
In this paper, Fe50Mn30Co10Cr10-xNbC (x = 0, 2, 5, and 10 wt.%) high-entropy alloy composites were prepared by Spark Plasma Sintering (SPS) and analyzed by optical microscopy, X-ray diffractometer, scanning electron microscope, microhardness tester and electrochemical workstation. The microstructure, hardness and corrosion resistance were analyzed using optical microscopy, X-ray diffraction, scanning electron microscopy, microhardness tester and electrochemical workstation. The results show that the carbon in the graphene spacer diffuses into the Fe50Mn30Co10Cr10 high-entropy alloy matrix during the SPS sintering process, which inhibits the formation of the dense hexagonal (HCP) phase and makes it consist of a single-sided centered cubic structure (FCC). In addition, the diffused carbon forms a compound of M23C6 ((Fe, Co, Mn, Cr)23C6) at the grain boundaries with Fe, Co and Cr in the alloy of the matrix. the addition of NbC increases the number of nucleation plasmas and refines the grains; the hardness is significantly increased with the increase of NbC content, with the highest value of HV 463 for the sample containing 10 wt.% NbC; The wear resistance first increased and then decreased, where the high entropy alloy with 2 wt.% NbC added had the best wear resistance with a low wear amount of 0.2479 mg; the corrosion resistance first became better and then worse, and the curves of polarization curves and impedance spectra showed that the samples with 5 wt.% NbC added had better corrosion resistance. The corrosion resistance is closely related to the composition and distribution of the compounds at the grain boundaries. When a small amount of NbC is added, the grain boundary precipitation of elemental Cr is suppressed and the corrosion resistance is improved; however, with the enhancement of the continuity of coarse NbC particles precipitating on the grain boundaries and the increase of the carbide content of Cr-rich phase, the corrosion resistance deteriorates rapidly.
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