Microstructure, mechanical properties, and wear behavior of AlCoCrFeNi high-entropy alloy and AlCrFeNi medium-entropy alloy with WC addition

AlCoCrFeNi is one of the early studied high-entropy alloys (HEAs), attracting considerable attention due to its attractive mechanical properties. Efforts have been continuously made to improve properties of the HEA by modifying its composition. In this study, WC particles were added to AlCoCrFeNi alloy with different percentages (10, 30 and 60 wt%) using an arc furnace. Since medium-entropy alloys with fewer elements may also possess attractive properties with less structural complication, we also added WC to the Co-free medium-entropy alloy, AlCrFeNi, in comparison with its high-entropy HEA companion. Microstructure, mechanical properties and re-sistances against wear, corrosion and corrosive wear of the WC-added alloys were investigated. It was shown that the added WC decomposed and formed in situ carbides. The WC-added AlCrFeNi is harder with a higher wear resistance than the WC-added AlCoCrFeNi. Both the alloys consist of a BCC matrix and carbides in a eutectic state. With increasing the WC content, hardness and wear resistance of the alloys increased. The medium-entropy alloy AlCrFeNi showed better performance than AlCoCrFeNi. For comparison, Co-WC composite alloy was also prepared using the arc furnace. The wear volume loss of AlCrFeNi-60 wt%WC was only half that of Co-60 wt% WC under the same wearing condition. The Co-containing alloy, e.g., AlCoCrFeNi+60WC, showed its corrosion resistance lower than that of Co-free AlCrFeNi-60 wt%WC, mainly due to its lower %Cr. The addition of WC significantly reduced the volume loss caused by corrosive wear in the 3.5 wt% NaCl solution for both alloys as a result of improved hardness.