Mechanical and dry sliding tribological properties of CoCrNiNbx medium-entropy alloys at room temperature

Abstract The CoCrNiNbx (x = 0, 0.1, 0.2, 0.3, 0.385, 0.4 and 0.5) medium-entropy alloys (MEAs) were successfully prepared by the arc-melting and casting injection technique. Laves phase and typical lamellar eutectic structure were formed in the Nb-alloyed CoCrNi MEAs. There are three categories of CoCrNiNbx MEAs, i.e., hypo-eutectics (x   0.385). Specially, the eutectic CoCrNiNb0.385 MEA attracts most owing to its full lamellar eutectic structure and brilliant combination of mechanical properties. In tribological properties, the CoCrNiNb0.385 MEA without the highest hardness shows the lowest friction coefficient and wear rate. According to the theory of multilayer films, the most uniform co-deformation between the FCC and Laves phases results in the reduction of friction and wear in the eutectic MEA.