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

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), eutectics (x = 0.385) and hyper-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.

Automated summary

The CoCrNiNbx medium-entropy alloys were successfully prepared via arc-melting and casting injection technique, displaying different categories and properties. Among them, the CoCrNiNb0.385 MEA is attracting attention for its full lamellar eutectic structure and excellent mechanical properties. In terms of tribological properties, this material exhibits the lowest friction coefficient and wear rate, attributed to uniform co-deformation between FCC and Laves phases in the eutectic MEA.