Mechanical characteristics and electrochemical corrosion of NiCoCr alloys

Abstract

Previous studies have shown that NiCoCr medium entropy alloys (MEAs) have perfect strength-ductility balance and significant escape fracture toughness. This work aimed to determine the effects of annealing temperature and alloy composition on the mechanical characteristics and corrosion behaviors of the NiCoCr MEAs. The results showed that the grains generated in the NiCoCr MEAs became more petite with the cooling rate increasing. The Vickers hardness (HV) of annealed NiCoCr MEAs increased with increasing annealing temperature. For NiCoCr alloys with different alloy compositions, the potentiodynamic polarization results showed that the NiCoCrFeMn alloy has the highest polarisation resistance, lowest current density, and lowest corrosion rate. However, the composition of Fe2O3-based passivation film makes it highly reactive and easily cleaved by Cl-. The NiCoCr and NiCoCrFe MEAs with high Ni content had a denser and slowly dissolved NiO passivation layer and better corrosion resistance. Moreover, the hardness of corroded NiCoCr MEAs decreased by 7.7 %.