Study of the structure and phase composition of a quasi-high-entropy alloy of the Cr-Mn-Ni-Fe-Co-Nb system

The paper presents the results of studying the structure and properties of quasi-high-entropy alloys (QHEAs) of the Cr-Mn-Ni-Fe-Co-Nb system, with the Nb content 0-18 %. These alloys were smelted with partial use of ferroalloys in the charge, which is their feature and determines formation of new phases. For the experimental alloys obtained under the specified smelting conditions and charge composition, the Laves phase and the a phase were not detected. The structure of the studied alloys is represented by the FCC solid solution that includes all the metals, and the niobium content varies widely. In addition, the structure is represented by interstitial phases: niobium carbide NbC0.76-1.0, manganese carbide Mn7C3 and intermetallic CrNi with the cubic lattice. Introduction of niobium in the Cr-Mn-Ni-Fe-Co-Nb system in the amount of 14-16 % leads to increase of hardness, compression strength and wear resistance. The niobium content above 18 % leads to a slight decrease of these parameters, which can be explained by its uneven distribution in the structure. The study shows that the partial use of ferroalloys in the charge makes it possible to obtain alloys of the Cr-Mn-Ni-Fe-Co-Nb system of the QHEA type that have a higher commercial attractiveness due to simplification of the smelting technology and the cost of the charge.