STUDY OF THE EFFECT OF MOLYBDENUM ON THE PROPERTIES OF THE Co-Cr-Fe-Ni-Mn-Nb QHEA

This study investigates the effects of varying molybdenum concentrations (5 %, 10 %, and 15 %) on the microstructural features, hardness, and melt fluidity of quasi-high-entropy alloys (QHEAs) within the Co-Cr-Fe-Ni-Mn-Nb system. The primary objective is to reduce production costs of advanced alloys by partially replacing pure elemental constituents with ferroalloys. Experimental ingots were synthesized via induction melting, followed by characterization through scanning electron microscopy (SEM), Brinell hardness testing, and spiral fluidity assessments. Results indicate that increasing Mo content markedly enhances hardness – approaching a threefold increase at 15 % Mo – attributable to solid-solution strengthening and probable intermetallic phase formation. However, elevated molybdenum levels negatively affect melt fluidity, with a reduction of approximately 12 % observed at Mo contents between 10 % and 15 %, leading to casting defects. These findings emphasize the importance of optimizing molybdenum concentration to achieve an optimal balance between mechanical performance and castability. For components with complex geometries, maintaining Mo content below 10 % is advisable. This work contributes to the development of cost-effective QHEAs suitable for precision casting using locally sourced materials. Keywords: quasi-high-entropy alloy, melt fluidity, molybdenum, hardness, microstructure, casting, ferroalloy.