Development and Characterization of MoSi₂-Added (HfZrTaTiW)C-Based Composites

Abstract

High-entropy carbides (HECs) have recently attracted considerable attention due to their exceptional thermal and mechanical stability. However, the compositional design of these systems has mostly focused on monolithic structures or variants reinforced with silicon carbide (SiC). In this study, molybdenum disilicide (MoSi₂) was incorporated into a high-entropy carbide matrix for the first time. This novel approach significantly improved both microstructural uniformity and mechanical performance. An equimolar (HfZrTaTiW)C system and its SiC and MoSi2 containing composites were synthesized through high-energy ball milling followed by spark plasma sintering (SPS). The applied two-step SPS schedule effectively promoted carbothermal reduction, leading to the formation of a dense, single-phase rock-salt structure. X-ray diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDS) analyses revealed that Mo atoms derived from MoSi₂ were successfully incorporated into the multicomponent carbide lattice rather than forming a separate silicide phase. This incorporation caused a slight lattice contraction accompanied by solid-solution strengthening. The optimized HEC reached a relative density of 98.3%, while the MoSi2-reinforced composite achieved 99.8% of theoretical density, exhibiting a hardness of 28.5 GPa and a fracture toughness of 5.2 MPa.m1/2. These findings demonstrate that MoSi2 addition provides an effective route to develop dense, homogeneous, and mechanically robust HEC-based composites.

Keywords

• High Entropy Ceramics (HECs)
• SiC
• MoSi2
• High energy ball milling
• SPS

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