Synergistic Mechanical and Tribological Optimization of High-Entropy (TiVCrMoW)B Ceramics

To address the inherent brittleness and insufficient wear resistance of conventional transition metal monoboride ceramics, as well as the application limitations caused by large interfacial mismatches triggered by adding heterogeneous secondary phases, we prepared (TiVCrMoW)B homology and isostructural high-entropy monoboride ceramics containing compositionally enriched isostructural microregions using spark plasma sintering. This ceramic inherits the orthorhombic Cmcm-type monoboride crystal structure. XRD analysis indicates a single phase within its detection limit, while EDS characterization reveals significant elemental segregation, forming in situ compositionally enriched isostructural microregions that are Ti-, Mo-, and W-rich. The interfaces between these regions are well bonded, and the relative density reaches 94.13%. Relying on this intrinsic microstructural architecture, the material is observed to concurrently improve hardness and toughness under the present testing conditions, achieving a Vickers hardness of 39.95 ± 4.32 GPa under a 0.5 N load and a fracture toughness of 3.39 ± 0.36 MPa·m1/2. Under 10 N reciprocating dry friction conditions, it exhibits stable friction behavior, with a steady-state coefficient of friction maintained at 0.52 and a volume wear rate as low as (1.11 ± 0.4) ×10−6 mm3/(N·m). The wear mechanisms are primarily early-stage abrasive wear, microcrack propagation, and localized layered spalling, with no adhesive wear or brittle fracture observed. The low wear rate arises from the combined effects of lattice distortion induced by high entropy, isostructural compositional-microregion toughening caused by elemental segregation, and fine-grain-induced retardation of microcrack propagation. This work confirms that a homology isostructural compositional-microregion structure architecture can contribute to the concurrent enhancement of hardness, toughness, and wear resistance of high-entropy monoboride ceramics, and provides a promising design strategy for wear-resistant ceramics without external secondary phases based on the high-entropy strategy.