Experimental analysis of design, development, mechanical and tribological properties of spark plasma sintered advanced WC-Al₂O₃ composites reinforced by graphene platelets

Alumina-based tungsten carbide composites reinforced by different weight percentages of graphene platelets (GPLs) were successfully sintered by latest spark plasma sintering (SPS) technique. The WC-Al₂O₃-GPLs composites were fabricated to design advanced tool materials to acquire an optimum set of mechanical, thermal and anti-wear properties for high-temperature cutting tool applications. This study has the novelty that such composites have not been developed using SPS. The addition of GPLs to composites enhanced the microstructure, however the optimum mechanical and thermal properties were exhibited with the composite having lesser addition of GPLs. At higher levels of GPLs addition, the microstructures and properties of composites were degraded on account of stacking/agglomeration of GPLs. It was observed that SPS delivered better densification and microstructures as compared to other conventional sintering. The mechanical properties were best revealed by the sample with 0.6 wt. % of GPLs with hardness of 20.71 GPa and fracture toughness of 11.84 MPa.m^1/2. The improved toughening and strengthening results of WC-Al₂O₃-GPLs composites were essentially acquired by inhibiting grain growth during sintering, bridging of GPLs between matrix components, and improved dispersion of composite constituents (EPMA/WDS), particle hardening and phase toughening (Al₂O₃, GPLs). A thermal study was conducted to investigate the thermal stability of sintered composites at higher temperatures while providing the maximum thermal conductivity and thermal diffusivity of 166 Wm⁻¹K⁻¹ and 0.276 × 10⁻⁴ m²s⁻¹ at room temperatures. The tribological testing revealed that the composites with lesser GPLs reinforcement attributed lower coefficients of friction, better surface finish and least wear of the materials.