Effect of cBN@RGO Core–Shell structure on mechanical properties and microstructure of alumina-based ceramic tool materials

Despite their high hardness and wear resistance, the widespread application of alumina (Al 2 O 3 ) ceramics is limited by their inherent low fracture toughness. To address this challenge, a composite reinforcement strategy incorporating high-hardness cBN and high-strength graphene nano-platelets was employed. To address the issues of poor dispersion and weak interfacial compatibility associated with direct addition, a core–shell reinforcing phase comprising cubic boron nitride (cBN) coated with reduced graphene oxide (RGO), denoted as cBN@RGO, was synthesized via electrostatic self-assembly. Al 2 O 3 /cBN@RGO composites were then fabricated using spark plasma sintering at 1350 °C under a pressure of 35 MPa with a dwelling time of 8 min. Compared to the baseline Al 2 O 3 /cBN composite, the Al 2 O 3 /cBN@RGO composite exhibited simultaneous enhancements in hardness, flexural strength and fracture toughness by 9.5 % (to 19.5 GPa), 26.7 % (to 568 MPa) and 28.2 % (to 6.81 MPa m 1 / 2 ), respectively. Microstructural analysis revealed that the cBN@RGO core–shell particles were well dispersed in the Al 2 O 3 matrix without agglomeration, exhibiting strong interfacial bonding, which effectively inhibited the detrimental phase transformation of cBN to hBN at high temperatures. The results demonstrate that the cBN@RGO core–shell design achieves a synergistic reinforcement effect, providing a novel strategy for developing high-performance ceramic matrix composites.