Mechanical and tribological properties of high entropy carbide-based micro-nano ceramic composites

(NbTaTiWZr)C-based micro-nano composites were fabricated by spark plasma sintering employing multi-layer graphene (MLG), Ni, and Al2O3 as reinforcements. It is demonstrated that excellent mechanical properties were achieved for MLG, Ni, and Al2O3 hybrid addition with a hardness of 21.73 GPa, a flexural strength of 572.4 MPa, and a fracture toughness of 7.65 MPa m1/2. Enhanced densification together with inhibited grain growth contributed to the simultaneously improved hardness and flexural strength. The major toughening mechanisms were determined as microcracks, crack deflection, crack bridging, crack stopping, MLG wall, MLG pull-out, MLG bending, and MLG wrapping grains. Furthermore, outstanding tribological performance occurred to the (High entropy ceramic) HEC-Ni-Al2O3-MLG with a friction coefficient of 0.23 and wear rate of 4.32 x 10- 7mm3N- 1m- 1, as a function of graphene acting as a lubricating friction layer and the enhanced mechanical responses.