Mechanical and tribological properties of porous metallic CBN composites reinforced by graphene nanoparticles

Porous metallic cubic boron nitride (CBN) composites with 50 vol.% porosity were prepared by using water soluble spherical carbamide particles as pore-forming agents. Graphene nanoparticles were employed in porous metallic CBN composites via a conventional vacuum sintering technique to strengthen the mechanical property of as-sintered samples. In order to investigate the influence of graphene nanoparticles on the strengthening mechanism and microstructure of porous metallic composites, various graphene concentrations (0, 0.005, 0.01, 0.05, 0.05, and 0.1 wt.%) were incorporated. Characterization of morphology characteristics, such as macropores, micropores, and interfaces between CBN abrasive grains and metallic matrix, were carried out. Results show that addition of graphene nanoparticles up to 0.01 wt.% improves the flexural strength of the as-sintered composites. Micropores within as-sintered samples rapidly increase with graphene nanoparticles concentrations and severely affect the mechanical strength of metallic composites. And then samples containing a higher graphene nanoparticles concentration have larger cracks around CBN abrasive grains. In addition, the grain fracture modes ranging from the trans-granular fracture to inter-granular fracture are observed as graphene nanoparticle concentrations increase. The mass fraction of graphene concentrations is optimized as 0.01 wt.% in terms of the friction coefficient, wear morphology, and microstructure.