Tribological characterisation of silicon nitride/multilayer graphene nanocomposites produced by HIP and SPS technology

Tribological performance of monolithic silicon nitride (Si3N4) and Si3N4 based composite ceramics containing 1 wt% and 3 wt% multilayer graphene (MLG) sintered by conventional hot isostatic pressing (HIP) and spark plasma sintering (SPS) have been investigated by ball-on-disc tests in dry sliding conditions at two different sliding speeds (v=20 and 200 mm/s), using SiC and Si3N4 ball materials, as sliding counterparts to compare the wear behaviour of the differently produced ceramic materials. The wear performance was characterized by the specific wear rate (k), wear coefficient (K) and friction coefficient (μ), completing with the analysis of the wear track morphology and wear mechanisms. SPS composites showed improved wear behaviour that can be explained by the combined effect of SPS on the microstructure and mechanical properties resulting in modification of the controlling wear mechanism of the Si3N4/MLG composites.