The Effect of Addition of Mesocarbon Microbeads (MCMB) on the Microstructure, Mechanical Properties, and Friction Coefficient of MCMB-Cf/SiC Composites Prepared by Spark Plasma Sintering Method

Introduction and objective: The aim of this study is to investigate the effect of addition of mesophase carbon microbeads (MCMB) on the microstructure, mechanical properties, and friction coefficient of MCMB-Cf/SiC composites prepared by spark plasma sintering.Materials and methods: Silicon carbide nanocomposite powder reinforced with 20 wt. % carbon fibers and different percentages of MCMB was prepared. Disk-shaped samples were prepared using spark plasma sintering (SPS). The effect of addition of different percentages of MCMB on the density, friction coefficient, fracture toughness, flexural strength, and microhardness of the samples was investigated.Results: The results showed that by increasing the MCMB content from 0.1 to 1 wt. %, the density of the sintered samples decreased from 93.1% to 89.8% of the theoretical density due to the higher porosity of this sample. Also, the friction coefficient decreased from 0.54 to 0.48 with increasing MCMB content due to the higher graphite content in higher MCMB weight percent. The hardness of the sintered samples with silicon carbide nanoparticles matrix also increased from 1095 to 1510 Vickers due to the higher density and lower porosity of sample with decreasing MCMB content from 1 to 0.1 wt.%. The fracture toughness and flexural strength of MCMB-Cf/SiC samples increased from 3.47 to 5.96 MPa.m1/2 and 72.9 to 138.7 MPa, respectively.Conclusion: It was found that the MCMB-Cf/SiC sample containing 1 wt. % of MCMB has the closest properties to the properties of air brake discs. The densities of the SPS-sintered samples containing 1 wt. % of MCMB were obtained as 93.1% of theoretical density. The friction coefficient of these samples was obtained to be 0.48, which had the closest friction coefficient to that required for air brakes (0.4).