Study on interface modification and tribological properties of MCMB-SiC self-lubricating composites

Mesocarbon microbead-silicon carbide (MCMB-SiC) composites are promising candidates for mechanical seals of nuclear reactor main pumps due to their adaptability to severe environments. However, the weak bonding strength between MCMB and SiC matrix causes an unstable dry friction coefficient, which limits its further development. Herein, the interface-modified MCMB-SiC composites were prepared by hot-pressing sintering using liquid vinyl hydrido polycarbosilane (VHPCS) coated raw material powder for the first time. The pyrolytic VHPCS was loaded on the surface of MCMB particles. The effects of VHPCS content on the microstructure, mechanical properties, and dry tribological properties of MCMB-SiC composites were systematically studied. The results show that the MCMB-SiC composites with 1 wt% VHPCS (MS-P1) had good comprehensive mechanical properties. Meanwhile, compared to MCMB-SiC composites without VHPCS (MS-P0), MS-P1 exhibited improved dry friction properties, with a dry friction coefficient (mu) reduced by -25% (0.18) and a wear rate (WR) reduced by -35% (7.69 x10-7 mm3 center dot N- 1 center dot m- 1). It was considered to be due to the nano-SiC grains generated by VHPCS after sintering improved the interface strength between MCMB and SiC matrix, which inhibited the detachment of hard SiC particles during the friction process. In addition, sufficient C-Si-O lubricating film can fill the pits, which acts as a self-healing effect. This study provides an effective route to improve the tribological properties of MCMB-SiC self-lubricating composites with high carbon content.