B<sub>4</sub>C–SiC Ceramics with Interfacial Nanorelief Morphologies and Low Underwater Friction and Wear
Wei Zhang, Xiaoyu Chen, Seiji Yamashita, Mitsuhiro Kubota, Hideki Kita
Abstract
The tribological properties of carbide ceramics (SiC, B4C–SiC, and B4C) sliding against SiC balls in water at a normal load of 20 N in ambient conditions were investigated. Compared with traditional SiC ceramics used as mechanical seal materials, B4C–SiC ceramics exhibit lower friction and wear under water lubrication. The lower coefficient of friction of B4C–SiC ceramics is caused by the nanorelief with a depth of 12 nm formed on their friction surfaces. The water stored in the valleys of nanorelief can provide continuous lubrication to the B4C–SiC ceramic friction surfaces, and the good load carrying capacity makes B4C–SiC ceramics exhibit lower COF under higher load (20 N). In situ formed nanorelief can show beneficial influence on the frictional property of materials under water lubrication. The formation of nanorelief on B4C–SiC ceramics is the result of competition between mechanical wear and tribochemical wear under water lubrication. B4C–SiC ceramics with better tribological properties are expected to replace traditional SiC ceramics as mechanical seal materials under water lubrication. A design idea that using the microhardness difference between the two phases of composite ceramics to in situ prepare relief on the composite ceramic surface to improve the frictional property under water lubrication has been proposed in this study.