Kazumi Kashiwagi

Tribochemical wear theory of non-oxide ceramics in high temperature and high-pressure water

Abstract The wear behavior of non-oxide ceramics in self-mated sliding in high-temperature and high-pressure water is controlled by the tribochemical reaction between ceramics and water at high temperature, when the frictional work appears as heat. This reaction kinetics is considered to follow a linear rate law, because the reaction products formed are easily removed during the contact and the tribochemical reaction proceeds on the interface between the fresh surface of the ceramics and the surrounding water. A theoretical equation for tribochemical wear of ceramics in high-temperature and high-pressure water is proposed on the basis of the interface reaction due to friction. The validity of the proposed equation is verified by using previous wear data for Si 3 N 4 and SiC. The bulk properties to improve the wear resistance for non-oxide ceramics are discussed.

Tribological Characteristics of Carbon Nano-Fiber Dispersed Silicon Nitride Based Composites in High-Temperature Fuel

The effect of carbon nano-fiber (CNF) dispersion on the tribological behavior of Si3N4 based composites against bearing steel were investigated in kerosene. The friction coefficients were not affected by the CNF addition. On the other hand, the wear rates of Si3N4/CNF composites showed a minimum value on 3 mass% CNF additions. The primary wear mechanism of Si3N4 is considered to be controlled by oxidation wear of Si3N4 due to a trace amount of water as impurity in the kerosene.