Wear engineering oxides/anti-wear oxides

The tribological behaviour of self-mated ceramic composites, like SiC-TiC, Si3N4-TiN and (Ti, Mo) (C, N) + Ni, were characterized under dry sliding friction. The coefficient of friction still remain unchanged on a level known from SiC and Si3N4 ceramics. The addition of titanium compounds to SiC and Si3N4 ceramics reduced the wear rate compared to titanium-free ceramics. Increasing sliding speed and temperature enhances this trend. The (Ti,Mo)(C,N) materials exhibited a wear behaviour nearly independent from sliding speed and temperature with wear rates lower than 10(-7) mm(3)/N m UP to 800 degrees C. The present study has by means of Small-Spot X-ray diffraction, Laser Raman Spectroscopy (LRS) and Transmission Electron Microscopy (TEM) demonstrated, that TiO2 and crystalline Magneii-phases of Ti(n)O2(n-1)-type with a crystallographic shear structure as well as some double oxides like NiTiO3, Mo0.975Ti0.0025O2 and beta-NiMoO4 were detected on different ceramic substrates formed by tribo-oxidation during tests at 400 degrees C and 800 degrees C. The conditions during tribological operation are sufficient to generate crystalline Magneli-type phases by tribo-oxidation, like gamma-Ti3O5, Ti5O9 and Ti9O17. (C) 1998 Elsevier Science S.A. All rights reserved.