TRIBOLOGICAL PROPERTIES OF SILICON-CARBIDE UNDER WATER-LUBRICATED SLIDING

The friction and wear performances of three kinds of self-mated silico n carbide (SiC), reaction sintered SiC, pressureless sintered SiC and toughened SiC, were investigated with a block-on-ring arrangement unde r water-lubricated sliding. Furthermore, the morphologies, phases and element valences of the worn surface were observed, examined and analy sed employing scanning electron microscopy, X-ray diffraction, X-ray p hotoelectron spectrometer and Fourier transform infrared spectroscopy respectively. In addition, the effects of microstructure and mechanica l properties of the ceramics on their tribological properties were als o discussed. It was found that the three kinds of SiC obviously showed different tribological properties. Higher friction coefficient and we ar coefficient occurred for reaction sintered SiC and pressureless sin tered SiC. The wear mechanisms of them were explained in term of pull- outs of grains and grain fracture. However, excellent tribological pro perty, friction coefficient of 0.01, which suggested the characterizat ion of hydrodynamic lubrication and wear coefficient of 4.2 X 10(-7) m m(3) N-1 m(-1), was obtained for toughened SiC. This resulted from tha t tribochemical oxidation took place and a ultraflat surface was forme d on the worn track as a result that the toughened SiC possessed highe r fracture toughness. (C) 1998 Elsevier Science S.A. All rights reserv ed.