Tribological properties of silicon carbide under water-lubricated sliding

The friction and wear performances of three kinds of self-mated silicon carbide (SiC), reaction sintered SiC, pressureless sintered SiC and toughened SiC, were investigated with a block-on-ring arrangement under water-lubricated sliding. Furthermore, the morphologies, phases and element valences of the worn surface were observed, examined and analysed employing scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectrometer and Fourier transform infrared spectroscopy respectively. In addition, the effects of microstructure and mechanical properties of the ceramics on their tribological properties were also discussed. It was found that the three kinds of SiC obviously showed different tribological properties. Higher friction coefficient and wear coefficient occurred for reaction sintered SiC and pressureless sintered SiC. The wear mechanisms of them were explained in term of pull-outs of grains and grain fracture. However, excellent tribological property, friction coefficient of 0.01, which suggested the characterization of hydrodynamic lubrication and wear coefficient of 4.2 X 10(-7) mm(3) N-1 m(-1), was obtained for toughened SiC. This resulted from that tribochemical oxidation took place and a ultraflat surface was formed on the worn track as a result that the toughened SiC possessed higher fracture toughness. (C) 1998 Elsevier Science S.A. All rights reserved.