Cyclic fatigue behaviour of silicon nitride materials

The cyclic fatigue behaviour of two silicon nitride materials have been investigated. Both ceramics were prepared under the same processing conditions from two different types of silicon nitride powders. One of the powders was obtained by self-propagation high temperature synthesis (SHS), and the other by a commercial route. Materials have been fully characterized using conventional techniques of XRD and SEM. Fatigue tests on double cantilever beam-type specimens, at a frequency of 10 Hz and a load rate of R = 0.125, have been performed under tension-tension cyclic fatigue, and under tensile static fatigue. Crack growth was measured with a travelling microscope focused on the specimen surface. Crack growth parameters were obtained assuming a Paris power law dependence. The results obtained from these analyses and the study of fracture surfaces on both materials have been correlated to the fatigue mechanism. (C) 1997 Elsevier Science Limited.