CYCLIC FATIGUE BEHAVIOR OF SILICON-NITRIDE MATERIALS

The cyclic fatigue behaviour of two silicon nitride materials have bee n 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 synthes is (SHS), and the other by a commercial route. Materials have been ful ly 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-ten sion cyclic fatigue, and under tensile static fatigue. Crack growth wa s measured with a travelling microscope focused on the specimen surfac e. Crack growth parameters were obtained assuming a Paris power law de pendence. The results obtained from these analyses and the study of fr acture surfaces on both materials have been correlated to the fatigue mechanism. (C) 1997 Elsevier Science Limited.