THE EFFECT OF TIN AND TIC DISPERSOIDS ON THE HIGH-TEMPERATURE DEFORMATION MECHANISMS OF SI3N4

The compression creep properties of pressureless sintered Si3N4 matrix, Si4N4-(TiN + TiC) and Si3N4-TiN composites, and of a hot pressed Si3N4-TiC composite were studied in air between 1260 and 1340-degrees-C. Creep characteristics have been compared in relation to microstructure. The addition of soft TiC particles resulted in better mechanical strength, particularly in the creep ductility. The deformation of Si3N4-TiC, dominated by a more refractory vitreous phase, was slower than for the other composites. Further, based on a comparison of creep parameters obtained experimentally in this work and on the nature of dispersoids, deformation mechanisms are proposed.