MICROANALYSIS OF SIC-SI3N4 CERAMICS MADE BY HOT ISOSTATIC PRESSING

SEM (Scanning Electron Microscopy) and micro-FEB (Proton Elastic Backs cattering) were used to study a composite ceramic (Si3N4/SiC) layer ge nerated on the surface of SiC by exposing SIC to an N-2 atmosphere at high temperatures (1850, 1950 and 2000 degrees C) for different times of 0.5, 1, and 2 h, respectively. The thickness of the layers and the concentration of Si3N4 in the layers have been determined and correlat ed with the material properties, such as bending strength and fracture toughness, before and after the nitridation process. A remarkable imp rovement of the properties has been found to be related to the Si3N4 c oncentration in the nitridation layer, A model of N-2 diffusion in SiC under HIP (Hot Isostatic Pressing) is discussed.