Comparative study of fabrication of Si3N4/SiC composites by spark plasma sintering and hot isostatic pressing

A Si3N4/SiC composite with additions of La2O3, Y2O3 and SiO2 was fabricated by spark plasma sintering (SPS). The porosity and phase formation resulting by this method are compared with those obtained by sinter/hot isostatic pressing (sinter/HIPing). The open porosity was completely eliminated by SPS in 10min of heating to 1900 degrees C and 5min dwell time. The complete alpha to beta transformation was achieved with the formation of elongated beta Si3N4 grains. The same result was achieved by sinter/HIPing at 1750 degrees C with a dwell time of 160min. There were differences in the % beta transformation from a, open porosity and the presence of minor phases between the two processes. The comparison of SPS with sinter/HIP showed the former to be a rapid fabrication process for Si3N4 which warrants further investigation to optimise the microstructure. (C) 1998 Published by Elsevier Science Limited.