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 fabri cated by spark plasma sintering (SPS). The porosity and phase formatio n resulting by this method are compared with those obtained by sinter/ hot isostatic pressing (sinter/HIPing). The open porosity was complete ly eliminated by SPS in 10min of heating to 1900 degrees C and 5min dw ell time. The complete alpha to beta transformation was achieved with the formation of elongated beta Si3N4 grains. The same result was achi eved by sinter/HIPing at 1750 degrees C with a dwell time of 160min. T here were differences in the % beta transformation from a, open porosi ty and the presence of minor phases between the two processes. The com parison of SPS with sinter/HIP showed the former to be a rapid fabrica tion process for Si3N4 which warrants further investigation to optimis e the microstructure. (C) 1998 Published by Elsevier Science Limited.