ND2O3-DOPED SIALONS WITH ZRO2 ZRN ADDITIONS FORMED BY SINTERING AND HOT ISOSTATIC PRESSING

beta-sialon and Nd2O3-doped alpha-sialon materials of varying composit ion were prepared by sintering at 1775 degrees and 1825 degrees C and by glass-encapsulated hot isostatic pressing at 1700 degrees C. Compos ites were also prepared by adding 2-20 wt% ZrO2 (3 mol% Nd2O3) or 2-20 wt% ZrN to the beta-sialon and alpha-sialon matrix, respectively. Neo dymium was found to be a fairly poor alpha-sialon stabilizer even with in the alpha-phase solid solution area, and addition of ZrN further in hibited the formation of the alpha-sialon phase. A decrease in Vickers hardness and an increase in toughness with increasing content of ZrO2 (Nd2O3) or ZrN were seen in both the HIPed beta-sialon/ZrO2(Nd2O3) com posites and the HIPed Nd2O3-stabilized alpha-sialons with ZrN addition s.