Thermal Shock Behavior of Nd-Doped α-Sialon Ceramics

Nd-alpha-sialons with the stoichiometric composition of Nd0.333Si10Al2ON15 were obtained by hot-press sintering at 1800 degrees C for 1h. The thermal shock behavior of the Nd-alpha-sialons was examined by a water-quenching technique. The influence of the thermal shock temperature difference (Delta T) and cycle times on the residual strength was evaluated. Equiaxed alpha-sialon grains formed together with a small amount of intergranular phase M' (Nd2Si3,AlxO3+xN4-x) and beta-sialon phase. The residual strength after a thermal shock tended to decrease gradually with increasing Delta T above 500 degrees C. However, the specimens exhibited an improved residual strength (similar to 94% of the room temperature strength) after a thermal shock of Delta T = 1100 degrees C. The residual strength presented a gradual decrease with increasing the thermal shock cycle times at Delta T = 1100 degrees C, and was still remained similar to 55% of the room temperature strength after 11-time cycle. It is contributed to the surface oxidation which may results in the healing of surface cracks and the generation of surface compressive stresses.