Thermal shock and thermal fatigue resistance of Sialon–Si3N4 graded composite ceramic materials

Abstract

Sialon–Si3N4 graded composite ceramic materials were fabricated by hot press sintering. The mechanical properties and microstructure of the composites were examined. The thermal shock and thermal fatigue resistance of the Sialon–Si3N4 graded composite ceramic materials were investigated by means of the water quenching method. The microstructure of the composites was characterized with transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The results showed that the graded ceramic exhibited higher retained flexural strength under all thermal shock temperature differences compared to the homogeneous reference one, indicating the higher thermal shock resistance of the graded ceramic. The highest critical temperature difference of the graded composites was 600°C. The crack growth (∆c) of graded ceramic materials was much lower than that of homogeneous ceramic materials, which revealed the higher thermal fatigue resistance of the graded ceramics. The improvement of the thermal shock and thermal fatigue resistance was attributed to the formation of compressive residual stress in the surface layer and the enhanced mechanical properties induced by the graded compositional structure.