Development of α-SiAlON-SiC ceramic composites by liquid phase sintering

In this work, “in situ” α-SiAlON-SiC ceramic composites were obtained by liquid phase sintering, using SiC as reinforcement. Different β-SiC powder contents (0–20 wt.%), were added to Si3N4–AlN–RE2O3 powder mixtures, and compacted by cold isostatic pressing. The samples were sintered at 1950 °C for 1 h, in N2 atmosphere. Sintered samples were characterized by relative density, weight loss, X-ray diffraction and scanning electron microscopy. Furthermore, mechanical properties such as hardness and fracture toughness were determined by Vickers indentation method. Lattice parameters of the α′ phase did not considerably change with increase of SiC content. However, morphology, average grain size and aspect ratio of the α′ phase were considerably changed with increase of the SiC content. These behavior influences significantly the mechanical properties of this hard ceramic composite.