Investigation of microstructure and mechanical strength of SiC/AlN composites processed under different sintering atmospheres

This work inspects the effect of different sintering atmospheres on the microstructure behavior and grains morphology of pressureless sintered SiC/AlN ceramic composites. Different SiC/AlN composites with different AlN content (0-40 wt%) were prepared by pressureless sintering at 2080 °C/2 h with addition of 2.5 wt% yttria and alumina as sintering aids. Microstructure investigation of the different carbide/nitride composites were studied under two different sintering atmospheres of argon (Ar)/vacuum and nitrogen (N2)/vaccum. Densification parameters of the different composites were measured and evaluated. Results showed that, SiC/AlN composites gave homogenous microstructure with expected high temperature properties. However they manifested different demeanors under the different atmospheres. Sintering of different composites in Ar/vacuum atmosphere was found the most suitable with high density and harmonic structure. Cold crushing strength (CCS) of the composites of the chosen atmosphere was studied and analyzed. Different SiC/AlN composites gave superior strength values resulted from the good bonding and diffusion between SiC and AlN besides their solid solution reaction. Results suggest using the investigated composites in aggressive high mechanical and high temperature applications.