Microstructure and mechanical properties of hot pressed ZrB2-20SiC composite

In this study effort has been made to evaluate micro structural features and corresponding mechanical properties such as bulk hardness, micro hardness, flexural strength and fracture toughness of the ZrB2-20 vol% SiC composite before and after infra-red (IR) heating at 1400 and 1500 degrees C for 600 s. Volume fraction of the ZrB2-matrix phase and SiC reinforcing particulate phase of the composite remain same before and after IR heating. The surface of the composite after IR heating at 1400 degrees C appears to be covered by a thin outer tetragonal SiO2 layer, and a thin inner monoclinic ZrO2 layer. Flower like morphology of these oxides is also observed in the oxide scale. Some penetration of oxide product inside the surface defects is also seen. Similar oxide scale is observed for 1500 degrees C IR heated sample except the absence of flower like oxides morphology in this case. This marginal oxidation on the outer surface of the composite due to IR heating does not affect the mechanical properties of the composite. The mechanical properties such as, bulk hardness, micro hardness, flexural strength and fracture toughness of the composite do not get deteriorated after IR heating of the composite at 1400 and 1500 degrees C for 600 s rather it appears to improve slightly after IR heating possibly due to healing of the surface defects during IR heating.