EFFECTS OF SINTERING CONDITIONS ON MICROSTRUCTURE AND MECHANICAL PROPERTIES OF REACTIVE HOT PRESSED TIB₂-SIC CERAMIC COMPOSITES

Reactive hot pressing (RHP) offers many advantages over the conventional hot pressing process. In this work, TiB 2 -20 wt. % SiC ultra-high temperature ceramic composites were fabricated via RHP. The effects of sintering time (1600 -1700C) and sintering temperature (30 -60 min), as well as the relationship between microstructure and mechanical properties, were investigated. For the investigated range of sintering conditions, the optimum comprehensive mechanical properties, i.e., flexural strength of 725 MPa, fracture toughness of 6.5 MPam and hardness of 21.6 GPa, were achieved at 1700C for 45 min. The good mechanical properties were attributed to small grain size and homogeneous microstructure. The sintering time and temperature had significant influences on the mechanical properties and microstructure of the composites. The flexural strength and hardness increased when the sintering time prolonged from 30 min to 45 min, subsequently decreased with further increasing of time. The fracture toughness had the opposite trend. With increasing of the sintering temperature, both flexural strength and hardness increased. The high porosity resulted from the low temperature was responsible for the poor mechanical properties. Moderate sintering time and a higher sintering temperature would lead to higher mechanical properties.