LAUSR

Abstract Effects of HfC addition on microstructures and mechanical properties of TiC 0.7 N 0.3 -based and TiC 0.5 N 0.5 -based ceramic tool materials were investigated. The results showed that the same by-products such as HfN 0.4 , HfNi, Ti 0.76 Hf 0.24 Ni, TiNi 0.85 Co 0.15 and HfCo 6 were discovered in these ceramics. To some extent, HfC additive can inhibit their denitrification in the sintering process. The HfC particles can produce the crack flection and a suitable HfC content can improve mechanical properties of these ceramics effectively. Besides, the TiC 0.5 N 0.5 -HfC ceramics exhibited a poor sinterability compared to TiC 0.7 N 0.3 -HfC ceramics, showing much more pores in fracture and polished surfaces micrographs; grains in TiC 0.7 N 0.3 -HfC ceramics are finer than that in TiC 0.5 N 0.5 -HfC ceramics; the HfC particles dispersion in TiC 0.7 N 0.3 -HfC ceramics is more uniform than that in TiC 0.5 N 0.5 -HfC ceramics; thus, the mechanical properties of TiC 0.7 N 0.3 -HfC ceramics are superior to that of TiC 0.5 N 0.5 -HfC ceramics. In addition, their fracture mechanism is a combination of transgranular fracture and intergranular fracture. As a consequence, the enhancement of their mechanical properties is conducive to the presence of intermetallic compounds, the fine microstructure and the suitable HfC content.