Influence of tantalum on the microstructure and properties of Ti(C,N)-Ni cermets

• (Ta,Ti)(C,N) cermets were made by mechanical alloying
• Ta is incorporated in the starting Ti(C,N) structure during sintering
• The addition of Ta results in grain refinement
• Improvements in hardness and fracture toughness are achieved
• The addition of Ta modifies the core-rim structure of the Ti(C,N)-Ni cermets

Several (Ti,Ta)(C,N) cermets were prepared from Ti(C,N) and Ta powder with or without Ni. For comparison, Ti(C,N) with Ni were also prepared. The mixed powders were sintered at 1400–1500 °C by FAST/SPS up to a density higher than 99% theoretical density. The addition of Ta delays densification of Ti(C,N)-Ni cermets due to the formation of intermetallic phases. During sintering, the Ta was incorporated into the Ti(C,N), forming solid solution, thus changing the core-rim structure of the Ti(C,N) cermets. On the other hand, the Ta additions result in grain refinement and improved hardness (from 16.1 GPa to 17.8 GPa) and fracture toughness (from 5.5 MPa.m1/2 to 6.9 MPa.m1/2).