In situ Ti(C,N)-based cermets by reactive hot pressing: Reaction process, densification behavior and mechanical properties

In situ Ti(C,N)-TiB 2 -Co cermets were produced by reactive hot-pressing from a Co-Ti-C-BN system. The reaction process and densification behavior were investigated through the comparative researches on the phase transition sequence, microstructure evolution pattern and shrinkage rate of powder compacts during sintering process. The results show that Ti(C,N) is synthesized via the dissolution of C into TiN unit cell, while TiB 2 is formed through the combination of B and TiB as well as the reaction of Ti and B atoms in liquid. The viscose flow and dissolution-precipitation mechanisms are responsible for the densification in the reaction stage, while the plastic flow method contribute to the elimination of closed micropores in the solid state sintering stage. An external pressure can promote the densification, and Ti(C,N)-based cermet sintered at 34 MPa pressure exhibits the maximum relative density and mechanical properties.