Effect of TiN addition on the microstructure and mechanical properties of TiB2-FeNi based cermets

The TiB2-x vol% TiN-20 vol% (Fe-Ni) system cermets with various volume fraction of TiN were successfully fabricated through gas pressure sintering. The effects of TiN content on the mechanical properties and microstructure of TiB2-based cermets was explored in detail. The microstructure and compositional analyses of TiB2-based cermets were investigated by SEM, EPMA, TEM, and X-ray diffraction. The results shown that only TiB2, TiN and Fe0.64Ni0.36 phases in the TiB2-based cermets, not any other brittle phases such as M2B, M23B6 could be found. The TiB2 grains formed a typical core-rim structure, but the TiN particles didn't. The dominant fracture mode of TiB2-based cermets transformed from intergranular fracture to transgranular fracture as the TiN content increasing from 0 to 25 vol%. Toughening mechanisms of TiB2-based cermets transformed from debonding, crack deflection to crack bridging and crack deflection as the TiN content increasing. The properties of TiB2-based cermets have been greatly enhanced as the TiN content varying from 0 to 25 vol%. The transversal rupture strength, indentation fracture toughness, Vickers hardness, and relative density of TiB2-20 vol% TiN-20 vol% (Fe-Ni) cermet reached up to 1191.12 +/- 40 MPa, 18.77 +/- 0.40 MPa m(1/2), 14.40 +/- 0.20 GPa, and 99.74 +/- 0.20%, respectively.