Rapid consolidation of TiNCr ₂N(Ti,Cr)N nanoparticles using pulsed current activated sintering and the mechanical properties of sintered product

We previously reported that the electrical explosion of Cr-plated Ti wires in N2 gas produced nanoparticles composed of cube-shaped TiN, sphere-shaped Cr ₂N and extremely fine (Ti,Cr)N particles. In this study, the mixture powders were consolidated by pulsed current activated sintering (PCAS). A near-full density compact could be obtained within five minutes at 1600°C. The shrinkage-time profile revealed an abnormally high contraction of the compact at 1500°C after the typical sintering period observed at temperatures between 700 to 1300°C. The sudden shrinkage at 1500°C turned out to be the consequence of the eutectic melting of Cr2N particles which decomposed to Cr and N ₂. The metallic Cr phase was located mostly at triple points and grain boundaries prohibiting the grain growth of TiN grains. The microhardness of the compact (13.6 GPa) was lower than that of pure TiN compact (16.2 GPa) due to the soft Cr phase. Nevertheless, the fracture toughness of the compact (6.6 MPa·m _1/2) was higher than that of the pure TiN compact (6.0 MPa·m1/2) probably because the metallic Cr along grain boundary may deter the crack propagation.