Fabrication of Bulk Chromium Nitrides Using Self-Propagating High-Temperature Synthesis and Hot Isostatic Pressing

摘要

Cr_2N, CrN and their mixtures with desired fractions were prepared by self-propagating high-temperature synthesis (SHS) under controlled nitrogen pressure and then followed by hot isostatic pressing at 1300 deg C and 196 MPa under argon gas. The combustion temperature increased with increasing nitrogen pressure. Single-phase Cr_2N and CrN were formed at 1040 deg under 0.18 MPa N_2 and 1730 deg C under 2 MPa N_2, respectively. The mechanical properties of chromium nitride ceramics with relative density of 99.2 percent were examined; Vickers hardness H_v (CrN: 11.2 GPa and Cr_2N: 14.5 GPa) linearly increased with increasing fraction of Cr_2N, whereas fracture toughness K_(IC) (approx 4.7 MPa· m~(1/2)) and bending strength sigma_b (approx 355 MPa) were constant regardless of the fraction of Cr_2N/CrN.