Sintering behaviour and mechanical properties of Cr_3C_2-NiCr cermets

摘要

Cr_3C_2-NiCr cermets are used as metal cutting tools due to their relatively high hardness and low sintering temperatures. In this study, a powder mixture consisting of 75 wt% Cr_3C_2-25 wt% NiCr was sintered at four different temperatures and characterized for its microstructure and mechanical properties. The highest relative density obtained was 97% when sintered at 1350℃. As the relative density increased, elastic modulus, transverse rupture strength, fracture toughness and hardness of the samples reached to a maximum of 314 GPa, 810 MPa, 10-4 MPa-m~(1/2) and 11.3 GPa, respectively. However, sintering at 1400℃ caused further grain growth and pore coalescence which resulted in decreasing density and degradation of all mechanical properties. Fracture surface investigation showed that the main failure mechanism was the intergranular fracture of ceramic phase accompanied by the ductile fracture of the metal phase which deformed plastically during crack propagation and enhanced the fracture toughness.