Microstructure and performance of graded Ti(C, N)-based cermets modified by nitriding treatment during different sintering stages

The effects of nitrided treatment during different sintering stages on the microstructure and mechanical properties of Ti(C, N) based cermets were studied. The results showed that: compared with the sample sintered in vacuum, the surface microstructures of these samples which nitrogen gas was introduced in entire stage, heating stage and final sintering stage changed obviously, the porosity greatly increased, and the mechanical properties decreased dramatically. However, the sample which nitrogen gas was introduced at cooling stage had formed an about 10 μm graded surface layer enriched in hard phase and deficient in binder phase, the surface microhardness improved significantly from 14.33 to 18.11 GPa, and the transverse rupture strength (TRS) was basically unchanged.