Fabrication technology of functionally graded Ti(C, N)-based cermets

Ti(C，N)-based cermets were prepared by vacuum liquid sintering and then heat-treated by double-glow plasma carburization. The microstructures，compositional distribution and phase constitution of the as-sintered and carburized cermets were analyzed by scanning electron microscope (SEM)，electron probe micro-analysis (EPMA) and X-ray diffraction (XRD) technology，respectively. It is found that a surface zone enriched in titanium，molybdenum，tungsten，carbon and nitrogen，deficient in nickel is introduced by the double-glow plasma carburization. The high carbon activity in the surface region drives titanium，molybdenum and tungsten elements inside the substrate to diffuse outwards，and consequently，the nickel-rich binder is forced to transport inwards. After carburization，the hard phase enriches in the surface zone while the binder enriches in the near surface area. The surface hardness of the cermet is enhanced by the heat-treatment，while its transverse rapture strength (TRS) is hardly changed.