Fabrication of functionally graded Ti(C, N)-based cermets by double-glow plasma carburization

Functionally graded Ti(C, N)-based cermets were prepared via vacuum liquid sintering and subsequent double-glow plasma carburization. The microstructure was characterized using scanning electron microscope (SEM), electron probe microanalysis (EPMA) and X-ray diffraction (XRD). It was found that a surface zone enriched in titanium, molybdenum, tungsten, carbon and nitrogen, deficient in nickel was introduced by double-glow plasma carburization. The high carbon activity in the surface region drove titanium, molybdenum and tungsten elements inside the substrate to diffuse outwards, consequently the nickel-rich binder was forced to transport inwards. The formation of the binder-deficient layer was controlled by the diffusion of the alloy elements and the growing rate did not follow the parabolic law.