Ti(C, N)-based cermets were treated using hot isostatic pressing (HIP) at 1423 K in nitrogen. The microstructures compared with the as-sintered cermets were investigated using X-ray diffraction, scanning electron microscopy, transmis- sion electron microscopy, energy-dispersive X-ray analysis, and electron microprobe analysis. It was found that high nitro- gen activity in the surface zone resulted in the formation of gradient structure. Approximately 20-μm-deep, nitrogen-rich and titanium-rich hard surface zone was introduced by the heat treatment. The nitrogen activity was the driving force that caused the transportation of the atoms through the binder, titanium towards the surface, and tungsten and molybdenum in- wards. In the surface zone, the particle size became fine, the inner rim disappeared, and the volume fraction of the outer rim and the binder phase considerably reduced. Small grains of TiN, WC, Mo2C, and nitrogen-rich carbonitride phases formed in the surface zone during the heat treatment, improving the tribological property of the heat-treated cermet.
LIU WenjunXIONG WeihaoZHENG YongSHI ZengminYE Jiajian
