Characterization of functionally gradient Ti(C, N)-based cermets fabricated by vacuum liquid phase sintering and nitriding treatment during cooling

• Graded Ti(C,N)-based cermets were prepared by a simple one-cycle procedure.
• A 200 μm deep surface zone enriched in hard carbonitride grains was introduced.
• The hardness of the surface was significantly increased.

Functionally graded Ti(C,N)-based cermets were prepared by a simple and economic procedure which combined vacuum liquid phase sintering with nitriding treatment during cooling in one cycle. The prepared cermets were investigated using scanning electron microscope (SEM), energy dispersive X-ray analysis (EDX) and electron probe microanalysis (EPMA). It was found that the high nitrogen activity in the surface region drove titanium to transport outwards and accordingly forced nickel to diffuse inwards. As a result, a hard graded layer from the surface region down to about 200 μm depth enriched in carbonitride grains and depleted in binder phase was introduced, which improved significantly the hardness of the graded cermets.