Microstructure and properties of (Ti,W)(C,N)/(Ni,Mo) cermets after a heat-treatment at high nitrogen pressure

In order to decrease the heat-treatment time and avoid particle growth during the post-sintering heat-treatment, the interaction of nitrogen with (Ti,W)(C,N)/(Ni,Mo) cermets was investigated at high pressure. Sintered (Ti,W)(C,N)/(Ni,Mo) cermets with different starting formulations were heated at 1000 degrees C using nitrogen pressures up to 110 MPa. At this temperature and nitrogen pressure the nitriding time for the formation of interaction zones more than 20 mu m thick is decreased to 3 hours and no particle growth occurs. The heat-treatment leads to a dramatic improvement in surface hardness and a very small decline in transverse rupture strength of the (Ti,W)(C,N)/(Ni,Mo) cermets. The microhardness in the near-surface area shows a transition of the highest microhardness to a lower as the interior is approached.