Abstract
Different types of compaction process were employed in studying the effect of the green state on the sintering of TiCTiNNiMo
2C and Ti(C
0.3N
0.7)NiMo
2C cermets. Specimens of 51 mm × 7 mm × 5 mm with and without 5 wt% polyethylene glycol (Carbowax) were uniaxially pressed at 150 MPa, some being subsequently compacted by cold isostatic pressing (CIP) at 350 MPa. Liquid-phase sintering was carried out in nitrogen atmosphere at temperatures of 1500 and 1530°C for 2 h. Solid-state sintering was performed also at 1450°C for comparison. It is shown that 1450°C is too low a temperature for effective sintering no matter what compaction method is used. The green-state porosity and the pore-size distributions, as sintered morphologies, and the microhardness and microstructural development were characterized. Mercury-porosimetry measurements indicate that with increasing compacting pressure, large pores are eliminated and the pore-size-distribution curves shift towards smaller pores. Higher compaction load also leads to a decrease in average pore size and a wider pore-size distribution. It was found that the Ti(C
0.3N
0.7)NiMo
2C cermets are superior to the TiCTiNNiMo
2C cermet, in that they possess better micro-hardness, higher bulk density and a lower porosity level. Cermets with Carbowax additives are sinter better than those without. In comparison of the different compaction processes, the two-stage consolidation (die-pressing + CIP) results in better sintering properties than does die-pressing alone.