Controlling cobalt capping in sintering process of cermets

Liquid Phase Migration in Cemented Carbides – Experiments and Modelling

“…With regard to the formation of the Co-rich layer, the heat treatment cycle is the most important difference between experiments n this work and previous studies where cemented carbides went through a standard sintering cycle [40,41]. In this work, the samples were in the liquid state for a short time and quenched after heat treatment.…”

“…6) was observed. Co-capping results in the formation of a thin cobalt layer on top of cemented carbides [40].…”

Synthesis Studies of Radiation Dense Reactive Sintered Borides (Rsb) Nuclear Shielding Materials

“…3b and in Table 5 shows that the equilibrium liquid volume at the onset of the liquid phase at 1259 • C is 19.8% compared to 10.7% for cWC (Table 4), implying that densification would be well underway at T = 1300 • C. However, the liquid phase is much more complex in RSB55 than in cWC8A and that the actual liquid volume present would be significantly less than the equilibrium volume. It is probable that the liquid present in RSB55 at T > 1259 • C under sintering conditions either has a significantly lower volume than predicted from CAPHAD or is poor at wetting other solid components and therefore does not have a significant capillary force to densify the RSB55 body at T < 1350 • C. For cWCs, Co is excellent at wetting WC during liquid phase sintering [31] and this helps to densify the cWC body. The 1400 o C vacuum sintered sample (Fig.…”

Development of manufacturing technology on WC–Co hardmetals

“…Cobalt capping was a term that refers to local thin layers of cobalt which were occasionally observed on the surface of sintered WC-Co parts when they came out of the furnace. Cobalt capping, which is usually believed undesirable and needs to be removed, was also considered to be related to the carbon atmosphere in the sintering furnace during cooling [76][77][78][79][80].…”