On the Sintering of the Fe-Ni-C Ternary Mixed Powder Compacts

Abstract

Using mixed powder compacts of Fe-Ni-1.0 wt%C system with different Ni contents and Fe-4.0wt%Ni-C system with different graphite contents, the influence of Ni addition on the carburization and the dimensional changes were investigated by means of the differential dilatometric method and carbon analysis.The results obtained are summarised as follows:(1) Carbon content combined during heating process up to 900°C, which is about 0.1 wt% in a Fe-1.0 wt%C binary compact, increases with increasing Ni content in Fe-Ni-1.0 wt%C ternary compacts.(2) In the case of the ternary compacts which content carbonyl Ni powder, the sintering rate is remarkably promoted. Also the sintering promotive effect is observed in Fe-carbonyl Ni-1.0 wt%C compacts. These results suggest that the shrinkage due to the sintering of fine powders plays an important role in the promotion of sintering.(3) The combined carbon concentration of the Fe-1.0 wt%C binary sintered compact is nearly the same as that of eutectoid composition. However in Fe-Ni-1.0 wt%C ternary sintered compacts, some hypereutectoid regions are observed, because the carbon concentration lowers with increasing Ni content along the Fe-Ni-C ternary eutectoid line. Therefore the retained shrinkage increase remarkably by the contraction due to the precipitation of primary cementite in the Ni content more than 6 wt%Ni.