Comparative study of carbon black and graphite powder as carbon source for PM compacts

Graphite powder is the most widely used source of carbon in making powder metallurgy components. In this study, the graphite powder was replaced by the nanoscale carbon black powder. Compared to graphite powder, the carbon black powder provides more uniform distribution, higher apparent density, and faster flow rate for the Fe-0.8% C powder mixture. After sintering, the homogenisation of carbon, microstructure, and hardness are all similar between the two carbon powders. But a higher amount of spring back during ejection and thus lower green density was attained by using carbon black powders. Nonetheless, the compacts using carbon black powder had higher amounts of shrinkage, which compensated for the spring back effect during sintering, thus giving the same density as the graphite powder.