Effect of different carbon sources on the sintering behaviour and mechanical properties of alloyed PM steels: From graphene to carbon black

Carbon is added to sintered steels with two main purposes: to reduce residual surface oxide during heating stage and further dissolve in the steel matrix for alloying purposes. The most desirable requirement to the carbon source is that it provides efficient oxide reduction before inter-particle necks starts to develop and so minimizes risk of the surface oxide enclosure, resulting in weak inter-particle necks and low mechanical properties. The present study summarizes the activity of different carbon sources, including different grades of graphene nano-platelets, number of natural and synthetic carbon sources and different grades of carbon black. Results from the study of sintering process, microstructure and fractography evaluation are correlated with mechanical properties. Obtained results indicate that structure, powder size and interatomic bond characteristics of the carbon source are the most important properties determining carbon reactivity