Effects of graphite additive contents and processing parameters on the mechanical properties of sintered and case-hardened compacts made of molybdenum hybrid-alloyed steel powder

Effects of graphite additive contents and processing parameters on the mechanical properties of sintered and case-hardened compacts made of molybdenum hybrid-alloyed steel powder have been investigated. High tensile strength and impact value were obtained in the conditions of the medium internal carbon content, higher sintering temperature, lower carbon potential or shorter carburizing time. The mechanical properties are deteriorated due to increasing hard martensite phases with high carbon content. It is believed that the reduction of these mechanical properties are mainly caused by increasing of brittle fracture by an internal notch effect of the pores, because the hard martensite phase have a high notch sensitivity.