Effects of Graphite Content and Temperature on Microstructure and Mechanical Properties of Iron-Based Powder Metallurgy Parts

An experimental investigation was conducted to study the effects of graphite content and temperature on the microstructure and mechanical properties of iron-based powder metallurgy parts. The specimens were produced at two sintering temperatures, 600 °C and 1100 °C, respectively, and the graphite contents were 0.5%, 1%, 1.5% and 2%, respectively. The polished and etched specimens were examined by optical metallography (OM) and scanning electron microscopy (SEM). Brinell hardness of the sintered specimen was measured to evaluate the mechanical behavior, and the density and the porosity of the specimens were calculated to evaluate the compaction and sintering. The results show that: (1) as the graphite content increasing from 0.5% to 2%, the microstructure of the iron-based powder sintered specimen changes gradually from ferrite and a small amount of pearlite to pearlite and a small amount of ferrite, (2) with the sintering temperature increasing, the microstructure of the sintered interface becomes uniform, (3) with the graphite content increasing, the hardness of the iron-based powder sintered part grows obviously and (4) the densities of the specimens with different graphite contents at 1100 °C are higher than those at 600 °C, and with graphite content increasing, the porosity of the sintered specimen decreases.