Influence of microstructure on mechanical properties of molybdenum alloyed P/M steels

Different sintered alloyed steels were manufactured following conventional powder metallurgy route. Molybdenum prealloyed steel powders were used as raw material. Graphite and iron powders were added to obtain final compositions (two levels of carbon and four of molybdenum). Materials were uniaxially compacted at 700 MPa and sintered at three different temperatures (1150, 1200 and 1250 °C) in a 95% N2–5% H2 atmosphere. After sintering, mechanical properties were evaluated, and a broad microstructural study was carried out. Results show that molybdenum promotes a bainitic microstructure from sintering that could eliminate the possibility of quenching thermal treatment. High mechanical properties are obtained, and strengths of 600 MPa are obtained for 0.7% C–3.5% Mo steels.