Simultaneous Enhancement of Strength and Toughness in a Medium-Carbon Martensitic Steel by Ti-Mo Addition

A 1700 MPa grade medium-carbon Ti-Mo martensitic steel was produced by thermo-mechanical control process (TMCP) and quenching–tempering (Q-T) process. Microstructural and precipitation analyses were performed to characterize the refined microstructure and (Ti, Mo)C particles. Unlike other high-strength steels, the impact toughness of the 1700 MPa grade Ti-Mo-bearing martensitic steel was improved as well (42 J at −40 °C), which is close to the levels of maraging steel and secondary hardening steel with higher alloy contents. The quenching and tempering treatment refined prior austenite grains and facilitated the formation of nanoscale (Ti, Mo)C particles. Precipitation strengthening and grain refinement strengthening contributed to the improvement in strength and toughness.