Influence of Quenching-Partitioning-Tempering (QPT) process on microstructure and mechanical properties of Ce-microalloyed low alloy steels

Quenching-Partitioning-Tempering (QPT) treatment was applied to cerium (Ce)-microalloyed low alloy steels to explore the influence of QPT process parameters on the microstructure and mechanical properties. The QPT heat treatment helps achieve a wide-range of mechanical properties tailoring of the low alloy steels. Results revealed that for the steel A with 0.005 Ce, the optimal QPT process was found to be austenizing at 830 °C, with quenching at 280 °C, and partitioning at 400 °C for 30 minutes, yielding superior mechanical properties with an ultimate tensile strength of 1131 MPa, yield strength of 888 MPa, and elongation of 13.7%. Similarly, for the steel B with 0.017 Ce, the optimal QPT process was austenizing at 800 °C, with quenching at 250 °C, and tempering at 400 °C for 30 minutes, with an ultimate tensile strength of 1045 MPa, yield strength of 820 MPa, and elongation of 14.2%. The exceptional mechanical performance was attributed to the synergistic effect of tempered martensite, sufficient retained austenite, and fine carbides. The addition of Ce contributes to grain refinement by pinning while the Ce-containing precipitates exhibit a more favorable size and morphology. These findings contribute to the understanding and optimization of the QPT process for Ce-containing high-strength low alloy steels, enhancing their applicability in various industrial sectors.