Microstructures and mechanical properties of surface and center of carburizing 23Cr2Ni2Si1Mo steel subjected to low-temperature austempering

A multiphase microstructure composed of nano-scaled bainite, martensite, undissolved spherical carbides and retained austenite was obtained on the top surface of carburizing 23Cr2Ni2Si1Mo steel after low-temperature austempered at 200 °C, with a dual-phase microstructure of fine martensite lath and carbon-enriched retained austenite in the center of steel. As compared with the conventional oil quenching and tempering (OQ) state, the low-temperature austempering specimens showed a higher surface residual compressive stress and a thicker residual compressive stress layer, and the wear resistance of the top surface of specimens austempered for 4 h, 8 h and 24 h was increased 40%, 58% and 12%, respectively. Moreover, the impact toughness of the center of these austempered specimens is also improved 20.8-33.3% as compared with that of the OQ specimen. Then, it can be deduced that applying the low-temperature austempering treatment for manufacturing carburizing-steel part is beneficial to improving its service performance for the better stress condition, higher wear resistance and higher interior toughness.