The effect of electropulsing-assisted ultrasonic nanocrystal surface modification on the microstructure and properties of 300M steel.

In this study, electropulsing-assisted ultrasonic nanocrystal surface modification (EP-UNSM) was used to process 300M steel. It has been demonstrated that pulsed current can more effectively improve the plasticity of 300M steel as compared to continuous current having the same effective current density, even though the bulk temperature (around 150 °C) and thus the thermal effect is the same. It is believed that a pulsed current, which has a much higher peak current density, can more effectively activate pinned dislocations and can better assist the deformation-based surface modification process. EP-UNSM treatment of the steel resulted in much higher surface hardness and greater plastically affected depth as compared to both UNSM and continuous current-assisted UNSM (CC-UNSM). As a result, EP-UNSM treatment imparted much higher wear resistance to the steel than either UNSM or CC-UNSM treatment. It has been demonstrated that pulsed current can effectively improve the process effectiveness of the selected deformation-based surface engineering process (UNSM) without significantly increasing the temperature. Unlabelled Image • EP-UNSM resulted in much higher surface hardness and thicker hardened layer compared with UNSM and CC-UNSM. • Pulsed current can more effectively improve the plasticity of 300M steel compared with continuous current. • Pulsed current can improve the process efficiency of UNSM without a significant temperature increase. [ABSTRACT FROM AUTHOR]