A novel quenching-electroshocking-tempering process for toughness improvement by microstructure refining and austenite stability tailoring in aviation bearing steel

Abstract

In this work, the microstructural evolution and mechanical properties of aviation M50 steel under a novel quenching-electroshocking-tempering (Q-E-T) process were investigated. Microstructural observations indicate that the carbon concentration and volume fraction of retained austenite (RA) in Q-E-T specimens are higher than those in conventional quenching‐tempering (Q‐T) specimens due to the significant carbon partition induced by the introduced electroshocking treatment (EST). Meanwhile, the diameter of packets in the Q-E-T specimens is refined from 1.71 μm to 1.34 μm, which is attributed to the segmentation of blocky as-quenched RA by bainite transformation during EST. The mechanical analysis shows that an excellent combination of ultimate tensile strength and impact toughness is achieved for M50 steel subjected to the Q-E-T process. Compared with the conventional Q-T process, the impact absorbing energy of M50 steel is increased by 24.1% without any loss of tensile strength. Additionally, the thermal and mechanical stabilities of RA in the Q-E-T specimens are both improved. This work provides a novel strategy for improving the impact toughness of M50 by refining the microstructure and appropriately tailoring the stability of RA via an efficient Q-E-T process.