Effect of martensite pre-quenching on bainite transformation kinetics, martensite/bainite duplex microstructures, mechanical properties and retained austenite stability of GCr15 bearing steel

In this work, effect of martensite pre-quenching on the subsequent bainite transformation kinetics of GCr15 bearing steel has been investigated by means of dilatometry. The results show that the pre-quenched martensite is significantly accelerate nucleation of subse-quent bainite transformation in comparison with direct bainite austempering. Meanwhile, specimen of martensite pre-quenching at 200 degrees C has the shortest incubation period of bainite transformation at 240 degrees C. Moreover, the transformation rate of bainite trans-formation after martensite pre-quenching is faster than direct bainite austempering in the initial growth stage, and decrease with the decreasing of martensite pre-quenching tem-perature. Compared with the conventional quenched and tempered (QT) specimen, the tensile strength is slightly decrease from 2170 MPa to 2143 MPa, but the impact toughness is obviously increase from 43 J to 71 J in specimen heat-treated by martensite pre-quenching at 200 degrees C and subsequent bainite transformation at 240 degrees C. In addition, the mechanical stability of retained austenite in all martensite pre-quenching specimens are higher than that of QT specimen. (C) 2021 The Authors. Published by Elsevier B.V.

Automated summary

The effect of martensite pre-quenching on the bainite transformation kinetics of GCr15 bearing steel was investigated through dilatometry. The results showed that pre-quenched martensite accelerates the nucleation of subsequent bainite transformation and has advantages in transformation rate and mechanical properties compared to direct bainite austempering.