Enhanced toughness of bearing steel by combining prior cold deformation with martensite pre-quenching and bainite transformation

This work reasonably utilizes the decreasing of martensite start (Ms) temperature caused by prior cold deformation, combining martensite pre-quenching and bainite transformation to develop ultrafine martensite-bainite duplex microstructures for improves toughness of GCr15 bearing steel. Comparison with the conventional quenched and tempered (QT) specimen, the remarkable improvement of impact toughness (∼87 J) and fracture toughness (∼39 MPa·m1/2) were achieved in 30% prior cold deformed specimen, while with a slight decrease in the hardness. The enhanced toughness was attributed to the nanometric martensite-bainite duplex microstructures and the formation of film-like retained austenite.