Obtaining ultrafine spheroidized carbides by combining warm deformation with divorced eutectoid transformation in GCr15 bearing steel

Abstract

In this work, the ultrafine spheroidized carbides were obtained by combining warm deformation with the divorced eutectoid transformation (DET) in GCr15 bearing steel. The results show that the temperature range of DET is approximately 730 °C to 700 °C at a cooling rate of 0.05 °C s−1. It is also found that excellent spheroidized microstructure can be obtained and less deformation resistance can be generated when the deformation is carried out at 720 °C with a strain rate of 0.5 s−1. This result could be ascribed to the fact that deformation provides the driving force for transformation, dynamic recrystallization (DRX) and reduced dislocation density through the coordination of warm deformation and DET. This suggests that the deformation at the initial temperature is more favorable to the spheroidization than that at the intermediate temperature of DET. In addition, it is also proved that the warm rolling forming in the actual production line can shorten the spheroidization time from at least 10 h to 2 h and obtain ultrafine spheroidized carbides with the roundness close to 1. This research may provide a novel pathway to obtain good spheroidization effect with less energy conservation.