The Evolution of Deformation-Induced Carbides during Divorced Eutectoid Transformation in GCr15 Steels

A series of rolling experiments were carried out using GCr15 steel to investigate the effect of initial microstructure on the spheroidizing process, and especially the effect of deformation-induced carbides (DIC) on the divorced eutectoid transformation (DET). The results indicated that the existence of DIC was beneficial to the spheroidizing process, the optimal initial microstructure for DET was lamellar pearlite, and DIC precipitated at grain boundaries. The average thickness of the cementite lamella and the size of DIC decreased with a decrease in rolling temperature in the critical temperature region. When the specimen was rolled at 1053 K, a small amount of DIC of size similar to 1 mu m precipitated at grain boundaries. In contrast, the amount of DIC was increased when the rolling temperature was decreased to 1023 K, whereas the size of DIC was reduced to similar to 0.5 mu m. Interrupted quenching experiments indicated that DIC (M7C3) were transformed to M3C during the process of partial austenitization, and the evolution of spheroidization was influenced by the variation in the initial microstructure. For the specimens rolled at 1023 K, only similar to 60 min was needed to achieve the dissolution of DIC, which was the minimum, and the total time needed to achieve spheroidization was reduced to similar to 90 min.