Effects of V/Cr on the Nucleation and Transformation of Mo-containing Carbides on Fe Matrix in M50 Bearing Steel

The Mo-containing carbides in M50 bearing steel have an important effect on fatigue and wear resistance. It is significant to study the nucleation mechanism of Mo-rich carbides for controlling the type of carbides and improving the properties of steel. In this study, the α-Fe (100)/MoC (100) interface and the α-Fe (100)/Mo2C (100) interface with different structures are studied based on density functional theory. The results show that the interface with Fe–C covalent bond has the highest stability. The study of the electronic structure of the interface shows that the main component bonding of the interface is covalent and metallic, the electron orbital contribution consists mainly of the d orbitals of Fe and Mo atoms and the s and p orbitals of C atoms. In addition, the effects of V and Cr elements on the precipitation of Mo-rich carbides were studied. The results show that interface stability is improved with the increase of V element concentrations. With the addition of Cr atoms, the precipitation of Mo-rich carbides is inhibited. Under the effect of V element segregation, the spherical VC gradually nucleates at the Fe/Mo2C interface, and the large-size carbides are refined.