Atomistic investigation of the mechanical and tribological responses of the ferrite-cementite interface with a Bagaryatskii orientation

The excellent tribological properties of pearlitic steel can be tracked to the synergistic effect between ferrite and cementite phases. However, owing to the lack of full understanding of the plastic carrier-interface interaction mechanism, the essential role of the interface in the mechanical and tribological response is indistinct. In this study, the deformation response of cementite/ferrite (Fe₃C/α-Fe) interface under a mechanical load was explored by leveraging molecular dynamics simulation. The results showed that the Fe₃C/α-Fe interface significantly hinders the shear deformation propagation and can effectively relax the strain/stress concentration. With the increasing indentation depth, the cementite phase undergoes an amorphous transformation and rejuvenation, and the ferrite phase undergoes a phase transformation to HCP, thus synergistically enhancing the plasticity of pearlite. On this basis, we revealed the underlying origin for the decreased growth rate of friction coefficient with the increasing friction depth. In particular, the tribological properties change periodically in the scratch direction due to the effect of interfacial dislocations, and the friction mechanism is also affected by the interfacial dislocation structure, showing a dendritic shear banding deformation. Our work is a step forward in understanding the relationship between the Fe₃C/α-Fe interface and the micro-mechanism of friction.