Chemical evolution of polycrystalline cementite (Fe3C) during single-pass sliding wear: An investigation by surface spectroscopy

Abstract

The development of wear-resistant steels requires an understanding of deformation behavior and chemical evolution in cementite (Fe3C) under tribological loading. Previous investigations of chemical changes in steels during wear provided limited knowledge of the cementite stability and its transformations as the single phase is conventionally embedded in a metal matrix. This study examines elemental and phase distributions in bulk polycrystalline cementite with minor fractions of graphite, iron, and wüstite after single-pass sliding wear. We employ energy-dispersive X-ray spectroscopy in scanning transmission electron microscope, Auger electron spectroscopy, and X-ray photoelectron spectroscopy to characterize cementite composition before and after wear. Our results demonstrate that severe plastic deformation via contact shear leads to the partial decomposition and mechanical mixing of the non-cementite inclusions into the cementite matrix and the partial elemental homogenization in the outermost deformed region. In addition, we relate the dissolution of the graphite, which is present in the initial microstructure, to the formation of the Hägg carbides (Fe5C2).