Deformation and phase transformation in polycrystalline cementite (Fe3_{3}C) during single- and multi-pass sliding wear

Cementite (Fe$_{3}$C) plays a major role in the tribological performance of rail and bearing steels. Nonetheless, the current understanding of its deformation behavior during wear is limited because it is conventionally embedded in a matrix. Here, we investigate the deformation and chemical evolution of bulk polycrystalline cementite during single-pass sliding at a contact pressure of 31 GPa and reciprocating multi-pass sliding at 3.3 GPa. The deformation behavior of cementite was studied by electron backscatter diffraction for slip trace analysis and transmission electron microscopy. Our results demonstrate activation of several deformation mechanisms below the contact surface: dislocation slip, shear band formation, fragmentation, grain boundary sliding, and grain rotation. During sliding wear, cementite ductility is enhanced due to the confined volume, shear/compression domination, and potentially frictional heating. The microstructural alterations during multi-pass wear increase the subsurface nanoindentation hardness by up to 2.7 GPa. In addition, we report Hägg carbide (Fe$_{5}$C$_{2}$) formation in the uppermost deformed regions after both sliding experiments. Based on the results of electron and X-ray diffraction, as well as atom probe tomography, we propose potential sources of excess carbon and mechanisms that promote the phase transformation

ОЦІНКА ДОВГО СТРОКОВОСТІ ЕКСПЛУАТУЮЧИХ СЯ ЕНЕРГОМАШИНОБУДІВЕЛЬНИХ КОНСТРУКЦІЙ НА ОСНОВІ РОЗРАХУНКУ НАПРУЖЕНО-ДЕФОРМОВАННОГО СТАНУ

There are the considered problems of longevity and durability of elements of power machinecreation in the article.Рассмотрены проблемы долговечности и прочности элементов энергетического машиностроения.Розглянуто проблеми довговічності і міцності елементів енергетичного машинобудування