Impurities segregation and two-dimensional phases formation on iron surface

Abstract

Surface segregation kinetics of impurities in ferritic steels with ultra-low carbon content in temperature range of 550-750^oС is studied with Auger-electronic spectroscopy and scanning electronic microscopy methods. At temperatures below 600^oС main impurity segregating is carbon displacing the sulfur atoms in surface. Above 700 ^oС sulfur and titanum dominate displacing phosphorus atoms in the surface. At 600-700^oС temperature range sulfur and phosphorus atoms competition is observed and surface composition is found to be different for various granules. Dissolution of titanium sulfides placed in subsurface layers of some granules increases segregation flow of sulfur and titanium atoms and decreases phosphorus segregation. The surface of granules free of sulfide releases is enriched with phosphorus.