Atomic migration of carbon in hard turned layers of carburized bearing steel

Grain finement and non-equilibrium carbon segregation within grain boundaries alters the mechanical performance of hard turning layers in carburized bearing steel. An atom probe tomography (APT) study on the nanostructured hard turning layers reveals carbon migration to grain boundaries as a result of carbide decomposition during severe plastic deformation. In addition, samples exposed to different cutting speeds show that the carbon migration rate increases with the cutting speed. These two effects lead to an ultrafine carbon network structure resulting in increased hardness and thermal stability in the severely deformed surface layer. (C) 2016 CIRP.