Determination of rail steel structural elements via the method of atomic force microscopy

The distance between pearlite plates is an important parameter for control of ductility and deformation strength-ening of carbon steels. Most methods of optical end electronic microscopy for measuring the distances between cementite and pearlite plates in pearlite steels make definite complications when applying to high-dispersed micro-structures. At present time rail steels with pearlite structure are fabricated with interlamellar distance 60-130 nm. This research used atomic force microscopy (AFM) for measuring interlamellar distances of pearlite structure in the heat-affected zone (HAZ) of rail welded joint. Qualitative evaluation of cementite and ferrite plates thickness was obtained for the first time, depending on location relating to a rail weld fusion line. The input of cementite plates in strength on the base of Hall-Petch equation was considered. Influence of the relationship between the size of pearlite colonies d p and thickness of cementite plates t c on metal destruction stress of a HAZ welded joint was assessed.