Structure, Phase Composition, and Defect Substructure of Differentially Quenched Rail

摘要

Differential quenching of rail by compressed air is a promising hardening method. Transmission electron microscopy is used for layer-by-layer analysis of differentially quenched rail. Quantitative parameters of the structure, phase composition, and dislocational substructure are determined and compared for different quenching conditions. Differential quenching of rail by compressed air in different conditions is accompanied by diffusional γ→α transformation. Three morphologically distinct components are formed: grains of plate pearlite, structure-free ferrite, and ferrite-carbide mixture. Gradient behavior is noted in the resulting structure: the state of the surface layer in the rail steel depends not only on the quenching conditions but also on the direction of observation and the depth of the layer being analyzed. Dislocational substructure is obtained; not only dislocational chaos, but also reticular, cellular, and fragmented dislocational substructure.