Comparative Analysis of the Structure and Phase States and Defect Substructure of Bulk and Differentially Quenched Rails

Abstract

Optical and transmission electron microscopy (TEM) methods are used for layer by layer comparative analysis of low-temperature reliability rails with increased wear resistance and contact-fatigue strength of the highest quality after bulk quenching and differential hardening by different regimes. Quantitative relationships are established for changes in structural parameters, phase composition, and dislocation substructure over the central axis and fillet at different distances from the running surface. The degree of structure and phase composition inhomogeneity and defective substructure is revealed. It is shown that with respect to structural component content and interlamellar distance the structure after bulk hardening compared with differential hardening is more uniform in a layer 2 mm thick and less uniform at a distance of 10 mm from the running surface. With respect to stress concentration density, the rail structure after bulk hardening (compared with differential hardening) is less uniform in a layer 2 mm thick and more uniform in a layer at a distance of 10 mm from the running surface.