Influence of shot peening on surface residual stress and microstructure evolutions of R260 rail steel.

Abstract

In this study, shot peening (SP) was performed on R260 rail steel. The effects of SP treatment on surface properties such as surface topography, microstructure, residual stress, and microhardness were investigated using optical microscopy, X-ray diffraction, and microhardness measurements. Increasing both the peening intensity and surface coverage effectively produced a gradient structure in the surface layer of R260 rail steel, characterized by high compressive residual stress and significant work hardening. The enhancements in grain refinement, compressive residual stress, and work hardening achieved by increasing surface coverage were more pronounced than those obtained by simply raising the Almen intensity. Under the 24A-1000 shot peening condition, the steel exhibited a residual stress of approximately 1.24 GPa and a surface hardness of roughly 410 HV0.01.