Hydrogen Embrittlement Susceptibility of Corrosion-Resistant Spring Rod Used in High-Speed Railway

Abstract

The corrosion of spring steel is very important for vehicle safety. In this work, we conducted an experiment on multi-element micro-alloy composition design; the corrosion resistance of a 60Si2Mn spring was improved by adding Cr, Ni, Cu and other corrosion-resistant elements, and the corrosion resistance index (I) was increased from 3.21 to 8.62. Hydrogen embrittlement resistance was studied using a hydrogen permeation experiment and a slow strain rate tensile experiment. For this study, the following steps were performed: Firstly, the material composition was designed, and the experimental materials that met the experimental design were prepared according to the corresponding deformation and heat treatment process; secondly, the experimental materials were charged with hydrogen; and finally, conventional tensile testing, slow tensile testing and fracture morphology testing were carried out. A hydrogen permeation experiment was carried out for the materials. The result showed that, with the increase of hydrogen charging time, the hydrogen content of two steel samples increased, and the plasticity indexes such as elongation and reduction of the area appeared in three different stages which rapidly decreased, slowly declined, and then tended to balance. The uniform NbC nano precipitated phase can double the number of irreversible hydrogen traps (Nir) per unit volume, and decreased the effective hydrogen diffusion coefficient (Deff) from 1.135 × 10−10 to 6.036 × 10−11. It limited the free diffusion of hydrogen and made the immersed hydrogen harmless, thus improving the hydrogen embrittlement resistance of corrosion-resistant spring steel 60Si2Mn.