Hydrogen Embrittlement of a Manganese–aluminum High-strength Bainitic Steel for Railway Crossings

Abstract

The hydrogen embrittlement characteristics of a Mn–Al bainitic steel for railway crossings were studied by means of the slow strain rate test (SSRT), the delayed fracture test and X-ray diffraction (XRD) analysis. The binding energies and hydrogen diffusion barriers of an iron unit cell were tested separately with Al, Si and H, and were evaluated by the first principle calculation. The results showed that the hydrogen embrittlement decreased greatly with increased Al content. Microstructure examinations indicated that the content of retained austenite increased with increased Al content, which was as irreversible hydrogen traps and was not sensitive to hydrogen embrittlement. It is found that the characteristics of hydrogen embrittlement identified by SSRT and the delayed fracture test were different. From the first principle calculation, the binding energy of the iron lattice containing aluminum decreased less as compared to those of the cell containing silicon, but the diffusion barriers increased significantly.