Effect of δ-ferrite on the H-trapping behavior in the martensitic stainless steel

δ-ferrite usually plays an important role in the mechanical properties of martensitic stainless steel. However, there are few studies on the effect of δ-ferrite on hydrogen embrittlement (HE) in martensitic steel. In this study, the H-trapping of δ-ferrite and the effect on the HE in martensitic stainless steel is investigated. The hydrogen distribution characteristics were observed by atomic force microscope scanning (AFM), and the related results show that the δ-ferrite, martensite and δ-ferrite/matrix (F/M) interface can act as hydrogen traps. The martensite and F/M interface has the higher hydrogen-trapping capability, hydrogen diffuses in δ-ferrite is faster than that of martensite. During deformation, Electron Back Scatter Diffraction (EBSD) observation shown that the exist of δ-ferrite can release the stress concentration caused by the poor deformation ability of martensitic grains, and further improve the resistance of HE. The results provide valuable insights into the behavior of δ-ferrite in the HE.