Acoustic Emission Characteristics of Hydrogen Charged Cr-Mo Steel During Deformation

Tensile test was conducted on 2.25Cr-1Mo steel specimens that were electrochemically hydrogen charged and acoustic emission signals were collected in the real-time stretching process. The results show that tensile strength of 2.25Cr-1Mo steel with hydrogen charging is 536.30MPa, decreased by approximately 57MPa and reduction of area is 43.62%, decreased by 7%, compared with the specimens without hydrogen charging. Hydrogen embrittlement-induced regions known as “fisheyes” and quasi-cleavage morphology are observed on the tensile fracture surface. The AE signals activity in the elastic stage of hydrogen charged 2.25Cr-1Mo steel is enhanced, but the acoustic emission signals activity in the yield stage is decreased. The cumulative absolute energy of AE signals of hydrogen charged specimens during deformation is almost one order magnitude lower than that without hydrogen charged specimens. The AE signals amplitude generated by the hydrogen charged specimens is about 0.33mV lower than that of the specimens without hydrogen charging during tensile deformation, and that the bandwidth of signal is reduced by 0.06MHz. Though the analysis of AE signals, it is found that tensile deformation microscopic mechanism of hydrogen charged specimens is that dislocation emission and motion is enhanced but dislocation cross-slip is inhibited by hydrogen.