Interaction of Hydrogen with the Microstructure of AH36 Steel

Abstract

In this research, internal friction testing, x-ray diffraction, and multiple microstructural observation techniques were used to investigate the interaction between hydrogen and the AH36 steel microstructure. The results showed that the microstructure of tested steel consisted of ferrite, lamellar pearlite, and a small amount of degraded pearlite. The number of dislocations in ferrite and pearlite increased after electrochemical hydrogen charging, and the ferrite grain boundaries broadened. As an increase in the hydrogen-charging current densities, the full width at half maximum of the diffraction peak on the (110) crystal plane stayed almost unaltered, while those on the (200) and (211) crystal plane widened and the total dislocation density was increasing. The P1 internal friction peak appeared after hydrogen charging, and the diffusion of interstitial hydrogen atoms generated the Snoek peak. The appearance of P2, P3, and P4 peaks was independent of hydrogen in the sample. The P2 peak was the Snoek peak generated by the diffusion of interstitial carbon atoms. The P3 peak was the Snoek–Kê–Köster generated by the interaction between hydrocarbon Cottrell atmosphere and dislocations. The P4 was the relaxation peak of grain boundaries. With increased hydrogen-charging current densities, the activation energy of the P1, P3, and P4 peaks decreased gradually, while the P2 peak remained essentially constant.