1989 Volume 38 Issue 429 Pages 668-674
In order to investigate the effect of hydrogen charging on the mechanical properties of 0.1%, 0.3% and 0.6% carbon steels with ferrite-pearlite and cementite-spheroidized structures, creep tests during cathodic polarization have been carried out. Cathodic polarization introduced hydrogen into the specimen, and produced hydrogen-induced cracks. Charging with hydrogen increased the creep rate. The creep rate changed in a complex manner, depending on the charging time, the structure and thickness of the specimen, the carbon content, and the external stress. During hydrogen charging, the application of external stress larger than a critical stress, which depended on the structure, carbon content and thickness of the specimen, caused creep fracture of the specimen. In general, the hydrogen-induced creep deformation and fracture process can be explained by the following three mechanisms; (i) Lüders deformation caused by the generation of hydrogen damage (crack and dislocation), (ii) the motion and multiplication of the dislocations caused by the internal stress due to hydrogen and the external stress, and (iii) the growth of cracks caused mainly by the application of external stress. The creep (i) is observed only in the case of the application of the stress just below the yield stress. In the case of small external stress, only the creep (ii) occurs.
