2019 Volume 59 Issue 10 Pages 1901-1907
Hydrogen distribution in an electrolytically hydrogen-charged duplex stainless steel (DSS) was investigated by means of hydrogen microprint technique (HMPT), and quantitative analysis was made in terms of the sites where hydrogen atoms were desorbed. The results obtained were discussed with respect to the trapping site and diffusion path. The DSS (JISSUS329J4L) specimens with phase volume fraction of about 50:50 were examined as a function of hydrogen-charging and keeping time. The HMPT was performed on the charged side of the 1.5 and 24 h charged specimens with two keeping times in the ambient air for 0.5 (unkept) and 300 h. In the unkept specimen, hydrogen atoms (silver particles) were mostly detected on the interphase boundary at the shortest charging time, while they were also in the ferrite matrix for the longer charging time. The relative fraction of hydrogen atoms on the boundary against ferrite matrix was increased by increasing keeping time both in the cases of 1.5 and 24 h charging. Thus, the phase boundary was regarded as the preferential stable site for hydrogen in the DSS. Observation on the distribution of hydrogen in the cross section (middle thickness) of the unkept specimen for the charging time of 24 h revealed that relative ratio of silver particles inside the ferrite phase against the phase boundary was larger than that on the surface. This confirmed that some of the charged hydrogen atoms diffuse toward the other side, leaving the interphase boundary into the ferrite matrix because gamma phase is isolated.
