Visualization of Hydrogen in Stress and Strain Fields Using SIMS

Abstract

In order to clarify the mechanism of hydrogen embrittlement in high strength steel, it is necessary to evaluate local hydrogen concentration in stress and strain fields where hydrogen embrittlement is considered to occur. There are several ways to visualize hydrogen, but SIMS is advantageous in that it can detect hydrogen directly without reaction. In this study, visualization of hydrogen accumulated in stress and strain field was tried using SIMS. Hydrogen flux intensity in the bent portion of the U-bend specimen, where the stress gradient exists, changed according to the stress gradient, and the hydrogen flux intensity was higher on the outside of the bending than on the inside, with the center of the plate thickness at the boundary. On the shearing surface with strain field, the hydrogen flux intensity had a positive correlation with the stress. On the other hand, it remained constant with respect to the strain. From these observations, the hydrogen partitioning behavior in steel could be visualized semi-quantitatively by using the isotope labeling method with SIMS.

Appearance of the U-bend specimen (d = 10.0 mm) and hydrogen flux intensity (²D⁻/⁷²FeO⁻ image).