Laser-induced breakdown spectroscopy (LIBS) allows for a time and spatially resolved almost non-destructive in situ measurement of hydrogen in metals [1]. A surface pretreatment is not necessarily needed. We measured quantitatively hydrogen in steel samples, which were charged either electrochemically or by high-pressure hydrogen gas and compared the results. Further, the feasibility of quantitative hydrogen line scan measurements was demonstrated by measuring hydrogen at water jet cut surfaces. The hydrogen concentrations measured with the help of LIBS were compared with CGHE measurements. It was observed that hydrogen can be reliably measured with LIBS for concentrations larger than 2 wt.-ppm. The results show that LIBS is a promising technique for time- and spatially resolved measurements of hydrogen in steel and steel weldments [2]. Results of time-dependant hydrogen permeation experiments will also be presented.

Figure 1. LIBS measurements (black squares) across the cut steel sample. The line is a guide-to-the-eye. Towards the sample surfaces to the left and to the right, a hydrogen concentration gradient can be seen due to the electrochemical charging in an electrolyte and the subsequent volume diffusion in the bulk.

References

[1] R.D., Smith; G.P., Landis; I., Maroff; D.L., Olson; T.R., Wildeman; Welding Journal, 2001, 80, 115-121.

[2] L., Quackatz; A., Griesche; T., Kannengiesser Welding in the World, 2024, 68, 915-923.