Hydrogen Trapping in BCC Fe-Cr Alloys (7 ~ 9.4 Wt% Cr) as Studied by Microautoradiography—Contribution of Carbon-Hydrogen Interaction—Consequences on Hydrogen Cracking

Microautoradiography of tritium, observed at the electron microscope scale (SEM or TEM) was used to locate hydrogen trapped in the microstructure of Fe-Cr (50 ppm C) alloys, after cathodic charging. The morphology and behavior of the hydrogen traps depends on the thermal history of the specimens and is strongly related with carbon precipitation and segregation. Outgasing experiments were performed at room temperature and the trapping energy was estimated to 59 kJ/mole (14 kCal/mole) for grain boundaries containing carbon and to 67 kJ/mole (16 kCal/mole) for carbide precipitate interfaces. The consequences of high energy trapping on hydrogen induced cracking are discussed.