BEHAVIOR OF HYDROGEN IN FE-NI-C ALLOYS

A particular cathodic charging technique was used to evaluate the beha viour of hydrogen on Fe-25.66Ni-0.31C alloy. This technique is based o n the electrolysis of water injected in a molten salts bath. The elect rolytic charging conditions were chosen as -2.05 V/Ag and 300 degrees C. The quantities of hydrogen extracted from specimens of different di ameters after electrolysis over different durations were used to calcu late both the substantial surface concentration (C-0=3 cm(3) H-2/cm(3) metal) and the hydrogen concentration profiles in austenite. After qu enching at - 65 degrees C, a linear relationship between the hydrogen concentration and the amount of retained austenite was determined. A c ritical concentration C-k = 0.06 cm(3) H-2/cm(3) metal, initiated micr ocracks in martensite. The behaviour of hydrogen on austenite is discu ssed in terms of grain boundary and dislocation trapping.