By using electron microscopic tritium autoradiography and tritium release measurements, the hydrogen behavior in heat-treated Cr-Mo steels was analyzed.
The optimum experimental conditions for autoradiography were first determined including the tritium charging of the sample, selection of nuclear emulsions, protective films of the sample surface, sub-zero temperature exposure and development.
The autoradiographic observations by thin foil transmission electron microscopy, replica electron microscopy and electron microprobe analyser revealed that, prior austenite grain boundary, martensite-lath interfaces, precipitate-matrix interfaces and MnS inclusion-matrix were the trap sites for hydrogen in these steels. Tritium release measurement enabled us to separate quantitatively mobile and trapped hydrogen in these steels.
