Hydrogen attack of steel. Progress report, April 1, 1979-March 31, 1980

The objective of this work is to establish the atomic processes by which the hydrogen attack of pressure vessel steel occurs. The approach is to follow the growth kinetics using an exceptionally sensitive dilatometer and to compare these data with the predictions of models based on the postulated mechanisms. This is supplemented by scanning electron microscope (SEM) studies to establish the geometry and location of the growing methane bubbles. The steels used have been various commercial alloys because of our now confirmed suspicion that trace impurities, e.g., from dioxidation practice, play a central role in determining the nucleation and growth geometry of the bubbles or fissures