Effect of hydrogen on the ductility reduction of F82H martensitic steel after different heat treatments

The influence of heat treatment on hydrogen embrittlement (HE) susceptibility of F82H martensitic steel, a candidate material for the first wall and blanket of the DEMO reactor, was investigated by means of low strain rate tests conducted at room temperature on notched cylindrical specimens, pre-charged with hydrogen. Three types of thermal treatment were compared, which produced quite different material hardness and strengths. As a general rule, F82H steel exhibited a strong susceptibility to HE in all conditions, with transitions between ductile and brittle behaviour ranging from 0.5 to 1.0 wppm H. The comparison of results produced by the different heat treatments confirmed for F82H also the tendency toward an increase of the susceptibility with material hardness. Moreover, the examined steel appeared to be more sensible to HE than another martensitic steel (MANET II), which was also proposed as a candidate material for fusion reactor first wall application.