Grain Boundary Analysis of HT9 Steel after Accelerated Creep Testing

Abstract

AbstractFerritic/martensitic steels are attractive materials for use as components in nuclear reactors because of their high strength and good swelling resistance. Grain boundary specific phenomena (such as segregation, voiding, cracking, etc) are prevalent in these materials so grain boundary character is of primary importance. Certain types of boundaries are more susceptible to thermal creep damage whereas others tend to resist damage. If more damage resistant boundaries can be introduced into the structures, this will result in steel that is more resistant to the processes of degradation that prevail in high-temperature environments. We have characterized the grain boundary structure in HT9 steel by electron backscatter diffraction to identify boundaries that are resistant to degradation and those that are more susceptible to damage in extreme environments. It is found that intergranular damage is mitigated by a high fraction of low energy boundaries, and certain kinds of grain boundaries are more favored by intergranular cracks.