Microtomographic investigation of damage in E911 steel after long term creep

Damage distribution in a notched hollow cylinder made of E911 steel and crept for 26,000 h at 575 °C under multi-axial stress state is assessed. Based on high-resolution tomographic reconstructions the size, shape and spatial distribution of voids along the notch radius have been characterized. The spatial distribution of void density shows strong correlation with stress triaxiality, maximum principal stress and the equivalent von Mises stress. The analysis of the size distribution of non-coalesced voids in terms of general power-law functions describing nucleation and growth indicates that void growth in E911 steel is dominated by the constrained diffusion mechanism.