Creep damage analysis of mod.9Cr-1Mo steel welds considering void mechanics modeling

Since creep strength reduction of mod.9Cr-1Mo steel welds in long-term was confirmed experimentally, residual life prediction for Type IV failure has been an important theme Ultra Super Critical (USC) plants after service. The mechanism within the fine-grained heat affected zone (FGHAZ) is twofold; increase number density voids a size comparable to FGHAZ grain (5 μm), and strain softening last stage life. In this paper, damage analysis scheme considering above two mechanisms applied welded joints with non-uniform weld metal materials, (HAZ) base metal, such as those found large uniaxial cross-weld specimens. A void mechanics model expresses (creep density) terms nucleation, which strongly influenced by multiaxial state stress. critical value corresponding initiation micro-crack determined based on results random-fracture-resistance boundaries authors paper. Both distribution process crack initiation, propagation final rupture predicted are compared experimental at 650 °C．