Modelling of a Grade 91 power plant pressurised header weldment under ultra super-critical creep conditions

This paper is concerned with the creep-damage modelling of a Grade 91 pressurised header, which was observed to undergo in-service cracking in weldments. A multi-axial creep damage model Kachanov type, single state variable, has been implemented into finite element analysis study responses weldments and sub-zones i.e. base metal (BM), weld (WM) heat-affected zone (HAZ). Material properties for each constituent were obtained from results accelerated tests on materials extracted header. Predictions crack initiation made sections stub header welds. also used estimate failure life weldment under ultra-super-critical conditions. Further, growth behaviour predicted based time-dependent critical growth. The distributions mode cross-weld test specimens good agreement reported experimental observations. correlate reasonably well industrial