High temperature damage development in Ni-alloy/steel dissimilar metal welds

The development of high-temperature damage in Ni-alloy/steel dissimilar metal welds and its influence on creep-rupture (CR) times and creep-fatigue (CF) endurances is examined. The importance of a systematic and detailed post-test examination of the damage generated in x-weld microstructures is emphasised, and available evidence for Alloy-617/1%Cr-steel welds at 550 degrees C and Alloy-617/10%Cr-steel welds at 575 degrees C is characterised. CR and CF weld strength factors for the two DMWs are determined by the respective kinetics of microstructural developments adjacent to the fusion line and in the FG/ICHAZ of the steel. While the influence of near-weld microstructural evolution in the steel part of Alloy-617/1%Cr-steel DMWs is similar for both CR and CF damage development at 550 degrees C, the same cannot be concluded for Alloy-617/10%Cr-steel DMWs at 575 degrees C. Creep-fatigue damage in Alloy-617/10%Cr-steel DMWs initially develops in the over-tempered parent material with an increasing influence of FG/ICHAZ CF damage generation with reduced strain range.

Automated summary

This study focuses on the examination of high-temperature damage in Ni-alloy/steel dissimilar metal welds and its impact on creep-rupture times and creep-fatigue endurances. The research emphasizes the importance of systematic and detailed post-test examination of the damage in x-weld microstructures, and characterizes available evidence for Alloy-617/1%Cr-steel welds at 550 degrees C and Alloy-617/10%Cr-steel welds at 575 degrees C. The study also determines CR and CF weld strength factors for the two DMWs based on the respective kinetics of microstructural developments adjacent to the fusion line and in the FG/ICHAZ of the steel.