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

ABSTRACT

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°C and Alloy-617/10%Cr-steel welds at 575°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°C, the same cannot be concluded for Alloy-617/10%Cr-steel DMWs at 575°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.

KEYWORDS:

• DMW
• creep-rupture
• creep-fatigue
• damage characterisation

Disclosure statement

No potential conflict of interest was reported by the author(s).