Review of factors affecting condition assessment of nickel based transition joints

The high temperature performance of welds manufactured between ferritic low alloy steels and austenitic stainless steels is critical to power plant operation. The fabrication of these joints via established procedures using nickel based consumables should ensure adequate service life. However, low ductility failures as a consequence of creep cavitation at interfacial carbides have been reported in these welds within less than 10 years of operation. Accurate assessment of damage develop ment in plant welds is therefore required to prevent unplanned outages. Remaining life predictions can be made using post-exposure testing provided material is available. Non-destructive assessments are preferred and the potential exists for establishing techniques based on monitoring cavity density or strain accumulation.