Failure analysis of welded joints in a power plant exhaust flue

In this paper, a series of failures of the welded joints in a power plant exhaust flue have been investigated. On-site investigation and experimental evaluations revealed that knife-line attack, embrittlement of weld metal detected due to sigma phase formation and thermal fatigue are responsible for the failure. The flue is made of stabilized austenitic stainless steel (type 321) and works at 520–550 °C.