Failure Analysis of Thermal Network Compensator in High-temperature Caustic Environment

A steam pipe compensator of thermal network consists of Incoloy825 alloy (inner layer) and 316L stainless steel (outer layer). The crest of bellows of the compensator cracked during the start of boiler after a abnormal stop. A comprehensive research on the failed reason of the compensator was carried out by metallography, SEM and EDS, etc. The results showed that caustic stress corrosion cracking occurred at the crest of bellows of the compensator, in which the tensile stress was the largest.