Failure of Secondary Superheater Tube by Caustic Stress Corrosion Cracking (CSCC)

Abstract

Failure analysis of a ruptured superheater tube from a boiler has been carried out. Experiments revealed that the chemical composition of the tube was in correspondence to SA213-T22 standard and had ferrite-pearlite microstructure of 2.25Cr-1Mo steels. Investigations showed that caustic stress corrosion cracking (CSCC) was the predominant mechanism of cracking and failure of the tube. Misuse of boiler feed water, as the supplying water through the attemperator to the superheated steam, in the secondary superheater, and carryover from the steam drum to the superheater resulted in scale buildup and cracking of the CSCC type.